DIVERSE STYLES AND AGES OF BASE, PRECIOUS METAL, AND PGE MINERALIZATION AT GOODSPRINGS, NV

The areally extensive Goodsprings district comprises three styles of epigenetic mineralization: (a) largely stratiform Zn+Pb±Ag deposits restricted to a thin interval of Mississippian carbonate rocks, (b) gold deposits in contact zones of Jurassic megacrystic granite porphyry dikes and sills that intruded Paleozoic and Triassic carbonate rocks, and, (c) discordant Cu±Ag-Au-PGE fissure deposits in Paleozoic carbonate strata that are zoned around the c.200 Ma porphyritic intrusions. All deposits are partly cospatial and occur in both plates of the regional Keystone thrust fault that is thought to have originated in the late Mesozoic. Deposit styles, distribution, and assumed ages require no more than several kilometers of compression along the Keystone fault in the Goodsprings district.

Paragenesis is obscured by deep oxidation but the deposits possess contrasting S and Pb isotope compositions that suggest at least two component sources and depositional ages. Zn+Pb deposits at Goodsprings and in the vicinity of Las Vegas display MVT characteristics, including wide distribution of strata-bound deposits in a platform carbonate sequence that abuts the Proterozoic craton margin, dolomite host rocks that have undergone dissolution, simple sulfide mineralogy, highly radiogenic leads (206/204 ³ 21) indicative of upper crustal sources, and probable late Paleozoic age. Jurassic intrusion-related Au and Cu±Ag-Au-PGE fissure deposits contain less radiogenic lead (206/204 » 18), are depleted in d³⁴S relative to Zn+Pb deposits (0±1 vs. 6±2‰, respectively), and have derived components from homogenized crust and/or mantle sources. PGE occurrences at Goodsprings, in southern NV, and in southeastern CA, uncommon elsewhere in the Great Basin, allow for additional igneous and hydrothermal PGE resources in Paleozoic and subjacent cratonal rocks.

Multiple periods of mineralization at Goodsprings as well as in other Great Basin districts constitute an under-utilized datum for quantifying aspects of tectonic and igneous events.