The Ore-forming Fluid And Mineralization Of Micro-disseminated Gold Deposits In Western Jiangxi Province

In order to study the micro disseminated gold mineralization and exploration direction in the western depression belt of Jiangxi Pingle. This paper takes Deposit Geology, Structural Geology, Geochemistry as instruction. By collecting the deposit information of four gold deposits in the west of Jiangxi Province. Collecting fluid inclusions, Analysis the characteristics of the micro disseminated deposits in the west of Jiangxi Province.The main object of study is fluid inclusion which has been analyzed in petrography, micro-thermometry, it’s ingredients along with oxygen and hydrogen isotope. This paper discusses the evolution of the ore-forming fluid and ore deposit genesis in the research area, the main research conclusions are as follows:(1) The fluid inclusions of the west of Jiangxi Province Carlin-type Gold Deposit can be divided into three categories. The first type is gas-liquid inclusion of which the gas-liquid ratio is generally between5%and10%, it is of the largest number and longest lasting among the others; the second one is the rather rare vapor inclusion which has50%to60%of its volume occupied by gas; the last and the least type is three phase inclusion which consists of liquid aqueous solution, liquid carbon dioxide and vapor CO2+H2O.(2) The oxygen and hydrogen isotope feature shows that8D (smow) values around-30.3～-83.1,δ180(smow) is between-2.93and+16.94, whereas818O (H2O) locates within the radius of-5.19and+7.25; hence the ore-forming fluid is mainly originated from atmospheric rainfalls blended with a small amount of mixed acid fluid from magmatic water.(3) Besides, the fluid of local Carlin-type gold deposits has a usual range is1.9-8.6wt%NaCl. In addition, the density range of the fluid is as high as0.89～0.96g/cm3. On the other hand, the ore-forming pressure is between247x105Pa and608x105Pa, take it as275x105Pa/km and work out that the estimated depth of the static rocks is between0.9to2.2km which makes it a hypabyssal environment. The oxygen and hydrogen isotope feature shows that5D (smow) values around-30.3～-83.1, and δ180(smow) is between-2.93and+16.94, whereas818O (H2O) locates within the radius of -5.19and+7.25; hence the ore-forming fluid is mainly originated from atmospheric rainfalls blended with a small amount of mixed acid fluid from magmatic water.(4) Source bed of ore deposits is YiFeng fine blue sandy basalt (rock) group-quartz keratophyre series in the research area; Caledonian period magmatic rocks; Late Devonian-Early Carboniferous five-group, Huashan Ling group and Wu Fang group. The main part of ore-forming fluid is atmospheric precipitation, fluid mixed by magmatic water and building water is complementary. Ore storage space under the Yanshan orogenic continental activation (partial extension) and other tectonic formation also superimposed pre-formed small folds and layers break while they are formed in the vicinity of a series of intensive, network and micro-fracture zone for ore-controlling structure of the Lord. Hydrothermal power is Yanshanian period magmatic rocks.(5) The gold in the investigated region majorly moved as gold-sulfur complexes in the mode of AuHS and [Au(HS)2]-, precipitation enrichment consequently occurred in the wall-rocks near the low-pressured and oxidant fracture zones which had been developed in the dense fissure and micro-fracture zones. Finally, fillings and metasomatisms happened along the junctions of favorable structures, a gold deposit of stratiform, quasi-stratiform and lenticular then developed and gradually grew into the west of Jiangxi Province Carlin-type Gold Deposit. The west of Jiangxi Province Carlin-type Deposit is mainly located in the northwest of Jiangxi Province, which covers Yichun, Pingxiang, and Xinyu.