Palaeostress analysis using fault-slip data from the Xiangdong tungsten deposit in the central south China continent: Evolution of intraplate stress in the Middle Mesozoic

Abstract

In the central South China continent, the Xiangdong tungsten deposit associated with Late-Jurassic granitic intrusion offers an opportunity to examine the evolution of intraplate stress between the Late Jurassic and Early Cretaceous, which was a time of transition from regional shortening to regional extension. NE–ENE-striking, steeply-dipping, opening-mode tungsten-bearing quartz veins constitute the deposit. Favorable conditions for vein formation where densely spaced arrays have non-curving tips occur under remote stress with a large stress difference and hence in this case probably aligned with the horizontal maximum principal stress axis. Palaeostress analysis using fault-slip data measured on the side walls of underground mine levels yielded the optimal solution of two stresses characterized by an NNW–SSE-shortening strike-slip regime and an NNW–SSE extensional regime. Based on field observations, the first tectonic phase existed during meso- and epi-thermal mineralization, probably owing to the collision between the Siberia and Mongolia–Sino-Korean continents far to the north at the time, and the second tectonic phase appeared after hydrothermal mineralization, as a result of Cretaceous regional rifting. Therefore, multiple strike-slip deformations would have involved the study area during hypo- and epi-thermal mineralization in the Late Jurassic. This evidence does not support the mainstream extension model for Mesozoic tungsten mineralization in central South China.