Crystallization history of Obsidian Dome, Inyo Domes, California

Autor: John C. Eichelberger, Michael T. Naney, Henry R. Westrich, Samuel E. Swanson
Rok vydání: 1989
Předmět:
Zdroj: Bulletin of Volcanology. 51:161-176
ISSN: 1432-0819
0258-8900
DOI: 10.1007/bf01067953
Popis: Samples obtained by U.S. Department of Energy research drilling at the 600-year-old Obsidian Dome volcano provide the rare opportunity to examine the transition from volcanic (dome) to plutonic (intrusion) textures in a silicic magma system. Textures in the lavas from Obsidian Dome record multiple periods of crystallization initiated in response to changes in undercooling (ΔT) related to variable degassing in the mag-ma. Phenocr)ysts formed first at low ΔT. A drastic increase in ΔT, related to loss of a vapor phase during initial stages of eruption, caused nucleation of microlites. All of the lavas thus contain phenocrysts and microlites. Extrusion and subsequent devitrification of the dry (0.1 wt% H2O) magma crystallized spherulites and fine-grained rhyolite at high ΔT. A granophyric texture, representing crystallization at a moderate ΔT, formed in the intrusions beneath Obsidian Dome. Textures in the intrusion apparently represent crystallization of hydrous (1–2 wt% H2O) rhyolitic magma at shallow depths.
Databáze: OpenAIRE
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