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Detailed geological mapping and interpretation of the Grand Forks-Eholt area, Boundary district, British… Reinsbakken, Arne 1970

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DETAILED GEOLOGICAL MAPPING AND INTERPRETATION OP THE GRAND FORKS-EHOLT AREA, BOUNDARY DISTRICT BRITISH COLUMBIA  by ARNE REINSBAKKEN B . S c , University of B r i t i s h Columbia, 1968  A THESIS SUBMITTED IN PARTIAL FULFILMENT OP THE REQUIREMENTS FOR- THE DEGREE OP MASTER OF SCIENCE  i n the Department  or Geology  We accept t h i s thesis as conforming to the required standard  THE UNIVERSITY OP BRITISH COLUMBIA December, 1970  In  presenting  this  thesis  an a d v a n c e d d e g r e e the L i b r a r y I  f u r t h e r agree  for  scholarly  by h i s of  shall  this  written  at  permission  is understood  permission.  Depa r t m e n t Columbia  I agree  r e f e r e n c e and this  that copying  not  or  for  that  study. thesis  by t h e Head o f my D e p a r t m e n t  for financial gain shall  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  requirements  for extensive copying of  p u r p o s e s may be g r a n t e d It  the  B r i t i s h Columbia,  it freely available for  representatives. thesis  fulfilment of  the U n i v e r s i t y of  make  tha  in p a r t i a l  or  publication  be a l l o w e d w i t h o u t my  A northward view up Granby River Valley from Thimble Mountain. The ridge i n the foreground and across the Valley i s underlain by the Middle T r i a s s i c Sharpstone Conglomerate and Brooklyn Limestone sequence.  iii ABSTRACT The Grand. Forks-Eholt map area i s underlain predominantly by a sequence of moderately deformed and s l i g h t l y metamorphosed sedimentary and volcanic rocks, previously termed the "Anarchist Group" and ranging i n age from Permian/or E a r l i e r to Middle Jurassic. These rocks are d i v i s i b l e into two d i s t i n c t sequences: (a) cherts (Knob H i l l ) , quartzites, p h y l l i t e s , and greenstones of Permian/or E a r l i e r age. The term Anarchist Group i s now r e s t r i c t e d to t h i s lower sequence which resembles the Cache Creek Assemblage (Penn.-Lower T r i a s s i c ) widespread throughout southcentral B.C.;  (b) Sharp-  stone Conglomerate/Brooklyn Limestone sequence (Middle-Upper T r i a s s i c ) , and overlying Pragmental Andesites (Middle Jurassic) which correlates with the Takla-Hazelton Assemblage  (Middle T r i a s s i c - Middle Jurassic) i n north  c e n t r a l B.C. This upper sequence rests unconformably on -the lower and the Sharpstone Conglomerate forms the basal conglomerate separating the two sequences. The Grand Forks Group (pre-Cambrian/or Early Paleozoic), consisting of paragneisses, minor marble and amphibolites crops out east of the Granby River F a u l t . The f a u l t forms approximately the eastern boundary of the map area. Latest Jurassic Nelson granodiorites; Latest Cretaceous quartz-diorite, quartz-monzonite porphyries, leuco-gabbros and d i o r i t e s ; and Eocene C o r y e l l syenites and related a l k a l i c rocks intrude the sediments and volcanics  pre-  dominantly i n the northern part of the map area. The Nelson granodiorites occur as large b a t h o l i t h - l i k e masses and the younger intrusions form small i r r e g u l a r plugs, dykes and s i l l s .  iv  A NNE  to N trending nearly recumbent s y n c l i n a l structure i s outlined  within the Sharpstone Conglomerate/Brooklyn Limestone/Fragmental Andesite sequence. I t i s transected by prominent NW trending shear/fault zones and has been broken by these into blocks that are downdropped and shifted to the southwest from north to south i n the map area. The eastern part of the map  area i s transected by the NNE  trending Granby River Fault which forms  the northern p r o j e c t i o n of the Eastern Boundary Fault of the Republic Graben - a major s t r u c t u r a l element to the south i n Washington State. Prominent NW and NE Late Cretaceous  to T e r t i a r y fractures are ubiquitous  and often f i l l e d by sheared serpentinites and T e r t i a r y pulaskite and d i o r i t e dykes.  The Middle Jurassic and older sediments and volcanics have been r e g i o n a l l y metamorphosed to the Greenschist Facies. The Grand Forks Group to the east has undergone metamorphism to the  Almandine-Amphibolite  Facies. Large hornfelsed metasedimentary aureoles surround the larger Nelson granodiorite masses. The Brooklyn Limestone has been thermally a l t e r e d to marble and l o c a l l y to chalcopyrite-magnetite bearing c a l c s i l i c a t e skarns, which are often of economic value. Thin contact thermal aureoles surround the Latest Cretaceous quartz-diorite and quartzmonzonite porphyry plugs and dykes, i n d i c a t i n g high l e v e l i n t r u s i o n .  V  TABLE OF CONTENTS Page SECTION  SECTION  I; INTRODUCTION a. Nature and Scope of Project  1  b. Field Approach and Laboratory Studies  2  c. Location and Accessibility  3  d. Previous Work  6  e. General Geology  7  II; STRATIGRAPHY A. SEDIMENTARY SUCCESSION  10  a. Grand Forks Group  10  b. Anarchist Group  13  c. Sharpstone Conglomerate Sequence  19  d. Brooklyn Limestone Formation  30  e. Fragmental Andesites  38  f. Tertiary Layered Rock  44  - Kettle River Formation  44  - Marron Volcanic Formation  47  B. SERPENTINITES  51  C. INTRUSIVE ROCKS  54  a. Nelson Intrusions  54  b. Valhalla Intrusions  56  c. Diorites and Gabbros  57  d. Tertiary Intrusions - Quartz-diorite and quartz-monzonite porphyry intrusions; includes "Scatter Creek Formation" rocks  63  vi Page - C o r y e l l Syenite and P u l a s k i t e Dykes SECTION I I I ; STRUCTURES  SECTION  SECTION  71  a. Republic Graben  71  b. Northwest and Northeast Fault Patterns  73  c. Dyke s  74  d. Folds  75  e. T e r t i a r y Block F a u l t i n g and T i l t i n g  80  IV: METAMORPHISM  84  a. Regional Metamorphism  84  b. Contact Thermal Metamorphism  87  V: SUMMARY AND CONCLUSION  91  a. Summary  91  b. Conclusions  97  c. Suggestions f o r Further Work SECTION  66  VI; REFERENCES  101 103  APPENDIX I ; ECONOMIC GEOLOGY  106  - Mining H i s t o r y  106  - Mineralization  107  APPENDIX I I : FOSSIL LOCATION AND DESCRIPTION  111  LIST OF TABLES Table 1  " Table of Formations  Page 11  LIST OF FIGURES Figure 1 2  3  4  5i 6. 7.  8.  9. 10.  Page Location map of the Grand Forks-Eholt map area, Boundary D i s t r i c t , B r i t i s h Columbia.  5  General g e o l o g i c a l s e t t i n g of the Boundary D i s t r i c t and adjacent Curlew quadrangle i n northern Washington.  8  I d e a l i z e d diagram of the possible source and formation of T r i a s s i c marine basins and the r e l a t e d deposition of the Sharpstone Conglomerate sequence and the Brooklyn Limestone.  28  NW-SE diagrammatic c r o s s - s e c t i o n (looking NE) from the Rathmullen Creek - C.P.R. track i n t e r s e c t i o n to where Lime Creek flows i n t o the Granby V a l l e y .  81  E-W diagrammatic c r o s s - s e c t i o n through Baker Ridge.  82  SW-NE diagrammatic c r o s s - s e c t i o n through Hardy and Goat Mountains.  83  Observed s t r a t i g r a p h i c range of metamorphic minerals and other features of the E a r l y P a l e o z o i c , Permian, and T r i a s s i c - J u r a s s i c rocks ( a f t e r Parker and Calkins (1964), with m o d i f i c a t i o n s ) .  85  P o s s i b l e outside c o r r e l a t i o n s of various rock u n i t s and formations outcropping throughout the Grand Forks area.  96  Sketch and Measurements of Megaphyllites. Mature to Juvenile Suture Patterns of Megaphyllites  113 114  viii LIST OF PLATES Plate  Page  Frontispiece  1.  2.  3.  4.  5.  6.  A northward view up Granby River Valley from Thimble Mountain. The ridge i n the foreground and across the v a l l e y i s underl a i n by the Middle T r i a s s i c Sharpstone Conglomerate and Brooklyn Limestone sequence.  i i  Photograph Typical bedded sharpstone conglomerate with d i s t i n c t alignment of angular chert pebbles. Note large weathered p i t s s t i l l containing limestone cobble remnants, and an increase i n maroon colour towards the top of the picture.  22  Sharpstone conglomerate. Showing predominance of l i g h t green to grey angular chert pebbles. Several dark red jasper pebbles can be seen.  22  Typical "Puddingstone" or limestone cobble conglomerate from exposure along C.P.R. tracks north of Neff Creek. The white elongate rounded cobbles are aligned roughly p a r a l l e l to bedding.  26.  Photograph  Photograph  Photograph A thin lens of sharpstone conglomerate interbedded with a maroon-coloured f i n e grained wacke of the uppermost "Puddingstone" sequence, found west of Baker Ridge.  26.  Photograph "Aeolian limestone" or Seraphim's "Peanut B r i t t l e " limestone forming the basal section of the Brooklyn limestone NW of Baker Ridge. Note alignment of the frosted chert ovoids.  34  Photograph Brooklyn Limestone, t h i n l y bedded, well banded,unit from area immediately west of Grand Forks. Thin more r e s i s t a n t beds are tuffaceous and impure limestone.  34.  ix Page 7.  Photograph Typical fragmental andesite from Goat Mountain. Note several large rounded porphyritic f r a g ments and the l i g h t green-yellow epidote and chlorite alteration.  8.  9.  41  Photograph Spectacular andesite agglomerate outcropping along the southern P r o v i n c i a l Highway i n the July Creek Valley. Camera case - extreme l e f t for scale.  41  Intensely sheared, steeply dipping serpentinite body found within a NW trending f a u l t zone northeast of Hardy Mountain.  53  Coarse-grained s l i g h t l y f o l i a t e d leucogabbro or mela-diorite from east of Hardy Mountain. Composed of plagioclase and hornblende.  53  Photograph  10. Photograph  11. Photograph Coarse-grained quartz-monzonite porphyry ("Scatter Creek Formation"?) from easterly trending dyke at Eagle Mountain.  68  C o r y e l l syenite " c l o t porphyry" v a r i e t y from east of Wilgress Lake.  68  12. Photograph  13. Photograph A NE view of the limestone c l i f f d i r e c t l y opposite the Granby River from the Hummingbird showing. Shows s y n c l i n a l f o l d minor structure within the well banded limestone unit and several f l a t dipping T e r t i a r y dykes.  77  X MAP  I. GEOLOGY Grand Forks-Eholt Area (l"=2000')  i n pocket at back  xi ACKNOWLEDGEMENTS  The author wishes to thank Texas Gulf Sulphur Company f o r the opportunity of working on the project and f o r allowing f u l l use of a l l data and maps on which t h i s thesis i s based. The author was ably assisted i n the f i e l d by C.N. Forster, K.A. Komenac, R.Taylor and P.T. Edwards at various times throughout the summer. Special thanks goes to J.M. Newell, who supervised the f i e l d mapping and with whom the author has spent many hours discussing various aspects of the project. His guidance and enthusiasm were much appreciated. The author would l i k e to thank Mr. J . Paxton, mine geologist at Granby's Phoenix Copper D i v i s i o n , f o r h i s discussions and the loan of several maps' on the p i t geology. Dr. E.T. Tozer of the Geological Survey of Canada at Ottawa discussed the ages of several f o s s i l s found i n the Grand Forks-Phoenix v i c i n i t y . The author would also l i k e to thank h i s supervisor, Dr.A.J. S i n c l a i r , and other f a c u l t y members of the geology department f o r t h e i r discussions and advice given during the preparation of this thesis. F i n a n c i a l assistance during the winter session was obtained from the National Research Council and a teaching assistantship from the University of B r i t i s h Columbia. Texas Gulf Sulphur Company paid f o r a l l t h i n sections and f i n a l d r a f t i n g of the accompanying geological map.  1. DETAILED GEOLOGICAL MAPPING AND INTERPRETATION OP THE GRAND FORKS-EHOLT AREA, BOUNDARY DISTRICT, BRITISH COLUMBIA  Nature and Scope of the Project  During the 1969 f i e l d season, May to September, the author was employed by Texas Gulf Sulphur Company to do detailed geological mapping i n an area adjacent to the Phoenix mine, near Grand Forks, i n southern British  Columbia.  Objective of the programme was to outline the stratigraphy i n the area, paying p a r t i c u l a r attention to the T r i a s s i c Sharpstone Conglomerate and overlying Brooklyn Limestone, the "ore sequence" (Newell, 1969). Previous reconnaissance geology, summer 1968, by J.M. Newell showed that the "ore sequence" formed a good reference throughout the map area. Special emphasis was placed on o u t l i n i n g possible ore l o c a l i z i n g structures such as folds and f a u l t s . The d i f f e r e n t intrusive rocks and related metamorphism, and f a u l t i n g and f r a c t u r i n g were noted with t h e i r possible r e l a t i o n s to mineral deposits. The programme was oriented towards the discovery of deposits similar to the Phoenix mine, about  mile west of the map area. Early prospectors  i n the area appear to have l e f t no stones unturned, hence, i t was f e l t that i f any new mineralization were to be discovered i t would be by projecting the favourable rock types and structures under areas of g l a c i a l d r i f t or T e r t i a r y sedimentary and volcanic cover.  2. F i e l d Approach and Laboratory  Studies  The author spent four months i n the Grand Forks area. Detailed mapping was accomplished using T mile a e r i a l photographs with  transparent  acetate overlays. Outcrop patterns, a i r photo l i n e a r s and the geology were plotted d i r e c t l y onto the overlays i n the f i e l d and t h i s data was l a t e r transferred onto tracing paper over a 1 inch to 1000 feet preliminary topographic  map. Interpretations of f a u l t s , contacts and possible struc-  tures v/ere made d i r e c t l y on the a i r photo overlays. Two long traverses following road cuts along the eastern and western boundaries of the map area and along numerous interconnecting logging roads, f o r e s t r y access roads and abandoned railway grades, provided good exposures and an i n i t i a l o v e r a l l geological picture. This formed a  skel-  eton from which l a t e r interconnecting traverses and helicopter traverses were planned to cover the more open mountain sides and ridges. Much emphasis i n the geological mapping was placed on Newell's "ore sequence", because these r e l a t i v e l y unmetamorphosed sedimentary units contained abundant minor structures, f o s s i l s , and housed a l l the major copper skarn deposits i n the Boundary d i s t r i c t . Very l i t t l e emphasis was given to d i s t i n g u i s h i n g various layered. T e r t i a r y rocks f o r they seem unrelated to copper mineralization i n the area. However, the possible thickness of t h i s T e r t i a r y cover  was of major importance i n t h i s project...  Some 80 thin sections were studied to check the v a l i d i t y of f i e l d names and compositions i n order to postulate possible depositional environments f o r the finegrained rocks of dubious o r i g i n . From such studies  3. i t was hoped that some c r i t e r i a would emerge that would prove useful i n distinguishing the fine-grained hypabyssal basic i n t r u s i v e rocks from fine-grained intermediate volcanic flows. A similar problem was outlined by Monger (1968) i n h i s studies of the T e r t i a r y Marron extrusives and Coryell i n t r u s i v e s i n the area i n which he interpreted some of the C o r y e l l intrusives as feeder dykes to the middle and upper parts of the Marron Formation. The degree of metamorphism was also checked, e s p e c i a l l y the andesites and greenstones  that are unstable i n their present environment, hence very  susceptible to metamorphic change. Much of the detailed mapping was r e s t r i c t e d to areas between and away from the mines and working of the Summit and Phoenix camps, where much of the previous work has been confined. In such areas, the author spent only a short time checking and c o r r e l a t i n g other workers' data.  Location and A c c e s s i b i l i t y  The map  area covers approximately 56 square miles immediately west  and northwest of the c i t y of Grand Forks at the southeastern extremity of the Boundary D i s t r i c t of B r i t i s h Columbia (Figures 1 and 2; pp. 5 and 8 , respect.). I t i s elongate i n a north-northeasterly d i r e c t i o n , i s about 5 miles wide at i t s widest point and about 11 miles long. On the east i t i s bounded by the d r i f t covered Granby River Valley; on the west by July Creek, on the south by the International Boundary and on the north by the Canadian P a c i f i c Railway tracks and Brown Creek running east from Eholt  4. (see Geological map i n back f o l d e r ) . Access to the western and eastern edges of the map area i s provided by the Southern P r o v i n c i a l Highway and the Granby River road respectively. The present Canadian P a c i f i c Railway tracks also provide good rock exposures along the eastern and northern boundaries of the map area. Several abandoned railway grades run through the map area to the old mine workings and are passible by most motorized vehicles. Numerous old and presently used logging roads and wagon t r a i l s can be used by 4-wheel drive vehicles and provide easy access to most points of the map area. Near the southern part of the map area a powerline and a natural gas pipeline access road was also used. The Boundary D i s t r i c t occupies the southern extremity of the B r i t i s h Columbia I n t e r i o r Plateau and the western flank of the Monashee mountains forms the eastern margin. The country i s t y p i f i e d by generally rounded h i l l s and deeply incised g l a c i a l v a l l e y s . Much of the area l i e s between the 3000 foot and 4500 foot elevation  and the maximum r e l i e f i s i n the  order of 2500 feet, the lowest elevation of 1700 feet being i n the Kettle River Valley at Grand Porks. The highest point i s Thimble mountain at the north end of the map area which reaches a height of 4300 feet. To the north the mountains become much more rugged, generally r i s i n g as pyramidal peaks to heights of about 7000 feet. Most of the south facing slopes are open and grassy, with the dry slopes overlooking Grand Porks t y p i c a l of the open "Cariboo type" cover. The northern and western slopes are well wooded,with spruce,lodgepole pine, f i r s and alders predominating. The gently sloped drift-covered v a l l e y  Figure I  Location  Map.  Grand Forks - Eholt map area within dotted area west  of  Grand Forks.  6. bottoms are i n places swamp-like with dense cedar growths, making traverses next to impossible. The mountain tops and ridges are generally open and grassy providing numerous helicopter landing spots.  Previous Work Early geological mapping (Brock, 1901, 1902; Daly 1912; McNaughton, 1945)> was confined mainly to old workings and adjacent areas. Many of t h e i r ideas are now out of date i n the l i g h t of some recent detailed mapping. Recent work by Seraphim (l956), sets f o r t h some c r i t e r i a for separating the various rock types that were previously believed products of s i l i c a metasomatism. H.T. Carsxrell (1957), a few years l a t e r extended Seraphim's d i v i s i o n of rock units to the Summit Camp, but mainly confined h i s detailed work to the o l d showings. More recently, f i e l d studies i n the Grand Forks-Greenwood area by the Geological Survey of Canada include: a 1 inch=4 mi. map of the Kettle River area (East Half) by L i t t l e (1957) i n xvhich no attempts were made to separate the Permian and younger sedimentary and volcanic rock units; a complete study i n the Greenwood map area of the T e r t i a r y sedimentary, volcanic and igneous rocks by Monger (1968); and a f i e l d report of regional mapping carried out by L i t t l e and Thorpe (l965), i n which they appear to have applied Seraphim's breakdown of the Permian and younger rock units on a regional scale. The most recent a r t i c l e about the Grand Forks map area i s a compilat i o n from various geological reports and maps by J.M. Newell (1969). Newell*s report r e i t e r a t e s Seraphim's c r i t e r i a f o r separating various  7. rock units and emphasizes Seraphim's b e l i e f i n a sedimentary o r i g i n f o r the controversial Sharpstone Conglomerates. I t was from Newell's report that the author obtained many of h i s early ideas, some of which have become incorporated into t h i s thesis. Detailed mapping, i n northern Washington State, f o r the United States Geological Survey was done by Parker and Calkins subdivisions made i n the Permo-Jurassic  (1964), however the only  sedimentary and volcanic rock  sequence was the T r i a s s i c (?) carbonates versus the other rock types. Correlation from the Grand Forks map area i n t o northern Washington i s further hampered by the difference i n nomenclature,  d i f f e r e n t map units  and d i f f e r e n t map scales.  General Geology The Grand Forks map area i s underlain predominantly by a sequence of moderately deformed and s l i g h t l y metamorphosed sedimentary and volcanic rocks ranging i n age from Permian and/or e a r l i e r to Jurassic, that previ o u s l y had been termed the "Anarchist Group". These rocks were intruded by several Cretaceous and younger granodiorite, d i o r i t e ,  quartz-monzonite  and a l k a l i c i n t r u s i v e bodies. Block f a u l t i n g and shearing along northwest and northeast trending f a u l t s i s common. An intermittent covering of T e r t i a r y continental sedimentary and volcanic rock marks much of the T e r t i a r y h i s t o r y (Figure 2, page 8 ) . The map area i s bounded on the east by the Granby River Fault, which extends f o r some 50 miles south into Northern Washington and across which l i e s the intensely metamorphosed gneissic t e r r a i n of the Monashee Range (Figure 2 ) .  8.  J Early T e r t i a r y  intrusive  Early Tertiary sedimentary and volcanic rocks  • j3  Ultrabasic  intrusives  Nelson and Valhalla acid intrusives Miles 0  10  '  to Mid. J u r a s s i c u n divided sed. and vol. rocks  "I Shuswap type ' terrain '  Major  metamorphic  faults  Grand F o r k s - E h o l t  Figure 2 .  General District  geological BC,  in northern  and  equivalent  Pemian  •  20  rocks  setting  of  adjacent  the Curlew  map area  Boundary quadrangle  Washington, ( a f t e r Monger,1967-,  G.S.C. map 9 3 2 A j Parfcer  and C a l k i n s ; 1964.)  9. Granitic and alkalic rocks of the Nelson, Valhalla and Coryell intrusive complexes pervade the area immediately north of the map area. Permian Anarchist cherts and greenstones predominate the area west of Phoenix. Tertiary sedimentary and volcanic rocks underlie most of the area west of Greenwood, and also appear  to become more abundant within the Republic  Graben, a major NNE trending structure in Curlew County N.Washington (Pig.2). It appears probable that the so called "Anarchist Group" i n this area includes both Permian and Triassic-Jurassic rocks, which, as suggested by Newell (1969), may possibly correlate with Cache Creek and Nicola-Takla Groups elsewhere i n British Columbia. The regional geology of the area suggests that an unconformity exists between the Permian and Triassic units, marked by the basal Sharpstone Conglomerate. The lithologies of the older units suggest a deep-quiet, offshore, marine,possibly island arc environment; lithologies of the younger units, on the other hand, indicate rapid deposition i n shallow water, suggesting "a shore line environment at the edge of the Nicola Sea" (Newell, 1969). This indicates that the area was not completely submergent during Triassic time, i n agreement with Campbell (1966, pp.63-64).  