| 铜官山铜矿床的组合特征及成因 |
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| 引用本文：.1985.The origin and the geological assemblage feature of the Tonggunshan copper deposit[J].Mineral Deposits,4(2):13~22 |
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| The origin and the geological assemblage feature of the Tonggunshan copper deposit |
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| Abstract:The Tounggunshan copper Deposit is one of the well-kn(wn deposit on the lower-middle Yangtze copper and iron metallogenic belt. Acctrding to its occurfence, association and alteration, the deposit can be subdivided into three types of mineralization: The upper mineralization, occurring at the upper part of the contact zone between the limestone and the intrusive body, is regarded as a conventional skarn deposit. The middle mineralization, which occurs in the strata and forms the main part of the deposit. shows stratabound nature. Ores in this part are laminated, banded, colloform, and framboidal in structure, and mineralization shows a horizontal zoning in order of magnetite-pyrrhotite-pyrite-kappa-pyrite from the contact zone outward. Of them, pyrite, especially kappa-pyrite, is the primary product formed in the early stage of sedimentation or diagenesis, and magnetite and pyrrhotite are products of metamorphism and hydrothermal alteration. Magnetite and pyrrhotite show fabrics similar to pyrite, and the postmagmatic hydrothermal-derived magnetite and pyrite can also be observed in the contact zone. There are therefore two sorts of magnetite-pyrite series in the deposit, which are discussed in the paper in terms of such aspects as shapes, hardness, cell parameters, major and minor elements, and sulfur and oxygen isotopes. Chalcopyrite is mainly of hydrothermal origin. The lower mineralization is present in hornfels near the contact zone and the periphery of the intrusive body in the form of disseminated and network ores subjected to biotitization with pyrite, chalcopyrite and sphalerite as the major metallic minerals. Pyrite is rich in Co and Ni with Co/Ni ratio>1 and S/$e ratio about 15000, showing the character of magmatie activity. This part, Therefore, is named quartz-vein deposit. The whole deposit is characterized by “three in one” assemblage, i. e., the deposit is primarily controlled by stratigraphy, especially the original sedimentation, while magmatism has also made a great contribution to the mineralization. The formation of the ore deposit can be divided into several stages, sedimentation-diagenesis, contact metamorphism and postmagmatic hydrother real superposition. During the first stage, the sedimentary pyrite was deposited in a favorable weak hydrodynamic condition as well as in a relatively stable tidal-flat depression, framboidal pyrite was a characteristic product at early diagenesis, and siderite or hematite might also have been deposited at the oxidized environment. During the main stage of mineralization-contact metamorphism and post-magmatie hydrothermal superposition, the quartz-diorite intrusion resulted in the contact metamorphism and the transformation of the kappa-pyrite into pyrite, pyrrhotite and magnetite in accordance with the distance from the igneous body. Finally, the superposition of ore-bearing hydzothermal fluids was accompanied by skarnization and other alterations. According to the characteristics of the main mineralization (the middle ore body), the deposit is termed a strtabound skarn deposit. In this paper its genetic model is illustrated and the main problems concerned are discussed. |
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