Geology and mineral deposits of the Pyramid district, southern Washoe County, Nevada
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Authors
Wallace, Andy Bert
Issue Date
1975
Type
Dissertation
Language
en_US
Keywords
Pyramid District , Nevada , Pah Rah Range , Mineralization , Veins , Fracture Zones , Faults , Late Oligocene Ash-flow Tuffs , Miocene Ash-flow Tuffs , Hartford Hill Rhyolite , Vein Mineralization , Disseminated Copper , Molybdenum Mineralization , Guanomi Quartz Monzonite Stock , Post-mineralization Rocks , Dacite Stocks , Dacite Lavas , Lacustrine Sediments , Basaltic Tuff-breccias , Basalt Flows , Ash-flow Tuff Of The Pyramid Sequence , Hypogene Mineralization , Mackay Theses and Dissertations Grant Collection
Alternative Title
Abstract
The Pyramid district is thirty miles north-northeast of Reno, Nevada in the northern Pah Rah Range. Known mineralization in the district is confined to west and northwest trending veins along fracture zones and faults cutting the Late Oligocene to Miocene ash-flow tuffs of the Hartford Hill Rhyolite. The vein mineralization is only slightly younger (1-3 million years) than disseminated copper and molybdenum mineralization in the Guanomi quartz monzonite stock exposed six miles from the district. Post-mineralization rocks in the area include dacite stocks and lavas, and also lacustrine sediments, basaltic tuff-breccias, basalt flows, and ash- flow tuffs of the Pyramid Sequence. Hypogene mineralization in the district displays well- defined zoning with a central enargite (luzonite)-pyrite zone, an intermediate polymetallic zone with tetrahedrite, sphalerite, galena, chalcopyrite, bornite, and pyrite, and an outer zone with galena and pyrite. The ash-flow tuffs of the Hartford Hill are pervasively propylitized with sericitic envelopes around veins, and in the central enargite-pyrite zone, advanced argillic alteration occurs between the veins and the sericitic envelopes. Mineralization in the Pyramid district is similar to several Peruvian polymetallic vein systems, Butte, Montana, Chinkuashih, Taiwan, several Japanese polymetallic vein deposits, and also to districts in the San Juan Mountains of Colorado. At least one of the polymetallic vein systems in Peru (Morococha) is known to directly overlie a porphyry copper deposit and it is suggested that such an exploration target may lie beneath the central zone of the Pyramid district.
Description
Thesis Number: 955.
Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.
Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.
Citation
Publisher
University of Nevada, Reno
License
In Copyright(All Rights Reserved)