塔里木盆地顺南4井中硅化热液的地质与地球化学特征  

Geological and geochemical characteristics of silicified hydrothermal fluids in Well Shunnan 4,Tarim Basin

作　　者：李映涛[1,2] 叶宁[1,2] 袁晓宇[3] 黄擎宇[4] 苏炳睿[5] 周瑞琦[6] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [2]成都理工大学能源学院,四川成都610059 [3]中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214151 [4]中国石油勘探开发研究院,北京100083 [5]成都理工大学沉积地质研究院,四川成都610059 [6]四川省煤田地质工程勘察设计研究院,四川成都610059

出　　处：《石油与天然气地质》2015年第6期934-944,共11页Oil & Gas Geology

基　　金：中国石化西北油田分公司项目(3440008-14-ZC0607-0023)

摘　　要：塔里木盆地顺南4井奥陶系鹰山组灰岩取心段中发现有明显的热液蚀变现象和交代硅化特征,溶蚀缝洞、疏松硅质灰岩/硅质岩、热液脉体以及粗大石英晶簇异常发育。通过对取心岩样的地质特征观察,针对热液脉体（方解石脉和石英脉）以及硅质岩样品进行了系统采样,用来进行包裹体测温与测盐、稀土元素和微量元素分析。结果表明,热液流体具有混合性质,由岩浆活动提供热源,地层水提供主要的流体来源,岩浆热液与地层卤水混合后形成了中-低温、高盐度的硅化热液。稀土元素（REE）分析显示,铕异常δEu值为0.040~0.118,平均值为0.069,呈强烈负异常,指示了还原的成岩环境。Sm/Nd值为0.169~0.256,平均值只有0.194,可见成岩流体应该属于壳源流体。样品REE平均值配分曲线与地壳REE配分曲线趋势高度相似,表明热源来自壳源岩浆,且从其贫Mg2＋的特征来看属于上地壳（硅铝层）。微量元素特征中Ba/Sr值为0.43~19.76,平均值为6.70,变化范围较大,亦反应出流体的相对复杂性,U/Th值为0.35~4.76,平均值为2.14,Th/U值为0.21~2.88,平均值为1.03,Th/U-Y/Ho的相关性均显示硅化热液属于低温型热液。Cores from the Ordovician Yingshan Formation limestone in the of Well Shunnan 4 of the Tarim Basin show remarkable signs of hydrothermal alteration and metasomatism of silicon. Dissolved fracture-cavity,loose siliceous limestone / siliceous rock,hydrothermal veins and large quartz crystal cluster were abnormally developed. Observation of geological characteristics of the samples and analyses of fluid inclusion / rare earth elements and trace element,all suggested a mixed origin of the thermal fluids. It is believed that igneous activities provided energy and volcanic thermal fluid together with formation water formed a mixture of low-to-medium temperature and high salinity silicified hydrothermal fluid. REE analyses reveal that δEu values range from 0. 040 to 0. 118 and average 0. 069-negative anomaly that indicates a reductive environments; Sm / Nd ratios range between 0. 169 and 0. 256 and average 0. 194,indicating a crustal diagenetic fluids. The high similarity between the average REE distribution curve of samples and those of earth＇s crust suggests the origin of heat from magma,and to be more specific,the upper crust as indicated by a lack of Mg2 ＋in the samples. Ba / Sr values range from 0. 43 to 19. 76 and average 6. 70. Such a wide variation means the relative complexity of the fluid. U / Th ratios range from 0. 35 to 4. 76 and average 2. 14. Th / U ratios range from 0. 21 to 2. 88 and average1. 03. And Th / U-Y / Ho correlations all indicate that the fluid is of low-temperature type.

关 键 词：微量元素 稀土元素 硅化热液 流体包裹体 硅质岩 顺南地区 塔里木盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]