Abstract:

Ophiolite from Xigaze is one of well-outcropped rocks in the Yalung Zangpo ophiolite, southern Tibet. Elemental and Sr-Nd isotopic compositions of the basaltic rocks from Bainang ophiolite in Xigaze were studied in this paper. The rocks are calc alkalic series, with low TiO₂(0.6%-1.1%), high MgO(6.6%-8.7%), Al₂O₃(15.3%-16.0%) and LOI(2.8%-4.6%). The primitive mantle-normalized multi-element pattern of basaltic rocks is similar to that of the normal Mid-Ocean Ridge Basalt(N-MORB)with the characteristics of island arc, which suggests that the rocks are related to subduction processes. The geochemical characteristics of Sr-Nd reflect that mantle source of Bainang ophiolite is a little enriched MORB mantle. The geochemical characteristics of Tethyan Ocean are similar to those of the Indian sub-oceanic mantle, which further confirms that the Indian sub-oceanic mantle is inherited from the Tethyan Ocean geochemical domain.

Key words: Bainang ophiolite, geochemical characteristic, source characteristic, Yalung Zangpo ophiolite, Tibet