Download or read book Geology and Geochemistry of the Little Walker Volcanic Center Mono County California written by George R. Priest and published by . This book was released on 1979 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed mapping and geochemical analysis of Oligocene to early Pliocene volcanic rocks in the Little Walker volcanic center, Mono County, California have revealed a complex eruptive history. After eruption of widespread rhyolitic ash flows of the Valley Springs Formation in the Oligocene, Miocene to early Pliocene volcanism of the western Great Basin and northern Sierra Nevada was dominated by eruption of calc-alkalic, andesitic lavas bearing abundant hydrous mafic phenocrysts, and, thus, high H2O contents. These kinds of calc-alkaline magmas are associated with most of the major epithermal Au-Ag districts of the western Great Basin. A highly potassic latitic pulse of volcanism occurred at the Little Walker volcanic center about 9.5 m.y. ago during the ongoing calc-alkalic activity. The latitic series is unusually enriched in K and other incompatible elements, as well as Fe compared to the surrounding calc-alkaline rocks. The latites have mineralogic evidence of much lower H2O content than the calc-alkaline lavas; yet early latitic magmas were rich enough in volatiles to produce very large, welded ash-flow sheets (e.g., the Eureka Valley Tuff). Rapid evacuation of the magma reservoir beneath the Little Walker center during the ash-flow activity resulted in formation of the Little Walker caldera. Intracaldera volcanism culminated with extrusion of viscous, phenocryst-rich plug domes and coulees of transitionally calc-alkaline, low-K latite lava of the Lavas of Mahogany Ridge. The low-K latite series is severely depleted in all incompatible elements relative to early latitic rocks and has mineralogic, geologic, and trace element evidence of higher H2O content relative to early latites. Significant phenocrystic hornblende, association with hydrothermal alteration, and high Eu3 /Eu2 all suggest significant H2O concentration in the low-K latite magmas. These rocks probably come from a source region intermediate between that of the calc-alkaline and latite series. Trace and major element data favor generation of latitic magmas from a primitive mantle diapir. The diapir rose into a subduction zone that was actively generating widespread calc-alkalic lavas throughout the region from hydrous mantle and, possibly, lower crustal sources. The latite magmas were drier and hotter than the calc-alkaline magmas, but were also enriched in volatiles, particularly CO2, and incompatible elements from their undepleted mantle source. Rising latitic magmas may have gained additional incompatible elements by wall rock reaction and zone refining of upper mantle and lower crustal rocks. Extensive qualitative trace element evidence of crystal fractionation shows that incompatible elements may have been further concentrated by variable amounts of crystal settling. High-pressure (plagioclase-poor, pyroxene-rich) fractionation of the early, dry latitic series produced low-Ca-Mg latites with high Fe/Mg and A1203 but low Si02. Low-pressure (plagioclase rich) differentiation of the early latitic magmas produced quartz latite ash flows with high Si02 and moderate Fe/Mg, while low-pressure differentiation of hydrous low-K latite magmas yielded silicic low-K latite and quartz latite lavas with low Fe/Mg. More extensive separation of olivine relative to pyroxenes at low pressures and increased stability of subsilicic hydrous crystals and Fe-Ti oxides in the hydrous magmas account for changes in differentiation trends caused by Ptotal and PH2O variations. Lack of giant welded ash-flow sheets in the hydrous calc-alkaline series and common eruption of such ash flows from volcanic centers with rather anhydrous magmas led to the conclusion that H20/CO2 as well as total volatile content are critical controls on the likelihood of large scale, hot ash-flow eruptions. Giant, hot ash-flow sheets and associated calderas are favored in magmas with low H20/CO2 and high total volatile content. Basaltic and latitic volcanism in areas of thick sialic crust, where crystal fractionation is extensive are, therefore, the best sources of giant ash-flow sheets. H20/CO2 and total volatile content were also critical controls of the probability of hydrothermal ore deposition. Magmas with high H20/CO2 and moderate total volatile contents are most favored for ore deposition, because such magmas tend to form mesozonal or epizonal plutons rather than volcanic rocks. Plutonic crystallization of hydrous magma will yield a fluid phase capable of transferring incompatible metals and geothermal heat to ground water. If permeable structures and rocks are present, as in a caldera, widespread mineralization will be favored, but there may be no genetic relation between ore-forming magmas and magmas which produce calderas.
