| 四川邻水高滩镇地热井含膏盐段岩屑稀土元素特征及意义 |
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| 关键词:Linshui County Gaotan Town geothermal well gypsum salt rare earth element |
| 基金项目:中国地质调查局环境地质及油气地质调查项目“成渝双城经济圈城市地质安全体检与风险评估”(编号: DD20221733)；“四川盆地西缘页岩气战略性矿产调查评价”(编号: DD20230322) |
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| Characteristics and Significance of Rare Earth Elements in Lithic Cuttings of Gypsum Salt Section of Geothermal Well in Gaotan Town, Linshui, Sichuan |
| The study of rare earth elements in paste salts can help identify the source of ore-forming materials, and have important significance for evaluating the ore-forming potential of potassium salts. A multi-layer paste salt interlayer was drilled in the Jialingjiang Formation–Leikoupo Formation of a geothermal well in Daobei Village, Gaotan Town, Linshui County, Sichuan, and petrological, rare-earth elements, and related trace elements were tested and analyzed. The study shows: (1) The gypsum salt beds in this area are mainly composed of gypsum and contain a small amount of terrigenous debris, such as potassium feldspar, quartz, and clay minerals. ΣREE is low, ranging from 7.18×10–6–77.63×10–6 with an average of 20.03×10–6, which is significantly lower than the total REE of mudstone and sandstone, and similar to the total REE of gypsum salt in Xinjiang Basin of Jiangxi Province and carbonate rocks in northern Anhui Province. ΣREE is positively correlated with the main carrier of Al (clay minerals), and HREE and LREE are also significantly positively correlated. Ree elements come from terrigenous clastic clay minerals in the nearby Luzhou palaeouplift and the adsorption of clay minerals on REE in water, which may be the main sources of REE elements in paste salts. The content of rare earth elements may be used as an index to evaluate the distance between paste salt and salt basin and ancient land. The mineral composition and rare earth element characteristics of the paste rock debris indicate that this area is close to the Luzhou palaeouplift, and the desalting effect of surface fresh water from the ancient land is the main reason for the failure to form large-scale potassium salt deposits in this area; (2) The rare earth elements of the paste salt formation in this area are relatively flat standardized curve of shale. LREE/HREE ranges from 3.02 to 3.72, with a mean value of 3.72. (La/Yb)N was between 1.15–1.63 with a mean value of 1.29. The curve inclined slightly to the right, and light rare earth were weakly enriched. δEu ranged from 1.14 to 6.89 with a mean of 2.65. δCe ranges from 0.81 to 0.87 with a mean of 0.85. It has an apparent positive Eu anomaly and weak Ce deficit, which is characterized by anoxic, reductive and strong acid environment, and hydrothermal sulfite reduction (TSR) exists in the formation or widely; (3) The La/Ce values, Zn-Ni-Co triangle diagram and LogTh-LogU correlation diagram show that the paste salt formation is a high-temperature environment, which promotes the development of TSR effect. In addition to the normal geothermal gradient, the high temperature may be more importantly related to the follow-up effect of the Emei basalt eruption and the volcanic eruption (mung bean rock) at the bottom of the Lekoupo Formation. These findings help understand the accumulation mechanism of earth elements in paste salt and positively promote the understanding of the geochemical behavior of earth elements in the process of paste salt deposition and diagenesis. |
| LIU Jianqing,HUANG Congjun,ZHU Huaping,HE Li,RAN Jing.2024.Characteristics and Significance of Rare Earth Elements in Lithic Cuttings of Gypsum Salt Section of Geothermal Well in Gaotan Town, Linshui, Sichuan[J].Acta Geoscientica Sinica,45(6):882-892. |
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