Initial subduction of Neo-Tethyan ocean: Geochemical records in chromite and mineral inclusions in the Pozantı-Karsantı ophiolite, southern Turkey

Xia Liu, Ben Xun Su, Yan Xiao, Chen Chen, Ibrahim Uysal, Jie Jun Jing, Peng Fei Zhang, Yang Chu, Wei Lin, Patrick Asamoah Sakyi

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

Chromitites in the Pozantı-Karsantı ophiolite in Turkey mainly occur as podiform chromitites within mantle harzburgite and stratiform-like chromitites in mantle-crust transition zone. Chromites in chromitites have varing Cr# from 62.8 to 80.3 and can be divided into two types, namely; intermediate (Cr#: 62.8 – 69.2) and high-Cr (Cr#: 73.9 – 80.3) types. Major elements of the high-Cr chromitite have an affinity with boninite, whereas the intermediate chromitite shows transitional features between MORB and boninite. The compositional differences in clinopyroxene inclusions between intermediate- and high-Cr chromitite, coupled with the relatively high trace element contents (e.g. V, Ga) in the high-Cr chromitite, indicate distinctive parental magmas. Trace elemental profile analysis of a nodular chromite grain in one nodular chromitite sample PK14-41 demonstrates significant but non-systematic variations from the core to the rim, which also confirmed the compositional heterogeneity of the parental magmas. The presence of primary hydrous mineral inclusions such as amphibole in chromite, together with Ca-rich minerals (e.g. calcite), reflect the water-rich and Ca-rich characteristics of the parental magma. The higher fO2 of high-Cr chromitite evidenced by the lower V/Mn values may be due to more oxidized fluids released from downgoing crustal materials. Thus, we conclude that the parental magmas of the Pozantı-Karsantı chromitite were derived from a proto-forearc mantle and evolved to higher fO2 with the subduction initiation at that time, but were water- and Ca-rich in general.

Original languageEnglish
Article number102926
JournalOre Geology Reviews
Volume110
DOIs
Publication statusPublished - Jul 2019

Keywords

  • Chromite
  • Mineral inclusions
  • Parental magma
  • Subduction initiation
  • Trace elements

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