SUCCESSION OF MAGMATIC-HYDROTHERMAL EVENTS IN THE PATAGONIA MOUNTAINS, AZ

The Patagonia Mountains of southern AZ consist of Precambrian granitic rocks, Paleozoic and Mesozoic sedimentary and volcanic rocks, and a core of Laramide intrusive rocks that comprise the Patagonia Mountains pluton. Laramide intrusions and adjacent rocks contain 2 porphyry Cu (PC) deposits (~0.6 and 1.5 Gt @ 0.6 and 0.3 % Cu, resp., 0.01 % Mo), Mo-Cu breccia deposits (~4-8 Mt @ ≤ 1.2 % Cu, 0.24 % Mo), and numerous replacement (~0.5 to 6.5 Mt @ ≤ 16 % Cu+Pb+Zn+Mn, ≤ 5 opt Ag) and vein deposits (≤ 0.26 Mt @ ≤ 22 % Cu+Pb+Zn, ≤ 40 opt Ag). U-Pb and ⁴⁰Ar/³⁹Ar mineral ages define 6 Laramide magmatic-hydrothermal events that span 16 m.y., from 74 to 58 Ma. Skarn deposits at Washington Camp-Duquesne are spatially associated with the 74 Ma Washington Camp stock, but some or all of the deposits could be 60 Ma, the age of large-volume quartz monzonite and granodiorite that comprise the southern part of the pluton and surround the Washington Camp district. Widespread trachyandesite in the northern part of the range and K-mica in a vein at the Flux carbonate replacement deposit are ~71 Ma, but uncertain paragenetic relationships preclude association of Flux to trachyandesite volcanism. The Ventura Mo-Cu breccia deposit is related to a 65 Ma granodiorite stock, one of several 65-63 small-volume intrusions of the pluton. Mineralized (cpy-bn) quartz monzonite porphyry in the Red Mountain PC system at the northern end of the range is 62 Ma; a near surface cc-en resource associated with advanced argillic alteration is paragenetically younger but not firmly dated. The 60 Ma Cu-Mo breccia deposit at Red Hill (Four Metals mine), in the southern part of the pluton, may mark a degassing conduit in large-volume granodiorite. The 61-58 Ma Sunnyside PC system consists of a deep cpy resource, and a near-surface cc-en-tn resource, although individual events comprising the system have not been adequately resolved. Vein and replacement deposits at the northern end of the pluton, including the Hardshell Ag-Mn resource, are thought to be distal deposits of the Sunnyside and Red Mountain systems. Other long-lived magmatic successions that include PC deposits (PCD) are the Oquirrh-Wasatch magmatic trend, UT (Bingham PCD), the Boulder batholith, MT (Butte PCD and vein deposits), and the Pima district, AZ (Mission and Sierrita PCDs); all lasted ~ 17 m.y.