Geochemical characteristics and tectonic significance of Proterozoic Songshugou Formation volcanic rock in Qinling Mountain, Shaanxi Province

The middle-upper Proterozoic Songshugou Formation is exposed in the south of Zhouzhiheihe Huangcaopo and the north of Zhashuifeng Street. It consists of basic igneous rocks with vesicular structure, amygdaloidal structure and local pillow structure, together with small amounts of clastic rocks. The basic igneous rocks experienced amphibolite facies metamorphism. An analysis of the Sognshugou Formation shows that, it is similar to the mid ocean ridge in petrochemical characteristics. The curve is flat, and there exists the enrichment of LREE relative to HREE. The trace element spider diagram shows it is rich in high field elements and large ion lithophile elements. An analysis of the structural environment shows that it is characteristic of the mid ocean ridge.