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Galena lead isotope study of mineral deposits in the Eagle Bay Formation, southeastern British Columbia

University of British Columbia

The Eagle Bay Formation in the Adams Plateau-Clearwater area, 35km northeast of Kamloops, hosts several economic and sub-economic mineralized occurrences. The age and genesis of these mineral deposits can be estimated by using a specific growth curve which depicts the lead evolution for the Eagle Bay Formation. This curve, named the remodeled curve, represents a local deviation from the average 'shale' curve of Godwin and Sinclair (1982) for the autochthonous part of the Canadian Cordillera. This remodeled curve is specifically applicable to the Adams Plateau-Clearwater area. The lead isotope data from the deposits of the Eagle Bay Formation plot in three distinct clusters along the curve indicating that the lead isotopic signature of the Eagle Bay Formation is upper crustal, and that three periods of mineralization can be recognized or 'fingerprinted'. Accordingly, mineralization cogenetic with Devonian volcanism, and veins related to Cretaceous magmatism can be distinguished by location of galena-lead isotope values within clusters 1 or 3 respectively. Cluster 2 reflects a Late Triassic pulse of mineralization and includes epigenetic veins and stratiform deposits. These deposits are either replacement or cogenetic with their host. The Triassic model age for mineralization that is apparently stratiform and cogenetic raises questions about the currently assigned Cambrian age of associated host rock. To accommodate the lead isotope data a new Upper Triassic unit (T-EBG) within the Eagle Bay Formation is defined. The distinctive lead isotopic signature between deposits hosted by the Eagle Bay Formation is valuable as a guide for future mineral exploration programs in the Adams Plateau-Clearwater area. Recognition of lead isotopic fields that fingerprint types of mineral deposits, provides a useful and practical framework for the classification and evaluation of new mineralized prospects in the area.

Text

2010-07-09

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http://hdl.handle.net/2429/26264

Geological Sciences

University of British Columbia

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