Magmatic-Tectonic History and Component Sources of Major Precious Metal Deposits in the Tonopah, Goldfield, and Comstock Lode Districts, NV Completed

Science Issue and Relevance

Large, exposed mineral resources have sustained economies and stabilized social order worldwide for centuries. Future mineral supplies will be obtained from concealed resources, which must be higher grade for unsubsidized extraction. Lithospheric-scale (crust and upper mantle) investigations of large, high-grade metal deposits are fundamental to identifying concealed resources with sufficient unit value to mine with existing technology. Determination of sources of igneous host rocks and components of hydrothermal minerals in such world-class gold-silver-copper (Au-Ag-Cu) deposits as Tonopah, Goldfield and Comstock Lode, Nevada, is a basic requirement for understanding the magmatic and hydrothermal processes that form these deposits, and for predicting the location of similar, concealed deposits. 

Project results are expected to include refined geologic and tectonic maps of important districts in the Walker Lane, reduced uncertainty in sources of elements in ore deposits, improved precious metal deposit models, and refined provincial and local scale exploration concepts for concealed, high-grade, gold-silver deposits.

Methodology to Address Issue

During previous research in the Southern Walker Lane, a systematic investigation was begun of the sources of igneous and hydrothermal mineral components in three significant, subduction-related, Au-Ag-Cu districts in Miocene volcanic fields in western Nevada and eastern California (Goldfield and Tonopah, NV, Bodie Hills, CA-NV). This investigation employed multiple methods including mapping of volcanic stratigraphy, geochronology, and geochemical and isotopic analyses. Although studies were completed in the Bodie Hills, they were not completed in the Goldfield and Tonopah districts. The Comstock Lode Au-Ag district was added to the current investigation because of its world-class size and grade, and the existence of significant legacy data. Our objectives are refinement of stratigraphy, structure, and magmatic-hydrothermal evolution of the Tonopah, Goldfield, and Comstock Lode districts, and determination of the sources of hydrothermal mineral components.