摘要:
水热蚀变与泉华作为地热流体水-岩反应和化学沉积的产物,其相关研究可为水热活动发展史、恢复地热流体古温度及水岩反应过程等方面研究提供重要信息。古堆地热田位于错那—沃卡裂谷中部,是继羊八井地热田之后我国大陆最具发电潜力的非火山岩型高温地热田之一,极具开发潜力。为了解古堆地热田泉华和水热蚀变的类型、分布特征及判断有利的勘探方向,本文在野外地热地质调查的基础上,结合室内镜下鉴定和扫描电镜分析等工作,识别出绿泥石化、硅化、高岭石化和碳酸盐化等水热蚀变类型。研究发现,古堆地热田水热蚀变呈现出从蚀变中心向外由酸性蚀变过渡为弱酸性-中性蚀变的分带模式,蚀变中心常由强烈蚀变的硅化带或高岭石带组成;水热蚀变分布受断裂构造的控制,蚀变在断裂交汇处最为强烈,蚀变中心常沿着断裂延伸;根据水热蚀变的分布及蚀变强度,初步判断布雄朗古和杀嘎朗嘎的渗透性相对较好且热储温度高,具有较好的开发前景。在泉华沉积方面,古堆地热田西区主要为钙华区,东区为钙华和硅华叠加区;结合青藏高原动力学背景,认为古堆地热田水热发展史与陆陆碰撞的隆升过程及错那—沃卡裂谷活动密切相关且存在明显的耦合关系。
关键词:
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古堆
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水热蚀变
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蚀变分带
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泉华
Abstract:
As the results of water-rock interaction and geothermal fluid chemical deposition, the hydrothermal alteration and sinter can provide important information to research on hydrothermal activity history, geothermal fluid temperature, and water-rock interaction process. The Gudui geothermal field, located in the central Cone–Oiga rift, is a shallow buried high-temperature geothermal field with the greatest power generation potential in China after Yangbajing geothermal field, and has great development potential. In order to analyze the type and distribution characteristics of sinter and hydrothermal alteration, favorable exploration direction in Gudui geothermal field, and the coupling relationship between hydrothermal deposition and regional tectonic; based on geothermal geological investigation, microscopic identification, and scanning electron microscope analysis,identified hydrothermal alterations such as chloritization, silicification, kaolinization, and carbonation. The hydrothermal alteration in Gudui geothermal field exhibits obvious hydrothermal alteration zonation, which extends from acidic alteration to weak acidic-neutral alteration, and the alteration center is mainly composed of extensively altered silicification or kaolinization zones. The distribution of hydrothermal alteration is controlled by fault, and the alteration center, which is mainly located in the junctions of faults, extends along the faults. The distribution and intensity of hydrothermal alteration implies that the Buxionglanggu and Shagalangga have enormous resource potential. Therefore, geothermal exploration in Gudui geothermal field should focus on the Bushonglanggu and Shagalanga. In terms of hydrothermal deposition, the west area of Gudui geothermal field is dominated by travertine, and the east area is dominated by travertine and geyserite. Furthermore, combined with the dynamic background of Qinghai–Tibet Plateau, an obvious coupling relationship exists between hydrothermal history and the uplift of Qinghai–Tibet Plateau during continent-continent collision and the activity of the Cone–Oiga rift.
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