安徽沿江地区晚石炭世黄龙组白云岩地球化学特征及其成因研究  

Geochemistry characteristics and origin of Upper Carboniferous Huanglong Formation dolomites in the Anhui segment of the Lower Yangtze area

作　　者：赵大千[1] 李双应[1] 王冰[1] 嵇在飞[1] 芦艳琳[1] 孟祥金[2] 吕庆田[2] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《地质科学》2012年第3期851-866,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家地质调查专项<长江中下游重要"矿源层"沉积环境与燕山期岩浆热液叠加成矿作用研究>;国家自然科学基金项目(41172097)资助

摘　　要：安徽沿江地区晚石炭世黄龙组白云岩广泛发育,主要为晶粒白云岩,其次是角砾白云岩和残余颗粒白云岩。地球化学分析表明,安徽沿江地区黄龙组白云岩中Fe、Mn、Sr、Na含量分别为:2 567×10^(-6)(1 600×10^(-6)～4 400×10^(-6))、353×10^(-6)(166×10^(-6)～742×10^(-6))、109.7×10^(-6)(69.0×10^(-6)～176.5×10^(-6))、288×10^(-6)(100×10^(-6)～700×10^(-6)),稀土元素总量为7.29×10^(-6)(2.56×10^(-6)～20.82×10^(-6)),∑LREE/∑HREE比值平均为3.07(1.16～10.17),经海水标准化后,显示LREE富集,HREE相对亏损,δCe平均为4.53(2.82～7.78),正异常显著,δEu平均为1.85(0.94～2.92),配分模式曲线显示白云岩化流体来自海水。白云岩中可见蒸发岩类或蒸发构造。综合分析认为该地区白云岩主要为准同生成因,部分为埋藏成岩成因,其中角砾白云岩为准同生成因,怀宁地区白云岩δEu平均为2.38(1.91～2.92),正异常显著,表明后期受到热液流体影响。Dolomites distribute widely in the lower part of the Late Carboniferous Huanglong Formation in the Anhui segment of the Lower Yangtze. Dolomites include three rock types, mostly rystalline dolomites, secondly breccia dolomites and remnant grain dolomites. According to geochemical analysis, Average concentrations of Fe, Mn, Sr and Na of dolomites of the Huanglong Formation are 2 567×10^-6（ 1 600×10^-6 -4 400×10^-6） , 353×10^-6（ 166×10^-6 -742 ×10^-6） , 109.7×10^-6（69.0×10^-6 - 176.5×10^-6） and 288×10^-6（ 100×10^-6 -700×10^-6） ; The average concentrations of REE is 7.29 ×10^-6 （ 2.56 ×10^-6 20.82 ×10^-6 ） and ratios of ELREE/ EHREE is 3.07 （1.16 - 10. 17 ）, After normalizing to standard seawater, it shows that dolomites are all rich in LREE and depleted in HREE. The average values of δCe and ∑u are 4.53 （ 2. 82 - 7.78 ） and 1.85 （0.94 - 2.92）, distributions of REEswN of dolomites indicate that dolomitization fluids come from seawater. Evaporative rocks and sedimentary structures could be found in dolomites in Anhui segment of the Lower Yangtze, so we think that dolomites of Huanglong Formation are mainly penecontemporaneous and some are formed by burial dolomitization,breccia dolomites are peneeontemporaneous. Besides, positive anomalies of Eu （the average of ∑Eu is 2.38 （ 1.91 - 2.92 ） ） of dolomites in Huaining area indicates that dolomites are effeeted by later hydrothermal activity.

关 键 词：晚石炭世 黄龙组 白云岩 地球化学 成因研究 安徽沿江地区 

分 类 号：P534.45[天文地球—古生物学与地层学] P588.245[天文地球—地质学]