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Melting Interval of Peridotite with 5.7 per Cent Water to 30 Kilobars

Millhollen, G. L. and Irving, A. J. and Wyllie, P. J. (1974) Melting Interval of Peridotite with 5.7 per Cent Water to 30 Kilobars. Journal of Geology, 82 (5). pp. 575-587. ISSN 0022-1376. doi:10.1086/628007.

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Crystalline pargasite-rich spinel peridotite mylonite from St. Paul's Rocks containing 5.7% water bound in hydrous minerals was reacted in sealed platinum capsules in a piston-cylinder apparatus from 10 - 30 kb. At 10 kb the subsolidus assemblage is amphibole, olivine, orthopyroxene, clinopyroxene and spinel, an amphibole lherzolite; with increasing pressure garnet appears at 18 kb, spinel and amphibole disappear at about 25 kb; the resulting high pressure assemblage is that of a garnet lherzolite. The solidus was located in the presence of water-rich vapor, but vapor dissolves completely in the liquid at higher temperatures, and the liquid becomes water-undersaturated. Stability limits in the melting interval were determined for amphibole, garnet, spinel, clinopyroxene, orthopyroxene, and olivine (the liquidus mineral). The results are consistent with a published conclusion that St. Paul's Rocks is a diapiric, solid-state mantle intrusion initially mobilized at a depth between 45 km and 70 km near 1,000 - 1,050°C. An estimate of the solidus of peridotite with 0.2% water is presented and compared with other studies. At intermediate pressures this solidus is determined by the breakdown of amphibole. Discrepancies among results of the various studies probably arise at least in part from experimental problems involved in the complex systems.

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Additional Information:© 1974 University of Chicago Press. Manuscript received September 13, 1974; revised January 8, 1974. Research supported by the Earth Sciences Section, National Science Foundation, NSF Grant GA-32266X. We would like to acknowledge also the general support of the Materials Research Laboratory by the National Science Foundation. We thank W.G. Melson and G. Thompson for providing the analyzed rock sample, and R.B. Merrill and J.K. Robertson for experimental advice and assistance.
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Issue or Number:5
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Official Citation:G. L. Millhollen , A. J. Irving , and P. J. Wyllie . "Melting Interval of Peridotite with 5.7 per Cent Water to 30 Kilobars." The Journal of Geology 1974; 82(5), 575-587. DOI: 10.1086/628007
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64427
Deposited By: Tony Diaz
Deposited On:19 Feb 2016 22:23
Last Modified:10 Nov 2021 23:30

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