重庆巫溪县文峰地区巴东组沉积特征及其铜矿化研究

发布时间：2018-12-06 20:13

【摘要】：研究区地处四川盆地东缘的大巴山东段南麓,构造单元主要隶属上扬子陆块米仓山-大巴山基底逆推带中的巫溪凹褶束。区内发现有多处砂岩型铜矿点及矿化点,含矿地层为三叠系中统巴东组,巴东组呈近东西向分布于塘坊-菱角及竹园-上磺一带。本文根据野外调查及实测地层剖面资料,通过对巴东组岩石特征、沉积构造及沉积环境的研究进行了地层划分对比及沉积相分析;同时,对产于巴东组二段内的铜矿(化)体特征、成矿地质条件和矿化成因进行了分析讨论,取得了以下几点认识:1、巴东组岩性以紫红色夹灰绿色中-薄层泥岩、钙质泥岩、粉砂质泥岩、泥质粉砂岩为主夹浅灰色泥灰岩,中部夹有灰色薄-中厚层状泥质灰岩、白云质灰岩、白云岩、泥灰岩及钙质页岩。巴东组沉积环境总体上属于障壁海岸相,根据其岩性组合特征可细分为四个岩性段。2、巴东组一段为泥岩、粉砂质泥岩、钙质泥岩的岩石组合,属障壁海岸相碎屑潮坪环境沉积。巴东组二段主要为紫红色厚层-块状含钙质结核粉砂质泥岩、紫红色中-薄层状粉砂质泥岩、钙质泥岩夹灰绿色中层细砂岩,属障壁海岸岛的碎屑潮坪相沉积。巴东组三段基本层序为:微晶灰岩→泥灰岩→钙质泥岩、白云岩→生物碎屑灰岩,属碳酸盐潮坪环境沉积。巴东组四段基本层序为钙质泥岩→白微晶白云岩,属泻湖亚相沉积。3、研究区发现的6处铜矿点或矿化点,其构造部位处于青龙包-菱角向斜的南翼或寨包-长梁子近东西向背斜构造的南翼,含矿地层均为三叠系巴东组二段,铜矿化层发育于此套地层中的灰绿色细砂岩、粉砂岩或泥质粉砂岩夹层中,矿化体呈似层状、不规则脉状、透镜状、鸡窝状顺层断续产出。矿化以铜为主,伴有银、钼等的富集。矿体厚0.35~4.10m,铜品位一般在0.94~5.08%之间;Ag含量主要在(2.5-7.9)×10-6之间,最高可达6500×10-6。Mo含量在(0.32-1.8)×10-6,最高可达400×10-6。矿石矿物呈薄膜状、细脉状沿裂隙断续分布。矿石自然类型有:①浅灰绿色细粒砂岩型铜矿石,矿物成分主要为孔雀石,少量辉铜矿;②灰-绿色泥质粉砂岩型铜矿石,矿物成分主要为为孔雀石,少量铜兰、辉铜矿及蓝铜矿;③浅灰色-翠绿色粉砂岩型铜矿石,主要矿物成分为孔雀石,次为铜兰、辉铜矿、斑铜矿、黝铜矿及黄铜矿。矿石中金属矿物成分分布不均匀,脉石矿物主要为石英、长石、方解石等。巴东组二段砂岩型铜矿,其富集的主要控制因素是地层和沉积环境,具有明显的层位特征;其次则与岩石性质及所发育的构造裂隙有关。具体表现在“灰绿色粉-细砂岩层”的厚度、范围、有机质含量及其构造裂隙的发育程度,是较为典型的层控型-热液叠加改造型铜矿。
[Abstract]:The study area is located at the southern foot of Daba Shandong section in the eastern margin of Sichuan Basin, and the tectonic unit is mainly belong to the Wuxi fold in the basement inversion belt of the upper Yangtze block. There are many sandstone-type copper deposits and mineralization sites in the area. The ore-bearing strata are the Padong formation of the Middle Triassic, and the Badong formation is distributed in the near east-west direction in the areas of Tangfang-Lingjiao and Zhuyuan-Shangmeng. Based on field investigation and measured stratigraphic profile data, stratigraphic division and correlation and sedimentary facies analysis are carried out on the basis of the study of the rock characteristics, sedimentary structure and sedimentary environment of Badong formation. At the same time, the characteristics, ore-forming geological conditions and mineralization genesis of copper ore bodies in the second member of the Badong formation are analyzed and discussed. The results are as follows: 1. The lithology of the Badong formation is grayish green and grayish green. Calcareous mudstone, silty mudstone, shaly siltstone are mainly intercalated with light gray marl, and in the middle there are gray thin-medium thick layer marlite, dolomite, marlite and calcareous shale. The sedimentary environment of Badong formation is generally a barrier coastal facies, which can be subdivided into four lithologic segments according to its lithologic assemblage. 2. The first member of Badong formation is composed of mudstone, silty mudstone and calcareous mudstone. It belongs to barrier coastal clastic tidal flat environment. The second member of Badong formation is mainly composed of fuchsia thick layer and massive calcareous nodule silty mudstone, purplish red medium-thin layer silty mudstone, calcareous mudstone intercalated with gray-green meso-fine sandstone, which belongs to clastic tidal flat facies deposit of barrier coast island. The basic sequence of the third member of Badong formation is: microcrystalline limestone, mudstone, calcareous mudstone, dolomite and bioclastic limestone, which belong to carbonate tidal flat environment. The basic sequence of the fourth member of the Badong formation is calcareous mudstone albinite microcrystalline dolomite, which belongs to lagoon subfacies deposition. Its structural position is located in the southern wing of Azure Dragon Bao-Diamond syncline or the southern wing of Zaibao-Changliangzi structure near the east-west anticline. The ore-bearing strata are all the second member of the Padong formation of the Triassic system. The copper mineralization strata are developed in the grey-green fine sandstone in this set of strata. In siltstone or argillaceous siltstone intercalation, the mineralized bodies are stratiform, irregular veins, lenticular and chicken nest. The mineralization is mainly copper, accompanied by the enrichment of silver and molybdenum. The ore body thickness is 0.35 ~ 4.10 m, and the copper grade is generally between 0.94 and 5.08%. The content of Ag is mainly between (2.5-7.9) 脳 10 ~ (-6), the highest content is 6500 脳 10-6.Mo (0.32-1.8) 脳 10 ~ (-6), and the highest is 400 脳 10 ~ (-6). The ore minerals are thin-film and veined along the fissures. The natural types of ore are as follows: 1 the mineral composition is mainly malachite and a small amount of chalcopyrite; (2) Grey-green argillaceous siltstone type copper ore, the mineral composition is mainly malachite, a small amount of copper blue, chalcopyrite and blue copper ore; The main mineral composition is malachite, followed by copper blue, chalcopyrite, pyrite, tetrahedrite and chalcopyrite. The distribution of metallic minerals in ores is uneven, and the gangue minerals are mainly quartz, feldspar, calcite and so on. The sandstone-type copper deposits in the second member of the Badong formation are mainly controlled by stratigraphic and sedimentary environments and have obvious stratigraphic characteristics, followed by lithologic properties and tectonic fractures developed in the second member of the Badong formation. The thickness, range, content of organic matter and the degree of development of structural fissures of "grey-green silt-fine sand strata" are typical strata-controlled and hydrothermal superimposed and reformed copper deposits.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.41

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