Geology, geophysics and age of a late Miocene, intermediate-silicic, collapsed stratovolcano complex in the northern Mojave Desert, CA

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5127543

Sabin, A E ^[1]; Monastero, F C; Katzenstein, A M ^[2]; Snee, L W ^[3]

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1. Colorado School of Mines, Golden, CO (United States)
2. Geothermal Program Office, China Lake, CA (United States)
3. Geological Survey, Lakewood, CO (United States). Branch of Isotope Geochemistry

Geologic mapping has revealed that the Myrick Spring-Eagle Crags area of the northern Mojave Desert is an intermediate to silicic volcanic center covering nearly 100 square km. A complex series of flows, tuffs, dikes, sills and flow breccias ranging in composition from calc-alkaline basalt to high slica rhyolite were extruded through at least three different types of NW- to W-trending vents. Alteration associated with these vents includes silicic, propylitic, argillic and minor carbonate. The most intensely altered zones are vent-proximal and are controlled by a set of conjugate NW- and NE-trending fractures. Preliminary analyses reveal anomalously high concentrations of Hg, Sb and Ba with no detectable Au or Ag within these zones. Up to 500 m of vertical offset along an arcuate fault scarp in the central portion of this region describes the topographic rim of a half-graben style caldera with an infered diameter of at least 5 km. The outlow facies to the south of the rim is dominated by thick sequences of volcaniclastic breccias with interlayered rhyolite tuffs. Preliminary results of a detailed gravity survey have precisely delineated one of the largest gravity lows in the region ([minus]140 mgals). This low directly coincides with the topographic rim of the caldera. [sup 40]Ar/[sup 39] Ar age dating of biotite, sanidine and hornblende from dacite and rhyolite flows and tuffs preliminarily bracket the age of this volcanic center between 12.4 [+-].04 and 14.5 [+-].05 Ma.

• OSTI ID: 5127543
• 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

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALIFORNIA
CENOZOIC ERA
CHEMISTRY
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGY
GEOMORPHOLOGY
GEOPHYSICAL SURVEYS
GEOPHYSICS
GRAVITY SURVEYS
IGNEOUS ROCKS
ISOTOPE DATING
ISOTOPES
LIGHT NUCLEI
MAPPING
MIOCENE EPOCH
NORTH AMERICA
NUCLEI
RADIOISOTOPES
ROCKS
STABLE ISOTOPES
SURVEYS
TERTIARY PERIOD
TUFF
USA
VOLCANIC ROCKS
VOLCANISM
VOLCANOES
YEARS LIVING RADIOISOTOPES