Association of petroleum and cinnabar in mercury deposits of the California Coast ranges, USA
Many mercury deposits around the world contain small but significant amounts of petroleum in association with cinnabar. Geological and geochemical investigations of mercury deposits in the northern California Coast ranges (Mayacmas, Wilbur Springs, Knoxville, and New Almaden districts) were undertaken to document the association, determine petroleum chemical compositions, and establish the geochemical setting of such deposits in order to formulate a genetic model. Petroleum +/- cinnabar occurs in veins, vugs, between breccia fragments, between quartz or carbonate crystals, in fluid inclusions or in froth veins. The occurrence of petroleum and cinnabar along the hanging walls of permeable structures attests to the relative buoyancy of oil and Hg during the transport process. GC-MS analysis of petroleums reveals the dominance of polycyclic aromatic hydrocarbons such as phenanthrenes, chrysenes, and naphthalenes. Neutron activation analysis of 6 petroleums yields maximum trace element concentrations of 20 ppm Hg, 330 ppb Au, 2.2 ppm As, 160 ppb Ag, 39 ppm Cr, 2.3 ppb Co, and 1.5 ppm Se. Silica-carbonate rock, an alteration product of serpentinite, is commonly the ore host. Geochemical modelling indicates that this alteration can arise from interaction with a CO{sub 2}-rich, H{sub 2}O-CO{sub 2} fluid. In addition to CO{sub 2}, the only components added to the system during alteration and mineralization were petroleum, H{sub 2}S, and Hg. The presence of free CO{sub 2} in sedimentary rocks allows the concentration of mercury in the gas phase and mobilization of petroleum. When the fluid is focussed by large scale anticlinal structures, it has the potential to form a cinnabar-(petroleum) deposit as it approaches the surface.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 5891054
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALIFORNIA
GEOLOGIC DEPOSITS
CINNABAR
ORIGIN
GEOCHEMISTRY
PETROLEUM
STRUCTURAL CHEMICAL ANALYSIS
ARSENIC
CARBON DIOXIDE
CARBONATE ROCKS
CHEMICAL COMPOSITION
CHROMIUM
COBALT
CORRELATIONS
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL TRANSPORT
GAS CHROMATOGRAPHY
GEOLOGIC MODELS
GOLD
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYSTEMS
ISOTOPE RATIO
MASS SPECTROSCOPY
MERCURY
MINERALIZATION
NEUTRON ACTIVATION ANALYSIS
PERMEABILITY
PETROLEUM DEPOSITS
POLYCYCLIC AROMATIC HYDROCARBONS
RESERVOIR FLUIDS
SELENIUM
SILICATES
SILVER
SOURCE ROCKS
SULFUR
TRACE AMOUNTS
ACTIVATION ANALYSIS
AROMATICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
CHROMATOGRAPHY
ELEMENTS
ENERGY SOURCES
ENERGY SYSTEMS
FEDERAL REGION IX
FLUIDS
FOSSIL FUELS
FUELS
GEOTHERMAL SYSTEMS
HYDROCARBONS
MASS TRANSFER
MERCURY COMPOUNDS
MERCURY SULFIDES
METALS
MINERAL RESOURCES
MINERALS
NONMETALS
NORTH AMERICA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SEMIMETALS
SEPARATION PROCESSES
SILICON COMPOUNDS
SPECTROSCOPY
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENTS
USA
020200* - Petroleum- Reserves
Geology
& Exploration
023000 - Petroleum- Properties & Composition