Physical and chemical aspects of fluid evolution in hydrothermal ore systems

Miscellaneous · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6244349

Cline, J S

A one-dimensional, physical model describing two-phase fluid flow is used to simulate the effect of boiling on silica precipitation in geothermal and epithermal precious metal systems. The extent to which decreasing temperature and fluid vaporization are responsible for quartz precipitation is dependent on three related factors-the temperature of the fluid entering the two-phase system, the change in fluid temperature with respect to distance of fluid travel, and the extent of fluid vaporization in regions of gradual temperature decline. Boiling contributes to significant quartz precipitation in systems with high-temperature basal fluids, and in deeper portions of systems in which extensive vaporization occurs. Temperature reduction is a dominate precipitation mechanism in near-surface regions where temperature reduction is rapid, and in systems with lower temperature fluids. Quartz precipitation is most intense in systems with high mass flux/permeability ratios and low initial fluid temperatures. Geothermal systems with high mass flux/permeability and moderately low initial fluid temperatures are most effective in producing epithermal systems with abundant gold. Fluid evolution during the magnetic-hydrothermal transition and coincident molybdenite precipitation at Questa, New Mexico, has been traced using fluid inclusion microthermometry. The lack of cogenetic liquid- and vapor-rich inclusions, plus final homogenization of most saline, liquid-rich inclusions by halite dissolution indicate that high-salinity fluids were generated by a mechanism other than fluid immiscibility. Pressure flucuations are capable of producing the observed fluids and inclusion behavior. Solubility data indicate that the crystallizing aplite porphyry generated fluids with salinates as high as 57 wt.% NaCl equivalent.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)
• OSTI ID: 6244349
• Resource Relation: Other Information: Thesis (Ph.D)
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
GEOTHERMAL FLUIDS
ORIGIN
QUARTZ
PRECIPITATION
BOILING
COPPER ORES
EVAPORATION
GEOCHEMISTRY
GEOLOGIC MODELS
GOLD ORES
HYDROTHERMAL SYSTEMS
MATHEMATICAL MODELS
MOLYBDENUM ORES
NEW MEXICO
ONE-DIMENSIONAL CALCULATIONS
PERMEABILITY
PRESSURE GRADIENTS
RESERVOIR TEMPERATURE
SALINITY
SILICA
SOLUBILITY
TEMPERATURE DEPENDENCE
TEMPERATURE GRADIENTS
TWO-PHASE FLOW
CHALCOGENIDES
CHEMISTRY
DEVELOPED COUNTRIES
FEDERAL REGION VI
FLUID FLOW
FLUIDS
GEOTHERMAL SYSTEMS
MINERALS
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
USA
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions