Geodynamic Significance of Cr-spinels from Ophiolite Mantle Peridotites of Northwestern Himalaya

Abstract

In this contribution the composition of Cr-spinels from Suru valley ophiolite peridotites is described and compared these with published data from Shergol serpentinized peridotites, both of these sequences occur as dismembered ophiolite blocks along the Indus suture zone (ISZ), Ladakh Himalaya and those from Manipur ophiolite belong to the eastern Himalaya. Back scattered electron images reveal that the Cr-spinel have overgrowth of magnetite, which is the dominant textural feature of the investigated rock types. However, in few peridotite samples, gradual replacement of Cr-spinel by ferrian-chromite along grain boundaries commonly occurs. Based on the spinel geochemistry, the Shergol peridotites are characterized by Cr-poor/Al-rich Cr-spinels whereas, the Suru valley peridotites by Cr-rich/Al-poor Cr-spinels. Shergol and Manipur ophiolite indicate their ocean floor affinity and the Suru valley peridotites depict supra subduction zone characteristics.