塔里木盆地牙哈—英买力地区寒武系—下奥陶统白云岩形成机理  

The Genetic Mechanism of Dolostones of the Cambrian-Lower Ordovician in Yaha-Yingmaili Region,Tarim Basin: dolomitization through deep buried hydrothermal fluid

作　　者：何莹[1] 鲍志东[2] 沈安江[3] 申银民[4] 李明和[4] 

机构地区：[1]中国石油化工股份公司西南分公司勘探开发研究院,成都610081 [2]中国石油大学资源与信息学院,北京昌平102249 [3]中国石油勘探开发研究院杭州地质研究所,杭州310023 [4]中国石油塔里木油田分公司勘探开发研究院,新疆库尔勒841000

出　　处：《沉积学报》2006年第6期806-818,共13页Acta Sedimentologica Sinica

摘　　要：根据铸体薄片鉴定、阴极发光显微镜观察、碳、氧稳定同位素测定、微量元素分析及包裹体测温等手段,对塔里木盆地牙哈—英买力地区寒武—下奥陶统深埋热液白云岩类型及成因机理进行了详细的研究。认为研究区深埋藏白云岩主要由细晶或中晶白云石组成,白云石呈自形或半自形晶。δ13CPDB值为-1.63‰~2.31‰,平均为0.25‰,δ18OPDB值为-11.49‰^-6.02‰,平均为-8.72‰;锶含量较低,在77×10-6~107×10-6之间,二价铁、锰含量较高,具有高的有序度和低的CaCO3摩尔含量的特点。各种资料表明,该类白云岩是在深埋藏环境中较高温度条件下形成的,白云岩的形成与海西期岩浆喷发活动有关,变质岩体的分布控制了白云岩的分布。白云化流体来自岩浆热液、变质热液、有机酸及区域地下热卤水的混合,白云化所需的Mg2+来自岩浆岩中铁镁矿物的分解、埋藏压实过程中粘土矿物的脱水作用等。因此其白云化机制可称之为“深埋热液白云化”。The types and genetic mechanism of the Cambrian-Lower Ordovician deep buried hydrothermal dolostones in Yaha -Yingmaili region, Tarim basin are investigated by means of stained thin section microscopic identification, cathodoluminescence microscopic observation, carbon and oxygen isotope geochemistry, trace element analysis, and fluid inclusion analysis. Deep buried dolostones in study areas mainly consist of fine or medium dolomites, which crystals are euhedral or subhedral. The δ13C is - 1.63‰ -2.31‰（PDB） and averages 0.25‰;δ180 is - 11.49‰ - 6.02‰（PDB） and averages - 8.72‰. The content of Sr is low, 77 × 10 ^-6 - 107× 10^-6, the content of Fe and Mn are high. The degree of order is high and the molar volume of CaCO3 is low. Various data show that these dolostones were formed under deep burial conditions, relatd to magmatic exhalation of Hercynian age. The distribution of dolostones is controlled by the distribution of metamorphic rock. The dolomitizing fluid was a mixture of magmatic hydrothermal, metamorphic hydrothermal, organic acid and regional brine under the ground. The Mg^2＋ for dolomitization came from dissolution of magmatic rock, dehydration of clay mineral in the course of buried compaction. Thus, the dolomitization mechanism in this area may be called ＂ dolomitization through deep buried hydrothermal＂.

关 键 词：塔里木盆地 寒武系-下奥陶统深埋热液白云岩 白云化作用 地球化学特征 成因机理 

分 类 号：P588.245[天文地球—岩石学]