Geochemistry of the ophiolite from Guanzizhen area, west Qinling, and its tectonic implications
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    Abstract:

    The ophiolite outcropped in Guanzizhen area, which marks the west part of the Shangdan suture zone in the Western Qinling, consists mainly of serpentites, meta-gabbros and meta-basalts. The meta-basalts are mostly characterized by high SiO2 and MgO contents, low TiO2, Al2O3 contents and Na2O>>K2O, as well as depleted in LREE and LILE. Additionally, the meta-basalts show that they are unfractionated in HFS elements in the primitive-normalized trace elements distribution patterns. All above signatures show that the magma source of the basalts from Guanzizhen is similar to that of a typical MORB. In detail, the meta-basalts can be divided into two A-type and B-type, which outcrop in the southern and northern of the section, respectively. The meta-basalts of B-type show lower TiO2, Al2O3, MgO and higher Σ Fe2O3 contents, and more depleted in LREE than that of the A-type meta-basalts. All above major and trace elements geochemistry suggest that both A and B types of the basalts are derived from a depleted mantle source, which are mostly like a middle ocean ridge setting, but were formed during different stages of the magma evolutionary process. In view of the regional geology and geochronology, it is preferred that these rocks were formed in a mid-ocean ridge setting during early Paleozoic. This ophiolite together with the other ophiolitic mélanges in Wushan, Tangzang and Yanwan areas mark the suture zone after the closure of the Qinling ocean in early Paleozoic.

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Dong Yunpeng.2008. Geochemistry of the ophiolite from Guanzizhen area, west Qinling, and its tectonic implications[J]. Acta Geologica Sinica,82(9):1186-1194

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History
  • Received:July 25,2008
  • Revised:July 25,2008
  • Adopted:July 28,2008
  • Online: September 17,2008
  • Published: