Neogene rhyolites of the northern Jemez volcanic field, New Mexico
| Autor: | Bruce M. Loeffler, W. Scott Baldridge, David T. Vaniman, Muhammed Shafiqullah |
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| Rok vydání: | 1988 |
| Předmět: |
Atmospheric Science
geography geography.geographical_feature_category Ecology Geochemistry Paleontology Soil Science Forestry Magma chamber Aquatic Science Oceanography Dacite Volcanic plug Volcanic rock Igneous rock Geophysics Space and Planetary Science Geochemistry and Petrology Pumice Rhyolite Earth and Planetary Sciences (miscellaneous) Caldera Geology Earth-Surface Processes Water Science and Technology |
| Zdroj: | Journal of Geophysical Research. 93:6157 |
| ISSN: | 0148-0227 |
| DOI: | 10.1029/jb093ib06p06157 |
| Popis: | Volcanic centers previously mapped as the 20 Ma El Rechuelos Rhyolite in the northern Jemez volcanic field, New Mexico, include three distinct episodes of rhyolitic volcanism. An early (7.5 Ma) extrusive dome of flow-banded biotite rhyolite and an intermediate (5.8 Ma) rhyolite, possibly a volcanic neck, correspond in age to rhyolites of the Keres Group in the southern Jemez volcanic field. Three other extrusive domes of aphyric, pumiceous rhyolite and obsidian comprise a late volcanic episode, dated at 2.0 Ma. We retain the name El Rechuelos Rhyolite only for these late centers. Another center, farther north than the others but previously mapped with the El Rechuelos Rhyolite, is a dacite pumice ring whose age (5.2 Ma), petrography, major- and trace-element chemistry, and Sr initial ratio all suggest it should be included with rocks of the Tschicoma Formation. Nd and Sr isotopic ratios of the Neogene rhyolites of the northern Jemez volcanic field suggest that these rhyolites were not produced by partial melting of either upper or lower crust. Rather, they may have been generated from a mantle-derived mafic magma, such as the nearby Lobato Basalt, by fractional crystallization with concomitant assimilation of small amounts ( |
| Databáze: | OpenAIRE |
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