| 塔里木盆地东北部中上奥陶统却尔却克群深水碳酸盐岩及白云岩化* |
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| 引用本文： | 钱一雄,张克银,陈跃,陈强路,田蜜,尤东华,罗宇.塔里木盆地东北部中上奥陶统却尔却克群深水碳酸盐岩及白云岩化*[J].古地理学报,2016,18(1):21-38. |
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| 作者姓名： | 钱一雄 张克银 陈跃 陈强路 田蜜 尤东华 罗宇 |
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| 作者单位： | 1.中国石化勘探开发研究院无锡石油地质研究所,江苏无锡 214126;2.中国石化西南分公司石油勘探开发研究院,四川成都 610081 |
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| 基金项目： | *“973”项目(编号:2005CB422100,2012CB214802)与国家科技重大专项(编号:2011ZX05005-002,2011ZX05008-003)联合资助 |
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| 摘 要： | 塔里木盆地东北部库鲁克塔格中上奥陶统却尔却克群中的深水碳酸盐岩及其白云岩化是较为特殊的沉积与成岩作用类型之一。通过对南雅尔当山剖面详细观察与采样分析,阐明了其沉积学、岩石学及地球化学特征:深水碳酸盐岩的顶、底均与浊积岩伴生,呈重力滑覆-带状分布,主要由黄灰色-灰色、大多呈薄层瘤状的白云岩夹泥页岩构成;可见到海绵骨针、三叶虫等浮游生物化石以及分选差的花岗岩、火山岩及硅质岩等碎屑;基本保留了原始沉积中的溶解、水平层理等较深水沉积的特征。该套白云岩包括泥粉晶白云岩、细晶白云岩或残余陆屑白云岩、巨型藻鲕白云岩和生屑泥粉晶白云岩等9类白云岩;白云石有序度为0.47~0.56和0.70~0.76,中强阴极发光,经历了2期较强的白云岩化作用;富含SiO2、Al2O3、Mg、Mn、Fe、MnO和TiO2;δ34SV-CDT为-0.2~6.6,ΣREE含量为46.7×10-6~67.4×10-6,呈正铕负铈的“帽式”稀土配分模式,反映相对还原沉积环境;反映沉积水体盐度的Na2O+K2O、Sr、Ba含量偏低, 87Sr/86Sr 值相对偏高,δ18OPDB 、δ13CPDB稍低,不能指示原始海水或原始环境。综合上述分析结果认为:这套深水碳酸盐岩形成于向上变浅的缓坡带,其发生了浅埋藏、中-深埋藏条件下的2期白云岩化,且受构造推覆或重力滑覆至外陆棚,并发生裂隙-溶蚀作用和白云石、方解石及烃类的充填作用。
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| 关 键 词： | 深水 碳酸盐岩 白云岩化 地球化学 奥陶系 塔里木盆地 |
| 收稿时间： | 07 April 2015 |
Deep-water carbonate rocks and their dolomitization of the Middle and Upper Ordovician Queerquek Formation in northeastern Tarim Basin |
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| Qian Yixiong,Zhang Keyin,Chen Yue,Chen Qianglu,Tian Mi,You Donghua,Luo Yu.Deep-water carbonate rocks and their dolomitization of the Middle and Upper Ordovician Queerquek Formation in northeastern Tarim Basin[J].Journal of Palaeogeography,2016,18(1):21-38. |
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| Authors: | Qian Yixiong Zhang Keyin Chen Yue Chen Qianglu Tian Mi You Donghua Luo Yu |
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| Institution: | 1.Wuxi Institute,Exploration & Production Research Institute,SINOPEC,Wuxi 214126,Jiangsu;2.Exploration & Production Research Institute,Southwest Oil & Gas Company,SINOPEC,Chengdu 610081,Sichuan |
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| Abstract: | Deep-water carbonate rocks and its dolomitization of the Middle and Upper Ordovician Queerquek Formation in Kuluketage Mountain,northeastern Tarim Basin,is one of special types of deposition and diagenesis. By detailed observation and sampling of the Nanyaerdangshan section,we studied the sedimentary,petrological and geochemical features of the dolomitic beds. The deep-water carbonate rocks,which occurred in thrust-nappe or gravity-related sliding shapes in the stratigraphic column of the outcrop, is of yellow and dark grey,thin to medium bedding dolostone interbedded with mudstone,marl and shale,usually irregular and lenticle “knotty nodule”accompanied with turbidite of fine rocks debris either at the bottom or at the top. It is characterized by the planktonic faunas such as trilobite,siliceous sponge spicules and echinoderm fragments,and richness in poorly sorted terrigenous sediment attributed to grantite,volcanic and siliceous rocks. The carbonate rocks exhibited a certain rhythm structures such as dissolved-bedding,thin-horizontal bedding and few of algae laminae in primitive sediment. The main mineralogical peculiarities of dolostone composed of nine various types i.e.,near-micritic,giant ooids,fine-crystalline dolostone,bitumen-bearing algae poloid dolostone with residual bioclastics and silicification,and so on. The low and middle degree of order varies between 0.47-0.56 and 0.70-0.76, with a medium and extensive cathodluminescence(CL),indicating two-episodes strong dolomitization. The carbonate rocks have the abundance of SiO2 and Al2O3, and richness of Mg、Mn、Fe、MnO and TiO2. The value of δ34SV-CDT(-0.2-6.6) and REE(46.7×10-6-67.4×10-6) are similar to the shale on the “cap-form”distribution pattern of rare earth elements with positive europium(δEu)and negative cerium(δCe), indicating a relative reduction deep-water environment. The salinity index such as Na2O+K2O,Sr and Sr/Ba, are rather low,compared with those of typical terrace carbonate rocks. Since the higher 87Sr/86Sr ratio of the dolostone with rather low values ofδ18OPDB δ13 CPDB,it can’t be interpreted as a typical of isotopic feature of coeval seawater. Therefore,the deep-water carbonate rocks were developed in a shallowing-up parts of gentle-slope, then suffered two-episodes dolomitization at shallow buried or middle and deep buried respectively,and finally were thrusted or gravities-slided into outer continental shelf or lower parts of slope,with dolomite and calcite, hydrocarbon fillings in dissolved-vugs-fractures. |
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| Keywords: | deep-water carbonate rocks dolomitization geochemistry Ordovician Tarim Basin |
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