{"title":"Geochemical study of fluid origin and caprock formation with carbonate mineral precipitation in the Okuaizu geothermal area","authors":"Dongyang Mao , Jing Zhang , Yukiko Hoshino , Sakurako Satake , Heejun Yang , Hideki Kuramitz , Akira Ueda , Amane Terai","doi":"10.1016/j.geothermics.2024.103242","DOIUrl":null,"url":null,"abstract":"<div><div>To elucidate the origin and mechanism of carbonate mineral precipitation controlling fluid movement in geothermal active areas, analyses were conducted in the Okuaizu geothermal area (with a maximum temperature of 340 °C). Carbon and oxygen isotopes and chemical compositions were analyzed for carbonate minerals in rocks from four newly drilled geothermal wells and one existing well. Carbon content in the rocks increased gradually from 200 to 500 m above sea level (mASL; above sea level), sharply increasing to a maximum of 3 wt% near the study area's center. Stable isotope composition data were combined with well temperature data to compute oxygen and carbon isotope compositions of the fluids. Results suggest that the fluids precipitating carbonate minerals originate from a mixture of meteoric water, fossil seawater, and magmatic fluids at depths <−500 mASL. Carbon primarily originates from shallow organic matter sources and deep magmatic CO<sub>2</sub>. The caprock formation in the Okuaizu geothermal area occurs at shallow depths, with temperatures ranging from 100 °C to 150 °C, and comprises carbonate and clay minerals. This indicates that conditions conducive to CO<sub>2</sub> interaction with rocks and subsequent fixation as carbonate minerals in the formation develop at relatively low temperatures and shallow depths.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103242"},"PeriodicalIF":3.5000,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geothermics","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0375650524003286","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
To elucidate the origin and mechanism of carbonate mineral precipitation controlling fluid movement in geothermal active areas, analyses were conducted in the Okuaizu geothermal area (with a maximum temperature of 340 °C). Carbon and oxygen isotopes and chemical compositions were analyzed for carbonate minerals in rocks from four newly drilled geothermal wells and one existing well. Carbon content in the rocks increased gradually from 200 to 500 m above sea level (mASL; above sea level), sharply increasing to a maximum of 3 wt% near the study area's center. Stable isotope composition data were combined with well temperature data to compute oxygen and carbon isotope compositions of the fluids. Results suggest that the fluids precipitating carbonate minerals originate from a mixture of meteoric water, fossil seawater, and magmatic fluids at depths <−500 mASL. Carbon primarily originates from shallow organic matter sources and deep magmatic CO2. The caprock formation in the Okuaizu geothermal area occurs at shallow depths, with temperatures ranging from 100 °C to 150 °C, and comprises carbonate and clay minerals. This indicates that conditions conducive to CO2 interaction with rocks and subsequent fixation as carbonate minerals in the formation develop at relatively low temperatures and shallow depths.
期刊介绍:
Geothermics is an international journal devoted to the research and development of geothermal energy. The International Board of Editors of Geothermics, which comprises specialists in the various aspects of geothermal resources, exploration and development, guarantees the balanced, comprehensive view of scientific and technological developments in this promising energy field.
It promulgates the state of the art and science of geothermal energy, its exploration and exploitation through a regular exchange of information from all parts of the world. The journal publishes articles dealing with the theory, exploration techniques and all aspects of the utilization of geothermal resources. Geothermics serves as the scientific house, or exchange medium, through which the growing community of geothermal specialists can provide and receive information.