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    青藏高原东北缘深部地质构造与地热资源分布关系研究

    Research on relationship between the deep structure and geothermal resource distribution in the Northeastern Tibetan Plateau

    • 摘要: 青藏高原内部及边缘分布大量地热田,主要有青海共和—贵德地热田、甘肃张掖盆地地热田、甘肃天水地热田、云南腾冲地热田等,所有地热田系统整体围绕青藏高原边缘呈带状展布,主要受控于青藏高原构造活动。对该区域多个地热田进行分析,均具有深部热源垂直传导供热、深大断裂和其发育的次级断裂为有利通道等特性。青藏高原深部分布多个通道流,在地震层析成像观测结果、远震P波走时层析成像等地球物理资料上均有显著反映,青藏高原中北部地壳低速-高导层是部分熔融层的岩石学证据亦被证实。主要地热田均分布在通道流沿线,根据地热田的研究成果,认为下地壳的通道流不仅为地热田提供热源,形成明显的大地热流异常区带,通道流区域的地壳厚度减薄、构造活动增强,热流易于向上传导运移。文章综合分析后初步建立了地热分布与通道流关系模型、与通道流相关的地热田地热模型,认为青藏高原东北缘地区分布的多个地热田均受控于其深部的通道流;通过对该区域地热资源前景进行分析,认为甘肃天水地区位于通道流的交汇部位,地热资源前景巨大。

       

      Abstract: Large number of geothermal fields are distributed on the margin and inside of the Tibetan Plateau, such as Gonghe-Guide geothermal field, Zhangye geothermal field, Tianshui geothermal field and Tengchong geothermal field. All these geothermal fields are basically characterized by zonal distribution along the Tibetan Plateau and systematically controlled by its tectonic activities. The analysis on multiple geothermal fields shows that they all have a deep heat source with vertical upward heating conduction through favorable channels from deep faults to their secondary faults. It is revealed that several channel flows exist under the deep Tibetan Plateau and are remarkably shown in geophysical data like the seismic tomographic imaging and teleseismic P-wave travel time tomography. It has also been verified by petrologic evidence that the low-velocity and high conductive layer beneath the crust of the Mid-Northern Tibetan Plateau is a partial melting layer. In view of geothermal fields distributed along the channel flow and combined with other research results, it is believed that the channel flows not only act as heating resources, but also form significant abnormal zones of terrestrial heat flow. In the area of channel flows, crust is thinned, structural activities are intensified, which enables heat to be easily transferred upward. According to comprehensive analysis, the relationship model of geothermal distribution and channel flow, and the geothermal field model related to channel flow are preliminarily established. It is believed that geothermal fields distributed in the northeast margin of the Tibetan Plateau are controlled by the channel flow in the deep crust. Through the analysis of the prospect of geothermal resources in this area, it is suggested that the Tianshui area in Gansu Province is located at the intersection of channel flows, and has great potential for prospecting of geothermal resources.

       

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