Fluid-melt interactions involving Cl-rich granites: Experimental study from 2 to 8 kbar
- American Museum of Natural History, New York, NY (United States)
Experiments have been conducted in the system Na{sub 2}O-K{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O-Cl{sub 2}O{sub {minus}1} at 2, 4 kbar (800 and 1,000C) and 6, 8 kbar (800C) to determine thermodynamic constraints on fluid-melt interaction and to determine the effects of pressure (P) and temperature (T) on Cl partitioning between aqueous fluid and subaluminous and peralkaline haplogranite melts. The Cl concentration of the run product glasses was determined by electron microprobe, and the H{sub 2}O concentration of some glasses was determined by ion microprobe. The Cl concentration of the aqueous fluid was computed by mass balance and was also analyzed by chloridometer for several runs; agreement between the two methods is within {plus minus}9 relative %. D{sub Cl} increases strongly with increasing P for P < 6 kbar, increasing concentrations of Cl in the system, and decreasing T. The experimental results indicate that the concentration of Cl in granitic melts may reach a maximum limiting value as Cl-rich magmas crystallize. Granitic systems exhibiting a maximum concentration of Cl in the melt must either contain crystalline alkali chlorides, molten alkali chlorides, or coexisting liquid plus vapor or the melt must contain the solubility limit for Cl. The experimental data suggest that at 2 kbar and 800C a single, supercritical fluid is stable, if the fluid contains {le} 67 wt% NaCl and KCl. Conversely, at 2 kbar and 1,000C two immiscible phases coexist with haplogranite melt if the combined liquid and vapor contain from approximately 10 to 55 wt% NaCl and KCl. Application of experimental data to Cl-rich and F-poor, mineralizing granitic systems suggests that Cl will be most strongly enriched in ore fluids at relatively low temperature (between 800 and 1,000C) and relatively high pressure (for P < 6 kbar).
- OSTI ID:
- 5319783
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:2; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ACTIVATION ENERGY
CHEMICAL COMPOSITION
CHLORINE
CHLORINE COMPOUNDS
ELEMENTS
ENERGY
FLUIDS
GEOTHERMAL FLUIDS
GRANITES
HALOGEN COMPOUNDS
HALOGENS
HYDROTHERMAL ALTERATION
IGNEOUS ROCKS
INCLUSIONS
MINERALIZATION
NONMETALS
ORES
PETROCHEMISTRY
PHYSICAL PROPERTIES
PLUTONIC ROCKS
PRESSURE EFFECTS
ROCKS
TEMPERATURE EFFECTS
THERMODYNAMIC PROPERTIES