摘要
In Dulan County, Qinghai Province NW China, the arc volcanic sequences in the northern side of the Central Fault of the East Kunlun were metamorphosed progressively from upper greenschist facies in the south to epidote-amphibolite facies in the north. High-angle thrust deformation was developed synchronously with the peak metamor-phim and superimposed with later low-angle striking-slip deformation. Zircon U-Pb dating yields a concordant age of (448±4) Ma for the metavolcanics. Syn-kinematic hornblende and muscovite separated from the high-angle thrusting belt give 40Ar-39Ar plateau age of (427±4) Ma and 408 Ma, respectively. These results precisely constrain the timing of the closure of early Paleozoic volcanic basin (Proto-Tethys) over the eastern portion of the East Kunlun Orogen, and the thrust tectonic slice had a cool rate of ca. 9°C/Ma.
In Dulan County, Qinghai Province NW China, the arc volcanic sequences in the northern side of the Central Fault of the East Kunlun were metamorphosed progressively from upper greenschist facies in the south to epidoteamphibolite facies in the north. High-angle thrust deformation was developed synchronously with the peak metamorphim and superimposed with later low-angle striking-slip deformation. Zircon U-Pb dating yields a concordant age of (448± 4) Ma for the metavolcanics. Syn-kinematic hornblende and muscovite separated from the high-angle thrusting belt give 40Ar–39Ar plateau age of (427± 4) Ma and 408 Ma, respectively. These results precisely constrain the timing of the closure of early Paleozoic volcanic basin (Proto-Tethys) over the eastern portion of the East Kunlun Orogen, and the thrust tectonic slice had a cool rate of ca. 9°C/Ma.
基金
This work was supported by the National Natural Science Foundation of China (Grant No. 49972023)
China Geological Survey Bureau (Project on 1 : 250000 Scale Mapping Methods for Orogens in Western China)
a CRCG grant from the University of Hong Kong.
