Geochronological and geochemical constraints on the petrogenesis of Middle Paleozoic (Kwangsian) massive granites in the eastern South China Block
To achieve a better understanding of the Kwangsian orogenic event of the eastern South China Block, this paper documents a set of new zircon U–Pb geochronological and Hf isotopic data and whole-rock elemental and Sr–Nd isotopic analytical results for the representative massive granite intrusions across the Jiangshan-Shaoxing fault. The studied samples are classified into two groups, representing the rocks from the Cathaysia Block to the east of the Jiangshan-Shaoxing Fault (Group 1) and those from the eastern Yangtze Block between the Anhua-Luocheng and Jiangshan-Shaoxing faults (Group 2). The Group 1 samples gave the zircon U–Pb ages of 405–454 Ma and eHf(t) values of - 3.6 to - 15.2 with Hf model ages of 1.6–2.4 Ga. Group 2 yielded the zircon U–Pb ages of 400–432 Ma and eHf(t) values of - 0.2 to - 12.7 with Hf model ages of 1.3–2.2 Ga. Geochemically, the Group 1 samples (A/CNK = 1.02–1.43) have relatively lower Al2O3, MgO, CaO, P2O5 and eNd(t) but higher K2O + Na2O than those of Group 2 (A/CNK = 0.93–1.44). Both groups show similar chondrite-normalized patterns of rare-earth elements with Eu/Eu* values of 0.15–0.92 and strongly negative Ba, Sr, Nb, P and Ti anomalies in primitive mantle-normalized spider diagrams. Their eNd(t) values range from - 11.1 to - 8.0 for Group 1, and - 8.9 to - 5.0 for Group 2, generally similar to those of Precambrian paragneiss and contemporaneous gneissoid granites in the eastern South China Block. Our geochronological results indicate that the Kwangsian massive granites in the eastern South China Block were crystallized between 400 Ma and 454 Ma, synchronous to the Kwangsian gneissoid granites along the Wugong and Wuyi-Baiyun-Yunkai domains in the eastern South China Block. The synthesis of these whole-rock geochemical and in-situ zircon Hf isotopic data suggests that both the Group 1 and 2 granites across the Jiangshan-Shaoxing Fault were predominantly derived from a crustal source with some proportional metapelitic and metaigneous
Downloadable Archival Material, Undefined, 2012
Elsevier BV, 2012