Discovery and Significance of Carbonate Mud Mounds from Cu-polymetallic Deposits in the Middle and Lower Yangtze Metallogenic Belt: Examples from the Wushan and Dongguashan Deposits
Discovery and Significance of Carbonate Mud Mounds from Cu-polymetallic Deposits in the Middle and Lower Yangtze Metallogenic Belt: Examples from the Wushan and Dongguashan Deposits
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发表时间：
2011
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通讯作者：
Jiang Shaoyong
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作者：
Jiang Shaoyong
长江中下游成矿带的武山、冬瓜山铜矿床中产出层状硫化物矿体，在层状硫化物矿体中发现了典型的环状或层状结构，通过对矿石样品的薄片显微观察、碳氧同位素分析和扫描电镜观察，发现层状硫化物矿体中存在着典型的环状或层状结构。提出该类硫化矿属于碳酸盐岩泥丘矿化类型，其宏观结构与典型碳酸盐岩泥土丘孔洞系统十分相似，以往的研究表明，碳酸盐泥丘一般发育在水深比台地深的斜坡环境中，碳酸盐泥丘的出现与海-水关系密切。两个铜矿床的碳酸盐泥土丘保存条件不同，冬瓜山铜存款保存了大量原生喷流沉积结构，发现细菌构造，碳氧同位素组成显示原生沉积特征，而武山铜存款则表现为热液蚀变/叠印结构，至今未发现细菌构造，碳氧同位素组成也显示了热液改造作用。综上所述，巫山和冬瓜山铜矿中碳酸盐泥土丘构造硫化物矿的发现，为海西期沉积热液作用提供了新的证据。下扬子成矿带的喷流成矿作用。
Bedded sulfide orebodies occur in the Wushan and Dongguashan Cu deposits in the Middle and Lower Yangtze mineralization belt.In this study,we found a typical circular or laminated texture in the bedded sulfide ores.Based on microscopic observation of thin sections of the ore samples,carbon and oxygen isotopic analysis,and scanning electron microscope (SEM) observation,we suggested that this type of sulfide ores belongs to a mineralized kind of carbonate mud mound.The macroscopic structures of these sulfide ores are quite similar to those of cavities system of typical carbonate mud mounds,and there are also bacteria structures found in some of the ore samples with SEM analysis.Previous studies show that the carbonate mud mound generally develops in a slope setting with water depth deeper than platform.It is also shown that the occurrence of carbonate mud mound has a close relationship with sea-floor hydrothermal exhalative ore-forming processes.The conservation conditions of the carbonate mud mounds in the two copper deposits are different,in the Dongguashan Cu deposit a lot of primary exhalative sedimentary textures are preserved,bacteria structures are found,and the carbon-oxygen isotopic compositions show primary sedimentary characteristics,while those in the Wushan Cu deposit show hydrothermal altered/overprinted textures,and no bacteria structures have been found so far,the carbon-oxygen isotopic compositions also indicate a hydrothermal reworking.In summary,the discoveries of carbonate mud mounds structure sulfide ores in the Wushan and Dongguashan Cu deposits provide new evidence for the Hercynian sedimentary hydrothermal-exhalative mineralization in the Middle and Lower Yangtze metallogenic belt.