Experimental Study On Hydrothermal Alteration Metasomatism Of Linglong-jiaojia-type Gold Deposits, Jiaodong

The gold deposit concentration zone in the Jiaodong Peninsula is one of the china's most important gold producing areas, where there is Linglong-Jiaojia type gold deposit which is the most typical gold deposits series combination relative to Mesozoic granite worldwide developed in Linglong and Jiaojia gold orefields. There are three ultra-large type gold deposits containing over 100 tons gold reserve and five gold deposits containing over 50 tons in the area, and in which the second gold concentrating zone in depth is being gradually uncovered with a huge exploration prospect. Therefore, the area is desperately in need of in-depth peripheral Metallogenic Regularity study. However, both little geochemical process study of structural ore-controlling physicochemical conditions and structural-hydrothermal metasomatic alteration and lack of theoretical study and experiments in tectonic-geochemical ore-forming mechanism seriously impede the arduous prospecting task in the future. This sort of works imperatively needs to be intensified. The author takes "Experimental research of hydrothermal alteration of Linglong-Jiaojia type gold deposit in Jiaodong Peninsula" as Master's dissertation topic, which may have important scientific significance and referential value for gold prospecting.As a graduate student, I had participated my tutor's six research projects such as Geological Survey Project research on basement structure and ore-transmitting-and-controlling essential in midstream and downstream of Changjiang River, Cross-cutting project Metallogenic regularity and deep peripheral forecasting of Linglong gold orefield in Zhaoyuan City, Shandong Province, etc., National Science Foundation Project Fluidic geochemistry and tectonic metallogenesis research of gold deposit in Northwest of Jiongdong Peninsula, and had completed inside and outside work of Stat Key Laboratory of Ore Deposit Geochemistry Project Tectonic physicochemical experiment research of Linglong-Jiaojia type gold deposit, and obtained abundant first-hand data. The dissertation is accomplished by reading relevant documents and analyzing them comprehensively, field measurement of geological profiles of typical gold deposits and carrying out hydrothermal metallogenic experiment for three months. The main progress the dissertation makes is as follow:1,We chose Linglong and Jiaojia orefields to carry out field work, and have researched tectonically rock-controlling and ore-controlling and diagenesis and metallogenesis rules, have measured typical geological profiles of two types of ore deposits, i.e. alteration type and quartz vein type, and have collected eight groups of samples 30 samples in total, all of which set a sound basis for indoor hydrothermal alteration experiment research.2,According to characteristics of metasomatic alteration of the deposits, hydrothermal alteration metasomatism metallogenic experiment was designed to conduct in NaCl and KCl solution systems respectively. A llaboratory at Institute of Geochemistry Chinese Academy of Science has the exerting differential stress device and hydrothermal controlling system, which can be accurately conducted tectonic-hydrothermal alteration experiment research.3,The texture and structure of the samples experimented have obvious variation in that substantial conjugate shear fractures develop and new minerals paralleling to fracture planes are common, and part of the minerals occurs synkinematic plastic deformation and tensile fractures, and in which broken grains migrate into new fractures in local region. This approves that rigid minerals tend to occur brittle deformation, while flexible ones tend to occur plastic deformation, and that tectonic deformation occurs synchronously with process of diagenesis and metallogenesis.4,In the 10% concentration of NaCl hydrothermal system, FeO and CaO compositions in quartz in the quartz-vein-type gold deposit decrease, NiO increase, and FeO decreases, CaO increases in the alteration rock type; average compositions of biotite, CaO, K2O and Na2O in potassic granite have also increased in different degree. In 10% KCl solution, FeO and CaO concentrations have obviously increased in the granite after experiment.5,What is most important is that under the hydrothermal process of NaCl solution, concentrations of FeO, MgO, K2O, Na2O, TiO2 and MnO of sericite in the sericite quartzite synergistically decrease, approving that sodium alteration plays a crucial role in the metallogenic elements transmission in sericite in gold deposit in Jiaodong Penuinsula. In contrast, potassic alteration has not obvious effect on separation of metallogenic elements. For instance, FeO and CaO concentrations in feldspar of granite have obvious increase yet after experiment.The experiment reveals that the geochemical cause of massive accumulation in gold deposits of Jiaodong Peninsula is that intensive sodium alteration developing in wide sericite quartzite alteration belt cause metallogenic elements to migrate in a large quantity, and the potassic alteration afterwards cause metallogenic elements to massively deposit and form deposit.