10.  SECTION I I ;  STRATIGRAPHY  A . STRATIGRAPHIC SUCCESSION Grand Forks or Monashee Group  Host of the author's f i e l d work i n the Grand Forks area was ted  restric-  to the western side of the Granby River Valley and consequently very  l i t t l e information was compiled on the Grand Forks Group. These rocks are of general i n t e r e s t because they form the abrupt eastern boundary against which the rocks underlying the Grand Forks-Eholt area abut. Most of the information herein i s derived from the reports of Parker and Calkins (1964) and L i t t l e  (1957).  The Grand Forks Group contains the oldest rocks i n the Boundary area. Brock (l902) described them as c r y s t a l l i n e mica and hornblende  schists  with a few bands of c r y s t a l l i n e limestone. Later mapping by L i t t l e has outlined an  (1957),  intensely metamorphosed t e r r a i n comprised of granite  gneiss, marble, hornblende schists and f o l i a t e d granite s i l l s . Parker and Calkins (1964), to the south of Grand Forks i n northern Washington, mapped i n some d e t a i l , a sequence of intensely regionally metamorphosed sediments and igneous rocks having a thickness of about 17,000 feet, which they c a l l e d the Tenas Mary Creek Formation. These Tenas Mary Creek rocks are t y p i f i e d by a gradual decreasing degree of metamorphism with decreasing stratigraphic depth: orthoclase-quartz-oligoclase gneiss characterizes the lowermost  strata; through marble, quartzites, hornblende  schists,  quartz-plagioclase gneiss to schists and p h y l l i t e s i n the upper parts. However, Parker and Calkins' Tenas Mary Creek Formation encompasses both  TABLE I ; TABLE OF FORMATIONS ERA  Cenozoic  PERIOD OR EPOCH  FORMATION AND THICKNESS IN FEET  LITHOLOGY  Recent  Stream alluvium, t a l u s , s o i l .  Pleistocene  Glacial drift  Oligocene  Coryell intrusives  B i o t i t e and potash-feldspar syenite porphyry, p u l a s k i t e , and r e l a t e d a l k a l i c rocks.  ("Scatter Creek" Formation?)  Quartz-monzonite, q u a r t z - d i o r i t e porphyries; minor d i o r i t e s .  I n t r u s i v e Contact? Eocene-Oligocene?  Marron Formation 300 feet  Intermediate volcanic flows. Sodic trachytes, andesites, phonolites; generally porphyritic.  Middle Eocene  K e t t l e River Formation 1200 feet  Arkose, and volkanic sandstone, a c i d t u f f s , l o c a l conglomerate and shale.  F a u l t bounded and i n t r u s i v e contacts Late Cretaceous or Early Tertiary  D i o r i t e s and gabbros  D i o r i t e s and leuco-gabbro, found as dykes and i r r e g u l a r i n t r u s i v e bodies associated with the NW prominant f a u l t zones. May include coarsegrained andesites and border phases of Nelson g r a n o d i o r i t e s .  Fault contacts, contemperaneous Late Cretaceous or E a r l y T e r t i a r y  S e r p e n t i n i t e s and Pyroxenites  Serpentinized u l t r a b a s i c s , pyroxenites; l o c a l l y a l t e r e d to carbonate, t a l c , and mariposite rock. R e s t r i c t e d to NW shear zones.  contact not seen (sheared?) Mesozoic  Upper J u r a s s i c  Valhalla intrusives  Coarse-grained granite generally non-porphyritic  Nelson i n t r u s i v e s  Granodiorite to q u a r t z - d i o r i t e g e n e r a l l y non-porphyritic  I n t r u s i v e contact Middle.Jurassic  Fragmental Andesites maximum 2000' (variable)  Andesites; flow b r e c c i a s , massive flows, agglomerates and minor p i l l o w s , and greenstones.  Unconformity; conformable i n part Upper T r i a s s i c .  Brooklyn limestone maximum 2000'  Mostly massive, bedded, a r g i l l a c e o u s limestone, w i t h banded tuffaceous limestone, minor b r e c c i a s , limy chert pebble sandstone, l o c a l marble and skarn.  Gradational and sharp Middle? to Upper Triassic  Sharpstone conglomerate sequence 2000' maximum  Angular chert pebble conglomerate, as beds and lenses, interbedded with a r g i l l i t e s , mudstones, s i l t s t o n e s , and w a t e r - l a i d t u f f s . Includes the maroon coloured limestone cobble conglomerate or "Puddingstone" and "Rawhide Shale".  UnconformityPaleozoic  Permian and/or penn.  Anarchist group, thickness unknown.  Intensely sheared and f r a c t u r e d cherts, q u a r t z i t e s , p h y l l i t e s , cherty a r g i l l i t e s and black massive a r g i l l i t e s ; greenstones, l o c a l l y quartz-mica s c h i s t ; undivided a r g i l l a c e o u s and s i l i c e o u s hornfelsed metasediments.  Faulted contact E a r l y Paleozoic or Pre-Cambrian  Grand Forks and Monashee Group, thickness unknown.  Layered paragneisses, minor marble, amphibolites, q u a r t z i t e s , e t c .  12. the Grand Forks Group and the schists and p h y l l i t e s of the upper portion of the Anarchist Group that i n the Boundary D i s t r i c t appears to overly the Grand Forks Group. Parker and Calkins stated that the lower part of the Tenas Mary Creek Group most l i k e l y correlates with rocks of similar l i t h o l o g y and gross structure i n the v i c i n i t y of Grand Forks. Considering the Tenas Mary Creek Formation to be one continuous stratigraphic sequence, then one f i n d s i n the Grand Forks area the lowermost paragneisses (Grand Forks Group) and the uppermost schists and p h y l l i t e s (Anarchist Group) of t h i s stratigraphic column i n faulted contact with each other. The Grand Forks Group contains gently dipping east-west gross structures as do the Tenas Mary Creek rocks to the south. Contact r e l a t i o n s with younger rocks i n the map area are obscure f o r the Granby River Fault forms the western boundary of the Grand Forks Group. The high-grade metamorphic rocks are believed either, the u p l i f t e d , deeply weathered basement on which the younger, l e s s metamorphosed Anarchist rocks were deposited, or, as Parker and Calkins suggest, they may represent the lower more intensely metamorphosed portion of a continuous stratigraphic sequence stretching up into the upper reaches of the Anarchist Group. Brock  (1902) noted that the Grand Forks rocks resembled the highly  metamorphosed rocks of the Shuswap complex; and Parker and Calkins  (1964)  also stated that the Grand Forks rocks appear continuous with high-grade schists and gneisses i n the Orient region of northern Washington State, postulated as being pre-Cambrian i n age and similar to the Shuswap t e r r a i n of southern B r i t i s h Columbia. The age of the Shuswap metamorphic complex and time of metamorphism i s not well documented at present but  13. Reesor (l970,p.73) i n discussing the s t r u c t u r a l evolution and regional setting i n part of the Shuswap metamorphic complex, of which the C h r i s t i n a Lake segment i s part, f e l t that: "rock involved i n the gneiss complex are considered to be the stratigraphic equivalents of the Windermere ( l a t e s t pre-Cambrian) and Paleozoic successions of the P u r c e l l - S e l k i r k mountains. Deformation and metamorphism of these strata i s post Mississippian (Milford Group) and possibly post T r i a s s i c (Slocan Group)". Hence i t appears that the Grand Forks Group can be as old as l a t e s t preCambrian age.  Anarchist Group Previous mapping of the so-called "Anarchist Group" within the Boundary D i s t r i c t included a variety of sedimentary and volcanic rocks ranging i n age from pre-Permian to Jurassic. Recently, L i t t l e (l965), redefined the Anarchist Group as Permian and/or pre-Permian, highly deformed and intensely fractured meta-cherts, a r g i l l i t e s , schists and  phyllites,  greenstones.  Anarchist rocks crop out only sparsely within the Grand Forks-Eholt map  area: 1.  immediately  west of Grand Forks, north of the International  Boundary; 2.  south of Fisherman Creek along the Canadian P a c i f i c Railway tracks - east of Baker Ridge; and  3.  immediately  east of the Shickshock and S a i l o r Boy showings at  the northeast corner of the map  area.  14. Anarchist rocks within the map area are d i v i s i b l e into two mappable units; a lower s i l i c e o u s unit and an upper a r g i l l a c e o u s u n i t . The  lower  s i l i c e o u s unit consists of intensely fractured white to grey microc r y s t a l l i n e chert and quartzite with minor quartz-sericite (?) schist. Cherts are characterized by a s l i g h t f o l i a t i o n or micaceous (white mica) parting that p a r a l l e l s the o r i g i n a l bedding (Parker and Calkins,1964), and a complete r e c r y s t a l l i z a t i o n of the chert and clear quartz f i l l i n g the numerous c r i s s - c r o s s i n g fractures, giving the rock a cross-hatched pattern i n outcrops. This f o l i a t e d chert predominates i n the southern area west of Grand Forks where the f o l i a t i o n trends south-southeast, dipping moderately to the northeast. A similar chert unit also underlies the northern area east of the Shickshock and S a i l o r Boy showings. In this area, a thin d i s continuous band of grey chert pebble conglomerate i s found interbedded with the white f o l i a t e d chert unit. The pebbles, t y p i c a l l y pale grey to black, are composed predominantly of grey chert and dark argillaceous chert set i n a microcrystalline cherty matrix. The fragments are well sorted and sub-rounded. Quartz-muscovite  schists also crop out i n the northern area  immediately adjacent to the f a u l t zone separating the s i l i c e o u s unit from limestones to the west. Muscovite partings p a r a l l e l the f a u l t plane, dipping moderately to the west, and probably were formed during mechanical shearing  associated with movements along the f a u l t zone.  Quartz-muscovite  or s e r i c i t e schists have been found c l o s e l y associated with t h i s lower s i l i c e o u s unit throughout the Grand Forks area. Several outcrops and bands of grey microcrystalline chert and chert  15. pebble conglomerate  are present i n Anarchist rocks that crop out immed-  i a t e l y south of Fisherman Creek. These rocks, however, occur within a major northwest  trending f a u l t zone that appears to have brought the  s i l i c e o u s rocks from depth, and relationships between the i n d i v i d u a l blocks and outcrops are obscure. L i t t l e (1965), divided the Anarchist Group into six units.  The  author's s i l i c e o u s unit correlates with L i t t l e ' s map unit 2, which consists of "bedded chert"* commonly with argillaceous partings, c h l o r i t e schists and mica s c h i s t s . Overlying the s i l i c e o u s unit with apparent conformity, although with obscure contact r e l a t i o n s h i p s , i s a r e l a t i v e l y thin sequence of dark argillaceous rocks ranging from black to grey well bedded a r g i l l i t e s and black cherty a r g i l l i t e s , with minor grey cherts, cherty s i l t s t o n e s and an angular chert pebble conglomerate. with L i t t l e ' s map unit 3.  This argillaceous sequence correlates  An extensive sequence of t h i s black well  bedded a r g i l l i t e , cherty a r g i l l i t e with minor interbedded dark shale, grey chert and chert pebble conglomerate  i s found underlying the area adjacent  to the Canadian P a c i f i c Railway tracks immediately  south of Fisherman  Creek. These extremely fine-grained a r g i l l i t e s occur as small elongated, f a u l t bounded blocks, caught up i n an extensive north-west  trending shear  s zone, that obscur^ i n t e r n a l structure and r e l a t i o n s between the outcrops, making correlations highly speculative. Several of these well bedded a r g i l l i t e s are sheared.  Present thicknesses of these argillaceous units  are generally under 100  to 150 f e e t . Minor syngenetic pyrite and  pyrrhotite (?) has been found conformable  to bedding planes within the  16. dense black a r g i l l i t e , suggesting deposition i n a deep r e s t r i c t e d basin under quiet,reducing conditions. The angular chert pebble conglomerate found interbedded with the black massive cherty a r g i l l i t e s and w e l l bedded a r g i l l i t e s has been mapped as part of the Sharpstone Conglomerate sequence by the author, but may w e l l be a conglomerate u n i t occurring w i t h i n the Anarchist Group, as i t contains numerous grey to black sub-rounded chert fragments, set i n a cherty matrix. The fragments appear much more rounded, sorted, and homogenous i n composition than those t y p i c a l of the Sharpstone Conglomerate cropping out to the south. The Sharpstone Conglomerate also has a greenish coloured c h l o r i t i z e d matrix and i s not composed of m i c r o c r y s t a l l i n e chert. A much more d e t a i l e d study i s needed to separate these two conglomerate units. Immediately west of Grand Forks a t h i n sequence of dark p h y l l i t e apparently l i e s with g r a d a t i o n a l contact, above the f o l i a t e d chert u n i t . F o l i a t i o n s and crenulations w i t h i n the p h y l l i t e have the same north-northwest trend as i n the underlying cherts. This p h y l l i t e i s composed of s e r i c i t e , c h l o r i t e and b i o t i t e p a r a l l e l to c l a y s i z e dark laminae, a s i l k y l u s t r e . These  micas,  imparting  surrounding rounded to elongate broken  quartz g r a i n s and laminae, suggest  r o t a t i o n and mechanical movement.  A t h i n , dark, well-bedded a r g i l l i t e u n i t i s found underlying the Sharpstone Conglomerate sequence east of the s i l i c e o u s u n i t at the northeastern corner of the map area. The bedding w i t h i n the a r g i l l i t e appears conformable to the o v e r l y i n g Sharpstone Conglomerates and as the a r g i l l i t e s appear r e l a t i v e l y undeformed and unsheared, rather a t y p i c a l of the  17. Anarchist cherts to the west, t h i s a r g i l l i t e unit may well be a s t r a t i graphic equivalent of the Rawhide shales found by Seraphim, underlying the Sharpstone Conglomerate at Phoenix. L i t t l e (1965) mapped a massive limestone unit with minor chert i n t e r beds, below the Knob H i l l massive cherts and greenstones, south of Phoenix. A similar unit of thin well-bedded argillaceous limestone crops out along the Canadian P a c i f i c Railway tracks approximately 3,500 feet to  4,000 feet southeast of Goat Mountain. This 50-foot-thick limestone band occurs between two thin grey cherty s i l t s t o n e s and appears to underlie a thick? massive amygdaloidal basalt or greenstone which may be equivalent to the Knob H i l l greenstone i n the Phoenix area to the west. The basalt unit appears to be overlain to the west by the T r i a s s i c Brooklyn  Limestone  and lower Jurassic Fragmental Andesites, but contact r e l a t i o n s are obscured by the numerous cross-cutting f a u l t s and a more detailed study i s needed to separate the various limestone units and greenstones i n t h i s area. Contacts between the Anarchist rocks and the older rocks are not seen i n the map area, but appears to be faulted - the Granby River Fault separates the Anarchist rocks from the Grand Forks and Monashee gneissic t e r r a i n to the east. Parker and  Calkins (1964) believe that the schists  and p h y l l i t e s i n northern Washington, equated to the Anarchist Group i n the Boundary  D i s t r i c t , form the uppermost strata of a continuous  strati-  graphic sequence from the Early Paleozoic Tenas Mary Creek Formation or Grand Forks Group equivalent, up to the Permian schists and p h y l l i t e s . Contacts between the Anarchist rocks and the younger T r i a s s i c and Jurassic  18.  rocks i n the Grand Forks area are either drift-covered or f a u l t s , but most writers agree that the T r i a s s i c and younger layered rocks l i e unconformably on top of the Anarchist rocks, the Sharpstone Conglomerate representing a basal conglomerate. The Anarchist Group i s believed to be Permian and/or e a r l i e r . L i t t l e  (1965) mentions possible Paleozoic f o s s i l s from several l o c a l i t i e s within the dark well-bedded a r g i l l i t e s , h i s unit No. 3.  Waters and Krauskopf  (l94l) postulate a Permian and possibly Pennsylvanian age f o r p r o t o c l a s t i c border rocks surrounding  the C o l v i l l e Batholith near O r v i l l e , Washington,  that have been correlated with the Anarchist rocks. Deformation within Anarchist rocks i s intense but i n t e r n a l structures and degree of f o l d i n g are obscured by the intense mechanical movement associated with the f r a c t u r i n g and shearing, and because of the general lack of good marker beds. Poor outcrop exposures and the great distances between these exposures within the Grand Forks-Eholt map  area  makes c o r r e l a t i o n s d i f f i c u l t . The Anarchist Group appears to by t y p i c a l of the widespread Cache Creek Assemblage as described by Campbell  (1966). This assemblage i s  characterized by massive cherts, ribbon cherts, greenstones, black p h y l l i t e s , schists, amphibolites and a r g i l l i t e s , that were deposited i n a quiet deep water, marine environment.  The Cache Creek Assemblage i s also  characterized by intense f r a c t u r i n g and primari l y  a lack of d i s t i n c t i v e  u n i t s or marker horizons and has an age range from Mississippian to E a r l y T r i a s s i c , similar to the Anarchist Group.(see Figure 8, p. Little  96).  (1957) also mentions the s i m i l a r i t i e s of the Anarchist rocks  19. to the Mount Roberts Formation underlying the Rossland Formation some 30 miles east of the Grand Forks area.  Sharpstone Conglomerate Sequence The Phoenix Sharpstone Conglomerate has been the subject of much controversy over the years. E a r l y w r i t e r s (Brock, LeRoy) c l a s s i f i e d the rock as a "jasperoid" and postulated d e r i v a t i o n from limestone by a process of s i l i c i f i c a t i o n .  The calcareous matrix was believed to represent un-  a l t e r e d rock, the "fragments", the products of hydrothermal processes r e l a t e d to ore formation. McNaughton (1945) preserved the jasperoid terminology and i t remained i n the l i t e r a t u r e u n t i l the term "sharpstone conglomerate" was f i r s t proposed by Seraphim ( l 9 5 6 ) , wherin he presents reasons f o r assigning a sedimentary o r i g i n to t h i s l i t h o l o g i c u n i t . Seraphim (1956, p.688), suggests a s l i g h t r e c r y s t a l l i z a t i o n of the quartz or chert accompanying the subsequent metamorphism. Seraphim also l i s t s several convincing  reasons f o r a sedimentary o r i g i n f o r the Sharpstone Conglomerate,  summarized below: 1.  The sharpstone conglomerate has a heterogeneity of colour, s t r u c t u r e , and composition of fragments that can not be a t t r i b u t e d to a metamorphic o r i g i n .  2.  The rock i s bedded; shale, impure limestone and s i l t s t o n e beds a few inches t h i c k and hundred foot t h i c k fragmental beds have conformable contacts. The fragments are rudely aligned p a r a l l e l to the bedding.  20.  3.  Several outcrops containing interbedded  fragmental  rock and s i l t -  stone or shaly s i l t s t o n e show scour and f i l l structures. The author also noted graded beds and cross bedding. 4.  In fragmental  beds that are s t r a t i g r a p h i c a l l y close to the beds  of limestone,  shale or s i l t s t o n e , the chert fragments are smaller,  more rounded and better sorted i n size than the chert fragments i n most fragmental  beds elsewhere, usually occurring s t r a t i -  graphically below the former. This suggests longer transport or some reworking or sorting. 5.  The large rounded limestone remnants, mentioned by LeRoy, so numerous i n the jasperoid near the contact with the limestone, are a c t u a l l y pebbles and boulders deposited with the chert fragments. These limestone remnants are suggestive of rapid transport.  The Sharpstone sequence encompasses a great variety of c l a s t i c rocks ranging from angular chert pebble conglomerate or "sharpstone conglomerate", to bedded and massive fine-grained a r g i l l i t e s , mudstones and s i l t s t o n e s with minor interbeds of greywacke or fine-grained sharpstone conglomerate equivalents and minor water l a i d t u f f s .  Thin calcareous bands have also  been noted within the upper a r g i l l i t e sequences. This r e l a t i v e l y thick sequence of coarse-to-fine-grained  clastic  debris r e s t s unconformably on the Permian and e a r l i e r Knob H i l l cherts and greenstone as mapped by Seraphim (1956) at Phoenix, and probably forms a basal conglomerate representing the unconformity separating the deep  21.  water s i l i c e o u s Anarchist rocks from the overlying shallow water c l a s t i c "Sharpstone Conglomerate" sequence and Brooklyn Limestones (Figure 3, p.28 The sharpstone conglomerate i s composed e s s e n t i a l l y of angular pebble of white to grey microcrystalline chert, minor dark to l i g h t green l i t h i c volcanic and dark shaly fragments and rare jasper fragments set i n a finer-grained matrix of similar composition with minor micaceous, carbonaceous and some tuffaceous matter  (Plate 1 and 2, p. 22). Angular  fragments average from T"-%" i n diameter but l o c a l l y can be larger and commonly much smaller. The fine-grained matrix i s extremely variable but appears to be about 5-6 orders of magnitude smaller. Changes i n the composition and size of the angular pebble fragments are  variable throughout the map area. The l i t h o l o g i c variations of the  conglomerate fragments have not been studied to any great extent but a few general trends were noted. The thick Sharpstone Conglomerate  sequence  cropping out west of Baker Ridge and towards Phoenix contains a great abun dance of grey to white angular chert pebbles with minor dark green l i t h i c volcanic and shaly fragments, and several brick red jasper pebbles, (Plate l ) , probably r e f l e c t i n g a source from the more s i l i c e o u s rocks of Knob H i l l cherts that underDie the Sharpstone sequence to the west and south of Phoenix.  Sharpstone conglomerates exposed northeast of Thimble  Mountain along the Canadian P a c i f i c Railway tracks at the northeast corner of the map area, however, contain numerous dark greenish l i t h i c volcanic fragments with minor l i g h t coloured l i t h i c fragments and minor white chert or quartz fragments, probably r e f l e c t i n g a source from the Anarchist greenstones to the west.  