Geochemical Evolution at White Island, New Zealand
White Island, New Zealand, is an active andesitic volcano that is located near the southern end of the Tonga-Kermadec Volcanic Arc at the convergent plate boundary where the Pacific Plate is being subducted beneath the Indian-Australian Plate. The plate tectonic setting, volcanic features and the pe...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1998
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.521.9773 http://scholar.lib.vt.edu/theses/available/etd-61098-171720/unrestricted/mhr1.pdf |
| Summary: | White Island, New Zealand, is an active andesitic volcano that is located near the southern end of the Tonga-Kermadec Volcanic Arc at the convergent plate boundary where the Pacific Plate is being subducted beneath the Indian-Australian Plate. The plate tectonic setting, volcanic features and the petrology of White Island are thought to be characteristic of the environment associated with formation of porphyry copper deposits. White Island has only been active for about 10 Ka and, as such, is thought to be an ideal location to study early magmatic processes associated with formation of porphyry copper deposits. In this study, the geochemistry of the silicate melt at White Island has been characterized through detailed studies of silicate melt inclusions, phenocrysts, and matrix glass contained in recent ejecta (1977-1991). Most melt inclusions contained only glass, however, daughter minerals present in multiphase melt inclusions in the 1991 sample indicate a different P-T history compared to the other samples. Samples studied are vesicular porphyritic andesitic dacites containing phenocrysts of plagioclase, orthopyroxene, and clinopyroxene. A glassy matrix containing crystallites surrounds the phenocrysts. Both mineral and silicate melt inclusions occur in all three phenocryst phases. Inclusions of plagioclase occur in pyroxenes and inclusions of orthopyroxene and clinopyroxene |
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