Coupling mechanism of mineralization and hydrocarbon-forming in hydrothermal convection system: An example from Longtoushan Sn-polymetal deposit, Dachang |
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Authors: | Yang Bin Peng Sheng-lin Yang Mu Zhang Qi-zuan |
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Affiliation: | (1) Institute of Geosciences and Environmental Engineering, Central South University, 410083 Changsha, China;(2) China University of Geoscience, 100083 Beijing, China |
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Abstract: | Longtoushan Sn-polymetal deposit is a large-scale deposit of high-tenor. The ore-bodies occur in reef limestone of middle Devonian. There is much anthraxolite in reef limestone and ore-bodies. The anthraxolite is the postmature result of oil-gas’ thermal metamorphism. The close relationship of anthraxolite and Sn-polymetal deposit reveals the space-time relation between oil-gas evolution and Sn-polymetal mineralization. Sulfur isotope of Longtoushan deposit is close to oil’s sulfur in Devonian, which indicates obvious relationship between the sulfur’s source of deposit and oil-gas’ activity. The forming of Longtoushan deposit relates to exhalative-sedimentary mineralization in Devonian. Because of the favorable hydrocarbon-forming condition of Longtoushan reef and surrounding basin facies’ black shale and peat, coupling of ore-formation and hydrocarbon-forming occurs in seabed’s hydrothermal convection. The distributing of ore-forming elements indicates the presence of hydrothermal convection system. The thermal fluid containing organic matters conduces to Sn-polymetal elements’ activation and transfer, and provides catalyzing condition to the transforming from SO 4 2− to S2−. The erosion action of brine containing organic acid to reef limestone induces the growing of crannies and karst’s caverns, which provides advantageous space to Sn-polymetal mineralization. The heat source of mineralization provides thermocatalysis condition to hydrocarbon-forming. When the circulatory fluid containing oil-gas enters the high-temperature region(>150°C), the oil-gas is decomposed and anthraxolite comes into being. Foundation item: Project(20030533012) supported by Specialized Research Fund for the Doctoral Program of Higher Education |
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Keywords: | coupling mechanism of mineralization and hydrocarbon-forming hydrothermal convection Sn-polymetal deposit Longtoushan |
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