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The geology of Hawkesbury Island, Skeena mining division, British Columbia Money, Peter Lawrence 1959

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THE  GEOLOGY  OF HAWKESBURY  ISLAND  SKEENA MINING D I V I S I O N , B R I T I S H  COLUMBIA  by  PETER B.Sc,  A  LAWRENCE  McGill  MONEY  University,  1956  thesis submitted i n p a r t i a l f u l f i l m e n t of the requirements f o r the degree o f MASTER in  OF  SCIENCE  t h e Department of GEOLOGY  We to  THE  UNIVERSITY  accept t h i s t h e s i s as the required standard  OF B R I T I S H  April,  1959  COLUMBIA  conforming  ABSTRACT  British  Hawkesbury  Island  Columbia.  I t i s u n d e r l a i n by  lamprophyre part  dykes  of the E c s t a l l The  limestone,  other  rock  ally  have  septum  of  rocks.  rocks.  few  metamorphism  bands  Shear zones and  These  The  of  quartzite,  rocks  have  These minerals  of the  a r e common been  and  formed  They  and  amphibolite  Small the  by  gener-  staurolite-quartz  throughout  formed  and  schist  subfacies of the almandine  have  form  crystall-  been  are strongly s e r i c i t i z e d .  chlorite  latter  amphibolites  of the r e g i o n a l type.  indicative  of  pendant.  are mainly  are present.  assemblages  sericite  A  Division  I n t r u s i o n s , younger  kyanite-staurolite-almandine mica  kyanite-muscovite-quartz facies.  or r o o f  rocks  gneisses.  types  dynamothermal  Coast  o l d e r metamorphic  metamorphic  quartz-feldspar ine  and  i s i n the Skeena Mining  percentages  metamorphic  during retrogressive  metamorphism. Apart these  rocks  consisting arkosic  were  few  a thick  of tuffaceous  igneous  eugeosynclinal  s e d i m e n t s and  bodies,  sequence  semi-pelitic  or  sediments.  periods  metamorphic  the f o l i a t i o n  to  70°  north 20°  rocks  of deformation,  However,  north  s m a l l metamorphosed  originally  mainly  The two  from a  west  east  has  so  have that  a general  i n the northern  to north  55°  probably  east  their trend  part  undergone  at  least  s t r u c t u r e i s complex. of north  o f the septum  i n the southern  50° and  part.  west of  The positions zation  by  Coast  intrusion.  in situ.  occurred  but  have  little  had  metamorphic  Intrusions They  have have  Some a s s i m i l a t i o n  this  i s a marginal  affect  rocks.  on  reached  their  not been  present  formed  of the country  feature.  The  by rock  Coast  the grade o f metamorphism  granitihas  Intrusions of  the  In the  presenting  requirements  this for  of  British  it  freely available  agree for  that  Department  for  or  copying  gain  shall  by or  not  his  and  study.  I  extensive be  copying  granted  representatives.  allowed  of  this  without  tig?  my  by  of  the  It  thesis  is  make  further this  Head  of  thesis my  understood  for  written  of  University  reference  may  .  the  shall  of  CL^iJ  at  Library  The U n i v e r s i t y of B r i t i s i Vancouver Canada. Date  degree  fulfilment  the  publication be  partial  that  for  purposes  in  advanced  I agree  permission  that  Department  an  Columbia,  scholarly  thesis  financial  permission.  TABLE  OF  CONTENTS  Chapter I.  II.  Introduction P r e l i m i n a r y Statement F i e l d Methods L o c a t i o n and A c c e s s Topography and G l a c i a t i o n Drainage Climate Flora Fauna General Previous  III.  Page  .  12  Geology Geological  1 1 1 2 4 7 8 9 10  12  Work  General Geology The Metamorphic Rocks Introduction Petrology of the Plagioclase Amphibolites . . (1) P l a g i o c l a s e - h o r n b l e n d e - b i o t i t e rocks . (2) Plagioclase-hornblende-biotite-epidote rocks (3) Plagioclase-hornblende-diopside amphibolites (4) P l a g i o c l a s e - s t a u r o l i t e amphibolites . . Petrology of the Metasediments (1) Plagioclase-quartz-biotite-hornblende gneiss (2) Plagioclase-K feldspar-quartz gneiss .  . . . .  13 20 20 20 22 32  . .  . .  34 37 44 44 47  (3) Kyanite-staurolite-almandine mica schist . 57 (4) Sillimanite-quartz-plagioclase gneiss . . . 68 (5) Graphitic quartz-plagioclase schist . . . . 70 (6) Quartzite 75 (7) Quartz-tremolite-zoisite rocks 75 (8) C r y s t a l l i n e limestone 79 (9) Sericite-epidote schist 81 (10) A l b i t i z e d a n d p o t a s h - e n r i c h e d rocks . . . . 83 P e t r o l o g y o f t h e Meta-igneous Rocks 87 (1) Meta-iegneous amphibolites 87 (2) Acid pegmatites 92 O r i g i n o f t h e Metamorphic Rocks 92 The Grade o f Metamorphism 104 (1) Metamorphic F a c i e s 104 (2) Temperature-Pressure Conditions I l l The C a u s e s o f M e t a m o r p h i s m 114 IV.  The Igneous Rocks Petrology o f the Coast Intrusions O r i g i n and Nature o f t h e Coast I n t r u s i o n s Other Intrusions (1) Carbonatized A n d e s i t i c (?) Rocks (2) Lamprophyre Dykes  . . . .  118 118 128 129 129 133  Chapter V.  VI.  Pa%e 137  S t r u c t u r a l Geology General Structure of the Northern Part of the Coast Mountains Major Structural Features of the Map Area . . . Small-scale Structures (1) In the metamorphic rocks (2) In the igneous rocks  137 138 149 149 151  Conclusions  153  Bibliography  156  LIST OF ILLUSTRATIONS Figure  Page  1. 2.  Index map of Western B r i t i s h Columbia 3 ACF diagram showing the range i n composition of the plagioclase-hornblende-biotite rocks . . 23 3 . Photomicrograph of plagioclase-hornblende amphibolite 40 4 . Photomicrograph of plagioclase-hornblendeepidote rock 40 5. Photomicrograph of plagioclase-hornblendeepidote rock 41 6. Photomicrograph of plagioclase-biotite-epidote rock 41 7. Photomicrograph of plagioclase-biotite-epidoterock 42 8 . Photomicrograph of plagioclase-diopside-hornblende amphibolite 42 9. - 1 0 . Photomicrographs of p l a g i o c l a s e - s t a u r o l i t e amphibolite 43 11.-12. 13.-14.  Photomicrographs of plagioclase-K feldsparquartz gneiss . . .  55  Photomicrographs of plagioclase-K feldsparquartz gneiss 56 15. ACF diagram showing the range i n composition of the kyanite-staurolite-almandine mica schists 59 16. - 1 7 . Photomicrographs of kyanite-staurolitealmandine mica schist 64 18.-19. Photomicrographs of kyanite-staurolitealmandine mica schist 65 2 0 v - 2 1 . Photomicrographs of kyanite-staurolitealmandine mica schist 66 2 2 . - 2 3 . Photomicrographs of k y a n i t e - s t a u r o l i t e almandine mica schist . 67 2 4 . - 2 5 . Photomicrographs of s i l l i m a n i t e - q u a r t z pla&ioclase gneiss 69 2 6 . - 2 7 . Photomicrographs of graphitic--quart z-: . plagioclase schist . 73 2 8 . - 2 9 . Photomicrographs of graphitic quartzplagioclase schist 74 30. Photomicrograph of quartz i t e 78 31. Photomicrograph of quartz-tremolite-zoisite rock 78 32. Photomicrograph of c r y s t a l l i n e limestone . . . 80 33. Photomicrograph of sericite-epidote schist . . 83 34. Photomicrograph of a l b i t i z e d rock 86 35. - 3 6 . Photomicrographs of meta-igneous amphibolite . 91 37. ACF diagram showing the compositional ranges of three: rock units 93  Figure  38.-39. 40. 41. 4 2 . -43.  44.-45. 46. 47. 48. 49. 50. 51. 52.  53.  Page Photomicrographs of quartz d i o r i t e Photomicrograph of monzonite Photomicrograph of granodiorite Photomicrograph o f (?) a n d e s i t i c rock Photomicrograph of lamprophyre . Poles of F o l i a t i o n of the Metamorphic Rocks o f Hawkesbury I s l a n d Intersection of the Planes of F o l i a t i o n the Metamorphic Rocks i n A r e a I I n t e r s e c t i o n of the Planes of F o l i a t i o n the Metamorphic Rocks i n A r e a I I I n t e r s e c t i o n of the Planes of F o l i a t i o n the Metamorphic Rocks i n A r e a I I I Intersection of the Planes of F o l i a t i o n t h e M e t a m o r p h i c Rocks i n A r e a IV I n t e r s e c t i o n of the Planes of F o l i a t i o n the Metamorphic Rocks i n A r e a V The A z i m u t h and P l u n g e o f Drag F o l d s i n the Metamorphic Rocks Map  of the Geology  1 54.  Map  inch  =  1  o f Hawkesbury  inch  =  127 127 132  135 141 of 142 of 143 of 144 of 145 of  o f Hawkesbury  1 mile  146 147  Island,  adft-  mile  of the Structure 1  126  Island,  pooke fc~7{Ym? j  f ^> i n poeteefr ^  ACKNOWLEDGMENT  The Company field  thin by  and i t s o f f i c e r s  work  thesis  of  carried  sections.  D r . W.  W.A.  t o thank  f o rt h e i r  the Ecstall  Mining  permission  t o use  kind  o u t f o r t h e company  Assistance  H. W h i t e ,  Padgham  as a b a s i s  tification  The w r i t e r  i s also who  indebted  carried  M r . K . R o y a n d M r . W.  collected  of the thesis  a n d D r . G.V. R o s s i s  during  the field  to  out part  Philips,  a s s i s t a n t s , a n d t o M r . R. G r e g g s  of fossils  for this  photographs and  the preparation  a n d Mr. C.C. S h e n g ,  mapping,  as f i e l d  during  D r . K.C.McTaggart  acknowledged.  the field  served  like  a n d f o r t h e u s e o f company maps, a e r i a l  gratefully Mr.  w r i t e r would  who  ably  f o r idenwork.  CHAPTER  I  INTRODUCTION  PRELIMINARY  STATEMENT  This the  thesis  o f 1958  summer  Mining  Company,  during  the winter  account  and  and  FIELD  METHODS  to  traverses  a number  feet  ridge  employed  by  during  the  laboratory  work  1958-59.  I t s object  i s t o present  o f Hawkesbury  Island,  o f the metamorphic  over  Ecstall  c a r r i e d out  with  an  particular  rocks  of the  Intrusions  of  to  these  l i m i t e d work  and,to  Points  checks  run at i n t e r v a l s Island. with  on  a  These  helicopter,  geological  features  points. routes and  of the v a l l e y  altimeter,  by  were  o f Hawkesbury  of making confirmatory  photographs  tops  traverses  most  supplemented  Traverse  gradient  was  undertaken  subsequent  and a l t i m e t e r  6000  were  consisting  aerial  work  t o the metamorphism.  Compass  2000  field  the r e l a t i o n s h i p of the Coast  and  at  of  on  the writer  on t h e p e t r o l o g y  rocks  of  while  of the geology  emphasis island  i s based  were  a topographic sides  a lesser  were  w h i c h was  chosen w i t h  located  map.  traverses  extent,  Owing  were  on v a l l e y  on s t e e p  corrected  the a i d of  slopes  at points  vertical  to the  generally  steep  run  along  floors. by  use o f an  o f known  elevation.  2 These  points  vertical were and of  feet.  located  on  owing  to  the  these  may  be  A  case  Bell  is  use  on the  timber  order  only  i f mapping by  this  AND  Division islands  tip  of  an  used  carrying  of  It  is  and  work  men  heavy  have  been  However, in  possible  error  for  eight  moving  base  camps.  camp,  carrying  starting points of  the  in  feet.  from  to  from  doubtful,  very  could  mapping  shore,  i n view  of  the  using  island  a.boat,  of  the  extremely  undergrowth,  and  heavy  completed  during  one  rain-  field  method.  Island  British a  fiord  area  of  Hawkesbury  Kitimat.  The  Rupert  a i r , and  by  was  out  accurate.  The  thousand  carried  location  ACCESS  of in  one  The  readings,  valleys, points  a l t e r n a t i v e method  combination  Hawkesbury  has  of  helicopter  sometimes  i n the  inaccurately.  G-2  LOCATION  It  very  model  topography  season  cover  be  valleys,  altimeter  to  w o r k was  a  photographs,  hundred  in  5  believed  is  one  tops and  ridges  the  The  ridge  within  possible.  back-packing.  fall,  aerial  on  to  wherever  located  and  accurate  points  field  be  rugged  of  be  landmarks  heavy  in  traverses.  and  to  The  supplies,  would  believed Reference  by  sightings points  one  are  is  located  in  It  is  the  of  which Kitimat  Columbia. at  the  head  approximately Island  island  is  is  95  about  about  80  i t s southern  the  largest  square 21  miles  miles tip is  Skeena of is  miles.  several located.  The  southeast  south-east 85  Mining  miles  by  northern of  of the  Prince shortest  3  Figure 1  water  route.  approximately  The  geographical  53°  06'  Hawkesbury Kitimat  or  the  island  onshore  wind.  working  in this  island. and  It  Island  are  float  largest  I t was area  could  the  island  of  of  topographic by  an  probably  glacial Valley with  using  the  Island  Western  features  area  trends  from  either  any  anywhere  on  part the  i n each major land  on  the  i t would  i s i n the  Coast  be  parts  with  helicopter is ideal to  harbour  most  particularly  plane  of  System the  separated  seem  and  by  largely  the  original  descending  on  of  of  the  ridge  three  or  an  for  tops  valley.  A  four  impossible  to  map  alone.  of Angle was  higher  former  a  stream  mainly  ridges.  structural  largely of  The  steep-walled  V a l l e y , and  parts  Region.  glaciers.  U-shaped,  by  sub-  developed  round-topped  unaffected  the  been  valley  numerous narrow  Mountains  Cordilleran  have  later  control  along  the  island  c o n s i s t s of  i c e accumulating  glaciers  a  boat  at  West.  I s l a n d , but  float  possible exception  that  but  07'  is  GLACIATION  valleys  the  likely and  island,  129° by  access  place  island  sheltered natural  on,  a  almost  could the  is a  easy  one  o v e r r i d i n g i c e sheet The  that  for  the  reached  land  least  Hawkesbury division  to  landed  adequately  TOPOGRAPHY AND  be  Hawkesbury  found and  be  plane  lakes  and  of  longitude  There  difficult  usually i n at  small  and  I s l a n d may  Prince Rupert.  between Kitsaway of  north  centre  control,  i t seems  topographic, the  island  channels.  and  snow  5 The and on  the the  presence highest  glaciers and  rounded  had  chatter  of  of  225°  on  of  three  or  four  is  be  expected,  sets  the  ridge  of  of  matterhorn  chatter  ridges  overridden  245°  to  absence  striae,  these  completely marks  tops,  glacial  parts  movement  to  ridge  marks  suggest  the  tops  island.  indicate  for  this  overriding  striae  were  seen  indicate  a  that  and  erratics  at  one  stage  Glacial  a  striae  direction  sheet.  parallel  of  These,  to  ice  Only  in valleys.  movement  peaks  the  as  valley  wall. In tributary U-shaped  addition hanging  profile  glaciers.  during  to  covered  the  glaciers  to  which  of  glacial valleys  present.  obviously have  These  occupied 500'  floors  large  the  west  of  was  of  numerous  have by  the  small  1700'  to  formed  the  east  to  the  ocean,and  a  possibly  During island is  the may  and  small  typical tributary  above  from  second have  later  isostatic  is  based  on  presence  of  a  the  one  during  This and  apparently  valley  figure  marine  Douglas  which  or  uplift  and  moved  completely  the  4000'  stage  stage  remnants stage  probably  second  Channel  at  been  recovery  glaciers  which  Sue  stage  3300 f e e t .  for  the  tfhird  the  glaciers,  to  formed,  figure  valley  glacier  i s l a n d ; and  the  development  stage  Passage  were  minimum  ance  a  glacier.  adjacent The  early  which  Channel  riding  sequence  an  down V e r n e y  are  were  valleys  main  floors.  The included  the  valleys and  These  main v a l l e y  to  of  the  large  glacier more makes of  over-  immediately  in an  500  post-glacial  thickness. allow-  feet, clays  at  6  300+  feet  above  thickness the  sea l e v e l .  of the glacier  highest  point  Canada,  published  Canada,  shows  I t makes  below  by  t h e 4000 f o o t  ing  Hawkesbury  has  an  3900+  of  f o r the  or i t s thickness  Island.  The  Glacial  Map  above of  the G e o l o g i c a l A s s o c i a t i o n of contour  of i c e thickness  Island i n the v i c i n i t y  elevation  allowance  sea l e v e l  on Hawkesbury i n 1958  no  feet  and  of Gale  as  cross-  Mountain, which  i s the highest  point  on  the  island. The granitic to  topography  rocks  has  of areas  significant  t h e f a r more homogeneous  The  valleys  in granitic  cross-section those  and  i n areas  of metamorphic  in  rocks.  but  on  of  higher  the island  types.  This  of metamorphic  feet. most  The  relief  highest  o f t h e map  and  relief  due  are  than  practically  the g r a n i t i c  to the hard  o f Hawkesbury  rocks  symmetrical  generally very  i s about  but none  rocks  t h e same  form  for  resistant  I s l a n d as spurs  seem  irregular  metamorphics  and  truncated  due  both  nature  compared were  t o be  with  noted  i n  preserved  in  rocks. on Hawkesbury  point  area  Cirques  and  rocks.  regular appearance  the adjacent  Several  i n the g r a n i t i c  Total  than  the l o c a l  rocks  a much more  rocks.  rocks  apparently  of the igneous  the mainland  peaks  of the mainland.  valleys areas  On  i s probably  the metamorphic  those  have  g e n e r a l l y a more  i n the former  considerably  differences,  character  areas  hemispherical the l a t t e r  u n d e r l a i n by metamorphic  Island  i s t h e peak  the tops  is  of Gale  of ridges  have  3950  feet  ±  40  Mountain.  Over  elevations  ranging  7  3000  from  feet  3200  to  Gale Mountain-Sidebacon tops  fairly  level  consistent glaciers have  surface,  could  valley  floor  2500  major  - Backbacon  These  ridge  a s maximum  of  100-500  at their  feet  heads.  and r i d g e  Lake  elevations  of the island  exception area,  t o p s may  that  be w h o l l y r e s p o n s i b l e .  elevations feet  The o n l y  Lake  feet.  over most  1000  to  3600  average  feet.  above  Average  where  represent  a r e so  i t seems Valley  an o l d ,  unlikely the generally  b u t r e a c h up  relief,  top, i s of the order of  ridge  remarkably  floors  sea level, local  i sthe  between  2000  feet  to  feet.  DRAINAGE  Drainage rivulets streams The  which  heads, neath beds. most  streams,  I n t h e upper of the valley  parts floors  and r a p i d s the main  material  characterized  and c o a l e s c e  fans  where  drop  streams  flow over  of  natural  levees.  in  regions  o f marine  The l a t t e r clays.  their  flow becross  the coast  their  where  to sea level  present.  abandoned  near  o f bedrock  o f f sharply  and p o s t - g l a c i a l  t o the ocean.  streams  and near  tiny  t o form  and g e n e r a l l y  ridges  o f streams  are usually  by numerous  valleys  and t h e main  up v e r y l a r g e  these, appearing only  alluvial  walls  i s by innumerable  out through the g l a c i a l  built  course  Island  over v a l l e y  tributary  have  waterfalls their  fall  draining  larger  on Hawkesbury  Throughout  most  of  a combination of  marine  clays.  channels  and t h e p r e s e n c e  are particularly  F o r t h e most  They a r e  part  well  developed  the o l d channels  8 l i e only a few feet from the new ones and have rarely been abandoned for more than a few tens of f e e t .  It i s probable  that the channel used varies from year to year, controlled by where the bulk of the material carried by spring floods i s deposited.  The main streams have an average width of ten to  twenty-five feet and a maximum depth of one to f i v e feet, except for plunge pools which may be up to twenty feet deep. A most interesting example of channel control by a l l u v i a l material i s South Beaver Creek, near the west coast of the island.  This stream drains into Beaver Creek through two  separate channels which reach the l a t t e r creek some apart.  During the summer of 1958,  2000  feet  due to most of the material  from the spring freshets being deposited i n the middle of the channel, this stream divided and flowed through both channels, which may be termed d i s t r i b u t a r i e s .  It seems l i k e l y that  during some years a l l the water flows through one of the a l t e r nate channels instead of forming this d i s t r i b u t a r y system. Most of the lakes on the island are of the tarn type. The p r i n c i p a l exceptions are Sidebacon and Backbacon Lakes, which are finger lakes; and possibly Evelyn Lake, Roy Lake and Beaver Lake, which are i n low overburden-filled valleys and appear to be held back by marine clays, a l l u v i a l material and possibly some morainal deposits. CLIMATE Hawkesbury Island, l i k e most of the Coast Mountains of  9 British The  Columbia,  average  has a v e r y humid  annual p r e c i p i t a t i o n  Kemano, K i t i m a t  and P r i n c e  Hawkesbury  Island  95  inches respectively.  months  (May-September)  Kemano  t o 29  -  i n May,  in  August  hours  a n d 54°  -  55°  i n September.  hours  Most  20  b e t w e e n May  due t o r a i n , About  until  early  sheltered  23.  September,  patches  inches and  inches i n  4.3  was  were  Island  - 61°  number o f  136  from  hours i n  was  mild  only  out  3 days than  cloudy but t o t a l figure.  were an  hours The  a l l summer, o r  had c o m p l e t e l y d i s a p p e a r e d , a p a r t  i n some  and  carried  probably less  t h e h i g h e r peaks  3.1  t o about  period  the average  49°  i s  57°  exceptionally  this  temper-  stations  i n July,  about  t h e summer  monthly  The average  was  rainfall  o f t h e days  mantles  61°  varies  During  p r o b a b l y f a r above  usually  -  on Hawkesbury  and t o t a l  one-third  s u n s h i n e was  snow w h i c h  of  and J u l y  94  stations  during  Average  i . e from  o f 1958  T h e summer  o f t h e mapping  56°  Rupert  i n September,  inches,  f o r these  i n June,  dry.  of  Rupert.  of record  f o rPrince  stations i n  a p p r o x i m a t e l y 15  from  55°  p e r day.  inch.  period  climate.  nearest  precipitation  -  hours  lost  the three  53°  of sunshine  t o 95  May  varies  inches i n Prince  f o r the total  50°  Rupert,  Average  mild  at meteorological  i s a p p r o x i m a t e l y 74  to  ature  and f a i r l y  of the higher valleys,  from  by t h e end  July.  FLORA  The cedar  valleys  and balsam  support heavy  stands  f i r to an elevation  o f hemlock,  o f about  2000  yellow  feet.  Hem-  10 lock  i s t h e most  juniper were  abundant  and r e d cedar  seen heavy  and  t h e undergrowth, mainly  and  similar  to  have  a diameter  carried  out near  shoreline been  some  alder,  t h e mouth  four  reach  Club,  size  huckleberry,  Lumbering  of Evelyn Creek  winters  large  S e v e r a l hemlocks feet.  pine,  tamarack  of mild  a very  Devil's  i s luxuriant.  jack  and a few  Because  of the trees  o f about  spruce,  locally  wet a r e a s .  and  shrubs,  Sitka  a r e abundant  i n particularly rainfall  species.  were  found  has been  and a l o n g t h e  between Danube B a y and E v a P o i n t , b u t no work has  done  elsewhere.  FAUNA  Wild the  larger  life  i s not plentiful  animals,  goats  are believed  never  seen,  ridges the  grizzly  its  presence  cuttings  only black bears t o be p r e s e n t  but t h e i r  and t r a c k s bear  trails  were  seen  i s common  on t h e i s l a n d  were  found  i n the v i c i n i t y  a n d t h e dams a r e i n a s t a t e  of  larger black  during  ponds  ducks  and Beaver  have  died  and streams  living  t h e summer.  scarce.  found.  seen  the  but very  the tops  Valleys.  seem  on them.  Partridge  No  Birds  Although of  dams a n d  Lake  fresh  and Roy  cuttings so that  were  i t seems  a r e numerous. A l l  t o have  Geese were are present  were  of a l lthe  Old beaver  of disrepair,  out.  They  no e v i d e n c e  of Evelyn  Of  Mountain  occasions.  on t h e m a i n l a n d ,  and i n Angle  the beavers  common.  on s e v e r a l  was  Island.  seem  run along  Lake  likely  on Hawkesbury  one o r two seen  families  several  but r a r e .  The  times only  11 fresh-water long.  These  fish  seen were  are not  brook  trout,  never  over  six  inches  common.  0  CHAPTER  GENERAL  PREVIOUS  Mountains,  g e o l o g i c a l mapping  p r i m a r i l y because  economic  interest  as  rainfall,  heavy  cover  mapping  and only  anything and  Survey  of  Canada.  1922  Coast  Previous consists Ecstall  of  (1)  Mine  1 V. Between Burke P a r t A,  1921,  Between Summary  the and  been  few  done  i n the  known d e p o s i t s  topographic  scarcity  of  features  outcrop  t r a n s p o r t a t i o n extremely  by  work  miles  V.  the a  day,  i n 1951»  of  mapping  and  Coast of such heavy  difficult  1  was  of  2  a  and and  w h i c h was  for  very  and  30  of  carried  at  into  an  average  only  two  rocks.  miles  out  Geological  generalized  Hawkesbury  square  about  shoreline  the  mapped  metamorphic  Dolmage, " C o a s t and I s l a n d s I n l e t and D o u g l a s C h a n n e l " , pp.  22-49.  the  differentiated  vicinity  some  Island  of  c o a s t l i n e being  i n the  mapping  Hawkesbury  Dolmage, * '  mapping  Intrusions work  on  i s the  Dr.  This  nature, 20  some  divisions,  ruggedness,  previous  1921  of  climatic  i s published  reconnaissance  of  has  expensive.  during  rate  and  w h i c h make  slow The  which  GEOLOGY  G E O L O G I C A L WORK  Little  timber  II  in  Island  around  the  conjunction  with  of B r i t i s h Columbia G.S.C.Summary R e p o r t  2 V. D o l m a g e , " C o a s t and I s l a n d s o f B r i t i s h C o l u m b i a D o u g l a s C h a n n e l and t h e A l a s k a n B o u n d a r y " , G.S.C. R e p o r t . 1922, P a r t A, p p . 9-34.  13 extensive development work on this property, (2) the mapping of a large part of the E c s t a l l septum between the Skeena River  3 and Douglas Channel during the summer of 1958 and  (3)  by W.A.  Padgham  the mapping of the mouth of the Skeena r i v e r along the  Grand Trunk P a c i f i c Railway i n 1912  by R.G.McConnell.  4  Of the  reports on this work the f i r s t i s not available to the public and McConnell's contains l i t t l e about the metamorphic rocks of the E c s t a l l septum, so that the only work of any value i n d i s cussing the geology of Hawkesbury Island i s Padgham's. fortunately this work was  Un-  carried out on so large a scale that  the numerous rock types present could only be subdivided into groups rather than separate petrologic units, as w i l l be attempted i n this t h e s i s . Other reports have appeared on mines and mineral  occurr-  ences i n the Coast Mountains, but none of these has any direct connection with the geology of Hawkesbury Island, so they w i l l not be discussed here.  A l l of these reports which the writer  has been able to find are l i s t e d i n the bibliography. GENERAL GEOLOGY The rocks of Hawkesbury Island consist of metamorphic rocks o f the E c s t a l l s e r i e s , both igneous and sedimentary i n 3 W.A. Padgham, Geology of the Ecstall-Quaal River Area, B r i t i s h Columbia. 1958, Unpublished M.A.Sc Thesis, University of B r i t i s h Columbia. 4 R.G.McConnell "Geological Section Along the Grand Trunk P a c i f i c Railway from Prince Rupert to Aldermere, B.C.," G.S.C. Summary Report, 1912, pp. 55-62.  14 o r i g i n , which are intruded by plutons of g r a n i t i c rocks of the Coast Intrusions and of at least one ahdesitic(?) s i l l .  The  E c s t a l l Series rocks and Coast Intrusions are intruded by a few late hornblende lamprophyre dykes.  