松嫩平原黑土区西北部阿荣旗地下黑土稀土元素特征及环境指示  

REE Geochemistry and Its Environmental Significance of Subsurface Black Soil from Northwestern Arongqi,Songnen Plain Black Soil District

作　　者：杜贯新 闫百泉[1] 孙雨[1] 钱程[2] 秦涛[2] 臧延庆 DU Guanxin;YAN Baiquan;SUN Yu;QIAN Cheng;QIN Tao;ZANG Yanqing(School of Earth Science,Northeast Petroleum University,Daqing,Heilongjiang 163318,China;Shenyang Center of Geological Survey,China Geological Survey,Shenyang,Liaoning 110034,China)

机构地区：[1]东北石油大学地球科学学院,黑龙江大庆163318 [2]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《现代地质》2023年第3期813-820,共8页Geoscience

基　　金：中国地质调查局地质调查项目(DD20190039-01)。

摘　　要：东北黑土的形成长期备受学者们的关注,然而人类活动不同程度影响着表层黑土的自然特征。地下黑土能较为真实地反映客观属性,但其研究仍然匮乏,由此本文选择松嫩平原黑土区阿荣旗钻孔内的地下黑土为研究对象,进行稀土元素地球化学测试,采用地质统计学分析地下黑土层ΣREE、HREE、LREE的分布特征,结合Ce异常、Eu异常、(La/Yb)N、(La/Sm)N、(Gd/Yb)N、Al_(2)O_(3)/TiO_(2)图解、Ceanom讨论了黑土的物源特征与环境记录。结果显示,阿荣旗地下黑土ΣREE含量较高,平均值为141.45×10^(-6)。球粒陨石标准化曲线表现为向右倾斜,轻稀土富集,δEu微弱负异常,δCe明显负异常。(La/Yb)N平均值7.58,(La/Sm)N平均值为1.14,(Gd/Yb)N平均值为3.54,表明地下黑土重、轻稀土元素分异程度大,轻稀土元素相比重稀土元素分馏作用更为显著;稀土元素配分曲线指示多个物源特征,δEu与Al_(2)O_(3)/TiO_(2)图解共同指示地下黑土的源岩为下白垩统中-酸性火山岩;Ceanom>-0.1(平均值3.9)指示其形成于还原环境。Formation of black soil in Northeast China has long been a research focus in the academia,but anthropological activities have influenced the study of surficial black soil to varying degrees.At present,there is a paucity of research on the underground black soil.In this study,the black soil from drill-cores at Arongqi of the Songnen Plain was sampled for REE geochemical analysis.Distributions ofΣREE,HREE and LREE elements of the deep black soil layer were analyzed by geostatistics.Combined with the Ce anomaly,Eu anomaly,(La/Yb)N,(La/Sm)N,(Gd/Yb)N,Al_(2)O_(3) vs.TiO_(2) diagram and Ceanom,the provenance and formation environment of the black soil are discussed.The results show that the subsurface black soil at Arongqi have highΣREE content(avg.141.45 mg·kg^(-1)).The right-inclining chondrite-normalized patterns show LREE enrichments,with weak negative Eu and strong negative Ce anomalies.The average(La/Yb)N=7.58,(La/Sm)N=1.14,and(Gd/Yb)N=3.54,indicating that the HREEs and LREEs are highly fractionated,and the LREE fractionation is stronger than that of HREE.TheδEu and Al_(2)O_(3)/TiO_(2) diagram indicate that the subsurface black soil was sourced from the nearby Cretaceous felsic-intermediate magmatic rocks.The Ceanom>-0.1(mean 3.9)suggests an anoxic environment.

关 键 词：黑土 环境指示 稀土元素 阿荣旗地区 物源示踪 

分 类 号：P595[天文地球—地球化学] X142[天文地球—地质学]