Age and Lithogeochemistry of Volcanic-hosted Massive Sulfide Deposits of the Ambler District, Southern Brooks Range, Alaska

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McClellandEAR-0208162Modern examples of volcanic-hosted massive sulfide (VMS) deposits suggest that hydrothermal activity associated with formation of these deposits is a steady-state process. In contrast, ancient examples typically define distinct age groups and recent genetic models relate VMS mineralization to specific tectonic events such as incipient intra-arc rifting. Distinction between steady state and punctual models for VMS mineralization requires high precision geochronologic data to establish the duration of magmatism at the scale of individual deposits and to establish correlation, distinction, or migration of magmatism observed at the regional scale. The widespread occurrence of Devonian to Mississippian VMS deposits in the northern North American Cordillera provides an ideal setting to examine this issue. U-Pb geochronology and Nd-Sr isotope geochemistry combined with major, trace, and REE geochemistry of felsic and mafic rocks associated with mineralization and hydrothermal alteration will establish the age and tectonic setting of VMS mineralization in the Ambler district, southern Brooks Range, Alaska. The resulting database will serve as a basis for comparison with and evaluation of broadly age equivalent VMS deposits in the Yukon-Tanana terrane as well as sediment-hosted deposits within adjacent terranes and the Cordilleran miogeocline. The results of this project will provide valuable insight into the temporal and tectonic setting of VMS mineralization throughout the northern Cordillera. This insight will potentially lead to the generation of new genetic models for the evolution and preservation of VMS deposits in additional settings. The project will also address the long-standing question of the tectonic setting of mid-Paleozoic magmatism in the Cordillera.