ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    共和盆地深部构造格架及其对干热岩热源的影响

    Deep Tectonic Framework of Gonghe Basin and Its Influence on Heat Source of Dry Hot Rock

    • 摘要: 干热型地热资源作为一种新型的地热资源形式,是一种发展前景广阔的新型清洁能源。青海省共和盆地位于青藏高原东北缘,区域地质活动丰富,为干热岩的形成创造了良好的条件。因此,研究共和盆地构造格架与干热岩成热模式,对地热资源勘探具有重要意义。笔者基于重力异常归一化总水平导数垂向导数技术(NVDR-THDR)和重磁异常融合方法划分了共和盆地的断裂构造格架,共识别深大断裂20条,有9条是前人未识别断裂。其中,F1-15推断断裂作为共和盆地东西分界断裂,对共和盆地干热岩成因具有重要意义。基于超低频大地电磁测深剖面及重力异常归一化总梯度的反演结果显示,共和盆地地幔物质向上运移并加热和侵蚀岩石圈底部,导致岩石圈底部发生熔融减薄。盆地东部和西部均存在自青海南山及贵南南山向盆地的逆冲推覆构造,但深部地质结构存在明显差异。盆地西部地质体挤压变形程度强于盆地东部,西部盆地深部地质体密度结构呈“八”字型特征,表现为压陷盆地的特征,断裂发育较少;而东部盆地大量发育深大断裂,为深部的热源物质和热量提供了传输通道。因此,认为共和盆地干热岩热源以地幔热流传导供热和壳内部分熔融层供热为主,放射性元素衰变生热为辅,盆地东部相较于西部更具备干热岩成藏条件。

       

      Abstract: As a new type of geothermal resource, dry-hot geothermal resource is a type of clean energy with broad development prospects. The Gonghe basin in Qinghai Province is located in the northeastern margin of the Qinghai-Tibet Plateau. The regional geological activities are rich, which creates good conditions for the formation of hot dry rock. Therefore, it is of great significance to study the tectonic framework of the Gonghe Basin and the heat generation model of dry-hot rock for geothermal resource exploration. Based on the normalized vertical derivative of total horizontal derivative of gravity anomaly (NVDR-THDR) and the fusion method of gravity and magnetic anomalies, the fault tectonic framework of Gonghe basin has been divided. A total of 20 deep and large faults are identified, and 9 of them are not identified by predecessors. The inferred F1-15 fault is the east-west boundary fault of Gonghe basin, which is of great significance to the genesis of dry-hot rock in Gonghe basin. The results from the ultra-low frequency magnetotelluric sounding profile and the normalized total gradient inversion of gravity anomalies show that the mantle material of the Gonghe basin migrated upward, heated and eroded the bottom of the lithosphere, resulting in melting and thinning of the bottom of the lithosphere. The basin are subject to the thrust nappe of the Qinghai Nanshan and Guinan Nanshan, but there are obvious differences in the deep geological structure between the eastern part and western part. The degree of extrusion deformation of the geological body in the western part is stronger than that in the eastern part. The density structure of the deep geological body in the western basin is characterized by an ' eight ' shape, which is characterized by a depressed basin, but the faults are less developed. A large number of deep faults are developed in the eastern basin, which provides a transmission channel for deep heat source materials and heat. Therefore, it is considered that the heat source of dry-hot rock in Gonghe basin is dominated by mantle heat flow conduction and partial melting layer in the crust, supplemented by heat generation of radioactive element decay, and the eastern part of the basin has more dry-hot rock accumulation conditions than the western part.

       

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