Evolution of Cretaceous granitoids in the western cordillera: An example from the Santa Rose Mountain Range, Nevada
- Miami Univ., Oxford, OH (United States)
The Santa Rosa Range is located in Humboldt County, Nevada. Two textural/compositional groups exist within the granitoid suite. The bulk of the granitoids, exposed in the main stock and a smaller flanking stock, belong to the Santa Rosa/Andorno (SR/A) group. These rocks are primarily met- to peraluminous, equigranular, hornblende-biotite granodiorite. These granitoids are enclave bearing and are cross cut by syn-plutonic rholite/dacite dikes and fine grained aplite dikes. The second group exposed in the Sawtooth (ST) and Granite Peak (GP) stocks, are primarily met- to peraluminous, equigranular to porphyritic biotite granite/granodiorite. The rocks of this group are also cut by fine grained aplite dikes. Petrographic and elemental analyses indicate a broad northward evolutionary trend with rocks of the GP stock being the most highly evolved of the suite. Major element variation diagrams show patterns of enrichment or depletion consistent with fractional crystallization. There is a change in the slope of these trends, however, at the SR/A and ST/GP transition indicating these two groups many not be petrogenetically linked. Sr vs SiO[sub 2] displays two distinct, overlapping, sub parallel trends of Sr depletion with increasing SiO[sub 2] again indicating the two granitoid groups are not related. Trace element characteristics suggest that it is not possible to derive the most evolved granitoid in the SR/A group from the least evolved sample available by fractional crystallization alone. Crustal contamination of the magma, or the mixing of an additional liquid(s), coupled with fractionation of both plagioclase and biotite are required to produce the trace element trends observed in the SR/A groups. In contrast, the GP/ST group has undergone K-feldspar fractionation.
- OSTI ID:
- 6137463
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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