No  jasper  fragments were found. The Sharpstone  21. water s i l i c e o u s Anarchist rocks from the overlying shallow water c l a s t i c "Sharpstone Conglomerate" sequence and Brooklyn Limestones (Figure 3, p.28). The sharpstone conglomerate i s composed e s s e n t i a l l y of angular pebbles of white to grey microcrystalline chert, minor dark to l i g h t green l i t h i c volcanic and dark shaly fragments and rare jasper fragments set i n a finer-grained matrix of similar composition with minor micaceous, carbonaceous and some tuffaceous matter  ( P l a t e 1 and 2, p. 22).  Angular  fragments average from T"-1T" i n diameter but l o c a l l y can be larger and commonly much smaller. The fine-grained matrix i s extremely variable but appears to be about 5-6 orders of magnitude smaller. Changes i n the composition and size of the angular pebble fragments are  variable throughout the map area. The l i t h o l o g i c variations of the  conglomerate fragments have not been studied to any great extent but a few general trends were noted. The thick Sharpstone Conglomerate  sequence  cropping out west of Baker Ridge and towards Phoenix contains a great abundance of grey to white angular chert pebbles with minor dark green l i t h i c volcanic and shaly fragments, and several brick red jasper pebbles, (Plate l ) , probably r e f l e c t i n g a source from the more s i l i c e o u s rocks of Knob H i l l cherts that underlie the Sharpstone sequence to the west and south of Phoenix.  Sharpstone conglomerates exposed northeast of Thimble  Mountain along the Canadian P a c i f i c Railway tracks at the northeast corner of the map area, however, contain numerous dark greenish l i t h i c volcanic fragments with minor l i g h t coloured l i t h i c fragments and minor white chert or quartz fragments, probably r e f l e c t i n g a source from the Anarchist greenstones to the west.  No  jasper  fragments were found. The Sharpstone  P l a t e 1:  T y p i c a l bedded sharpstone conglomerate with d i s t i n c t alignment of angular chert pebbles. Note large weathered p i t s s t i l l containing limestone cobble remnants, and an increase i n maroon colour towards the top of the p i c t u r e .  P l a t e 2:  Sharpstone conglomerate showing predominance of l i g h t green to grey angular chert pebbles. Several dark red jasper pebbles can be seen.  23. Conglomerate occurring west of Grand Forks also contains predominantlydark brown-black l i t h i c volcanic pebbles, with very few, i f any, l i g h t chert fragments. Within both the southernmost and northernmost l o c a l i t i e s just mentioned, the conglomerate pebbles and e s p e c i a l l y the finer-grained matrix have been noticably s i l i c i f i e d and contain minor amounts of disseminated p y r i t e . Sharpstone Conglomerates i n the v i c i n i t y of Hardy Mountain appear very similar i n composition to the conglomerate found west of Baker Ridge and along the Canadian P a c i f i c Railway tracks east of Baker Ridge, but a decrease i n pebble size i s noted with an the  accompanying s l i g h t rounding of  pebbles southeast from the Phoenix cut-off road to Eagle Mountain. The Sharpstone Conglomerate occurs generally as thick masses and  lenses i n the northeastern and western parts of the map area and displays sharp v e r t i c a l stratigraphic boundaries and rapid l a t e r a l f a c i e s changes. Sharpstone conglomerate t y p i c a l l y occupies the bottom of the Sharpstone sequence but also occurs as thinner lenses higher i n the sequence i n t e r bedded with the finer-grained greywackes and mudstone-siltstones. The conglomerate appears to t h i n and pinch out southeast of Eagle Mountain, where thin bedded a r g i l l i t e s and mudstone predominate. West of Baker Ridge, north of Thimble Mountain and at Eagle Mountain, the  basal sharpstone conglomerates show a marked upward decrease i n the  proportion of coarse c l a s t i c fragments.  The sharpstone conglomerate,  therefore, grades upwards into the finer-grained a r g i l l i t e s , mudstones, s i l t s t o n e s with minor intercalated greywacke bands, frequently showing scoured bottom contacts. Higher i n the sequence the fine-grained  24.  a r g i l l i t e s are t y p i c a l l y well-bedded and continuous, r e f l e c t i n g a r e l a t i v e l y quiet environment of deposition. Greywackes are t y p i c a l l y a finer-grained equivalent of the sharpstone conglomerate, the fragments appear more rounded and smaller, probably r e f l e c t i n g a reworking of a previous conglomerate source or a less rapid deposition and more distant source. The a r g i l l i t e s , mudstones and the finer-grained matrix of the sharpstone conglomerate are composed predominantly of microscopic c l a s t i c quartz, feldspar and l i t h i c fragments mixed with abundant clay-size p a r t i c l e s aligned roughly p a r a l l e l to the bedding. The finer-grained matrix contains abundant a l t e r a t i o n shreds of c h l o r i t e and minor s e r i c i t e , carbonate and possibly pyrophyllite?  The o v e r a l l great abundance of  c h l o r i t e , up to 25-30% of the matrix i n places, imparts a prominant greenish colouration to the rocks that i s so c h a r a c t e r i s t i c i n the Grand Porks area. Near the top of the Sharp: tone sequence, an increase i n carbonate material i s noted and i n several places, such as immediately southeast of Eagle Mountain, several d i s t i n c t 20-30 foot thick bands of white  recrys-  t a l l i z e d limestone have been found interbedded with the a r g i l l i t e s . Similar t h i n carbonate bands have been found within the maroon coloured mudstone-siltstone along the highway immediately west of Baker Ridge. A maroon coloured angular chert pebble conglomerate and mudstone, s i l t s t o n e , carbonaceous rock sequence, l i t h o l o g i c a l l y i d e n t i c a l to the Sharpstone Conglomerate  sequence, occupies the upper stratigraphic posi-  t i o n within the Sharpstone sequence south of the Phoenix road junction  25. and along the Canadian P a c i f i c Railway tracks immediately north of Neff Creek.  Called "Puddingstone" by the oldtimers, this rock derives i t s name  from the large white rounded limestone cobbles set i n the maroon coloured angular chert pebble conglomerate matrix that appears to occupy a certain stratigraphic horizon near the top of the conglomerates underlying the a r g i l l i t e s (Plate 3 and 4, p. 26). These limestone cobbles help to outl i n e the bedding. Several outcrops show the clear t r a n s i t i o n from a green colour to t h i s t y p i c a l maroon or dark red-brown colour  up  maroon colour r e s u l t s from f i n e l y disseminated  strata,  (Plate l ) . The  hematite or oxidized i r o n  and suggests formation under oxidizing conditions. This maroon colour i s also t y p i c a l of the overlying limestones which thin and pinch out immediately west of Baker Ridge and appears to represent an ancient oxidized erosion surface roughly underlying Baker Ridge. Similar maroon coloured a r g i l l i t e s have also been noted within the Phoenix open p i t and might represent a similar erosion surface. On the other hand, i t could represent oxidation conditions produced from hydrothermal a l t e r a t i o n associated with ore formation at Phoenix. Large rounded, white limestone cobbles, generally l e s s than 1 foot across, so c h a r a c t e r i s t i c of the "puddingstone", are also found i n several l o c a l i t i e s occupying a similar stratigraphic l e v e l within the sharpstone conglomerate(Plate 1, p.22): along the abandoned r a i l r o a d grade some 5>000 feet northwest of Hardy Mountain; weathered limestone p i t s are found p a r a l l e l i n g the bedding of the Sharpstone Conglomerates underlying Eagle Mountain; s k a r n i f i e d limestone boulders also occur within the sharpstone  P l a t e 3:  T y p i c a l "Puddingstone" or limestone cobble conglomerate from exposure along Canadian P a c i f i c Railway tracks north of Neff Creek. The white rounded limestone cobbles are aligned roughly p a r a l l e l to bedding.  P l a t e 4:  A t h i n lens of sharpstone conglomerate interbedded with a maroon-coloured f i n e grained wacke of the uppermost "Puddingstone" sequence, found west of Baker Ridge.  27. conglomerates immediately west of Grand Forks. These limestone cobbles appear to decrease i n size and increase i n roundness towards the southeast from the Fhoenix road junction to Eagle Mountain, suggesting a similar source, from the west or northwest and an increasing distance of transport to the southeast. Most writers believe the sharpstone conglomerates are derived from the  cherty sediments of the Knob H i l l series  (Anarchist Group), with  l o c a l variations i n the amounts of l i t h i c , volcanic, sandstone, minor shale and jasperoid fragments depending on the l i t h o l o g y of the source e.rea. The t h i c k l y bedded sequence of angular conglomerate probably represents rapid accummulation of talus deposits on a steep f a u l t scarp formed at the edge of the shallow T r i a s s i c sea (Figure 3» p.28). These ancient f a u l t scarps appear to have been northerly trending structures with the downdropped block t i l t i n g westerly. With, a rapid inpouring of coarse c l a s t i c debris from the west, a large talus or d e l t a i c p i l e of sharpstone conglomerate formed against the western edge of this scarp. Farther from the  source, within the basin (to southeast), the conglomerate lenses thin  r a p i d l y and fine-grained greywackes, mudstones, s i l t s t o n e s and well-bedded a r g i l l i t e s i n t e r f i n g e r and i n t e r c a l a t e with the conglomerates. The f i n e r sediments become  more  prominent farther out into the basin, representing  a more quiescent environment of deposition. Some fine-grained water l a i d t u f f s have been found associated with the a r g i l l i t e s and probably represents ash from nearby volcanic a c t i v i t y . As the basin f i l l e d and the source area became eroded, the sediments deposited became f i n e r and finer-grained, marked by s i l t s t o n e , mudstone,  Figure '3  Idealized basin  and  Sharpstone  diagram the  of the formation  related  depositional  conglomerate  and  of  a  Triassic  sequence  Brooklyn  marine  of  limestone.  29. a r g i l l i t e sequences, o v e r l y i n g the conglomerates. Near the top of these f i n e r sediments, carbonaceous bands increase i n abundance, being t y p i c a l l y l i g h t tan coloured and m i c r o c r y s t a l l i n e with carbonaceous matter- suggestive  of shallow water  deposition under s a l i n e conditions.  The Sharpstone Conglomerate appears to be t h i c k e s t at or near Phoenix, approximately T mile west of the edge of the map sheet, where Seraphim (l956) quotes a t o t a l thickness of 2000 f e e t . A large Sharpstone Conglomerate body found immediately west of the southern P r o v i n c i a l Highway west of Baker Ridge dips moderately to gently to the east and here reaches approximately 2000-2500 feet i n thickness, w i t h some 500 feet of f i n e r mudstone and s i l t s t o n e o v e r l y i n g the conglomerate. A s i m i l a r Sharpstone Conglomerate band occurring west of the Canadian P a c i f i c Railxray tracks at the northern edge of the map area i s also approximately 1200-1500 feet t h i c k , with another 200-300 feet of f i n e s i l t s t o n e overl y i n g the conglomerate. Throughout the remainder of the area the Sharpstone sequence i s not found completely i n t a c t mostly because of block f a u l t e d contacts. The Sharpstone Conglomerate, as already mentioned, pinches out to the SE of Eagle Mountain and i n the v i c i n i t y of Goat Mountain and to the south i s probably represented by several t h i n lenses of green to brown mudstones or a r g i l l i t e s interbedded with the t h i c k e r w e l l bedded a r g i l l a c e o u s Brooklyn Limestone. These a r g i l l i t e bands seldom reach thicknesses greater than 10-20 f e e t . One block of a r g i l l a c e o u s limestone found at the western contact of the gabbro body northeast of Hardy Mountain and p o s s i b l y brought up from depth along the steep f a u l t zone shows a 40-50 foot  30. a r g i l l i t e bed between two bands of bedded a r g i l l i t e limestone. L i t t l e (1965) mentions that a f o s s i l of Middle to Upper T r i a s s i c Age was found by Thorpe w i t h i n the Rawhide Formation, which according to Seraphim (1956) occurs at Phoenix as a t h i n u n i t of l o c a l l a t e r a l extent at the base of the Sharpstone Conglomerate. This puts a maximum age of Middle to Upper T r i a s s i c f o r formation of the sharpstone basin of deposit i o n , and the author f e e l s that the shape and thickness of the Sharpstone Conglomerate sequence found i n the Grand Forks area, suggests a very short time i n t e r v a l of formation, probably w e l l w i t h i n several m i l l i o n years. Sharpstone Conglomerate lenses and bands associated w i t h o v e r l y i n g limestones, s i m i l a r to that exposed i n the Grand Forks-Eholt map area have been found i n several i s o l a t e d , discontinuous areas throughout the southern Boundary D i s t r i c t (Newell, 1969): south of B r i d e s v i l l e , some 38 miles west of Grand Forks; the Midway window and at the Deadwood Camp, west of Greenwood, B.C. are several such examples.  Dr. W.H. White  (personal communication, 1970), also mentioned s i m i l a r conglomerates w i t h i n the F r a n k l i n Camp, some 40 miles north of Grand Forks along the Granby River.  Brooklyn Limestone The Brooklyn Limestone conformably o v e r l i e s the Sharpstone Conglomerate sequence i n the map area. The contact i s g r a d a t i o n a l , cons i s t i n g of a gradual increase i n carbonate and a decrease i n a r g i l l a c e o u s matter upward i n the sequence, u n t i l f i n a l l y calcium carbonate  prevails.  This probably represents a complete inundation of the shallow N i c o l a Sea.  51. The Brooklyn Limestone Formation i n the Grand Forks-Eholt area i s d i v i s i b l e into three d i s t i n c t l i t h o l o g i c units. The lowest unit l y i n g conformably and gradationally above the w e l l bedded a r g i l l i t e s and s i l t s t o n e s of the Sharpstone white to tan rounded chert  sequence consists of a  pebbly to sandy limestone. These chert ovoids  form Seraphim's (l956, pp. 689) "Peanut B r i t t l e Limestone" and which are t y p i c a l l y well rounded, frosted, white to pale grey chert fragments, l / 8 to l/4 inch i n diameter set i n a white to tan limestone matrix and, as Seraphim noted, i s strongly suggestive that the chert ovoids are windblown pebbles: hence the term"Aeolian limestone" (Plate 5, p. 34).  Generally  the chert sand grains are evenly disseminated throughout the limestone but i n places have been found concentrated along bedding planes and sometimes as streaks along planes of high shear.  The sand grain content  generally i s about 10-15$ of the limestone, but a 60$ content has been found i n the limestone just north of the Phoenix road turn-off. Sand grain concentrations along bedding planes and cross-bedding are suggestive of strong current action, near shore, d e l t a i c depositional environment.  The frosted ovoid chert grains were probably wind lofted(?)  from a near shore dune or beach deposit. Thickness of this sandy limestone member i s quite variable but appears to be maximum near Phoenix and immediately to the east, where i t i s about 100 feet thick.  This member appears as a lens that thins r a p i d l y to  the southeast, being about 20 feet thick just north of Hardy Mountain. A 5 foot band within dark argillaceous limestone, immediately north of Hardy Creek, probably represents re-working of these chert sand grains.  32. The "aeolian limestone" appears to grade upwards into a tan to white dense microcrystalline limestone generally devoid of any primary structures. Microscopic  argillaceous matter forms about 5-10$ of this unit.  Total thickness of this unit i s unknown, but does not appear to be greater than several hundred feet thick. Limestone breccias occur within this stratigraphic unit i n several localities throughout the northern part of the map area and probably reflect slumping or cataclastic breccias associated with contemporaneous faulting within the basin of deposition. These breccia fragments are angular to sub-rounded elongate slabs, and range i n size from several inches to several feet across, but generally less than one foot. The breccia fragments are closely packed and cemented together by a finegrained carbonate matrix carrying much clay and sand-size fragments of similar composition to the larger fragments. Thicknesses of these breccias are not known but they appear to be 50 to 100 feet thick and quite restricted i n lateral extent.  A good exposure of a typical breccia can  be found along the southern Provincial Highway about one mile south of the Oro Denoro workings. The second mappable limestone unit i s a distinct continuous sequence of well banded limestone that conformably overlies the sandy and microcrystalline units.  These bands are pale buff-brown to greenish-brown and  form thin continuous layers that range i n thickness from less than l/8 inch to 6 inches, but average about one inch or less. The frequency of these bands also varies considerably.  The bands are composed, generally,  of a microcrystalline argillaceous to tuffaceous matter, very rarely  33.  cherty, vrith a minor carbonate matrix and form c h a r a c t e r i s t i c resistant ridges i n outcrop i n contrast to the less r e s i s t a n t pale buff coloured microcrystalline limestone that houses these bands (see Plate 6, p . 3 4 ) . Total thickness  of t h i s banded limestone unit i s variable through-  out the map area and appears best developed and thickest near the southern part of the map area, west of Grand Porks, between the i n t r u s i v e bodies, where i t appears to be about 1 0 0 feet thick. This thin-bedded limestone unit could very well be a t r a n s i t i o n a l or offshore f a c i e s of the nearshore fine-grained microcrystalline limestone because i n the southern part of the map area the banded limestone s i t s on top of a cross-bedded sandy limestone unit.  A thick sequence of massive to well bedded grey to black argillaceous limestone, s t r a t i g r a p h i c a l l y overlying the well banded limestone, forms the t h i r d and uppermost limestone u n i t .  Contact r e l a t i o n s with the under-  l y i n g limestones have not been observed but are presumably gradational and could be abrupt ( ? ) . A t y p i c a l argillaceous limestone, dark grey to black on a fresh surface, weathers l i g h t grey and i s composed of fine-grained to microscopic, thin,black to dark brown argillaceous laminae that p a r a l l e l bedding planes and i s set i n a microcrystalline calcareous matrix. Several large, 1 mm diameter, rounded to elongate r e - c r y s t a l l i z e d c r i n o i d stems and other b i o c l a s t i c fragments are found roughly p a r a l l e l i n g the bedding. The amount of argillaceous matter i n these carbonates i s variable.  South of  Hardy Creek and along the highway i n the lower reaches of July Creek, the  P l a t e 5'  "Aeolian limestone" or Seraphim's "Peanut B r i t t l e " limestone forming the basal section of the Brooklyn Limestone NW of Baker Ridge. Note alignment of the f r o s t e d chert ovoids.  P l a t e _6_: Brooklyn Limestone, t h i n l y bedded, w e l l banded u n i t from area immediately west of Grand Forks. Thin more r e s i s t a n t beds are tuffaceous and impure limestone.  35. limestones are t y p i c a l l y black, thin bedded, shaly and f i s s i l e , with a well developed s l a t y cleavage. I n t r a f o l i a l folds have been noted 1970).  The more massive argillaceous  (Ross,  limestones are frequently strongly  fractured and i r r e g u l a r l y veined by white to pale c a l c i t e .  Graded bedding  and numerous minor folds (Plate 13, p. 77 ) are well developed within the bedded argillaceous limestones and the banded limestones below, and almost a l l of the T r i a s s i c f o s s i l evidence l o g i c and stratigraphic u n i t s .  to  date  has come from these l i t h o -  F o s s i l locations and descriptions are  given i n Appendix I I . Total thicknesses of the Brooklyn Limestone vary considerably throughout the map area from a maximum of about 2000 feet (Seraphim, 1956)  near  the northwest corner of the map area to a minimum t o t a l stratigraphic thickness of 100-150 feet immediately south of Goat Mountain (SE corner of the map area). Here the Brooklyn Limestone i s comprised almost wholly of massive to well bedded argillaceous to shaly limestone, with a 5-8 foot bed of chert pebble to sandy limestone present near i t s eastern or lower boundary.  I t appears to l i e on a very thin veneer (25 feet thick)  of fine-grained a r g i l l i t e or water l a i d tuffaceous a r g i l l i t e which probably represents the scant presence of the Sharpstone  sequence.  This decrease i n thickness and increase i n the dark argillaceous matter within the Brooklyn Limestone sequence towards the southeast of the map boundary suggests a quiet, deep water deposition farther out into the basin of deposition. On the other hand, some of the thinning of the Brooklyn Limestone i s attributed to pre-Fragmental Andesite erosion surfaces such as that depicted by the less than 50 foot limestone band  36.  immediately east of Eagle. Mountain, and e s p e c i a l l y to the west and beneath Baker Ridge where the limestone completely pinches out to the southeast and the andesites d i r e c t l y overlie the  "Puddingstone".  In the northern part of the map area i n the v i c i n i t y of the R.Bell, Bluebell, Mt.Rose and Swallow showings, where the Brooklyn Limestone crops out i n the v i c i n i t y of i n t r u s i v e masses, the massive limestones occur as coarse to fine-grained, white r e c r y s t a l l i z e d limestone or marble.  The  limestones are generally fractured and quite granular due to r e - c r y s t a l l i zation, hence, primary structures are obscured. In the immediate v i c i n i t y of several large granodiorite or quartz-diorite masses, the Brooklyn massive argillaceous limestones occur as fine-grained hornfelsed marble. Complex c a l c - s i l i c a t e skarns intimately associated with copper mineralizat i o n throughout the Summit Camp  are found l o c a l i z e d adjacent to several  granodiorite - or quartz-monzonite Skarn  masses.  A detailed description of  and related copper mineralization i s given i n Appendix I. Present f o s s i l evidence suggests that the Brooklyn Limestone ranges  i n age from Middle to Late  Triassic.  L i t t l e and Thorpe  (l965) state a  Middle T r i a s s i c age f o r their Brooklyn Limestone equivalent on the basis that i t contains Dapjiella and that the Rawhide Formation,  conformably  below, contains Middle to Upper T r i a s s i c f o s s i l s . Upper T r i a s s i c  (Norian)  corals have been found by L i t t l e  (l965) i n a massive limestone associated  with the author's "Puddingstone"  conglomerate  the Brooklyn  which l i e s conformably below  Limestone.  In Lower July Creek, grey shales interbedded with argillaceous limestones are, according to Newell  (1969), i d e n t i c a l to the Upper T r i a s s i c  37.  pelecypod HaJ^obia •» bearing beds found some 5 miles to the south near L a n v i l l e , Washington.  The author also found s h e l l fragments that appear  to be r ^ g n e l l a or HaJ^bia w i t h i n the Brooklyn Limestone along the southern P r o v i n c i a l Highway, north of the Phoenix road t u r n - o f f . A rather t i n y , p r i m i t i v e , c e r a t i t i c ammonoid, t e n t a t i v e l y correlated with P^raEP^ajnjp^exas or Megaphyllites (Figures 9 and 10, pp. 113  , 114 )  by the author, was found i n a t h i n shaly limestone u n i t some 2500 feet south of Goat Mountain. A d e t a i l e d d e s c r i p t i o n of t h i s ammonoid i s given i n Appendix I I .  Tozer (l970, personal communication) gives an age range  of l a t e Middle T r i a s s i c (Anisian) to middle Upper T r i a s s i c (Norian) f o r Megaphyllites, which suggests that t h i s t h i n limestone u n i t i s at l e a s t a time equivalent of the Brooklyn Limestone Formation. P o s s i b l e outside c o r r e l a t i o n s may be calcareous sediments of the T r i a s s i c Slocan Group to the northeast, and the Old Tom, Shoemaker Formations of the Oliver/Keremeos area i n the southern Okanagan D i s t r i c t (Ross, 1970). The p o s s i b i l i t y e x i s t s that more than one limestone sequence makes up the Brooklyn Limestone as mapped by the author.  Several t h i n limestone  beds have been mapped at Eagle Mountain i n t e r c a l a t e d with the upper part of the Sharpstone sequence.  Several t h i n limy beds are also found w i t h i n  the upper part of the Puddingstone a r g i l l i t e s near the Phoenix t u r n - o f f . Seraphim (l956) describes several lenses of limestone b r e c c i a or angular conglomerate i n t e r c a l a t e d with h i s upper Sharpstone sequence at Phoenix. However, these u n i t s appear to be very s i m i l a r to the angular limestone cobble conglomerate or Puddingstone sequence mapped by the author to the east.  38.  Fragmental Andesites The term "Fragmental Andesite" has here been coined to include a host of clastic and massive Jurassic andesite, agglomerates, flow breccias and porphyritic andesite flows with minor tuffs and pillows. The andesites incorporate a good portion of the trachytic andesites and the pyroclastic fractions of Carswell's (l957) "Eholt Formation". For the most part these fragmental andesites unconformably over] ie the Brooklyn Limestones and Sharpstone sequence and appear to have been deposited on an uplifted erosion surface of the Triassic sediments. However, slightly altered andesite pillows overlying the limestones i n one locality suggest i n part, conformity or continuous deposition of the andesite with the Triassic sediments. Massive andesites are prevalent throughout the map area but more prominent i n the vicinity of Goat and Hardy Mountains. Here the andesites are massive, coarse to medium-grained, porphyritic, slightly trachytic, dark to moderate avocado green rocks with prominant straight blocky joint surfaces forming angular outcrops.  Laths of plagioclase phenocrysts are  typically buff to tan, generally 2 mm in length, set i n a dark green fine-grained matrix.  These laths make up about 30$ of the rock and the  remaining fine-grained matrix i s composed of about 10$ hornblende. Plagioclase phenocrysts are clouded with fine-grained sericita, epidote and minor carbonate, imparting a creamy speckled appearance i n hand specimen.  The centres of the phenocrysts are almost completely  altered - making composition determinations impossible. Chlorite, epidote,  39. and minor carbonate occurs ubiquitously throughout the fine-grained matrix, imparting the t y p i c a l pistachio to dark green colour c h a r a c t e r i s t i c of the andesites throughout the Grand Pork-Eholt area. Total a l t e r a t i o n ; c h l o r i t e , epidote, s e r i c i t e , carbonate, and minor pyrite i n places reaches as much as 30$ of the whole rock. Hornblende c r y s t a l s , found i n places making up to 20$ of the rock, can occur as subhedral grains sometimes as large as the plagioclase laths. A maroon porphyritic andesite forming a flow top underlying the T e r t i a r y Kettle River sediments at Baker Ridge carries up to 50$ plagioclase laths, 15$ f i n e l y disseminated opaques (hematite or oxidized iron) and 20$ hornblende. noted.  About 1-2$ minor quartz and potash-feldspar have been  The remainder of the rock i s composed of the a l l pervasive c h l o r i t e ,  epidote, s e r i c i t e , and carbonate, a l t e r a t i o n products. Some of the massive andesites such as i n the v i c i n i t y of Hardy Mountain are very coarse-grained (plagioclase, hornblende) and can be mistaken f o r the coarse-grained d i o r i t e s found i n several places within the map  area.  P y r o c l a s t i c or flow breccias occur, ubiquitously throughout the area and form by f a r the greater percentage of the andesites.  map  They  occur as thick p i l e s (?) that grade into the more massive andesites and no d i s t i n c t boundaries have been found.  Even the more massive andesites  under close scrutiny generally contain some minute fragments or ashy particles.  These breccias are t y p i f i e d by sub-angular  to sub-rounded  volcanic fragments of variable size, composition, and colour set i n a massive, dense to s l i g h t l y p o r p h y r i t i c fine-grained matrix (Plate 7> p . 4 l ) . The fragments range i n colour from pale grey through dark and l i g h t greens  40. to brown-green, and themselves are p o r p h y r i t i c to massive, g e n e r a l l y very s i m i l a r to the host. The s i z e of the fragments i s v a r i a b l e from large rounded boulders (Plate 8, p. 4 l ) to microscopic, but f o r the most part average about T to 1 i n c h i n diameter and g e n e r a l l y compose l e s s than 10$ of the rock. Up to 70-80$ b r e c c i a fragments have been observed i n several l o c a l i t i e s throughout the map area. The matrix surrounding the fragments i s t y p i c a l of the more massive dense andesites with a s l i g h t a d d i t i o n of glass and t u f f fragments. I n v a r i a b l y , patches of pale green epidote a l t e r a t i o n can be observed surrounding some of these fragments,  and  probably represent deuteric or autometamorphism (Plate 7, p . 4 l ) . Agglomerates have been found i n s e v e r a l l o c a l i t i e s w i t h i n the area.  map  That cropping out along the highway i n the southern reaches of  J u l y Creek i s the most spectacular (Plate 8, p. 4 l ) . Here, large rounded to oval-shaped dark green andesite cobbles up to 1 foot i n length occur t i g h t l y packed and surrounded by a much f i n e r p y r o c l a s t i c and tuffaceous matrix.  A s l i g h t f o l i a t i o n of the elongate cobbles h i n t s of flow  d i r e c t i o n s (Plate 8 ) .  The thicknesses of these c l a s t i c p i l e s are not  known but appear greater than 30 feet and probably about 50 f e e t . What appear to be p i l l o w s of s l i g h t l y a l t e r e d andesite are found at the basal part of the Fragmental Andesite sequence o v e r l y i n g the s k a r n i f i e d Brooklyn Limestone along the Canadian P a c i f i c Railway tracks north of Fisherman Creek. The p i l l o w s , r e l a t i v e l y s m a l l , s l i g h t l y elongate and about 10-14  inches i n length are f l a t t e n e d p a r a l l e l to the limestone  contact - dipping steeply to the west.  These p i l l o w s are continuous f o r  a thickness of 15 to 20 f e e t then appear to grade i n t o a dense fragmental  41.  P l a t e 7:  Typical fragmental andesite from Goat Mc n t a i n . Note several large rounded p o r p h y r i t i c fragments and the l i g h t green-yellow epidote and c h l o r i t e alteration.  •I P l a t e 8:  Spectacular andesite agglomerate outcropping along the southern P r o v i n c i a l Highway i n the J u l y Creek V a l l e y . Camera case - extreme l e f t f o r scale.  42. andesite.  Below the base of the andesite pillows numerous 1-2 foot thick  tuffaceous beds are found interbedded with the limestone.  The pillows  are indicative of subaqueous volcanic activities and probably  represent  an inpouring of andesitic lava into a carbonate basin as the pillows appear quite conformable with the underlying skarnified limestone. Fragmental Andesites are characteristic i n appearance and can quite easily be distinguished from the older Anarchist greenstones and basalts. The andesites are generally lighter shades of green, fragmental, blocky and quite massive i n outcrop, as opposed to the intensely sheared and metamorphosed Anarchist greenstones.  Stratigraphic position i s also an  indication. However, i n intensely sheared and faulted areas such as surrounding the serpentine bodies, the andesites appear as greenstones that could well be mistaken for Anarchist rocks. Such an example i s the greenstone immediately south of the serpentine body that crosses the highway south of the Phoenix turn-off. Problems arise near the northern edge of the map area where porphyr i t i c diorite or quartz-diorite intrusive rocks become prevalent. Some of these greenish coloured fine-grained feldspar-porphyry intrusions or hypabyssal intrusive rocks have a slight trachytic texture and can easily be mistaken for andesite flow rocks such as those on the western slope of Baker Ridge.  The outlier of volcanic rock overlying the Brooklyn Lime-  stone south of Oro Denoro may be a case i n point. A similar situation occurs immediately north-northeast of the Bluebell showing, where the finegrained, trachytic textured rock appears identical to the trachytic andesites underlying Baker Ridge.  A detailed petrographic study i s needed to  43. solve this problem. The total thickness of the Fragmental Andesites i s not known and appears to be quite variable. Tertiary continental sediments and volcanics unconformably overlie the top of the andesites, suggesting an erosional contact between the two.  Since the Tertiary cover i s missing i n most  places, much of the andesites may also be eroded. Baker Ridge i s one of the few places that shovsboth the top and bottom contacts and here the Fragmental Andesites are only about 500-1000 feet thick. Throughout the map area the andesites appear to be less than 2000-2500 feet thick. The general lack of stratigraphic markers and later fracturing and settling greatly hinder any thickness measurements within the andesites. The more massive andesites probably represent the centres of flows that have had time to crystallize before solidification, and the fragmental andesites or breccias probably represent flow tops or pyroclastic ejections. In several places some of the fragments are reddish-brown possibly due to oxidation of the iron content upon exposure to atmosphere. Tuffaceous matter in the matrix also indicates that exhalation processes wee involved. Some of the andesite flows must have poured into shallow carbonate depositional  basins as suggested by a thin sequence of pillows  forming the basal part of the Fragmental Andesites found overlying the limestones i n one locality.  Thin tuffaceous beds within the underlying  limestone suggest that volcanic exhalations had been present for some time before the outpouring of lava. L i t t l e and Thorpe (1965) state that these andesites megascopically resemble the Rossland Formation of Lower to Middle Jurassic age, found  44. some 35 miles to the east of Grand Forks-Eholt area. Campbell (1966) includes the Nicola volcanic and Rossland Formations i n h i s widespread Takla-Hazelton Assemblage (Late T r i a s s i c to Middle J u r a s s i c ) , and since the Fragmental Andesites of the Grand Forks area resemble the Rossland volcanics, the Fragmental Andesites may well r e f l e c t the l a t e spread of the Nicola volcanic a c t i v i t y to the southeast during Middle Jurassic time. The (Middle T r i a s s i c ) Sharpstone Conglomerate - Brooklyn Limestone sequence and overlying (Middle Jurassic) Fragmental Andesites appear to correlate with the widespread  (Middle Triassic-Middle Jurassic) Takla-  Hazelton Assemblage as described by Campbell (l966, pp.63-64). (See Figure 8,  p.  96  )  T e r t i a r y Layered Rocks Kettle River Formation Since much of the f i e l d work was spent outside the T e r t i a r y cover most of the data herein i s taken from Monger (1968) and Parker and Calkins (1964). For a detailed description of the various T e r t i a r y rock units and t h e i r relationships the reader i s referred to Monger (1968). For occurrences of Tertiary s t r a t i f i e d rocks and intrusive a c t i v i t i e s i n county N-Washington State, the reader i s referred to Parker and Calkins (1964). The Kettle River continental sediments crop  out i n three l o c a l i t i e s  within the map area, namely: Baker Ridge*, • Thimble Mountain, immediately north of Fisherman Creek} and an i s o l a t e d l o c a l i t y immediately north of Wilgress Lake.  These sediments overlie the  Mid. Jurassic  Fragmental  45. Andesites unconformably and as yet have not been found overlying rocks older than t h i s . At Baker Ridge, the Kettle River sediments and younger Marron volcanics occur i n a gently warped syncline draped over an eastward t i l t i n g block of older Andesites.  As Monger states, the Kettle  River sediments are everywhere overlain by the younger Marron volcanics, except where erosion has proceeded below the stratigraphic l e v e l of the volcanic rocks. The basal contact of the Kettle River sediments at Baker Ridge i s a depressed area and distinguishable on a e r i a l photographs. Individual flow contacts within the overlying Marron volcanics also have a pronounced topographic expression. The Kettle River sediments, according to Monger (1968), are composed dominantly of feldspathic volcanic sandstones, l i t h i c volcanic sandstones and finer-grained equivalents of these.  Minor t u f f s of i n t e r -  mediate composition (dacite) and l o c a l l y shales and conglomerates also occur. Monger's basal conglomerate i s not present at Baker Ridge where the preponderance of the Kettle River sediments are feldspathic volcanic sandstones. The feldspathic volcanic sandstones, forming the lower part of the Kettle River Formation are composed of sand-size grains,1-2 mm i n diameter, of feldspar ( i n part plagioclase i n order of A n ^ quartz.  45^'  anc  * *>ordinate su  In outcrop, the sandstone or arkose appears white to pale grey  and has much the appearance of a granite, the c l a s t i c c r y s t a l fragments being angular and fresh.  The rock i s t y p i c a l l y structureless and thick  bedded with a few feet of t u f f s and conglomerates present at a l l s t r a t i graphic l e v e l s .  The t u f f s are pale grey, dense and generally thin bedded.  46.  Conglomerates found at Baker Ridge form a 20 foot thick section, the composition of the boulders i s variable ranging from g r a n i t i c to volcanic. The upper grey to brown weathering l i t h i c volcanic sandstone unit noted by Monger (1968) appears to be missing i n the Grand Forks-Eholt map  area.  Monger c i t e s four sources f o r the derivation of the c l a s t i c Kettle River sediments: 1.  acid volcanic rocks supplying volcanic feldspars and quartz;  2.  intermediate volcanic rocks;  3.  basement rock - g r a n i t i c d e t r i t u s ;  4.  intraformational shales supplying shale chips;  and the p o s s i b i l i t y of conglomerates formed from contemporaneous f a u l t i n g has been  suggested.  The l o c a l r e l i e f at the time of formation must have been considerable judging from the size of conglomerate boulders,and  the rate of accumula-  tion must have been rapid judging from the r e l a t i v e angularity of the c l a s t i c fragments and the thickness of the i n d i v i d u a l beds. The thin shale sequences probably represent l o c a l intraformational  shallow(?) depositional  basins. Contemporaneous f a u l t i n g probably aided to the continual u p l i f t i n g of the source areas. Monger believes the o r i g i n a l thickness of the Kettle River sediments to be about 2000 feet i n the southern part of the Boundary D i s t r i c t , but only about 1,200  feet i s present at Baker Ridge, and much less throughout  the remainder of the map area. LeRoy (1912) estimates a thickness of only 260 feet at Phoenix, to the west. Both plant f o s s i l s and radiometric ages indicate that the Kettle  47. River Formation i s of Kiddie Eocene age and Monger (l968) c i t e s various l i n e s of evidence f o r t h i s . C l a s t i c rocks of E a r l y T e r t i a r y age, l y i n g unconformably on top of p r e - T e r t i a r y rocks, crop out i n r e l a t i v e l y small i s o l a t e d areas across much of south-central B r i t i s h Columbia, and northern Washington. Equivalent rocks have been described as f a r north as the F r a n k l i n Camp, some 30 miles north of the c i t y of Grand Forks (Drysdale, 1915). In northern Washington, Parker and C a l k i n s (1964), have demonstrated the presence of Eocene(?) p y r o c l a s t i c and sedimentary rocks c a l l e d the O'Brien Creek Formation as f a r as 50 miles south of the Grand Forks map area and consider them roughly equivalent to the K e t t l e R i v e r Formation. Church (l967 s  p.  25) i n d i s c u s s i n g possible c o r r e l a t i o n s to the E a r l y T e r t i a r y Springbrook Formation from the White Lake area i n the Southern Okanagan D i s t r i c t , mentioned: K e t t l e River Formation  - (Midway area)  Curry Creek Formation  - (Beaverdell area)  Coldwater Formation  - (Kamloops area)  Allenby Formation  - (Princeton area)  O'Brien Creek Formation  - (Republic area, N. Washington S t a t e ) .  Marron Volcanic Formation The author uses the terminology applied by Monger (l968) and the Marron Formation incorporates the Midway Volcanic Group (Daly, 1912), and the Phoenix Volcanic Group ( L i t t l e , 1957).  Again the reader i s r e f e r r e d  to Monger (1968) f o r a more d e t a i l e d account on the Marron Formation i n  48.  the Boundary District. No attempt was made i n the f i e l d to subdivide the Tertiary volcanic rocks of the area. This has been done in some detail by Parker and Calkins (1964) i n northern Washington and recently i n the Greenwood map area to the east, by Monger ( l 9 6 8 ) . Within the Greenwood map area, the Marron Formation i s a well s t r a t i fied sequence of extrusive rocks of porphyritic andesite to trachyte composition, with minor intercalated beds of pyroclastic material. Basalt i s present locally. Near Grand Forks, the Marron Formation occurs at several localities as an east-dipping succession of flow rocks lying conformably on top of the early Tertiary Kettle River sediments; as at Baker Ridge. At Thimble Mountain, Marron volcanics directly overlie the folded Triassic sediments with marked disconformity and i s believed in faulted contact. Several other outcrops of Tertiary volcanic rocks are found in the vicinity of Wilgress Lake that have been mapped as Marron Formation. Division 4A which forms the lower division of Monger's Marron Formation, i s composed predominantly of sodic trachytes approaching phonolite in composition. A l l are porphyritic and phenocrysts of feldspar are i n variably anorthoclase and/or orthoclase. Monger recognizes 5 main lithologic varieties i n division 4A. They are i n order of decreasing age: 1.  basal lavas, local flow breccias and agglomerates;  2.  pyroxene-feldspar porphyry and pyroxene-feldspar rhomb porphyry;  3.  dark analcite bearing rhomb porphyry;  4.  fine-grained feldspar porphyry.  The pyroxene-feldspar  porphyry i s the most common lithologic type  49. i n Monger's d i v i s i o n 4A and forms much of the lower part of the Marron Formation. Similar rocks occur at Baker Ridge d i r e c t l y overlying the Kettle River sediments. Here the lower contact i s not v i s i b l e and /occupies a depression that may well s i g n i f i y a basal flow breccia or agglomerate. The pyroxene phenocrysts are stubby, euhedral, dark green, and generally about 5 mm long. In thin section they are colourless to very pale green and have abnormally high birefringence f o r common augite. Some pyroxenes enclose small apatite euhedra or opaque mineral grains, and some mantle feldspars.  The potash-feldspar phenocrysts are generally  smaller than the pyroxenes and are generally zoned with a core and mantle of d i f f e r e n t composition. The cores are p a r t l y altered to carbonate and/ or s e r i c i t i c white micas and numerous minute opaque inclusions, whereas the  mantles are f a i r l y clean. Twinning i s not common. B i o t i t e has been  noted as small euhedra. Amygdaloidal volcanic rocks, found l o c a l l y by Monger, has also been noted at Baker Ridge and the v e s i c l e s pinkish  are here f i l l e d with a white to  zeolite(?).  The o r i g i n a l thickness of the Marron volcanics i n the Grand Forks area i s unknown since the upper surface i s erosional, however a maximum thickness of about 6000 feet has been mapped by Monger (l968) just west of Greenwood, B r i t i s h Columbia.  The Marron volcanics at Baker Ridge have  an apparent thickness of about 4000-5000 feet. Evidence f o r the base of the Marron Formation being synonymous (diachronous) with the top of the Kettle River Formation has been c i t e d  50. by Monger (1968). He also states that the middle part of the Marron Formation i s of Middle Eocene age based on plant f o s s i l s c o l l e c t e d by W.H.  L i t t l e and a radiometric age of 49+2 M. years from Mathews ( l 9 6 3 )  and 48+2 M. years on a syenite porphyry s i l l i n t r u s i v e i n t o K e t t l e River sediments. Monger believes that the syenite porphyry i n t r u s i v e i s equivalent to the trachy - andesites of h i s Middle D i v i s i o n (4B). The T e r t i a r y v o l c a n i c rocks described by Monger ( l 9 6 8 ) , from the Boundary D i s t r i c t have been c o r r e l a t e d with volcanic rocks of mid.-Eocene age widely dispersed across southern B r i t i s h Columbia, and according to Church ( 1 9 6 7 ) , are comparable to the type s e c t i o n f o r the Marron Formation at the White Lake area i n the southern Okanagan D i s t r i c t . Church also states that the ages of the "Midway Group" (a T e r t i a r y v o l c a n i c s e c t i o n found several miles west of the Grand Forks map area, that resembles the Marron Formation) c o r r e l a t e s with v o l c a n i c rocks of the Kamloops and Princeton Groups, based on Potassium-Argon ages from Mathews ( 1 9 6 4 ) . E a r l y T e r t i a r y (Eocene?) v o l c a n i c rocks extending over a wide area i n northern Washington and termed "Sanpoil Volcanics" by Parker  and  C a l k i n s (1964) have been equated by Monger to h i s Upper D i v i s i o n (4C) of the Marron Formation.  