| 山东三山岛金矿床形成物理化学条件研究 |
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| 引用本文：.1985.The physicochemical condition for the formation of Sanshan Island gold deposit[J].Mineral Deposits,4(4):35~46 |
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| 基金项目:中国科学院科学基金 |
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| The physicochemical condition for the formation of Sanshan Island gold deposit |
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| Abstract:The gold deposits located in the west of the Jiaodong Peninsula occur mostly in Zhaoyuan and the north of Yexian, which constitute the Zhaoyuan-Yexian gold mineralization zone. The Sanshan Island gold deposit is a part of this mineralization zone. The formation of the deposits was closely related to the intrusion of the Linglong granitic body distributed in the district. The Linglong and Guojiaoling granitic bodies related to the formation of the gold deposits in the region were formed as a result of the polygenetic processes, mostly by the intrusion of the granitic magma due to the melting of the Jiaodong Group and partly by the metasomatism caused by regional migmatization. The melting inclusions formed under the temperature range from 780℃ to 940℃ have been found in the Linglong granite during this study. It shows that in this district the granite is of magmatic origin. During the formation of the granite, the local differentiation could have occurred in the magma. With the falling of the temperature of the magma, the rock-forming minerals were crystallized, the aqueous solutions were separated from the melt, the differentiated intergranular solutions could replace the rock-forming minerals, and the massive sericite-quartz gold-bearing rock formed(the Sanshan Island gold mine). In the fracturing surroundings, the intergranular solutions could infiltrate through the cracks, fissures and fractured zones and, as a result, the gold-bearing fractured zones or vein gold deposits were formed(e. g., Jiaojia and Linglong Gold Mines). The altered rocks in Sanshan Island was formed at 280-420℃,which is close to the homogenization temperature(300-460℃) of the Gas-liquid inclusions in the quartz of the mother rocks. Moreover, the compositions of the liquid and trace gases in the inclusions of the two kinds of rocks are also similar. All of these facts reasonably indicate that in genesis, the deposits were formed as a result of metasomatosis by intergranular solutions of the granite in the district. In the altered rocks, there is a close correIationship between the intensities of the mineralization and the alteration. With the reducing of temperature and the intensification of the pyrite-sericite-quartz alteration, the gold content increases. The analyses of the ore-forming solutions show the characteristics of SO4-2>Dl-1>HCO3-1>F-1, K+/Na+1, and H2O>CO2>CH4,caused by potassium ions and weak acid in the gold-bearing pyrites-sericite-quartz altered rocks. Gold should be transported in the form of sulfur or chiorine complexes. Owing to the change in temperature, pressure and the fugacity of oxygen in the environment, the complexes could be decomposed and as a result, natural gold was separated out and deposited in the ore. The source of the ore-forming materials of the gold deposits in the district must have been closely related to the Jiaodong Group, whose gold content is decades times higher than that of normal metamorphic rocks．During the formation of the granite through the melting of the gold-bearing metamorphic rocks, gold should be mobilized and transferred into the granite and then be further concentrated in the deposits by the action of the intergranular solutions. The metallogenie elements, therefore, must have mostly come from old basement metamorphic rocks, and Jiaodong Group could be regarded asthe source beds of gold. Besides, the ore-forming solutions had a close relationship with the intargranular solutions. |
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