The protoliths of central Himalayan eclogites

Abstract Eclogites represent the highest pressure conditions yet observed from rocks thrust to surface in central Himalaya. A detailed investigation of protolith nature these eclogites is needed better understand pre-Himalayan geological history. Retrogressed were collected Thongmön (Dingri County) and Riwu (Dinggye County), Himalaya, China. We investigated bulk rock major trace elements, Sr-Nd isotopes, zircon geochronology, Hf-O isotopes. These retrogressed experienced five stages metamorphic evolution prograde amphibolite-facies peak eclogite-facies, high granulites-facies, granulites-facies then final overprinting during exhumation. Geochemically, they are subalkaline basalts with FeO contents a tholeiitic affinity; elements show similarities enriched mid-ocean ridge basalts. Bulk have wide range εNd(t) values −0.24 +7.08, an unusually initial 87Sr/86Sr ratios 0.705961–0.821182. Zircon relict magmatic cores both yield consistent age ca. 1850 Ma, heavy rare earth element patterns significant negative Eu anomalies. oxygen isotopes signatures δ18O = 5.8–8.1‰, εHf(t) –4.85 +9.59, two-stage model ages (TDM2) 1.91–2.81 Ga. Metamorphic overgrowth zircons much younger 14 Ma. Integration all above data suggests that Himalayan might be Proterozoic continental flood North Indian Plate, generated under post-collisional extension setting assembly Columbia Supercontinent. Occurrence Neoproterozoic–early Paleozoic 1.85 Ga regional crystalline may reflect either unrecognized sub-horizontal Main Central Thrust exposure(s) or exhumation deeply cut part Greater Crystalline complex. In combination previous reports Late Cretaceous, Neoproterozoic, similar but Paleoproterozoic protolith, it clear originate multiple sources protolith.