A proposed epithermal model for the high grade district, California

Abstract

A historic gold mining district in northeastern California has not been incorporated into the global knowledge base for precious metal vein deposits. This study collected various data types which are important characteristics in the classification and understanding of vein deposits. The High Grade District (HGD) is a gold mining site located in the northeast corner of Modoc County, California, in the Warner Mountains. The Warner Mountains are composed of Tertiary eruptive centers, cropping out between valleys formed through extensional tectonics. Mineralization of the HGD displays abundant silicification, adularia, and gold; these characteristics are sufficient to classify mineralization as low-sulfidation epithermal and warrants exploration activities to test models of this specific type. This study integrates local field mapping and hard-rock sampling with numerous laboratory methods to characterize the mineralizing system and test the classic epithermal model.

390 rock samples were collected and geologic maps were constructed. Rock samples are analyzed for elemental abundances, fluid inclusion studies, thin/polished section microscopy, and electron microprobe analyses were performed. Geochemical results were processed statistically with JMP software, surfaces modeled in Golden Software's Surfer, and visually interpreted in ArcGIS. This study constrains the timing of mineralization with Ar⁴⁰/Ar³⁹ dates and generates a data set of δ¹⁸O values in the HGD. This new knowledge base can be used to guide later economic and scientific endeavors to better understand the mineralization encountered in the HGD. The addition of data from this study to the global knowledge base, surrounding epithermal vein deposits, makes our collective scientific understanding of this topic more complete.