The Evolutionary History of Ore-forming Processes of Metallic Ore Deposits in Northern Guangxi

The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late timesfin the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.

Analysis of Mineralization System and Prediction of New-Type Ore Deposits

The discovery of new-type ore deposits, an important approach to guarantee the mineral resources supply in the 21st century, often brings about a gigantic increase in the mineral resources reserves. The analysis of mineralization system is of great importance to the discovery of new type ore deposits. ① The understanding of the relationship among various ore deposit types within a mineralization system in a region can help us to locate the unknown ore deposit types from the known ore deposit types, evidence that has been proved in the mineral prospecting history of ore belts in the middle and lower reaches of the Yangtze River, China. ② The understanding of the spatial structure of a mineralization system, especially of the vertical zonation, is helpful for the discovery of the concealed ore deposit types. ③ Clarifying the temporal structure of a mineralization system, including the iteration relationship between the mineral deposit types in the mineralization, leads to the location of the missing mineralization chains from the known mineralization chains (mineral deposit type), a method often proved to be effective in the magmatic hydrothermal mineralization system.④ Clarifying the factors restraining the diversity of mineral deposit types in mineralization system leads to the discovery of the potential of new type mineral deposits in relevant region. ⑤ Studying new mineralization setting and new ore forming processes leads to discovery of new type mineral deposit. More probabilities of discovery of new type mineral deposits are present in biogenic mineralization system, deep sea mineralization system, low temperature mineralization system, tectonic mineralization system and superimposed mineralization system.

Shear Alteration, Mass Transfer and Gold Mineralization: An Example from Jiaodong Ore Deposit Concentrating Area, Shandong, China

Taking the gold ore deposit concentrating area of Jiaodong area in Shandong, China for an example, based on geological analysis, and applying Gresens’ equation, Grant’s isocon diagram and O’hara microelement calculation method, a thorough study on shear alteration, mass transfer and gold mineralization was carried out. The authors also made mathematic simulation and geochemical analysis. The work reveals temporal spatial changing regularities of temperature field and velocity field of fluids, and also reveals fluid transport chemical reaction coupling metallogenic dynamics of the Jiaojia gold ore concentrating area. During shear alteration process of the Jiaodong gold ore concentrating area, all kinds of components transferred with different amounts, fluid rock ratio was rather high and volume strain was of dilation type. Fast flow of ore forming fluid favors the occurrence of mixed fluid. Shear fractured zones are places where there was strong transportation reaction coupling mineralization. Ore bodies were located in dilation space of shear structure where there was the greatest fluid flux. After the emplacement of the rock body, a convex heat field was formed around the rock body. It is one of the main metallogenic forces. The major reason for mineralization is the mobilization, migration and enrichment of ore forming elements induced by shear compressive extensional tectonism. Inclusion gold dominant low grade ores were formed in the early ore forming stage, while high grade ores, which contained fissure gold and polymetallic veinlets, were formed in late ore forming stage.