CHARACTERIZATION AND PETROGENESIS OF ADAKITIC PYROCLASTIC ROCKS ERUPTED DURING THE HOLOCENE FROM
The variation of magma compositions at Shiveluch volcano, the northernmost and most active andesitic volcano on the Kamchatka Peninsula, was examined in Holocene eruptive products (8900 14 C year BP to 1964). Pumice clasts and tephra samples from 48 pyroclastic eruptions were analyzed by X-ray fluor...
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| Format: | Text |
| Language: | English |
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2002
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.211.498 http://www.ees.nmt.edu/outside/alumni/papers/2002i_hartman_m.pdf |
| Summary: | The variation of magma compositions at Shiveluch volcano, the northernmost and most active andesitic volcano on the Kamchatka Peninsula, was examined in Holocene eruptive products (8900 14 C year BP to 1964). Pumice clasts and tephra samples from 48 pyroclastic eruptions were analyzed by X-ray fluorescence and electron microprobe methods. Medium-K, hornblende-bearing andesite has been the dominant eruptive product from Shiveluch volcano. Four basaltic andesite and one dacite eruption have been recognized. Rhyolites are absent in the Holocene eruptive products. Analyses of single pumice from individual eruptive units show no evidence for chemical zonation suggesting the magma chambers were well mixed and uniform throughout. Bulk analyses of pumice show coherent geochemical trends consistent with either mixing and/or fractional crystallization. The Shiveluch andesites have high MgO (2.3-6.8 wt %), Cr (65-358 ppm), Ni (18-106 ppm) and Sr (471-615 ppm) and low Y (<18 ppm). They are geochemically similar to adakites, which are derived by partial melting of eclogite subducted oceanic crust. Slab melt is usually associated with subduction of young, relatively warm oceanic |
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