Accessory mineral U-Th-Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

Justin I. Simon, Jorge A. Vazquez, Paul R. Renne, Axel K. Schmitt, Charles R. Bacon, Mary Reid

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤ 230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ∼85 ka rhyolites yielded ages between ∼100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ∼200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10's to 100's ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.

Original languageEnglish (US)
Pages (from-to)421-446
Number of pages26
JournalContributions to Mineralogy and Petrology
Volume158
Issue number4
DOIs
StatePublished - 2009

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Bearings (structural)
accessory mineral
accessories
chronology
Accessories
volcanic eruptions
magma
Minerals
volcanology
volcanic eruption
minerals
Pleistocene
zircon
granophyre
dating
allanite
Geothermal wells
rhyolite
Domes
domes

Keywords

  • Ar/Ardating
  • Coso volcanic field
  • Magmatime scales
  • Rhyolite
  • U-Th-Pbdating
  • Zirconand allanite

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Accessory mineral U-Th-Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California. / Simon, Justin I.; Vazquez, Jorge A.; Renne, Paul R.; Schmitt, Axel K.; Bacon, Charles R.; Reid, Mary.

In: Contributions to Mineralogy and Petrology, Vol. 158, No. 4, 2009, p. 421-446.

Research output: Contribution to journalArticle

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