Abstract

The time and the environment of formation of igneous rocks along the southern margin of the Yangtze continental block in southern Anhui Province and northeastern Jiangxi Province, China, are discussed. Sm-Nd dating for samples from two ophiolite suites give ages of about 1 Ga. Late Proterozoic granodiorites in the study area have ages of about 0.9 Ga and have normal intrusive relations against Banxi Group metamorphic country rocks. Trace element abundances and initial Nd isotope ratios for ophiolite and Proterozoic granodiorites are consistent with formation in an island-arc environment. In contrast, Sr and Nd isotopes for Mesozoic granitoids of the region suggest that they are products of remelting of crustal sources similar to the basement of the Yangtze block. These relations do not support a recently proposed Mesozoic overthrust tectonic model for southeast China, but rather favor a late Precambrian collision history for the Yangtze and Cathysia blocks.

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