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Open Access Publications from the University of California

High temperature metamorphism in the conductive boundary layer adjacent to a rhyolite intrusion in the Krafla geothermal system, Iceland

  • Author(s): Schiffman, P
  • Zierenberg, RA
  • Mortensen, AK
  • Frioleifsson, GO
  • Elders, WA
  • et al.

A rhyolite magma body within the Krafla geothermal system that was encountered at a depth of 2.1km during drilling of the IDDP-1 borehole is producing high temperature metamorphism within a conductive boundary layer (CBL) in adjacent host rocks. Cuttings recovered during drilling within a few meters of the intrusive contact in IDDP-1 are mainly comprised of granoblastic hornfelses, the rock type which confirms the presence of the CBL at the base of the IDDP-1 bore hole. The two pyroxenes in these hornfelses record temperatures that are in the range of 800-950°C. The minimum heat flow across the CBL is 23Wm-2. Country rocks at distances beyond 30m of the intrusive contact are essentially unaltered, implying that they have been emplaced very recently and/or as yet unaffected by hydrothermal fluid flow. © 2012 Elsevier Ltd.

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