Lithology, kinematics and geochronology related to Late Mesozoic basin-mountain evolution in the Nanxiong-Zhuguang area,

The Nanxiong red-bed basin and its adjacent Zhuguang granite form a distinctive basin-mountain landform in the Nanling region, South China. Research results suggest that the Zhuguang granite is a polyphase composite pluton developed on the metamorphic basement of the paleo-Tethys-paleo-Asian tectonic regime and possesses geometrical and kinematic features of hot-doming extensional tectonics at the middle-upper crustal level, which is considered as a magmatic complex that resulted from the collision-orogeny during the Indosinian Period, the subduction-consuming during the Early Yanshanian Period and the intra-continental basaltic underplating and deep-seated geodynamics during the Late Yanshanian Period. The Nanxiong basin is a Late Cretaceous-Paleogene asymmetric faulted basin that is characterized by a fault boundary on the northern side and an uncomformable boundary on the southern side, its deposit center was migrated gradually from south to north. Structural kinematic results on the basin-mountain coupled zone demonstrate that the ductile and the brittle rheological layers show a quite coincident sense of shear, implying that it is a continuous process from the ductile extensional deformation followed by locally sinistral strike-slip shear at a middle-crustal level to the brittle tensional deformation at a upper-crustal level during formation of granitic doming extensional tectonics. The Zhuguang granite and the Nanxiong faulted basin constructed a semi-graben tectonic system. Lithological and geochemical results suggest that the Late Triassic to Jurassic granitic bodies in the Zhuguang have some similar features: high SiO2, Al2O3, K2O contents, alkalinity index ＞ 2.8, ANKC value ＞ 1.1, LREE-enriched pattern with high REE contents, marked negative Eu anomalies, enrichment in Rb and Th, depletion in Ba and Nb, showing a K-rich and Al-rich calc-alkaline affinity, which suggest a continuous magmatic evolution from Late Triassic to Jurassic. Formation of Nanxiong basin and evolution of basin-mountain system were controlled both by the Zhuguang granitic-doming and the regional extensional tectonics.Development of the olivine basalt in the basin suggests that tension action was very strong during lava eruption. The magma-type zircon grains of basalt from the Nanxiong basin yielded the SHRIMP age of 96±1Ma, providing reliable geochronological constraint on the tectono-thermal event and basin-mountain evolution in the Nanling region, South China.

作 者： SHU LiangShu DENG Ping WANG Bin TAN Zhengzhong YU Xinqi SUN Yan   作者單位： SHU LiangShu,WANG Bin,YU Xinqi,SUN Yan(Department of Earth Sciences,Nanjing University,Nanjing 210093,China)

DENG Ping(Department of Earth Sciences,Nanjing University,Nanjing 210093,China;Research Institute No.290,CNNC,Shaoguan 512026,China)

TAN Zhengzhong(Research Institute No.290,CNNC,Shaoguan 512026,China) 

刊 名： 中國科學D輯（英文版）  SCI 英文刊名： SCIENCE IN CHINA SERIES D EARTH SCIENCES  年，卷(期)： 2004 47(8)  分類號： P5  關鍵詞： lithology   structural kinematics   basin-mountain evolution   SHRIMP age   Zhuguang granite   Nanxiong basin