Study On The Tectono-magmatic Function And Fluid Metallogenic Process Of Typical Gold Deposits In Jidong Region, Hebei Province, China

Many gold deposits in Jidong region, which is one of the important concentrating area of gold deposits in China, were undergoing serious resource crisis for long-term exploiting. Rescent years deep mine prospecting in this area shows good prospecting effect and huge potencial in the deep of gold deposits. It is necessary to carry out further research work on gold deposits of Jidong area.Based on previous work and solid field work, understanding and progresses are obtained on the Jinchangyu, Huajian and Yuerya gold deposits by applying a lot of high quality testing analysis and new metallogenic theory. (1) The reginal tectonic evolution controlling and structural plane types of gold deposits in Jidong area are studied and summarized, and the mine field tstructural characteristics of Jinchangyu, Huajian, and Yuerya gold deposits are proposed. The Jinchangyu gold deposit is controlled by folds and schistosity zones, the Huajian gold deposit is controlled by folds and faults, and the Yuerya gold deposit is controlled by folds and fractures. (2) It is the first time using high precise Re-Os to date the molybdenite in Jinchangyu gold deposit. The results show that the mode age of six molybdenite samples, which were formed with gold deposit during the same period, is (242.4±5.4)Ma and (240.5±4.2)Ma, and the isochron age is 242.6±6.8Ma. It suggests that the mineralization of gold deposit began in Indosinian. (3) The metallogenic material migration and depositing environment are studied, and fluid ore-forming process is discussed by several methods, such as mineral alteration, fluid inlusions, trace elements, and stable isotope. (4) The Zircon LA-ICP-MS of precise isotopic age determination shows that the age of monzonitic granite and pink granite in Qinshankou intrusive is 193±2.4Ma and 199.7±1.5Ma respectively. Two period granites in Niuxinshan intrusive were formed at 186.8±2.6Ma and 153.7±4.1Ma respectively. (5) It is the first time putting forward the qingshankou granite and Niuxinshan granite belonging to A-type granite. It is believed that granite in Jidong area was formed during the transiton stage of post-collisional stage to post-orogenesis stage. It makes connections between tectono-magmatic function in Jidong area and the collision of Paleo-Asian Ocean in northern margin of north China plate. (6) The formation age and genesis of Jinchangyu, Huajian, and Yuerya gold deposits are discussed. It proposes that there were about 20Ma intervals between intense periods of magmatism in Jidong area. The appearance of albite vein with molybdenum represents the beginning of post-collision stage and mineralization in Jidong area. (7) It is confirmed that the Ore-forming geological body of Yuerya and Huajian gold deposit is yuerya and niuxinshan rock mass formed during the late stage respectively. The Ore-forming geological body of Jinchangyu gold deposit is the concealed Mesozoic granite in deep mineralization. (8) The relationship between magmatic evolution and mineralization of gold deposit is summarized. This paper emphasizes the response in Jidong area of magma structure and collision orogenesis by North China plate and Siberia plate during the Indo Chinese epoch. The structural weak plane compressed by Archean obduction and extension structure formed by the orogeny during late Palaeozoic controls the intruding upward of alkali magma and depositing of metallogenic material.