EVIDENCE FOR HYDROUS HIGH-MGO MELTS IN THE PRECAMBRIAN
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dc.contributor.author | Stone W.E. | |
dc.contributor.author | Larson M.S. | |
dc.contributor.author | Lesher Michael C. | |
dc.contributor.author | Deloule E. | |
dc.date.accessioned | 2020-12-13T04:29:22Z | |
dc.date.available | 2020-12-13T04:29:22Z | |
dc.date.issued | 1997 | |
dc.identifier | https://elibrary.ru/item.asp?id=31729139 | |
dc.identifier.citation | Geology, 1997, , 2, 143-146 | |
dc.identifier.issn | 0091-7613 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/20658 | |
dc.description.abstract | Prevailing petrogenetic models for Precambrian high-MgO melts such as komatiites invoke crystallization from nearly anhydrous melts (≪0.5% H2O) generated by partial melting of mantle peridotite at temperatures of (≤ 1900 °C and pressures of (18 GPa. However, ultramafic cumulate and gabbro zones of komatiitic and other high-MgO units in Precambrian greenstone belts contain vesicles and minor to major amounts (≤ 25%) of igneous amphibole. The textures (oikocrysts, rims on intercumulate pyroxene, and mineral inclusions within orthocumulate olivine) and the water-rich compositions (1.00% 2.50% H2O) of igneous amphiboles from the Archean Abitibi belt indicate crystallization in situ from significantly hydrous melts while the melt fraction was still as high as 40% 50%. Comparisons to experimental phase equilibria suggest that the residual melts from which the amphiboles crystallized contained 3% 4% H2O, and adjustments for fractional crystallization suggest that the initial melts may have contained as much as 2% H2O. H2O contents of this magnitude would require substantial revision of the nearly anhydrous models for Precambrian high-MgO melts, possibly permitting generation at lower temperatures and pressures, lowering their densities and viscosities, increasing their eruptibility, and enhancing the formation of spinifex textures. | |
dc.subject | Precambrian | en |
dc.title | EVIDENCE FOR HYDROUS HIGH-MGO MELTS IN THE PRECAMBRIAN | |
dc.type | Статья | |
dc.subject.age | Precambrian | en |
dc.subject.age | Докембрий | ru |
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