Provenances of the Carboniferous clastic sedimentary rocks and the paleogeography of the Tengchong block: constrains on detrital zircon U-Pb ages and Hf isotopes

• 1、School of Earth Sciences and Resources, China University of Geosciences, Beijing, Beijing 100083

Abstract：To constrain the paleoposition of the Tengchong block within Gondwana during the Early Paleozoic, we performed in-situ U-Pb and Hf isotope analyses on detrital zircons from Carboniferous strata in the Tengchong block. The age distributions yield dominant Neoarchean (~2.5 Ga), Mesoproterozoic (1.7-1.4 Ga), Grenvillian (~0.95 Ga), and Pan-African (0.65-0.5 Ga) age groups. Hf isotope compositions of Mesoproterozoic, Grenvillian, and Pan-African zircon age groups exhibit wide range of εHf(t) suggesting their diverse sources. The oldest Hf model ages indicates that the source magma included reworked Eoarchean (~3.7 Ga) crustal materials. The remarkable resemblance of zircon age spectra and Hf isotopes from the Tengchong block with those from Tethyan Himalayan, western Qiangtang and Indochina suggests that the Tengchong block was located along the Indian margin of Gondwana during the Early Paleozoic. The crustal εHf value changed from 0.5 (at 3550 Ma) to -17.9 (at 450 Ma) for the source area, and in Grenvillian and Pan-African, crustal growth only took a small portion.

Keywords： geochemistry；U-Pb age Hf isotope detrital zircon Gondwana margin Tengchong