The youngest deposits  are unconsolidated a l l u v i a l material, marine blue-grey clays and scarce g l a c i a l and g l a c i a l - f l u v i a l deposits.  A table of  rock units, showing the nature of the contact, the age of the units and their major subdivisions i s on., the following page. The rocks of the E c s t a l l Series form a mass which i s surrounded by g r a n i t i c rocks of the Coast Intrusions.  It i s  not known whether this mass i s a roof pendant or a septum. The presence of small stocklike bodies of g r a n i t i c rocks surrounded by extensive swarms of g r a n i t i c dykes i n the central parts of the E c s t a l l series i n the map area suggests a grani t i c f l o o r at no great depth, i . e . that this mass i s a roof pendant.  The rocks of the E c s t a l l S e r i e s , on the other hand,  might a c t u a l l y not be floored by the Coast Intrusions but : form a "screen" between several of the numerous intrusions i . e . be a septum. The E c s t a l l septum, or roof pendant, i s known to extend from north of the Skeena River south through the E c s t a l l River area, across Hawkesbury Island and up Gardner Canal. I t s minimum length i s 80 miles.  Probably  i t continues south of  Gardiner Canal to Graham Reach or Sheep Passage and north of the Skeena River to Portland Canal, which would give i t a t o t a l length of some 180 miles.  Its width ranges from less than 3  15 TABLE  OF ROCK U N I T S  Age Pleistocene  and Recent  Unconsolidated sediments Clay, sand, gravel, e t c . , (including marine bluegrey clays) Unconformity  Age  Unknown  Hornblende Lamprophyre and sills Intrusive  Jurassic-Cretaceous ( p r o b a b l y Upper Jurassic)  Age  dykes  Contact  Coast Intrusions: Pegmatite G r a n i t i c dykes Granodiorite, quartz monzonite, Monzonite,quartz d i o r i t e and diorite  Unknown  Andesitic Intrusive  Pre-Jurassie (possibly OrdovicianDevonian)  (?) s i l l s  and  dykes  Contact A E c s t a l l S e r i e s Rocks: "Meta-igneous amphibolites"  Intrusive  Contact "Plagioclase amphibolites," quartz-K-feldspar-plagioclase gneisses, kyanite-staurolite-almandine mica schists, quartzites, limestones, graphitic quartz-plagioclase schists, etc.  &  The w r i t e r w i l l r e f e r t o the E c s t a l l r o o f pendant throughout t h i s t h e s i s . venience but a l s o r e f l e c t r o c k s p o s s i b l y do f o r m a  the metamorphic rocks forming o r septum as t h e " E c s t a l l S e r i e s " This i s mainly a matter of cons the writer's believe that these time u n i t .  miles  at  the  Ecstall  Lake-Foch Lake The  width  on  The may  be  area  mine just  Hawkesbury  metamorphosed  into  igneous  to  the  Island  metamorphic  subdivided  t o more  rocks three  than  north  of  the  the  metamorphosed  the  "igneous  amphibolites",  are  "plagioclase  amphibolites",  rather  conformable with  per  cent  consist  of of  the  the  numerous i n the  The  very basic  the  septum.  Of  the  other  staurolite-almandine Each  of  these  makes  about  types  major  mica up  units.  40  the  per  the  one  igneous  which  cent  of  are per  the cent  the  the  to 55  some  of  which  types,  most  rocks  of  the  kyanite-  most of  seem  sediments  a l l these are  The  form  divisions  Of  and  rocks,  extent.  q u a r t z i t e s and  schists  about  area  are  metamorphosed  plagioclase-K feldspar-quartz gneisses up  Island  sediments,  the  make  rock  Channel.  These  rocks  listed  They  of  Amoeba  miles.  minor  are  abundant.  table  10  metamorphosed  The  types,  Douglas  groups.  of  series.  rock  i n the  Hawkesbury  metamorphosed  Ecstall  miles  "plagioclase amphibolites"  the  be  sediments.  of  averages  broad  rocks,  11  important.  the  rocks  of  the  septum. The the  Ecstall  ticularly  metamorphosed series  common  igneous  cutting  i n the  amphibolites"  the  half  feldspar-quartz  of  the  gneisses  other  southern  "plagioclase southern  the  are  map  part  are  rock of  found  and  the  northern  throughout  types but-are  par-  ;  the  septum.  also particularly  area  i n the  rocks  The  common  in  plagioclase-K half.  Considerable  17 interbedding  between  these  units occurs.  kyanite-staurolite-kyanite interbedded  with  part  septum  of  the  the  occur  in  the  southern  The  one  in  both  the  boudin. later to  the  The consist of  one  of of  the  pegmatite the  The  of  rocks  Hill  and  stock-like  13  pluton,  underlying  at  least  4  of  granitic  in  which  width  to  Sidebacon  least  dykes  one  square  the  size  of  pluton.  Lake  pluton  pluton  2000  to  i s one  3000  feet  of  been  wide.  Its  3  by  is  foot  intruded relationship  are  the  north and  the  dyke  4 miles wide  and  Within  rocks  the  width  these  within Lake  Danva has  of  Lake pluton  a  swarm  the  zones  proportional in  swarm  that  the  Beaver  pluton  wide,  facies  innumerable  the  and  i s roughly The  of  Sidebacon  miles,  The  Island  i s a marginal  granitic  i t .  found  mile  to  Each  are  Beaver  which  mile.  swarms  i s about  foot  Hawkesbury  miles  dyke  pluton  on  square  the  Lake  septum.  10  a  have  squares  associated with  the  the  plutons  plutons  least  southern  andesitic(?) rocks  form  masses  sills  at  i n the  unknown.  stock-like  dykes  of  the  intrusion,  underlying  at  of  examined  pluton,  underlying  parts  they  is  occur  quartz-plagioclase  deformation.  batholithic  and  limestones  "plagioclase amphibolites"  i s believed to  several small  septum.  where  Intrusions  main  the  northern  period  North  veins  with  area  intrusive Coast  and  graphitic  occurrence  type  main  the  septum, and  known  rock  the  other  and  Brooks  This  than  The  interbedded  Trench  schists  quartzites,  "plagioclase amphibolites"  only.  schists  mica  The  around  that  around  around areas  the  the the Danva  granitic  18 rocks  may  outcrop areas  dykes  They c o n s i s t  some m o r a i n a l  rock  to silt  floors  sea  330  valley.  from  of the Outside  total these  few dykes  to the north  Their  i n the  o f t h e septum  feet  marine  present,  clays.  s c a t t e r e d over  of well-rounded five  They  through  feet  clays  which  or weakly to  sub-angular  o r more i n  the bedrock  although  of Evelyn i s 330  an i s o s t a t i c  since the retreat  the fans  fifty  a t the  principally i n  Lake. feet  Their  maximum  above .  readjustment  of the valley feet  to  common-  thicker.  a r e found  Valley)  o f 250  the  generally carpet the  a r e a p p a r e n t l y much  A t an e l e v a t i o n  definitely  i s b e l i e v e d t o be f i v e  indicating  de-  I t i s probable  b u t none  are found  of the valleys,  ( i n Angle  alluvial  feet.  and i n the v i c i n i t y  probably  and o t h e r  boulders  veneer  marine  to the valleys.  are unstratified  thickness  most  fans  particles.  i n a thin  elevation  level,  least  size  blue-grey  Valley  recorded  3300  deposits  o f some v a l l e y s The  Angle  of  ranging  throughout  heads  are very  erratics  outwash and c o n s i s t  outcrops.  feet  There  blue-grey  Glacial  alluvial  fragments  valley  per cent.  are confined mainly  alluvial  t o an a l t i t u d e  diameter  t o 15  exposed  material i s also  identified.  stratified  ly  deposits  of talus,  The  per cent  Island.  and p o s t - g l a c i a l  ridges  10  scarce.  of the batholith  Recent  was  perhaps  are quite  Hawkesbury  posits  up a s m u c h a s 75  make  and average  vicinity on  locally  i n Angle  glacier Valley  of at  i n this  several  19 specimens clays,  establishing  pelecypod a  of Saxicava  has  geographic age  The  blue-grey  o r >  and  slumping  from  determinations  at  Saxicava dips  their  20° as  clay  the  marine  or  S.E.  It  to  and  i n Angle  is in a  from  of Miocene  i n most Valley  of  where  attitude  stream  bank.  is the  conditions. horizontal.  specimens  n o r t h 40° may  and  i t useless  climatic  places  this  to Recent  making  i t strikes  this  similar  Unfortunately  Greenland,  collected,  i s possible  exposure  origin.  determinations  i s bedded  were  collected  range  Panama  locality  arctica  this  were  stratigraphic  range  for  However,  a  arctica  be  east  due  to  CHAPTER I I I  THE  METAMORPHIC  ROCKS  INTRODUCTION  The listed  i n the Table  the  basis  and  textural  mentary all  metamorphic  have  rocks  o f Rock  features.  category  have  compositions  The rocks  "plagioclase  have  suggests  i s f a rtoo basic  amphibolites" which  have  indicate  than  25  blende, of and  these  per cent  f o r a normal  biotite  those w i t h more  origin  meta-sedi-  sedimentary rocks.  The  Their  but t h e i r  sediment.  and  sedimentary  The  mode  compos-  "igneous  occurrences  a r e not o f sedimentary  tex-  origin.  AMPHIBOLITES  than  50  a r e rocks  per cent  c o n t a i n i n g more  o f combined  horn-  25  per cent  a r e included i n the meta-sedimentary  division  and d i o p s i d e .  minerals  i n these  and i n most  amphibolites  and l e s s  any  on  relationships  a r e r a t h e r anomalous.  a sedimentary  they  plagioclase  with  been present  P E T R O L O G Y OF T H E P L A G I O C L A S E  The  included i n the  has destroyed  compositions  units  relationships  possible  amphibolites"  occurrence  field  compatible  w h i c h may  the units  smaller  cutting  features  tures  and i n t o  into  a lack of cross  Recrystallization  ition  Units  of mineralogical composition,  origin.  of  are sub-divided  than  50  Rocks  per cent  with  less  than  i n t h e meta-igneous  division.  The plagioclase amphibolites  are subdivided into  (1) plagioclase-hornblende-biotite rocks, lacking diopside and containing 5 per cent or less of epidote group minerals (2) plagioclase-hornblende-biotite-epidote rocks, similar to the above but with more than 5 per cent epidote; (3) plagioclase-hornblende-biotite-diopside (4) p l a g i o c l a s e - s t a u r o l i t e amphibolites, s t a u r o l i t e and hornblende.  amphibolites;  containing both  These d i v i s i o n s are further subdivided on the basis of the r e l a t i v e proportions of these minerals. A l l the plagioclase amphibolites ance i n hand specimen and may  be described together.  dark grey, generally fine-grained ( 1 mm.) medium-grained ( 1 mm b l a s t i c i n texture.  to 5 mm)  havec.a similar appearThey are  but occasionally  rocks most of which are grano-  A few specimens are porphyroblastic.  The plagioclase amphibolites weather to various shades of brown or reddish brown. 1/4  The weathered layer i s normally quite t h i n ,  inch or l e s s , but i n sulphide r i c h rocks i t may  be several  inches thick, making i t d i f f i c u l t to take a fresh sample. Turner defines s c h i s t o s i t y or f o l i a t i o n (which he considers to be synonymous) as "any p a r a l l e l structure, of metamorphic o r i g i n , that induces a more or less planar b i l i t y i n a rock.""''  fissi-  In these rocks the degree of f o l i a t i o n  i s determined mainly by the percentage of b i o t i t e , c h l o r i t e and, to a lesser extent, muscovite, i n the rock.  1 H. Williams, F.J. Turner, CM. (W.H.Freeman and Co., 1955)) p. 169.  Those rocks  Gilbert, Petrography  lacking weak  biotite  schistosity  unusually some  flat  slight  flattened  after weak  only  bands  i s present  except  f a r from 1 mm  generally Evelyn feet  Lake,  wide  (1/25  only  (1)  subdivision  sections  this  subdivision.  width Near  colored  (6  cm (2  to 3  inches)  of the amphibolite  plagioclase-hornblende of biotite;  containing  rocks  amphibolites  the eastern several  across,  than  5 per cent  t i p of hundred  although  rocks  rocks  rocks,  be f u r t h e r  17  24  to  into  5 per cent  or  amphibolites,  of hornblende  and p l a g i o c l a s e - b i o t i t e g n e i s s e s ,  Of  belong  divided  containing  each  form the  amphibolites.  plagioclase-hornblende-biotite  greater  minerals  inches).  group  may  develop-  o f t h e bands i s  of amphibolite  of the plagioclase  These  generally i s  i s not well  and d a r k  plagioclase-hornblende-biotite  thin  biotite,  cm.  then  amphibolite.  The p l a g i o c l a s e - h o r n b l e n d e - b i o t i t e The  less  or less.  an area  5 t o 7.5  tendency i s  of a l l the sub-types  occurrences  colored  up t o 15  as  i n t o m a f i c - r i c h and m a f i c - p o o r  The average  inch)  however,  has bands  averaging  largest  complete.  of  t o be  and o n l y  Lineation  i n one o r more s p e c i m e n s  of the l i g h t  as w e l l  The l a t t e r  varieties  extremely-  alignment  and f e l d s p a r  hydrofluoric acid.  common b u t i n m o s t  separation  being  grained  Segregation  an  crystals,  the plagioclase-hornblende-staurolite  i s quite  ed,  hornblende  t o the hornblende.  with  a t best  due t o a p l a n a r  f o r the quartz  i n medium  or lacking.  specimen,  i s mainly  and t a b u l a r  tendency  etching  i n hand  which  parallel  noticeable  It  have,  containing  and o f 5 per  23 cent  or  that  they  of  less are  mapping.  main  rock  of  hornblende.  not The  types  mappable  These field  d i v i s i o n s are  units,  on  the  major  southern  band  of  small  present  plagioclase-hornblende-biotite i n the  so  rocks  scale are  the  plagioclase  amphibolites. Figure  2  Figure  shows  2.  the  approximate  range  of  composition  ACF d i a g r a m f o r t h e a l m a n d i n e a t amphibolite facies, staurolitequartz s u b f a c i e s , showing the range of composition of the plagioclase-hornblende-biotite rocks  of  the up  plagioclase-hornblende-biotite rocks of stable  arbitrary by  mineral  compositions  c r o s s e s , were  hornblende, inous  assumed.  magnesia  trial the  field  rocks  plotting  was  chosen  of certain  hornblende-biotite  gneisses The  1.  amphibolite  i n the stauroliteA high  f o r the biotite specimens  amphibolite  showed  and  alumina, as a this  was  plagioclase-  a r e t h e commonest  are comparatively  compositional  range  The  sub-types  of  plagioclase-  rare.  of these  types  a r e as f o l l o w s :  Plagioclase-Hornblende Amphibolite (based on 8 t h i n s e c t i o n s )  Mineral  Total  Variation  (An2Qto A n Quartz Epidote Apatite Sphene Chlorite Sericite "Iron Ore"  i n Percentage  Mean  30 - 35% 1 3% 2 4 - 61%  Hornblende Biotite Plagioclase  &  o f aluminum p o s s i b l e  plagioclase-hornblende-biotite rocks.  biotite  alum-  satisfactory. Plagioclase-hornblende  the  f o r the  t o be a r a t h e r  amount  fall  indicated  chosen  o f t h e ACF diagram.  composition  and e r r o r  most  t h e maximum  any o f these  epidote-almandine low  The composition  t o b e made  of plotting,  and hornblende,  be shown p r o b a b l y  contains  making  F o r ease  of biotite  which w i l l  variety,  without  assemblages.  considered  4  0  w  )  Percentage W° 1% 59%  a  5%  3 - 22# none 5% JO  none none  A l l determinations  <1% 2$ 1% <1%  o f An content  w e r e made b y m e a s u r i n g fragand a monochromatic l i g h t  X' 010 f o r s e c t i o n s l a o r b y m e a s u r i n g N ' o n c l e a v a g e A  ments u s i n g source.  x  special  index  oils  25 2.  Plagioclase-Hornblende-Biotite (based on 7 t h i n s e c t i o n s )  Mineral  Total  Hornblende Biotite Plagioclase (An^o t o A n Quartz Epidote Almandine Apatite Sphene Sericite "Iron Ore"  3.  Amphibolite  Mean  V a r i a t i o n i n Percentages  25$  15 - 35% 1 0 - 20$ 40 4 3  )  Percentage  12% 48%  -  5 - 15% none none  -  < 1 none  8% 2%  5% 2%  < 1% 2% < 1%  -  1%  P l a g i o c l a s e - B i o t i t e Gneiss (based on 2 t h i n s e c t i o n s )  Mineral  Total  V a r i a t i o n i n Percentages  Hornblende Biotite Plagioclase t o Anog) Quartz Epidote Almandine Chlorite Muscovite Sericite Apatite "Iron Ore"  none 20  54  (An3i  These section. blende  Most  Mean  Percentage  27$  63%  io - 15% none < 1 none  sub-types  are quite  specimens  amphibolites  1% < 1% <1% < 1% similar  of fine-grained  have a w e l l  developed  i n texture  i n thin-  plagioclase-horngranoblastic  In  a l l medium-grained plagioclase-hornblende  in  a l l the plagioclase-hornblende-biotite amphibolites,  of  the hornblende  commonly sieve  enclose  grains small  or p o i k i l o b l a s t i c  a n d some  grains  texture  amphibolites,  of the plagioclase  of other  minerals,  i s developed.  texture. and  most  grains,  so that  a  Hornblende i n  26 the  plagioclase-biotite Hornblende  subhedral. negative  It  with  and  Z c A  as  Rock  large  is a  shown  a l s o has  i s generally euhedral  is rarely a  There  gneisses  twinned  on  . this but  (100)  sieve  i n some  and  is  texture. specimens  biaxial  2V.  systematic  i n the  variation  following  Type  i n pleochroic  formula  table.  Pleochroic  formula  X Y Z  pale pale blue  yellow blue green green  21°-22  Plagioclase-hornblendeb i o t i t e amphibole Plagioclase-hornblende amphibolite  X Y Z  pale blue dark  yellow green green  22°-23  P l a g i o c l a s e-hornblende amphibolite  X  pale  yellow  Y Z  brownish greenish dark brownish green  X Y Z  p a l e brown brown d a r k brown  Plagioclase-biotite  Increasingly with  2  and  hornblendes green =  deep  i n c r e a s i n g grade  Turner  Z  gneiss  but  of at  brownish  (W.H.  i n the Sept.  Compton^. the  higher  p l e o c h r o i c c o l o r s and  of metamorphism The  former  amphibolite grades  have  found  facies  c  23°-24°  higher  t h a t most  of metamorphism  Zc A  been noted  have Z  =  c  of  deep  by the blue  ( w i t h i n the  facies)  green.  2 H.Williams, F r e e m a n and Co.,  F.J.  Turner, CM. p. 242  1955)>  Gilbert,  Petrography  3 R.R.Compton, " S i g n i f i c a n c e o f A m p h i b o l e Paragenesis B i d w e l l Bar Region, C a l i f o r n i a , " American M i n e r a l o g i s t pp.  1958,  890-907.  27 Both Compton " and Eskola^ analysed a number of horn4  blendes and found an increase i n A1 0^, MgO 2  and CaO  and  decrease i n FeO and F e , ^ with a higher grade of metamorphism. They suggest that the color of hornblende i s controlled mainly by the amount of alumina, a deeply colored hornblende being a highly aluminous  one.  B i o t i t e occurs as tabular plates, euhedral from ragged terminations.  apart  In thin sections containing horn-  blende most of the b i o t i t e i s marginal to the hornblende or cuts through i t , and i s obviously a l a t e r mineral, than the hornblende which i t replaces.  Most of the b i o t i t e grains are  p a r a l l e l or sub-parallel to the f o l i a t i o n , but i n one section of b i o t i t e gneiss, i n which the b i o t i t e l i e s along  the  grain boundaries of the plagioclase and quartz, many b i o t i t e plates have developed along these boundaries at large angles to the general f o l i a t i o n .  These are noticeably smaller than  the b i o t i t e plates p a r a l l e l to the f o l i a t i o n .  Most of the  b i o t i t e i s a strongly colored variety which i s pleochroic from deep reddish brown (Z) to pale brown or straw yellow  (X)  but i n some sections of plagioclase-hornblende-biotite amphib o l i t e , Z i s a very dark brown and i n a section of plagioc l a s e - b i o t i t e gneiss, i t i s brown with a greenish cast.  4  In one  Compton, l o c . c i t .  5 P. Eskola, "On the petrology of the Orijarvd region i n southwestern Finland, "Comm. Geol. Finlande B u l l . No. 40 (1914), p. 113.  thin the  section biotite,  pyrite, pale  perhaps  i n the  vicinity  yellow.  indicating  and  shows  plagioclase-hornblende-biotite amphibolite  i s bleached  straw  bent  of  evidence  (rarely)  inclusions all  of  ionally The  types  also  A  few  have  i s , as  per  cent  very  broad,  1  2  a  at,  per  type or  type quite  determination  or  individuals.  or  plagioclase  albite  of  Biotite  i n most  although  sodic or  zoning.  grains narrow  subhedral  The  table  andesine,  but  highly calcic and  a  Most  core  of  Many  of  of  as f e w  the  the  individual lamellae  are  not  is  twins, to  lamellae  indistinct.  It  i s not  set  of  definite  probably sub-  are  complex  twinning  another. lamellae what  rim  Perhaps  p o l y s y n t h e t i c twins  one  a  rare.  sets  i s present  only  eight  two  one  The  grains  i n which  to  very  twinned  grains  angles  occas-  and  twinned  right  25»  page  oligoclase.  the  of  have  in  of An^i  three twin  on  zoned.  albite  as  rounded  is  sericite  are weakly  to  plagioclase  of  twinning  is  sections  i n small  i n the  indicated  consist  I n most  nearly at,  to  low b i r e f r i n g e n c e ,  in large  shown  grains  twinning.  more,  cent  but  hornblende.  slightly  i . e . reversed  only  yellow  chlorite.  occurs  feldspar is exceptionally fresh  An-jg,  of  section  generally occurs  or  a  probably  strain.  g r a i n s , but  rock  medium  satisfactory  60  thin  golden  p o r t i o n has  towards  h i g h l y sodic andesine  scarce.  of  bleached  in poiMloblastic  these  generally  The  of  anhedral  opaque m i n e r a l ,  i s p l e o c h r o i c from  i n one  Plagioclase  an  and  alteration  fractured  no  of  types  develop  Where are of  this  usually twins  are  29 represented here, but a l b i t e - p e r i c l i n e i s probably the commonest combination which would have this appearance.  No Carlsbad-  a l b i t e twins were noted. Quartz occurs as large anhedral grains and also as small inclusions i n p o i k i l o b l a s t i c hornblende, and more r a r e l y i n plagioclase.  In one t h i n section of plagioclase-horn-  blende amphibolite vein quartz i s also present.  I t i s not a  major mineral, generally forming between 5 per cent and 15 per cent of the rock.  As i t i s d i f f i c u l t to d i s t i n g u i s h from  untwinned plagioclase, p a r t i c u l a r l y as this i s unaltered or nearly so i n most thin-sections, percentage estimates were checked by making o p t i c a l determinations on ten grains per section, and by hydrofluoric acid etching on several  specimens.  Quartz only rarely shows evidence of s t r a i n . The common epidote group mineral, present, p i s t a c i t e , i s c o l o r l e s s , has a large negative 2V, anomalous " b e r l i n blue" interference colors and a birefringence of approximately 0.03, which corresponds cent BX^Fe-^SI^O^  a  n  d  to a composition of about 18 per  $2 per cent H C a ^ l ^ S i ^ O ^ '  T t i e  c l i n o  "  z o i s i t e - p i s t a c i t e boundary i s drawn at about 10 per cent IK^Fe^S 130^2•  T  n  e  maximum known percentage of IK^Fe^Si^O-^  i n p i s t a c i t e i s about 40 per cent, so i t would seem t h i s i s a moderately iron-poor p i s t a c i t e .  Turner' notes that the epidote 7  6 A.N. Winchell, Elements of Optical Mineralogy Part II (John Wiley and Sons, 1948), p. 313 7 H.Williams, F.J. Turner, C.M.Gilbert, Petrography (W.H.Freeman and Co., 1955)» p. 242.  30 (pistacite)  of amphibolites  yellowish.  I n one t h i n  less  pistacite  occurs  ore",  probably  other  minerals,  a  rather  percentage result of  and might thin  usual of  pistacite  pistacite  always  anhedral  occurs  i n a thin  is  epidote grain  group  minerals  boundaries  clase.  Crystal  epidote  i s partially  offered  less  or  form  this  occurs  i n a thin  This  i s a much  masses  enclosed  Allanite  as  of similar  resistance to i t s crystallization  It  cores crystal  Most  grains of  and  occur  and  plagio-  w e l l developed which  of the  and i s  gneiss.  or b i o t i t e  i n biotite,  of  the margins  of pyrite,  or subhedral,  i s particularly  those  along  position.  hornblende  epidote  non-pleochroic,  and occurs  pistacite  high  i s the  section  plagioclase.  brown,  are euhedral  An  like  but i t occurs  extinction  between  any o f t h e  epidote  of plagioclase-biotite  of colorless  but d i f f e r e n t  biotite  of plagioclase.  replaces  brown t o p a l e  than  "iron  and a  and i r r e g u l a r  section  by rims  orientation  rocks,  of  color-  bleached  properties very  and c l e a r l y  p l e o c h r o i c dark  surrounded  on  i n these  to  as t h i s i s  amphibolite.  with  pyrite-quartz veins  origin  pale  be h y d r o t h e r m a l ,  probable  alteration  hydrothermal  plagioclase-hornblende  with  I t seems  a grain  ore" i s later  possibly  section  or very  a pleochroic, yellow  The " i r o n  o f opaques.  undoubted  colorless  as a r i m s u r r o u n d i n g  of hydrothermal  colorless  section  pyrite.  altered  i s either  when t h e  apparently than  hornblende  mineral.  Iti s  plagioclase. Almandine  found  i n only  garnet  three  thin  i s a rare  accessory  s e c t i o n s , two o f  plagioclase-  31 hornblende-blotite  amphibolite  gneiss.  i n colorless  ragged which but  I t occurs anhedral  have  some  ores". and  groups  sieve  texture.  The i n c l u s i o n s  Biotite-  i s no  to pale  plagioclase-biotite  pink,  isotropic,  of grains, to euhedral,  a r e o f sphene,  there  and one o f  porphyroblasts  Inclusions are mainly  apatite,  quartz,  of  biotite  and  d o n o t show a n y p r e f e r r e d  evidence  of any "snowball"  and h o r n b l e n d e - r i c h bands  appear  plagioclase, "iron  orientation  or s i m i l a r to flow  effects.  around  the  garnets. Apatite minerals. short  prismatic crystals,  o f the major  boundaries.  Sphene  clase-hornblende bolite, is  a faintly  rock,  i s found  i s also  section  from  green  parallel ference  crystals  euhedral,  scattered i s found  and b i o t i t e  rock  to colorless,  extinction,  which  throughout  at  grain  as  plagio-  between  and anomalous  of  hydro-  yellow  gneiss.  In the other  i s pleochroic  has p a r a l l e l  pale  crystals.  aggregates  and almandine  length fast,  the  larger  of plagioclase-biotite  The c h l o r i t e  It  rounded  s c a t t e r e d throughout  i n the v i c i n i t y  biotite unit.  gneiss.  occurs  as r o s e t t e s and f i b r o u s  replacing  of this  colors.  variety  i n one s p e c i m e n  found  thin  and a l s o  at the boundaries  occurs  hornblende  pyrite  occurs  to  i n the p l a g i o c l a s e - b i o t i t e  but p a r t i c u l a r l y  thermal  grains  accessory  and p l a g i o c l a s e - h o r n b l e n d e - b i o t i t e amphi-  and wedge-shaped  replacing  common  i n a l l thin-sections of the  p l e o c h r o i c brown  Chlorite  It  minerals  but i s absent  granules  are the only  A p a t i t e , i n s m a l l , rounded  stubby,  crystals  and sphene  grey  or nearly inter-  32 "Iron The it  pyrite .forms  consist  i s probably veins  pistacite  chiefly  partially  i n one s e c t i o n  i n another  normally to  ores"  opaque  hydrothermal  and  I n some  thin  ores" are partially  a reddish translucent material which  magnetite.  i n origin  and i s surrounded  section.  "iron  of pyrite  as  .  by a zone  of  sections the  or wholly  altered  i s probably  hematite  or l i m o n i t e .  (2)  The p l a g i o c l a s e - h o r n b l e n d e - b i o t i t e - e p i d o t e r o c k s This  sedimentary  unit  type  part  o f the main west  the  south  the  Sidebacon  side  are  of Angle  Lake  of thin  rocks  amphibolite  Valley  stock.  the main  minor  found  subdivision  On t h e b a s i s  plagioclase  s i d e o f Ice-Cake  throughout  these  small  i s b e l i e v e d t o be p a r t i c u l a r l y  the  very  a rather  amphibolites.  rock  of  forms  north-west  Lake  plagioclase  extent.  Outside  a r e known t o o c c u r  interbedded  with  rocks  which  extends  occur  amphibolite  band,  band  i n i s Wye  but they a r e  where  area they  plagioclase-quartz-K feldspar  gneiss. The of  these  major  rocks  minerals  i n the four  a r e as f o l l o w s :  thin  with  elsewhere  the only  Valley  from  from  to the contact  also  of this  this  i n that  t o t h e s e a , and  south-west  These  sections  abundant band  of the  sections  made  augen  Thin  30% 28$  6% 30%  Epidote Hornblende Biotite Plagioclase  (Anon t o A n ) Quarts &  —  ^  Determined  Thin The  bands  per  cent  section  vary  hornblende  hornblende. sections  Texture  hornblende  texture  10%  16%  rounded  individual on  biotite. ties  may  i n some  0.021  to  per cent  epidote,  sections occurs  of biotite  grains  banding.  epidote,  5  55 p e r c e n t I n some sieve  flakes  as a mosaic  and i n o t h e r  crystals  most  or completely  i s pistacite  which  of  s e c t i o n s as of which  enclosed  h a s t h e same  occur by  proper-  i n the plagioclase-hornblende-biotite  i n one t h i n  0.023,  95  developed  5)  to euhedral  as t h e p i s t a c i t e except  well  be p o r p h y r o b l a s t i c and have  to subhedral  The e p i d o t e  rocks  from  per cent  4 and  subhedral  the border  f o r sectionsl a  i s generally granoblastic.  (see figures Epidote  small,  t o 45  25%  Wo  has v e r y  i n composition  —  4-3%  A  #17-5  15%  3% 25%  A-2%  X' 010  by m e a s u r i n g  Number  27%  Q  ft  Section  section  corresponding  to  where  13  the birefringence i s  molecular  per cent  of  HCa^Fe^Si^O-j^. Hornblende  i s very  similar  plagioclase-hornblende-biotite erties. pale  Z c A  yellow,  i s 21° Y =  - 22°  blue  t o the hornblende  rocks  i n occurrence  and  and t h e p l e o c h r o i c formula  green  and Z =  dark  green.  i n the prop-  i s X =  34 Biotite brown  or  i n most  golden  sections  brown  erties A  few  to  that  grains  in  are  Quartz inclusions of  (Z)  is pleochroic Plagioclase  in  sections to  from  yellow dark  similar in  (X)  brown  from  reddish  but  in a  to  straw.  occurrence  occurs  few  and  prop-  plagioclase-hornblende-biotite  weakly  sieve  straw a very  i s very  the  is pleochroic  rocks.  zoned.  as  large  texture  anhedral  grains  hornblende.  It  and  as  small  shows no  evidence  strain. Apatite  They  have  apatite  and  and  sphene  i n the  replaces  quantities.  around  p y r i t e i n one  masses  of  no  from  (3)  the  and  only  occur  accessory similarly  The  the  feldspars  in  rocks,  section.  pyrite  to  rocks.  i n a l l sections,  the  type  i s found The  opaques  are  found  very  in  replacing  pyrite  p a r t i c u l a r o r i e n t a t i o n and  this  minerals.  plagioclase-hornblende-biotite  C h l o r i t e , of  clase-hornblende-biotite  Apart  are  similar properties  Sericite minute  sphene  is  may  in be  rare  but  the  plagio-  biotite  irregular hydrothermal.  i n these  sections.  Plagio-clase-hornblende-biotite-diopside amphibolites  bolites a  very  The  plagioclase-hornblende-biotite-diopside  are  represented  minor  division  by of  only  the  three  thin  plagioclase  amphi-  sections. amphibolites.  They  are  35 The  composition  of the sections  i s as  Thin  Section  8-6A Hornblende Diopside Biotite Plagioclase (An-DQ t o A n Quartz ^ Epidote Chlorite Sericite Sphene Apatite "Iron Ore" Calcite  In texture  6$ 7$ 22$ 25$  6$ 10$ — <1$ ^ 1$ <1$ <1$ —  9$ 13$ 2$ 11$ < 1$ <1$ <1$ 5$  ) 5$ 3$ — < 1$ < 1$ < 1$ < 1$ —  t h i n - s e c t i o n these  rocks  have  essentially  as t h e p l a g i o c l a s e - h o r n b l e n d e - b i o t i t e  plagioclase-hornblende-biotite-epidote  One  section  other  has p o r p h y r o b l a s t i c  of the porphyroblasts sections  replaced  elsewhere.  Sections  A  =  was  and,the  A  amphibolites. and  diopside. The  grains  noted  replacing or  t o subhedral  grains  but i s r a r e .  pleochroic  formula  follow:  #8-6A, #26-7  X = pale Z c  i n Z c  amphibolites  granoblastic.  and as e u h e d r a l  (100)  on  t h e same  the schistosity.  as s u b h e d r a l  by d i o p s i d e  Variations Thin  occurs  Twinning  hornblende  l i e across  are essentially  Hornblende being  26-7  20$ 25$ — 37$  and  Some  Numbers  13-6  30$ 3$ 5$ 53$  A P  follows:  yellow  22° - 23°  Y =  blue  green  Z =  dark  green  36 S e c t i o n #13-6  Thin  X  = pale  Z c  =  A  This the  other  hornblende  o r straw  partially  replaces both  altered  is colorless  noticeably second  and as  sphene i n the  3  per  mass  it  cite  thin  and  have  faint  cis-39°  section  (Z)  the  t osubhedral pale  t o color-  biotite  is  green  grains.  tint  and  is  interference color  t o-41°  quartz, the  diopside. I t  sericite.  a moderately  plagioclase,  and  o r r e d d i s h brown  maximum  and  the  not  is  diopside i s  l a r g e 2V.  epidote  (pistacite),  same p r o p e r t i e s a n d  ore"  consists  i n #26-7,  a few  o fsmall  probably  mainly  The  abundant  sericite  o fa l t e r e d by the  rock, also  pyrite  probably  chlorite  and  apatite  occurrence  and  ragged  grains.  (11 p e r  8 per  cent  calcite  products,  vein material.  and  These  magnetite.  o ffeldspar.  alteration  may b e i n t r o d u c e d  and  i n #26-7  biotite,  alteration  as the  euhedral  large anhedral  are  formed  are  A  hornblende o f  plagioclase-hornblende-biotiterocks.  cent  altered  The  Z  with  present  and,  opaques  a very  t o the  hornblende  as euhedral  o r has  yellow.  "Iron grains  green  rocks.  I n one  tochlorite occurs  positive The  Z = brownish  similar  brown  (X).  pleochroic.  order  biaxial  golden  yellow  Diopside It  i s very  plagioclase amphibolite  p l e o c h r o i c from  less  Y = green  24°  Biotite is  yellow  The  cent)  includes  offine  felty  This which  is a heavily are  although chlorite  present i n the has  cal-  37 parallel and  extinction,  a moderate  calcite large  i n elongate  unit  band  is  composed  contact  feet  wide  similar  rocks  was n o t s u s p e c t e d thin  with The  almandine sphene,  section  these  20  by o n l y  of mosaics of  may  occur  to exist  made  this  ores"  inch  (1.2  much s m a l l e r  medium-grained.  rock  schists,  type  5-foot  schist.  elsewhere  Iti s  i n the v i c i n i t y  as t h i s  i n the f i e l d  specimen  and l e s s and  than  unusual  and  from  this  hear  the  1  5 per  chlorite  4 per cent,  per cent  occur  of  apatite  the high  well  as porphyroblasts  Almandine  and h i g h l y a l t e r e d .  i s only moderately  per cent,  quartz  i n diameter.  Despite  i s staurolite  sericite.  sieve texture. cm)  15  biotite  and s t a u r o l i t e  poorly-developed  section  side of a  o f an a m p h i b o l i t e  of this  per cent,  5 per cent  "iron  1/2  one t h i n  where  on e i t h e r  p l a g i o c l a s e 44 p e r c e n t ,  Almandine  ion  The  rocks.  composition  hornblende  5 per cent,  are  biotite.  of kyanite-staurolite-almandine mica  the only  reach  interference colors  amphibolites  o f South Beaver V a l l e y ,  that  type  cent,  grey  replacing  kyanite-staurolite-almandine mica  rock  a  areas  i s represented  some 20  a band  probable of  I t occurs  The p l a g i o c l a s e - s t a u r o l i t e  t h e head  wide  yellow  grains.  This  forms  relief.  occurs  (4)  from  anomalous  developed.  porphyroblasts  The s t a u r o l i t e The other  content  with  grains  minerals are  of biotite  foliat-  38 Hornblende  occurs  i n euhedral  Z^e  i s 22° and t h e p l e o c h r o i c formula  Y =  blue  ous  hornblende  green  and Z =  chlorite.  quartz 2V,  chroism  I t contains  from  deep  blende  Chlorite  chlorite to  nearly pale  green  colors.  i.e. clase  and s t r o n g  a  large  pleo-  yellow.  plates replacing  horndark  and aggregates  and s t a u r o l i t e .  i s partly preserves  grains.  extinction,  grains  (unzoned  f o r cleavage  source,  with  of  strung  out  t h e shape  A l l the c h l o r i t e i s p l e o c h r o i c from  of  The  parallel  of the  has p a r a l l e l medium  or  green  to  greyish yellow interference  I t i s length-fast.  position x  but i n part  and has anomalous  Most  N '  replaced  inclusions  positive  flakes  almandine,  staurolite  staurolite  parallel  being  I t i s p l e o c h r o i c from  as ragged  biotite,  the f o l i a t i o n  alumin-  yellow (X).  replacing  original  as s u b h e d r a l  yellow,  area.  grains  to pale  staurolite.  occurs  replacing  of this  relief  grains.  i s t h e common  a few n o n - o r i e n t a t e d  yellow  i s found  (Z) t o straw  flakes  This  It is biaxial  golden  and p o s s i b l y  i s X = pale  i n irregular  birefringence, high  Biotite  brown  occurs  and p l a g i o c l a s e .  h a s weak  green.  of the amphibolites  Staurolite by  dark  to subhedral  of plagioclase  determined  as A n ^  flakes  index  and a sodium  i s a slightly  grains  I t s com-  g r a i n s ) was with  and as An44 by m e a s u r i n g  this  are subhedral.  a r e zoned.  calcic  X'  oils A  by  finding light  010 f o r s e c t i o n s i - t o a ,  andesine.  G e n e r a l l y zone  Many  of the plagio-  boundaries  are very  39 vague but  and i r r e g u l a r .  commonly  indicated albite the  a r i m o f A n ^ £ and a core  i n about  two-thirds  staurolite  section has  occurs  undulatory  The  One  t o be  cyclic  determination  o f An.^.  Twinning  of the plagioclase  i s simple  and complex i n  only  i t .  plagioclase  thin  section.  clase  grain.  prisms  occurrence  I t also  almandine  i s found  porphyroblast  euhedral,  but marginal  The garnet  occasionally as  inclusions  occurs  I t forms  I t i s pale  i n unusually  The l a r g e s t  be e u h e d r a l  as thesphene  i n this  alteration  pink  and  large grains  or  short,  stubby  to  thin chlorite  inclusions  isotropic. i n this  a r e as b i g as t h e average  extremely  i s not very  found  has a few n o n - o r i e n t e d  and q u a r t z .  w h i c h may Sphene  grains which  and almandine.  i s almost  rounded  as a n h e d r a l  extinction.  Apatite  and  type.  appears  rest.  have  of  of the zoning  i t i s of the reverse  Quartz  in  Some  plagio-  hexagonal  subhedral.  common.  I t h a s t h e same p r o p e r t i e s  i n the other  types  of plagioclase  amphibolite. "Iron chlorite amounts morphous  o r e " forms  and t h e o t h e r as a f e l t y after  mass  biotite  large,  anhedral  minerals. replacing and  grains  Sericite  i s found  plagioclase  chlorite.  replacing i n small  and a l s o  pseudo-  Figure  3.  Photomicrograph of p l a g i o c l a s e hornblende amphibolite. Plain l i g h t X64. C o n t a i n s hornblende, p l a g i o c l a s e and q u a r t z and m i n o r s p h e n e and apatite.  Figure  4.  Photomicrograph of p l a g i o c l a s e hornblende-epidote rock. Plain l i g h t X24. C o a r s e p o r p h y r o b l a s t i c hornblende, f i n e granular e p i d o t e , q u a r t z and plagioclase.  Figure 5. Photomicrograph of plagioclasehornblende- epidote rock. Polarized l i g h t . X64. Same thin section as Figure 4.  Figure 6.  Photomicrograph of plagioclasebiotite-epidote rock. P l a i n l i g h t . X24 Elongate b i o t i t e laths, euhedral to subhedral epidote, plagioclase and quartz.  42  Figure  7.  Photomicrograph of p l a g i o c l a s e biotite-epidote rock. Polari z e d l i g h t . X24. As F i g u r e 6.  Figure  8.  Photomicrograph of p l a g i o c l a s e Biopside-hornblende amphibolite. P l a i n l i g h t . X64. Dark hornblende, lighter diopside, plagioclase, q u a r t z , and m i n o r a p a t i t e and sphene.  43  Figure  9.  Figure  10.  Photomicrograph of plagioclasestaurolite amphibolite. Plain l i g h t . X24. S t a u r o l i t e , hornblende, b i o t i t e , c h l o r i t e , apatite, plagioclase and quartz.  Photomicrograph of plagioclasestaurolite amphibolite. Plain l i g h t . X 2 4 , s i m i l a r to F i g u r e  9.  44 PETROLOGY  OF T H E  Major  METASEDIMENTS  subdivisions  of the metasediments  a r e as  follows:  (1  Plagioclase-quartz-biotite-hornblende gneiss Plagioclase-K feldspar-quartz gneiss Kyanite-staurolite-almandine mica schist Sillimanite-quartz-plagioclase gneiss Graphitic quartz-plagioclase schist Quartzite Quartz-tremolite-zoisite rocks Crystalline limestone Sericite-epidote schist A l b i t i z e d and p o t a s h - e n r i c h e d rocks  (2  (3 (4  (5 (6 (7 (8  (9 (10 It ation  i s realized  that  the divisions i n this  are a r b i t r a r y , but i t i s f e l t  presents  some r e a l  difference  of the rock  petrological  d e s c r i p t i o n o f each  contain  combined  division K  biotite  form  any mappable  type  rock  of  the l a t t e r . rocks  scattered  the extremes types,  areas,  (See t h e s e c t i o n chapter).  rocks  which  do  25 p e r c e n t  of  scale  by  three  and does n o t o f mapping.  of composition  amphibolites,  of the o r i g i n  i n this  than  i . e . the K  detailed  gneiss  I t i s represented  at the present  and p l a g i o c l a s e  a consideration  less  A  follows:  to include  but contain  units  represents  in  morphic  created  from widely  metamorphic  gneisses  o r grade o f  i s justified.  rock  and h o r n b l e n d e .  sections,  apparently  was  feldspar  thin  major  and hence  division re-  Plagioclase-quartz-biotite-hornblende This  not  each  i n composition  metamorphism  (1)  that  classific-  It  o f t h e two  feldspar-bearing  a n d may  and c o n d i t i o n s on t h e o r i g i n  be of  important formation  o f the meta-  45 In hand specimen these rocks have a close resemblance to the plagioclase amphibolites. grained  They are fine-grained to medium  dark grey rocks which appear to almost completely lack  schistosity.  Lineation i s weak or lacking.  Hornblende may be  porphyroblastic. The composition of the three thin sections i s as follows: Thin Section Number 15-3A  Plagioclase (An,«  -  An.,)*  Quartg * Hornblende Biotite Epidote Sericite Sphene Apatite "Iron Ore"  L  18-9  24T4  57%  65%  55%  20% 13% 8% <1% < 1% <1% <1% <1%  15% 15% 5% — <1% <1% <1% <1%  7% 3% 15% 10% < 1% < 1% < 1%  & Determined by measuring N ' or x' 010 for sections -L a x  A  It i s apparent i n thin section that a l l these rocks actually have a f a i r l y strong f o l i a t i o n . l i t t l e else i n common.  Texturally they have  One section has an e s s e n t i a l l y grano-  b l a s t i c texture, modified  by later dynamic metamorphism which  has resulted i n undulatory extinction In the quartz, granul a t i o n of quartz and plagioclase and a series of p a r a l l e l fractures i n the section at a large angle to the o r i g i n a l foliation.  The other sections have porphyroblastic  textures.  Plagioclase i s usually anhedral to subhedral. are of the a l b i t e type (60%-Q5%) or are complex twins. Carlsbad  Twins No  or Carlsbad-albite twins are d e f i n i t e l y i d e n t i f i e d .  46 All is  well  grains  quartz  developed  grains  #15-3A  in  anhedral.  and  Undulatory  i s found  i n two  or  extinction  three  i n #24-4. Hornblende  occurs type  are  as  as  ragged  the  anhedral  occurs  terminations.  biotite  cut  subparallel vermicular  dark  to  brown  straw  Epidote hedral.  It  to  thin  the  It  plates,  section  cleavage The  a  same  amphibolites.  commonly few  with  sections  show t h a t  biotite  when i t  i s the  plagioclase  i s generally euhedral  is colorless  2V,  has  contains  one  quartz.  i s almost  a  i n the  except  i t is  of inter-  is pleochroic  from  yellow.  epidote and  subhedral  i n subhedral  In  grown w i t h  to  porphyroblasts.  common h o r n b l e n d e  Biotite ragged  i s euhedral  always  b i r e f r i n g e n c e of 18  occasionally  associated with  pistacite,  approximately  but  per  biaxial about  cent  of  biotite.  negative  0.03> the  subThe  with  a  indicating  large  i t  13013  HC^Fe-^S  molecule. Sericite granulation. the  Here  plagioclase  these  cross  a  chroic  i n the  i t occurs  and  also  as  a  in a  set  feldspar grain.  It  Sphene granules  i s common  i s found  in a l l thin  ( p a l e brown Apatite  to  as  fine of  narrow  i s rare  colorless) i n small  It  which  felty  wedge-shaped  sections.  occurs  section  is a  mass  has  undergone  replacing  fractures  whenever  i n the  other  crystals  and  very  faintly  sections. rounded  pleo-  type. hexagonal  grains which  are  47 euhedral occurs  or  as  subhedral.  "Iron  large anhedral  (2)  grains.  rocks  of  contains  Hawkesbury  the  sedimentary  rocks  There  have  the  The  "Normal"  gneiss  and  in different  (b)  occur  there.  i n composition  divisions  been  type  the  type  i s the  with  the  upper  plagioclase The  across  Mountain ernmost  to  branch  south the  forms of  except  of  area two  this  The  the  North  band  be  the  meta-  excluding  of  probably  distinct rocks so  of  that  (a)  the  Sidebacon  the  the meta-  differthis  three  "Normal" Lake  subtype,  type.  valley. to  bands;  amphibolites  and  a  south some  part  s l o p e , and  also  small  The  Sidebacon  the  north  of  about  and  Sidebacon  of  7000*  wide  found  the  the  a l l of  part  of  Lake  type  feet  main  island. which  Augen  u n d e r l i e s the  this  3000  one  with  which area  It is also  I t forms  a  i n the  interbedded  band  and  feldspar gneisses  mountain.  Island.  valley  immediately  to  of  are  K  i n the  forms  north  o f Wye  forms, unit  pyrite.  gneisses cent  island,  (c)  valley  Hawkesbury  separate  unknown  type  the  and  forms  and  amphibolite  per  i n the  These  plagioclase  o f Wye  Augen Mountain  extends  the  part  seems  the  #18-9,  in  common p l a g i o c l a s e - K f e l d s p a r - q u a r t z  It  between Augen mountain in  of  erected.  island.  interbedded  largest  i n texture  parts  Augen Mountain  of  only  i s probably  I s l a n d and  amphibolites,  division  It  some 4 0  plagioclase  ences  found  Plagioclase-K feldspar-quartz  This, d i v i s i o n morphic  ore",  the  north-  ridge  is  confined  l a k e , where i t wide  and  the  width. "Normal"  type  Lake  to  type  are  very  other  48 similar type it  and w i l l  i s so d i f f e r e n t  will  (a)  "Normal" In  hand  fine-grained, with  a high  surface  to  and S i d e b a c o n  specimen  t h e same  although  i s much more size  from  band  m a f i c - r i c h bands.  be m a i n l y  minerals.  Where  i t i s developed,  t o form  with  a maximum  an i n c h .  "gneiss"  its  Hawkesbury  Such  weak.  The  sets  than  "leptite",  The term  temperature  i n  lack mica leptynite,  granulite  and hornblende. imply  Island K-feldspar  textural rocks.  of  occasseems and  -  A l l three  sets  bands,  o f about  referred schist"  i s now  other  o r weak.  continuous  been  fol-  weathering  are present  "quartz  granulite  given  but t h i s i s  i s lacking  t e x t u r e have  A  of b i o t i t e  o f bands  rather  weathered  as i s v i s i b l e  alignment  banding  varieties  rock.  and t h e presence  foliation  or  In the f i e l d ,  and q u a r t z - r i c h .  lenses  "granulite",  of the high  variant  grey.  as t h e f r e s h  t o band  of this  i n the past.  teristically  be  medium  but the  due t o d i f f e r e n c e s  three  Gneiss  l e n g t h o f an i n c h o r so and w i d t h  Rocks  "leptynite",  rocks  Mountain  composition  lack of foliation,  Compositional  elongate  of  i n color,  extremely  feldspar-rich,  tend  of  and  are usually  may  due t o t h e p a r a l l e l  platy  mafic-rich,  color  evident  Types  rocks  of mafics  show a c o m p l e t e  present  grain  these  Lake  and w h i t i s h t o p i n k  h a s much  usually  ional  b u t t h e Augen  i n texture, appearance  percentage  s p e c i m e n may  iation  together,  be d e s c r i b e d s e p a r a t e l y .  The  and  be d e s c r i b e d  1/10  t o as and  reserved f o r  facies.  These  The term  leptite,  features lacking  charaand  i n the  The w r i t e r p r e f e r s t o  49 call  these  reserve  rocks  t h e term  gneisses schist  rather than  f o r rocks  schists  with  as he  a well  would  developed  foliation. The K  composition  feldspar-quartz gneiss  mean v a l u e  48 p e r c e n t ;  5 per cent;  quartz  and  less  biotite  Sericite, garnet than  than  may  35  K  of  plagioclase-  t o 54  per cent,  f e l d s p a r 2 t o 20 p e r c e n t , per cent,  mean  1 t o 20 p e r c e n t ,  epidote,  be p r e s e n t ,  allanite,  value  but generally occur  value  28 p e r c e n t ;  mean v a l u e sphene,  mean  8 per cent.  apatite  i n amounts  and of  less  1 per cent. Sidebacon  35  t o 41 p e r c e n t ,  20  per cent,  epidote, minor mainly  poor  i n K  f e l d s p a r 35 less  between  t h e two t y p e s a r e  content.  section,  minerals.  t o form which  i s seen  t o be  due t o a r a t h e r  of biotite  by a replacement  of s i l i c a  Hornblende,  The d i f f e r e n c e s  i s a w e l l developed  liberation  1 t o 2 per cent.  18 t o  and opaques a r e  orientation  and c a l c i u m  quartz  apatite  f o r f e l d s p a r and quartz  formed  plagioclase  t o 42 p e r c e n t ,  than  has developed  to these  have  sphene,  texture, i n thin  sub-parallel however,  gneisses  f e l d s p a r and b i o t i t e  foliation  tendency  type  sericite,  constituents.  sub-parallel  sodium  K  Lake  and b i o t i t e  chlorite,  The  is  type  i s plagioclase  1 0 t o 36  chlorite,  The  A  o f the "Normal"  incomplete  and hornblende,  to occur  complex.  and a  i n elongate  Superimposed  upon  leaves  this,  pseudocataclastic texture  which  of potassium  i n K  f e l d s p a r s by  plagioclase,  with  a  appears  as f r e e  consequent  quartz.  This  50 results quartz  i n a texture and f e l d s p a r  same m i n e r a l s . finer  grains  grains  texture in  physical  may  rocks  with  o f quartz  suggests  be p r e s e n t ,  texture  this  generally  appear  texture  i s mainly  based  types  on m e a s u r i n g  twinned are  i n both  also  grains  X'^  have  present. The  potassium  the "Normal"  is  of the quadrille  at  simple  type  rather  the edges  albite  feldspars  feldspar gneiss.  type,  than  of grains  was  t o have  Such  showing  orthoclase. only.  composition suitable In the grain  not  was  observed  corroded  mareffects  to A ^ Q *  of A n ^  M E D : I  determinations Most  but  i s usually  twinning  U M  are  twins  rare. untwinned  as i s  the twinned  Twinning  '  o f t h e i: -  but complex  a r e present  Whether  texture i s  cataclastic  twinning  that  lamellae  pseudocataclastic.  These  present  twin  have  0 1 0 f o r s e c t i o n s J~ a .  Zoned  in  microcline  of gneiss.  of  Cataclastic  one f e l d s p a r  although minor  i n that  texture.  quartz  P l a g i o c l a s e ' has a c o m p o s i t i o n andesine,  which  usually  only  of the  suggestion  cataclastic  of  of the larger  a suitable chemical  granulated  that,  texture  and bent  i n deciding  however,  i s fractured,  This  grains  by t h e groundmass.  to develop  grains  cataclastic  i s a strong  grains  examined,  the l a r g e r  gins.  there  granulation  properties  sections  xenomorphic  are not fragments  pseudocataclastic  seen which and  from  The d i f f i c u l t y  i n that  develop  thin  i n that  of the larger  feldspars.  present to  o f groundmass  features  large  are set i n a fine-grained matrix  It differs  and a l s o  corrosion  i n which  present feldspar i s  i s usually  the untwinned  K  present  feldspar  51 is  m i c r o c l i n e or  ested If  that  this  o r t h o c l a s e may  i s the  orthoclase. spar  o r t h o c l a s e i s not  case  In  the  is practically  where  in  contact  this  invert  K  Lake  a l l twinned  I t has  been  to m i c r o c l i n e under  untwinned  Sidebacon  with  known.  feldspar is  type  plagioclase,  K  is often  stress.  probably  gneisses  microcline.  sugg-  the  K  feld-  feldspar,  fringed  by-Mlwart-  8 by  myrmekite.  The  optically  continuous  with  like"  the  extent  that  the  myrmekite. Large  extinction.  twin  Biotite ations. unlike  It the  of  the  plagioclase,  primary  l a m e l l a e may  grains This  plagioclase  of  quartz  mineral  occurs  has  no  i s p l e o c h r o i c from common r e d - b r o w n  extend  commonly  i n small  the  other  without  have  brown  biotite  of  even  to  change  into  properties.  ragged  termin-  straw  yellow,  to  the  is  undulatory  unusual  plates with dark  myrmekite  plagioclase  amphibolite. The chlorite,  the  brown  minerals  sericite,  Hornblende of  minor  occurs  Sidebacon type.  sphene,  as  hornblende,  epidote,  apatite,  garnet  and  large  subhedral  grains  in  type  gneisses.  Lake  The  are  epidote  group  It  mineral  is a  as  i t s birefringence varies  from  indicating  16  to  of  occurs out  the  as  rock. 8  Phenomena G.S.A.  small  19  molecular  anhedral In  one  to  thin  per  cent  subhedral section  of  G.H.Anderson,"Granitization, i n the  Bulletin,  Northern vol.  48,  Inyo  1937,  Range pp  of  one  thin  section  is  about  dark  probably  0.026  to  HCa Fe3Si^0]_3. scattered  Sidebacon  Albitization  through-  Lake and  type Related  California-Nevada,  37-39.  0.031 It  2  grains the  opaques.  pleochroic  present  pistacite,  allanite,  52 gneiss  a few c o r e s  pistacite  rim.  of  biotite  in  the case  minor  only in  to  almost  i n most  of the thin  scarce  grains,  (b)  and  weathered  texture. have  Apatite thin  shade  of  pennine,  even  are very inter-  which  Sphene  than  i n tiny Garnet type  euhedral  i n thin  from i st h e  i s present  i n the plagio-  p l e o c h r o i c from  occurs  products  and i s p l e o c h r o i c  but i s rarer  i n small  pale  brown  euhedral and  hexagonal  prisms.  i s found  i n about  gneiss.  I ti s  t o subhedral  section.  s e c t i o n s and c o n s i s t  "Iron  crystals. ores" are  of small  anhedral  magnetite.  specimen  surfaces.  Type  diameter  of  these They  and w e l l d e f i n e d  with  developed  augens.  Gneiss  rocks always  a r e grey have  are oval  o f about  foliation well  blue"  sections.  The p o r p h y r o b l a s t s  a maximum  has " b e r l i n  as s m a l l wedge-shaped  i n a l l thin  hand  Both  properties.  I t i s weakly  The Augen Mountain In  these  by a  g r a i n s , and,  masses.  s e c t i o n s o f "Normal"  pink  probably  as f e l t y  section,  and i s found  i s a pale  i n ragged  extinction,  with  surrounded  are alteration  I t i s probably  and occurs  crystals.  