Rock geochemical characteristics of the Neoproterozoic Wuyishan ophiolite mélange

Abstract：According to a rock geochemical study, basalt and andesite in the Neoproterozoic Wuyishan ophiolite mélange in the South China orogenic belt may be divided into two types: one is tholeiite, which is characterized by TiO2=2.26％-2.59％ (average 2.43), LREE being richer than HREE, (La)N/(Yb)N=6.4-9.4 (average 7.8), relative enrichment in Nb, Ta and Ti and the trace element characteristics being similar to those of OIB; and the other is of calc-alkaline type, which is characterized by TiO2=0.69％-0.93％ (average 0.83％), LREE enrichment, (La)N/(Yb)N=4.2-12.6 (average 8.4), weak negative Eu anomaly, lower Nb, Ta and Ti contents and enrichment in LILE such as Ba, Rb, Th and K, shows the characteristics of IAB and is the product of subduction. The two types of rock coexist in the ophiolite mélange and record the history of the subduction and closing of a paleo-ocean between the Yangtze block and Cathaysia block and arc-arc collision and amalgamation.