A RELATIONAL DATABASE FOR MIOCENE TO HOLOCENE IGNEOUS ROCKS OF THE GREAT BASIN, WESTERN USA: IMPLICATIONS FOR PETROGENESIS AND MINERAL DEPOSIT RESEARCH

As part of a regional study of metallogeny in the Great Basin, Western USA, we have compiled a relational database for Miocene to Holocene igneous rocks. Database tables are linked to other geospatial earth-science data including isotopic age, geochemistry, environment of deposition or emplacement, tectonic setting, and associated mineral deposits. Voluminous published and unpublished data are being compiled in an atlas format and made retrievable via web access. The database is designed to study the relationship of bimodal magmatism to mineral deposits, especially the formation of these volcanic systems during hot-spot impingement, extension-related crustal thinning, and mantle upwelling during regional extension. We will focus on northern Nevada to examine how these volcanic systems contributed to the formation of many significant epithermal deposits in the region. Although the bimodal assemblage locally includes intermediate (trachydacite) compositions, the dominant lithologies are basalt, basaltic andesite, and rhyolite. The mafic units are well exposed in the 16.4-15.8 Ma northern Nevada rift-Mule Canyon sequence near Battle Mountain and the base of the ~16.5-14.8 Ma volcanic sequence in the Santa Rosa Range north of Winnemucca. Contemporaneous silicic domes and flows were erupted throughout northern Nevada; most lack biotite and hornblende; although, those in and near the Santa Rosa Range contain hydrous phases. Felsic units include the 16.5 – 15.6 Ma McDermitt caldera complex near the Idaho border, 15.2-14.9 Ma silicic lava domes in the Ivanhoe and Midas districts, and the widespread ~14-16 Ma Jarbidge Rhyolite north of Elko. Associated mineral deposits are mostly low-sulfidation epithermal gold-silver deposits (e.g., Midas, Sleeper, Mule Canyon, Jarbidge); however, significant hot-spring mercury and Ga (McDermitt) Li, and U resources are also present. Our ultimate goals include: producing a regional compilation of the attributes and locations of bimodal volcanic rocks in the region; analyzing these data to better understand the petrogenesis of these volcanic systems; and linking these data to related epithermal ore-deposit research. Also importantly, the database will identify knowledge gaps that can help guide future research. We invite the participation of interested colleagues.