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<p>The present study discusses the whole-rock major element, trace element, and Nd-isotope geochemistry of arc-related mafic rocks from Dras, Shergol, Nidar, and Spongtang ophiolitic rocks along the Indus Suture Zone (ISZ), Ladakh Himalaya. The Shergol gabbros and Dras basalts from western Ladakh have positive <i>ε</i><sub>Nd</sub> (<i>t</i> = 140&#xa0;Ma) values (+5.3 to +8.3 and +4.9 to +6.1, respectively) comparable to Spongtang and Nidar ophiolitic mafic rocks from other parts of ISZ. The lower ratios of Ta/Hf (average = 0.46), Th/Yb (average = 0.14), Nb/Yb (average = 0.67), Nb/Ta (1–5), and Zr/Hf (2–6) and higher large-ion lithophile element (LILE)/high-field-strength element (HFSE) ratios in the Shergol gabbros reflect limited subduction influence, whereas the higher ratios of Ba/Nb = 2.4–110, Rb/Nb = 0.3–45, La/Nb = 1.1–4, Nb/Ta (5–20), and Zr/Hf (21–39) with constant Nb/Y, Th/Yb, and Nb/Zr ratios of the Dras basalts are consistent with fluid-added mantle sources. This temporal variation in the subducting slab-derived fluids is also evident in terms of synchronized variation in their Nd isotope and HFSE ratios. Rare earth element (REE) modeling suggests that the observed depleted and enriched light rare earth element (LREE) patterns of the Ladakh ophiolitic mafic rocks could be the result of variable degrees of partial melting (5% to 25%) of the fluid-metasomatized mantle wedge. Thus, the observed geochemical variation in Ladakh ophiolitic mafic rocks could be related to the spatially and temporally variable metasomatism oblique to the intra-oceanic island arc subduction zone analogous to the Izu-Bonin-Mariana arc system within the Western Pacific.</p>

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Isotopic and geochemical variation of Mesozoic ophiolitic magmatic rocks from the Ladakh Himalaya: A magmatic response of the changing subduction nature

  • 期刊论文

  • 发表日期：

    2025年10月18日

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  • Irfan M. Bhat,
  • Hiredya Chauhan,
  • Talat Ahmad

摘要

The present study discusses the whole-rock major element, trace element, and Nd-isotope geochemistry of arc-related mafic rocks from Dras, Shergol, Nidar, and Spongtang ophiolitic rocks along the Indus Suture Zone (ISZ), Ladakh Himalaya. The Shergol gabbros and Dras basalts from western Ladakh have positive εNd (t = 140 Ma) values (+5.3 to +8.3 and +4.9 to +6.1, respectively) comparable to Spongtang and Nidar ophiolitic mafic rocks from other parts of ISZ. The lower ratios of Ta/Hf (average = 0.46), Th/Yb (average = 0.14), Nb/Yb (average = 0.67), Nb/Ta (1–5), and Zr/Hf (2–6) and higher large-ion lithophile element (LILE)/high-field-strength element (HFSE) ratios in the Shergol gabbros reflect limited subduction influence, whereas the higher ratios of Ba/Nb = 2.4–110, Rb/Nb = 0.3–45, La/Nb = 1.1–4, Nb/Ta (5–20), and Zr/Hf (21–39) with constant Nb/Y, Th/Yb, and Nb/Zr ratios of the Dras basalts are consistent with fluid-added mantle sources. This temporal variation in the subducting slab-derived fluids is also evident in terms of synchronized variation in their Nd isotope and HFSE ratios. Rare earth element (REE) modeling suggests that the observed depleted and enriched light rare earth element (LREE) patterns of the Ladakh ophiolitic mafic rocks could be the result of variable degrees of partial melting (5% to 25%) of the fluid-metasomatized mantle wedge. Thus, the observed geochemical variation in Ladakh ophiolitic mafic rocks could be related to the spatially and temporally variable metasomatism oblique to the intra-oceanic island arc subduction zone analogous to the Izu-Bonin-Mariana arc system within the Western Pacific.