Journal of Petrology Advance Access originally published online on December 10, 2004
Journal of Petrology 2005 46(4):701-716; doi:10.1093/petrology/egh094
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Solubility of Anhydrite, CaSO4, in NaCl–H2O Solutions at High Pressures and Temperatures: Applications to Fluid–Rock Interaction
DEPARTMENT OF EARTH AND SPACE SCIENCES, UNIVERSITY OF CALIFORNIA LOS ANGELES, LOS ANGELES, CA 90095-1567, USA
Anhydrite solubility in H2O–NaCl solutions was measured at 6–14 kbar, 600–800°C and NaCl mole fractions (XNaCl) of 0–0·3 in piston–cylinder apparatus. Solubilities were determined by weight changes of natural anhydrite in perforated Pt envelopes confined with fluid in larger Pt capsules. In initially pure H2O at 10 kbar and 800°C, CaSO4 concentration is low (0·03 molal), though much larger than at the same temperature and 1 kbar. Hematite-buffered experiments showed slightly lower solubilities than unbuffered runs. CaSO4 solubility increases enormously with NaCl activity: at 800°C and 10 kbar and XNaCl of 0·3, CaSO4 molality is 200 times higher than with pure H2O. Whereas CaSO4 solubility in pure H2O decreases with rising T at low T and P, the high-P results show that anhydrite solubility increases with T at constant P at all XNaCl investigated. The effects of salinity and temperature are so great at 10 kbar that critical mixing between sulfate-rich hydrosaline melts and aqueous salt solutions is probable at 900°C at XNaCl 
0·3. Recent experimental evidence that volatile-laden magmas crystallizing in the deep crust may evolve concentrated salt solutions could, in light of the present work, have important implications regarding such diverse processes as Mount Pinatubo-type S-rich volcanism, high-f O2 regional metamorphism, and emplacement of porphyry Cu–Mo ore bodies, where anhydrite–hematite alteration and fluid inclusions reveal the action of very oxidized saline solutions rich in sulfur.
KEY WORDS: anhydrite; sulfur; solubility; metamorphic brines; granulites
* Corresponding author. Telephone: 1 310 206 3290. Fax: 1 310 825 2779. E-mail: manning{at}ess.ucla.edu
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  C. R. Stern, C. R. Stern, J. A. Funk, M. A. Skewes, and A. Arevalo MAGMATIC ANHYDRITE IN PLUTONIC ROCKS AT THE EL TENIENTE Cu-Mo DEPOSIT, CHILE, AND THE ROLE OF SULFUR- AND COPPER-RICH MAGMAS IN ITS FORMATION Economic Geology, November 1, 2007; 102(7): 1335 - 1344. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Skewes and C. R. Stern GEOLOGY, MINERALIZATION, ALTERATION, AND STRUCTURAL EVOLUTION OF THE EL TENIENTE PORPHYRY Cu-Mo DEPOSIT--A DISCUSSION Economic Geology, September 1, 2007; 102(6): 1165 - 1170. [Full Text] [PDF]
|
|
|
|
 |
|
 E. C. Hansen and D. E. Harlov Whole-rock, Phosphate, and Silicate Compositional Trends across an Amphibolite- to Granulite-facies Transition, Tamil Nadu, India J. Petrology, September 1, 2007; 48(9): 1641 - 1680. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. D. Webster and C. W. Mandeville Fluid Immiscibility in Volcanic Environments Reviews in Mineralogy and Geochemistry, July 1, 2007; 65(1): 313 - 362. [Full Text] [PDF]
|
|