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川东南—黔中及其周边地区自晚震旦世早期以来沉积环境受后期构造运动改造的影响很大,对该区下组合烃源岩沉积古环境进行恢复有重要的地质意义。对研究区样品的稀土元素地球化学分析结果表明,该区泥岩和页岩的稀土总量最高,(∑LREE/∑HREE)和(La/Yb)_N及(La/Sm)_N等显示,烃源岩具有轻稀土元素富集的配分型式,整体上随地层时代变新陆源影响增强;轻稀土元素之间分异中等,重稀土元素之间分异不明显。δCe均呈现负异常,并随地层变老和灰岩岩性异常增强,反映了研究区总体沉积环境为较深海水环境。Eu呈弱的负异常,只有寒武系渣拉沟群、都柳江组和牛蹄塘组样品的δEu呈正异常,印证了黔东南地区当时处在深水陆棚和远离陆源的沉积环境。
The sedimentary environment in southeastern Sichuan-central Guizhou and its surrounding areas has been greatly affected by the remolding of tectonic movements since the late Neocegas. It is of important geological significance to restore the paleoenvironment of sedimentary assemblages in this area. The results of REE geochemical analysis of the samples in the study area show that the total amount of rare earths in the mudstone and shale is the highest (ΣLREE / ΣHREE) and (La / Yb) _N and (La / Sm) _N, The distribution pattern of light rare earth elements in source rocks shows an overall increase with the change of terrestrial land-sourced new terrestrial sources. The distribution of light rare earth elements is moderate and the distribution of heavy rare earth elements is insignificant. δCe show negative anomalies, and with the aging of the formation and abnormal enhancement of limestone lithology, the overall sedimentary environment in the study area is deeper seawater environment. Eu shows a weak negative anomaly. Only the δEu of the samples from the Brala Group, the Duyujiang Group and the Niutizang Formation in the Cambrian are positive anomalies, which confirms the sedimentary environment in the southeastern Guizhou at that time in the deep-water shelf and away from the terrestrial source.