Origin and tectonic significance of the Huangling massif within the Yangtze craton, South China

As the oldest exposed basement and the typical sedimentary cover of the Yangtze craton, the Huangling massif is a suitable place to decipher the tectonics of South China block. Structural analysis shows that the Huangling massif has an elliptic domal shape with N–S striking long axis, an asymmetric antiform with a steep western flank and a gentle eastern flank. There, three litho-tectonic units are recognized, from inner to outer parts: (1) Archean– Paleoproterozoic metamorphic rocks intruded by Neoproterozoic granitoids; (2) Neoproterozoic to Jurassic sedimentary envelope around the dome core; (3) Cretaceous terrigeneous alluvial–fluvial deposits, unconformably overlying the dome flanks. Coeval with the uplifting of the massif, the pre-Cretaceous strata on the western and eastern flanks of the Huangling massif were involved in a series of folds with nearly N–S axes and layer-parallel slip structures with top-to-the-W and top-to-the-E motion, respectively. The subsequent brittle normal faulting controlled the deposition of the graben or half-graben basins on both flanks. Cooling history reveals that the Huangling massif underwent uplifting between 160 Ma and 110 Ma with an average cooling rate of 2–3 °C/Ma. Moreover, the Huangling area was not significantly affected by the Early Paleozoic and Triassic orogenies of South China. Comparable with the contemporaneous extensional structures, such as metamorphic core complexs, syntectonic plutons bounded by ductile normal faults, and rift-related basins in eastern China, it is proposed that the Huangling massif, might be an extensional structure controlled by a weak crustal extension. In this case, it will represent the western front of the Late Mesozoic lithospheric thinning in entire eastern China. However the compressional model cannot be ruled out.