Presentation Information
[R8P-12]Origin and Tectonic Evolution of Ultramafic Complex and Associated Lithologies along the Rakhabdev Lineament, Aravalli–Delhi Mobile Belt, India
*Drishti1, Anupam CHATTOPADHYAY2, Kaushik DAS1, Swarnaa ANNADURAI MUNUSAMY1, Junichi ANDO1, Sirshendu Kumar BISWAS1 (1. Hiroshima University, 2. University of Delhi)
Keywords:
Rakhabdev Lineament,Structural evolution,Antigorite serpentinite,Mineral chemistry and whole-rock geochemistry,Tectonic evolution
Orogenic belts commonly contain major structural discontinuities that preserve evidence of past tectonic processes. The Rakhabdev Lineament, located in the Archean-Paleoproterozoic Aravalli-Delhi Mobile Belt (ADMB), northwestern India, represents one such prominent structure. It marks the boundary between metamorphosed deep- and shallow-marine sedimentary successions and hosts discontinuous ultramafic bodies associated with metabasic and metasedimentary rocks. The protoliths of the ultramafic, metabasic, and metasedimentary rocks and the tectonic processes responsible for their present-day juxtaposition remain unconstrained. This study adopts an integrated approach to investigate the ultramafic rocks and the associated lithologies. Structural investigations identify three deformation phases recorded in the metasedimentary rocks during regional-scale deformation. The subparallel foliation (generally considered S2) of the serpentinite and metasedimentary rocks, together with the local occurrence of serpentinite as blocks within foliated metabasic rocks, indicates that these lithologies shared the dominant deformation phase (D2) and a close structural association, thereby constraining the relative timing of exhumation of these ultramafic rocks. Petrographic observations and preliminary spinel mineral chemistry suggest derivation of the serpentinite from a highly depleted peridotite protolith. Raman spectroscopy confirms the presence of antigorite. The associated metabasites record greenschist-facies metamorphism based on mineral assemblages and chlorite geothermometry. Whole-rock geochemical analyses of the metabasic rocks (Zr-TiO2-Nb-Y contents) suggest a subalkaline basalt to basaltic-andesite protolith. Whole-rock geochemical analyses of the metasedimentary rocks (La-Th-Sc-Zr-Co contents) suggest deposition in an active continental margin setting with provenance from a continental arc. The integrated structural, petrographic, and geochemical dataset provides a framework for evaluating the origin and tectonic evolution of the ultramafic bodies and the associated rocks along the Rakhabdev Lineament.