GEOCHEMICAL CHARACTERISTICS AND TECTONIC SETTING OF OPHIOLITE OF DONGQIAO, TIBET

Ophiolites exposed in Dongqiao are mainly composed of metamorphic peridotites, gabbros and basalts. Through the analysis of major and trace elements of ophiolite in Dongqiao, it is concluded that the geochemical characteristics of its metamorphic peridotites are high content in Mg,Fe,Cr, and low content in Ti and REE. The gabbros and basalts are the transitional MORB type basalt. According to the data of trace elements in the ophiolite, the gabbros and basalts show the same characteristics as the spreading MORB, such as the depletion of elements of Nb, Ta and its relative enrichment of Rb, Sr and Ba. Meanwhile, according to the REE distribution patterns with no Eu anomaly, the gabbros and basalts are similar to Mid-Ocean Ridge Basalt.On the basis of its geochemical attribute, it is concluded that the ophiolite of Dongqiao geotectonic setting is formed in spreading ocean basin.