Geology, geophysics and age of a late Miocene, intermediate-silicic, collapsed stratovolcano complex in the northern Mojave Desert, CA
- Colorado School of Mines, Golden, CO (United States)
- Geothermal Program Office, China Lake, CA (United States)
- 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-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structurally controlled volcanism and contrasting types of mineralization, Tuscarora mining district and vicinity, Nevada
Cenozoic volcanic geology and probable age of inception of basin-range faulting in the southeasternmost Chocolate Mountains, California
Related Subjects
CALIFORNIA
VOLCANOES
VOLCANIC ROCKS
GEOCHEMISTRY
ISOTOPE DATING
GEOLOGY
ARGON 39
ARGON 40
GEOMORPHOLOGY
GEOPHYSICS
GRAVITY SURVEYS
MAPPING
MIOCENE EPOCH
TUFF
VOLCANISM
AGE ESTIMATION
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CENOZOIC ERA
CHEMISTRY
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
GEOPHYSICAL SURVEYS
IGNEOUS ROCKS
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
RADIOISOTOPES
ROCKS
STABLE ISOTOPES
SURVEYS
TERTIARY PERIOD
USA
YEARS LIVING RADIOISOTOPES
580000* - Geosciences