Geology and Geochemistry of the 25 Ma Underdown Caldera Tuffs and the Tuff of Clipper Gap, Western Nevada Volcanic Field, North-Central Nevada
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The Underdown Caldera Complex is a 25.0 Ma caldera in the Western Nevada Volcanic Field formed during the mid-Cenozoic Ignimbrite Flare-up, one of the largest expressions of continental volcanism in geological time. Intracaldera and associated outflow tuffs are characteristically crystal-poor, except for one crystal-rich intracaldera tuff representing a later stage of explosive volcanism. Outflow tuffs extend to the east and west of the caldera, representing multiple phases of intracaldera tuffs. Post-deposition alteration of ignimbrites has altered Sr isotopic ratios, and caused rare earth element enrichment in the Tuff of Clipper Gap. Sr and Nd isotopic compositions of the ignimbrites show a relation to lavas collected from the margins of the caldera, and trace element ratios suggest similar origins of the lavas and ignimbrites from a mixture of mantle and crustal sources. Pb isotopes plot on mixing lines formed by a mantle-derived source and either a local sedimentary or granitoid unit.
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Copyright © 2020 the author(s). Theses may be used for non-commercial research, educational, or related academic purposes only. Such uses include personal study, research, scholarship, and teaching. Theses may only be shared by linking to Carleton University Institutional Repository and no part may be used without proper attribution to the author. No part may be used for commercial purposes directly or indirectly via a for-profit platform; no adaptation or derivative works are permitted without consent from the copyright owner.
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