Two series of copper-gold deposits in the middle and lower reaches of the Yangtze River area (MLYRA) and the hydrogen, oxygen, sulfur and lead isotopes of their ore-forming hydrothermal systems

Based on studies on the geological characteristics of the copper-gold depos its in the middle and lower reaches of the Yangtze River area (MLYRA) and t heir hydrogen, oxygen, sulfur and lead isotope compositions, it is conclude d that there existed two series of copper-gold deposits. They are evolution al products of two ore-forming hydrothermal systems in different geodynamic settings and geological era. Series I is stratiform or stratabound copper- gold deposits. These deposits were formed by submarine exhalation and sedim entation of hydrothermal solutions in Hercynian tensional tectonic environm ent after hot brine ascending along contemporaneous faults and exhaled into the sea-floor. Series II consists of copper-gold deposits related to mediu m and acidic magmatic intrusions. Their mineralizations took place in Yansh anian in a tensional or a transitional period to the tensional tectonic env ironment from the composite of the tethys tectonic regime and the Paleo-Pac ific ocean tectonic regime, as well as in the upper mantle doming and crust al thinning environment. Copper-gold deposits were formed from the hydrothe rmal fluids, mixtures of magmatic water and pail of meteoric water, by comp lex water-rock interactions and coupling dynamic processes of transport-che mical reactions. Superposition is an important condition for the formation of the large-scale copper-gold ore deposits.