Geology, geochronology and genesis of gold desposits in the West Quinling Orogen, central China

[Truncated abstract] The gold metallogeny of the West Qinling Orogen of central China is a main subject of this contribution. The thesis begins with the studies on magmatism aiming to improve the understanding of the tectonic setting of the region. The methods used to achieve this were geochronological and geochemical investigations on various suites of Triassic granites. Efforts are made to characterize the major geochemical profiles of the various suites using original data and recent publications on the region. Magmatism is widespread in the Qinling Orogen, having commenced ca. 240 Ma and continued episodically until ca. 205 Ma in the Late Triassic. Magmatism shows spatial variation in timing. It began in the northwestern part of the orogen and intermittently progressed to the southeast to the North Qinling terrane. Magmatism was then widespread in the South Qinling terrane during the Late Triassic. Based on location and high-quality geochronology, a new division of Triassic intrusion has been proposed across the Qinling Orogen. Several critical geochemical differences have been summarized under this new division. First, the West Qinling suites are significantly enriched in Large Ion Lithophile Elements, including Cs, Rb, U, Th and K, whereas the East Qinling suites have moderate enrichment in these elements; second, there is an obvious transition from calcium to potassium enrichment in the Late-Triassic-West-Qinling suite, whereas the Late-Triassic-East-Qinling suite appears to follow a curved trajectory starting from high Na through K to high Ca; third, the Ba and Sr concentrations of the West Qinling suite have marked depeletions on mantle-normalized multi-element plots, whereas the East Qinling suites have relative enrichment of the two elements.