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Published October 1, 1971 | public
Journal Article

Rock-water systems, with special reference to the water-deficient region

Abstract

The four types of subsolidus assemblages in silicate-water systems are: Type I, water-absent; assemblage of anhydrous minerals with no vapor phase. Type II, water-deficient and vapor-absent; assemblage of minerals including hydrous minerals, but with no vapor phase. Type III, water-deficient and vapor-present; an assemblage of minerals, with or without hydrous minerals, with a vapor phase; there is insufficient water present to saturate the liquid when the crystalline assemblage is completely melted at the existing pressure. Type IV, water-excess; an assemblage of minerals and vapor with at least enough water to saturate the liquid when the crystalline assemblage is completely melted at the existing pressure. Water-deficient systems of types II and III are significant for magma generation and crystallization; there are few experimental results. Water-deficient phase relationships can be estimated by interpolation between available experimental data for systems of types I and IV. Mantle magmas are generated in type I, II, or III systems. The first liquid produced in type III systems is H_20-saturated, and the first liquid in type II systems is H_2O-undersaturated. It appears that the normal product of partial fusion of many continental crustal rocks is a H_2O-undersaturated granite liquid in a crystal mush, and that liquids of intermediate composition are not generated because temperatures required are too high. Phase relationships are depicted for granodiorite in a pressure-temperature- water diagram.

Additional Information

© 1971 American Journal of Science. We thank the National Science Foundation for Grant GA-10459 which has supported this research, Advanced Research Projects Agency Grant SD-89 to the Physical Sciences Division for a research assistantship for J. K. Robertson, many colleagues for discussion of the scheme developed, G. L. Millhollen for a critical review, and two anonymous reviewers whose comments led to this revised version with more explanation and justification of claims than the first manuscript submitted in August, 1970.

Additional details

Created:
August 23, 2023
Modified:
October 17, 2023