51. B. SERPENTINITES  Serpentinized ultramafic bodies i n the Grand Forks-Eholt area occur t y p i c a l l y along northwest  trending, steeply dipping shear/fault zones  (Plate 9, p. 53). They form elongate, rounded, intensely sheared bodies that p a r a l l e l the steeply dipping f a u l t zones and i n some of the larger bodies where the outer edges of the ultramafic body i s intensely sheared, a characteristic dark to pale green polished surface or f i s h scale serpentine i s well developed. The central core of the larger bodies are generally massive, less sheared and composed of a dark green t o black dense matrix with several p a r t i a l l y serpentinized r e l i c s of o r i g i n a l pyroxene c r y s t a l s (bastites?) present. The dense matrix i n most cases i s a microscopic f e l t e d serpentine mass. Serpentine bodies cropping out i n the v i c i n i t y of limestones contain mariposite, magnesite, t a l c , dolomite and other carbonate a l t e r a t i o n products (Parker and Calkins, 1964).  Some of these minerals were found  by the author associated with a serpentinite southeast of Hardy Mountain. A large serpentinized pyroxenite body crops out along the P r o v i n c i a l Highway near the headwaters of July Creek, south of the Phoenix road turn-off.  This large northwest  trending body i s composed almost wholly  of large 4 inch long blades of dark green pyroxene intergrowths that have been fractured and p a r t i a l l y serpentinized; minor c h l o r i t e has been noted along c r y s t a l faces.  The outer edges of t h i s body i s also intensely  sheared and serpentinized. Serpentinite and pyroxenite bodies i n the Grand Porks map  area  weather a c h a r a c t e r i s t i c dun to dark brown to sometimes black-green colour  52. and are devoid of vegetation except f o r moss, grasses, and lichens, providing e a s i l y mappable shear zone and f a u l t trend.  A l l of these  serpentinites and pyroxenites are strongly magnetic and should show up on aero-magnetic maps of the area. Several large northwest trending serpentinized ultramafic bodies have been mapped by Parker and Calkins  (1964), west of Danville,  Washington, south of Grand Porks, that carry carbonate and quartz veins The serpentinite mass about 5000 feet west  with galena mineralization.  of Hardy Mountain, contains several v e r t i c a l easterly-trending small quartz and carbonate veins with very minor galena mineralization. According to Parker and Calkins  (1964) these serpentinites are  interpreted as having originated from an ultramafic i n t r u s i v e , suggested by the presence of r e l i c t outlines of o r i g i n a l c r y s t a l s , fractures f i l l e d with serpentine, and the presence of chromitiferous magnetite(?) and pods of chromite. L i t t l e  (1957) states that the serpentinized u l t r a -  basic bodies intrude rocks of Late Paleozoic to Jurassic age and i n turn are themselves cut by granodiorites and related rocks of the Nelson intrusion.  No d i r e c t evidence f o r the age of these serpentinites was  found by the author, but Parker and Calkins  (l964, p.36) c i t e several  convincing reasons from other areas that suggest a Late T r i a s s i c age f o r t h e i r i n i t i a l intrusions.  They state that"commonly however, the exposed  serpentines ... are i n sheared contact with Upper T r i a s s i c rocks and these bodies are considered to be " d i a p i r i c " intrusions  or  "water melon seed" type cold i n t r u s i v e ultramafic bodies that have been squeezed up along deep f a u l t zones subsequent to the i n i t i a l intrusions.  ^  P l a t e 9:  "*•»» '* '  Intensely sheared, steeply dipping s e r p e n t i n i t e body found w i t h i n a N¥ trending f a u l t zone northeast of Hardy Mountain.  54.  The s e r p e n t i n i t e s i n the Grand Forks-Eholt  area e x h i b i t such sheared  contacts with rocks as young as the Eocene K e t t l e River sediments and appear t y p i c a l of d i a p i r i c i n t r u s i o n s . This suggests that the steeply dipping f a u l t zones containing these serpentine bodies have been i n t e r m i t t e n t l y a c t i v e up to Middle T e r t i a r y time.  C.  INTRUSIVE ROCKS  Nelson Intrusions Intrusive  g r a n i t i c rocks, defined by L i t t l e (l957) as Nelson  I n t r u s i o n s , occur as several large bodies w i t h i n the northern part of the map  area and consist predominantly of coarse-grained  sub-porphyritic q u a r t z - d i o r i t e or g r a n o d i o r i t e . One occurs as a tongue of coarse-grained  equigranular  to  such large body  granodiorite i n the v i c i n i t y of the  Oro Denoro and Emma working that appears to extend westward towards the great expanse of s i m i l a r granodiorite rocks north of Greenwood. Several smaller i s o l a t e d plugs of Nelson granodiorite have been found i n the southern and middle parts of the Grand Porks area, a marked contrast to the vast expanse of Nelson i n t r u s i v e rocks that L i t t l e (1957) has mapped to the north, and probably i n d i c a t e s the dwindling e f f e c t s of Nelson a c t i v i t i e s southward i n t o the Grand Porks area. One  such small  granodiorite plug i s found about 3000' northwest of Eagle Mountain. The most abundant rock type w i t h i n the map coarse-grained,  area i s a l e u c o c r a t i c  s l i g h t l y sub-porphyritic, hypidiomorphic-granular  g r a n o d i o r i t e . M i c r o s c o p i c a l l y the rock c o n s i s t s of:  55. 44$  tabular, zoned plagioclase, composition averaging about An. 40 rt  20$  small anhedral orthoclase grains  15$  large rounded quartz  10$  prismatic black hornblende  5$  grains  b i o t i t e altered to c h l o r i t e and  epidote  and about 1% combined magnetite and p y r i t e . The hornblendes are elongate prismatic, can reach 1 cm i n length, and i n some cases impart a s l i g h t porphyritic texture to the granodiorite.  Feldspars are i n most  cases strongly altered to s e r i c i t e , white mica and minor carbonate and epidote, probably representing deuteric a l t e r a t i o n . Minor chalcopyrite was  found along small j o i n t s cutting the granodiorite i n t r u s i v e north  of Brown Creek. A dark, f i n e to medium-grained d i o r i t e border phase of the granod i o r i t e i s found i n several l o c a l i t i e s along the granodiorite contact west of the Oro Denoro workings. Previous workers have considered rock unit a more massive coarse-grained  this  part of the Fragmental Andesite  u n i t s , but the author believes that such a close association to the granodiorite contact and a separation from other areas underlain by i n t e r mediate and basic volcanic rocks, indicates some genetic r e l a t i o n s h i p and probably represents a contaminated border phase. The d i r o i t e i s mapped as a distinct unit. Nelson granodiorites are found cutting a l l rocks Middle Jurassic and older i n the Grand Forks area. Immediately north of Grand Forks, a granod i o r i t e body cuts through the Grand Forks gneisses. The large granodiorite body mentioned west of the Oro Denoro workings intrudes Brooklyn Limestone,  56. Sharpstone Conglomerate and greenstones.  sequence and Anarchist meta-cherts, meta-argillites  The small granodiorite plug northwest of Eagle Mountain  cuts the Lower to Middle Jurassic Fragmental Andesites, and hence the Kelson granodiorite appears to be post Middle Jurassic i n age. Parker and Calkins  (1964) assign a Late Jurassic to Middle Cretaceous age to similar  Nelson-type i n t r u s i v e s i n northern Washington State. Recent radiometric studies by S i n c l a i r et a l  (1968), have determined the emplacement of the  northern part of the Nelson Batholith at about 160 M. years (at the base of Upper J u r a s s i c ) . The granodiorites found i n the Grand Forks-Eholt area appear i d e n t i c a l to the Greenwood stock to the west, mapped as a Nelson i n t r u s i o n by L i t t l e (1957, 1965).  W. Livingstone (1970, personal communication)  mentioned that the so-called Nelson granodiorites from the Grand Forks area appear to be i d e n t i c a l to rocks mapped by L i t t l e as the West Kettle Batholith i n the v i c i n i t y of Beaverdell, some 30 miles west of Grand Forks.  V a l h a l l a Intrusions V a l h a l l a Intrusions are also medium to coarse-grained plutonic rocks, but are generally more acid than the Nelson i n t r u s i v e s . Granites and quartz-monzonites predominate and leucocratic v a r i e t i e s are abundant. V a l h a l l a i n t r u s i v e s can be distinguished from Nelson by the presence of smoky  quartz, r a r i t y of hornblende and an allotriomorphic granular texture,  generally porphyritic ( L i t t l e , 1957). V a l h a l l a rocks are found i n only two l o c a l i t i e s within the map area. An extremely small outcrop of very coarse-grained granite crops out about  57. mile south of Oro Denoro along an abandoned r a i l r o a d grade. Here the coarse-grained granite has sheared contacts with the surrounding Brooklyn Limestone. A large i n t r u s i v e body found occupying the Granby Valley immediately east of Fisherman Creek, about 3-4 miles north of Grand Forks, i s believed related to the V a l h a l l a intrusions because of i t s very coarsegrained allotriomorphic texture, roughly g r a n i t i c composition (although closer to a syenite) and the pink colouration of the orthoclase. However, t h i s i n t r u s i v e could well be a syenite s i m i l a r to the coarse-grained T e r t i a r y i n t r u s i v e s found by Parker and Calkins (l964) i n Curlew county northern Washington. L i t t l e (1957) states that the V a l h a l l a i s gradational with and cross-cuts the Nelson Intrusives.  Therefore i t has here been assigned  a Late Jurassic age f o r emplacement, similar to the age of the northern part of the Nelson Batholith ( S i n c l a i r et a l . , 1968). Because of the s c a r c i t y and minute size of the exposures of V a l h a l l a i n t r u s i v e s i n the Grand Forks area, they have been mapped with the Nelson i n t r u s i v e s by the author, knowing that i n a more detailed p e t r o l o g i c a l study these two rock types could be separated.  D i o r i t e s and Gabbros This map unit includes various f i n e to coarse-grained dark basic rocks of variable ages and of obscure r e l a t i o n s to other igneous rock types i n the area. They have been mapped together as a l i t h o l o g i c unit and contain basic rocks of variable compositions and probably r e f l e c t several i n t r u s i v e a c t i v i t i e s . They occur as numerous sirall d i o r i t e dykes  58. and plugs scattered throughout the map area - g e n e r a l l y more prominant i n the south; as a large northwest elongate, somewhat sheared,  leucogabbro  body c l o s e l y associated with a s e r p e n t i n i t e f i l l e d northwest f a u l t zone centered about the middle of the map area, south of Baker Ridge; and as a dark medium-grained massive d i o r i t e forming the border phase(?) of the Nelson g r a n o d i o r i t e near the Oro Denoro workings. As p r e v i o u s l y mentioned i n d i s c u s s i n g the Nelson i n t r u s i o n s , a medium to f i n e - g r a i n e d dark green d i o r i t e crops out south of the Ore Denoro workings and i s believed to be a border phase of the Nelson g r a n o d i o r i t e . S i m i l a r dark, f i n e to coarse-grained, sheared rocks have been noted at various l o c a t i o n s along both the southern and northern contacts of the large g r a n o d i o r i t e body.  Previous workers had mapped  such dark rocks as a coarser phase of the J u r a s s i c basic and intermediate v o l c a n i c s u i t e found i n the area, but these d i o r i t e s do not appear to carry the t y p i c a l p r o p y l i t i c a l t e r a t i o n , c h a r a c t e r i s t i c of the v o l c a n i c s u i t e , and a l s o they appear r e s t r i c t e d to the g r a n o d i o r i t e contacts and d i s p l a y i n t r u s i v e contacts i n places. The freshness i n hand specimen, on the other hand, may suggest a s s o c i a t i o n with some T e r t i a r y basic dykes found to the east. A large,east-west,elongate,coarse-grained d i o r i t e body d i s p l a y i n g c h i l l e d margins and i n t r u s i v e contacts outcrops w i t h i n the large t r a c t of limestone west of Grand Porks. Near the centre of t h i s body the rock i s i n t e n s e l y f r a c t u r e d i n a north-west d i r e c t i o n . Several small northeast trending dykes were found w i t h i n f a u l t zones immediately south of t h i s d i o r i t e body.  Conformable contacts with the bedded limestone at the  59.  eastern contact may suggest that these coarse-grained d i o r i t e s are i n fact coarser-grained massive volcanic flows associated with the Mid. Jurassic intermediate volcanics that o v e r l i e the Brooklyn Limestone i n the area. Approximately  1000 feet north of Hardy Mountain, a small plug of  medium to coarse-grained d i o r i t e containing well formed euhedral plagioclase c r y s t a l s has been mapped,and appears very similar to the coarsegrained massive andesites extending f o r some 1000 feet to the southeast. This d i o r i t e plug may i n f a c t be g e n e t i c a l l y related to the andesites and may represent a feeder dyke to the andesite volcanic p i l e overlying the Triassic  Brooklyn Limestone. Because of the large quantity of p r o p y l i t i c  a l t e r a t i o n associated with the andesites, i t i s very d i f f i c u l t to compare textures and compositions with the d i o r i t e s which also contain some a l t e r a t i o n products. A large 30-40 foot wide, r e l a t i v e l y unfractured northwest  trending  dark d i o r i t e dyke occupies a large f a u l t zone west of Eagle and Hardy Mountains.  The d y k e - f i l l e d f a u l t zone appears to be the southern  extension of a major f a u l t mapped by L i t t l e (l965, p.60) that 11  has been traced from near Phoenix, where i t marks the northern boundary of the Snowshoe orebody, southeastward ... ".  This f a u l t , according to L i t t l e , i s pre-Tertiary and i s "partly occupied by dykes of T e r t i a r y d i o r i t e " . In the v i c i n i t y of Eagle Mountain, t h i s d i o r i t e i s coarse-grained, s l i g h t l y p o r p h y r i t i c with large well developed quidimensionalpotash-feldspar phenocrysts set i n a fine-grained matrix of anhedral plagioclase, potash-feldspar, and b i o t i t e intergrowths.  The  e-  60. term d i o r i t e , used f o r t h i s T e r t i a r y dyke, emphasizes the dark colour of the rock, but the d i o r i t e may w e l l approach monzonite and syenite i n composition.  This Monz/no-or Syeno-diorite probably represents a more  contaminated  southern v a r i e t y of the T e r t i a r y C o r y e l l syenites found to  the north. A large northwest elongate, f i n e to coarse-grained gabbroic i n t r u s i v e body occupies the c e n t r a l part of the map Mountain and Baker Ridge.  sheet, between Hardy  This "gabbroic" body becomes coarser grained  towards i t s centre, the g r a i n s i z e of the medium-grained border phase being about 1 mm and the coarse p l a g i o c l a s e s w i t h i n the c e n t r a l part of the body have been measured up to 2 cm. across the elongate d i r e c t i o n . A composition of about 50$ white to pale grey p l a g i o c l a s e and  50$  dark green to black hornblende imparts a c h a r a c t e r i s t i c mottled or s a l t and pepper appearance to t h i s gabbro i n hand specimen (see P l a t e 10, p.53).  The rock i s roughly e q u i g r a n u l a r , s l i g h t l y f o l i a t e d i n places and  the p l a g i o c l a s e s are rounded to embayed i n o u t l i n e with the  hornblendes  g e n e r a l l y forming i r r e g u l a r i n t e r s t i t i a l intergrowths. The p l a g i o c l a s e s , t y p i c a l l y unzoned, are i n most places s l i g h t l y aligned and bent or broken, strongly i n d i c a t i v e of some movement subsequent to c r y s t a l l i z a t i o n .  The  p l a g i o c l a s e s are a l s o clouded with white-mica and c a l c i t e a l t e r a t i o n products making composition determinations v i r t u a l l y impossible. Hornblendes have been found l o c a l l y almost completely a l t e r e d to c h l o r i t e and epidote, forming a complete f i b r o u s f e l t e d mass. The intense a l t e r a t i o n of both the p l a g i o c l a s e s and hornblendes, plus the broken and bent nature of these p l a g i o c l a s e s , the s l i g h t f o l i a t i o n ,  61.  and the numerous quartz and carbonate f i l l e d fractures found roughly p a r a l l e l i n g the northwest  sheared contact d i r e c t i o n s , strongly suggest  movements within the gabbroic body contemporaneous with and subsequent to the cooling history of the gabbro, and probably r e f l e c t intermittent movements along the steeply dipping shear/fault zone within which t h i s gabbro l i e s (see Figure 6, p. 83). Near the middle and at i t s western edge, the gabbro was found with i n t r u s i v e contact into a sheared serpentinite.  Farther to the north a serpentine body was found within a  sheared zone cutting northwesterly across the gabbro. These f a c t s strongly suggest that the gabbro was emplaced contemporaneously with the development of the large northwest  trending shear zone, and that subse-  quent movements along t h i s f a u l t zone body.  have sheared some of the gabbroic  The gabbro i s believed to be Latest Cretaceous or Early T e r t i a r y  i n age. The gabbroic mass i s bounded on both the west and east sides by northwest  trending f a u l t zones containing serpentinite bodies. Both  a r g i l l i t e s and limestones i n contact with the southern part of this gabbroic body, east of Hardy Mountain, have been hornfelsed somewhat. The limestone appears to be s i l i c i f i e d i n several places. Using Williams,Turner,and G±lbert>s(1954, p.106) c l a s s i f i c a t i o n , t h i s gabbro has the c h a r a c t e r i s t i c s of both a d i o r i t e and a gabbro: i t s colour index i s approximately 50 - within the l i m i t s of d i o r i t e ; i t contains hornblende as i t s p r i n c i p a l mafic constituent - as a d i o r i t e ; but a rough composition determination of the plagioclases gives A n ^ 54 ~ wit* range of gabbro.  Williams, Turner,and G i l b e r t (1954), state that  1111  the  62.  such borderline rocks could be termed e i t h e r ."meladiorites" or "leucogabbros".  The author prefers "leucogabbro" to emphasize the  p e c u l i a r b i m i n e r a l i c composition, the large g r a i n s i z e , and the l i g h t coloured mottled appearance i n outcrop, so very d i s t i n c t i v e from d i o r i t e s i n the map area. Ages of these dark basic rocks are quite v a r i a b l e , but i t appears from t h e i r close a s s o c i a t i o n to the northwest and northeast steeply dipping f a u l t zones and T e r t i a r y f r a c t u r e  system, that most of these  basic rocks are probably Late Cretaceous or E a r l y T e r t i a r y i n age. Movements have occured along some of these f r a c t u r e zones subsequent to s o l i d i f i c a t i o n of the i n t r u s i v e rocks. The d i o r i t e s occurring as plugs w i t h i n the Fragmental Andesites and representing feeder dykes are probably of Middle J u r a s s i c age. The dark d i o r i t e border phase of the Nelson granodiorite i s probably lowest Upper J u r a s s i c i n age.  T e r t i a r y Intrusions T e r t i a r y igneous rocks w i t h i n the map area are quite widespread and v a r i a b l e i n composition, age and s t r u c t u r a l h a b i t a t . They can be divided i n t o two d i s t i n c t mappable u n i t s : 1.  Feldspar porphyry quartz-monzonite: predominantly i n the southern part of the map area and occurring t y p i c a l l y as e a s t e r l y trending dykes and l a r g e r masses, that are equivalent to Parker and C a l k i n ' s "Scatter Creek Formation". Also included  63.  i n t h i s u n i t i s Carswell's  (1957)  "Emma I n t r u s i o n s " , or  q u a r t z - d i o r i t e and r e l a t e d quartz-monzonite f e l d s p a r found predominantly i n the northern part of the map  porphyries, area. A  small a l a s k i t e dyke has also been included i n t h i s u n i t . 2.  The  second and apparently younger rock u n i t i s a complex-  sequence of syenites known as the " C o r y e l l I n t r u s i v e s " (Monger, 1968), and includes syenite porphyries, f e l d s p a r , b i o t i t e , c l o t porphyries, f e l d s p a r rhomb porphyries as dykes and  and p u l a s k i t e s occurring  sills.  Scatter Creek Formation The  "Scatter Creek" f e l d s p a r porphyry quartz-monzonites found i n  the Grand Forks area are v a r i a b l e i n texture and composition. The  quartz-  monzonite i s f i n e - g r a i n e d and strongly p o r p h y r i t i c with abundant white prismatic p l a g i o c l a s e c r y s t a l s , black b i o t i t e c r y s t a l s , with minor hornblende and c h l o r i t i z e d augite g r a i n s , and rounded c l e a r quartz grains.  These p o r p h y r i t i c c r y s t a l s are set i n a moderate grey dense  groundmass ( P l a t e 11, proportions  p. 6 8 ) .  This groundmass i s composed of varying  of m i c r o c r y s t a l l i n e c h l o r i t e , b i o t i t e , f e l d s p a r and  quartz.  The p l a g i o c l a s e phenocrysts, commonly euhedral and zoned, reach lengths of 3 mm. 5 mm.  The f e l t e d or m i c r o - g r a n i t i c groundmass i s g e n e r a l l y l e s s than P l a g i o c l a s e , both phenocryst and groundmass, i s andesine i n  composition and c o n s t i t u t e s about 30-60$ of the rock. Orthoclase i s confined to the groundmass and commonly forms graphic intergrowths quartz (Parker and C a l k i n s , 1964).  with  Most of the quartz i s also r e s t r i c t e d  to the groundmass and g e n e r a l l y forms less.than 5-10$  of the rock.  64. Irregular b i o t i t e s also occur as a common accessory and augite and hornblende has been noted within the groundmass. Minor accessory minerals include apatite, sphene, magnetite, pyrite and zircon. The plagioclase i s incipie.ntly altered to s e r i c i t e , and c h l o r i t e and carbonate has been found as deuteric alteration products from augite and  hornblende.  The Scatter Creek cuartz-monzonite porphyries are abundant within the Republic Graben (Parker and Calkins, 1964). However, similar i n t r u s i v e rocks are found cropping out i n only a few l o c a l i t i e s i n the southern part of the Grand Forks map area and occur as small easterly trending dykes and irregular masses.  Due west of Grand Forks, a large  i r r e g u l a r elongate mass cuts across the T r i a s s i c Sharpstone Conglomerate/ Brooklyn Limestone contact.  Intrusive contacts are sharp and contact  thermal metamorphism i s weak. The surrounding rocks are hornfelsed f o r approximately 20-30 feet.  Similar easterly trending v e r t i c a l dykes are  found south of Hardy and Eagle Mountains that appear to continue f o r some two miles to the east. Direct relationships between the quart-monzonite  feldspar porphyry  "Scatter Creek Formation" and the Coryell syenites have not been found i n the Grand Forks area. However, Parker and Calkins (1964) believe the "Scatter Creek Formation" to be Eocene to Oligocene i n age, since it  has  been  found cutting Kettle River and Marron volcanic equivalents  i n northern Washington. This suggests a contemporaneous age with the C o r y e l l i n t r u s i v e s i n the southern Boundary D i s t r i c t .  