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稀土元素是研究沉积岩的形成条件及环境特征的重要指标,本文以桂林寨底地下河系统中岩石样品为研究对象,采用激光剥蚀电感耦合等离子体质谱进行稀土元素测试分析,研究了该地区碳酸盐岩的形成环境。结果表明:碳酸盐岩的稀土总量(∑REEs)偏低,不同地层岩性间的∑REEs具有一定差异性,总体上信都组泥质粉砂岩(D2x)的∑REEs最高,其次为融县组(D3r)厚层灰岩和桂林组灰岩(D3g),东村组厚层灰岩(D3d)和额头村组灰岩及白云质灰岩(D3e)的∑REEs较低。整体上表现为重稀土元素相对于轻稀土元素富集的特征,且Ce具有较明显的负异常,而Eu无异常或异常不明显,不同于碎屑岩的轻稀土相对富集、Eu负异常、Ce无异常或异常不明显的特征。这些特征表明研究区碳酸盐岩的形成环境为氧化-海相碳酸盐岩沉积环境,可为定量化判别岩溶区碳酸盐岩形成环境提供依据。
REE is an important index to study the formation conditions and environmental characteristics of sedimentary rocks. In this paper, the rock samples from the underground river system in Guilin sub-bottom are used as the research object, and the REE coupled with coupled plasma mass spectrometry is used to analyze the REE. Salt rock formation environment. The results show that the total REEs of carbonate rocks are low, and the ΣREEs between lithologies of different strata are quite different. Generally, the ΣREEs of the Xindu muddy siltstone (D2x) is the highest, followed by The ΣREEs of the thick limestone of D3r and the limestone of D3 in Guilin Formation, D3d in Dongcun Formation and the limestone and dolomitic limestone in D3 / D3 in Weitou Formation are relatively low. As a whole, the heavy rare earth elements are enriched relative to the light rare earth elements, and Ce has obvious negative anomalies without any abnormalities or obvious anomalies of Eu. The light rare earths different from clastic rocks are relatively enriched and Eu negative anomalies , Ce no abnormal or abnormal obvious characteristics. These characteristics indicate that the formation environment of carbonate rocks in the study area is an oxidized-marine carbonate depositional environment, which can provide a basis for quantitatively determining carbonate rock formation in the karst area.