Deformation sequences and ore-controlling structures of the Chanziping–Daping gold mining area in Hunan Province, China

The Chanziping–Daping gold deposit area is located in the southwest section of the Xuefeng arc-shaped structural belt, with mainly NWW-NNW-trending and secondary NNE-trending Au veins. Existing studies proposed the NE-trending faults as the ore-passing and ore-bearing structures and the NW-trending faults as the ore-bearing structures. However, there is no clear and reliable understanding of the nature and age of ore-controlling faults. Given this, the authors carried out detailed field observation and analysis of surface outcrop structures and mineralization alteration, and then combined with regional structural characteristics, tectonic evolutions, and dating data, determined the deformation sequences and their ages in the Chanziping–Daping gold deposit area, and determined the types and attributes of ore-controlling structures. The study suggests that the study area experienced six main deformation events from early to late: Regional NWW compression during the late Silurian which resulted in the NNE-trending folds, slaty cleavages and brittle-ductile shear zones; Regional NNW compression in the late Middle Triassic which caused the formation of NWW-to-NW-trending dextral strike-slip faults and shear fractures, NS-trending sinistral shear fractures, NW- and NNE-trending conjugate shear fractures, NEE-trending thrust faults and superimposed folds; Regional NS compression in the early Late Triassic which led to the development of NW-to-NNW-trending dextral strike-slip faults and shear fractures, NNE-to-NE-trending sinistral shear fractures and faults, and NEE-trending sinistral kinks; Regional NWW-to-near EW-compression in the late Middle Jurassic which resulted in the NS-to-NNE-trending thrust faults, NW-to-NWW-trending sinistral shear fractures, NE-trending dextral thrust shear fracture, NNE-to-near NS-trending fracture cleavages, foliation folds and boudins; Regional NE compression in the middle-late Paleogene which led to the development of NNE-to-NS-trending dextral shear fractures and faults, NEE-trending sinistral shear fractures, NW-trending thrust faults and fracture cleavages; Regional NW compression during the late Paleogene to early Neogene which led to the formation of NE-trending thrust shear fractures and NWW-trending dextral shear fractures. The NNE-trending mineral veins in the study area formed in the late Silurian and the late Late Triassic, and the NWW-to-NNW-trending mineral veins formed in the late Late Triassic. The mineralization in the late Silurian was associated with the tectonic activation caused by the fault movement, and the mineralization in the late Late Triassic was related to large-scale granitic magmatism in the same period. The ore-passing structures are mainly the large NNE-trending faults, namely the brittle-ductile shear zones formed by NWW- compression in the late Silurian. The main ore-bearing structures are the NWW-to-NW-trending dextral strike-slip faults formed by NNW compression in the late Middle Triassic, NW-to-NNW-trending dextral strike-slip faults formed by NS compression in the early Late Triassic, with next NNE-trending brittle-ductile shear zones formed by NWW compression in the late Silurian