Petrochronology and petrogeochemistry of the Tamulangou Formation in Tahe area, northern Da Hinggan Mountains NE China: Geological implication

Abstract

This study reports petrography, petrogeochemistry and geochronology of Tamulangou Formation, which are located in Tahe, northern Da Hinggan Mountains, northeast China. In this study, we discussed their formation ages, petrogenesis, and tectonic environment. Zircon U-Pb dating results suggest formation ages of 148.1±1.95Ma and 161.5 ± 1.9 Ma for the conglomerate gravel, and the basaltic andesite, respectively. The geochemical characteristics indicate that the volcanic rocks in Tamulangou Formation are high-K calc-alkaline-shoshonitic rock that that formed in a continental intraplate environment. All volcanic rocks of Tamulangou Formation in the study area are enriched in large ion lithophile elements and light rare earth elements and depleted in high field strength elements and heavy rare earth element. Combined with geochemical characteristics of the volcanic rocks and previous studies on the region, we concluded that the magma source of the volcanic rocks in the Tamulangou Formation derived from the enriched lithospheric mantle formed by metasomatism of subduction fluids. Comprehensive study suggested that the volcanic rocks from Tamulangou Formation in Tahe region all formed in a tectonic environment of lithospheric extension triggered by post-orogenic extension after the closure of the Mongol-Okhotsk Ocean.