北羌塘盆地那底岗日剖面中上侏罗统碳酸盐岩稀土元素地球化学特征与沉积环境分析  

REE Geochemical Characteristics and Sedimentary Environment Analysis of the Middle-Upper Jurassic in the Nadi Kangri Area,North Qiangtang Basin

作　　者：冯兴雷[1] 付修根[1] 谭富文[1] 陈文彬[1] 

机构地区：[1]中国地质调查局成都地质矿产研究所,四川成都610082

出　　处：《新疆地质》2012年第2期210-215,共6页Xinjiang Geology

基　　金：国家油气专项:"青藏高原重点盆地油气资源战略调查与选区"(XQ-2009-1);国家自然科学基金项目(40702020);四川省青年科技基金(09ZQ026-006)联合资助

摘　　要：北羌塘盆地那底岗日剖面中上侏罗统碳酸盐岩发育,其中以布曲组和索瓦组最为发育,对研究该区中上侏罗统沉积环境具重要意义。通过对稀土元素分布规律、分布特征及地球化学特征值分析,表明该套碳酸盐岩中稀土元素平均总含量(ΣREE)较低,为35.305μg/g;ΣLREE/ΣHREE比值为7.769～9.046,轻重稀土分馏明显,且稀土总含量(ΣREE)与SiO2和Al2O3含量呈正相关,与CaO含量呈负相关,说明沉积期有大量陆源碎屑注入。δCe平均值为0.966,基本无异常,但不同地层中有一定变化,布曲组到索瓦组一段、二段沉积水体氧化性显示为强-弱-强演化过程。LaN/YbN比值为1.124～1.493,其中索瓦组二段数值最小,沉积时期水体酸性最弱。表明研究区沉积水体具弱还原性,沉积时期有大量陆源碎屑注入,为近岸碳酸盐岩沉积。REE plays an important role in recognizing the sedimentary environment. In this paper ,base on the analysis of REE geochemical characteristics of carbonate rocks from the section plane of Nadi Kangri in North-Qiangtang basin,we discuss the sedimentary environment and sedimentary face of the Nadi Kangri area.And analyze the different characters of REE among different formations.The geochemistry analysis show that the average amount of REE of carbonate rocks is 35.305 gg/g and the lowest.The ratios of ELREE/EHREE is 7.769-9.046,and the correlation of ZREE with SIO2,A1203 is positive, but with CaO is negative. These result indicates that a lot of terrigenous sediments was brought into the water system of palaeoenvironment.The average value of 6Ce is 0.966 and appears weakly negative anomaly, and has weak variation in different formation.This result indicates that oxidation index of the environment has changed from Buqu to Suowa formation, and shows that the evolution process is strong to weak and to strong. The ratios of LaN/YbN between 1.124 tol.493,and the value of Suowa 2th formation is the least, shows that the water acidity is the weakest during the deposition period. All study results indicates that the water with weak reductive, a large number of terrigenous clastic was brought into the water during deposition period and the sedimentary environment was inshore carbonate sedimentary environment.

关 键 词：北羌塘盆地 那底岗日 稀土元素 地球化学特征 沉积环境分析 

分 类 号：P595[天文地球—地球化学] P512.2[天文地球—地质学]