GMEG - Mineral and Environmental Resources
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This task aims to improve fundamental understanding of the relationship between Proterozoic basin evolution and genesis of sediment-hosted copper deposits, focusing on the Belt basin in Montana and Idaho, and the generation of its copper (+silver) deposits. The task aims to elucidate factors that define the regional scale mineralizing system, for example:
Focus will be on the genesis of sediment-hosted Cu-Ag deposits in the Revett Formation of the Proterozoic Belt Supergroup in northwest Montana and northern Idaho, and will attempt to place fundamental constraints on the origin, migration and precipitation of ore deposit components. That information will be integrated with new data that is emerging on the tectonic and sedimentologic evolution of the basin, resulting in the definition of the following:
Sedimentary exhalative deposits develop in a sedimentary basin by the submarine venting of metal-rich hydrothermal fluids which precipitate to form sedimentary layers rich in sulfide minerals of lead and zinc, and in some cases copper and cobalt.. This task will focus on these types of base- and precious metal deposits in the Prichard Formation and equivalents within the Belt Supergroup of western Montana and Idaho. We will attempt to establish the variations in sources, processes, and timing of fluid migration and ore formation in the context of basin evolution and tectonic processes active at the time. The results should be useful in future exploration in the Belt and in other Proterozoic rocks around the world.
In order to compile these results this task will:
Thick sequences of Proterozoic siliciclastic rocks in the western U.S. contain or are subjacent to world-class metal deposits; respective examples are the Coeur d’Alene (Ag-Cu) district in northern Idaho, and the Carlin (Au) Trend in the Great Basin of north-central Nevada. This task will determine selected primary modal and chemical compositions of both sequences of siliciclastic rocks, in conjunction with investigations under Tasks 1 and 2, and compare the impact of diagenesis, catagenesis, metamorphism, and magmatism on those compositions to ascertain the relative importance of provenance and process in the metallogeny of the two sequences.
The ultimate goal of this Task is to distinguish between Proterozoic strata that contain metallic mineral resources from those that contributed components of such resources. Identification of differences in composition and post-depositional processes that affected Proterozoic strata will contribute toward improvement of exploration success and assessment accuracy.
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