Spinel chemistry and geochemistry of serpentinite of North Delhi fold belt, Rajasthan: Constraining the petrogenesis and geodynamics of northwestern Indian shield

Abstract

The western margin of the north Delhi fold belt, Rajasthan is mostly covered by the thick alluvium‐sand cover of the Thar Desert. However, a study on a cluster of scattered and deformed serpentinite bodies exposed in the small opencast quarries are presented here. Though alteration and absence of primary phases possess constraints over petrogenesis, but, the accessory, anhedral spinel chemistry aids in the genetic reconstruction. The unaltered core part of the spinel that is, the Al‐chromite (avg. 45.2 wt% Cr2O3), followed by ferrit chromite (avg. 32.3 wt% Cr2O3) inner rim and magnetite towards the outer rim is the character of spinels present in the host, where the chemistry of the core part is used exclusively. This core part of spinel preserves the primary mantle signature and attests the forearc peridotite character and a similar subduction‐related trait is followed by the whole‐rock major oxide proxies. Cumulative petrological, whole‐rock geochemistry, and mineral chemical signature unequivocally advocate towards a harzburgitic protolith, an arc peridotitic character, and presence of ancient forearc environment. The present communication is the first to describe the detailed characterization of serpentinite bodies with a possible linkage towards the presence of ancient oceanic slices in the north Delhi fold belt, Rajasthan, NW India.