Fine to medium-grained quartz-monzonite  and quartz-diorite porphyries  65. that are s i m i l a r to and include Carswell's  (1957) "Emma Intrusions" form  numerous small i r r e g u l a r masses cutting the T r i a s s i c and Jurassic sedimentary and volcanic rocks, i n the northern part of the map  area.  Their texture i s generally porphyritic, with light-coloured, strongly altered euhedral plagioclase c r y s t a l s occurring as phenocrysts.  These  phenocrysts are so strongly altered to fine-grained white mica and carbonate that the o r i g i n a l character of the c r y s t a l s i s obscure, and also imparts a pale cream to l i g h t greenish colouration that t h i s unit i n hand specimen.  characterizes  The plagioclase phenocrysts are s l i g h t l y  elongate, generally average 2-3  mm  i n length and comprise up to 20$  of  the rock i n some of the finer-grained v a r i e t i e s . The groundmass consists of varying amounts of plagioclase, quartz, b i o t i t e , hornblende(?), c h l o r i t e and accessory magnetite forming a dark fine-grained denee matrix. The mafics are somewhat c h l o r i t i z e d . Carswell  (1957) states that the plagioclase i s andesine i n composi-  t i o n and he suggests a genetic association with basic rocks. This  quartz-  d i o r i t e porphyry unit has been found adjacent to every major copper magnetite skarn prospect i n the Summitt Camp, except f o r Oro Denoro. Age  r e l a t i o n s of these quartz-diorite and quartz-monzonite feldspar  porphyries  are obscure. However, i n several places these i n t r u s i v e s have  been found cutting the Middle Jurassic Fragmental Andesites and i n turn themselves intruded by the younger Coryell syenites and pulaskite dykes and are therefore  post-Middle Jurassic to pre-Eocene i n age.  Since  these feldspar porphyry i n t r u s i v e s contain abundant p r o p y l i t i c a l t e r a t i o n products, i t i s believed these i n t r u s i v e s were emplaced p r i o r to the  66.  termination of the regional metamorphic e f f e c t , possibly Cretaceous and even Early T e r t i a r y age. However, autometamorphism could also have produced t h i s low grade of a l t e r a t i o n . The quartz-monzonite  and quartz-diorite feldspar porphyry masses  occur close to or along major s t r u c t u r a l breaks and appear i n areas of maximum displacements and deformation. In several l o c a l i t i e s the intense pale a l t e r a t i o n of the plagioclases, the o v e r a l l moderate green colouration of the matrix and a s l i g h t f o l i a t i o n of the plagioclase phenocrysts impart a strong resemblance d i o r i t e porphyries to the altered, trachytic immediately east of the B l u e b e l l Showing).  of these quartz-  Fragmental Andesites (e.g. This s t r i k i n g resemblance  may  well emphasize Carswell's (1957) b e l i e f that these quartz-diorite porphyr i e s have a genetic r e l a t i o n to basic rocks.  Coryell Syenites and Pulaskite Dykes  Abundant C o r y e l l i n t r u s i v e units i n the Grand Forks area consist of a complex sequence of f i n e to medium-grained syenites and include, i n part, the i n t r u s i v e equivalents to Monger's (1968) Marron volcanics and hypabyssal dykes, sheets, and flows of pulaskite, phonolite and syenite porphyries. Monger (1968, p.27-32) r e l a t e s these C o r y e l l syenites to the Middle and Upper D i v i s i o n of the Marron Volcanic Formation. A syenite porphyry forms the most abundant i n t r u s i v e unit of the C o r y e l l Complex within the Grand Forks area and i s c h a r a c t e r i s t i c a l l y brownish-pink i n colour with approximately 10$ of the rock as feldspar phenocrysts and the remaining 90$ of the rock composed of a f i n e l y  67. c r y s t a l l i n e groundmass. This rock has a " c l o t porphyry texture" (Monger, 1968), with c l o t s , or small white p l a g i o c l a s e l a t h s generally arranged r a d i a l l y about a b i o t i t e nucleus (see Plate 12, p. 68).  The s i z e of  p l a g i o c l a s e phenocrysts i s quite v a r i a b l e , and i n some cases the b i o t i t e s are also of phenocryst s i z e . The groundmass i s f i n e l y  crystalline  and  composed of a randomly oriented mesh of p l a g i o c l a s e feldspar l a t h s , with i n t e r s t i t i a l opaque minerals, quartz and c h l o r i t e ; clinopyroxene  and  b i o t i t e c r y s t a l s also occur i n the groundmass. The p l a g i o c l a s e i n the coarser-grained  v a r i e t i e s are generally clouded with f i n e micaceous and  carbonate a l t e r a t i o n and the clinopyroxenes chlorite.  are somewhat a l t e r e d to  The dark b i o t i t e s on the other hand are generally clean  and  unaltered. A v a r i e t y of t h i s c l o t porphyry has been found containing large c l e a r to pink, zoned, elongate p l a g i o c l a s e l a t h s set i n a pale brown extremely fine-grained matrix containing small specks of dark biotite. Monger, (1968, p.30)  states that:  "pulaskites or a l k a l i c syenites are merely a v a r i e t y of the above syenite, characterized by i t s aphanitic fawn to buff matrix and appears to occur only i n the smallest i n t r u s i v e bodies". This also applies i n the Grand Porks area where the p u l a s k i t e s occur i n dykes and s i l l s that are the southernmost extensions of the C o r y e l l syenites. Numerous northwest trending dykes are found i n the northern part of the map  area.  M i c r o s c o p i c a l l y , the p u l a s k i t e i s composed of small l a t h s and phenoc r y s t s of p e r t h i t e and c r y p t o p e r t h i t e ; phenocrysts of a l b i t e ; nepheline  68.  CENTIMETERS  2  Plate 11:  Coarse-grained quartz-monzonite porphyry (Scat ter Creek Formation?) from e a s t e r l y trending dyke at Eagle Mountain.  Plate 12:  C o r y e l l syenite " c l o t porphyry" v a r i e t y from east of Wilgress Lake.  69.  as i n c l u s i o n s i n e a r l y minerals; b i o t i t e , hornblende,  riebeckite,  a e g i r i n e - a u g i t e , magnetite; rare i n t e r s t i t i a l quartz and very rare pigeonite (Monger, 1968). The f e l d s p a r s are clouded and s t r o n g l y a l t e r e d to micaceous minerals and the mafic minerals a l s o appear s l i g h t l y a l t e r e d . The fawn c o l o u r a t i o n appears to be from microscopic disseminations of i r o n oxide. Sutherland-Brown (1967), mentions that he found no f e l d spathoids associated with the p u l a s k i t e s from the Oro Denoro area and would consider these rocks as andesite dykes. East of Wilgress Lake, w i t h i n the large expanse of a l k a l i c i n t r u s i v e rocks, the " c l o t porphyry" becomes c h a r a c t e r i s t i c a l l y grey on a f r e s h surface and the groundmass appears extremely f i n e - g r a i n e d and dense. Here a l s o , another v a r i e t y of the syenite porphyry i s found, which as Monger (1968) notes, has a high "phenocryst to groundmass r a t i o " and thus appears medium-grained equigranular rather than p o r p h y r i t i c . This i n t r u sive i s speckled i n appearance, composed almost wholly of coarse p l a g i o c l a s e phenocrysts with b i o t i t e phenocrysts r e s t r i c t e d to the i n t e r s t i t i a l groundmass. P l a g i o c l a s e s are zoned and have a composition range from An^-Ang^. B i o t i t e s are f r e s h but the pyroxenes i n groundmass have been almost completely a l t e r e d to u r a l i t e (Monger, 1968). Anhedral grains of quartz have been found i n trace amounts throughout the groundmass. Monger (l968) states: "there are other i n t r u s i v e rocks i n the map area whose T e r t i a r y age i s demonstrated by crossc u t t i n g r e l a t i o n s h i p s but cannot be r e l a t e d to any p a r t i c u l a r l a v a type" (Marron Formation).  70. These syenites commonly occur as f e l d s p a r porphyry syenite dykes such as that found immediately northwest of the Hummingbird showing. Here, potash-feldspars form extremely large (up to 1 inch long) pink, euhedral c r y s t a l s set i n a pale brown fine-grained matrix. Epidote and c h l o r i t e forms a c h a r a c t e r i s t i c yellow-green a l t e r a t i o n rim around the large feldspar phenocrysts. Radiometric dates f o r C o r y e l l i n t r u s i v e s i n the immediate map area are not a v a i l a b l e , but ages of 56 to 60 m i l l i o n years have been obtained from the type C o r y e l l b a t h o l i t h to the east (Monger, 1968). Ages obtained from T e r t i a r y lavas i n southcentral B r i t i s h Columbia are 45-53 m i l l i o n years, and Monger states that "at l e a s t part of t h i s p a r t i c u l a r i n t r u s i o n appears to have been emplaced e a r l i e r than rocks r e l a t e d to the Marron Formation". Therefore, i t appears that the main C o r y e l l i n t r u s i v e a c t i v i t y w i t h i n the map area conforms to that of the C o r y e l l b a t h o l i t h and i s probably Eocene i n age. Monger concludes that: "there i s no proven r e l a t i o n s h i p between the C o r y e l l i n t r u s i o n s and Marron Formation at present and they appear merely to have been formed at roughly the same time i n the same general area and show the same general range of compositions".  71. SECTION I I I : STRUCTURES  The Grand Forks map area contains several major s t r u c t u r a l elements: the Granby River Fault, an extension of the eastern boundary f a u l t of the Republic Graben i n northern Washington State; other related northwest and northeast trending fracture patterns; the overturned western limb of a north-northeasterly gently plunging, nearly recumbent syncline outlined within the T r i a s s i c - J u r a s s i c sediments and volcanics; several major northwest trending steeply dipping fault/shear zones that appear to divide the s y n c l i n a l f o l d structure into separate e n t i t i e s that are shifted progressively to the south-southwest from north to south; and eastern t i l t i n g and gently warping of the E a r l y T e r t i a r y sedimentary and volcanic units.  Republic Graben  The north to northeast trending Republic Graben, which i s the p r i n c i p a l s t r u c t u r a l element i n Curlew County N-l/ash., and has been traced f o r some 30 miles to the south, and has an apparent maximum stratigraphic separation of some 17,000 feet, appears to lose i t s i d e n t i t y as i t crosses the International Boundary into the Grand Forks area (Parker and Calkins, 1964). The Granby River Fault, trending north-northeast immediately west of Grand Forks, appears to be the northern extension of the Drummer Mountain Fault or the eastern boundary f a u l t of the Republic Graben. Like the Drummer Mountain Fault, the Granby River Fault appears to be a steep, westerly-dipping normal f a u l t that separates the  72. down-dropped Permo-Triassic  and younger rocks to the west, from the up-  l i f t e d h i g h l y metamorphosed Grand Forks Group on the east. The northern extension of the Granby River Fault i s obscure, but several g e o l o g i c a l maps of B r i t i s h Columbia show i t extending some 25-30 miles north of Grand Forks. V e r t i c a l movement on the f a u l t near Grand Forks i s unknown, but Parker and Calkins ( 1 9 6 4 ) , state that "the v e r t i c a l component decreases n o r t h e r l y " so that near Grand Forks and to the north, i t i s probably very much l e s s than the 17 000 feet maximum. 9  The extension to the Bacon Creek F a u l t or the western boundary f a u l t of the Republic Graben has not been found north of the I n t e r n a t i o n a l Boundary. However, a 30 foot t h i c k north-northeasterly trending v e r t i c a l to steep southeasterly dipping mylonite zone, was found w i t h i n fragmental andesites along the o l d abandoned r a i l r o a d grade about one h a l f mile west of Eagle Mountain.  This mylonite zone may be the northernmost extension  of the Bacon Creek F a u l t that i s s a i d to die out as i t crosses the I n t e r n a t i o n a l Boundary i n t o Canada (Parker and C a l k i n s , 1964). However, t h i s sheared zone does not appear to extend f o r any great distance to the northeast. Parker and Calkins (1964), state that the "boundary f a u l t s and the general shape of the graben were e s t a b l i s h e d before and during deposition of the O'Brien Creek Formation". The l a t t e r i s the K e t t l e River Formation equivalent i n northern Washington, hence dates the f a u l t i n g as Late Cretaceous or E a r l y T e r t i a r y . They also mentioned that movements along the boundary f a u l t s were i n t e r m i t t e n t , and p e r s i s t e d u n t i l w e l l a f t e r deposition of the Marron v o l c a n i c equivalents, or w e l l a f t e r Oligocene time.  73. Northwest and Northeast Fault Patterns  Most other f a u l t s i n the graben trend north to northeast p a r a l l e l to the boundary f a u l t s . Other numerous northwest trending cross f a u l t s with associated serpentinites, and quartz f i l l e d fractures have been noted, e s p e c i a l l y i n the Republic gold-quartz mining d i s t r i c t some 30 miles south of the Grand Forks map area (Parker and Calkins, 1964), and near Goosemus Creek immediately  south of the International Boundary.  Within the Grand Forks area, similar northeast and northwest trending conjugate fracture patterns have been mapped and are very well demonstrated within the massive more competent fragmental andesites southwest of Goat Mountain.  These two fracture  systems appear to persist  through-  out the map area, with l o c a l variations, and the northwest d i r e c t i o n appears to dominate the Grand Forks area. The most s t r i k i n g feature about these northwest trending f a u l t zones i s their association with elongate sheared, serpentinized ultrabasio and pyroxenite bodies. Northwest f a u l t zones commonly have a steep southwest dip, as demonstrated by the shearing i n the serpentinites and the f o l i a t i o n s within the surrounding country rocks, and are believed to be steep thrust planes. Absolute directions and distances of movement along these zones are d i f f i c u l t to ascertain. The accompanying geological map  demonstrates, from north to south,  many northtfest trending steeply dipping f a u l t zones, that cross the at what appear  map  to be regular i n t e r v a l s , suggesting probably some unique  control to t h e i r even d i s t r i b u t i o n and directions. Northwest and northeast fracture patterns and northwest f a u l t zones  74. are believed to be related to the same stress system that •• formed the Republic Graben and i t s related f a u l t and fracture sets to the south. With the loss of the western boundary f a u l t , on crossing the International Boundary, the northwest d i r e c t i o n appears to have taken up much of the displacements and movements i n the Grand Forks d i s t r i c t . A l l the major f a u l t s appear to have been active during the T e r t i a r y period, but much of t h i s r e l a t i v e l y recent movement may have taken place on structures that originated when the T r i a s s i c and Jurassic rocks were being deposited. Many of the ultrabasic bodies scattered throughout the area have been intruded along these older breaks, and probably s l i v e r s of these serpentinized ultrabasics were sheared and brought up along these deep f a u l t zones i n late T e r t i a r y time. Similar T e r t i a r y northwest and northeast conjugate fracture patterns are prominant i n many places i n the southern Boundary and Okanagan D i s t r i c t s (Church, 1967; pp.96-99) and (Ross and C h r i s t i e , 1969). This pattern i s shown i n Figure 2, p.  Dykes  Throughout  the northern portion of the map area i s found a promin nt  northwest to north and minor northeast trend of numerous pulaskite and a l k a l i c C o r y e l l i n t r u s i v e dykes. Several of these dykes have a moderate southwest dip and are believed related to the formation of the northwest shear zones and northwest-northeast fracture systems. In several places an apparent horizontal displacement of several thousand feet can be seen, such as the limestone found on either side of the northwesterly trending  75. p u l a s k i t e dyke southwest of the B.C. mine and immediately north of the R. i e l l mine. This dyke appears to dip moderately to the northeast. Near Hardy and Eagle Mountains, several v e r t i c a l e a s t e r l y trending quartz-monzonite porphyry dykes are found. These i n t r u s i v e s are probably r e l a t e d to the "Scatter Creek Formation" i n northern Washington, and here appear to be e a r l y T e r t i a r y , d e f i n i t e l y pre-Coryell or Eocene i n age. These e a s t e r l y trending dykes probably r e f l e c t a r e l a x a t i o n and change i n s t r e s s f i e l d s forming the Republic Graben.  Folds An overturned western limb of a l a r g e , open, nearly recumbent s y n c l i n a l structure that opens to the east and whose f o l d a x i s plunges gently to the north-northeast and a x i a l plane clips gently to moderately to the northwest, i s demonstrated w i t h i n the T r i a s s i c sediments and J u r a s s i c v o l c a n i c s underlying Hummingbird Ridge, northeast of Thimble Mountain (Figure 4, p. 81, shows a diagramatic c r o s s - s e c t i o n ) . Several i n v e r t e d graded beds and the complete r e v e r s a l i n the normal s t r a t i graphic sequence here suggest the overturning. The general pattern of t h i s open s y n c l i n a l structure i s w e l l demonstrated i n the c l i f f d i r e c t l y north-northeast across the Granby V a l l e y from the Hummingbird prospect (Plate 13, p. 77). Southward from Hummingbird Ridge, the s y n c l i n a l structure has been transected by a s e r i e s of northwesterly trending, steeply dipping f a u l t zones and appears to have been s h i f t e d p r o g r e s s i v e l y towards the west, as counterparts of t h i s overturned western limb are found at the  76. Shickshock and S a i l o r Boy showings, at the B.C. mine and at the Emma and Oro Denoro mines. I f these are indeed fragments of the same limb, then several miles of apparent horizontal displacement are represented here. South of Oro Denoro, the stratigraphic sequence i s found right side up and dipping moderately to gently northeast  to easterly, and appears  to represent the unfolding or opening of the overturned to v e r t i c a l limb,at Oro Denoro,into the western limb of a north or northwesterly plunging open trough or basin structure underlying Baker Ridge and to the west (see Figure 5, p. 82). Several major northwest trending structural breaks appear to have stepped down the northeasterly dipping T r i a s s i c sedimentary sequence at almost regular i n t e r v a l s to the south and southwest of Baker Ridge as similar sedimentary sequences occur at Hardy and Eagle Mountains and immediately west of Grand Forks.Occurrences of similar rock units immediately south of the International Boundary i n northern Washington probably represents a further downdropping to the southwest. A closure i n this northwesterly plunging basin or syncline i s demonstrated  within the Brooklyn Limestone south of Hardy Creek, north-  west of Grand Forks, where the beds swing from-a northwest trend/ northeast moderate dip to a northeast and northerly almost v e r t i c a l dip. The northwesterly plunge of the s y n c l i n a l structure i s also  demonstrated  by several minor s y n c l i n a l and a n t i c l i n a l closures within the Brooklyn Limestones some 2500 feet south of Goat Mountain and approximately 2000 feet west of Hardy Mountain. Trends of minor f o l d axes within the T r i a s s i c sediments also attest to this northerly plunge.  i  77.  Plate 13:  A NE view of the limestone c l i f f across the Granby V a l l e y , d i r e c t l y opposite the Hummingbird Showing. Shows s y n c l i n a l minor f o l d structure w i t h i n the w e l l banded limestone u n i t and several f l a t dipping T e r t i a r y dykes.  78.  A gradual swing i n the plunge directions of these minor f o l d axes, from a gently plunging north-northeasterly d i r e c t i o n i n the northeast corner of the map area to a moderate to gentle northwesterly plunge south of Goat Mountain suggest a warp i n the a x i a l plane and f o l d axis of the north to northeasterly trending gross structures. However, trends of minor f o l d axes could be greatly affected by the numerous shear and f a u l t zones that cross-cut the gross structural trend, and d i r e c t relationships between the i n d i v i d u a l faulted blocks are unknown. The age of t h i s s y n c l i n a l structure i s pre- Late  Jurassic since i t  i s cut by the Nelson granodiorites at Oro Denoro. I t i s probably postEarly to Middle Jurassic as i t involves the Middle Jurassic Andesites. Furthermore,  Fragmental  since these andesites i n part l i e unconformably  on limestone erosion surfaces, the deformation may well have started s l i g h t l y before or during the deposition of the Fragmental Andesites. Intense f a u l t i n g and intrusive a c t i v i t i e s obscure the structures of the area west of Grand Forks, but i n general the minor folds within the limestones appear to plunge gently southeast, almost a direct reversal to the gentle northwesterly d i r e c t i o n found to the north. Structures within the Anarchist cherts and p h y l l i t e s below the T r i a s s i c sediments at the southern part of the map area are obscure  due  to the intensely fractured nature of the rock and general lack of good exposures.  However, one minor f o l d was found whose axis plunges  moderately to the southeast, which appears to conform roughly to the southeast-northwest  trending structures mapped by Parker and Calkins(l964)  i n s i m i l a r rock units some 6 miles to the southwest i n northern Washington.  79. The s t r u c t u r a l g r a i n of the h i g h l y metamorphosed Grand Forks rocks l y i n g to the east of the map area, i s almost at r i g h t angles to that w i t h i n the T r i a s s i c and younger rocks. The Grand Forks  paragneisses  contain east-west major s t r u c t u r a l trends that are c l e a r l y v i s i b l e from a e r i a l photographs and Parker and Calkins (1964) state that s i m i l a r rocks of the Tenas Mary Creek Formation have gently dipping east-west s t r u c tures . I t appears from the mapping by Parker and Calkins that s t r u c t u r a l trends s h i f t from a general east-west d i r e c t i o n w i t h i n the Pre-Cambrian or E a r l y Paleozoic Grand Forks equivalent rocks, to a northwest-southeast trend i n the Permian-Pennsylvanian Anarchist equivalent rocks. As p r e v i o u s l y mentioned, the M i d . T r i a s s i c - Mid. J u r a s s i c sediments and v o l c a n i c s i n the Grand Forks-Eholt map area contain northwest to northeast trending s t r u c t u r e s . This suggests that there i s a change i n the s t r u c t u r a l g r a i n with depth or with age of the host rocks, r e f l e c t i n g several d i f f e r e n t periods of deformation  probably  or a d i f f e r e n t  s t r u c t u r a l s t y l e with depth of b u r i a l . Hence the deeply buried, h i g h l y metamorphosed Grand Forks gneisses house predominantly east-west s t r u c tures and the T r i a s s i c to J u r a s s i c rocks contain NW to NE  trending  structures. V. Preto (personal communication, 1970) mentioned that the trending recumbent f o l d found at the northeast corner of the map  NNE area  appears t y p i c a l of the phase 3 structures found i n the high grade metamorphics of the Grand Forks Group north of Grand Forks.  