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Liquid segregation parameters from amphibolite dehydration melting experiments

Wolf, Michael B. and Wyllie, Peter J. (1995) Liquid segregation parameters from amphibolite dehydration melting experiments. Journal of Geophysical Research B, 100 (B8). pp. 15611-15621. ISSN 0148-0227. doi:10.1029/95JB00660.

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We have experimentally obtained some of the parameters necessary for understanding the segregation of silicate liquid from amphibolite undergoing dehydration melting at 1 GPa and 750–1000°C. The solidus for this calcic amphibolite (68% Mg-Hb, 32% Pl (An_(90))) is <750°C. Amphibolites begin to melt at relatively high temperatures in the garnet-absent field, but the solidus appears to backbend at ∼1 GPa, coincident with the garnet-in boundary. Hornblende breakdown due to garnet formation releases H_2O and causes melting. Thus, in the garnet-present field (≥1 GPa), the amphibolite dehydration melting solidus may be coincident with the H_2O-saturated solidus. Liquid interconnectivity may be achieved at <900°C and <5 vol % liquid, based on both physical and chemical data from solid rock runs. Mass balance calculations from powdered rock runs suggest that small amounts (∼5–15 vol %) of hydrous (≥4 wt % H_2O), low-viscosity (10^3–10^4 Pa s), heavy rare earth element-depleted, felsic liquid may be segregated during amphibolite dehydration melting at ≥875°C. The rapid breakdown of coarse-grained Hb cores may lead to the formation of transient H_2O-saturated liquids with even lower viscosities (∼10^2 Pa s). Although comprising only a small portion of the melting cycle, these H_2O-rich conditions may enhance the segregation of liquid by reduction of liquid viscosities and by mechanical effects on the restite (e.g., increased deformation and liquid fracturing). During anatexis of coarse-grained (natural) rocks, transient conditions may control the initial stages of liquid segregation.

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Additional Information:Copyright 1995 by the American Geophysical Union. (Received July 15, 1994; revised January 13, 1995; accepted February 24, 1995.) Paper number 95JB00660. This research was supported by the Earth Science section of NSF, grant EAR 89-04375. We thank A. Patiño Douce, D. Laporte, and T. Rushmer for their thoughtful reviews.
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NSFEAR 89-04375
Issue or Number:B8
Record Number:CaltechAUTHORS:20141105-134311354
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Official Citation:Wolf, M. B., and P. J. Wyllie (1995), Liquid segregation parameters from amphibolite dehydration melting experiments, J. Geophys. Res., 100(B8), 15611–15621, doi:10.1029/95JB00660.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51322
Deposited By: George Porter
Deposited On:05 Nov 2014 22:13
Last Modified:10 Nov 2021 19:09

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