贵州威宁窑上组沉积物物源特征及沉积控制因素分析

Analysis of Sediment Provenance and Sedimentary Control Factors in Yaoshang Formation,Weining County in Guizhou Province

根据威宁草海第四纪窑上组沉积物主量元素和REE特征,探讨沉积物物源特征、气候演变情况、沉积物堆积控制因素。结果表明：Al、Mg、Ca、K、Na和Ti的含量变化在剖面上一致,它们的相关系数很高（0.522~0.985）。Fe含量和Mn含量呈正相关形式,与Al、Mg、Ca、K、Na和Ti呈负相关。Fe2O3含量在土黄色粘土的铁质层很高（42.86%~50.57%）。样品中REE球粒陨石标准化配分模式与贵州土壤、贵州碳酸盐岩风化壳配分模式很相似,与峨眉山玄武岩配分模式不一致,但其含量略低于贵州碳酸盐岩风化壳的含量;沉积物主要来源于碳酸盐岩,且碳酸盐岩强烈风化成土作用使REE超常富集,在剖面上呈现高ΣREE（平均219.38μg/g）。通过Mg/Ca、MgO/Al2O3、（CaO＋K2O＋Na2O）/Al2O3、（Fe2O3＋Al2O3）/（MgO＋CaO）、（K＋Na＋Ca＋Mg）/（Fe＋Mn）、（Al＋Fe＋Mn）/（K＋Ca＋Mg）和（MgO＋Na2O＋CaO）/Al2O3等气候指标研究,表明在草海窑上期为湖泊沉积时期,气候经历了由温暖湿润向冷干的转变。同时,认为物源性质、构造运动、气候等共同控制该区沉积物形成。

The feature of major elements and REEs composition of lake sediments of Yaoshang Formation in Guizhou,Weining County,are analyzed.The provenance features,climatic evolution and control factors of sediment accumulation have been discussed.The results show that： The change of abundance of Al,Mg,Ca,K,Na and Ti is consistent in the section.Their correlations between 0.522 and 0.985 are very high.Fe and Mn form a positive correlation,while they negatively correlate with Al,Mg,Ca,K,Na and Ti.The abundance of Fe2O3 in the yellow clay of iron layer is very high.The chondrite-normalized REE distribution patterns of samples are similar with that of soil and red clay of karst areas in Guizhou,almost similar with that of weathering crust of carbonate rocks in Guizhou,and are inconsistent with Emeishan basalt.The abundance of REEs is slightly lower than that of the weathering crust of carbonate rocks.The provenance mainly comes from carbonatites of which the strong weathering results in the abnormal enrichment of REEs in this section（ΣREE average 219.38 μg/g）.The climatic indicators of Mg/Ca,MgO/Al2O3,（CaO＋K2O＋Na2O）/Al2O3,（Fe2O3＋Al2O3）/（MgO＋CaO） and（K＋Na＋Ca＋Mg）/（Fe＋Mn） show that the climate has experienced the conversion from warm and humid to cold and dry.（Al＋Fe＋Mn）/（K＋Ca＋Mg） and（MgO＋Na2O＋CaO）/Al2O3 can also be used as the climatic indicators of lake sediments.The formation of deposits is controlled by provenance properties,iron rocks,tectonic movements and climate.