The Hunan-Jiangxi strike-slip fault system in southern China: southern termination of the Tan-Lu fault

The NNE-trending Hunan-Jiangxi strike-slip fault system (HJSFS) of southern China comprises three NNE-trending primary faults (the Anhua-Chengbu fault, the Chalin-Chenxian fault, and the Ganjiang fault) with associated NE- and NW-trending secondary faults. A series of linear Bouguer gravity lows coincide with these NNE-trending faults and their associated secondary ones. En echelon basins and ranges occurring at fairly regular intervals of 20-40 km are strictly situated along the NE- and NNE-trending faults and within their releasing and restraining bends or stepovers, respectively. Several large streams, in general, follow the strike-slip faults. These features demonstrate a close relationship between the modern landforms and the HJSFS. Sub-linear seismically active zones and hot springs are also distributed along or adjacent to the faults, indicating this strike slip fault system is still active. The spatial and temporal relationships between the strike-slip faults and Mesozoic granitic rocks suggest that these faults acted as the loci for magmatic activity at that time. The deformed fold axes, together with the structural framework of the HJSFS itself, indicate a clockwise sub-vertical rotation of large-scale blocks restricted by the primary strike-slip faults. A variety of structural evidence suggests that the HJSFS experienced three deformation stages, i.e. transpression, transtension and compression. On the basis of offsets of pre-Late Triassic lithofacies, Mesozoic granites, and the Late Silurian suture zone between the Yangtze and Cathaysia Blocks, the total sinistral displacement of the HJSFS is estimated to be 50-60 km. The HJSFS is comparable to the Tan-Lu fault with respect to the fault geometry and evolution history. However, the HJSFS has a different structural style, displacement and earthquake intensities from those of the central segment of the Tan-Lu fault, resulting from the differences in crustal structures of the North China Block and South China Block. (C) 2001 Elsevier Science Ltd. All rights reserved.