Tectono-magmatic evolution of the Amet granite-gneiss terrane, Sandmata Complex (NW India): Implications for Paleoproterozoic crustal accretion during Columbia assembly

The Sandmata Complex in the Aravalli orogen (NW India) preserves an extensive Paleoproterozoic geological record characterized by granulite-facies metamorphism, granitoid magmatism, and multiphase deformation. This studyintegrates structural, petrological, geochemical, and geochronological data to reconstruct the tectonomagmaticevolution of garnet-bearinggranitoids and metamorphic history of the host gneissesin the Amet region.The gneisses record four deformation events (D₁-D₄), whereas the granitoids preserve three deformation phases (D₁-D₃).TheD₂-D₄in gneisses correspond temporally D₁-D₃in the granitoids.Crystallographic preferred orientation (CPO) analysesof granitoidsreveal a transition from monoclinic (S₁) to triclinic shear regimes (S₂-S₃), indicating progressive non-coaxial deformation. Quartz CPO patterns record WNW-ESE-directed (D₁) and NE-SW-directed (D₂-D₃) brittle-viscous shearing accompanied by dynamic recrystallizationat 500-600 ℃.The gneisses record syn-D₂peak metamorphic conditions of 5.8-6.6 kbar, 660-680 ℃. The Amet granitoids crystallized at 6.0-7.4 kbar, 730-775 ℃, and contain inherited garnet cores (Grt-I) with peritectic rims (Grt-I rim) and matrix garnets (Grt-II). REE patterns and negative Eu anomalies in the pre-D₁ garnets indicate a two-stage growth history related to evolving melt composition and P-Tconditions. U-Pb zircon dating constrains granitoid crystallization at ~1823 Ma. In-situ monazite geochronology records deformation events at ~1670 Ma (D₁) and ~949 Ma (D₂-D₃),the latter representing animprint of the Delhi Orogeny. These results indicate partial melting and magma emplacement, driven by long-lived subduction during the Aravalli orogeny. The findings of this studyprovide robust evidence of Paleoproterozoic magmatism and continent-scale collisions during ~2.1-1.8 Ga, highlighting the significance ofAravalli orogenin the assembly of the Columbia supercontinent.