Lewis, Madeline J. and Bucholz, Claire E. and Jagoutz, Oliver E. (2021) Evidence for polybaric fractional crystallization in a continental arc: Hidden Lakes mafic complex, Sierra Nevada batholith, California. Contributions to Mineralogy and Petrology, 176 (11). Art. No. 90. ISSN 0010-7999. doi:10.1007/s00410-021-01844-y. https://resolver.caltech.edu/CaltechAUTHORS:20211110-161345996
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Abstract
Although the voluminous granitoids that constitute the upper crust of the Sierra Nevada batholith (California) have been investigated in detail, comparatively few studies focus on the origin of mafic bodies at similar crustal levels. Here, we present field and petrographic observations, geochronology, and geochemistry of the Hidden Lakes mafic complex in the central-eastern Sierra Nevada batholith. Our results show that the complex comprises norites, gabbros, monzondiorites, and monzonites that record fractional crystallization of a hydrous (~ 3 wt% H₂O), non-primitive basalt within the upper crust (0.3 GPa) at c. 95–96 Ma. To quantitatively model the generation of the observed lithologies, we construct a two-stage polybaric crystallization model based on cumulate and melt-like bulk-rock compositions. In the first step, we model fractionation of a primitive, mantle-derived basalt at > 30 km depth, generating dominantly pyroxenite cumulates. The evolution of the derivative melt (67% of melt mass remaining) is then modeled to fractionate at 12 km depth to produce the observed lithologies within the Hidden Lakes mafic complex. Extension of this model to higher-silica melt compositions (> 65 wt% SiO₂) replicates observed granodiorite compositions in the batholith, suggesting that polybaric crystallization could be an important process for the generation of arc granitoid melts. The depth of differentiation in continental arcs is debated, as field observations indicate abundant lower crustal fractionation while experimental data suggest that high-pressure crystallization of hydrous basalts cannot produce the non-peraluminous granitoid compositions observed in continental arc batholiths. Our model supports polybaric differentiation as one potential mechanism to resolve this inconsistency.
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Additional Information: | © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021. Received: 14 January 2021; Accepted: 15 September 2021. We thank Joe Biasi, Allyson Trussel, and Ben Klein for their assistance in the field, and thank Chi Ma for help with microprobe analyses and Nathan Dalleska for ICPMS support. We are grateful to the UCSB Petrochronology lab and Arizona Laserchron Center for their assistance with zircon LA-ICPMS. The geochronology analyses were supported by Awards for Geochronology Student Research2 funding (via National Science Foundation Grant no. EAR-1322032) awarded to M.J.L. O.J. and C.E.B. were supourted in part by EAR-1322032. Reviews by Cin-Ty Lee and Saskia Erdmann, as well as comments from editor Othmar Müntener, have been very helpful for improving this manuscript and are greatly appreciated. | |||||||||
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Subject Keywords: | Mafic; Gabbro; Sierra Nevada batholith; Polybaric; Arc; Fractional crystallization | |||||||||
Issue or Number: | 11 | |||||||||
DOI: | 10.1007/s00410-021-01844-y | |||||||||
Record Number: | CaltechAUTHORS:20211110-161345996 | |||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20211110-161345996 | |||||||||
Official Citation: | Lewis, M.J., Bucholz, C.E. & Jagoutz, O.E. Evidence for polybaric fractional crystallization in a continental arc: Hidden Lakes mafic complex, Sierra Nevada batholith, California. Contrib Mineral Petrol 176, 90 (2021). https://doi.org/10.1007/s00410-021-01844-y | |||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
ID Code: | 111821 | |||||||||
Collection: | CaltechAUTHORS | |||||||||
Deposited By: | Tony Diaz | |||||||||
Deposited On: | 11 Nov 2021 19:03 | |||||||||
Last Modified: | 11 Nov 2021 19:03 |
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