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<p>The Chumathang granitoid of eastern Ladakh Trans-Himalaya records a magmatic evolution from subduction-related arc magmatism to syn-collisional crustal melting during the Himalayan orogeny. Field and petrographic relations define two contrasting phases an early hornblende-bearing metaluminous granodiorite and a later muscovite-bearing peraluminous leucogranite. The granodiorite displays calc-alkaline, magnesian and oxidised signatures (SiO<sub>2</sub>= 63.7–68.7 wt%; ASI = 0.85–1.11) with moderate LREE enrichment, flat HREE trends and weak negative Eu anomalies consistent with derivation from a metasomatized mantle wedge modified by subduction fluids. The leucogranite is highly siliceous (71.99-76.1wt%) peraluminous (ASI = 0.9–1.09) and strongly depleted in Sr, Ba and Zr indicating partial melting of lower crust under thickened oxidising conditions (Fe<sub>2</sub>O<sub>3</sub>/FeO ≈ 0.9; 700–1000 °C). Its elevated Rb/Sr ratios and magnesian-ferroan transition mark advanced fractionation and crustal anatexis during the syn-collisional stage. Together these lithologies document the progressive shift from mantle-dominated subduction-related magmatism to crust-derived melting during Himalayan convergence. The Chumathang granitoid thus preserves a coherent record of the tectono-magmatic transformation that accompanied the closure of the Neo-Tethys Ocean and provides new insight into magma source evolution and crust-mantle interaction in continental collision zones. </p>

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Geochemical characteristics of magmatic phases in Chumathang granitoids, NW Ladakh Himalaya, India: implications for tectonic setup and magmatic evolution of granites

  • 期刊论文

  • 发表日期：

    2026年4月11日

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  • Stanzin Namga,
  • Pankaj K. Srivastava,
  • Pawan Singh

摘要

The Chumathang granitoid of eastern Ladakh Trans-Himalaya records a magmatic evolution from subduction-related arc magmatism to syn-collisional crustal melting during the Himalayan orogeny. Field and petrographic relations define two contrasting phases an early hornblende-bearing metaluminous granodiorite and a later muscovite-bearing peraluminous leucogranite. The granodiorite displays calc-alkaline, magnesian and oxidised signatures (SiO2= 63.7–68.7 wt%; ASI = 0.85–1.11) with moderate LREE enrichment, flat HREE trends and weak negative Eu anomalies consistent with derivation from a metasomatized mantle wedge modified by subduction fluids. The leucogranite is highly siliceous (71.99-76.1wt%) peraluminous (ASI = 0.9–1.09) and strongly depleted in Sr, Ba and Zr indicating partial melting of lower crust under thickened oxidising conditions (Fe2O3/FeO ≈ 0.9; 700–1000 °C). Its elevated Rb/Sr ratios and magnesian-ferroan transition mark advanced fractionation and crustal anatexis during the syn-collisional stage. Together these lithologies document the progressive shift from mantle-dominated subduction-related magmatism to crust-derived melting during Himalayan convergence. The Chumathang granitoid thus preserves a coherent record of the tectono-magmatic transformation that accompanied the closure of the Neo-Tethys Ocean and provides new insight into magma source evolution and crust-mantle interaction in continental collision zones.