Chapman, Alan D. and Saleeby, Jason B. and Eiler, John (2013) Slab flattening trigger for isotopic disturbance and magmatic flare-up in the southernmost Sierra Nevada batholith, California. Geology, 41 (9). pp. 1007-1010. ISSN 0091-7613. http://resolver.caltech.edu/CaltechAUTHORS:20130919-131453568
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The San Emigdio Schist of Southern California permits examination of partial melting and devolatilization processes along a Late Cretaceous shallow subduction zone. Detrital and recrystallized zircon of the structurally highest portions of the schist bracket the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower-plate schist and upper-plate assemblages of the Sierra Nevada batholith (SNB) reveal a δ^(18)O shift of ∼1.5‰ between igneous (∼5.5‰) and recrystallized (∼7‰) domains. These results, taken with previous zircon and whole-rock δ^(18)O measurements, provide evidence for devolatilization and/or partial melting of the schist and fluid ascent through overlying southwestern SNB upper-plate assemblages. Furthermore, the timing of mobile phase–rock interaction in the southwestern SNB is coincident with voluminous S-type magmatism in the southeastern SNB. We posit that during flattening of the Farallon slab, the schist was emplaced into the root zone of the southeastern SNB, where ensuing partial melting triggered a magmatic flare-up. Shallow subduction of the Cocos plate beneath central Mexico represents a close modern analog to this model.
|Additional Information:||© 2013 Geological Society of America. Manuscript received 4 February 2013; Revised manuscript received 7 May 2013; Manuscript accepted 8 May 2013. Published online 11 July 2013. This research was supported by National Science Foundation grant EAR-0739071 awarded to Saleeby. This is Caltech Tectonics Observatory contribution number 222. We thank Yunbin Guan for analytical assistance; Rita Economos, Sue Kay, Sarah Roeske, and Luigi Solari for insightful reviews; Rónadh Cox and Sandra Wyld for editorial handling; and Paul Asimow, Carl Jacobson, and Steven Kidder for discussions.|
|Group:||Caltech Tectonics Observatory|
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|Deposited By:||Tony Diaz|
|Deposited On:||19 Sep 2013 21:55|
|Last Modified:||19 Sep 2013 21:55|
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