Akademik Veri Yönetim Sistemi
Lithos, cilt.532-533, 2026 (SCI-Expanded, Scopus)
The accretion and growth of the oceanic lithospheric mantle are fundamental processes in plate tectonics and crustal evolution, driven primarily by melt-pyrolite interactions. Ophiolites, as remnants of ancient oceanic lithosphere, preserve critical records of lithospheric evolution, making them invaluable for investigating melt percolation and channelized flow in juvenile oceanic mantle. This study examines the Cuobuzha ophiolitic mantle peridotites and associated chromitites within the Yarlung-Zangbo suture zone (Neo-Tethyan domain) through integrated petrological, geochemical, and thermodynamic analyses. The mantle sequence is dominated by spinel harzburgite, with subordinate massive podiform and vein-like chromitites. Geochemical characteristics of the harzburgites—including various whole-rock CaO (1.38–2.04 wt%), Al2O3 (1.32–1.93 wt%), and spinel Cr# (17.0–51.7)—closely resemble those of abyssal peridotites. Trace element modeling of clinopyroxene indicates a polybaric melting history, involving 0–6% partial melting in the garnet stability field followed by 4–9% melting in the spinel facies. Subsequent melt percolation is evidenced by the occurrence of pargasite and light rare earth element (LREE) enrichment in both whole-rock (LREE = 0.059–0.116 ppm) and clinopyroxene compositions (LREE =0.194–0.466 ppm). Thermodynamic simulations suggest that the harzburgites were infiltrated by minor volumes of hydrous forearc basaltic melt in upper mantle (1.0–1.5 GPa, 1350–1050 °C, and FMQ-0.6 to FMQ-0.2). The chromitites are classified as high-Cr type, with chromite Cr# values of 71.9–78.2. Equilibrium calculation indicates that these chromitites crystallized from channelized boninitic melts migrating through the harzburgites. Collectively, the Cuobuzha ophiolitic mantle records two distinct melt-rock interaction events: (1) pervasive percolation of forearc basaltic melts, and (2) focused flow of boninitic melts forming high-Cr chromitites. Their coexistence reflects progressive slab deepening and intensification of subduction-related signatures during the initial stages of subduction.