Chapter 3 Melt Inclusion Study of the Embryonic Porphyry Copper System at White Island, New Zealand
White Island, New Zealand, is an active andesitic-dacitic volcano that is located near the southern end of the Tonga-Kermadec-Taupo Volcanic Arc at the convergent plate boundary where the Pacific plate is being subducted beneath the Indian-Australian plate. The plate tectonic setting, volcanic featu...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.542.7969 http://www.geochem.geos.vt.edu/fluids/pdf/2003, Rapien et al,EconGeol.pdf |
| Summary: | White Island, New Zealand, is an active andesitic-dacitic volcano that is located near the southern end of the Tonga-Kermadec-Taupo 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 petrology of White Island are characteristic of the environment associated with formation of porphyry copper deposits. White Island has been active for at least 10 ka and, as such, is an ideal location to study early magmatic processes associated with formation of porphyry copper deposits. In this study, the geo-chemistry of the magma chamber at White Island has been characterized through analyses of silicate melt inclusions, phenocrysts, and matrix glass contained in recent ejecta (1977–1991). Most melt inclusions in samples from the 1977, 1988, and 1989 eruptions contained only glass and occasional vapor bubbles and/or trapped solids. The 1991 sample contained daughter minerals, suggesting a different P-T history compared to the other samples. Data obtained from White Island are compared to various major, trace element, and volatile composi-tion trends reported for both economic and noneconomic (or barren) porphyry deposits. Magmas asso-ciated with economic porphyry copper deposits are generally peraluminous with Al2O3/(Na2O + K2O + CaO) ratios greater than or equal to 1.3, and compositions of melt inclusions from White Island equal |
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