Geochronology, Accretion and Tectonic Framework of Precambrian Continental Crust of Eastern China

摘要

Eastern China consists of three major Precambrian continental blocks: the North China Block (NCB), the Yangtze Block (YB) and the Cathaysia Block (CB). The NCB is composed mainly of Archaean basement with the oldest sialic rocks as old as early Archaean (ca. 3.8 Ga). The most important crustal growth in the NCB took place at 3.0-2.8 Ga. Two periods of crustal reworking accompanied by some juvenile crusta! growth are the latest Archaean (ca. 2.5 Ga) and early Palaeoproterozoic (2.4-2.0 Ga), respectively. It was finally cratonized following the late Palaeoproterozoic LUliang Orogeny of ca. 1.8 Ga. The oldest rocks in the YB is of late Archaean age (2.8-2.5 Ga), probably representing the crustal nucleus of the YB. Rapid crustal growth and extensive reworking during the late Palaeoproterozoic to Mesoproterozoic resulted in the formation of the continental basement of the YB. The basement rocks in the CB are of Palaeoproterozoic age of ca. 1.8 Ga, and the major crustal growth in the CB took place during the Proterozoic. The unexposed late Archaean crust, however, is postulated to exist based on the available radiometric age data. The collision of the CB to the YB took place during the early Neoproterozoic Jinning Orogeny when both oceanic and continental arcs accreted to the southern margin of the YB, accompanied by extensive crustal rcmelting and some newly mantle input. Whereas, the timing of the NCB-YB collision is still controversial, the Early Palaeozoic (Caledonian-age) and the Triassic (Indosinian) collision models being the most probable.