Download or read book Geochemical Petrologic and Isotopic Investigation of Andesites and Related Volcanic Rocks in the Santa Rosa Range and Bloody Run Hills Nevada written by Mark Gene Mellott and published by . This book was released on 1987 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bibliography and Index of Geology written by and published by . This book was released on 1988 with total page 1060 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petrology and Geochemistry of the Emigrant Pass Volcanics Nevada written by Curtis Lawrence Johnson and published by . This book was released on 2015 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Emigrant Pass volcanics (EPV) are a 38.3 to 36.4 Ma calc-alkaline volcanic center that erupted andesite and dacite, and a late series of felsic dikes along the south flank of the Carlin gold district in north-central Nevada. The EPV includes dacite and rhyolite porphyry dikes indistinguishable from porphyry dikes associated with mineralization within the district. The volcanic rocks likely represent eruptive equivalents of deeper, unexposed Eocene plutons that may be the source of heat, fluids, and metals of Carlin-type gold deposits. New petrologic and geochemical data of the EPV are presented to test this hypothesis. The EPV are exposed over a 30 x 15 km area, have an estimated volume of 100 to>200 km3 and are divided into the early Primeaux lavas (38.1-38.3 Ma), the Mack Creek lavas and related intrusions (37.1-38.4 Ma), and late eruptive and hypabyssal rocks (Henry and Faulds, 1999). The Primeaux lavas are a>500 m thick sequence of pyroxene and hornblende andesite to dacite lavas and intrusions; minor pyroxene, hornblende and biotite dikes; and volcanic conglomerates. The Mack Creek lavas are a 180 m thick succession of porphyritic dacite lava flows, domes, and intrusions. Late small-volume units include the Bob Creek basaltic andesite to andesite lava (37.7 Ma) and rhyolitic to dacitic dikes (36.4-36.7 Ma). Primeaux andesite crystallized early clinopyroxene, orthopyroxene, plagioclase, and late hornblende, which suggests moderate water contents (~3 wt.%). Mack Creek dacite and late rhyolite-dacite dikes crystallized hornblende and biotite early, attesting to high water contents (>4 wt.%). Early Primeaux andesites contain abundant magnetite and sparse ilmenite, whereas Mack Creek dacites and late rhyolite-dacite dikes contain magnetite and local titanite. This mineralogy is consistent with the evolution of magmas from early moderately oxidized conditions to late strongly oxidized conditions (fO2 e"NNO+2) similar to porphyry copper magmas (Dilles, 1987). Carlin plagioclase-biotite-hornblende dacite porphyry dikes associated with gold ores yielded four new LA-ICP-MS U/Pb zircon ages (36.7±1.8, 38.8±1.7, 39.2±1.6, 39.4±1.5 Ma), overlapping in age with the earliest EPV eruptions. Two additional U/Pb zircon ages were obtained on a coarsely porphyritic dacite lava of the Mack Creek sequence (37.10±0.54 Ma), and a porphyritic dacite lava (148.2±2.3 Ma) likely of the Frenchie Creek Volcanics at the southern terminus of the EPV. All analyzed Carlin porphyries contain zircons with EuN/EuN* versus Hf arrays and EuN/EuN*> 0.4 similar to porphyry copper plutons (Dilles et al., 2015) and the 36 Ma Battle Mountain granodiorite porphyry associated with Cu(Au) ores (Farmer, 2013). Abundant partially melted granite xenoliths in EPV rocks indicate assimilation of crust during magma generation, whereas incompletely mixed magmas with differing mineralogy along with abundantly sieved plagioclase and resorbed amphibole indicate magma mixing processes. The andesites and dacites have high-K to shoshonitic compositions similar to subduction-related arc magmas. Whereas most major elements display simple linear correlations with silica, interpreted to indicate mixing, the MgO and Cr of most samples abruptly decrease with increased silica consistent with crystal fractionation. Dacites of the Mack Creek have elevated MgO and Cr compared to Primeaux andesites and Bob Creek basaltic-andesites, consistent with mixing of primitive basaltic andesite or andesite with rhyolite. Enrichment in Rb, Ba, and Cs indicate crustal additions compared to average arc magmas, whereas elevated V/Sc (1.4-17.3; Mean: 8.9) and Sr/Y (16.6-49.6; Mean: 36.1) ratios are similar to mineralizing porphyry Cu (Au) magmas (Loucks, 2014). Hornblende compositions from four samples are bimodal and include both low-Al and high-Al amphiboles now commonly recognized in arc suites (Aucanquilcha, Chile: Walker et al., 2013; Yanacocha, Peru: Chambefort et al., 2013). Using the Ridolfi et al. (2010) formulation, the low-Al hornblende crystallized at 820-890°C and 100-250 MPa (4-10 km depth), whereas high-Al amphibole crystallized at about 900-980°C and possibly greater depths. Electron microprobe studies of magmatic sulfide inclusions indicate monosulfide solid solution (MSS, pyrrhotite at low temperatures) was the dominant magmatic sulfide species with minor (n=4 of 119 analyses) intermediate solid solution (ISS, chalcopyrite at low temperatures). Sulfide contents decrease systematically as the magmas evolved from andesite-dacite-rhyolite, supporting the observation of increasing oxidation state and magmatic sulfate/sulfide ratio. Additionally, all phases of the EPV are highly depleted in whole rock Cu (
Download or read book Andean Magmatism written by Russell S. Harmon and published by . This book was released on 1984 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemical Evidence on the Nature of the Basement Rocks of the Sierra Nevada California written by and published by . This book was released on 1981 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemical database for intrusive rocks of northcentral and northeast Nevada written by and published by DIANE Publishing. This book was released on with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book University of Nevada Bulletin written by Nevada Bureau of Mines and published by . This book was released on 1967 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book R010 Isotopic age determinations of Nevada rocks written by and published by NV Bureau of Mines & Geology. This book was released on with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book SP035 A Geologic and Natural History Tour Through Nevada and Arizona Along U S Highway 93 written by Joseph V. Tingley and published by NV Bureau of Mines & Geology. This book was released on 2010 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geologic Studies in the Basin and Range Colorado Plateau Transition in Southeastern Nevada Southwestern Utah and Northwestern Arizona 1995 written by Florian Maldonado and published by . This book was released on 1997 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Final Report Geological Geophysical Chemical and Hydrological Investigations of the Sand Springs Range written by University of Nevada System. Desert Research Institute and published by . This book was released on 1964 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemical Reconnaissance of the Santa Rita Mountains Southeast of Tucson Arizona written by Harald Drewes and published by . This book was released on 1973 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace elements in alluvium and altered rock, recognized by geologic investigation previously reported, indicate some areas of potential economic interest along faults or near ore-associated intrusives.
Download or read book Geology and Ore Deposits of the Bullfrog District Nevada written by Frederick Leslie Ransome and published by . This book was released on 1910 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology of the Atomic Energy Commission Nevada Proving Grounds Area Nevada written by Mike S. Johnson and published by . This book was released on 1957 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: A stratigraphic and structural study of Yucca and Frenchman Flats.
Download or read book Great Basin and Sierra Nevada written by David R. Lageson and published by Geological Society of America. This book was released on 2000-01-01 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bulletin Nevada Bureau of Mines and Geology written by Nevada Bureau of Mines and Geology and published by . This book was released on 1972 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Environmental Isotopic and Hydrogeochemical Investigation of Recharge and Subsurface Flow in Eagle Valley Nevada written by James E. Szecsody and published by . This book was released on 1983 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
