The ages, mineral assemblages, and chemical compositions show that these late Oligocene alkaline magmas formed after a shallowly subducting oceanic slab peeled away from the overlying continental lithosphere and rolled back. Hot asthenosphere flowed in to replace the subducting plate and caused partial melting of the variably metasomatized lithospheric mantle. These alkaline magmas include the shoshonite, mafic alkaline dikes, and minette of Boulter Peak; they mark the transition from older subduction-related magmatism to Miocene magmatism caused by lithospheric extension.

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.