i s found  very  thin  amphibolites.  isotropic It  every  colorless  half  parallel  chlorite  occur  The c h l o r i t e  t o r e d d i s h brown.  subhedral It  They  of the chlorite,  colors,  are present  and s e r i c i t e  and f e l d s p a r .  common  clase  Chlorite  constituents.  ference green  of allanite  a porphyroblastic  (2.5  i s present  Varieties  fresh  f e l d s p a r augens  one i n c h  banding  on b o t h  with  cm).  which A  strong  i n the varieties  small  augens  lack  53 banding  and  stronger bacon  have  than  Lake  that  type  The  comparatively of most  composition  of  the  cent,  f e l d s p a r 15  to  5  cent,  2  to  3  per  Sphene,  15  to  of  the  although  "Normal"  and  Side-  gneisses.  feldspar-quartz gneiss  biotite  foliation,  specimens  clase-K K  weak  per  cent.  20  per  "iron  type  i s p l a g i o c l a s e 30 cent,  epidote  Chlorite  a p a t i t e and  Augen Mountain  and  4  15  to  sericite,  ores"  20  quartz  are  to  per may  always  of  to  50  25  per  cent, be  plagioper cent,  hornblende  present.  present  as  accessory  minerals. In to  be  tent  s e c t i o n , the  essentially by  example (see  thin  of  cataclastic 13  plagioclase  14)  s  augen  twins  also  as  clase of  larger  augen  one  very  i n which  has  a by  No  large  to  is  a minor  i n one  A  seen exgood  thin  g r a i n forming  grains  as  grains  An-^g  section  most  of  a  twinning, were  augens.  to  t o An-^g, m e d i u m  for  A  subhedral  forming  in thin  l a r g e and  albite  of  X* 010  measuring  zoned  groundmass  seen  a  rocks  effects.  i s present  composition  u s u a l l y have  present.  i n the  cataclastic  texture  determined  grains  are  occurs  as  these  is strongly fractured.  Plagioclase andesine,  of  porphyroblastic, modified  p s e u d o c a t a c l a s t i c and  figures  Twinned  texture  although  noted.  The  only  subhedral  complex  Plagioclase  anhedral  s e c t i o n i s composite,  several smaller  sections l a .  grains  and  large plagiobeing  composed  plagioclase  grains. K  feldspar i s a l l of  an  untwinned  type,  either  ortho-  54 clase  or microcline.  I t forms  the largest  rocks  and a l s o  as s m a l l  anhedral  known w h e t h e r in  thin  occurs  t h e augens  section.  They  etching  with  nitrite  solution.  myrmekites K  were  hydrofluoric The K  o f t h e type  identified  acid  grains.  I t i s not  o r n o t as none i n hand  and s t a i n i n g  i n the other  a r e found  specimen  by  i n a sodium  feldspars are fringed  present  i n these  cobalti-  by " w a r t - l i k e "  plagioclase-  feldspar-quartz gneisses. Quartz,  undulatory  i n anhedral  pleochroic  i s found  from  dark  Hornblende biotite.  pleochroic dark  leaves  a n d g r a i n s , commonly h a s  extinction.  Biotite  by  a r e composite  augens  i n large subhedral  brown  forms  green,  of X =  to euhedral  negative pale  i . e . i s t h e common  I ti s  straw.  subhedral  It i s biaxial formula  to  plates.  with  yellow  Y =  aluminous  Z c = A  blue  grains  fringed  2 2 ° , and a green,  hornblende  and Z =  of  this  area. Chlorite minor to  alteration  brown,  colors.  Sphene  (pale most  products.  and has p a r a l l e l  interference  hedral  and s e r i c i t e  brown  Sphene  to colorless)  s e c t i o n s and c o n s i s t  (pyrite?  magnetite?)  i n irregular  The c h l o r i t e extinction  I t i s probably  and a p a t i t e  crystals.  occur  occur  shreds  i s pleochroic  and " b e r l i n  as green  blue"  pennine.  as s m a l l  euhedral  t o sub-  i s t h e common w e a k l y p l e o c h r o i c variety.  "Iron  ores"  o f a few a n h e d r a l  grains.  are scarce i n  t o cubic  euhedral  55  Figure 11.  Photomicrograph of "Normal" type of plagioclase-K feldspar-quartz gneiss. P l a i n l i g h t . X24. Rounded garnets, plagioclase, K feldspar and quartz.  Figure 12.  Photomicrograph of "Normal" type of plagioclase K feldspar-quartz gneiss. Polarized l i g h t X24. As Figure 11.  56  Figure 1 3 .  Photomicrograph of Augen Mountain type of plagioclase-K feldsparquartz gneiss. Plain light X24. Large plagioclase augen containing small epidote grains. Some biotite outside of the augen.  Figure 14.  Photomicrograph of Augen Mountain type of plagioclase-K feldsparquartz gneiss. Polarized light X24. As Figure 1 3 . Fracturing is evident i n t h e augen.  57 (3)  The K y a n i t e - s t a u r o l i t e - a l m a n d i n e mica  These among of  rocks,  t h e most  important  determination  gree,  of the history known  than  tailed  field  mapping  occurs  as a  series  amphibolites valley,  of  Lake  the other  o f bands  on t h e east  of this  shape 100 of  feet this  feet bands  band.  and extent. i n width rock  is  is  mica  lengths  6000 f e e t .  i n a very  of  vary  short  long  from  a  as d e type  plagioclase Beaver  area,  almost  T h e maximum  Most  vary  unit i s  rock  of South  a r e found  bands  de-  series  This  with  of the island.  Some b a n d s  width  out.  the head  schist  of view  This  Lake-Kyanite.Pond  Individual  7000 f e e t  a n d a maximum have  side  zone  rocks.  of the E c s t a l l  carried  from  the point  and, t o a l e s s e r  interbedded  east  i n extent, are  from  facies  units  o f i t was  staurolite-almandine half  o f t h e septum  t h e I c e Cake  the interbedded  limited  o f the metamorphic  extending  through  quite  of metamorphic  better  Ellen  although  schists  width  of the kyanitei n the  southern  considerably i n few f e e t  distance.  to  over  The l o n g e s t  and has an average w i d t h  o f 89  feet.  2000 f e e t  to  to  The t h r e e  5000 f e e t  and  other  band o f 40  major  similar  widths. These pink,  or grey,  constituent fresh  rocks,  when  depending  minerals.  seen  a distance, are white,  on t h e r e l a t i v e  The w e a t h e r e d  surface, but kyanite,  phyroblasts  become p r o m i n e n t  from  them.  around  from  almandine  The m a t r i x  proportions  surface  i s much  and s t a u r o l i t e  as t h e m u s c o v i t e i s normally  of  their  like  the  por-  weathers out  medium  grained  to  58 coarse to  grained.  a parallel  mation  common  weakly  weaker when  larger  are  somewhat  a r e commonly  feldspar,  1^- i n c h e s  Kyanite,  which  crystals  a  inches  of  these  to  the s c h i s t o s i t y  crystals  black  long, which  i n  up  shades  of  inclusions  to the  to large flat a n d 1/2  are orientated with  and a r e s u b - p a r a l l e l  as  diameter. the  acicular  blades  length  to each  quartz,  schistosity.  inch thick. their  garnet  of  inch i n  occurs  flatten-  of which the  prismatic crystals,  of blue,  which  Small  aggregates  t o 1/4  to  diameter.  of this  rule,  l i e parallel  1 i n c h wide,  red subhedral  signs  contain  musco-  which  may  Nearly a l l parallel  other,  pro-  lineation. The  may  long,  rounded  which  few m i l l i m e t e r s l o n g  8  as  as s t u b b y  into  dodecahedrons  no  be-  i s occasionally  2 inches  general  and muscovite  i s varying  be  a  a n d show  to this  i n diameter,  occurs  reach  for-  enough and  to the s c h i s t o s i t y .  are large anhedral  staurolite,  Staurolite  rounded  as deep  due  but t h i s  Banding  bands  euhedral  parallel  are exceptions  to 3 inches  occurs  w h i c h may  and t h e  are large  orientation.  are usually  flattened  striking  ducing  Almandine  crystals  There  largest  this  present  and f e l d s p a r ,  and p l a g i o c l a s e - q u a r t z - r i c h  The  up  of quartz  flakes  the porphyroblasts  porphyroblasts  crystals  i s normally  of muscovite  leaves  developed.  euhedral  schistosity  orientation  enough t o d i s t o r t  vite-rich  most  strong  of elongate  comes m u c h  ing.  A  be  composition  seen  lite-quartz  from  of this  figure  subfacies  l5»  rock  unit  an ACF  o f the almandine  i s extremely  diagram  variable,  f o r the stauro-  amphibolite  facies  to  59  Figure 15.  ACF diagram for the almandine amphibolite facies, s t a u r o l i t e quartz subfacies, showing the range of composition of the Kyanite-staurolite-almandine mica schists.  60 which  the  rocks  in this  unit  with  e q u i l i b r i u m assemblages  belong.  Sample K-l  11-6A  24-7B  55%  46%  15%  31% 23% 10% 15% 15% 5% <1%  —  Plagioclase Quartz Muscovite Kyanite Staurolite Almandine Chlorite  Number  14%  —  3%  —— 25% 5%  30$  5% <1%  <i%  17-6.  PX-3  14%  18% 20% 35%  51% 3% 15% 10% 10% 10% <1%  51% 15%  <i%  10%  < i%  8%  K-2  11-4  50% 4%  —  25% 20% <1%  5% 20% <1%  -—  L e s s t h a n 1 p e r c e n t o f a p a t i t e and o p a q u e s a r e p r e s e n t i n a l l t h i n s e c t i o n s , m i n o r b i o t i t e and s p h e n e a r e p r e s e n t i n a few a n d s i l l i m a n i t e ( ? ) i s p r e s e n t i n one s e c t i o n .  In  thin  s e c t i o n the  strong  noticeable  feature.  Banding  specimen.  An  almost  complete  bands  i s present  and  muscovite  dine  and  veloped in the In  the  staurolite  garnet  are  schistosity, others  shows  there  little  or  one  large  its  formation, until  Other  grains  Kyanite  the  In  indicating i s no no  rotated end  i n this  but  of  have  about  are  of  seen  at of  rotation.  effects,  but  i t s period  and of  then  porphyroblasts  have  few  alman-  angles  Staurolite i n one  thin  section of  undisturbed  (see  whose  growth. usually  f o r most  grown  de-  to  after  rotational  inclusions,  hand  inclusions  garnet  formation  s e c t i o n show o t h e r  The  the  grown u n d i s t u r b e d 80°,  in  quartz-feldspar  varying the  most  to have w e l l  sections  are  rotation  evidence  to  into  i n some s p e c i m e n s .  some t h i n  rotational  i s the  n o t i c e a b l e than  segregation  subparallel  g r a i n seems  again  i s more  porphyroblasts  sieve textures.  schistosity  Figure  18)  effects. orientation  is  evidently  rotational found  crystallographically  affects.  i n thin 20  figures blasts  This  surrounding  i n the section. felty  of f a i r l y  texture  PX-3.  section  a n d 21)  fine-grained rim  Another  controlled,  coarse-grained  rim (see  a l l the staurolite of a broad  outside  no  or m i c r o s t r u c t u r e i s  i s an a l t e r a t i o n  It consists  sericite  a n d show  of which  chlorite.  porphyro-  rim of  I s an  This  fairly  incomplete  Is explained  by  9 Harker when is  as being  staurolite  more  i s altered  soluble  dissolved  due t o t h e i n c r e a s e i n volume w h i c h  and, because  to  the f o l i a t i o n  was  ranging  i t was  A^tj,  first  two d e t e r m i n a t i o n s  index  oils  others is  but quite  Quartz  occurs  of anhedral  usually  has u n d u l a t o r y  P.  350  i ti s  slightly  elongate  grain.  and o c c u r s i n elongate  "leaves".  parallel It also  The c o m p o s i t i o n  of the  ^30'  a r e based  ^ n ^ ,  a  n  d  on m e a s u r i n g  (sodium)  X' 010 A  light  A n  40* N ' x  source  ^  n  e  using and t h e  f o r s e c t i o n s X a.  Zoning  uncommon.  mosaics  9  change,  chlorite  In the sections i n which i t  ^26'  on m e a s u r i n g  The  the staurolite  almandine.  and monochromatic  a r e based  present  from  i s quite variable.  measured  volume  to subhedral  to lens-shaped  in poikiloblastic  plagioclase  from  i s anhedral  and aggregates  occurs  of this  a n d r e d e p o s i t e d away  Plagioclase grains  to s e r i c i t e - c h l o r i t e .  occurs  as elongate  grains with  A. H a r k e r ,  anhedral  sutured  leaves  or as  boundaries.  It  extinction.  Metamorphism,  (Methuen  and C o . L t d .  1950)  62 Muscovite bands  or  occasional isolated  some p l a c e s as  i s coarse-grained  tabular  i t has  and  subhedral  replaced kyanite,  crystals  and  as  generally occurs  as  tabular crystals.  staurolite  fine-grained felty  or  In  plagioclase  masses  of  sericite. Kyanite clusions biaxial  of  i s euhedral  plagioclase,  negative  birefringence,  v/ith  and  two  Staurolite clusions  of  pleochroic in  one  to  pale  and  is  thin  section  of  It  contains  It  is isotropic  golden  has  high  I t has  a  contains It  is  relief,  in-  colorless, moderate  cleavages.  to  and  anhedral.  It  plagioclase.  yellow  to  distinct  the  almandine  and  a  of  almost  contains It  is  in-  commonly  colorless,  but  deep y e l l o w i s h orange  cleavage  pale  power.  It  occurs  muscovite. strong  minerals  phyllite  to  and  It  be as  i s subhedral  quartz, red  is marginally altered  thought  only  opaques.  i s p l e o c h r o i c from  inclusions  mineral  rather  l a r g e 2V, prominent  Sillimanite(?)  and  and  It  and  also  a  parting  untwinned. Most  always  quartz  opaques,  pale  orange.  subhedral.  i s euhedral  quartz, from  a  or  occurs  color  to  sillimanite a  few  mullite,  is visible  acicular  needles  anhedral.  plagioclase. section.  It  #11-4.  The  only  are  under  replacing  colorless,  parallel  description  and  in thin  i n section  i s length-slow,  this  and  rounded  chlorite.  only  b i r e f r i n g e n c e , and with  opaques  to  has  i t i s extremely  biotite  high  extinction.  sillimanite, unlikely  high  relief, The  antho-  that  antho-  63 phyllite of  this  or mullite  occurs  uncommon m i n e r a l altering  dark  brown  Chlorite  fashion or i n a  subhedral  r o c k s , and, where  or chlorite. to  plates.  rock  I t i s an  seen,  i s usually  I t s pleochroic formula i s  straw.  i s found  as i r r e g u l a r  shreds  and f l a k e s .  garnet  (almandine)  i n a l l sections i n which  occurs,  and i s a l s o  found  staurolite  and b i o t i t e .  ence  i n the chlorites  have  parallel  from  medium  "berlin  i n this  as s m a l l  i n these  t o muscovite  generally  mineral  occur  composition. Biotite  replaces  would  There  formed  does  from  or nearly parallel  green  blue"  as an a l t e r a t i o n n o t seem  these  extinction,  to nearly colorless,  interference  colors,  this  product  t o be any  minerals.  It  of  differ-  They a l l  arepleochroic  and have  indicating  anomalous  they  • ,  may b e  pennine. Apatite in the  a r e t h e common  the kyanite-staurolite-almandinemica same  films  a r e common  interlaminated with  euhedral black.  cubic  grains.  The f i l m s  probably  probably  accessory schists.  minerals They  p r o p e r t i e s as i n a l l t h e p r e v i o u s l y d e s c r i b e d Opaques  are  and sphene  i n these muscovite  In reflected  and p o s s i b l y  g r a p h i t e whereas  magnetite.  some  rocks.  They  and as l a r g e light  they  occur  of this  rocks. as  fine  anhedral to a r e always  of the anhedral  the rest  have  grains  material" i s  Figure  16.  F i g u r e 17.  Photomicrograph of k y a n i t e - s t a u r o l i t e almandine mica s c h i s t . Plain light X24. Porphyroblastic a l m a n d i n e (on t h e r i g h t ) and s t a u r o l i t e (on t h e l e f t ) with muscovite l a t h s , quartz, p l a g i o c l a s e and m i n o r opaques and c h l o r i t e (rimming t h e a l m a n d i n e ) Inclusions indicate r o t a t i o n of the garnet.  Photomicrograph of k y a n i t e - s t a u r o l i t e a l m a n d i n e m i c a s c h i s t . P l a i n l i g h t X24. Kyanite porphyroblasts (rectangular cleavage) muscovite l a t h s , quartz, p l a g i o c l a s e , opaques. A s m a l l k y a n i t e g r a i n i n the lower l e f t c o r n e r i s v e i n e d by o p a q u e s .  65  Figure 18. Photomicrograph of kyanitestaurolite-almandine mica schist. Plain l i g h t . X24. Part of a large rotated staucolite porphyroblast.  Figure 19.  Photomicrograph of kyanitestaurolite-almandine mica s c h i s t . P l a i n l i g h t . X24, Twinned (?) rotated(?) s t a u r o l i t e porphyroblast.  66  9  L  I*  wm  *  0  Figure 20. Photomicrograph of Kyanitestaurolite-almandine mica schist. P l a i n l i g h t X24. An a l t e r a t i o n rim of s e r i c i t e and c h l o r i t e surrounding s t a u r o l i t e .  Figure 21.  Photomicrograph of Kyanitestaurolite-almandine mica schist. P l a i n l i g h t X64. Similar to Figure 20.  67  Figure  22.  Photomicrograph of Kyanitestaurolite-almandine mica s c h i s t . P l a i n l i g h t X24. K y a n i t e , staurol i t e , almandine, muscovite, q u a r t z , p l a g i o c l a s e and opaques.  68  (4)  Sillimanite-quartz-plagioclase  This ridge  between  occurs with  as  38  this  rounded  and  3/10  stands  out  This the  wide  of on  rock  an  Valley  and  is a  cent,  the  weathered  apatite  and  foliation  i s seen  which  muscovite  and  The  sillimanite  euhedral have  commonly Quartz  grey,  The  and  by  opaques.  bands  is  resistant  per  1  section  cent,  per  Under to  of  thin  sillimanite  than  i s due  sillimanite  one  36  cent,  less  1/5  variation noted  elongate  i n width,  i n the  a  the  the  15  per  of  sphene,  microscope  the  to  biotite.  found  Biotite  anhedral  sillimanite  f e l d s p a r are  numerous  The bands  small  and  grains  a  strong  acicular These  bands into  muscovite  occur  apparently in i r -  lamellae  gently  i n large anhedral  of  grains.  i s found  biotite are  cent,  s w e l l i n g out  Chlorite  has  orientation  sillimanite  occasionally  sillimanite.  replacing and  of  cent  which  plagioclase  subparallel  small  outcrop.  subhedral  inch  surface.  quartz  per  with  to  generally subparallel.  and  where i t  up  sillimanite  are  bent  the  f i n e - g r a i n e d rock  grains which  shreds  on  interbedded  formed  r e p l a c e d by  regular  F i s h t r a p Bay,  are  "knots"  being  locality  bands  great  large  cent  12  chlorite,  biotite,  pale  i s represented  biotite per  i n one  unknown l e n g t h  of white  following composition: per  of  inch long.  8  in  found  band  knots  muscovite  the  been  amphibolite.  outcrop  conspicuous  has  Angle  foot  plagioclase  across  type  upper  25  a  In  and  rock  gneiss  are  folded.  grains with  a  Figure 24. Photomicrograph of s i l l i m a n i t e quartz-plagioclase gneiss. P l a i n light X24. Fine-grained acicular s i l l i m a n i t e i n "knots" and swirling aggregates with b i o t i t e laths, elongate grains of opaques, plagioclase and quartz.  Figure 25.  Photomicrograph of s i l l i m a n i t e quartz-plagioclase gneiss. Polarized l i g h t X24. As Figure 24.  weak  elongation  ionally  has u n d u l a t o r y The  cation  sub-parallel  complex  flakes. twins  yellow.  Sphene  opaques  consist  (5)  was  Most  X-ray  are of the albite  interbedded  with  i s t h e common w e a k l y o f ragged  although  to  across  extend  brown t o  side  limited  some  the island,  20  The  grains.  schists  i n extent.  They  occur  i n the Trench  Brook  of F i s h t r a p Bay.  a t most  straw  pleochroic variety.  plagioclase amphibolite  locality,  x  type but  large anhedralpyrite  are quite  and on t h e east  N ' for  present.  i s p l e o c h r o i c f r o m medium  rocks  identifi-  as A n ^ by f i n d i n g  Graphitic quartz-plagioclase  These  occas-  methods.  determined twins  are also  Biotite  area  i s so f i n e - g r a i n e d p o s i t i v e  w a s made b y p o w d e r  cleavage  Quartz  extinction.  sillimanite  Plagioclase  to the f o l i a t i o n .  t o 30  a distance  In the former  feet  wide,  of a little  they under  appear 3  miles. In grey  layered  layers have and  hand  rocks  are sharply  great  these  They  are fine-grained, black  or without  distinct,  a strong  of widely  i n thickness  persistent  bedding.  metamorphic  with  variations  are very  relict  specimen  so that  i t seems  do n o t r e s e m b l e  differentiation.  schistosity.  varying  (paper  or dark The  composition,  thin  t o 1/4  likely  they  l a y e r s formed  inch) represent  by  71 The quartz  42  cent,  62  to  tremolite zoisite  composition,  none  none  per  to  less  to  4  per  cent,  none  to  1  per  cent  The  amount  One  hand from  Trench  of  a  feet  Brooks  of  with  sutured  sphene  the and  area.  In  tremolite to  the  of  felty  of  former,  parallel  to  cutting  that  margins across  quartz a  of  to  be  per of 10  of  feet  minerals and  the the  are  quartz  a  cent.  graphite.  wide  rock  in  This  the  i s seen  grains  to  of  latter  to  con-  euhedral  euhedral  to  subhedral  muscovite.  or  Compositional  etc.  the  exception  i s found  preferred  biotite,  The  sub-parallel  Graphite  strong  sub-parallel  frequently  orientated  grains  cent.  per  feldspar grains, with"  quartz,  several.  per  tendency  and  plagioclase.  calcite  plagioclase grains  slight  biotite  per  diopside  15  to  1  g r a p h i t e - r i c h rock  and  zoisite,  6  cent,  20  to  cent,  than  cent,  cent  t r e m o l i t e , the  grains with  of  cent  cent,  per  less  per  per  s e c t i o n the  subhedral  i n the  lath-like  80  most  with  and  quartz  elongate  1  than per  5  to  per 3  to  sphene  occasional small  shreds  sericite  the  thin  micaceous  elongate  the  at  and  containing  and  about  anhedral  diopside  7  1  swelling lens  and  ragged  than  sections, is  30  to  none  cent,  estimated  contains  contacts  subhedral  rimming  is  long  a mosaic  elongation,  or  per  opaques  and  several thin  biotite  apatite less and  pinching  sist  along  1  than  graphite  specimen  100  about  to  cent,  muscovite-sericite less  none  is  per  on  p l a g i o c l a s e 16  cent,  1  to  based  It  within banding  in  orientation occurs one  grain  into  graphite-rich and graphite poor bands i s well developed i n the rocks from the Trench Brooks area but i s lacking i n most specimens from Fishtrap Bay.  Quartz occasionally has undulat-  ory extinction but r a r e l y shows other evidence of s t r a i n . Only two r e l i a b l e determinations could be made on the feldspars.  These are A n ^  a  n  d  -k^^'  t l i e  f  o  r  m  e  determined  r  by measuring N ' for cleavage flakes and the l a t t e r by x  measuring X*  A  010 for a section l a .  Tremolite calcareous  i s the type found i n the quartzites and  quartzites.  It has Z c = 18° - 19°. A  Diopside i s  a colorless variety.  Its maximum interference color i s  second order yellow.  Z c i s at least -38°.  non-ferrian variety.  I t i s b i a x i a l positive with a small 2V  A  and deep blue interference colors.  Z o i s i t e i s the  B i o t i t e i s a variety  which i s pleochroic from reddish brown to straw.  Sphene as  an extremely pleochroic v a r i e t y , from deep red brown to a l most c o l o r l e s s . ary minerals,  C a l c i t e and muscovite-sericite are second-  the former probably replacing plagioclase and  the l a t t e r plagioclase and b i o t i t e . large enhedral grains.  The c a l c i t e i s found i n  The opaques, i n addition to graphite,  consist of euhedral to subhedral cubes of p y r i t e .  73  quartz and p l a g i o c l a s e  F i g u r e 27.  Photomicrograph of g r a p h i t i c quartz-plagioclase s c h i s t . P o l a r i z e d l i g h t X24. As F i g u r e 26.  Figure 28.  Photomicrograph of graphitic quartz plagioclase s c h i s t . P l a i n light X24. C a l c i t e , pyrite, epidote, graphite, plagioclase and quartz. The c a l c i t e , pyrite and epidote are probably secondary  Figure 2 9 .  Photomicrograph of graphitic quartzplagioclase s c h i s t . P l a i n light X64 Diopside, graphite, quartz and plagioclase.  75 (6)  (7)  and  Quartzites rocks  These They  occur  three  thickest lake,  with  localities,  with  (Calcareous  are of limited  interbedded  known  bedded  rocks  has a t o t a l  true  band,  Valley,  h a s a minimum  between  thickness  length  them  eous and  and p r o b a b l y  rich  surface,  bands.  easily  o f metamorphic  clined  to favor  extent white  of the contacts  and r e g u l a r i t y .  by a l t e r n a t e  In the quartzites,  of a mineral  thin  bands  explanation between  The weathered  a 1/4  inch thick layer  white  or  quartz-  minerals the  on t h e b a s i s  of  i s  quartzor a i s  i n -  of the  and t h e i r  surface  calcar-  whitish  i s bedding  t h e bands  occur  bands i n  but the w r i t e r  i n the q u a r t z i t e s , but i n a specimen  quartzite  calcar-  on t h e w e a t h e r e d  between  this  differentiation,  the former  The  In the  t h i c k are prominent  i n paper  o f Exe  impure  appearance.  I t i s n o t known w h e t h e r  result  sharpness  inch  The  are fine-grained  i s marked  due t o t h e s e g r e g a t i o n  which weather rich  t o 1/4  feet.  particularly  types  layers.  feet.  t h e q u a r t z i t e s as they  a banded  banding  greenish  1/8  bands  Both  commonly h a v e  pale  with  interThe  branches  5000  o f about  i n  of Sidebacon  500  o f about  represent  sediments.  quartzites this very  are also  gneisses.  t h e two s o u t h e r n m o s t  with  which  they  feldspar-quartz  quartzites are included  rocks  i n t h e septum.  the plagioclase amphibolites  eous  original  extent  of quartzites, to the north  longest  the  quartzites)  a t one o f w h i c h  plagioclase-K  sequence  and q u a r t z - t r e m o l i t e - z o i s i t e  great  normally  calcareous  of rusty weathering i s  76 present  and  one  due  to a high  pyrite  The  composition  of calcareous  content.  o f t h e two  quartzite  thin  broad  thin  alternate  quartz tacts  25-4  91% 3% 2% <1% 2% — < 1% < 1%  96% 1% 3% < 1% <1% <1%  and  undulatory  subhedral  grains  orientated minerals quartz  grains  Subhedral  in  gation  as  zoisite  or  small  and  follows:  Number  11-1 62% 8% 15% 13% 1% < 1% <1% <1%  grains  grains narrow  or  have  biotite  grains  the rock.  of small  euhedral  plagioclase  grains  grains  of the quartz  grains  to give  generally zoisite  grain  included  sub  size  i n ,  quart-  are  present.  tremolite,  with  sphene  small  and  are p a r t i a l l y parallel  a well  are  these  In the calcareous  wedge-shaped  single  and  of con-  tremolite  A l l of  between,  to anhedral  as  and  bands.  of varying  subhedral  leaves  easily  tBemolite, p l a g i o c l a s e , The  of  sutured  bands,  r e l a t i v e abundance  of quarts  shreds,  occur  Most The  quartzite  i s seen to consist  elongate  to the quartz  throughout  sericitized  bands  a  of sphene.  occur  bands  biotite  heavily  by  sub-parallel  also  sizes.  of b i o t i t e ,  grains  similar  minor  of anhedral  extinction.  aremarked  euhedral  zite  bands  the q u a r t z i t e  of d i f f e r e n t grain  weathered,  and  section  Section  14-4 Quartz Plagioclase Tremolite Zoisite Biotite Muscovite Sphene Apatite  of  w h i c h w e r e made  Thin  In  sections  segregated  to the  developed  elon-  foliation.  77 The  quartz  commonly  The no  suitable  at  least  putting  sections are  indices  are  equal  to  or  range  Twinning  a  to  H Ca Fe^Sig0 2  2 4  Birefringence  blue  ent cc-  this  optic  to  i s the A  yellow. as  highly In  than  albite  in thin could  of  2  and  98  molecular  97  to  or  but  i t is  Its  those  quartz,  of  range  re-  for  type.  section  not  as  method.  w i t h i n the  be  tremolite is negative.  is  definitely Z c  3 molecular  per  cent  19°)  cent  of  biaxial deter-  equals  A  per  and  which  of  R^CagMgj-SigO^  moderate. is biaxial  plane  positive  parallel  to  few  grains  have  with  010,and It  a  a  small  first  2V  of  zoisite,  parting  (about  order  is colorless.  non-ferrian variety  i s p l e o c h r o i c from  Muscovite well  as  i s found  replacing  p l e o c h r o i c from  view  seems  sign  known,  white  It  is  i.e.  parallel,  or  to  appar-  Termier's nearly  001. Biotite  tite  the  greater  the  interference colors.  zoisite.  so,  2V  Michel-Levy  - ^n^,  i s a l l of  i s not  determinations,  a maximum  is  Zoisite  An^Q  is colorless  large  corresponds  deep  for  the  A l l known  the  present of  such  30°),  plagioclase  basis  Tremolite  2  the  the  i t i n the  mined.  of  on  andesine.  with  fractured.  composition  Ano,o  fractive  is  of  the  likely  that  sphene  an  low  as  r e d d i s h brown iron  does  not  brown  alteration  plagioclase  deep  apparent  as  golden  content owe  to  product  sericite. to of  straw  pale these  of  bio-  Sphene  is  brown. rocks  i t s pleochroism  to  i t iron.  Figure  30.  Figure  31.  Photomicrograph of q u a r t z i t e . P o l a r i z e d l i g h t . X24. Strongly developed undulatory e x t i n c t i o n in quartz. A few t r e m o l i t e and z o i s i t e grains are present.  Photomicrograph of quartz-tremol i t e - z o i s i t e rock. P l a i n l i g h t X24. Z o i s i t e , t r e m o l i t e (on t h e r i g h t ) q u a r t z and m i n o r sphene  79 (8)  Crystalline Crystalline  clase side  amphibolite of Evelyn  localities, and  Creek.  interbedded  of Angle  I t s thickness  as i n the former  Valley  folded  i n a creek  with  plagio-  and on t h e e a s t  i s unknown  i t i s much  i t i s exposed  both  localities  medium-grained,  visible This  due  made  calcite.  i n both and  crumpled,  bed t h a t  parallels  present mosaic  massive  narrow  apatite,  ities  i s present  anhedral  calcite.  tremolite  calcite measured  Muscovite  small  too small  only.  One  Calcite  rock  of  of  scattered  may  and o c c u r s  apparently  minerals  impur-  throughout grains  and  and f e l d s p a r a r e be o f  detrital as  i n contact  has a v e r y  a  ragged  subhedral  Quartz  forms  the other  mainly  The t r e m o l i t e i s c o l o r l e s s .  but this  sphene,  o f t h e f e l d s p a r i s unknown  to isolate  thin  i s mainly  o f t h e bands  grains which  i s  a l l of which are  which  i n large  grains.  banding  The one  feldspar,  to consist  coarse  impurities.  occurrence,  (? g r a p h i t e )  euhedral  of  feature.  through  i s found  rounded  bands  1 per cent.  grains.  The c o m p o s i t i o n  untwinned,  grains  o f opaques  A weak  and opaques,  than  and i s found  as minute  as v e r y  origin.  isolated  grains  Valley  are quartz,  i n amounts o f l e s s  i n small  bedding  tremolite,  of large anhedral  rock.  parallel  the Angle  minerals  occur  found  i t i s a whitish to greyish,  an o r i g i n a l  from  Minor  muscovite,  almost  to dark,  i s probably  section  the  occurs  strike. In  to  limestone  a t t h e head  i n the l a t t e r  its  limestone  Z c A  could  low i r o n  i ti s with n o t be content  and this mineral has the same properties, as f a r as can be ascertained, as the nearly pure tremolite of the calcareous quartzites.  Figure 32. Photomicrograph of c r y s t a l l i n e limestone. Plain l i g h t X24. A mosaic of large c a l c i t e grains containing a few small grains of opaques (?graphite), quartz and feldspar.  (9)  Sericite-epidote  The white  to  to  a  strong  to  drag  green  in  always  red  color.  They  drag  folded  areas.  schistosity, folding. Only  one  Island.  This  300  wide,  feet  color, have  This large  shear is  a  have  high are  a  shear at  i n Angle  related  are  depending  on  pyrite  Most  the  content to  to  z o n e was  found  zones  foliation  to due  dimensions  Hawkesbury  long  10,000  about  and  in addition  on  feet  of  weather  microscopic  5000  least  and  shear  secondary  down  silvery  abundance  specimens,  strong  Valley  rocks  generally  confined  persists  zone,  and  schists  They  rusty  intensely a  sericite-epidote  pale  epidote.  schists  and  feet  up  to  from  its  mouth. The indicated  by  composition the  of  this  following  unit  is  Section  2-1 Plagioclase Epidote Biotite Muscovite (Sericite) Quartz Pyrite  plates  which  are  found  The  biotite  Biotite  as  also  are  is  generally  27% 30$ 10% 10% 20% 2%  occurs  as  cores  from  small  6-1X  15% 5% 1% 50% 22% 5%  as  subhedral.  anhedral  pleochroic  as  Numbers  6-1B  ( s e r i c i t e ) occurs  small  variable  table.  Thin  Muscovite  quite  large  subhedral  sub-parallel  Biotite  largely  golden  15% 25% 15% 15% 25% 3%  and  altered  brown  to  plates  chlorite to  muscovite  colorless. which  appear  to  82 be  replacing  with  the  muscovite.  concentrations  usually  of  occurs  clouded  to  for  determination  for  a l l grains  but  lower  or  suggesting  an  as  content  e x a m i n e d , was to  always  small anhedral  alteration.  o f An  equal  are  associated  pyrite.  Plagioclase due  These  that  No  are  than  quartz  anorthite content  sections  present,  higher  of  grains.  between  An^Q  the  for N  i n other  is  suitable  but  that  It  relief, of  0  quartz  orientations, and  An^g  i.e.  andesine. Quartz muscovite The  i s found  grains  former  colorless,  20 it  0.030  of  i s found  occurs  which  per  are  as  inclusions  of  as  anhedral  small  the  schistosity both  Apatite as  and  occurs  small  weakly  p l e o c h r o i c from  pistacite.  l a r g e 2V,  It  and to  sieve  schistosity  and  the  large  part  quartz euhedral  and  thin  18  after  active  as  small  colorless  anhedral  or  brown  texture  contain  and  subhedral  that  to  i t must  have  shearing.  subhedral to  the  section  i t is orientated parallel  t r a n s e c t s i t , so  to  apatite.  cubes  and  pale  bire-  sections  grains with  to  a  about  I n most i n one  is  has  anhedral  i n part  i s found  grains.  but  as  during  granulated  corresponds  muscovite,  In  Sphene  which  between  anhedra,  parallel  grains.  a  leaves  extinction.  HCagFe^Si^O^*  of  i s found  small  variety  with  0.032  biotite,  and  formed  to  of  anhedral  undulatory the  l a r g e ragged  Pyrite  been  have  negative  cent  elongate  elongate  mosaics  i s always  biaxial  molecular  epidote  as  invariably  Epidote  fringence  and  as  hexagonal grains.  colorless.  prisms. It  is  83  Figure 33. Photomicrograph of sericiteepidote schist, Plain light X 2 4 . Folding outlined by muscovite (sericite) laths. Minor biotite, epidote, pyrite, plagioclase and quartz. (10)  Albitized and potash-enriched Rocks  Strong albitization and potash enrichment is very rare on Hawkesbury although myrmekites and augens indicate some metasomatic exchange in most of the plagioclase-quartz-K  feldspar  gneisses.  The o n l y  bedded  with  branch  o f Exe V a l l e y ,  Beaver  Lake  of  quartzite  pluton.  unknown  hand  failed  weak,  scarcely  thin  per cent,  inches  thick  sericite,  texture  t o be  and l e s s  sphene  even weaker form  t o be  material  i ni t ,  has  foliation.  of the rock per cent than  feldspar  1 per cent The  of  thin  material. and t h e  i t does  a mosaic  i s seen  K  and a p a t i t e .  than  orien-  rock  i n t h e hand  lacking  f o r a few o f t h e l a r g e r  sub-parallel  any d i r e c t -  grains  which  have  elongation.  feldspars  present  AnQ4 ( 3 )  The andesine  30  a  micro-  purplish  i s essentially granoblastic  except  plagioclase  quartz  rock with  I t has a  any o f the v e i n - l i k e  The main m i n e r a l s  texture  to the  the composition  white  f o r the biotite  of white  angles  2 per cent  not contain  appears  The  spar.  with the  sub-parallel  The n o r m a l  per cent,  biotite  does  specimen.  (2)  50  chlorite,  The  weak  eight  tint.  due t o a  and a tendency  bands.  section  15  a  flakes  are at large  be p l a g i o c l a s e  ional  inter-  the binocular  for this  foliation  narrow  to  foliation  about  Examination with  visible  into  In  section  found  o f the southernmost  i s a fine-grained  t o show a n y r e a s o n  of which  epidote,  was  to the contact  a band  few i r r e g u l a r v e i n l i k e p a t c h e s  some  side  close  I t forms  tint.  of biotite  segregated a  fairly  specimen  purplish  scope  tation  on t h e east  example  length.  The decided  known  a r e (1)  microcline  (An4o)  occurs  plagioclase  and  (4)  An^Q,  untwinned  as numerous  small,  K  feld-  generally  85 anhedral  grains  myrmekites in  which  lower _La  and i n l a r g e  i t i s being  relief.  for  thin  well  section  scattered  myrmekite.  is  found  noted  above,  kites  of  and forms  gneisses  veinlike  so that  albite  the replacement  local  addition  and K  o f soda  widespread  addition  myrmekites  and augens  quartz  of the  A s i t was  N ' x  not seen  grains  section.  It i s usually  scattered  by e t c h i n g  or  orthoclase,  i n the perthites  v e i n l i k e patches. with  ( i nsmall  Andesine,  grains)  are probably  and p o s s i b l y  to this  a n d myrme-  plagioclase-quartz-K  these  are probably  the K  early.  feldspar  the results  of a  rock,  than the  and soda which  later  resulted  of the plagioclase-K  i nthe  feldspar-  gneisses. Quartz  occurs  as anhedral  grains.  It  hydrofluoric  cobaltinitrite.  and p o t a s h  fringed  throughout the  plagioclase  feldspar  o f most  part  f o r sections  anhedral  i t i s felt  of potash  A  as a few s m a l l  o f the normal  perthites  x' OTO  o f much  i snot  K feldspar  features  feldspar  minerals  of the white  sodium  perthites  to the other  replaces  i n the l a t t e r  untwinned  patches.  grains  part  type  by measuring  either microcline  anhedral  probably  a r e common  feldspar  occurs  forms  identified  these  the thin  and s t a i n i n g w i t h  microcline,  I t was  feldspar,  as s m a l l  identified  acid  The  K  section,  by m e a s u r i n g  its relationship  throughout  twinning, i n  by an untwinned  The a l b i t e  from  Microcline  by  was  relief.  albite  of replacement  identified  fragments  known.  thin  grains  v e i n - l i k e patches.  cleavage  developed  replaced  I t was  and by i t s h i g h  white  in  with well  Large  grains  may  86 have u n d u l a t o r y Epidote It  extinction. i s found  as  i s e i t h e r p i s t a c i t e or  finitely ference  identified.  small  anhedral to  clinozoisite  I t commonly has  but  subhedral  could  "berlin  not  blue"  grains.  be  de-  inter-  colors. Biotite  pleochroic  i s found  as  small  subhedral plates.  f r o m g o l d e n brown t o s t r a w .  It  It  i s commonly  is altered  t o a c h l o r i t e (? p e n n i n e ) w h i c h i s v e r y w e a k l y p l e o c h r o i c g r e e n t o c o l o r l e s s and colors.  Strings  folia  c h l o r i t e are  of  formed f r o m the of b i o t i t e  Figure  34.  to  of  has  deep b l u e anomalous  granular,  weakly p l e o c h r o i c  a l s o secondary a f t e r the  excess  titanium  present  from  interference sphene  between  biotite,  being  a f t e r the  alteration  chlorite.  P h o t o m i c r o g r a p h of a l b i t i z e d r o c k . P o l a r i z e d l i g h t X64. A l a r g e g r a i n of replacement pert h i t e . A n d e s i t e i s b e i n g r e p l a c e d by a l o w e r r e l i e f f e l d s p a r . T w i n n i n g p e r s i s t s i n t h e andes i n e i n the p e r t h i t e ( r e c o g n i z a b l e to the l e f t )  87 A duct  little  sericite  i s present  o f t h e f e l d s p a r s and o f b i o t i t e Apatite  grains  i s found  as v e r y  s c a t t e r e d throughout  (1)  The"meta-igneous The  tent.  They  sills  in  occur  or flows, types  bolite,  i s found  2000  feet  only  50  wide.  t o 100 In  great  just  considerable  with  north  and near the  1/2  hand  variation  crystals  the other  The l a r g e s t  plagioclase  o f these  from  coast  and t h i n  common body,  amphi-  I t i s over  bodies  i s probably  1/8  o f Wye  from  and j u s t  valley,  and  also  o f them a r e very  and l i n e a t i o n of  commonly  o f an i n c h l o n g  of the island  rocks,  orientation  The hornblende  there i s  are either  foliation  b u t i n one s p e c i m e n  branch  Most  and l i n e a t i o n Such  section  o f these  i n composition.  laths.  i n c h wide,  east  into  Lake.  ex-  are probably  are especially  band.  i n texture  i s due t o a s u b p a r a l l e l  hornblende  north  width  specimen  of variation  the east  They  limited  feet.  or absent.  elongate  o f which  of Sidebacon  poorly, developed,  platey  are of very  to the adjacent  Foliation  present  prismatic  section.  or intrusive  amphibolite  porphyroblastic.  is  colorless  most  series.  The average  outcrop,  deal  chlorite.  ROCKS  bodies,  interbedded  conformable  pro-  amphibolites"  as s m a l l  plagioclase  small  amphibolites  of the E c s t a l l  the main  apparently  a  meta-igneous  and  the thin  P E T R O L O G Y OF T H E M E T A - I G N E O U S  rock  as an a l t e r a t i o n  as  elongate occurs i n  t o one i n c h a small  long  pluton  to the north of  i t occurs  i n short  stubby  crystals  about  completely  lacks  metaigneous grained.  lineation  brown  amphibolite  of broad  long  axes  depending or black The  The l a t t e r A  rock  rarer  type  i s essentially granoblastic foliation  platey  similarly  These  across.  and l i n e a t i o n .  due t o a t e n d e n c y  foliation. color,  inch  foliation  I t has a s t r o n g  orientation  their  one q u a r t e r  rocks  hornblende  orientated from  on t h e c o l o r  composition  grains,  and a grains  i n the plane  dark  and  fine-  sub-parallel  of the hornblende  vary  weathered  due t o a  of  green  t o have  of the  to black  of the hornblende,  weaker  i n  and have  a  surface. o f a number  of selected  specimens  follows:  Hornblende Biotite Plagioclase Quartz Epidote  Specimen  Number  6-9B  10-4  14-6  16-9  65$ 4% 30$ 1$ <1$  55% 2% 41$ — <1$  96%  55%  70$  — —  26$ 4$ 12$  29$  3$  Other minerals present include accessory and opaques i n a l l t h i n s e c t i o n s , r u t i l e s e r i c i t e , and diopside i n  2$  Hornblende porphyroblastic one  section  chroic range  i s as  #6-9B,  #16-9.  i s commonly  euhedral  i t occasionally  a few g r a i n s  formula  apatite, i n  and Z c A  follows:  have  show  sphene, minor  to subhedral.  has a s i e v e  twinning  PA-2  on  considerable  texture.  (100).  The  variation.  Where In pleoTheir  89 Sample No.  Z e  Pleochroic formula  A  X PA-2 16-9  24° 23°  23°  10-4 14-6 6-9B  21° 20°  Y  Z  Pale brown very pale yellow  brown pale green  dark brown green  pale yellow  blue green  dark green  This relationship corresponds quite c l o s e l y with the results obtained for the plagioclase amphibolites and other rocks, ex-  #16-9,  which has very pale colors  This hornblende  occurs i n stubby euhedral  cept for the hornblende for a Z c of 23°. A  in  crystals and may be an o r i g i n a l igneous hornblende,  little  affected by metamorphism, which would explain why i t s properties do not f i t into the metamorphic hornblende B i o t i t e occurs i n subhedral f l a k e s . from golden brown to straw. hornblende  series.  It i s pleochroic  It i s commonly found rimming  or i n small flakes cutting through the  hornblende.  Plagioclase i s usually found i n small subhedral to anhedral grains.  In most specimens i t has a composition of  approximately A n ^ to An^ , but i n #6-9B the composition i s 0  An^.  Zoned feldspars are present but not very common.  A  single determination i n #6-9B indicated normal zoning with a core of A n ^ and a rim of A n ^ . Complex twins are quite common. A l l seem to be combinations  of polysynthetic twins.  Quartz occurs i n anhedral grains. Most grains have undulatory extinction. The epidote present i s p i s t a c i t e .  It occurs as small  euhedral  to  subhedral less  to  subhedral  to  anhedral  pale  yellow,  0.03  approximately cent  to  24  per  by  ference  a  formed The  rutile to  and  subhedral  the  to  usually  with  opaque  Rutile,  occurs  are  crystals. present  cubic  mainly  but  euhedral  probably  i n most  as  as  cores.  and It  grains. The  i l m e n i t e and/or  The  i n small  sieve  may  interis  biaxial  -42°. few  minute  of  present cores  i n other  rounded  occur  as  sphene, grains  large  texture, enclosing  i s a weakly  magnetite.  a  per  grains  include apatite,  clusters  opaque  opaques  of  A  18  *  anhedral  a Z c  Sphene  are  of  maximum  small  anhedra,  pleochroic pale  ("elbow") t w i n s ,  Opaques  cen  diopside  small highly birefringent  rare.  color-  feldspar.  present  grains with  Geniculated  ilmenite.  and  A p a t i t e i s found  strings  to  The The  p e r  s e c t i o n s as  of  prismatic crystals.  or  2  yellow.  of  birefringence of  composition  subhedral  l a r g e 2V  a  ® *° ^  is colorless.  minerals  euhedral  a  composed  p l e o c h r o i c from  I t has  a n d  small  alteration  opaques.  be  indicating  order  i s found  plagioclase,  ular  It  accessory  euhedral  as  moderately  by  l a r g e masses  I t may  EC^^Q^^^Pl^  i s second  with  as  colorless.  0.035  occurs  Sericite shreds  or  hornblende.  color  positive  grains.  to  cent  Diopside rimmed  g r a i n s and  as  yellow  twinned rounded  rimmed  type.  by  acic-  on to  sphene  sections are  101,  are  probably  Figure 35.  Photomicrograph of a meta-igneous amphibolite. P l a i n l i g h t . X24 Minerals are hornblende and plagioclase.  Figure 36.  Photomicrograph of meta-igneous amphibolite. P l a i n l i g h t X24. Minerals are hornblende and plagioclase.  92 (2)  Acid  Pegmatites  Pegmatites metamorphism  of  wide  Bay area.  band  pegmatite  pegmatite minor  subhedral less the  noted  folded  K feldspar  grains  and o c c a s i o n a l  greenish  muscovite  composition  i n the Evelyn  small  bands  stringers of  t h e metamorphic  consist  of large  interstitial  biotite  found  OF T H E METAMORPHIC  The  with  i nt h e  and narrower  Other  with  They  involved  o f F i s h t r a p Bay a two-  boudins  folding.  and e r e n u l a t i o n s .  quartz  ORIGIN  forms  been  been noted  On t h e s h o r e  ptygmatic  been  have  b u t have  o f pegmatite  have  have  folds  apparently  a r e n o t common  Lake-Fishtrap foot  which  flakes  i n the later  rocks white  anhedral  or shreds.  i n  colorThey  lack  pegmatites.  ROCKS  of the plagioclase  amphibolites  places  o most  of this  falls the  members  basic  class  of this  do have  considered rock  i n the basic  class  i n the quartzo-feldspathic  basic  they  group  unit.  group  a rather  Turner's  9  The  actually contain high  as r e p r e s e n t i n g  and s e m i - b a s i c  Reactions Press,  37).  (seefigure  class  basic  feldspar a high class  igneous  of Turner. near  i t s boundary  little  content.  includes tuffs  quartz, They  200.  with  although  a r e best  variety of this derivatives of a n d some  W.S. F y f e , F . J . T u r n e r , J . V e r h o o g e n , a n d M e t a m o r p h i c F a c i e s , G.S.A. Mem. 73 p.  1958),  of i t  "quartzo-feldspathic"  alumina  rocks,  Part  tuffaceous  Metamorphic (Waverly  93  Figure  sediments. from  basic  37.  ACF d i a g r a m showing t h e c o m p o s i t i o n a l r a n g e s o f I. K y a n i t e - s t a u r o lite-almandine Mica Schist; II. P l a g i o c l a s e A m p h i b o l i t e ; III. M e t a - i g n e o u s Amphibolite.  Turner  states  igneous  rocks,  that  i n the  amphibolites derived  . . . " h o r n b l e n d e and p l a g i o c l a s e t e n d t o be e q u a l l y a b u n d a n t . ... Q u a r t z a n d b i o t i t e a r e g e n e r a l l y m i n o r m i n e r a l s , t h o u g h t h e y may b e c o n s p i c u o u s i n rocks d e r i v e d from t u f f s . " 10  10 pp.  H;  241-242.  Williams, F.J.Turner,  CM.Gilbert,  Petrography  The  plagioclase 55  about of  60  to  amphibolites per  hornblende.  less  i n the  ages  about  occur,  The  per  least  hundred  relationships. has  within  On  the  tuffaceous posed  of  gneisses  The  They  show n o  thickest of  into  the  where  of  It  small  less  cent  Quartz  or  aver-  of  quartzite schist,  they  of  redeposition.  and  greywackes i n every  form  system  Ecstall  of  thick  note  amphibolite  and  of  quartzite,  forms most  a  of  quartzo-  be  tuffs rocks  the  on,  or com-  products.  ejecta  i s going  i n the  gneiss.  sediments.  are  large part  of Mesozoic  metamorphic  are  sedimentation  that  fall  or  by  Panhandle of  the  series  Tuffs are  probably  of  Devonian  Paleozoic rocks rocks.  over  intrusive  bands  pyroclastic  e r o s i o n and  rocks,  inches  must  sediments  normal  showers  greywacke  quartz-K  graphitic  amphibolites  Tuffaceous  to  with  feldspar-plagioclase  composition  when  few  amphibolites  sub-parallel  quartz-K  is interesting  The  or  per  plagioclase  sedimentation  tuffaceous  found  i s 12  evidence  of  mica  plagioclase  a  normal  Alaska  common.  and  basis  formed  basins  processes  are  band  calcareous  sediments.  be  cent  amphibolites.  i n beds  v o l c a n i c m a t e r i a l and  T h e y may  biotite  g e n e r a l l y have  per  interbedded  feet.  gneiss  indicates  35  locality,  one  kyanite-staurolite-almandine  This  and  plagioclase  limestone,  feldspathic  area  Island the  i t a number  crystalline  map  cent.  feldspar-plagioclase several  of  plagioclase  Hawkesbury  i n at  the  plagioclase  percentage  commoner 8  On  cent  of  extends  and also to  Portland be  the  Canal  from  metamorphosed  mentary  rocks.  correlation or  and  systems The  present  caused  large  be  any  granitic  of  potassium,  amphibolite spars the  distance  from  mainly  are  plagioclase  are  very  lites, biotite the  or  by  In  either  i.e. rence  a  low  may  Alaskan  t o make rocks  sedi-  any  definite  and  any  taken  caused  into  system  by  the  There  i n composition Coast  them.  Any  i s no  sodic  In-  have  does  not  between  additions to  silica.  i n potassium  there  Coast  the  The  and  seem  a  metamorphic  are  usually  plagioclase  sodium.  evidence  not  the  I n t r u s i o n s : : and  d u r i n g metasomatism and  account  effects, i f present,  the  of  No  K  feld-  alteration  of  varieties.  only  i n composition difference  case  the  these  to  being  I t seems most of  contamination  tuffaceous of  and  plagioclase-quartz-biotite-hornblendegneisses  contamination the  near  sodium  and  content.  by  these  from  t o more  similar  the  Alaska, the  Ecstall  not  difference  rocks  i s very  present  The  of  i n composition.  amphibolite,  considerable  the  effects  that  changes  significant  plagioclase  rocks  between  of metasomatic It is felt  to  part  i t i s impossible  d i s c u s s i o n has  trusions. any  of  into  Alaska.  above  possibility  equivalent  However,  at in  Portland Canal  tuffs of  result  likely  by  would or  plagioclase  lower  be some  interbedded  by  a  they  and  were  formed  sedimentary  materials  pyroclastic  material.  tuffaceous similar  with  amphibo-  hornblende  that  normal  sediments  greywacke  rocks  a  the  sediment  rock.  plagioclase  The  occur-  amphibolite  96  and plagioclase-K feldspar-quartz gneiss, which probably were t u f f s or tuffaceous sediments and arkosic or p e l i t i c sediments respectively, supports this view. The mean composition of the various types of plagioclase-K feldspar-quartz gneiss i s as follows:  (1)  "Normal"  type; plagioclase 48 per cent, K-feldspar 5 per cent, quartz 28 per cent and b i o t i t e 8 per cent  (2) Sidebacon Lake type:  plagioclase 38 per cent, K feldspar 39 per cent, quartz 19 per cent and b i o t i t e 1 per cent  (3)  Augen Mountain type:  plagioclase 40 per cent, K feldspar 18 per cent, quartz 23 per cent b i o t i t e 9 per cent, epidote 8 per cent and hornblende 2 per cent. A l l of these rocks belong to the quartzo-feldspathic group and, i f metasomatism has not been important, are d e r i vatives of sandstones and/or of acid igneous rocks.  Inter-  bedding with other rock types and a lack of intrusive r e l a t i o n ships suggests these rocks are probably metamorphosed  sediments.  The "Normal" and Sidebacon Lake types have abundant myrmekites and the Augen Mountain type abundant K feldspar and plagioclase augens.  These features are commonly i n t e r -  preted as being caused by metasomation, i n the former case involving introduction of soda and i n the l a t t e r of potash and soda. It seems probable therefore that metasomatism has, to some extent, changed the composition of these rocks. they have at present such an extremely high s i l i c a and  However alumina  97 content,  and  unlikely  their  somatism. bably  very  iron  present  The  a'high  low  feldspar)  mineral)  Turner's  near  i t s boundary w i t h  The  latter  The  pelitic  this  area  pelitic  rocks  may  class  class the  best  rocks  siltstones, probably  are  composition  strike,  indicates  poor  ing  rock  possibly,  low  to  i t seems meta-  therefore  pro-  semi-pelitic  arkosic  (quartz-  of  sorting  sillimanite  quartzites  sandstones.  The  c o n t a i n over  equivalent  of  two 90  per  Gilbert's  11 H.Williams, (W.H.Freeman and Co.  of  1  the  be  semi-pelitic.  aluminous  sandy The  both  original  sediments  rocks  shales  of or  erratic  along  are  and  across  materials  schists  equivalent chemically.  form-  to  the They  rocks.  s e c t i o n s examined quartz  quartz  and  arenite.  F.J.Turner, p.  1955),  37).  deposition.  rocks  mica  a l l fall  figure  o b v i o u s l y metamorphosed  cent 1  to  content.  rapid  pelitic  thin  (See  semi-pelitic  rocks,  bearing  are  class  metamorphosed  these  schists  quartzo-feldspathic class  The  i n calcium  metamorphosed The  both  an  d e r i v a t i o n s of  kyanite-staurolite-almandine are  or  was i.e.  considered  represent  of  The  the  shales, etc.  changes  and,  or  be  rather  also  rock  pelitic  siltstones  the  type,  solely  kyanite-staurolite-almandine mica  into  of  rock  that  rock.  The  i.e.  alumina  content  i s due  sedimentary  high  (quartz-feldspar-clay  magnesia  composition  original  silica,  and  291.  of  are  these  the  The  quartz rocks  metamorphosed  interbedded  C.M.Gilbert,  and  Petrography  98 much rarer quartz-tremolite-zoisite rocks represent calcareous  sandstones. The c r y s t a l l i n e limestones of the area, on the basis  of their accessory minerals such as tremolite, muscovite, ?graphite, quartz and feldspar, and of textural features, must be sedimentary rather than hydrothermal.  These accessory  minerals represent s i l i c e o u s and argillaceous impurities. The limestone, one occurrence of which i s on a granodiorite contact, i s composed of c a l c i t e rather than of dolomite, indicating a complete lack here of magnesium metasomatism, due to the Coast Intrusions.  This limestone was probably deposited i n a marine  environment as i t contains 97 per cent c a l c i t e .  Fresh-water  deposition of limestone does take place, but fresh water limestone i s usually marly or contains other impurities. The graphitic quartz-plagioclase schists have a general compositional range of quartz 42 to 62 per cent, plagioclase 16 to 30 per cent, graphite 7 to 15 per cent with minor tremo l i t e , b i o t i t e , z o i s i t e , p y r i t e , s e r i c i t e , c a l c i t e , epidote, etc.  One exceptional l e n s - l i k e bed contains 80 per cent or  more of graphite.  This composition indicates a calcareous and  aluminous quartoze rock.  As the graphite i s probably of  organic o r i g i n i t would seem these schists are metamorphosed sediments.  It i s possible the graphite-rich bed represents  metamorphosed coal, which would indicate swampy or shallow water conditions of formation, but this i s very problematical, p a r t i c u l a r l y i n view of the fact that none of the association  99 rocks  have  usually  compositions  found The  the  basis  Most  of  with  resembling  coal  rocks  are  directional  morphosed  coarse-grained  ition  commonly  grained  more  w h i c h may  be  The in  the  Coast of  They  associated  small  origin  of  the  actually  belong  to  the  involved  i n some l a t e r  not  seem  to  so  that  minor  explanation, the  temperature.  evidence  A  thin  true  such  unless  section  (3)  can  cut  some  from  seem  to  be  basic  been  the (1)  rocks  involved  main that  country  that  these  rock  these and  rocks  have  be  a  a  in  does  the  discounted. third  effects  very  plagioclase  been  There  i n the  cataclastic at  during  pegmatites  probably  place  the  period  intrusions  is postulated  i t took  fine-  deformation.  older acid  cause  The  and  injection  of minor  as  compos-  writer believes  Intrusion series  of  meta-  gabbroic  have  are the  or  possibility  probably  rocks,  of  intrusion  period  deformation,  metamorphic  out"  are  Coast  second  would  possibilities  these  older  Later  which  than  "sweated  weakly  flows.  later  the  have  be  masses.  the  are  to  ultrabasic or  on  relationships.  amphibolites  pegmatites  area  classified  appear  the  an  the  underclays  l a c k or  I f as  that  any  and  i s unknown.  venites  be  so  field  stock-like  pyroclastics  (2)  the  originally  or  with  area  of  sills  Intrusions of  metamorphism  rocks  They  include probably  metamorphism  actually  textures.  form  metamorphism, then  are  and  s c h i s t o s e meta-igneous  conformable.  are  coarse-grained  developed  and  amphibolites  texture, composition,  these  of  beds.  meta-igneous  of  that  in  high  amphibolite  sample  taken  right  Bay  occurrence  not  conclusive,  are  venites.  the  island,  beside  shows no  with  suggest  plastic  f l o w and  bolites  there.  It  ces  of  feet  possible  above  sea  i . e . the  more.  No  rocks in  currently  the  700  fusion.  t o 4000  This If  the  composed  with, few  of  pluton  and  obvious  minor  feet  the  thickness  i n at  altitudes  noted  are  the  of  Island  above  sea  300  outor  tops,  the  metamorphic  are  those  the  the  sediments  interbedded volcanics,  than  level  zone  of  formed partial  surmise.  p r o v i d e d by  i s correct,  occurren-  ridge  c o n s i d e r e d as w i l d evidence  on  amphi-  exposed  these  venites,  the  less  above  on  of  these  the w e l l  feet  rocks  field  Ecstall and  series  possibly  i n t r u d e d by  tuffs  a  bodies. the  Ecstall  between  bend  duplication  involved  note  these  is  occurrence  that  immediately  of  Bay  this  elsewhere  to  Hawkesbury  best  noted  fusion  of metamorphosed  present  some 4 3 0 0  were  composition  mainly  igneous  At  feet  analysis and  perhaps,  small  on  not  of  Fishtrap  Although  partial  1000  rocks  i s probably  relationships is  "venites"  i n the  to think that  most  tops, are  exposed  this.  Fishtrap  a l l at  that  i f these  boudins  folding,  possibly  and  ridge  that,  of  writer  the  venites are  possible  suggesting  the  is interesting  level,  crops,  the  ptygmatic:'  associated  of  evidence  i t leads  The  one  least  indicated  the  i n Angle of  may  Valley. the  periods be  rocks  contact with  folding  two  series  of  greatly  have  thickness  the North  Although  map  a  area  there  probably  deformation i n error.  A  so  Mountain is has  that  minimum  no been the  101 thickness seems  o f somewhere b e t w e e n  of the sequence  eous  sediments  ness  of the series  marine  rocks  composition character  bable  of tuffs  feet  and r a p i d  water  o f abundant  rocks,  the great  rocks,  associated with  etc.,  local  suggest  and  pro-  seem t o  This  i s support-  of material of volcanic which  i s not  The v o l c a n i c m a t e r i a l  i . e . an a c t i v e l y  of  i n shallow  sequence  the sedimentation,  deposits.  eugeosyncline,  and  c o n d i t i o n s o f d e p o s i t i o n would  o f l a r g e amounts  rocks  variations  d e p o s i t i o n , presumably  of the sedimentary  thick-  suggests  the lens-shaped  argillic  tuffae-  The  arkosic  deposition i n a geosynclinal basin.  normal marine  or  rocks.  of limestones  arkosic),  of the quartzites,  shallow  origin  a  are truly  by t h e p r e s e n c e  in  The p r e s e n c e  The t h i c k n e s s  indicate ed  and t h e p r e s e n c e  i n the a r g i l l i c  of sorting  water.  i s composed  and a r k o s i c or s e m i - p e l i t i c  deposition.  these  lack  a n d 20,000  reasonable. Most  (if  10,000 f e e t  found  indicates  subsiding geosyncline  with  12 associated the  volcanics.  sedimentary  Quaal R i v e r s a  shallow  stable  environment. based and  mainly  minor  area  water  shelf  rocks  marine  British  shelf  environment  series  facies,  laid  limey  i n the E c s t a l l Island  down  of a thick  represent  i n part  i n an unstable  of a stable shelf  on t h e p r e s e n c e  Lake  to the conclusion that  o f Hawkesbury  but mainly  The concept  interbedded  came  of the E c s t a l l  to the north  Mine S e r i e s and Agnes  British  Padgham  i n a  shelf  environment i s  sequence  of  quartzites  and ? t u f f a c e o u s m a t e r i a l ( t h e Quartzites).  These  have  a  maximum  12 W. P a d g h a m , G e o l o g y o f t h e E c s t a l l - Q u a a l R i v e r s A r e a , C o l u m b i a , ( u n p u b l i s h e d M . A . S c . T h e s i s , U n i v e r s i t y of* Columbia,1958)  pp.189-192  102 thickness  of  quartzites, wards The  on  Douglas  rest  very  of  similar  that  rapidly  mity  of  is  the  between It  younger little  sidence prior  writer  or  and  to  second  no  becoming  rocks,  much l e s s the  the  arkoses  series  or  area  most  there  and  the  unlikely  g e o s y n c l i n a l type  tuffs  Ecstall-  later  particularly  represent or de-  unconforrocks  the  ceasing  is  unstable  rocks  i s an  that  an  would  sediments,  geosynclines  stable areas,  of  tuffs  explanation  became  are  the  i n the  semi-pelitic  Whether  of  likely  s t a b l e and  Island.  although  quartzite series  and  stage.  most  to-  is  quartzites as  there  rapid  sub-  immediately  orogeny.  by  geosyncline time.  Hawkesbury  Ecstall-Quaal Rivers Island  These  out  abundant  stage  evidence  on  thin  are  i s considered the  septum,  appear  quartzite series  than  repetition.  metamorphosed  The  and  the  no  i . e . probably  feels  basin.  Hawkesbury occupied  i n the  originally  first  the  not  Hawkesbury  sediments the  assuming  edge o f do  greywackes, The  of  unknown. are  the  r e g i o n was  tuffaceous posits  sequence  subsiding  deposits  and  amphibolites,  area. this  western  Channel  to  tuffaceous  Quaal  20,000 f e e t ,  the  the  plagioclase or  over  the  Pacific  during  According  Island  to  i s i n the  or western  P a l e o z o i c and  area trough  believed to of  the  possibly early  have  been  Cordilleran Mesozoic  Eardley  "The s e d i m e n t s o f t h e w e s t e r n t r o u g h f r o m C a l i f o r n i a t o A l a s k a a r e c h a r a c t e r i z e d by a l a r g e amount o f v o l c a n i c m a t e r i a l and g r e y w a c k e i n every system. Phyllites, slates, argillites  103 s c h i s t s , g n e i s s e s , r e c r y s t a l l i z e d c h e r t , marble;?, metaconglomerate, meta-andesite and v a r i o u s m e t a m o r p h o s e d p y r o c l a s t i c s m a k e up t h e t h i c k  sequence."13  He  suggests  that  archipelago arc  the volcanic materials  t o t h e west  of the present This  Island bably  view  rocks  Japanese strongly  being  deposited  w h i c h was  came  very  from  similar  a volcanic  to the  island  archipelago. supports  the idea  a eugeosynclinal  i n the Alexander  o f t h e Hawkesbury  sequence.  division  They were  pro-  of the P a c i f i c  14 trough,  which  southern found.  i s believed  Alaska Their  by E a r d l e y  into the region  a g e may  t o have  i nw h i c h  be P a l e o z o i c  these  extended rocks  from  a r e now  or e a r l y Mesozoic.  Dol-  15 mage the  believes  y  basis  these  of strong  known U p p e r  rocks  may  be U p p e r  lithological  Triassic  age which  Triassic  similarities  are widely  i n age on  to rocks  distributed  of along  16 the in  coast  to the south  a much more r e c e n t  site  of deposition  during these  later rocks  (Vancouver work,  during  periods,  formation).  indicates that  the Ordovician  the southern  t h e map  He  however,  area  to Devonian  as f a r as i s known.  are probably  White,  was  but not  indicates  metamorphosed  a  that  extension  of  t h e r o c k s o f t h e Panhandle o f A l a s k a , where t h e O r d o v i c i a n 13 A.J. Eardley, "Paleozoic C o r d i l l e r a n Geosyncline and r e l a t e d o r o g e n y " , J o u r . G e o l . , v o l . p.  55 (1947),  !4  I b i d . . p.  309.  309-310  15 V. Dolmage, " C o a s t and I s l a n d s o f B r i t i s h C o l u m b i a b e t w e e n B u r k e a n d D o u g l a s C h a n n e l s , " G . S . C . Summary R e p o r t s  (1921), p. 25A 16  VJ.H.White,  Columbia",  AAPG B u l l . ,  "Cordilleran Tectonics J a n , 1959,  p.  63.  i n British  104 to  Lower  Devonian  21,000  about cherty  feet,  black  slate,  and  pyroclastics.  THE  GRADE  OF  (1)  have  mainly  stratigraphic  greywacke  limestone,  but with  conglomerate,  thickness of  much  interbedded  andesitic  lava  the writer  will  METAMORPHISM  Metamorphic In  a combined  discussing  use  t h e concept  and  quoted  Facies grade  o f metamorphism  o f metamorphic  facies  as d e f i n e d  by E s k o l a  by T u r n e r , i . e .  "In a d e f i n i t e facies are united rocks which f o r i d e n t i c a l bulk composition e x h i b i t an i d e n t i c a l m i n e r a l c o m p o s i t i o n , b u t w h o s e m i n e r a l composition f o r varying bulk composition varies a c c o r d i n g t o d e f i n i t e laws."17 The Fyfe,  Turner  morphic fication given  classification and Verhoogen  Facies  i n Igneous  fication  Among assemblages  i n Metamorphic  c o n s i d e r a b l y from and M e t a m o r p h i c  I n most  will  used  (Geol. Soc. o f America  differs  Verhoogen.  of facies  also  cases  Reactions 73).  the older  by  and Meta-  This  classi-  classification  P e t r o l o g y by Turner  and classi-  be made.  be r e g a r d e d  amphibolites  as s t a b l e :  plagioclase-epidote-(quartz-biotite)  the following  (1) H o r n b l e n d e - p l a g i o -  clase-epidote-almandine-(quartz-biotite)  morphic p. 9.  given  some r e f e r e n c e t o t h e l a t t e r  the plagioclase  may  Mem.  i s that  (3)  (2)  Hornblende-  Hornblende-plagio-  17 W.S. F y f e , F . J . T u r n e r , I . V e r h o o g e n , M e t a R e a c t i o n s a n d M e t a m o r p h i c F a c i e s , G.S.A. Mem. 73>  105 clase-diopside-quartz. almandine  amphibolite  facies).  The  and  latter  into  If  regarded, the  two  are  first one  belong  to  (formerly part  are  belongs of  The almandine contact  of  the  blages  taining  scarce,  five  Sericite  are  the  their  the  head  stock.  of  and  results  the  reached  of  the  which  Of  two  grade  five,  lack hornblende,  hornblende,  The  these  biotite  staurolite  and  two two  the are have  diopside  not  chlorite, of  rest  exception  that  assem-  slight i t is  Angle V a l l e y near  kyanite-muscovite-quartz part  belong  sillimanite-  A l l the  apparently  sub-  dis-  do  occurrence  or  from.  are  and  section indicating  has  chlorite  assemblage  thin  rocks  the  second  from  Lake  formerly  the  sole  i s from  were  to  minerals.  clase-hornblende  lower  and  late  these  amphibolite  plagioclase amphibolite  third  as  (which  and/or  are  gneisses  sericite  are  by  the  the  sillimanite-almandine  assemblages.  Sidebacon  of  to  s u b - f a c i e s ) , and  s i x t e e n belong  metamorphism  the  lite-quartz  of  the  these  sub-facies  underlain  with  to  generally very  they  sub-facies  sections of  assemblage,  retrogressive obvious  amounts  belong  s t a b l e i n the s t a u r o l i t e - q u a r t z  i s s t a b l e i n the  thin  any  assemblages  staurolite-kyanite  small  two  blage,  which  the  assemblage  facies.  a  facies  kyanite-muscovite-quartz  combined  to  first  A l l these  five  of  the  the  the area  stauro-  subfacies,  non-stable  assem-  plagioclase-biotite assemblages and  one  is a  conplagio-  amphibolite.  plagioclase-biotite  of metamorphism.  The  gneisses  probably  presence  of  indicate  biotite  and  106 andesine  and  l a c k of  conditions. present the  state  highest  thin  i s not  by  o f metamorphism  are  that  from  rocks  of to  or  reached  they  ever  attained.  the  rock  i n the  the  their  i f this, i s Other  areas  staurolite-quartz  subfacies of  the  almandine  hornblende-diopside-biotite bearing  represent  a  facies  the  dyke  these  and/  amphi-  facies. The  One  most  belong  kyanite-muscovite-quartz  bolite  non-equilibrium  r e t r o g r e s s i v e metamorphism,  degree  specimens  indicates  known w h e t h e r  sections indicate  these or  It  hornblende  to  transition  specimen swarm  from  the  and  the  upper  other  Angle  comes  probably  kyanite-muscovIte-quartz  sillimanite-almandine subfacies i s from  rocks,  Valley  from  the  sub-  or v i c e - v e r s a .  near  a  large  edge  of  the  granitic Danva  pluton. The  specimen;  amphibolite,from a  very  ofp l a g i o c l a s e - h o r n b l e n d e - s t a u r o l i t e  South Beaver  interesting  rock  type.  of mineral  assemblage  same  of metamorphism  grade  Valley,  Although  i t probably as  is a  the  r e p r e s e n t a t i v e of  unstable  indicates other  on  the  basis  approximately  amphibolites.  the  Turner  18 and  Verhoogen  note  and  amphiboles,  although  from  widely  separated be  that  a s s o c i a t i o n s of comparatively  localities.  connected  with  the  They  kyanite  rare,  have  suggest  limited  or  staurolite  been  this  recorded  para-  genesis  may  c a p a c i t y f o r Mg  to  replace  Fe  i n almandine  garnets, which,  i n an  MgO  rich  18 Petrology,  F.J.Turner, (McGraw-Hill  J . Verhoogen, Igneous B o o k C o . I n c . , 195D,  and p.  Metamorphic 4-55.  rock,  107 would  result  i n t o o m u c h Mg  present  in  the hornblende  if  a l l t h e A l i s t o be a c c o m o d a t e d .  would ible  result  n o t seem  would  form  all  have  of staurolite  likely  i n a Mg  The  o f much  t o sse how  an i r o n  rich  t o be  o f the almandine,  this  explanation  mineral  amounts  and/or  could  apply  as i t  staurolite  environment. gneisses  hornblende-plagioclase-epidote-  ( q u a r t z - b l o t i t e,)' a n d i n d i c a t e t h e a l m a n d i n e  Small  as  plagioclase-quartz-biotite-hornblende  staurolite-quartz  Mg.  rocks,  such  kyanite  i t poss-  a l l the excess  (and Fe poor)  t h e assemblage  of  o f the A l making  i n one o f t h e s e  rich  accomodated  Crystallization  t o accomodate  i t i s difficult  the formation  does  crystallization  i n the removal  f o r the hornblende  However, to  after  being  amphibolite  kyanite-muscovite-quartz  of sericite  are a result  facies,  subfacies.  of retrogressive  metamorphism. The have  plagioclase-K  gneisses  commonly  t h e assemblage q u a r t z - m i c r o c l i n e - p l a g i o c l a s e - b i o t i t e -  muscovite-epidote, and  feldspar-quartz  which  i s stable  kyanite-muscovite-quartz  bolite  facies.  almandine  would  sillimanite  and a l m a n d i n e .  represented  by these  chlorite,  present  retrogressive The contain  subfacies  The corresponding  subfacies  probably No  rocks.  i n some  i n the staurolite-quartz  rocks  of the  contain  other  Small  o f the almandine  stable  amounts  amphi-  sillimanite-  small  amounts  of  assemblages a r e of sericite  sections, are the results  of  and slight  metamorphism.  kyanite-staurolite-almandine  quartz,  staurolite  and m u s c o v i t e  mica  schists  and u s u a l l y  always contain  plagioclase,  kyanite  it  accompanied  is  always  chlorite  is  morphism.  considered  these  the  by  small  be  a  the  and  other  stable  thin  staurolite  and  almandine  amounts  result  of  of  is  present  chlorite.  This  retrogressive  meta-  however,  only  two  quartz-staurolite-almandine-  plagioclase-quartz-staurolite-kyanite-  r e s p e c t i v e l y , have are  When  chlorite,  assemblages  muscovite-biotite muscovite  almandine.  to  Disregarding  specimens, with  of  and  in  the  sections  equilibrium  assemblages.  Both  staurolite-quartz subfacies.  and/or  almandine.  hand  specimens  According  to  contain  Turner  and  A l l  kyanite,  Verhoogen  " S t a u r o l i t e a p p e a r s t o be s t a b l e o v e r a n a r r o w l y l i m i t e d range of temperature. At the boundary b e t w e e n t h e z o n e s o f s t a u r o l i t e and kyanite, a l m a n d i n e - k y a n i t e becomes a s t a b l e a s s o c i a t i o n at the expense of staurolite."19 3  FeAl Si 0 4  2  l  (OH)  0  2  +  Staurolite  minerals of  a  Any  is stable assemblage  i s presumably  transition  one  from  specimen  tentatively  the  also  identified  actually  sillimanite,  quartz ^  almandine +  19 Petrology,  ^  Fe^Alg  at  a  higher  containing  Kyanite  temperature a l l three  although  of  contains  a  It  few  kyanite  +  the  water  If  of  this  reaction is  so  than these  to  the  interesting to  needles  sillimanite.  i t suggests  is  Water  generally indicative  staurolite-quartz subfacies subfacies.  as  (SiO^+SAlgSiO^+SH^O  Almandine  unstable,  kyanite-muscovite-quartz that  2  Quartz  Kyanite-almandine staurolite.  Si0  slow  a  note  mineral  mineral  is  staurolite+ that  i t . may  F . J . T u r n e r , J . V e r h o o g e n , I g n e o u s and M e t a m o r p h i c ( M c G r a w - H i l l B o o k C o . I n c . , ) 1951, p. 454.  be  incomplete  other dine  possibilities assemblages.  actually  do  apparently The is  other so  form not  the  One a  one of  composition  which  almandine.  If this  stable  of  the  i n the  at  as  least  may one  suggestive  seen  The assemblage  scarce  almost of  i s not  an  a  from  these  and of  22  rocks of  which  would The  figure  one  these  the  schists  and  districts.  two  results  other  a  staurolite  rocks  to  is  composed  subfacies.  23)  and  actually composition  is  extremely  15.  However,  these  three  mi-  another,  which  is  compositional  calcareous  equilibrium  particularly  since  constituents.  almandine The  figures  of  composition  referring  separate  and  other  being  formation  case  minerals  systems.  quartzites  have  the  assemblage  but  does  closely  assemblageq u a r t z - p l a g i o c l a s e - t r e m o l i t e - e p i d o t e  staurolite-quartz the  as  i n contact with  two  two  quartz-plagioclase-tremolite-biotite-zoisite-seri-  the  (zoisite),  (see  are  T h i s , however,  staurolite  i n the  by  There  three  composition  has  and  the  seen  quartzites  This  approach  of  results  place  hardly  the  the  of which  these  evidence  regarded  kyanite  be  are  very  any  staurolite-quartz  nerals  cite.  be  form.  kyanite-staurolite-almandine mica  variable, in  by  were  i s that  assemblage.  i s that  may  to  the s t a u r o l i t e - k y a n i t e - a l m a n -  these  stable  they  formation  be  of  supported  systems,  begins  concerning  possibility  variable  separate in  when s i l l i m a n i t e  and  The  of  biotite  latter  and  sericite  assemblage  the  are  is stable  kyanite-muscovite-quartz  amphibolite  assemblage  both  in  subfacies  facies. graphitic quartzo-feldspathic  110 schists  is  pyrite. be  commonly  Tremolite,  present.  although  None  quartz-plagioclase-graphite-sericitebiotite,  of  the  thin  t h e i r assemblages  almandine  amphibolite  The  epidote,  calcite  sections  are  close  and  diopside  have a  stable  assemblage,  those  stable  in  to  the  facies.  s i l l i m a n i t e - q u a r t z - p l a g i o c l a s e gneiss  assemblage  may  has  the  plagioclase-quartz-biotite-sillimanite-muscovite.  The  stable  is  quartz-microcline-sillimanite-almandine-(plagioclase-biotite)  The  presence  indicates to  reach  assemblage  of  that this  abundant either  grade  ive  metamorphism  are  apparently  the  former The  has  the  sillimanite  muscovite  this  of  being  is  i n the  in  r o c k was  taken  place.  replaced  by  the  plagioclase chlorite  and  presence  of  and  a  higher biotite  shear  that  later  muscovite  sillimanite,  heated retrogress-  and  biotite  suggesting  assemblage  of  the  crystalline is  suggestive  of  a  limestone,  calcite-  non-equilibrium  the  almandine  one  amphi-  facies. The  or  microcline  case.  i s , however, a l s o  bolite  of  sub-facies  sufficiently  or  The  quartz-feldspar-muscovite-tremolite which  place  not  metamorphism,  almandine  zones  sericitic  schists  and  related  rocks,  (andesine)-epidote-biotite-muscovite s i m i l a r assemblages, andesine  indicates  grade  metamorphism,  of  the  greenschist  and  intensely  are  the  drag  and  folded  quartz-  (sericite-  p l a i n l y unstable,  almandine  facies.  with  the  Their areas  as  amphibolite  abundant  facies  sericite  occurrence suggest  the  in  these  rocks  I l l  were formed by retrogressive metamorphism, probably l a r g e l y dynamic i n nature.  The presence of r e l a t i v e l y abundant p y r i t e  suggests the presence of sulphur and possibly iron bearing solutions, although there was probably s u f f i c i e n t iron i n the o r i g i n a l rock to account f o r i t s forming p y r i t e . The meta-igneous amphibolites a l l have assemblages similar to those of the majority of the "plagioclase amphib o l i t e s " and also indicate the staurolite-quartz or kyanitemuscovite-quartz sub-facies. To summarize, the rocks of the E c s t a l l series underlying Hawkesbury Island have,on the whole, reached the almandine amphibolite f a c i e s , staurolite-quartz and/or kyanitemuscovite-quartz  sub-facies. Locally rocks of s l i g h t l y higher  or lower grade exist, but only one specimen belongs to the sillimanite-almandine sub-facies. Widespread minor r e t r o gressive metamorphism has taken place, which may be intense l o c a l l y i n shear zones and strongly drag folded areas. (2)  Temperature-Pressure  Conditions  20 Bowen  has given a series of curves for the s t a b i l i t y  relationships of the various minerals which form during the metamorphism of s i l i c o u s limestone and dolomite.  The assem-  blage c a l c i t e , tremolite and quartz, found i n t h i n section #13-4, i s stable between 100° C and 200° C at 1 atmosphere, 20 N.L.Bowen, "Progressive Metamorphism of S i l i c e o u s Limestone and Dolomite," Jour. Geol. 48 (1940), p. 256.  112 between 475° C and C and  560°  525°  C at  500  atmospheres and between 540°  C at 1800 atmospheres, estimated from these curves.  Increase i n pressure above 1800 atmospheres has l i t t l e on the temperature boundaries of the s t a b i l i t y ?1 F.G. Smith  effect  field.  determined the decrepitation temper-  atures of 23 specimens of almandine garnets and found that their temperature of c r y s t a l l i z a t i o n averaged 607° C and had a t o t a l range of 463° C to  707°  C.  A pressure correction must  be made but Smith feels this i s small.  22  Barth  gives a figure showing the temperature of  formation of equilibrium assemblages containing epidote and plagioclase of various anorthite contents.  On the basis of  his figures the temperature of formation of the rocks i s e q u i l ibrium on Hawkesbury Island ranges from 395° C to 420° C. However, t h i s figure i s based on the assumption that epidote group minerals are unstable above 450° C.  C l i n o z o i s i t e has  been observed forming at 600° C and 12,000 atmospheres and epidote has recently been synthesized at 900° C  so that i t  is obvious his figures must be considerably revised. Turner, Verhoogen and Fyfe place the upper l i m i t of o 24 the greenschist facies at about 400 C and suggest that i f 21 F.G.Smith, "Decrepitation Characteristics of Garnet" American Mineralogist, Vol. 37 (1952), pp. 470-491. 22 T.F.W.Barth, Theoretical Petrology, (John Wiley and Sons, Inc., 1952), p. 285. 23 W.S.Fyfe, F.J.Turner, J . Verhoogen, Metamorphic redactions and Metamorphic Facies, G.S.A. Mem. 73, 1958, pp 165-166 24  Ibid., p. 173  113 this to  i s due  4000  bars  presumably knowledge  and  should  of  on  the  at  of  burial  prevail. higher  stability  that  minerals. f o r the  alone The  load  fields  It  to  of  give  Due  any  to  definite  by  3000  of  amphibolite  hornblende,  is stated  amphibolite  pressures  almandine  temperatures.  i t i s impossible  these  Fyfe  depth  forms  sillimanite based  to  Turner,  a  facies  lack  of  kyanite  and  figures Verhoogen  facies  " i t w o u l d seem t h a t t h e p r e s s u r e - t e m p e r a t u r e field is extensive. The c o m p o s i t i o n o f g a r n e t s , t h e o c c u r r e n c e o f s i l l i m a n i t e and a n d a l u s i t e , and the m a r k e d p r e v a l e n c e o f h y d r o u s m i n e r a l s .... cons t i t u t e strong evidence point to pressures and temperatures lower than those of the g r a n u l i t e facies. Water p r e s s u r e s a r e h i g h enough t o a l l o w hydrated s i l i c a t e s to c r y s t a l l i z e . At constant pressure of water, i n c r e a s i n g temperature alone w i l l l e a d to a t r a n s i t i o n from amphibolite to h o r n b l e n d e - b i o t i t e g r a n u l i t e and e v e n t u a l l y t o pyroxene g r a n u l i t e . At constant temperature, i n the h i g h p r e s s u r e range, a f a l l i n the water pressure might induce t r a n s i t i o n of amphibolite t o g r a n u l i t e , and i n l o w e r p r e s s u r e r e g i o n s t o  pyroxene In  hornsfels."25  connection  with  the  various  sub-facies  they  state  'From t h e m e a g e r p h y s i c a l d a t a a v a i l a b l e i t i s t e n t a t i v e l y conjectured that the s i l l i m a n i t e - a l m a n dine sub-facies corresponds to maximal temperatures i n the a m p h i b o l i t e f a c i e s . From i t s f i e l d r e l a t i o n s h i p s t o the s t a u r o l i t e - k y a n i t e s u b - f a c i e s , i t m i g h t r e a s o n a b l y be i n f e r r e d t h a t l o a d p r e s s u r e s o f t h e t w o a r e a p p r o x i m a t e l y t h e same'.' 