Metallogeneses and Their Geodynamic Settings Related to Mesozoic Granitoids in the Nanling Range
Affected by the compressive stress from the Indo-China Peninsula, the Indosinian Orogenesis, characterized by collision, thrust and uplifting, took place inside the South China plate the Indosinian granitoids in the Nanling Range and vicinity areas are mostly of during 250 -230 Ma. The ages of 240 -205 Ma, indicating that they were emplaced in both syn-collision and post-collision geodynamic settings. No important granite-related metallogeneses occurred in this duration. A post-orogeny setting started from the beginning of the Yanshanian Period, which controlled the large-scale granitic magmatism and related metallogeneses. This paper makes the first attempt to divide the Yanshanian Period into three sub-periods, i.e. the Early, Middle and Late Yanshanian Periods, based on the metallogenic features of granitoids and their geodynamic backgrounds. The magmatic association of the Early Yanshanian Period （about 185 - 170 Ma）comprises four categories of magmafism, i. e. basalt, bimodal volcanics, A-type granite, and the intra-plate high-K calc-alkaline, which indicates the beginning of extensionthinning of lithosphere and upwelling of mantle material in a relative small and local extent. Pb-Zn, Cu, and Au mineralization associated with high-K calc-alkaline magmatism represents the metallogeny of this period. During the Middle Yanshanian Period, lithospheric extending-thinning developed more widely and intensively, and hence the mantle upwelling and basaltic magma underplating, which caused the formation of great amount of crust re-melting granitoids. This period can further be divided into two stages. The first stage （ 170 - 150 Ma） is represented by large-scale emplacement of crust re-melting granites with some tungsten mineralization at the end. The second stage （ 150 - 140 Ma） is the most important time of large-scale mineralizations of non-ferrous and rare metals, e.g. W, Sn, Nb-Ta, Bi, Mo, Be, in the Nanling Range area, although much less granitoid developed. The Late Yanshanian Period （140 -65 Ma） was generally characterized by full extension and breakup of the lithosphere of South China. However, owing to the influence of Pacific plate movement, the eastern part of South China was predominated by subduction-related compression, which resulted in magmatism of calc-alkaline and shoshonite series and related metallogeneses of Au, Ag, Pb-Zn, Cu, （Mo, Sn） , followed by extension in late stage. In the Nanling Range area, Late Yanshanian magmatism was represented by emplacement of granitic volcanic-intrusive complexes which were genetically related to volcanic-type uranium and porphyry type tin deposits, as well as mafic dykes which caused the mobilization, transportation and mineralization of uranium in pre-existing Indosinian granites.
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