Geochemical and Nd-Hf Isotopic Constraints on the Petrogenesis of an Archean Granitoid in the Erguna Massif, NE China

Crystalline basement and Precambrian crustal growth of the continental massifs within the Central Asian Orogenic Belt (CAOB) are still pending problems. Our geological and geochemical investigations identified an Archean (2606 Ma) granitic pluton in the Biliya area of the Erguna Massif. The Neoarchean granitoids show high and positive in-situ zircon SMALL ELEMENT OFHf(t) (+0.3 to +10.0), whole-rock SMALL ELEMENT OFNd(t) (+4.8) and whole-rock SMALL ELEMENT OFHf(t) values (+2.1). They are characterized by high Y + Ce + Zr + Nb (> 220 ppm) and Zr contents and could be classified as A-type granites. These granitoids are characterized by high Zr saturation temperatures (T-Zr) (796-836 degrees C). They were derived from partial re-melting of juvenile mafic lower crust in an intracontinental back-arc extensional environment. This newly identified Neoarchean granitic pluton may represent the crystalline basement of the several continent massifs within the CAOB, and their high SMALL ELEMENT OFHf(t)-SMALL ELEMENT OFNd(t) values may also indicate the occurrence of lateral crustal growth events in these massifs during the Neoarchean.