80. T e r t i a r y Block F a u l t i n g and T i l t i n g Eastward t i l t i n g and gentle warping have been recorded by Monger (1968) w i t h i n the large T e r t i a r y covered blocks throughout the southern Boundary D i s t r i c t . This i s demonstrated by the T e r t i a r y covering at Baker Ridge where the K e t t l e River sediments and o v e r l y i n g Marron v o l c a n i c s dip  about 45° to the east and appear to form the western limb of a broad  gentle syncline (Figure 5? p.82). The hinge zone and eastern limb of t h i s T e r t i a r y basin has been f a u l t e d and eroded o f f to the east of Baker Ridge. This T e r t i a r y f a u l t i n g , t i l t i n g , and warping i s probably contemporaneous (but l a t e ) with the development and s e t t l i n g of the Republic Graben,northwest and northeast f r a c t u r e system i n the area. Eastward t i l t i n g and warping presents a problem when c o r r e l a t i n g s t r u c t u r e s between i n d i v i d u a l f a u l t bounded blocks since i n most places the  T e r t i a r y cover i s absent, having been eroded away, and. therefore  gives no c o n t r o l to the amounts and d i r e c t i o n s of t i l t i n g .  NW  Figure 4  NW-SE C.PR.  diagramatlc  c r o s s - s e c t i o n (looking  track intersection  to where  Lime  NE)  creek  from the  Rathmullen  flows into the  Granby  creek — valley.  84.  SECTION IV:  METAMORPHISM  Regional Metamorphism The Permian, uppermost Anarchist cherts and p h y l l i t e s , the T r i a s s i c sediments and the J u r a s s i c Fragmental Andesites that underlie the Grand Forks map area have a l l undergone low-grade r e g i o n a l metamorphism and contain metamorphic minerals t y p i c a l of the Lower Greenschist Facies. The g n e i s s i c t e r r a i n east of the Granby River F a u l t , on the other hand, contains high-grade metamorphic minerals s i m i l a r to the Tenas Mary Creek Formation to the south, which Parker and C a l k i n s (1964) have c l a s s i f i e d as Almandine-Amphibolite  Facies ( a f t e r Turner and Verhoogen I960, p.554).  Parker and C a l k i n s suggest that from the lowermost gneisses of the Tenas Mary Creek Formation up through the o v e r l y i n g Permian s c h i s t s , p h y l l i t e s and greenstones, i s represented a continuous change i n metamorphic grade from Almandine-Amphibolite  Facies a t the bottom, to  Greenschist Facies a t the top. This probably suggests an increase i n metamorphic i n t e n s i t y with s t r a t i g r a p h i c depth or b u r i a l (Figure 7 , p . 8 5 ) . Within the Grand Forks area, t h i s encompasses rocks from the gneisses of the Grand Forks Group to the Knob H i l l cherts and greenstones a t the top of the Anarchist Group. Such a metamorphic gradation i s suggestive of a Barrovian type Facies Series ( a f t e r Winkler, 1967 pp.88-89). A s e r i e s of amphibolites mapped by L i t t l e (1965) below the uppermost massive cherts and greenstones and limestone of the Anarchist Group contain minerals very t y p i c a l of the t r a n s i t i o n between the uppermost Greenschist Facies and lowermost Almandine Amphibolite f a c i e s .  85.  Mid. J u r a s s i c  CO UJ  andesites  o <  Triassic clastic sediments  a> a  \  o o o  a>  Tz.  I— CO  Permian greenstones  X  and  o  CO  \  -z.  UJ UJ  cc o  cherts  phyllites  V  o  o •5  2500feet  o  schists  i  2 5 0 0 feet  ! f  \ CO UJ  quartz,  I  o  o  s  plagioclase gneiss 700  '  -  5300 feet  LU  _J  o  go X  hornblende  schist  a.  quartzite  < UJ  •I  500-  1  3000feet. marble  Q <  I  granite gneiss  I  1  3 5 0 0 feet  I 1 Figure  7  Observed other  stratigraphic  features  of  range  the  of  Early  Triassic - Jurassic  rocks.  observed  author.  (after  by  the  Parker  and  metamorphic  minerals  P a l e o z i c - Permian  Checks  Calkins, 1 9 6 4 ;  represent  with  and and  features  modifications.)  86. Parker and Calkins  (1964) state that:  "The t r a n s i t i o n from the Greenschist Pacies to the Almandine-Amphibolite Pacies apparently takes place i n the stratigraphic i n t e r v a l between the middle of the schist unit and several hundred feet above the base of the p h y l l i t e , a zone that contains minerals c h a r a c t e r i s t i c of both f a c i e s " . This corresponds to somewhere near the top of the Anarchist Group i n the Grand Forks area. The highly metamorphosed Grand Forks gneisses have not been studied by the author, and according to Parker and Calkins  (1964),  minerals found within the Tenas Mary Creek rocks (Grand Forks Group equivalent) t y p i c a l of the Almandine-Amphibolite muscovite,  f a c i e s are: b i o t i t e ,  pink garnet, dark green hornblende and a c t i n o l i t e , orthoclase,  plagioclase (oligoclase and minor a l b i t e ) , s i l l i m a n i t e , and c o r d i e r i t e . Metamorphic minerals characteristic of the Permian Anarchist cherts, mica-schists and p h y l l i t e s i n the Grand Forks area include muscovite, s e r i c i t e ? , b i o t i t e and c h l o r i t e . Some r e c r y s t a l l i z a t i o n of quartz occurs i n the s i l i c e o u s units. These f o l i a t e d rocks are highly deformed and sheared, very suggestive of dynamic thermal metamorphism. The  low  thermal grade probably f i t s near the Upper Greenschist Facies as suggested by Parker and Calkins  (1964).  The fine-grained matrix of the Sharpstone Conglomerate, wacke, a r g i l l i t e and mudstone sequence contains abundant shreds  of c h l o r i t e ,  s e r i c i t e , minor epidote and possibly pyrophyllite, t y p i c a l of the lowgrade Greenschist Metamorphic Facies. The Puddingstone sequence, a maroon coloured equivalent of the Sharpstone, appears to have very l i t t l e c h l o r i t e a l t e r a t i o n but contains much microscopic disseminated  87.  hematite and i r o n oxide. The overlying Brooklyn Limestone of  shows r e l a t i v e l y l i t t l e evidence  t h i s widespread low-grade metamorphic effect except f o r s l i g h t re-  c r y s t a l l i z a t i o n and sparry c a l c i t e f i l l i n g numerous fractures i s ubiquitous. Jurassic Fragmental Andesites found throughout the Grand Forks area provide  map  the best evidence of t h i s low-grade metamorphism, having  i n places up to 25-30$ a l t e r a t i o n minerals, mainly: c h l o r i t e , epidote and carbonate with minor a l b i t e , s e r i c i t e and opaques ( p y r i t e ? ) .  Contact Thermal Metamorphism Towards the northern part of the map area, near the large body of Nelson granodiorite and i n the v i c i n i t y of the smaller i n t r u s i v e plugs throughout the map area, the Permian to Jurassic folded sedimentary and volcanic rocks have undergone extensive thermal a l t e r a t i o n and charact e r i s t i c thermal aureois are found extending f o r some distance away from these i n t r u s i v e s . South of the Oro Denoro workings, and adjacent to the Nelson granodiorite the Brooklyn Limestone i s r e c r y s t a l l i z e d to a fine-grained marble,and to the south, farther from the contact, becomes coarsergrained.  The thermal effect appears to have extended some 2000 feet to  the south. The more impure massive and banded limestones a l t e r to a coarse-grained garnet (andradite?), epidote, pyroxene, c a l c i t e skarn that often c a r r i e s magnetite, p y r i t e , chalcopyrite and hematite mineralization, occasionally forming economic grade.  Oro Denoro, Emma, B.C.,  88. and R. B e l l mines of the Summit Camp are examples (see Appendix I , p.106, f o r a d e t a i l e d d e s c r i p t i o n of the m i n e r a l i z a t i o n i n the area). Farther from the i n t r u s i v e contact the well-bedded limestone u n i t s occur as d i s t i n c t bands of dense m i c r o c r y s t a l l i n e garnet, pyroxene and epidote h o r n f e l s with minor m i n e r a l i z a t i o n , a l l interbedded with coarsely c r y s t a l l i n e marbles. The Sharpstone Conglomerate sequence adjacent to the l a r g e r i n t r u sive bodies also d i s p l a y s t h i s thermal e f f e c t and i n places appears as a dense s i l i c e o u s h o r n f e l s w i t h associated disseminated p y r i t e ( i . e . west of Grand Forks). North of the Emma workings, a conglomerate appears white and bleached with the grey chert pebbles remaining unaffect. Some distance from the i n t r u s i v e contact, the fine-grained matrix of the Sharpstone sequence i s almost t o t a l l y a l t e r e d to a f i n e f i b r o u s mass of dark green hornblende. Northwest of the Hummingbird showing, i n the immediate v i c i n i t y of the r a i l r o a d tunnel, the Sharpstone Conglomerate i s s i l i c i f i e d and c a r r i e s disseminated p y r i t e . Here also the f i n e grained matrix i s almost completely a l t e r e d to dark green hornblende and chlorite. Dense s i l i c e o u s and biotite-muscovite hornfelsed metasediments are t y p i c a l of the Anarchist cherts and cherty a r g i l l i t e s found adjacent to the Nelson g r a n o d i o r i t e contact some 4000 feet west of Oro Denoro. The interbedded Anarchist greenstones have been almost t o t a l l y a l t e r e d to coarse-grained amphibolites. I n several places, both north and south of the granodiorite body, these metasediments have a schistose to g n e i s s i c texture which roughly p a r a l l e l s the i n t r u s i v e contact, probably  89. suggesting some flowage associated with f o r c e f u l i n t r u s i o n of the Nelson g r a n o d i o r i t e . Lack of c h i l l e d margins at the i n t r u s i v e contacts, large surrounding thermal aureoles and the coarse-grain s i z e and mineralogy of the associated skarn deposits, suggest a deep seated slow c o o l i n g or Mesozonal environment f o r the Nelson granodiorite emplacement.  Coarsely c r y s t a l l i n e f i b r o u s r a d i a t i n g a c t i n o l i t e c r y s t a l s have been found r e p l a c i n g limestone cobbles w i t h i n an a l t e r e d sedimentary sequence south and adjacent to a q u a r t z - d i o r i t e porphyry found along the Canadian P a c i f i c Railway track north of Fisherman Creek. W o l l a s t o n i t e , as coarsely bladed r a d i a t i n g c r y s t a l s confined to the lower coarser-grained section of graded beds, was found i n a s l i g h t l y hornfelsed bedded a r g i l l a c e o u s limestone u n i t at the Hummingbird workings. The occurrence of w o l l a s t o n i t e and of p y r r h o t i t e and s p h a l e r i t e m i n e r a l i z a t i o n w i t h i n the mine workings suggests a high temperature of formation. Winkler (l967, pp.35-36) states that w o l l a s t o n i t e found i n thermal aureoles i s i n d i c a t i v e of high l e v e l i n t r u s i o n s with high temperature (600°-700°C) and associated low pressure conditions. Several small q u a r t z - d i o r i t e porphyry i n t r u s i v e s are found to the west and a s i m i l a r mass probably underlies the Hummingbird showing. These Late Cretaceous-Early T e r t i a r y quartz-monzonite and quartzd i o r i t e porphyries are therefore probably high temperature high l e v e l i n t r u s i o n s that formed rather narrow thermal aureoles and must have  90. cooled very r a p i d l y ; very d i f f e r e n t from the conditions surrounding the Upper J u r a s s i c Nelson g r a n o d i o r i t e s . Thermal aureoles surrounding the T e r t i a r y C o r y e l l syenites and hypabyssal dykes and sheets appear to be very small, and the thermal e f f e c t surrounding these rather anhydrous i n t r u s i v e s must have been weak. They a l s o appear to be high l e v e l i n t r u s i o n s that have cooled r a p i d l y as they contain c h i l l e d border phase and have very l i t t l e thermal e f f e c t on the surrounding rocks. The age of o v e r a l l r e g i o n a l metamorphism i s probably post-Middle J u r a s s i c (Fragmental Andesites) to Upper J u r a s s i c (Nelson g r a n o d i o r i t e ) . The T r i a s s i c sediments and Middle J u r a s s i c andesites appear to have been folded p r i o r to or during the onset of any extensive period of metamorphism, and i s probably r e l a t e d to the intense f o l d i n g , deep b u r i a l , and elevated temperature and pressures that occurred at t h i s time. Parker and C a l k i n s (1964, p. 79) state that: "Although the g r a n o d i o r i t e d i d not cause the metamorphism at i t s present p o s i t i o n , an i n t r u s i v e magma that formed the g r a n o d i o r i t e could very w e l l have been generated at depth by processes r e l a t e d to r e g i o n a l metamorphism. Broadly speaking, the g r a n o d i o r i t e i s considered to be a l a t e phase i n the o v e r a l l period of metamorphism". C h l o r i t e was noted along some of the T e r t i a r y f r a c t u r e and j o i n t i n g planes i n d i c a t i n g that some l o c a l low-grade metamorphism occurred during Middle T e r t i a r y time ( ? ) .  91. SECTION V: SUMMARY AND CONCLUSIONS  Summary  P r i o r to the deposition and accumulation of the Permian Anarchist cherts, a r g i l l i t e s , greenstones and minor limestone lenses, much of the geological history of the Grand Porks area i s unknown. Paragneisses, marbles,amph±bolites and schists of the Grand Porks Group found east of the map area hold the oldest h i s t o r y within the Boundary D i s t r i c t . These rocks were o r i g i n a l l y marine sediments, probably representing part of a eugeosynclinal belt along the then western continental border during Early Paleozoic or Late pre-Cambrian  time, that have subsequently under-  gone deformation and intense metamorphism. A continual marine depositional  sequence probably exists from Early Paleozoic (Grand Porks Group) to  Permian  or Early T r i a s s i c (Anarchist) time with several periods of up-  l i f t , erosion and resubmergence (Parker and Calkins, 1964). Emplacement of f e l s i c and mafic s i l l s , dykes and i r r e g u l a r i n t r u s i v e bodies accompanied these movements. During Permian time the region was depressed below sea l e v e l and large quantities of mafic volcanic t u f f s and flows, black shales, cherts, ribbon cherts and l e n t i c u l a r limestones accumulated  therein under deep  water quiet sedimentation, probably i n an i s l a n d arc type environment. This sequence i s similar to the Cache Creek Assemblage found more widespread through south and central B r i t i s h  Columbia.  Before the Middle T r i a s s i c , Anarchist rocks must have undergone intense deformation since they appear much more i n t e r n a l l y deformed  p.r-c.  I  92.  sheared than the overlying unconformable sediments and volcanics. During Middle T r i a s s i c time, the Anarchist rocks were u p l i f t e d ( ? ) , folded and eroded. Breaks ( f a u l t s ) developed throughout the Boundary D i s t r i c t , forming several northerly trending deep marine basins at the edge of the T r i a s s i c (Nicola?) Sea. Into these basins poured rapid accumulations of coarse angular chert and l i t h i c volcanic fragments from the highlands to the north and northwest, forming numerous fanglomerates and d e l t a i c deposits at the edge of the T r i a s s i c sea (Figure 3, p. 28). Farther from the source, within the basin to the southeast, these conglomeratic lenses pinch out and i n t e r f i n g e r with f i n e r thin-bedded wackes, a r g i l l i t e s , s i l t s t o n e s and mudstones deposited under quieter deep water conditions. I n f i l l i n g of the basin coupled with erosion of the sourceland i s r e f l e c t e d i n the increasingly finer-grained sediments grading outwards and s t r a t i g r a p h i c a l l y upwards within the basin. Eventually, with an increase i n carbonate content, the basin became  r e s t r i c t e d and shallow water microcrystalline limestone deposi-  t i o n prevailed,marking the start of the Brooklyn Limestone sequence. Windblown chert ovoids within the basal limestones suggest a near shore and onshore a r i d environment. Tuffaceous bands within the limestone indicates nearby volcanic a c t i v i t y (Nicola volcanic a c t i v i t y to the  NW?).  Local c a t a c l a s t i c limestone breccias attest to contemporaneous f a u l t i n g and slumping within the carbonate basin. Interbedded black shales and argillaceous limestone units thin to the east and southeast farther within the basin of deposition. Carbonate deposition probably continued u n t i l Early Jurassic to Mid-Jurassic time with very l i t t l e contribution  93. of c l a s t i c material since r e l i e f appears to have been very low i n the surrounding positive areas. During Middle Jurassic time, much of the area was u p l i f t e d with accompanying erosion of some of the carbonates. Contemporaneous with t h i s u p l i f t began a time of widespread volcanism. Explosive andesite p y r o c l a s t i c debris, massive flows and agglomerates  o v e r l i e the limestone  unconformably i n most places. Andesite flows poured into the remaining shallow carbonate basins and quickly flooded the surrounding area. The extent, thickness and duration of the andesite volcanism  i s unknown.  The beginning of Middle Jurassic volcanism probably r e f l e c t s the early onset of s t r u c t u r a l deformation, b u r i a l , and accompanying i n creased geothermal gradient that produced: the northwest  to northeast  trending gross structures within the T r i a s s i c and Jurassic rocks; related low-grade Greenschist Facies regional metamorphism within the Permian to Mid-Jurassic rocks; and high-grade regional metamorphism within the deeper buried older Grand Forks rocks. The f i n a l r e s u l t of t h i s increased deformation, b u r i a l , and metamorphism was the emplacement of the Nelson granodiorites and related V a l h a l l a granites during  Early  Late -Jurassic time. These Upper Jurassic acid intrusions were emplaced under Mesozonal conditions, forming large thermal aureoles i n surrounding country rocks and, i n several l o c a l i t i e s , coarse-grained copper bearing skarns within the Brooklyn Limestone adjacent to i n t r u s i v e contacts. After emplacement, the i n t r u s i v e s and surrounding rocks cooled slowly with subsequent decrease i n the geothermal gradient, leaving the contact thermal  94.  aureoles and regional metamorphic grade now older rocks. Extensive sediments that may  found i n the Jurassic and  erosion stripped away late Jurassic or Cretaceous  have accumulated and exposed the deformed low grade  metamorphic and Nelson i n t r u s i v e rocks. The region was u p l i f t e d during Late Cretaceous or E a r l y T e r t i a r y time and appears to have remained above sea l e v e l up to the  present.  During t h i s Late Cretaceous or Early T e r t i a r y time, block f a u l t i n g , the i n i t i a l development of the Republic Graben and related northeast  and  northwest fracture systems were established i n northern Washington and the Grand Porks area. Contemporaneous with the intermittent s e t t l i n g and movements along the northwest steeply dipping f a u l t zones, was  the  emplacement of d i a p i r i c serpentinized ultramafics and pyroxenites, coarse-grained  large  d i o r i t e and leucogabbro bodies, and d i o r i t e dykes. In  the northern part of the map  area, small i r r e g u l a r quartz-diorite and  quartz-monzonite porphyry high l e v e l intrusions are confined to areas close to these northwest s t r u c t u r a l breaks, and appear to have been intruded about t h i s time. Deposition of the (Eocene-Oligocene?) continental Kettle River sediments followed the i n i t i a l development of the Republic Graben. These fast accumulating coarse c l a s t i c sediments have a varied o r i g i n from l o c a l volcanic a c t i v i t y presumably associated with the f a u l t i n g , to d e t r i t u s eroded from the nearby u p l i f t e d blocks (Monger, 1967). Local r e l i e f during t h e i r deposition must have been considerable, indicated by the thick beds and large cobble conglomerate units  that  suggest contemporaneous f a u l t i n g . The Kettle River sediment equivalents  95. to the south of the Grand Forks area appear confined to the sunken block of the Republic Graben and similar l o c a l but smaller continental basins may have existed to the north i n the Boundary D i s t r i c t . Subsidence and f a u l t i n g may not have been as great i n the Boundary D i s t r i c t and t h i s accounts f o r the r e l a t i v e l y few l o c a l occurrences of Kettle River sediments found. Parker and Calkins  (1964) believe that these  arkosic sediments continued to accumulate as long as movements and r e adjustments cont  ued along the main boundary f a u l t s and the numerous  subordinate north-^northeast trending f a u l t s . After much of the subsidence and adjustment within the i n d i v i d u a l blocks had ceased, lavas and pyroclastic accumulations of the Marron Formation were deposited conformably on top of the Kettle River sediments and older rocks of the t i l t e d blocks. During and following the extrusion of the Marron Volcanics, Coryell a l k a l i c intrusions invaded the country rocks as hypabyssal plugs, sheets and dykes, i n many places f i l l i n g the prominent northwest and northeast T e r t i a r y fractures. These a l k a l i c rocks cut the Kettle River sediments and older rocks and are believed i n part, feeder dykes to the middle and upper parts of the Marron extrusives. The upper part of the Marron Formation has been subsequently eroded and i s missing i n the Grand Forks area. The easterly trending "Scatter Creek" quartz-monzonite  porphyry dykes, found at the south of  the map area, were intruded about t h i s time. Later volcanic a c t i v i t y within the Grand Forks area, suggested by the pyroclastic and glassy b a s a l t i c rocks of the Miocene Klondike Mount a i n Formation i n northern Washington i s missing and believed eroded  Correlation with assemblages of in  widespread  British  Formations  extent  in the  Grand F o r k s - E h o l t  Columbia  Marron  Formation includes:  Kettle  c Takla Hazelton (Nicola?) Assemblage J ( U. Triassic — M. J u r a s s i c )  ( Miss. —  . w  * y  D  a  l  y  I  M  1  Fragmental  Eholt  Brooklyn L i m e s t o n e  Conglomerate  L.Triassic)  Rossland  Upper Triassic  Terrain  -^fc — -  Perm.  Mount  Knob Hill c h e r t s and greenstones  V  Penn.  Grand Forks  and Monashee  Groups  units  showing and  possible  formations  correlations outside  Washington  Washington  Formation  (Campbell)  ( L — M. T r i a s s i c )  the  Roberts Mary of  of  the  Creek  / ?  various  Grand F o r k s -  layered Eholt  Group  northern  Early Paleozoic Cambrian  Table  Tenas  /  pre-  Figure 8  N.Washington.  