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

发布时间：2018-07-08 19:04

本文选题：深水 + 碳酸盐岩　；参考：《古地理学报》2016年01期

【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Si O2、Al2O3、Mg、Mn、Fe、Mn O和Ti O2;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。
[Abstract]:Deep-water carbonate rocks and their dolomitization in the Middle and Upper Ordovician Chaoke Group in the northeastern part of Tarim Basin are one of the special sedimentary and diagenetic types. The sedimentology, petrology and geochemistry of the Nanyaldang Mountain profile are illustrated by detailed observation and sampling analysis. The top and bottom carbonate rocks are associated with turbidite and are distributed in the form of gravity slippage and zonal distribution. It is mainly composed of yellowish-gray, mostly dolomite mud-intercalated shales, spongy bone needle, plankton fossils such as trilobites, poorly sorted granite, volcanic rocks and siliceous rocks, etc. The characteristics of solution and horizontal bedding in the original sediments are basically preserved. The dolomite consists of 9 types of dolomite, such as argillaceous dolomite, fine-grained dolomite or residual continental dolomite, giant algal oolitic dolomite and dolomitic dolomite. The orderliness of dolomite is 0.470.56 and 0.70 ~ 0.76, with medium and strong cathodic luminescence. It has experienced two periods of strong dolomization, rich in Sio _ 2, Al _ 2O _ 3, MgMn _ 2O _ 3, Fe _ (mn) O and Ti _ 2O _ 2, 未 ~ (34) SV-CDT = -0.2N ~ (-6), 危 REE = 46.7 脳 10 ~ (-6) ~ 67.4 脳 10 ~ (-6), positive europium and negative cerium "cap" rare earth distribution pattern, which reflects the relative reductive sedimentary environment. The content of Na _ 2O _ K _ 2O _ 3 Sr _ 2O _ 3 Sr _ (18) Sr _ (86) Sr is relatively high, and 未 _ (18) OPDB and 未 ~ (13) CPDB are slightly lower, which can not indicate the original seawater or primordial environment. Based on the above analysis, it is concluded that the deep-water carbonate rocks were formed in the upward shallower gentle slope zone, which occurred in the second period of dolomitization under the conditions of medium-deep burial, and was subjected to tectonic nappe or gravity sliding to the outer shelf. Fissure-dissolution and dolomite, calcite and hydrocarbon filling occurred.
【作者单位】：中国石化勘探开发研究院无锡石油地质研究所;中国石化西南分公司石油勘探开发研究院;
【基金】：“973”项目(编号:2005CB422100;2012CB214802) 国家科技重大专项(编号:2011ZX05005-002;2011ZX05008-003)联合资助~~
【分类号】：P534.42;P588.2

【参考文献】