Integrated Spatial Analysis of Tectonic Processes in the Yarlung Zangbo Ophiolites Using Geochemical and Microstructural Proxies
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Understanding mantle-crust interactions and plate subduction dynamics during the closure of the Neotethys Ocean remains a critical challenge in solid Earth sciences. The Yarlung Zangbo Ophiolite Belt (YZOB) in southern Tibet, a pivotal archive of the Indo-Asian collision, preserves complex records of oceanic crust accretion and post-collisional adjustments, yet the emplacement mechanisms and tectonic significance of its constituent ophiolites remain debated. This study investigates the Saga, Sangsang, and Zhongba ophiolites to decode their genetic links to Neotethyan subduction dynamics and collisional tectonics. Integrating geological profiling, geochemical analyses, and Electron Backscatter Diffraction (EBSD) microstructural data, the research reconstructs multi-stage mantle processes and stress regimes. Results reveal that these ophiolites originated from a mid-ocean ridge setting, with geochemical gradients indicating progressive crustal assimilation during northward Indian Plate subduction. EBSD-derived crystallographic fabrics document a composite stress regime dominated by N-S compression and E-W shear, aligning with regional tectonic escape driven by plate convergence. The correlation between geochemical signatures and deformation microstructures establishes a three-phase emplacement model: Neotethyan slab rollback, crustal accretion under compression, and post-collisional shear-driven adjustment. This work innovatively bridges geochemical and microstructural proxies to resolve multi-scale tectonic processes, demonstrating that the YZOB records both ridge-derived mantle upwelling and syn-collisional crust-mantle recycling. These findings advance the understanding of ophiolite emplacement mechanisms in collisional settings and provide critical constraints for numerical models of subduction zone dynamics and mantle-crust interactions. The integrated methodology offers a novel framework for deciphering tectonic archives in ancient orogenic belts globally.