Rodingites in the Shergol ophiolitic melange in the Ladakh ophiolitic belt: Insights into rodingitization processes and geodynamic implications

Rodingites are reported for the first time in the Shergol ophiolitic melange in the northwest part of the Ladakh ophiolitic belt, which is associated with the Himalayan orogeny. These are embedded within serpentinites recording metasomatic processes driven by fluid-rock interactions and element transfer between mafic protoliths and the host ultramafic ophiolitic rocks. The Shergol rodingites are distinguished into two distinct types. Type I paragenesis includes clinopyroxene + garnet ± chlorite ± zeolite, whereas Type II comprises garnet + clinopyroxene + vesuvianite ± quartz. Mineralogical and geochemical data suggest that these two types correspond to a two-stage metasomatic evolution: initially, a main rodingitization phase during which mafic protoliths transformed into rodingites (Type I), followed by a derodingitization stage, during which calcium-rich minerals were replaced by Mg-rich minerals, forming chlorite-dominated blackwall zones at the rims. These rodingites are regarded as metasomatic derivatives of mafic protoliths that include gabbro and basaltic dolerite. Rodingitization resulted in significant depletion of Si, Na, K, along with Ca and in cases Mg enrichment. It is also associated with significant mobilization of large-ion lithophile elements (LILE). High Mg#, low k, Rb, U, Th, and Pb concentrations, with low ⁸⁷Sr/⁸⁶Sr Isotopic signatures, suggest a depleted mantle source for the protoliths.  Pressure-temperature conditions indicate that rodingitization occurred under low- to moderate-grade metamorphic conditions (250-325°C and ~3 kbar, respectively).

Keywords: Shergol ophiolitic belt, Rodingite, metasomatism, MORB, Ladakh Himalaya