20  To almandine pressure  sum  up,  the  p o s s i b l e temperature  amphibolites  i s probably  conditions are  unknown.  25  Turner,  26  Ibid.,  Verhoogen p.  166  and  400° C The  to  range  700+°C  assemblage  Fyfe,  op.  for  in  c i t . , p.  the  and thin  170  114 #13-4  section phosed  600°  a t under The  in  (limestone)  which  above  r o c k was  metamor-  C.  discussion  he c l a i m e d  belonging  suggests this  t o have  t o a number  largely produced  of facies  at  ignores  Yoder s  assemblages  600°  work,  1  C and  supposedly  15000  p s i water  27 pressure find  most  reasons that  THE  facies  CAUSES  OF  The Hawkesbury raised It  also  the of  600°  the amphibolite  C  i s determined  significance  preceeding Island  discussion  sequence,  during  these rocks,  have  the orogeny  deep  Intrusions.  o f metamorphism.  burial,  27  w h i c h was  Ibid.,  p  under  of strong  been  and pyroxene pressure,  petrology.  compressive  carried  seem  seem  which  there  of forces.  t o be  to a great  geosyncline  I t would  the rocks of  conditions  which  or orogenies  disappearance of the P a c i f i c  causes  shown  by t h e water  h a s shown t h a t  were metamorphosed  seems p r o b a b l e t h a t  the Coast  facies  t o metamorphic  temperature and p r o b a b l y  time  he h a s s u c c e s s f u l l y  detailed  METAMORPHISM  eugeosynclinal some  and F y f e  s t a t e m e n t s u n a c c e p t a b l e , and g i v e  between  at  of great  Turner, Verhoogen  but they state  t h e boundary  fact  bars).  o f Yoder's  forthis,  hornfels a  1000  (about  depth at  resulted i n  and t h e f o r m a t i o n a r e two  possible  One o f t h e s e i s t h e a b o v e - m e n t i o n e d presumably  19-20  accompanied  by r a i s e d  tempera-  115 tures  and  thermal by  pressures.  metamorphism  strong  that  the  tization  in  situ  of  regarded  because  character.  these  due  compression  possibility  deals  The  This  to  due  former  i s discussed  igneous  If  the  metamorphism been  (1)  Intrusions  foliation during  writer  for  of  (2)  the  maximum  (3)  of  the  essentially a  which  of  metamorphic  of  such  evidence  metamorphism Such spar  as  of  the  contacts  the  contacts.  of  It  by is  granidis-  intrusive  i n chapter  TV  which  this  area  of  strong  has  lack  seem  occurred  any  their  there near  be  compression any  to  i s compatable  rocks  of  becomes  to  folthe  of  formation  have evidence  thermal  metamorphosed quartz  very  of  Intrusions,  with  i s much more  this  to  marked  the  period  Coast  as  strong  is little  the  fracturing  likely  to  parallel  dynamothermally  and  Intrusions  s e r i e s appear  i n t r u s i o n s and  i s most  Coast  period  during  grade  i s present  i n these  the  depth  i . e . perpendicular  Intrusions  granulation  a  plutons  rocks  previously  i s present  The  obviously  the  not  o r i e n t a t i o n (4)  as  -.  i s a t t r i b u t a b l e to  does  the  d i f f e r e n c e i n metamorphic  and  accompanied  produced at  an  feel  map  compression  Coast  random  not  the  there  elongation  direction dykes  of  to  during  does  granulation  emplacement  tendency iation  or  rocks  fully  i s due  intruded  The  Coast  cause  were  have  more  essentially  rocks.  compression. the  rocks  is  Intrusions,  some o t h e r  metamorphic  the  have  Coast  Intrusions  with  must  possibility  the  to  Coast the  the  other  and  intense  feldnear  weak away  f e a t u r e was  rocks.  from  developed  116 during not  intrusion of a partially  solidified  a t t r i b u t a b l e to compression The  grade  near  only  evidence  the Coast  diopside-bearing Denva  during  a r e (1)  Intrusions  amphibolites  within  Lake  plutons  sillimanite-bearing  rock  some  Lake  samples  close  Other  to the plutons,  blende-biotite bolites, minor the  even  hornblende  bolites  major  period  lower  outcrop within the be  within some  and d i o p s i d e  grade  To positive  feet  from  about  15,000  4,000  feet  as p r o o f  the Sidebacon  from  d u e t o some  as  amphi-  grade  the pluton, are  t h e age r e l a t i o n s h i p between amphi-  i t i s n o t known w h e t h e r  or i s l a t e r  produced  this  during  superimposed mica  the  thermal schists,  of the sillimanite-bearing rocks, feet  of higher  that  almost  the higher  o f the Beaver  of the Sidebacon  there  of a  horn-  around  of sillimanite  summarize,  of the  f e e t , are normal  o f m e t a m o r p h i s m was  equivalents  of  (2) t h e occurrence  The k y a n i t e - s t a u r o l i t e - a l m a n d i n e  evidence  compression  200 t o 300 f e e t  i n the diopside-bearing  so that  one known o u t c r o p regarded  a zone  o f metamorphism  grade  500  so that  Unfortunately  higher  metamorphism. the  form  i s not clear,  localized  13,000  the occurrence  of amphibolite  amphibolites,  i n extent.  and  i . e . about  i f they  emplacement.  o f a d i f f e r e n c e i n metamorphic  and S i d e b a c o n  pluton.  magma i . e . i s  grade  does  the Coast other  Lake  bearing  Valley pluton pluton, rocks  metamorphism  n o t seem  cause, were  that  can hardly near  t o b e -any  Intrusions,  so  and  plutons.  strong  accompanied  responsible  by  f o rthe  metamorphism it  of the E c s t a l l  i s unlikely  metamorphism,  that  they  although  sillimanite-bearing superimposed It the  would  Ecstall  rocks  i n a high  the  Intrusions,  The of  this  of  r e s p o n s i b l e f o r most  feels  of the  may  be  the results  of  later  the metamorphism  have as  high  due  t o deep  temperature  occurred  prior  i f these  were  of the rocks burial  of  these  environment  during  to the i n t r u s i o n older they  of  should  of show  compression.  Coast  orogeny  that  pressure  T h i s must  much e v i d e n c e  The w r i t e r  t h e d i o p s i d e - b e a r i n g a m p h i b o l i t e s (and  i s probably  orogeny. Coast  rocks.  metamorphism.  seem  series  were  rocks?)  thermal  series  I n t r u s i o n s may  or p o s s i b l y  to a  be  related  separate  to a  later  orogeny.  phase  CHAPTER I V  THE  PETROLOGY  OF T H E COAST  The have  rocks  ellite) dykes  are a l l present  granodiorite. common.  margin  In addition  and pegmatites  The  Mountain  North  i s particularly wide  which The  band  grade  into  diorite-quartz  medium-grained  dark  lineation  grey  crystals,  biotite  bolite.  This  i s a  alignment  flakes,  of m a f i c - r i c h rock.  with This  clots  The l a t t e r contaminated  or  part  are  and a r e  of the  o f the Coast  I t consists  monzonite  diorite  The  them.  masses  and q u a r t z  rocks  monzonite  presumably  interesting.  i n outcrop.  to a sub-parallel  than  batholithic  quartz  bodies.  intrude the plutons  intrusion  of diorite  (adam-  f e l d s p a r pegmatites  younger  Island  quartz,,  monzonite  intrusive quartz  quartz-K  definitely  Diorite,  and q u a r t z  are mainly  o f one o f t h e m a j o r  and/or  i n composition.  at least,  4000-foot south  I n t r u s i o n s on Hawkesbury  i n the major  examined  The dykes  Intrusions  due  of the Coast  g r a n o d i o r i t e , monzonite  and s i l l s  part  ROCKS  INTRUSIONS  considerable variation  diorite,  in  IGNEOUS  diorite  of a  to the  to the north.  rocks  are coarse  a pronounced foliation  to  foliation  or lineation i s  of individual  hornblende  of mafics  inclusions  resemble border  and  plagioclase  facies  amphi-  of the batholith.  The  foliation  and  the strike  south,  i s parallel of E c s t a l l  so that  banding  to both series  formed  during  of the E c s t a l l  of  plagioclase  to  the s t r i k e  and, the of  rocks  injection  amphibolite  clots  i n t h e Danva  pluton  i n some p l a c e s , n e a r l y p e r p e n d i c u l a r pluton.  T h e s e must  the plagioclase  granulation a weak  formed  amphibolite  o f these  lineation  have  rocks  of this  inclusions  near  the pluton of  assimilation However, t h e  to their  monzonite  sub-parallel  to the margin  area.  flow  of the  are  by p a r t i a l  sub-parallel  i n the quartz  and  amphibolite  of  crystallized  assimilation  Similar  of the plagioclase  to the  i t i s a result  of a partially  and p a r t i a l  series.  of the batholith  immediately  i t i s n o t known w h e t h e r  magma o r o f g r a n i t i z a t i o n rocks  the margin  seem  c o n t a c t s and  t o be r e s u l t s  of  flow. The is 8  composition  approximately t o 15  per  p e r cent  cent  biotite  chlorite, noted  i n very  centage  may  vary  thin  t o 70  8 t o 20  minor  allanite  apatite,  or subhedral, i n grain  interstitial  plagioclase although  size.  that  i s seen  i s found  to the plagioclase.  5 to  17  opaques,  f e l d s p a r was  tests.  occasionally  Quartz  zircon,  No K  however. than  group  plagioclase,  sphene,  staining  locally  diorite  hornblende,  and s e r i c i t e .  small percentages  section  per cent  per cent  or by u s i n g  be much h i g h e r  greatly  grains  with  section  present  In  per cent  quartz,  epidote,  i n thin  anhedral  50  of the diorite-quartz  I t may  The mafic  per-  recorded commonly  above. t o be  euhedral, as s m a l l  Hornblende  be  and t o anhedral  occurs i n  120 large  generally subhedral  texture. There  Biotite  i s usually  crystals  i s found extensive  some o f w h i c h  as s m a l l  subhedral  have  sieve  platey  granulation of the quartz  grains. and  feldspar. Plagioclase andesine). _La  T h i s was  a n d , i n one c a s e ,  Complex ations  twinning  type  i n rocks  very  green  C a r l s b a d - a l b i t e combin-  i s biaxial  about  - pale  green.  which i s  i s of the reverse  A n ^ a n d t h e r i m An^Q.  negative.  i sX  rare,  The z o n i n g  being  f o r sections  Z c equals A  yellow,  Simple  22°  -  Y - green,  twins  23° and  o n 100 a r e  common.  occasionally  interference The It  the core  t o brownish  Biotite is  nature.  the pleochroic formula  - deep  although  X A 010  (medium  on a C a r l s b a d - a l b i t e t w i n .  feldspars are very  of this  i n one g r a i n  o f An^£ t o An^g  by measuring  by measurements  Zoned  Hornblende and  determined  i s common  are rare.  unusual  Z  has a c o m p o s i t i o n  i s p l e o c h r o i c from altered  colors,  to a chlorite  possibly  commonest  variety  pistacite  and b i a x i a l  occasionally  same c r y s t a l l o g r a p h i c position. colorless. grains.  with  of epidote yellow  negative  enclosed  t o straw.  anomalous  present  a l a r g e 2V.  of allanite  but different  i s p l e o c h r o i c from^deep  These m i n e r a l s  It  deep  blue  occur  i s pistacite.  to colorless,  with  cores  orientation  The a l l a n i t e  brown  pennine.  i s s t r o n g l y p l e o c h r o i c from  birefringent,  dark  as s m a l l  highly The  with the  extinction brown t o  subhedral  or  anhedral  121 Sericite, is  present  clase  as  never  small  zircon  and  acter.  prisms  Sphene  former  shaped  as  colorless,  of  uniaxial  hedral  and  in  rocks.  medium a very  cent  K  cent,  i n most  plagio-  include apatite,  sphene,  subhedral taining the  but  27  or  somewhat  and  as  subhedral  Opaques  crystals  of  pyrite.  of  the  and  to  subhedral  pale  They  North  as  shape,  are  wedge  brown  crystals  found  cubic  i s pink  grains,  squarish are  char-  euhedral  p l e o c h r o i c from subhedral  very  Mountain  anand  are  uncommon  intrusion  in color.  may  averages  39  per  quartz,  cent 1  biotite,  of  It  commonly  epidote,  per  2  to  cent 1  per  allanite,  to  plagioclase, 2  cent  per  cent  chlorite  sericite,  27  and  apatite  opaques.  section  vermicular other  as  character.  cent  cent and  thin  small  foliation.  per  sphene In  latter  composition  per  very  larger  coarse-grained  2  as  occur  monzonite  feldspar,  1  than  zircon,  than  per  length fast  granules  magnetite  weak  hornblende, less  masses  1  than  b i r e f r i n g e n c e and  subhedral  quartz  to  Its per  greater  i s found  are weakly  the  and  mainly  The  low  zircon  positive  grains  these  of  which  and  probably  has  felty  present  Apatite  anhedral  crystals  to  is  and  minerals  opaques.  euhedral  the  flakes  of  grains. Accessory  or  i n amounts  occur  plagioclase  i n myrmekites  quartz.  minerals.  i s commonly  It  as  anhedral  i s commonly  Quartz  euhedral grains  in larger  i s anhedral  and  or con-  grains  interstitial.  122  K  feldspar  fringes small due  i s found  o f myrmekite.  subhedral  t o a weak  blende.  weak  commonly  foliation  a r e common,  Zoning  grid  K  including  Carlsbad  present  twins  were  the texture i s essentially  o f An^Q  t o An^g*  Complex type.  usually  has weakly  i n part  developed  at least.  No  noted. and b i o t i t e  i n the diorite-quartz  replaced  Despite the  a few o f t h e C a r l s b a d - a l b i t e  and so i s m i c r o c l i n e  Hornblende found  and t h e  absent.  feldspar  twinning  horn-  granulation  i s lacking.  has a composition  i s apparently The  as  i s present  and  extinction  with  granular.  Plagioclase twins  lineation  but the extensive  diorite-diorite  grains  a r e found  of biotite  has undulatory  a n d some d e f o r m a t i o n  hypidiomorphic  weak  orientation  be f r a c t u r e d ,  i n the quartz  or anhedral  and hornblende  An extremely  sub-parallel  may  subhedral  Biotite  grains.  Quartz  feldspars common  i n large  by a c h l o r i t e  with  a r e t h e same  diorite. dark  They  purplish  types  as  are both anomalous  those rimmed  and  interference  colors. Apatite, also  t h e same  diorite may  types  rocks.  w h i c h may The  i n these  zircon  as t h o s e  The sphene,  be i n e x t r e m e l y  cores  ing  sphene,  be  large  and t h e opaques  found  i n the diorite-quartz  however,  grains.  present are  i s usually  I t commonly  e u h e d r a l and encloses' opaque  ilmenite.  epidote  group  rocks.  They  minerals consist  are particularly of pistacite  and  interestallanite.  123 The  allanite  of  pistacite,  or  as s e p a r a t e  strongly  may  form  the centre  or occur  as i r r e g u l a r  grains.  Pistacite  birefringent,  a n d may  yellow  always  s t r o n g l y p l e o c h r o i c from may  to colorless,  occur  Sericite the  masses  throughout  fractures  the four  quartz very  hand  thin  narrow  pluton  has a wide  phase,  similar  Mountain  and t h i n  section  almost  to the North  cent  monzonite 55  and l e s s  biotite, zircon mined rather  than  as  grains.  than i n felty  occasionally i n  variation  and opaques.  i n composition.  two a r e m o n z o n i t e ,  t o the quartz  intrusion,is these  rocks  Mountain  K  f e l d s p a r 35  epidote,  each  The p l a g i o c l a s e X'/vOlO  In  both  are texturally  and  i n proportions,  quart  monzonite.  per cent,  sphene,  i s An^  f o r s e c t i o n s i . a.  and no z o n i n g  a  diorite-  present.  of chlorite,  allanite,  one i s  In addition  has the f o l l o w i n g average  1 p e r cent  hornblende,  uncommon  brown.  rocks  but also  f o r a difference  per cent,  by measuring  to light  not only  from  Allanite i s  or euhedral  and one i s g r a n o d i o r i t e .  except  plagioclase  pleochroic  i n these  I t occurs  mineralogically,  The  common  sections studied  of the North  identical  subhedral,  margin  grains.  border  specimen  brown  a  negative,  pleochroic.  the feldspar grains  Danva  monzonite  diorite  diorite.  i n these  The Of  i s much more  dark  and have  i n the p i s t a c i t e  i s biaxial  or weakly  i n anhedral,  diorite-quartz  patches  be i n t e n s e l y  bright  Epidote  of the grain  i s present.  2  composition: quartz  5 per  sericite, apatite,  to A n ^ , Complex  deter-  twins a r e  The q u a r t z  monzon-  124 ite 15  50  has  per cent  per cent  ite.  quartz,  X^OIO  this  is identical  55  per  cent  per cent  rocks.  The p l a g i o c l a s e  The In  outcrop,  is  very  clase, than  als  have the is  An^o?  only  quartz  Lake  section  N ' x  plagio-  quartz  contains  45  less and  group  miner-  granular  with  present a l l monzonite  of  of the plagioclase  f o r cleavage  of the other  and  chlorite,  i n the quartz  similar  and t o t h e  or epidote  i s also  rock  p e r cent  The m i n e r a l s  pluton  this  thin  apatite,  Composition  of rock  examined  40  i n detail.  The o n l y  i s hypidiomorphic  intrusion.  Sidebacon  with  opaques,  of deformation.  on m e a s u r i n g  pluton  per cent  of biotite,  monzonite-monzonite  thin  for a  studied  monzonite.  monzonite  zircon,  seems t o be composed  quartz  25  as t h e above  section,  o f the Danva  The t e x t u r e  Mountain based  by  features  determined  and i n t h i n  t h e same p r o p e r t i e s a s t h o s e North  these  m i c r o c l i n e and  i s An^Q,  m i c r o c l i n e , 20  sphene,  evidence  The It  specimen,  of each  are present.  little  per cent  determined  The g r a n o d i o r i t e  p l u t o n has n o t been  i s quartz  1 per cent No  15  present  intrusion  per cent  sericite.  from  the monzonite.  to the rocks  studied 38  Lake  i n hand  similar  section  Apart  as t h e monzon-  twin.  Beaver  Mountain  of A n ^  a n d t h e same m i n o r m i n e r a l s  Carlsbad-albite  North  with  plagioclase,  quartz  minerals  has a c o m p o s i t i o n  f o r s e c t i o n s X a.  measuring  has  per cent m i c r o c l i n e ,  a n d t h e same m i n o r  Its plagioclase  rock  30  plagioclase,  fragments.  inadequately  studied.  to the granodioritel a r g e masses. p e r cent  The  plagioclase,  125 20 2  per per  m i c r o c l i n e , 25  cent cent  blende, cite.  epidote  apatite, This  The  rock  and  the  deformation The based i s not  zoned.  to  colorless.  The  as  that  North  of  distinct present  yellow  quartz The  similar  to  grained.  hypidiomorphic may  be  partly  of  present these  dykes  chlorite  i s very  of  horn-  and  seri-  close to quartz  the  monzonite.  granular without has  undulatory  fractured  rock  of N >  has for  x  i s not  Mountain  colorless same  and  any  ex-  biotite  a  composition  cleavage  quite  quartz  as  bent,  pleochroism.  of  fragments.  greenish  brown  strongly pleochroic  monzonite  p r o p e r t i e s as  belonging  larger Many  to  bodies, are  granular.  quartz as  be  each  biotite,  but  The  those  does  other i n the  show  minerals North  monzonite.  crystalline to  but  of  i s p l e o c h r o i c from  epidote  the  opaques,  commonly  this  form.  Coast  although  They  commonly  Their  i n the  i s t h a t most  to  be  texture  is  commonly  lack foliation  indicating  same m a j o r  plutons. them  An  very  tend  composition  The  of  Intrusions are  they  Their  probably  monzonite.  those  the  aplites.  strongly granulated,  diorite are  to  dykes the  of  Biotite  a l l have  Mountain  finer  the  cent  cent  minor.  determinations  It  per  per  g r a n o d i o r i t e and  Quartz  quite  5  quartz,  hypidiormorphic  plagioclase on  sphene,  f e l d s p a r s may is  1  than  between  textures.  cent  monzonite  is essentially  tinction  An^  quartz  boundary  directional  but  less  zircon,  is a  composition  and  per  intrusion  ranges and  but  from  minor  in grano-  minerals  interesting  feature  c o n t a i n numerous  inclus-  Figure  38.  Figure  39.  Photomicrograph of quartz d i o r i t e from the N o r t h Mountain intrusion. P l a i n l i g h t X24. The r a g g e d b i o t i t e , h o r n b l e n d e and minor e p i d o t e a r e p r o b a b l y due t o a s s i m i l a t i o n of country rock.  Photomicrograph of quartz d i o r i t e from the N o r t h Mountain intrusion. P o l a r i z e d l i g h t X24. As F i g u r e 29.  127  Figure 40.  Photomicrograph of monzonite from the Danva pluton. Polarized l i g h t X24. Microcline, plagioclase, quartz and myrmekite are present.  Figure 41.  Photomicrograph of granodiorite. P l a i n l i g h t X24. A contaminated dyke containing b i o t i t e , hornblende, epidote and sphene.  128 ions  of country  consequence as  thin  hornblende,  dine,  cases  i n various  s e c t i o n s may  biotite  a l l of which The  some  rock  pegmatites  resisted consist  or pale  of digestion,  be crowded  and e p i d o t e ,  have  biotite  stages  with  such  and i n  minerals  a n d c o n t a i n some  alman-  digestion.  of quartz,  K  f e l d s p a r and i n  greenish muscovite.  Small  euhedral  i garnets' were spar  a r e commonly  feldspar Biotite  ated  from  ORIGIN  NATURE  The ly  places  metamorphic  have  across.  of mica  to the garnets from  rocks  o f Hawkesbury  The boundaries  nearly perpendicular The dykes  and pegmatites  be r e g a r d e d  as e v i d e n c e  quite  xenoliths  sharp  material  to the f o l i a t i o n  cannot  are  deep  o f t h e meta-  of the plutons  and i n t r u d e t h e p l u t o n s ,  rock.  i s a  Island occur  orientation  country  up t o  assimil-  INTRUSIONS  random  the  colorless.  scattered flakes *  The garnet  formed  feld-  The K  g l a s s y and  as " b o o k s "  OF T H E COAST  granitic  rocks.  intergrowths.  as s m a l l  been  and K  rock.  discordant bodies.  some  occurs  i n appearance  the wall  AND  a r e found  I t may  The q u a r t z  and the quartz  and 4 i n c h e s  similar rocks.  i n graphic  white  muscovite  thick  type  morphic  found  and muscovite  inches  red  i n one p e g m a t i t e .  i s usually  Occasionally 2  found  of partial  The boundaries  and n o t d i f f u s e  i n the marginal  parts  are i n  of the  are generally of so t h a t  they  granitization  of the plutons  i n nature.  i n main-  There  of the plutons  and  of  dykes  a r e many  and i n t h e d y k e s .  129 These same  x e n o l i t h s appear rock  apart of  type  from  this  have  a contact The  granitic  depth  Intrusions  and a r e n o t  However, t h e x e n o l i t h s deal  of country  extent.  of the plutons  two m a i n modes  This  rock  with-  assimilation i s  a n d may b e c o n s i d e r e d t o  of origin  of definitely  fusion  currently  intrusive  o f the fused  mation  of a granitic  magma.  The products  magma  of these  be i n d i s t i n g u i s h a b l e .  found  no evidence  views  against  fraction  and w i l l  a r e (1) carried  to  a n d (2) t h e f o r of a  processes  At any r a t e ,  i n t h e map a r e a  the other  rocks  by d i f f e r e n t i a t i o n  of either  favored f o r  character  of previously solidified  and i n t r u s i o n  probably  t h e Coast  features  effect.  rocks  selective  i n situ.  i t t o any great  i n the case  that  as t h e  These  i n character  a s s i m i l a t e d a good  displacing  marginal be  intrusive  orientation  and dykes.  indicate  of granitization  show t h e y out  are truly  t h e same  the plutons  the xenoliths,  area  products  outside  t o have  supporting not discuss  basaltic would  the w r i t e r has one o f t h e s e this  p o i n t any  further.  OTHER  INTRUSIONS (1)  Carbonatized This  at  elevation  rock 390  type  A n d e s i t i c (?) Rocks was n o t e d  feet.  total  known  extent  brook  flows  along  Here  only  i toccurs  o f some l l O f e e t strike  i n West T r e n c h  no o t h e r  as a boudin  by 3 f e e t . boudins  brook,  and has a  Although the  were  noted.  i  In  hand  specimen  this  I  i s a pale  brownish  grey  aphan-  130 itic  rock  weathers  veined to  In  a  minor  No  phenocrysts aggregate  was  seen  Two  or  minor  replaced  are  very  few  and/or  One  with  large  a  fine  Numerous apatite  veins  crystal  vein.  a  (albite?)  twin  lamellae  (oligoclase)  A  occur.  present.  a  alteration  noted.  material also  into  An]_3,  It  plagioclase  calcite  interwoven  i n some l a t h s .  fragments.  by  the  power  of  of  ( g l a s s ? ) and  of  three  consist  f e l d s p a r was  quartz  calcite  to  mainly  material K  plagioclase  grains or  composed  isotropic  fractures.  color.  i t i s found  unidentified  in a The  like  section  quartz  and  calcite-filled  brownish  completely  of  calcite  numerous  groundmass  opaques,  products.  of  pale  thin  fine-grained  by  The  felty,  forms  occurs  as  lath-  non-directional can  composition  determined  It probably  groundmass  of  be  seen  the  by  measuring  at  least  aggregate.  under  high  plagioclase  N '  for  x  9 0 per  cent  is  cleavage of  the  groundmass. The  opaque m a t e r i a l i s found  and a z b h e d r a l cubic  to  be  isotropic  has  I t may  which  perhaps  1  the  per  form  5 per  commonest looks  same  It  as  euhedral  throughout  small  anhedral  grains  with  magnetite. the  rock,  It of  cent. the  relief cent  of  alteration  opaque  very  i s probably  random  m a t e r i a l between  and  The stance  occasionally  s c a t t e r e d at  i t forms The  glass.  and  oroctahedral outlines.  appears which  grains  as  feldspar laths as  balsam.  the  It  is  mainly probably  groundmass.  product  u n d e r medium  is  is a  power  brownish but  sub-  i s seen  to  be  131 transparent rounded  under  grains  high  could  throughout  the section  margins  their  ordinary  light.  phenocrysts, regate first  makes  with  The  shape  been  pyroxenes,  have  a short  few  a r e square The  occurs with,  vein  calcite. grain  On  concordent  than,  grade  and  high  under  cross  basis  rock  than  o f metamorphism  these  type  feldspars. may  have  o f them but a  would  calcite.  Quartz  associated  noted  i s an  elongate  fractures. likely  this  rock  I t seems e s s e n t i a l l y (sill)  or extrusive  i s i n doubt. during  possibility  i s such  during  conditions  they  i n , and  crystal  or introduced  The t h i r d  temperature  agg-  colors of  Most  subhedral  i t seems  or a s i m i l a r rock.  younger  of metamorphism. the  apatite  several  age o f t h i s  to the  or amphiboles?)  masses  a n d may b e a n i n t r u s i v e  The older  lens-shaped  a compos i t iona-^  an andesite  suggests  (pyroxene  i s mainly  The s i n g l e with  along  so (feldspar?).  material  as a few l a r g e  prismatic  was  or nearly  confined  of secondary  and f e l d s p a r s .  