Abstract
A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province, South China. It is an S-type granite characterized by high K2O, Al2O3 and low SiO2, Na2O contents with high A/CNK ratio of 1.22 for the whole rock. Zircons with stubby morphology from the gneissic granite yield 206Pb/238U ages ranging from 326 to 301 Ma with a weighted average age of 313±4 Ma, and negative ɛHf(t) values from −8.35 to −1.74 with Hf model ages (TCDM) of 1.43 to 1.84 Ga. This S-type granite probably originated from late Paleoproterozoic crust in intracontinental orogeny. Integrated with previous results on paleogeographic reconstruction of South China, the nature of Paleozoic basins, Early Permian volcanism and U-Pb-Hf isotope of detrital zircons from the late Paleozoic to early Mesozoic sedimentary rocks, we suggest the occurrence of a late Paleozoic orogeny in the eastern Cathaysia Block, South China. This orogenic cycle includes Late Carboniferous (340–310 Ma) orogeny (compression) episode and Early Permian (287–270 Ma) post-orogenic or intraplate extension episode. Therefore, the late Paleozoic magmatism in the southeastern South China probably occurred during the intraplate orogeny rather than the arc-related process.
Highlights
A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province, South China
Li et al [20] interpreted that ~265 Ma granitic magmatism in Hainan Island was induced by the subduction of the Paleo-Pacific ocean plate beneath the South China Block (SCB)
They related it to the amalgamation of the SCB with the Indochina-South China Sea plate during the convergence of the late Paleozoic Pangea supercontinent
Summary
The coastal region of the SCB can be divided into three parts by the NE-striking Zhenghe-Dabu and ChangleNan’ao faults (Figure 1(a)). The Caledonian fold belt is located to the west of the Zhenghe-Dabu fault, containing Precambrian basement rocks, early Paleozoic sedimentary rocks and Caledonian granites, whereas late Mesozoic granites, volcanic and sedimentary rocks are dominant to the east of the fault. Some high-grade metamorphic rocks and Paleozoic sedimentary rocks are sparsely exposed as inliers to the east of the Zhenghe-Dabu fault. It is worthy to note that these inliers are confined to the west of the Fu’an-Nanjing fault (Figure 1(a)). A fresh granitic gneiss sample was collected near the Wufenglou village, Zhouning County of Fujian Province, to the east of the Zhenghe-Dabu fault (Figure 1). Sample FN10-5-2 is a biotite-rich granitic gneiss with porphyroclastic texture (Figure 2), suggesting that it underwent brittle-ductile deformation. It shows an affinity with typical S-type granites characterized by high contents of K2O and Al2O3, and low SiO2 and Na2O contents with low Na2O/K2O ratio of 0.30 and high A/CNK value of 1.22
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