Formation  northern  Slocan Group  ^ Shuswap  S.E.  Middle Triassic  Sequence  Group  includes  of  Mid.-,  Formation  and  northern  OBrian Creek  Jurassic  j /  Anarchist  of  Eocene  Volcanics(Carswell)  in  Sanpoil Volcanics  l  Andesites  in part  correlations  British Columbia  Oligocene  ,  River Formation  Sharpstone Cache Creek Assemblage  Area  ^ ° ^ ° - ' / . . Phoenix Vol. Group (Little) d  Possible  Age  rock  area.  (Little)  Formation Washingfon  97. away. Late T e r t i a r y diastrophism i s evident from the many northwest and northeast f a u l t s found c u t t i n g the T e r t i a r y rocks. Regional t i l t i n g of some 30°to 45° to the east accompanied gentle f o l d i n g or warping of the T e r t i a r y sediments and v o l c a n i c s . Extensive erosion followed, s t r i p p i n g almost a l l of the T e r t i a r y layered rocks from the area. I n the P l e i s t o c e n e , g l a c i a l erosion and deposition modified the topography and drainage. The receding i c e l e f t the upland areas mantled with g l a c i a l t i l l and l a i d down g l a c i a l outwash deposits i n the present v a l l e y s such as Granby and K e t t l e River v a l l e y s . Present r i v e r a c t i o n has modified the v a l l e y bottoms.  Conclusions From the mapping and i n t e r p r e t a t i o n s involved i n t h i s t h e s i s , several conclusions can be drawn: 1.  The p r e v i o u s l y mapped Anarchist Group underlying the Grand Forks-Eholt erea appears to have included rocks as young as Middle J u r a s s i c , and can be divided i n t o two rather d i s t i n c t assemblages: the more widespread Takla-Hazelton Assemblage s i t t i n g unconformably on top of the Cache Creek Assemblage (Figure 8 , p. 96 ). a.  The lowermost Permian and/or E a r l i e r Anarchist Group proper, composed of c h e r t s , p h y l l i t e s , mica schists,greenstones and minor limestone lenses i s t y p i c a l of the more widespread  (Miss, to Lower T r i a s s i c ) Cache Creek Assemblage  (Campbell, 1966), c h a r a c t e r i s t i c of a deep water marine  98. offshore environment. b.  The Anarchist i s unconformably o v e r l a i n by a (Middle to Upper T r i a s s i c ) Sharpstone Conglomerate - Brooklyn Limestone - (Middle J u r a s s i c ) Fragmental Andesite sequence that i s t y p i c a l of the more widespread (Upper T r i a s s i c - Middle J u r a s s i c ) Takla-Hazelton Assemblage (Campbell, 1966).  Sharpstone Conglomerates form the basal section f o r the Middle Triassic clastic  sequence.  Both the Sharpstone Conglomerate - a r g i l l i t e and Brooklyn Limestone u n i t s t h i n to the southeast and east from the PhoenixOro Denoro areas, and the T r i a s s i c sediments become n o t i c e a b l y f i n e r - g r a i n e d i n t h i s same d i r e c t i o n , suggesting deposition f a r t h e r i n t o the basin (from the source area). T r i a s s i c c l a s t i c sedimentation probably accumulated w i t h i n n o r t h e r l y trending elongate basins, t r a n s p o r t a t i o n was from west to east and the source area f o r the Sharpstone Conglomerate probably was the Knob H i l l cherts and greenstones to the west and northeast. The Sharpstone Conglomerate and o v e r l y i n g Brooklyn Limestone sequence ("Ore sequence", Newell, 1969) forms a good marker u n i t throughout the Grand Forks-Eholt area, containing numerous primary and minor structures and some w e l l preserved f o s s i l s . New f o s s i l evidence, Halobia and Megaphyllites, confirms the Middle to Upper T r i a s s i c age f o r the beginning of deposition of the Sharpstone Conglomerate - Brooklyn Limestone sequences. The o l d timers'  1  "Puddingstone", previously mapped as a limestone  99. cobble agglomerate, l i e s g r a d a t i o n a l l y above the Sharpstone Conglomerate sequence and i s e s s e n t i a l l y a l i t h o l o g i c equivalent except that the Puddingstone has a maroon coloured matrix and contains f i n e l y disseminated hematite. 7.  Andesite p i l l o w s o v e r l y i n g a Brooklyn Limestone u n i t suggests that the unconformable Fragmental Andesites are i n part continuous with the end of carbonate deposition. There must have been some shallow carbonate d e p o s i t i n g basins s t i l l present at the onset of andesite volcanism.  8.  Pre-Permian to Middle J u r a s s i c sedimentary and v o l c a n i c rocks underlying the Grand Forks-Eholt area have undergone a r e l a t i v e l y low-grade of r e g i o n a l metamorphism t y p i c a l of the Greenschist Facies.  9.  The overturned western limb of a l a r g e , open, n e a r l y recumbent syncline that opens to the east and whose f o l d a x i s plunges gently fflE and a x i a l plane dips g e n t l y to moderately to the NW, i s o u t l i n e d w i t h i n the Sharpstone Conglomerate/Brooklyn  Lime-  stone/Fragmental Andesite Assemblage northeast of Thimble Mountain. This overturned limb appears to be p r o g r e s s i v e l y s h i f t e d westward from the Hummingbird area to the Oro Denoro-Emma v i c i n i t y . b y several N¥ trending s h e a r / f a u l t zones. South of Oro Denoro, the overturned western limb unfolds forming the gentle northeastward dipping western limb of a northwesterly plunging trough or basin. 10.  V a r i a t i o n s i n the plunge d i r e c t i o n s of minor f o l d axes and  100. hinge zones within the Brooklyn Limestone from a NNE  to a NW  d i r e c t i o n from north to south within the map area, suggest a marked warping of the major a x i a l plane and f o l d s x i s . 11.  The Republic Graben, a prominent Late Cretaceous to E a r l y Tertiary ME  trending structure i n Curlew County, N.Washington, loses  i t s i d e n t i t y to the north i n the Boundary D i s t r i c t - the Granby River Fault appears to be the northward extension of the Drummer Mountain Fault, the eastern boundary f a u l t i n northern Washington. A mylonite zone southwest of Eagle Mountain may  be  a northern extension of the Bacon Creek Fault, the western boundary f a u l t . 12.  A northwest and northeast conjugate fracture pattern predominates i n the Grand Forks area, s i m i l a r to Tertiary fracture patterns i n other areas of the southern Boundary and Okanagan districts.  13.  Northwest trending steeply dipping fault/shear zones are predominant and cut the Grand Forks-Eholt area at seemingly regular i n t e r v a l s . They a l l have r i g h t l a t e r a l horizontal apparent  dis-  placement i n the order of several thousand feet to several miles. 14.  Numerous d i a p i r i c , sheared, serpentinized ultramafic and pyroxenite bodies are confined to the northwest trending f a u l t zones within the map area. D i a p i r i c serpentinites suggest a source from depth and that these f a u l t s may at one time have been thrust planes.  101.  15.  Late Cretaceous  to Early T e r t i a r y d i o r i t e and gabbro intrusive  a c t i v i t y appears to be genetically related to and contemporaneous with movements along some of the prominent northwest f a u l t zones. 16.  Quartz-diorite and quartz-monzonite porphyries (Carswell's "Emma Intrusives") appear to be Late Cretaceous  to Early  T e r t i a r y i n age, may be genetically related to basic rocks, and appear confined to areas near the prominent northwest s t r u c t u r a l breaks. 17.  The quartz-diorite, quartz-monzonite porphyries are high l e v e l intrusions i n d i c a t i v e of high temperatures (600°-700°C) and associated low pressure conditions.  Suggestions f o r Further Work  1.  Detailed p e t r o l o g i c a l and chronological studies of the various i n t r u s i v e rocks i n the area.  2.  Detailed petrographic study to separate the fine-grained trachytic andesites from the Late Cretaceous-Early T e r t i a r y fine-grained quartz-monzonite and quartz-diorite porphyry i n t r u s i v e s . Also to separate the coarse-grained d i o r i t e i n t r u s i v e s from coarse-grained c r y s t a l l i n e andesites.  3.  A detailed study of minor structures, textures and f o s s i l evidences within the T r i a s s i c Sharpstone Conglomerate and Brooklyn Limestone to elucidate: number of units involved, f a c i e s changes, paleocurrents and l i t h o l o g y ; to determine directions of transport and source areas f o r the c l a s t i c  102. d e b r i s , the chronological r e l a t i o n s h i p s between the various layered u n i t s , and the d e p o s i t i o n a l environments. 4.  A d e t a i l e d s t r u c t u r a l a n a l y s i s of the Brooklyn Limestone and and underlying Sharpstone sequence - numerous primary and minor structures have been observed. One must work out the structures w i t h i n the i n d i v i d u a l f a u l t bounded blocks, keeping i n mind the T e r t i a r y block f a u l t i n g , approximate 45° t i l t i n g to east and gentle warping. Problem: T e r t i a r y cover has been eroded from most of the area.  5.  The study of Wollastonite w i t h i n the a r g i l l a c e o u s limestone hornfels and magnesium i n c a l c i t e (marble) as temperature i n d i c a t o r s f o r emplacement of the contact thermal aureoles surrounding the high l e v e l quartz-monzonite, q u a r t z - d i o r i t e porphyry i n t r u s i o n s i n the Hummingbird v i c i n i t y .  103. REFERENCES Brock, R.W., 1901. The Boundary Creek D i s t r i c t , B.C. Geol.Surv. Can. Summary Report 1901. ,1902. Preliminary Report on the Boundary Creek D i s t r i c t , B.C.; Geol.Surv.Can. Summary Report 1902. ,1905. Geological Map of the Boundary Creek Mining D i s t r i c t , B.C.; Geol.Surv.Can. Map 828. Campbell, R.B., 1966. Tectonic of the South Central C o r d i l l e r a of B r i t i s h Columbia; C.I.M.M. spec.vol. no. 8, pp.61-72. Carswell, H.T.,1957. Geology and Ore Deposits o f the Summit Camp, Boundary D i s t r i c t , B.C.; (unpubl.M.Sc.thesis, U.B.C.) Church, B.N.,1967. Geology of The White Lake Area. (unpubl.Ph.D. t h e s i s , U.B.C.) Daly, R.A., 1912. Geology of the North American C o r d i l l e r a of the 49th p a r a l l e l ; Geol.Surv.Can. Memoir 38. Drysdale, C.W.,1915. Geology of F r a n k l i n Camp, B r i t i s h Columbia; Geol.Surv.Can..memoir 56. Kerr, P.F.,1959. O p t i c a l Mineralogy. McGraw-Hill Book Co. I n c . Kulp, J.L., 1961. Geological Time Scale. 1105-1104.  Science, v o l . 133, pp.  LeRoy, D.E., 1912. Geology and Ore Deposits of Phoenix, Boundary D i s t r i c t , B r i t i s h Columbia. Geol.Surv.Can.,memoir 21. L i t t l e , H.W., 1957. K e t t l e River (East H a l f ) , Geol.Surv. Canada, Map 6-1957, 1957. Nelson Map Area (West H a l f ) , B r i t i s h Columbia. Geol.Surv.Can., memoir 308. —  and Thorpe, R.I., 1965. Greenwood (East H a l f ) : Geol.Surv. Can., paper 65-1.  L i v i n g s t o n e , W., 1970. Personal Communication. Mathews, W.H., 1964. Thirteen Potassium-Argon Dates of Cenozoic Volcanic Rocks from B r i t i s h Columbia; Univ. B r i t . C o l . , Dept. Geol., rept. no.2. -, 1964. Potassium Argon Determinations of Cenozoic Volcanic Rocks from B r i t i s h Columbia. Geol.Soc.Am.,bull.v.75, pp.465-468.  104. Monger, H.W.H., 1968. E a r l y T e r t i a r y S t r a t i f i e d Rocks, Greenwood Map Area, B r i t i s h Columbia. Geol.Surv.Can.,paper 67-42. Moore, R.C., 1957. Treatise of Invertebrate Paleontology, part L. Geol.Soc.America, Univ.Kansas Press, pp.179-180. .  , L a l i c k e r , and F i s c h e r , 1952. Invertebrate McGraw-Hill, pp.423-429.  McNaughton, D.A., 1945. Greenwood-Phoenix Geol.Surv.Can.,paper 45-20.  Fossils.  Area, B r i t i s h Columbia.  Newell, J.M., 1969. Report on Preliminary Reconnaissance Boundary D i s t r i c t , Greenwood Mining D i s t r i c t , B r i t i s h Columbia. Texas Gulf Sulphur Company, unpublished report. Parker, R.L. and C a l k i n s , H.A., 1964. Curlew Quadrangle, Ferry County, Washington. U.S.Geol.Surv.,bull.1169. Ross, J.V., 1970. Personal communication. , and C h r i s t i e , J . 1969. Geol.Soc.America, 65th Annual Meeting, A b s t r a c t , pt. 3, p.57. Preto, V.A.G., 1970. Personal Communication. Seraphim, R.H., 1956. Geology and Copper Deposits of the Boundary D i s t r i c t , B r i t i s h Columbia. C.I.M.M. vol.LJX, pp.684-695. S i n c l a i r , Nguyen, Libby, 1968. Age of the Northern Part of the Nelson B a t h o l i t h . Can.J.Earth S c i , v o l . 5 , p. 955. Sutherland-Brown, A., 1968. Lode Metals i n B r i t i s h Columbia, 1968. Report of the M i n i s t e r of Mines and Petroleum Resources, V i c t o r i a , pp.233-235. Tozer, E.T., 1970. Personal communication. Geol.Surv.Can.,Ottawa, Ontario. T r a v i s , R.B., 1955. C l a s s i f i c a t i o n Quart.,vol.50, no.1.  of Rocks. Colorado Sch.Mines,  Turner and Verhoogen, I960. Igneous and Metamorphic Petrology, 2nd. ed. McGraw-Hill, p.544 pp. Waters, A.C. and Krauskopf, K., 1941. P r o t o c l a s t i c Border of the C o l v i l l e B a t h o l i t h ; Geol.Soc.America, b u l l . , v o l . 52, no. 9, pp.1355-1417. White, W.H.,  1970. Personal Communication.  Williams, H., Turner, F.J., G i l b e r t , CM., 1954. Petrography; an i n t r o d u c t i o n to the Study of Rocks i n Thin Sections. W.H.Freeman and Co. Winkler, H.G.F., 1967. Petrogenesis of Metamorphic Rocks; 2nd.ed., New York, Springer Verlag Inc., pp.88-115. Yates, R.B., B e c r a f t , G.E., Campbell, A.B., and Pearson, R,C.,1966. Tectonic Framework of North-Eastern Washington, Northern Montana. C.I.M.M. spec.vol.no.8, pp.47-60.  106. APPENDIX I : ECONOMIC GEOLOGY Mining H i s t o r y Copper-bearing c a l c - s i l i c a t e skarn deposits w i t h i n the Grand PorksGreenwood area have been by f a r the most important metal producers i n the Boundary D i s t r i c t . F i r s t d i s c o v e r i e s  were made i n 1891 and by the  end of that year the three major mining camps: Deadwood camp, west of Greenwood; Phoenix and Summit camps between Grand Forks and Greenwood had been discovered. Granby Mining Company's f i r s t copper smelter, i n which 14 m i l l i o n s tons of ore were treated, was established a t Grand Forks i n 1900. Two other smelters were located a t Greenwood and Boundary F a l l s , between 1900 and 1919. During the years of 1898 and 1904, the Canadian P a c i f i c Railway  and Great Northern Railroad extended t h e i r  l i n e s to reach the town of Phoenix. Summit C i t y , now overrun by the present highway near the Oro Denoro workings, was established i n the l a t e 1890's and became the centre of the Summit camp; which included the Oro Denoro, Emma, Jumbo, Swallow, P y r r h o t i t e showings, Mount Rose, B l u e b e l l , B.C.,  and R.Bell  Mine workings(see g e o l o g i c a l map i n back f o l d e r ) . Total production from t h i s camp between 1899 and 1939 amounts to approximately 507,346 tons of shipped/treated ore; producing 17,981,427 pounds of copper, 326,863 oz. of s i l v e r and 507,536 oz. of gold, the majority of t h i s coming from the Oro Denoro, Emma and B.C. Mines (Carswell, 1957). The average grade f o r the camp was about 1.1% copper, 0.03 oz./ton Au and 0.25 oz./ton Ag. The d i s t r i c t s ' mining boom ended by 1920 and from then, u n t i l  107. Granby Mining Company resumed operation at Phoenix i n 1959, mining i n the d i s t r i c t was sporadic and on a small scale. The present Granby property at Phoenix encompasses the o l d Knob H i l l - I r o n s i d e s , BrooklynStemwinder and Snowshoe workings together with s e v e r a l smaller p r o p e r t i e s . T o t a l production up to 1966 amounts to approximately 19 m i l l i o n tons y i e l d i n g 750,000 ounces of gold, 416 m i l l i o n ounces of s i l v e r and 384.6 m i l l i o n pounds of copper. Current production i s at a r a t e of 2000 tons/day grading 0.65$ copper, 0.03 oz/ton Au and 0.15 oz/ton Ag. (Newell, 1969). Attwood Copper Mines Limited conducted e x p l o r a t i o n work throughout the Boundary d i s t r i c t from 1951-53 and extended the areas of known m i n e r a l i z a t i o n discovered by the o l d timers i n the Phoenix camp. Late i n 1955, Noranda E x p l o r a t i o n Company optioned 50 claims i n the Summit Camp and began d e t a i l e d property examinations. Recent h i s t o r y of the Boundary D i s t r i c t presents a p i c t u r e of g e n e r a l l y sporadic e x p l o r a t i o n , l a r g e l y d i r e c t e d towards r e a c t i v a t i n g o l d p r o p e r t i e s . Since the summer of 1967, many Vancouver-based companies have undertaken reconnaissance programmes i n the area.  Mineralization Copper skarn m i n e r a l i z a t i o n occurs t y p i c a l l y w i t h i n the a r g i l l a c e ous Brooklyn Limestone close to the underlying Sharpstone Conglomerate and adjacent to or near i n t r u s i v e bodies of Nelson g r a n o d i o r i t e or T e r t i a r y quartz-monzonite or q u a r t z - d i o r i t e porphyry. M e t a l l i c minerals are c h a l c o p y r i t e , p y r i t e , s p e c u l a r i t e , and magnetite, the l a t t e r being  108.  strongly developed i n the Summit Camp. Gangue i s variable, but almost always a c a l c - s i l i c a t e i n which c h l o r i t e , epidote, c a l c i t e , garnet, quartz and various amphiboles or pyroxenes are developed to d i f f e r e n t degrees; garnet, c a l c i t e and epidote predominating i n the Summit camp. At the Summit camp, sulphide minerals occur i n i r r e g u l a r fractures usually f i l l e d with c a l c i t e , and as i r r e g u l a r coarse-grained streaks, c l o t s and r e l a t i v e l y fine-grained disseminations. The orebodies, p a r t i c u l a r l y the high-grade sections, are i r r e g u l a r i n shape, but conform to the gross stratigraphy. High-grade ore was taken out of glory holes by the old timers. The B.C. mine i n the Summit camp, had the highest grade i n the Boundary D i s t r i c t averaging about 9$ copper during early production and having an o v e r a l l average grade of about 5.6$ copper up to 1901. The r i c h e s t mining camp of the Boundary D i s t r i c t , Phoenix, consists of much lower grade and larger mineralized areas than the Summit camp. Here the predominent metallic minerals are pyrite and chalcopyrite with minor specularite as opposed to magnetite and hematite of the Summit camp. The preponderence of c h l o r i t e , epidote and c a l c i t e gangue i n the skarn zone also d i f f e r s from the andradite  garnet and  epidote found at the Summit camp. Skarns of the Summit camp are products of contact metamorphism by the Kelson granodiorites, whereas Phoenix i s believed to be a pyrometasomatic skarn, since the nearest reported i n t r u s i v e i s several miles to the north. Several small skarn-type prospects carrying minor magnetite,  pyrite,  109. and chalcopyrite have been found within the Brooklyn Limestone adjacent to several small, i r r e g u l a r , quartz-diorite and  quartz-monzonite  porphyry bodies i n the northern part of the map area. These include the Rathmullen, S a i l o r Boy, Shickshock showings and several small workings northwest of Hardy Mountain and south of Eagle Mountain. Veins and shear zone mineralization occur  mostly within the Frag-  mental Andesite rocks and i n some cases within the underlying Brooklyn Limestone and Sharpstone Conglomerate sequence. This type of mineralization, i s ubiquitous and occurs as i r r e g u l a r veins and stringers of quartz and c a l c i t e with pyrite as the common s u l f i d e , but minor chalcopyrite and i n a few cases galena and sphalerite has been found. The diggings west of Hardy and Eagle Mountains are t y p i c a l examples that have not gone past the prospect stage. , P y r i t e , pyrrhotite, sphalerite and minor galena? occur as concent r a t i o n s along the apex of minor folds within a well-bedded, hornfelsed argillaceous limestone unit at the Hummingbird showing. This mineralizat i o n i s t y p i c a l of the high temperature contact thermal deposits surrounding high l e v e l , high temperature intrusions. Galena, sphalerite, p y r i t e and minor chalcopyrite? have also been found within granular, hornfelsed, bleached limestone (marble?) adjacent to several easterly trending quartz-monzonite  porphyry dykes south of Eagle Mountain.  Several small pyrrhotite, pyrite and minor chalcopyrite massive sulphide showings are found within intensely sheared areas underlain by s i l i c e o u s rocks of the Anarchist Group. The Packrat showing located about 1-jjr miles northeast of the B.C. mine i s a t y p i c a l example. Here  110. about  2000  tons of massive sulphides have been .stockpiled and i t appears  that very l i t t l e i f any has been shipped.  111.  APPENDIX I I FOSSIL LOCATION AND DESCRIPTIONS  1. Found i n outcrop AR322 along the southern P r o v i n c i a l Highway approximately 1 mile south of the Oro Denoro workings. Numerous black to dark broken, flattened, often overlapping casts and impressions of the pelecypod Halobia or r e l a t e d Daonella. Several of the fragments up to 1" across, compressed p a r a l l e l to bedding, show the general outline of the pectinoid pelecypod and strongly developed plicae.They occur within the pale grey to tan microc r y s t a l l i n e limestone unit of the Brooklyn Limestone. Suggests a shallow water  environment.  Halobia  an early or medial Late T r i a s s i c  Daonella  much larger range from Mid.-Late  age. Triassic.  2. Found i n outcrop AR251C. a large r a i l r o a d cut along the Canadian P a c i f i c Railway tracks approximately  mile south of Neff Creek.  Numerous, up to 1-2$ of the whole rock, broken c r i n o i d stems, 2-3 mm i n diameter and 3-4 times as long, have been found l y i n g p a r a l l e l to the bedding plane with random orientations. The host rock i s a fine-grained dark grey argillaceous limestone. The  crinoid  stems are composed of white, c r y s t a l l i n e , sparry? c a l c i t e or dolomite and appear to be t o t a l l y  recrystallized.  3. AR432A located approximately -jp-f mile south of Goat Mountain. Consists of numerous minute p a r t i a l l y r e c r y s t a l l i z e d ammonoids set i n a fine-grained dark grey to black well bedded argillaceous limestone. They are very small, generally from 1-5 mm,  typically  112.  subglobose, involute, low arched venter, smooth, exhibit c e r a t i t i c sutures with large number of elements, approximately s i x i n mature specimens (see Figures 9 and 10, pp. 113 and 114). The ammonoid has been t e n t a t i v e l y i d e n t i f i e d as possibly genus Megaphyllites or maybe Parapopanoceras  Range  by E.T. Tozer (personal communication, 1970).  order  Ammonoidea  suborder  Ceratitina  superfamily  Arcestaceae  family  Megaphyllitidae  genus  Megaphyllites  -  Megaphyllites  Norian  Mid-Upper T r i a s s i c  Anisian  lowest Middle T r i a s s i c .  Genus  Megaphyllites  (Mid. - Upper T r i a s s i c )  subglobose, involute, low arched ventre, smooth, c e r a t i t i c suture with large number of elements.  Figure  9  Sketch and measurements of Megaphyllites.  Suture Patterns  Mature  f  The juvenile (early) whorls appear to have goniatitic sutures suggesting a very primitive ceratitic suture type.  Figure  10  Mature to juvenile suture patterns of Megaphyllites.  

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