Download or read book Eruptive History and Geochemistry of the Little Walker Volcanic Center East Central California written by George R. Priest and published by . This book was released on 1974 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Geological Survey Circular written by and published by . This book was released on 1984 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Conterminous United States Mineral Appraisal Program written by and published by . This book was released on 1984 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Conterminous United States Mineral Appraisal Program written by Ticie A. Taylor and published by . This book was released on 1984 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ophiolites Arcs and Batholiths written by James Earl Wright and published by Geological Society of America. This book was released on 2008-01-01 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wright (geology, U. of Georgia) and Shervais (geology, Utah State U.) edit selections from a symposium titled "Ophiolites, Batholiths, and Regional Geology: A Session in Honor of Cliff Hopson" held at the Cordilleran Section Meeting of The Geological Society of America in 2005. With contributions from geologists and earth scientists from throughout the United States, the title contains separate sections for papers on the topics of ophiolites, arcs, and batholiths. The publication is illustrated in both black-and-white and color, but contains no index.
Download or read book Geothermal Systems of the Mono Basin Long Valley Region Eastern California and Western Nevada written by California. Division of Mines and Geology and published by . This book was released on 1985 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Concepts and Discoveries written by William M. Pennell and published by DEStech Publications, Inc. This book was released on 2015-06-12 with total page 719 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scientific analyses of the geology, metallogeny, and mineralization of gold, silver and other high-value elements in the western USATechnical details on working mines, exploration results, new depositsPresentations produced with the United States Geological Survey, Society of Economic GeologistsTwo-volume book set printed in full color with full-text searchable CD-ROM Produced under the auspices of the Geological Society of Nevada and published every five years, this two-volume book of peer-reviewed papers focuses on the geological analysis of ore-rich deposits in the western United States, especially ones containing gold and other high-value elements. Hundreds of stratigraphic, lithographic, remote-sensing and core sample examples are presented, particularly of areas likely to host Carlin-type gold deposits. The two volumes contain a wealth of data on specifically named mines, as well as technical information on high-potential areas for exploration. The book is profusely illustrated with full-color maps, photographs and charts for geology and mining engineering. A searchable CD accompanies the book and includes the full text of papers from the printed book, as well as abstracts and information from poster sessions not found in the printed book. Chapters in the text are fully refereed versions of presentations originally delivered at a symposium supported by the Geological Society of Nevada, along with the United States Geological Survey, Society of Economic Geologists and the Nevada Bureau of Mines. Sample key words: metallogeny, gold, epithermal ore, magmatism, Carlin trend, square array void mapping (SAVM), porphyry copper, tungsten, orogeny, lithogeochemistry, 3-D resistivity and modeling, fault-surface mapping, airborne electromagnetics and more. *The CD-ROM displays figures and illustrations in articles in full color along with a title screen and main menu screen. Each user can link to all papers from the Table of Contents and Author Index and also link to papers and front matter by using the global bookmarks which allow navigation of the entire CD-ROM from every article. Search features on the CD-ROM can be by full text including all key words, article title, author name, and session title. The CD-ROM has Autorun feature for Windows 2000 or higher products and can also be used with Macintosh computers. The CD includes the program for Adobe Acrobat Reader with Search 11.0. One year of technical support is included with your purchase of this product.
Download or read book Geology of the Central Sierra Nevada written by National Association of Geoscience Teachers. Far Western Section. Fall Field Conference and published by . This book was released on 2006 with total page 172 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 1981 with total page 1280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bulletin of the Geological Society of America written by Geological Society of America and published by . This book was released on 1976 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vols. 1-44 include Proceedings of the annual meeting, 1889-1933, later published separately.
Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1984 with total page 1016 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book California Geology written by and published by . This book was released on 1984 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book O S U Theses and Dissertations 1978 1982 written by Oregon State University and published by . This book was released on 1983 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petrogenesis of Late Tertiary Potassic Volcanic Rocks in the Sierra Nevada and Western Great Basin written by Gerald Frederick Brem and published by . This book was released on 1977 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transtensional Strains Tap Magmas from the Middle Crust and Low degree Melts in Crystal liquid Mush Zones written by Amalie Larsen-Van Vleet (Graduate student) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oregon Geology written by and published by . This book was released on 1985 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:
