Mingled mafic and felsic magmas in the Jurassic Eagle Mountain pluton, southeastern California
Conference
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· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5021590
- Univ. of Southern California, Los Angeles, CA (United States). Dept. of Geological Sciences
- Geological Survey, Menlo Park, CA (United States)
The metalluminous, compositionally expanded Eagle Mountain pluton ([approx] 165 Ma) was epizonally emplaced within Proterozoic metaigneous and Proterozoic-Paleozoic metasedimentary rocks in the Eagle Mountains of southeastern California. The evolution of the pluton involved mingling and partial mixing between mafic and felsic magmas. Heterogeneous rocks consisting of discrete biotite-clinopyroxene microdioritic enclaves (49--54% SiO[sub 2]) enclosed in hornblende-biotite granodiorite (57--61% SiO[sub 2]) grade into complexly mingled microdiorite and granodiorite as the proportion of microdiorite increases. The dioritic enclaves are notably potassic (2.1 [+-] .2 wt. %), containing abundant biotite (up to 23%) and interstitial patches of K-feldspar. These features are attributed to selective potassium enrichment of dioritic magma by diffusion during mingling with host granodioritic magma. A similar phenomenon was observed in experiments by Johnston and Wyllie, and attributed to relatively rapid diffusion of potassium from felsic to mafic magma. Calculated Sr[sub i] for the enclaves, intermediate dioritoids, and three of four analyzed host rocks cluster at 0.7085 [+-] 0.0002. Several homogeneous monzogranites not associated with enclaves have slightly higher Sr[sub i] (up to 0.7094) and define two separate mixing/AFC arrays on a plot of Sr[sub i] vs. 1/Sr, both anchored at the cluster of less radiogenic rocks. Alternatively, relatively rapid self-diffusion of Sr may have contributed to isotopic homogeneity during mingling of magmas from isotopically distinct sources.
- OSTI ID:
- 5021590
- Report Number(s):
- CONF-9305259--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
- Country of Publication:
- United States
- Language:
- English
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Conference
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Sun Feb 28 23:00:00 EST 1993
· Geological Society of America, Abstracts with Programs; (United States)
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OSTI ID:5879458
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Conference
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Wed Mar 31 23:00:00 EST 1993
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:5022700
Isotopic disequilibrium among commingled hybrid magmas: Evidence for a two-stage magma mixing-commingling process in the Mt. Perkins Pluton, Arizona
Journal Article
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Fri Sep 01 00:00:00 EDT 1995
· Journal of Geology
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OSTI ID:245397