Rutile to Titanite Transformation in Eclogites and its Geochemical Consequences: An Example from the Sumdo Eclogite, Tibet
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This work was supported by the National Science Foundation of China (Grant Nos. 92055202), the Second Tibetan Plateau Scientific Expedition and Research (Grant No. 2019QZKK0702) and the China Geological Survey (Grant Nos. DD20221817 and DD20221630). We are grateful to the editor and reviewers for their comments, that greatly helped in the improvement of the manuscript.

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    Abstract:

    The formation of titanite coronae after rutile is common in retrograde high- to ultrahigh-pressure meta-mafic rocks, which provides a good opportunity to address the geochemical behavior of HFSE in crustal environments. In the Sumdo eclogite, titanite occurs either as a corona around rutile grains or as semi-continuous veins cross-cutting the major foliation, whereas rutile grains occur either as inclusions in garnet or omphacite or as a relict core surrounded by titanite. Textural relationships and trace elements characteristics of rutile and titanite with different occurrences indicate that both minerals preferentially incorporate Nb and Hf over Ta and Zr in aqueous fluid. Moreover, the breakdown of omphacite and epidote could release substantial amounts of aqueous fluids enriched in Ca, Si, Fe and REE, which would react with rutile to form titanite coronae and veins. During this process, water-insoluble elements, like HFSE and HREE, behave like mobile elements, but they do not migrate substantially out of the system, instead, tending to react in situ. This suggests that the aqueous fluids released during the retrograde metamorphic reactions in mafic rocks could not substantially transfer fluid-immobile elements into the overlying mantle wedge in subduction environments.

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ZHAO Linghao, ZENG Lingsen, GAO Li’e, HU Mingyue, SUN Dongyang, ZHANG Lifei.2023. Rutile to Titanite Transformation in Eclogites and its Geochemical Consequences: An Example from the Sumdo Eclogite, Tibet[J]. Acta Geologica Sinica(),97(1):122-133

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History
  • Received:September 21,2007
  • Revised:March 04,2022
  • Adopted:
  • Online: February 28,2023
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