27 Rhyolite/Granite Magmatism II

Tuesday, 26 March 2019
1:30 PM - 5:45 PM
Konza Prairie Room

CHARACTERIZATION OF THE MARBLE CANYON AND CAVE PEAK GRANITOIDS IN TRANS-PECOS, TEXAS: INSIGHTS INTO THE PETROGENESIS OF HIGH-SILICA Y+REE-ENRICHED MAGMAS

Paper number: 27-8
Program: Theme Sessions
Time: 3:45 PM – 4:05 PM

Authors

Abstract

The Cave Peak intrusive complex in Trans-Pecos, Texas, hosts a molybdenum prospect that has been assigned to a class of high-grade, rift-related, fluorine-rich porphyries termed Climax-type Mo systems. Cave Peak exposures and exploration drilling define a hypabyssal rhyolitic core, surrounded by brecciated rhyolite and overprinted by hydrothermal alteration. The nearby Marble Canyon pluton consists of an unmineralized, compositionally zoned, monzodiorite to monzonite to quartz syenite intrusion that has been genetically linked to the Cave Peak rhyolite. These rocks show a within-plate geochemical affinity and represent a highly differentiated magma series. Rare earth element (REE) concentrations are even more elevated than other regional REE-prospects, with average REE+Y concentrations of 758 ppm (n=10) and 437 ppm (n=9) for Cave Peak and Marble Canyon, respectively. Quartz syenite and monzonite from the Marble Canyon Stock have zircon U-Pb ages of 36.2 ± 0.15 Ma and 36.1 ± 0.09 Ma, respectively, and an alkali feldspar granite porphyry at Cave Peak has a zircon U-Pb age of 34.8 ± 0.4 Ma. Petrogenetic modeling of early-formed Marble Canyon intrusive rocks and later-forming Cave Peak hypabyssal rhyolite provides insight into the nature of Y+REE-enriched high-silica magmatic systems.

Geological Society of America Abstracts with Programs. Vol. 51, No. 2

doi: 10.1130/abs/2019SC-327363

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