Petrology and geochemistry of the Russian peak pluton, Klamath Mountains, northern California

Thesis/Dissertation · Thu Jan 01 00:00:00 EST 1987

OSTI ID:5478098

Cotkin, S J

The Jurassic Russian Peak pluton consists of an older peridotite-to-quartz diorite complex intruded by younger granodiorite. U-Pb ages of 159 Ma have been obtained for both units. The peridotite-to-quartz diorite complex consists principally of quartz diorite; however, cumulate ultramafic rocks occur where it is in contact with Ordovician serpentinite, and the following zonation from serpentinite to quartz diorite is present: peridotite, pyroxenite, hornblendite, eucrite, and diorite. In order to evaluate the petrogenesis of the pluton a combination of field, petrographic, microprobe, X-ray fluorescence, and instrumental neutron activation analysis, and Rb-Sr data have been collected. Major and trace element modeling indicates that quartz-rich quartz diorite formed by crystallization, quartz-poor quartz diorite by accumulation of crystals plus trapped liquid, and ultramafic rocks by assimilation of serpentinite. Granodiorite on the other hand can be modeled by crystallization alone, with the precipitation of plagioclase, amphibole, and biotite accounting for the major and minor element variations. REE modeling indicates that a garnet-clinopyroxene amphibolite is a plausible source. A variety of techniques have been used to decipher the conditions of crystallization in each unit, including a comparison of paragenesis with crystallization experiments, geological thermometry and barometry, and phase equilibria. Pressure of intrusion is considered to have been approximately 3 kbar. The peridotite-to-quartz diorite complex intruded at about 1000/sup 0/C and was completely crystalline at 790/sup 0/C. Granodiorite intruded at somewhat lower temperatures and was completely crystalline at about 700/sup 0/C. The oxygen fugacity for both units was slightly above QFM. At its solidus, granodiorite was saturated with H/sub 2/O, which may account for the pervasive deuteric alteration of this unit.

• Research Organization: Wisconsin Univ., Madison (USA)
• OSTI ID: 5478098
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC DEPOSITS
AGE ESTIMATION
GEOCHEMISTRY
PETROLOGY
ACTIVATION ANALYSIS
CRYSTALLIZATION
ELECTRON MICROPROBE ANALYSIS
GEOLOGIC HISTORY
GEOLOGIC MODELS
INTRUSION
ISOTOPE DATING
LEAD
MINERALOGY
MINERALS
NEUTRON REACTIONS
RESERVOIR PRESSURE
RUBIDIUM
STRONTIUM
URANIUM
X-RAY FLUORESCENCE ANALYSIS
ACTINIDES
ALKALI METALS
ALKALINE EARTH METALS
BARYON REACTIONS
CHEMICAL ANALYSIS
CHEMISTRY
ELEMENTS
FEDERAL REGION IX
GEOLOGY
HADRON REACTIONS
METALS
MICROANALYSIS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
NUCLEAR REACTIONS
NUCLEON REACTIONS
PHASE TRANSFORMATIONS
USA
X-RAY EMISSION ANALYSIS
580100* - Geology & Hydrology- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)