Advanced characterization of hydrothermal flows within recharge and discharge areas using rare earth elements, proved through a case study of two-phase reservoir geothermal field in Southern Bandung, West Java, Indonesia
Advanced characterization of hydrothermal flows within recharge and discharge areas using rare earth elements, proved through a case study of two-phase reservoir geothermal field in Southern Bandung, West Java, Indonesia
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通过对印度尼西亚西爪哇省万隆南部两相储层地热田的案例研究，利用稀土元素对补给和排泄区域内的热液流进行了高级表征
DOI：
10.1016/j.geothermics.2022.102507
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发表时间：
2022
期刊：
影响因子：
3.9
通讯作者：
Irwan Iskandar
中科院分区：
文献类型：
--
作者：
Riostantieka Mayandari Shoedarto;Yohei Tada;Koki Kashiwaya;Katsuaki Koike;Irwan Iskandar
稀土元素分析是追踪地热和地下水系统中水-岩相互作用和溶质运移的有效方法。本研究旨在阐明地热系统补给和排放区域内的热液流动。选取印度尼西亚西爪哇省南万隆地区某知名的两相储层高温地热田为研究对象，采集了31个河流/泉水样品和8个井岩样品。水样中稀土元素总浓度变化范围广，河流为3.4 ~ 35 ppt，冷泉为0.3 ~ 284 ppt，温泉为1.4 ~ 102 ppm。太古宙后澳大利亚页岩正态化比球粒陨石正态化更清楚地表征了水样中轻稀土元素的富集。通过形态分析得出以下解释：河水中溶解的稀土元素来源于近地表地下水中常见的自由离子或Ln3+，主要成分为冷泉中的碳酸盐（LnCO3+）和Ln3+络合物以及温泉中的LnCO3+络合物。水蒸气和气体凝结成低氧地下水可以通过丰富的LnCO3+来指示。仅1个温泉与储层有较强的H2S凝结和LREE富集关系。其他冷泉和温泉的水可能通过浅层、深层和深居的含水层、渗透带和补给和排放区内的主要断层进行稀释、蒸发和岩浆气体冷凝。稀土元素分析结果还表明，含水层的主要成分为碳酸盐和硅酸盐矿物以及热液蚀变熔岩、安山岩熔岩和火山碎屑流沉积物。稀土元素有助于详细解释热液系统浅深水的地球化学相。最后，结合稀土元素、主要阴离子和阳离子、水同位素和锶同位素的分析结果，改进了地热储层地下水流动和补给-排放相互作用的概念模型。
Rare earth element (REE) analysis is effective for tracing water–rock interactions and solute transport in geothermal and groundwater systems. This study aimed to clarify hydrothermal flows within recharge and discharge areas of a geothermal system. We selected a well-known high-temperature geothermal field with two-phase reservoir in Southern Bandung, West Java (Indonesia) as a case study target, and collected 31 river/spring samples and 8 well rock samples. The measured total REE series concentrations ranged widely in the water samples, i.e., rivers: 3.4–35 ppt, cold springs: 0.3–284 ppt, and hot springs: 1.4 ppt to 102 ppm. Enrichment of light REEs (LREEs) in the water samples was characterized more clearly by Post Archean Australian Shale normalization than by chondrite normalization. Speciation analysis derived the following interpretations: dissolved REEs in the river water originated from free ions or Ln3+that are typically contained in near-surface groundwater, and the dominant components were carbonate (LnCO3+) and Ln3+complexes in the cold springs and LnCO3+complexation in the hot springs. Steam and gas condensation into less-oxygenated groundwater can be indicated by rich LnCO3+. Only one hot spring was interpreted as being directly connected with the reservoir by strong H2S condensation and LREE enrichment. The water of the other cold and hot springs probably underwent dilution, evaporation, and magmatic gas condensation through shallow, deep, and deep-perched aquifers, permeable zones, and a major fault within the recharge and discharge areas. REE results also suggest that the main constituents of the aquifers are carbonates and silicate minerals and hydrothermally altered lahars, andesitic lava, and pyroclastic flow deposits. REEs facilitate detailed interpretation of geochemistry facies in shallow–deep waters of a hydrothermal system. Finally, integration of the analysis results of REEs, major anions and cations, water isotopes, and strontium isotopes improved a conceptual model of groundwater flows and recharge–discharge interactions in aquifers feeding a geothermal reservoir.