摘要
柴达木盆地北缘构造带平台地区下干柴沟组下段主要发育河流相碎屑岩沉积,通过对钻井岩心样品中主微量元素分析测试,结果表明:下干柴沟组下段中稀土元素总含量(∑REE)分布在125.96~169.91μg/g之间,平均值为151.11μg/g;(La/Yb)_N值在8.99~11.29之间,平均为9.91;(La/Sm)_N值分布在3.42~4.10之间,平均为3.80;(Gd/Yb)_N值分布在1.51~2.25之间,平均为1.73;总体上表现为轻稀土元素富集,重稀土元素亏损,且Eu负异常的特征。Ceanom异常指数与La_n/Yb_n值表明当时沉积水体为氧化环境且沉积速率较快;重矿物组合以石榴石、磁铁矿、锆石、白钛矿和绿帘石为主,含少量电气石、榍石和角闪石。稀土元素和重矿物分析结果表明平台地区下干柴沟组下段沉积物源区岩性以花岗岩和沉积岩为主,少量来自碱性玄武岩。构造背景以大陆岛弧环境为主,通过对比周缘老山的构造背景及基岩类型,认为其沉积物源主要来自塞什腾山西段。上述研究为平台地区沉积体系的精细划分和寻找有利储层砂体提供了地质依据。
Fluvial facies clastic rocks are mainly developed in the lower part of the Lower section of Xiaganchaigou Formation of Paleogene in the tectonic belt platform area in the northern margin of Qaidam Basin.By analyzing and testing the main trace elements in the drilling core samples of the Lower section of Xiaganchaigou Formation,the results showed that the total content of rare earth elements(∑REE)was between 125.96μg/g and 169.91μg/g,with an average value of 151.11μg/g.(La/Yb)_N value ranged from 8.99 to 11.29,with an average of 9.91.(La/Sm)Nvalue ranged from 3.42 to 4.10,with an average of 3.80.(Gd/Yb)_N value ranges from 1.51 to 2.25,with an average of 1.73.On the whole,it is characterized by enrichment of light rare earth elements,loss of heavy rare earth elements,and negative anomaly of Eu.Ceanom anomaly index and(La/Yb)_n value indicate that the sedimentary water at that time is in an oxidizing environment with a faster deposition rate.The heavy mineral combination is dominated by garnet,magnetite,zircon,titanite and porphyry,and contains a small amount of tourmaline,sphene and amphibolyte.The analysis results of rare earth elements and heavy minerals show that the lithology of the lower sedimentary source area of Lower section of Xiaganchaigou Formation in the platform area is mainly granite and sedimentary rock,and a small amount comes from alkaline basalt.The tectonic setting of the study area is dominated by the continental island arc environment.By comparing the tectonic setting and bedrock types of the surrounding Laoshan,it is believed that the sediment source is mainly from the western section of Seshiteng Mountain.This study provides a geological basis for the fine division of sedimentary system and the search for favorable reservoir sand bodies in the platform area.
作者
蒋赟
潘世乐
秦彩虹
蒋峥文
朱文军
张明峰
孙国强
JIANG Yun;PAN Shi-le;QIN Cai-hong;JIANG Zheng-wen;ZHU Wen-jun;ZHANG Ming-feng;SUN Guo-qiang(Northvest Institute of Ecor Environmental Resources,Chinese Academy of Sciences.Lanzhou 730000,China;Universily of Chinese Academy of Sciences,Bejing 100049,China;Explorution and Development Research Instiute of PetroC hina Qinghai Oilfield Company,Dunhuang 736202.China;Gunsu Prowincial Key Laboralory of Oil and Gus Resources Research,Lanzhou 730000,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2020年第11期1537-1547,共11页
Natural Gas Geoscience
基金
甘肃省自然科学基金(编号:17JR5RA293)
甘肃省重点实验室专项(编号:1309RTSA041)联合资助。
关键词
稀土元素
重矿物
下干柴沟组下段
平台地区
柴达木盆地
Rare earth element
Heavy mineral
Lower section of Xiaganchaigou Formation
Platform area
Qaidam Basin
