ABSTRACT

The nature and geodynamic setting of Inner Makran ophiolites (SE Iran) are controversial and are the focus of a growing debate. The Fannuj-Maskutan ophiolite complex (central Inner Makran) is made up of lherzolites, harzburgites, layered and isotropic gabbros and diabase dikes and basaltic lavas. Here we present new textural description, mineral and whole-rock chemistry of peridotites together with bulk geochemistry of magmatic mafic rocks and U-Pb geochronology and Lu-Hf isotopes of inherited zircons in gabbros, with the aim to reconstruct the petrogenesis of the Fannuj-Maskutan ophiolite. The results indicate to a subduction-metasomatized depleted mantle source experienced 10–20% of partial melting. A transition from IAT-gabbros to E-MORB-basalts is also outlined. We interpret the obtained results as evidence for the Fannuj-Maskutan genesis in a supra-subduction zone (SSZ) basin developed in the Iranian cadomian crust as indicated by the presence of inherited Cadomian zircons (ca. 515 Ma, εHf_(t): −13.6 – +11.2). Comparing the Fannuj-Maskutan ophiolites to well-known SSZ-systems such as the South Sandwich SSZ, and integrating with the existing literature on Inner Makran ophiolite belt we interpret the Fannuj-Maskutan ophiolite as a part of a major SSZ-basin opened in the Iranian cadomian crust and evolved during the Neotethys subduction under Central Iran.

摘要

内马克兰蛇绿岩（伊朗东南部）的性质和地球动力学背景是有争议的，并且是越来越多争论的焦点。Fannuj-Maskutan蛇绿岩复合体（内马克兰中部）由锂铁矿，harzburgite，层状各向同性辉长岩，辉绿岩堤和玄武岩熔岩组成。在这里，我们介绍了新的质地描述，橄榄岩的矿物和全岩石化学，以及岩浆镁铁质岩石的整体地球化学以及长辉岩中继承锆石的U-Pb年代学和Lu-Hf同位素，目的是重建Fannuj- Maskutan蛇绿岩。结果表明，一个俯冲-变质化的耗尽地幔源经历了部分融化的10-20％。还概述了从IAT-辉长岩到E-MORB玄武岩的过渡。_（t）：-13.6 – +11.2）。将Fannuj-Maskutan蛇绿岩与著名的SSZ系统（例如South Sandwich SSZ）进行比较，并结合有关内Makran蛇绿岩带的现有文献，我们将Fannuj-Maskutan蛇绿岩解释为主要的SSZ盆地的一部分。伊朗中部地壳在伊朗中部新特提斯俯冲期间演化。