AN EXPERIMENTAL STUDY OF GRAIN SCALE MELT SEGREGATION MECHANISMS IN TWO COMMON CRUSTAL ROCK TYPES
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dc.contributor.author | Holyoke C.W. | |
dc.contributor.author | Rushmer T. | |
dc.date.accessioned | 2021-04-20T02:36:37Z | |
dc.date.available | 2021-04-20T02:36:37Z | |
dc.date.issued | 2002 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=1211695 | |
dc.identifier.citation | Journal of Metamorphic Geology, 2002, 20, 5, 493-512 | |
dc.identifier.issn | 0263-4929 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/28180 | |
dc.description.abstract | Creation of pathways for melt to migrate from its source is the necessary first step for transport of magma to the upper crust. To test the role of different dehydration-melting reactions in the development of permeability during partial melting and deformation in the crust, we experimentally deformed two common crustal rock types. A muscovite-biotite metapelite and a biotite gneiss were deformed at conditions below, at and above their fluid-absent solidus. For the metapelite, temperatures ranged between 650 and 800 °C at P c =700 MPa to investigate the muscovite-dehydration melting reaction. For the biotite gneiss, temperatures ranged between 850 and 950 °C at P c =1000 MPa to explore biotite dehydration-melting under lower crustal conditions. Deformation for both sets of experiments was performed at the same strain rate (ε.) 1.37×10-5 s-1. In the presence of deformation, the positive ΔV and associated high dilational strain of the muscovite dehydration-melting reaction produces an increase in melt pore pressure with partial melting of the metapelite. In contrast, the biotite dehydration-melting reaction is not associated with a large dilational strain and during deformation and partial melting of the biotite gneiss melt pore pressure builds more gradually. Due to the different rates in pore pressure increase, melt-enhanced deformation microstructures reflect the different dehydration melting reactions themselves. Permeability development in the two rocks differs because grain boundaries control melt distribution to a greater extent in the gneiss. Muscovite-dehydration melting may develop melt pathways at low melt fractions due to a larger volume of melt, in comparison with biotite-dehydration melting, generated at the solidus. This may be a viable physical mechanism in which rapid melt segregation from a metapelitic source rock can occur. Alternatively, the results from the gneiss experiments suggest continual draining of biotite-derived magma from the lower crust with melt migration paths controlled by structural anisotropies in the protolith. | |
dc.subject | DEHYDRATION-MELTING | |
dc.subject | DILATIONAL STRAIN | |
dc.subject | EXPERIMENTAL ROCK DEFORMATION | |
dc.subject | MELT DISTRIBUTION | |
dc.subject | MELT SEGREGATION | |
dc.title | AN EXPERIMENTAL STUDY OF GRAIN SCALE MELT SEGREGATION MECHANISMS IN TWO COMMON CRUSTAL ROCK TYPES | |
dc.type | Статья |
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