The Geology and Geochronology of the Echo Bay Area, Northwest Territories, Canada
In the Echo Bay region of Great Bear Lake the Echo Bay Group has been intruded by Precambrian granites, granodiorites, aplites, and diabases. This group, which has undergone zeolite-facies regional metamorphism, has a lower dominantly sedimentary-pyroclastic sequence (about 1320 m thick) and an uppe...
Published in: | Canadian Journal of Earth Sciences |
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Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Canadian Science Publishing
1972
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Subjects: | |
Online Access: | http://dx.doi.org/10.1139/e72-013 http://www.nrcresearchpress.com/doi/pdf/10.1139/e72-013 |
Summary: | In the Echo Bay region of Great Bear Lake the Echo Bay Group has been intruded by Precambrian granites, granodiorites, aplites, and diabases. This group, which has undergone zeolite-facies regional metamorphism, has a lower dominantly sedimentary-pyroclastic sequence (about 1320 m thick) and an upper volcanic sequence (> 1500 m thick). The Lower Echo Bay sub-Group consists of tuffs and cherts with a 190 m thick intermediate lava flow and occasional thin limestones. A sequence of andesites and pyroclastics comprises the Upper Echo Bay sub-Group. Contact metamorphism of the hornblende hornfels and albite–epidote hornfels facies has been induced by the granitic intrusions. A Rb–Sr isochron for the Upper Echo Bay sub-group volcanics gives an age of 1770 ± 30 m.y. K–Ar apparent ages for the granite, granodiorite, and volcanics average around 1650 m.y., possibly reflecting local argon loss up to this date. Mineralized veins with a pitchblende-Co,Ni arsenide-silver-Fe, Cu, Ag, Bi, Zn. Pb sulfide para genesis are mainly confined to the sedimentary-pyroclastic horizons of the Lower Echo Bay sub-Group. It is possible that the mineralization was effected by fluids generated during the low-grade regional metamorphism and that some contribution was made to ore genesis by the thermal regime developed during the diabase intrusion. |
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