METASOMATIC VEINS AND MINERALS IN MANTLE-DERIVED XENOLITHS, ANTARCTICA
Late Cenozoic basanites of the McMurdo Volcanic Group, Antarctica, contain numerous ultramafic xenoliths derived from the upper mantle. The xenoliths show multiple-episodes of metasomatism resulting in formation of the veined metasomites and the equilibrated metasomites. The metasomatized xenoliths...
| Main Authors: | , |
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| Format: | Report |
| Language: | English |
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Department of Geology and Mineralogy, Faculty of Science, Hokkaido University
1988
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| Subjects: | |
| Online Access: | https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2563 http://id.nii.ac.jp/1291/00002563/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2563&item_no=1&attribute_id=18&file_no=1 |
| Summary: | Late Cenozoic basanites of the McMurdo Volcanic Group, Antarctica, contain numerous ultramafic xenoliths derived from the upper mantle. The xenoliths show multiple-episodes of metasomatism resulting in formation of the veined metasomites and the equilibrated metasomites. The metasomatized xenoliths are characterized texturally and chemically by co-existence of Ti-augite, phlogopitic mica, pargasitic and kaersutitic amphiboles, Al-spinel and apatite with the upper mantle olivine, pyroxenes, and Cr-spinel. Ti-, Al-, Fe- and Ca- enrichments and Si-, Cr- and Mg-depletions observed in the metasomatic clinopyroxenes indicate that the metasomatism was probably generated by an alkaline silicate melt reacting with solid phases of the upper mantle. Ti- and Fe-enrichments and Al-depletion in the metasomatic clinopyroxenes can be also detected as a separate episode of metasomatism different from the above veined-type reactions. Texturally and chemically equilibrated phlogopites and pargasites in the mantle-derived xenoliths provide a different type metasomatism, showing conspicuous depletions in TiO_2,Al_2O_3,Cr_2O_3,and K_2O, and enrichments in SiO_2 and Na_2O. |
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