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Rare earth element distributions among minerals in a granodiorite and their petrogenetic implications

Gromet, L. Peter and Silver, Leon T. (1983) Rare earth element distributions among minerals in a granodiorite and their petrogenetic implications. Geochimica et Cosmochimica Acta, 47 (5). pp. 925-939. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20131113-090618069

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Abstract

A study of the distribution of lanthanide rare earths in a granodiorite from the eastern Peninsular Ranges batholith, southern California, reveals that a large fraction of the REE in this rock resides in the accessory phases sphene and allanite. The minerals plagioclase, alkali feldspar, biotite, epidote and apatite each contribute approximately 1% or less of each REE to the whole rock, with the exception of Eu for which plagioclase contributes 7%. Sphene and allanite together contain 80% to 95% of each REE. Each of these phases is zoned in REE concentration with substantial decreases from core to margin. Textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma. REE zoning trends in sphene and allanite, and unexpectedly low REE concentrations in largely later crystallizing minerals such as feldspar, indicate that the precipitation of sphene and allanite significantly reduced REE concentrations in residual melts. These results illustrate the potential that sphene and allanite have for controlling the behavior of REE in granitic magmas. Available information collectively suggest that the sampled granodiorite existed as a complete melt, that the REE contained in the assemblage of phases were derived by direct crystallization from the melt, and that the melt behaved essentially as a closed system once crystallization of the phases now present began. Close correspondences between the major and trace element chemistries of the granodiorite and phenocryst-poor lavas from similar tectonic settings support these conclusions. The REE pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism. The high liquidus temperature of a granodiorite melt (~ 1000°C) indicates the importance of mantle-derived components within the sources of batholithic magmas in the Peninsular Ranges.


Item Type:Article
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http://www.sciencedirect.com/science/article/pii/0016703783901588PublisherArticle
Additional Information:© 1983 Pergamon Press Ltd. Received January 5, 1982; accepted in revised form February 3, 1983. This work represents a portion of the senior author’s doctoral dissertation done at the California Institute of Technology under NSF grants EAR74-00155 and EAR76-23150 and DOE grant EY-76-G-03-1305. The senior author acknowledges the National Science Foundation for providing financial support under a Graduate Traineeship and an Energy Related Graduate Fellowship. Preparation of this manuscript partially supported by NSF Grant EAR79-11184. We thank Bruce Chappell for making available an unpublished chemical analysis. Reviews of an early draft by P. Hess and M. Rutherford and journal reviews by M. Loiselle, C. Miller and R. Price are appreciated. Contribution 3719, Division of Geological and Planetary Sciences, California Institute of Technology.
Funders:
Funding AgencyGrant Number
NSFEAR 74-00155
NSFEAR 76-23150
Department of Energy (DOE)EY-76-G-03-1305
NSF Graduate TraineeshipUNSPECIFIED
NSFEAR 79-11184
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences3719
Issue or Number:5
Record Number:CaltechAUTHORS:20131113-090618069
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131113-090618069
Official Citation:L. Peter Gromet, Leon T. Silver, Rare earth element distributions among minerals in a granodiorite and their petrogenetic implications, Geochimica et Cosmochimica Acta, Volume 47, Issue 5, May 1983, Pages 925-939, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(83)90158-8. (http://www.sciencedirect.com/science/article/pii/0016703783901588)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42410
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Nov 2013 23:20
Last Modified:03 Oct 2019 05:58

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