Petrogenesis of the Early Paleoproterozoic Felsic Metavolcanic Rocks from the Liaodong Peninsula, NE China: Implications for the Tectonic Evolution of the Jiao-Liao-Ji Belt, North China Craton

The early Paleoproterozoic (ca. 2.2-2.1 Ga) tectonic evolution of the Jiao-Liao-Ji belt (JLJB) is a continuous hot topic and remains highly controversial. Two main tectonic regimes have been proposed for the JLJB, namely arc-related setting and intra-continental rift. Abundant ca. 2.2-2.1 Ga volcanic rocks were formed in the JLJB, especially in the Liaodong Peninsula. These ca. 2.2-2.1 Ga volcanic rocks therefore could host critical information for the evolution of the JLJB. In this study, we report a suit of ca. 2.2-2.1 Ga felsic metavolcanic rocks in the Liaodong Peninsula of the JLJB to provide new insights into the above issue. Zircon U-Pb dating reveals that the felsic metavolcanic rocks were erupted at 2185-2167 Ma. They have variable & epsilon;Hf(t) values (-0.70 to +9.69), high SiO2 (66.30-75.30 wt.%) and relatively low TiO2 (0.03-0.78 wt.%), tFe2O3 (0.55-5.03 wt.%), MgO (0.17-8.76 wt.%), Cr (9.16-67.30 ppm), Co (2.01-7.00 ppm) and Ni (3.90-25.70 ppm) contents with enrichments in light rare earth element (REE) and large ion lithophile element (LILE), and depletions in heavy REE and high field strength element (HFSE). Geochemical and isotopic results indicate that the felsic metavolcanic rocks were sourced from partial melting of ancient Archean TTG rocks and juvenile lower crustal materials. Combined with coeval A-type granites, bimodal volcanic rocks and the absence of typical arc magmatism, the most likely tectonic regime at ca. 2.2-2.1 Ga for the JLJB is an intra-continental rift.