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Title: Changes in magma storage conditions following caldera collapse at Okataina Volcanic Center, New Zealand

Large silicic volcanic centers produce both small rhyolitic eruptions and catastrophic caldera-forming eruptions. Although changes in trace element and isotopic compositions within eruptions following caldera collapse have been observed at rhyolitic volcanic centers such as Yellowstone and Long Valley, much still remains unknown about the ways in which magma reservoirs are affected by caldera collapse. We present 238U– 230Th age, trace element, and Hf isotopic data from individual zircon crystals from four eruptions from the Okataina Volcanic Center, Taupo Volcanic Zone, New Zealand, in order to assess changes in trace element and isotopic composition of the reservoir following the 45-ka caldera-forming Rotoiti eruption. Our data indicate that (1) mixing of magmas derived from crustal melts and mantle melts takes place within the shallow reservoir; (2) while the basic processes of melt generation likely did not change significantly between pre- and post-caldera rhyolites, post-caldera zircons show increased trace element and isotopic heterogeneity that suggests a decrease in the degree of interconnectedness of the liquid within the reservoir following collapse; and (3) post-caldera eruptions from different vents indicate different storage times of the amalgamated melt prior to eruption. Furthermore, these data further suggest that the timescales needed to generate large volumes ofmore » eruptible melt may depend on the timescales needed to increase interconnectedness and achieve widespread homogenization throughout the reservoir.« less
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Univ. of California, Davis, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Michigan Technological Univ., Houghton, MI (United States)
  4. Michigan State Univ., East Lansing, MI (United States)
  5. Univ. of Canterbury, Christchurch (New Zealand)
Publication Date:
Report Number(s):
LLNL-JRNL-700958
Journal ID: ISSN 0010-7999
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Contributions to Mineralogy and Petrology
Additional Journal Information:
Journal Volume: 171; Journal Issue: 1; Journal ID: ISSN 0010-7999
Publisher:
Springer
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Rhyolite; Taupo volcanic zone; Hf isotope; zircon; 230Th–238U
OSTI Identifier:
1335788