Fluid-melt interactions involving Cl-rich granites: Experimental study from 2 to 8 kbar

Journal Article · Sat Feb 01 00:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90088-Z· OSTI ID:5319783

Webster, J D ^[1]

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1. 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), Vol. 56:2; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CHLORINE
ACTIVATION ENERGY
GEOTHERMAL FLUIDS
CHEMICAL COMPOSITION
THERMODYNAMIC PROPERTIES
GRANITES
HYDROTHERMAL ALTERATION
PETROCHEMISTRY
CHLORINE COMPOUNDS
INCLUSIONS
MINERALIZATION
ORES
PRESSURE EFFECTS
TEMPERATURE EFFECTS
ELEMENTS
ENERGY
FLUIDS
HALOGEN COMPOUNDS
HALOGENS
IGNEOUS ROCKS
NONMETALS
PHYSICAL PROPERTIES
PLUTONIC ROCKS
ROCKS
580000* - Geosciences