川东南新元古界南华系大塘坡组页岩气勘探潜力分析

针对南华系大塘坡组页岩的厚度和分布范围、有机地化特征、矿物成分和页岩物性以及页岩的吸附性做了分析研究。该地区大塘坡组分布范围较广,评价区内厚度多大于100 m;分析证明页岩的有机质主要为Ⅰ型干酪根,原始有机碳含量多为1.00%左右,属于较好烃源岩。由于地质演化程度高,有机质已经达到高过成熟阶段。页岩的脆性矿物成分含量较高,孔渗特性较好,页岩的吸附特性较好,有利于页岩气的储集。总结相关参数的分析大塘坡组页岩具有较好的页岩气勘探前景。     

Carbon and sulfur isotopic compositions of basal Datangpo Formation, northeastern Guizhou, South China: implications for depositional environment

Isotopic compositions of Mn-carbonate and organic carbon from the same individual samples and sulfur isotopic compositions of pyrites in the basal Datangpo Formation were analyzed. Highly ³⁴S-enriched pyrites (δ³⁴34S_pyrite =31.7‰—59.4‰) were precipitated in relatively occlusive pore water under anoxic condition in sediments, which is consistent with the observation of large and scattered pyrite framboids. The sulfidic deep ocean was not “oxidized” in the early Datangpo interglacial interval, thus the level of seawater sulfate remained low and marine δ³⁴34S_sulphate remained high. Low δ¹³C_car (average -7.4‰) and abnormal relationship between δ¹³13C_car and fractionation (?_car-org) imply that the negative δ¹³C_car excursion may have resulted from oxidation of part of a large organic carbon reservoir. High ? car-org (average 25.1‰) implicates high CO₂ level in the atmosphere. Small standard deviation (1.0‰) of ??sup>??C_car values indicates the Mn-carbonate was precipitated near the water-sediment interface rather than in occlusive pore water in sediments under dysoxic conditions.     

铜仁-松桃地区南华系大塘坡式锰矿地质特征及成矿规律探讨

贵州省东北部铜仁-松桃地区是我国南方南华纪大塘坡期锰矿的重要集中区,随着近年一系列大型-超大型锰矿床的发现,该地区逐渐成为地质研究和找矿的热点。在贵州省锰矿资源潜力评价（2012年）工作取得的成果基础上,选取铜仁-松桃地区大塘坡式锰矿为例,分析了锰矿床形成的控制和影响因素,并重点对锰质来源和锰的矿化过程进行了分析和论述。研究表明,古构造决定了聚锰盆地的形态、大小及规模等,控制锰矿的形成;成矿期岩相古地理对锰矿的形成具有重要影响,海岸相区-海湾相最有利于形成大规模优质锰矿,浅海陆棚内盆地亚相其次,陆棚平原亚相内则基本不产锰矿。基于前人对大塘坡式锰矿成矿物质来源的不同观点,认为锰质具有深源特征,锰质是通过海底火山喷发引起的热液喷流沉积或者深大断裂热卤水循环方式运移,与大气圈中CO2或海底渗漏的天然气水合物（冷泉）结合沉淀成矿。在上述分析基础上,总结了区内找矿的主要标志及预测要素,给出了9个最小最优选区。     

渝东南秀山酉阳地区南华系沉积环境初步研究

在重庆市东南部,南华系只分布在秀山县和酉阳县,可细分为3个组:南沱组、大塘坡组和千子门组。其中南沱组和千子门组为冰碛层,沉积环境为底磧相、冰内河道相、冰前冰河相、冰前海湾泻湖相和冰前滨海相;大塘坡组为海湾泻湖相沉积,形成了大型锰矿床。区内南华纪气候具备典型的三段式结构特征:上、下两个冰期,中间夹一个间冰期,亦即南沱冰期、大塘坡间冰期和千子门冰期。     

Carbon and sulfur isotopic compositions of basal Datangpo Formation, northeastern Guizhou, South China: implications for depositional environment

Isotopic compositions of Mn-carbonate and organic carbon from the same individual samples and sulfur isotopic compositions of pyrites in the basal Datangpo Formation were analyzed. Highly 34S-enriched pyrites （834Spyrite =31.7-59.4‰） were precipitated in rel- atively occlusive pore water under anoxic condition in sediments, which is consistent with the observation of large and scattered pyrite framboids. The sulfidic deep ocean was not ＂oxidized＂ in the early Datangpo interglacial interval, thus the level of seawater sulfate remained low and marine δ34Ssulphate remained high. Low δ13Ccar （average -7.4‰） and abnormal relationship between δ13Ccar and fractionation （ΔCar-ors） imply that the negative δ13CCar excursion may have resulted from oxidation of part of a large organic carbon reservoir. High Δcar-org （average 25.1‰） implicates high CO2 level in the atmosphere. Small standard deviation （1.0‰） of δ13CCar values indicates the Mn-carbonate was precipitated near the water-sediment interface under dysoxic conditions rather than in occlusive pore water in sediments.