Proterozoic arc magmatism from the Padhar mafic-ultramafics in Betul Belt, Central India Tectonic Zone: Insight from petrography, bulk rock and in-situ trace element geochemistry

• Geological, petrological, and geochemical data of the Padhar complex. • This complex exhibit features similar to Alaskan-type mafic-ultramafic intrusions. • The parent melt originates from a mantle source modified by slab-derived fluids. • The Padhar complex reveals a shallow level of a Meso-Neoproterozoic Island arc. • The ultramafic rocks are arc magma conduits in the Betul Belt of the CITZ. This study presents the first identification of an Alaskan-type intrusion within the late-Proterozoic Padhar mafic-ultramafic complex (PMUC), situated along the Central Indian Tectonic Zone (CITZ). The intrusion exhibits a differentiated composition, including peridotite, pyroxenites, hornblende gabbros and diorite. We adopt an integrated approach that combines field studies with analyses of major oxides, in-situ trace elements, and rare-earth element geochemistry. The field evidences of PMUC displays concentric zoning, with a core of dunite surrounded by wehrlite, olivine clinopyroxenite, clinopyroxenite, hornblende clinopyroxenite, and gabbro akin to Alaskan type intrusions. The primary minerals in the PMUC include olivine (forsterite), pyroxene (Cpx and Opx), amphibole, phlogopite, chromite, and magnetite, while secondary minerals like serpentine, chlorite, and talc are also present. The increase in magnesian number (Mg#) of olivine (70–77), orthopyroxene (53–73), and clinopyroxene (67–88) from mafic to ultramafic units indicates differentiation from a common parent melt. The geochemical signature, including negative Nb and Zr anomalies and positive Rb anomalies, suggests fluid metasomatism from slab sediments. The presence of a hydrous parent magma is inferred from the Mg# of early-formed olivine and high amphibole content. Tectonic discrimination plots of pyroxene and amphibole minerals, combined with in-situ trace element chemistry and bulk rock geochemistry, indicate an arc-related origin. The data suggest fluid-driven subduction zone metasomatism, characteristic of Proterozoic Alaskan-type tectonics within the CITZ. Platinum-group element geochemistry shows a high (Pt + Pd)/(Ir + Ru) ratio, similar to that of intrusive rocks of Alaskan types. Geological and geochemical data further support that the PMUC represents a shallow-level (ca. 17 km) segment of a Proterozoic arc, with minor ultramafic units acting as conduits for arc magma in the Betul Belt.