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Petrology of the Shingle Creek porphyry

University of British Columbia

A brief description of the geology of the Shingle Creek area southwest of Penticton B.C. together with a more detailed report on the mineralogy and petrology of the Shingle Creek Intrusion (granite porphyry) are given. The presence of flows and tuffs showing similar mineralogical features to the Shingle Creek: Intrusion suggest that this intrusion was shallow rather than deep-seated. Sanidine phenocrysts showing oscillatory zoning are described with a range in composition of from 40 to 70 percent orthoclase (based on a comparison of optical properties with those determined by Tuttle 1952). The zones often occur in pairs showing a gradation from an albite-rich inner zone to an orthoclase-rich outer gone, It is tentatively suggested here that pressure changes in the magma, by altering the liquidus - solidus relations, sight provide this reversed- zoning. Plagioclase phenocrysts from the intrusion show transitional to high temperature optics when compared with the results of Bowen and Tuttle 1950. Beta quartz phenocrysts showing rounded outlines and development of late halos are described, from evidence given it is suggested that these features are due to resorption of quartz in a magma chamber prior to intrusion, followed by late growth after intrusion and daring crystallization of the porphyry matrix, Petrographlc study of the largest dyke associated with the porphyritic intrusion has suggested that this dyke may have been intruded in several stages.

Text

2012-03-21

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http://hdl.handle.net/2429/41666

Geography

University of British Columbia

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