Hydrothermal alteration and geochemistry in core hole BC12-31: Implications for segregation of transient flow regimes in the Long Valley geothermal system

Andrew Fowler, Maya Wildgoose, Robert Zierenberg, Peter Schiffman, Gene Suemnicht

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations

Abstract

The results of fluid inclusion, intra-crystalline mineral, and stable isotope thermometric analyses suggest up to three periods of vein- and pore-filling mineralization: (1) shortly after eruption of the Bishop Tuff and deposition of the Megabreccia, when chlorite and possibly carbonate formed at temperatures in excess of 200°C; (2) after deposition of the Early Rhyolite, when quartz, carbonate, and some chlorite formed at temperatures closer to the present day boiling curve; and (3) most recently, at temperatures similar to present day measured downhole temperatures in BC 12-31. The microtextures of the Megabreccia, specifically the extremely low secondary porosity and fine-grained, chloritic matrix that appears to have formed shortly after the deposition of the Bishop Tuff, suggest that the Megabreccia might serve as an effective hydrologic barrier separating mixing of hotter fluids above and cooler fluids below. (Graph Presented).

Original languageEnglish (US)
Title of host publicationGeothermal Resources Council Annual Meeting 2011, Geothermal 2011
Pages785-789
Number of pages5
StatePublished - Dec 1 2011
EventGeothermal Resources Council Annual Meeting 2011, Geothermal 2011 - San Diego, CA, United States
Duration: Oct 23 2011Oct 26 2011

Publication series

NameTransactions - Geothermal Resources Council
Volume35 1
ISSN (Print)0193-5933

Other

OtherGeothermal Resources Council Annual Meeting 2011, Geothermal 2011
CountryUnited States
CitySan Diego, CA
Period10/23/1110/26/11

Keywords

  • Carbon isotopes
  • Chlorite geothermometry
  • Core BC 12-31
  • Fluid inclusions
  • Long Valley Caldera
  • Megabreccia
  • Oxygen isotopes

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