outline  along  conspicuous i n  interference  of the phenocrysts  rhombic  I t s presence  quite  be composed  amphiboles,  i n , and  colorless, anisotropic  a n d maximum  I t may  other  i s scattered  common  a l t e r a t i o n product,  i s a fine-grained,  small  and  material  phenocrysts.  the phenocrysts  Another  white.  This  but i s p a r t i c u l a r l y  low r e l i e f  order  i n extremely  birefringence  n o t be d e t e r m i n e d .  of, the altered  margins  I t occurs  and i s so f i n e t h a t  properties  the  power.  that  may  the main  be period  be d i s m i s s e d ,  i t implies  metamorphism. n o t have  I t may  (flow).  deep  Any r ock  the glassy  as  burial  intruded  m a t r i x and  132  F i g u r e 42.  Photomicrograph of (?) a n d e s i t i c rock. P l a i n l i g h t X64. A phenocryst r e p l a c e d by c a l c i t e and rimmed by extremely f i n e grained brownish m a t e r i a l i n a groundmass of f e l d s p a r l a t h s , g l a s s ( ? ) , opaques, e t c . A v e i n of c a l c i t e i s a l s o present.  F i g u r e 43. Photomicrograph of (?) a n d e s i t i c rock. P o l a r i z e d l i g h t X64. S i m i l a r to f i g u r e 42. A small phenocryst i s present i n the upper centre r e p l a c e d by a f i n e grained aggregate of secondary f e l d s p a r ( ? )  133 texture would The  this  retain  rock  the main  later a  shear Due  zones  survived, regional  In  this  bed  and  doubts  case  dykes  Ecstall  series.  I n one  through  granitic  dykes  dykes  are  several dyke  was  quite  were  splits  belonging  that  straight  two  glass  seriously should  of  main  i n some  slickensides  schists,  common i n  have  been  this  rock  could  the  case.  have  through the period  be  i t i s most  of  likely  than this  metamorphism.  a  dyke.  s i l l  abundant  there  locality  noted which into  and  are generally seen  to  may  i s younger  are not  are found here  dyke  metamorphism.  than the  area  rock  or  Dykes:  but  one  this  involved  believes  of necessity  how  enough the  been  assemblage,  the w r i t e r  Island,  dykes  but  sericite  t o whether  which  Lamprophyre Lamprophyre  but  rock  have  of minor  as  i t would  high  presence i n this  i t s present  intrusion  Individual  be  to  (?) i s l a t e r  i t must  The  metamorphism,  (2)  i n this  to see  prior  elsewhere, suggests this  with  i s an  not  I f the andesite  deformation.  to serious  this  probably  o f metamorphism,  graphitic  i f intruded  minerals  recrystallize. period  It is difficult  i t s texture  temperature would  affect  in  has.  of  pinched  o r more  were  to the  i s about  and  cutting  they  only  150  Hawkesbury through the  observed  cutting  Coast  Intrusions.  1  feet  about  fairly and  on  feet  t o 20 wide.  constant  swelled  and  b r a n c h e s w h i c h may  wide,  Most  width, but the  occasional  o r may  not  rejoin. The  lamprophyre  i s dark  green to grey-black  in  color.  It commonly weathers to a rusty brown shade.  It consists of  numerous black hornblende phenocrysts up to 1/3 of an inch i n length set i n an aphanitic groundmass.  The hornblende pheno-  crysts are commonly long, prismatic, rod-like c r y s t a l s , but may be i n part short and stubby.  They commonly make up some  15 per cent to 20 per cent of the rock but may reach 40 per cent. In thin section the hornblende phenocrysts are seen to be embedded i n a groundmass composed of plagioclase laths, smaller hornblende magnetite.  crystals^" and generally subhedral grains of  A few elongate apatite laths are also present.  The magnetite grains may make up as much as 5 per cent of the rock and the plagioclase and a l t e r a t i o n products up to 75 per cent.  Secondary minerals, comprising c a l c i t e , c h l o r i t e ,  epidote and s e r i c i t e , are always presents The hornblende  i s commonly i n euhedral c r y s t a l s .  These are occasionally fractured and cemented by plagioclase or various a l t e r a t i o n products.  The hornblende  i s a deep  brown variety which has well developed rhythmic zoning i n some thin sections.  It commonly has simple twins on (100).  The plagioclase, generally i n euhedral elongate laths, has a composition of An^Q to An^ i n various thin sections, 4  determined by measuring N 'for cleavage flakes. x  Of the secondary minerals; c a l c i t e , epidote and s e r i c i t e are found replacing plagioclase and c h l o r i t e and c a l c i t e occurs replacing hornblende.  These minerals vary greatly i n  135  Figure 44.  Photomicrograph of lamprophyre. P l a i n l i g h t X64. Elongate hornblende phenocrysts i n a groundmass of f e l d s p a r , e p i d o t e , c h l o r i t e , a p a t i t e and opaques.  F i g u r e 45.  Photomicrograph of lamprophyre P l a i n l i g h t X24. Stubby zoned hornblende phenocrysts of v a r i o u s s i z e s i n a groundmass of f e l d s p a r , epidote, apatite, c h l o r i t e , c a l c i t e and opaques.  136 amount,  a t a maximum  section. cases hedral  less.  replacement  pseudomorphs.  Epidote  t h e y may  and i s weakly  pleochroic have  greyish  or  sub-  pleochroic yellow  pale  the usual  that i n  euhedral  or nearly from  of the thin  except  form  i s a faintly  colors, parallel  C a l c i t e and s e r i c i t e  minerals.  anhedral,  C h l o r i t e has anomalous  interference  tinction,  some 4 0 p e r c e n t  are a l l generally  o f complete  pistacite. green  They  comprising  to  greyish  parallel green  ex-  to color-  properties  of  these  CHAPTER  STRUCTURAL  GENERAL  STRUCTURE  The Columbia  part  a general  trend  i s paralleled  which  generally strike  Ecstall 15° a  septum  west  Canal. of  north  However,  t h e septum The  and n o r t h  15°  pendant  has a  general  Channel-Skeena  Hawkesbury  compressive at  right  of the Coast  septum enay  Skeena in  other  pointed  to this  Hawkesbury  Mountains septa  fold  between  and/or 1  1  area  of  and  of  The  north probably  Gardner  the general  geological  i t are reflections  strike  have  reflects  acted  trend.  finds  system, latitude  the effects  o r warp  parallels  system  55°  a n d 57°  N,  features  strong  approximately Ecstall  i n the  and i n warps Range,  a r e a l l convex  W.H.White, " C o r d i l l e r a n T e c t o n i c s A . A . P . G . B u l l . , J a n , 1959 5 p . 6 0 , e t s e q .  trend  i n the Koot-  similar  o f t h e Coast  of  of the  i n a  pendants  s t i l l  to north-west  i n a direction  The bend  Island  These  north  province  of the forces  a f f e c t e d and a r e probably  roof  o u t b y White." '  Mountains  probably  forces which  composite  strike  and south  Island  The g e n e r a l  Mountains  across  Arch  have  region.  angles  River  west.  60° west.  conditions which  the Coast  This  north  and  of  of north.  between  of the structures within  this  British  septa, e t c . ,  and  affecting  west  of  pendants,  across  trend  Intrusions  MOUNTAINS  roof  o f t h e Skeena  i s north  OF T H E COAST  of a l i t t l e  by numerous  or roof  strike  o f the Coast  trend  i n the Douglas  similar  GEOLOGY  OF T H E NORTHERN PART  northern  have  V  as  eastward,  i n British  Columbia"  138 and, according to White "resemble drag folds orientated to conform with a counter-clockwise rotation of the entire cont i n e n t a l margin around the North P a c i f i c basin."  0  MAJOR STRUCTURAL FEATURES OF THE MAP AREA The general trend of the f o l i a t i o n of the E c s t a l l series rocks on Hawkesbury Island i s north 6 0 ° west to north 70° west north of a l i n e running approximately from Backbacon Lake to Evelyn Lake.  South of this l i n e there i s considerable  v a r i a t i o n i n strike and dip but strikes of about north 4 5 ° east are predominant.  There i s a change i n s t r i k e from north  6 0 ° to 70° west to north 4 5 ° east over a narrow t r a n s i t i o n a l zone.  The v a r i a t i o n i n strike probably i s due to folding as  there i s no evidence of major f a u l t i n g and the rocks which have the different trends are very similar i n l i t h o l o g y . In order to determine what deformation or deformations have affected the metamorphic rocks of this area figures 46 to 52 have been constructed.  I f these rocks have been affected  by one period of deformation, the intersections of the planes of f o l i a t i o n , shown i n figures 47 to 51» should have one strong maxima.  The position of this maxima should indicate the  strike and plunge of the fold axes.  A scattering of the points  of intersection and the production of two or more maxima i n dicate that the area has undergone more than one period of deformation.  Examination  of figures 47 to 52 shows that part  of the area, at least, has undergone more than one period of  White, i b i d , p. 60.  deformation. section of  the  the  The  decreases area.  part  as  indicating  in  only  one  effect  strong The  as  of  the  is  north  50°  west  one  that  area, the  strong  period  of  50  formed  of  51  and  during  of  have  been  northern The  although  part  folding.  Most  island.  azimuths  and  plunges  v a r i a b l e , are  of  approximately  of  50°  55°  insufficient  50  north  northwest number  interpretation  of  based  drag  on  also  west  for  of  to  the  drag  major  on  plunge  from  data  the  i n t e r s e c t i o n s of  this  on  pole  strongest  f i g u r e 46,  and  i t i s found  to  maxima  on  this  a  the  sound  and  plotted  of  a  azimuth on  strata  of  great  pass  figure.  This  the  earlier  fold  in  52)  azimuth  and  axes.  planes  circle  through  of  an  west  to  plunge  put  an  any  basis. derived  foliation  i s drawn centre  a  However,  axes of  i t  develop  statistical  major  as  (figure  f o l d s were measured  them  plunge  particularly  folds  fold  steep  traces  55°  north  so  azimuth  could  indicative  When t h e the  the  is  deformation  folded  o b l i t e r a t e d , however, the  the  This  axes  area  deformation.  strong  west.  of  involved  in this  earlier  fold  was  deformation  already  plunging  of  quite  to  steeply  part  interpreted  area  that  last  north  inter-  scattering in  be  indicate that this  55°  north  any  no  can  northern (2)  of  southern  or  which  or  traces  points  i n the  little  deformation  last  period  deformation the  be  i n d i c a t e s r e - f o l d i n g of  u n l i k e l y such  during  to  (1)  of  to  east  map  obliterate  axes  to  the  in figures  fold  probably is  to  maxima  of  period the  s c a t t e r i n g of  appears  either  of  of  from west  There  northern  the  amount  90°  at of  the  indicates that  an  is to  140  azimuth to  65°  northwest  period of  great  intersection second  axes  west  of figure  To  have  resulting  latest)  46  summarize,  55°  axes  circle  t o pass  50°  of the  dominant  The  failure  based  on t h e  through the  i s p r o b a b l y due t o t h e e f f e c t s  the metamorphic  resulting  and plunge  o f 50°  from  have  rocks  two o r more  o f d e f o r m a t i o n have  west  from  correct.  periods of deformation which  The f o l d  period  north  of foliation,  probably undergone  formation.  and plunge  or any o t h e r g r e a t  of planes  o r more  area.  Island  to  55°  north  f o r the fold  circle,  maxima  two  this  west  of deformation i s substantially  this  the  50  of north  affected  o f Hawkesbury  periods of de-  the strongest  an azimuth t o 65°  of  (? and 50  of north  n o r t h west  west  approx-  imately. If ably  the folding  indicates  compression trend ponent  a n o r t h e a s t - s o u t h west  i . e . the d i r e c t i o n  o f the Coast would  i s due t o c o m p r e s s i o n  modify  Intrusions. the picture  alone  direction  indicated  of  prob-  greatest  by t h e g e n e r a l  The p r e s e n c e somewhat.  this  of a shear  com-  141  F i g u r e 46.  P o l e s of F o l i a t i o n o f the M e t a m o r p h i c Rocks o f Hawkesbury Island  142  N  Figure 47.  I n t e r s e c t i o n of the Planes of F o l i a t i o n of the Metamorphic Rocks i n Area I (bounded by the l i m i t of mapping on the south, upper Angle V a l l e y on the e a s t , Ice Cake Lake to Backbacon Lake on the n o r t h and Douglas Channel on the west.)  143  Figure 48.  Intersection of the Planes of F o l i a t i o n of the Metamorphic Rocks i n Area II (bounded by the l i m i t of mapping on the south, Verney Passage on the east, lower Angle Valley on the north, and upper Angle Valley on the west).  144  Figure  49.  I n t e r s e c t i o n of the Planes of F o l i a t i o n of the Metamorphic Rocks i n A r e a I I I (bounded by V e r n e y P a s s a g e on t h e s o u t h , E v e l y n C r e e k on t h e e a s t , E v e l y n Lake to I c e Cake Lake on the n o r t h and l o w e r A n g l e V a l l e y on t h e w e s t . )  145  Figure  50.  I n t e r s e c t i o n of the Planes of F o l i a t i o n of the Metamorphic Rocks i n A r e a IV (bounded by t h e sea on the s o u t h and e a s t , Roy Lake to E v e l y n Lake on the n o r t h , and E v e l y n C r e e k on t h e west).  146  Figure  51.  I n t e r s e c t i o n of the Planes of F o l i a t i o n of the Metamorphic Rocks i n A r e a V ( c o m p r i s i n g a l l the metamorphic rocks n o r t h of areas I to IV i n clusive)  147  N  Figure  52.  The A z i m u t h and P l u n g e o f Drag Folds i n the Metamorphic Rocks of Hawkesbury Island.  148 Owing faults the  and shear  only  1.  to the nature  faults  zones  o f t h e mapping  escaped  seen that  probably  detection.  extend  more  many  small  The f o l l o w i n g a r e  than  a few f e e t :  5000  A shear zone a t l e a s t f e e t long i n lower Angle V a l l e y w i t h a s t r i k e o f n o r t h 50° east, a v e r t i c a l dip and drag f o l d i n g w h i c h i n d i c a t e s an upw a r d a n d s o u t h w a r d movement o f t h e w e s t s i d e o f the shear r e l a t i v e to the east s i d e .  (110°)  2.  A number o f f a u l t s i n t h e v i c i n i t y o f I c e C a k e L a k e , t h e l o n g e s t o f w h i c h i s some feet long, with s t r i k e s varying from north 10° east t o north 40° east and steep d i p s . Most o f t h e s e have d i s p l a c e d the k y a n i t e - s t a u r o l i t e - a l m a n d i n e mica s c h i s t bands a few f e e t . One v e r y l o n g f a u l t w e s t o f I c e C a k e l a k e h a s o f f s e t t h e k y a n i t e b a n d s some h u n d r e d s o f feet. I n a l l cases t h e r e has been l e f t hand separation. A s t h e map u n i t s s o d i s p l a c e d m o v e d have n e a r l y v e r t i c a l d i p s , t h i s p r o b a b l y i n d i c a t e s l e f t l a t e r a l s t r i k e - s l i p movement. Some o f t h e f a u l t s h a v e r e s u l t e d f r o m movement a l o n g t h e a x i a l plane o f l a r g e drag f o l d s which i n v o l v e the whole of the k y a n i t e band.  3.  A s i n g l e f a u l t j u s t t o t h e west w i t h a k n o w n l e n g t h o f some 300 n o r t h 50° w e s t , d i p s v e r t i c a l l y amount o f v e r t i c a l movement, a s slickensides.  4.  A shear zone, and/or f a u l t zone i n and near West T r e n c h B r o o k w i t h a k n o w n l e n g t h o f some 4 0 0 0 f e e t . T h i s s t r i k e s n o r t h 60o west and d i p s v e r y s t e e p l y . S l i c k e n s i d e s i n d i c a t e v e r t i c a l movement.  5.  A f a u l t o r n a r r o w s h e a r z o n e o f unknown l e n g t h ( g r e a t e r t h a n 200 f e e t ) c u t t i n g t h e N o r t h M o u n t a i n q u a r t z m o n z o n i t e a t e l e v a t i o n 600 f e e t above Gaudin P o i n t . T h i s has a s t r i k e o f due n o r t h , a  5000  dip The and  strike  west  stress  30° between  axis  and a n unknown  direction  and d i p o f t h e A n g l e V a l l e y  the Ice-Cake Lake  mediate of  o f 85°  o f t h e above s e r i e s feet. This strikes a n d h a d a n unknown i n d i c a t e d by  area  was  faults  nearly  the direction  shear  indicates that  vertical.  of faulting  o f movement.  the  Assuming  an  or shearing  zone interangle and t h e  greatest  stress  sinistral, during 20  o  these  maximum  20  s t r e s s may  be  i n strike  inhomogeneous The ) have  parallel morphic  rocks.  east. less  or nearly  As  these  of minor  varied  pattern.  may  be  along  period north  due  part  simply  60°  west  to the  rocks  stress  and  planes occur  foliation  considerably to  close  seem  this to  vertical  to f i t the  perhaps simply  foliation  meta-  t o some d e g r e e  fairly not  and  are  i n the  on  parallel  do  ( (3)  faults  movement  although  may  of the  be  the  planes.  STRUCTURES  Small-scale rocks  rocks  structural features  include  schistosity  segregation  cataclastic  textures.  a  involved.  probably  faults  They  is  between  i s i n d i c a t e d , as  of these  In the metamorphic  folds,  during  environment, i s probably  These  slippage  noted  v a r i a t i o n i n d i r e c t i o n of  vertical  faults  the weakness  regional  (1)  formed  stress  to north  d i r e c t i o n of greatest  SMALL-SCALE  iation,  than  been  of the rocks  west  i n d i c a t e d , however.  drag  The  of the f a u l t s  of the stress  by A  overall  of  o  the d i r e c t i o n of f a u l t i n g ,  plane.  morphic  have  or s u b - p a r a l l e l to the f o l i a t i o n  modified  result  a l l t h e movement  of greatest  50°  north  that  would  character  vertical  indicative  is  faults  north  and  variation  planes  and  which the axis  west  (4)  axis,  or  foliation,  banding, minor  structures,  and  observed  i n the  meta-  lineation,  crenulations  of  pseudocataclastic  folstructures  150 Segregation pseudocataclastic and  will  developed notable  foliation,  parallel  localities ease  of this  very  prominent  previously  series  have  a  well  p r e v i o u s l y mentioned. i s that  sedimentary  the latter  was n o t e d  discussed  of the E c s t a l l  foliation  to relict  i n which  been  s t r u c t u r e s and  further.  as has been  of recrystallization  Lineation is  of the rocks  feature  cataclastic  s t r u c t u r e s have  n o t be c o n s i d e r e d Most  nearly  banding,  was  parallel  i n a few p l a c e s  A  i ti s parallel  bedding  seen.  or  i n a l lthe  This  may  to original  be due t o  bedding.  In the amphibolites  In the kyanite-staurolite-almandine  and  mica  IS  schists.  The l i n e a t i o n  i n the amphibolites expressed  alignment  of hornblende  prisms  It  was n o t e d  i n specimens  amphibolites, very one  especially  coarse-grained with  East  within  dips  steeply north.  almandine of  elongate  from  the Evelyn  plane  kyanite  that  i s expressed  crystals.  of  This  foliation.  coarse-grained Lake  area.  h a s two d i s t i n c t  The l i n e a t i o n  schists  the plane  of particularly  d i p and t h e other  a foliation  mica  within  amphibolite  a vertical  by an  A  with  strikes  One  lineations,  a d i p o f about north  65°  50°  west and  i n the kyanite-stauroliteby a p a r a l l e l lineation  alignment  i s generally  about h o r i z o n t a l . Drag the  folds  and minor  crenulations  a t t i t u d e s o f a number w e r e m e a s u r e d .  outcrops  were  flat  tained,  so t h a t  plotted  accurately  and no good  only  idea  49 r e a d i n g s  a r e common a n d Unfortunately  o f plunge  could  w e r e made w h i c h  on t h e s t e r e o - n e t .  The great  many  be ob-  could  be  variation  151 in  azimuth  usually given also  and plunge  one o r two d i r e c t i o n s o f m a j o r  exposure, occur.  great  but smaller  o f the major  azimuths  o f south  westerly  plunges.  have moved  (2)  east  85°  west  This  The igneous Of  the area  eation.  Weak l i n e a t i o n s  North Mountain  alignment clots  foliation from  previously crystalline series the  70°  Ecstall  intrusion.  were  noted  north may  steep to the north  south.  examined,  only  foliation i n other  the North  and/or  50°  west  diorite  to vertically.  This  be due t o i n j e c t i o n  biotite  65°  flakes,  rocks  of a  of part  and t h e c o n t a c t  In the quartz  some  form  parallel  t o the f o l i a t i o n  monzonite  of flow  t h e Danva  banding,  and  dips  as  partially of the E c s t a l l  the f o l i a t i o n i n  of the North  a much weaker i s common.  i n the d i o r i t e  pluton  west  This  foliation,  i t i s s u b - p a r a l l e l to both  series  of  by a s u b - p a r a l l e l  crystals,  to north  lin-  plutons.  and q u a r t z  magma o r o f g r a n i t i z a t i o n as  the  t o have  and  t h e beds  i s expressed  hornblende  probably  In  rocks  developed  intrusion  north  noted,  rocks,  found  west  to the  series,  and i n c l u s i o n s o f m a f i c - r i c h r o c k s .  strikes  north  i n a  i n several directions  were  50°  of the d i o r i t e  of individual  of mafics  folds  t o t h e beds  has w e l l  foliation  folding  of the E c s t a l l  to north  of igneous  intrusion  the  drag  There are  rocks  Mountain  The  part  indicates that  relative  drag  crenulations  In the northern  majority  6.  i s i n d i c a t e d by f i g u r e  foliation  This i s  and quartz  the attitude of the  Mountain  diorite.  foliation  152 varies a  from  strike  a strike  of north  foliation  i s probably  assimilation alignment occurs  nearly  The lineation  alignment  i n situ  rocks type  dip to This  by  I t i s due t o  a n d i n some  places  margin  of the  the s t r i k e  of the  the pluton. has any n o t i c e a b l e  are confined  principally  to the margins  by a  parallel  A l l the lineation  and f o l i a t i o n  to the f o l i a t i o n of the adjacent also  a result  of  assim-  rocks.  Lake  pluton  However, most was  rarely  and a r e probably  o f these  rocks.  parallels outside  minerals.  Sidebacon  foliation.  marginal  immediately  parallel  but rather  to the nearest  and a r e marked  rocks  by f l o w  minerals  These  The  morphic  of mafic  or f o l i a t i o n .  of mafic  and v e r t i c a l  o f the metamorphic  pluton  had s t r i k e s  ilation  not caused  Lake  metamorphic  or  Beaver  west  and d i p o f 8 0 ° n o r t h - w e s t .  perpendicular  rocks  the pluton  noted  ciast  The f o l i a t i o n u s u a l l y  metamorphic  of  i n situ  of clots  pluton.  45°  15°  of north  to lack  of i t s contact  not examined  of lineation  appears  a n d i t may  with  have  lineation the meta-  t h e same  or f o l i a t i o n as t h e other  plutons.  153 CHAPTER  VI  CONCLUSIONS  The rocks  of  the  synclinal River down  metamorphosed, s e d i m e n t a r y  trough.  area in a  Ecstall  may  be  stable  eugeosyncline. bably of  one  an  The  source  island  activity  of  intrusive  island  bodies,  Quaal  may the  the  eugeoRiver-Ecstall  have  been  formation  sediments have  they  The  of  was  been age  a r e most  laid the pro-  the  of  site  these  likely  to  probably have  which  rocks  In  or  perhaps i n the  Ecstall  the  gabbroic  associated with  resulted  the  p a r t , however,  originally  been  of  have  the  been  series  volcanic they in  are  compos-  above  men-  intruded  metamorphism  of  the  during Ecstall  rocks. The  regional  It  in a  associated with  arcs.  volcanic activity  and  for  igneous  flows  tioned  series  to  d o u b t f u l but  w h i c h may  orogeny  they  prior  area  the  volcanic activity.  ition,  the  as  down  (?)  Devonian.  i n part  the  of  pyroclastic  a r c s , w h i c h must  metamorphosed  been  laid  quartzites  exception  i s somewhat  Ordovician to  have  were  environment  or more  The may  The  considerable local  sediments be  series  and  main metamorphism  i n type.  probably preceded  at the  It  took  of  place  the  under  temperatures  i n the  intrusion  the  of  Ecstall strong  range  Coast  of  series  is  compression 400° C  Intrusions.  to The  700°  C.  grade  154 of metamorphism bolite  facies,  generally  staurolite-quartz  muscovite-quartz of  regional  chlorite These  and epidote  i s very  assemblages  approach  zones  the shear The  have  reached  most  they 300  feet  Intrusions present  caused  or less  have  direction  where  The s e r i c i t i z e d  positions  which  rock.  Although  rocks, within  has r e s u l t e d  i nthe  the s i l l i m -  amphibolite series  on them  facies.  i n t h e map  of deformation.  the deformation which  had the strongest e f f e c t  some  grade  of the E c s t a l l  during  with  series  t o and a p p r o a c h i n g  two p e r i o d s  area  not responsible  of the E c s t a l l  rocks  i n this  by i n t r u s i o n  contacts which  at least  o f compression  rocks of  solutions  rocks  s u b f a c i e s o f the almandine  metamorphic  sericite-  i n composition  and r e l a t e d  belonging  undergone  Retrogressive  an i n c r e a s e i n metamorphic  of their  o f rocks  The  zones  series.  passageways.  of the country  a n i t e -almandine  have  as  grade  the E c s t a l l  metamorphism.  which  a high  o f late., s e r i c i t e ,  throughout  i n t e n s e i n shear  o f t h e metamorphism  formation  to  a r e common  amounts  are developed  zones  their  may h a v e  area  Small  amphi-  kyanite-  of quite  may b e d u e t o h y d r o t h e r m a l  Coast  assimilation for  and p o s s i b l y  the greenschist facies.  shear  i s t h e almandine  indicative  a r e due t o r e t r o g r e s s i v e  epidote  used  subfacies,  metamorphism.  metamorphism  the  reached  was p r o b a b l y  The  appears north-  east-southwest. Some Coast to  time  Intrusions  the present  after  (or before?)  e r o s i o n began  time.  the intrusion  i n this  The f e a t u r e that  area  of the  and has c o n t i n u e d  has had t h e most  '  155 effect  i n shaping  the  glaeiation.  The  completely  covered  of  marine  glaciers is the  clays and  gradually marine  isostatic  present  glaciers the  of t h i s  island.  i n the v a l l e y s  deposition filling  clays  topography  at  recovery  the  of  of  this  was  shortly  glacial  altitude  period,  There  talus,  330  amount  is  Pleistocene  at  one  limited  after  stage, deposition  retreat  etc., i s continuing valleys. feet  The  probably  since  their  of  the  and  position  of  indicates deposition.  an  156  BIBLIOGRAPHY Anderson, G.H. ( 1 9 3 7 ) , Granitization, A l b i t i z a t i o n and Related Phenomena i n the Northern Inyo Range of C a l i f o r n i a - ' Nevada, G.S.A. B u l l e t i n , v o l . 4 8 , pp. 1-74. Bacon, R.W. 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(195D, Elements of Optical Mineralogy Part I I , Descriptions of Minerals, John Wiley and Sons, Inc., White, W.H. (1959), C o r d i l l e r a n Tectonics i n B r i t i s h Columbia, A.A.P.G., B u l l . , January, pp. 60G100. Yoder, H.S. J r . (1955), Role of Water i n Metamorphism, Crust of the Earth, G.S.A. Special Paper 62, pp. 505-524.  


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