Sagehen Creek Field Station

07 Jul, 07 PM - 22 Jul, 12 AM

Much of the Sierra Nevada of northern California and adjacent parts of western Nevada are blanketed by Late Tertiary volcanic rocks of which relatively little is known, because few published studies of these rocks exist. Remarkably, this poorly understood fragment of the western US magmatic mosaic lies in a tectonic setting that is transitional between subduction-related continental arc and Basin and Range-related extension [Henry, 2001], raising the possibility that magmatism may be controlled by processes distinct to both subduction and extensional regimes. The goals of this project are to better constrain the timing of Ancestral Cascades arc (ARC) volcanism through 40Ar/39Ar geochronology, evaluate the relationship between magmatism and tectonism, assess geographic and temporal variations in rock composition that may relate to changes in mantle sources, lithospheric interactions, and tectonic affinity (arc vs. extension vs. hotspot) with time, and to compare volcanism in northeasternern California with that of purely extension-related volcanism in the Western Great Basin of southeastern California. To date, our research has been a reconnaissance-scale Ar-Ar geochronologic, major element, trace element, and Pb-Sr-Nd isotopic investigation of ARC volcanic complexes in the Lake Tahoe region [Cousens et al., 2008]. However, our work to date has only skimmed the surface of the ARC. We lack volcanic centres with adequate geochronology to establish how mantle sources and/or petrogenetic processes varied as subduction progressed. The Sagehen/Independence Lake area includes an abundances of ARC volcanic rocks of varying composition (basalt to dacite) that appear to have been erupted over a short time span (1 Ma), making this a prime target for detailed studies of the processes that control the composition of the lavas. The area has been well-mapped by A. Sylvester and students at UC Santa Barbara, with whom we are collaborating. This represents our first in-depth study of volcanism in the Ancestral Cascades arc.

Visit #21021 @Sagehen Creek Field Station

Approved

Under Project # 21502 | Research

Geochemistry of Miocene-Pliocene volcanic rocks, Sagehen Creek and Independence Lake Area

faculty - Carleton College

Reservation Members(s)

Group of 2 Graduate Student Jul 7 - 22, 2010 (16 days)
Group of 2 Faculty Jul 7 - 22, 2010 (16 days)
Brian Cousens Jul 7 - 22, 2010 (16 days)

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