Zircon age and Sr-Nd-Hf isotopic composition of migmatite in the eastern Tengchong block, western Yunnan

The Tethyan belt in western Yunnan, being one of the important parts of the eastern Tethyan belt, is made up of several micro-continental blocks and orogenic belts in between. Provenance and evolution of basements within these blocks are rarely known due to limited exposure of the basements that were subjected to imprint of tectonic events. This study presents zircon age, geochemical composition and Sr-Nd-Hf isotopic characteristic of migmatite from the eastern part of the Tengchong block, to discussion the formation age and tectonic setting of the protolith. Protoliths of migmatite originated from Middle Proterozoic granodioritic to granitic material that was subjected to re-melting in late Mesozoic and probably later migmatitization. The analyzed rocks have depleted-mantle Nd modal ages of 1.9 to 1.5Ga and zircon Hf modal ages of 1.8 to 1.5Ga, different from those of the early Paleozoic and late Mesozoic granites exposed in the Baoshan block. Geochemically, they exhibit enrichment in light REEs, light-degree fractionation between middle and heavy REEs, significantly negative Eu-, Nb-, Ti-, Ba-, and Sr-anomaly. Initial εNd values (-1.7 to 3.5 at 1.0Ga) of whole-rocks and zircon initial εHf values (mean values 10.5 to 13.1 at 1.0Ga), combined within chemical feature, can imply that there was probably are-related magmatism in the eastern part of the Tengchong block in middle Proterozoic.