Determining subsurface temperature & lithospheric structure from joint geophysical-petrological inversion: A case study from Ireland
Determining subsurface temperature & lithospheric structure from joint geophysical-petrological inversion: A case study from Ireland
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DOI：
10.1016/j.tecto.2023.230094
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发表时间：
2023-11
期刊：
影响因子：
2.9
通讯作者：
E. Chambers;R. Bonadio;J. Fullea;Sergei Lebedev;Yihe Xu;D. Kiyan;Christopher J. Bean;Patrick A. Meere;Ben Mather;Brian M. O'Reilly
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文献类型：
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作者：
E. Chambers;R. Bonadio;J. Fullea;Sergei Lebedev;Yihe Xu;D. Kiyan;Christopher J. Bean;Patrick A. Meere;Ben Mather;Brian M. O'Reilly
在评估一个地区的地热潜力时，高质量的地温梯度和温度图至关重要。然而，确定地热潜力是一项挑战，因为现场温度的直接测量很少，而且个别地球物理方法对一系列参数（而不仅仅是温度）敏感。在这里，我们开发了一种使用新的联合地球物理-岩石学反演来确定地温梯度的新方法，其中地幔中的地震速度和密度与热力学框架内的温度和体积成分相关。地震表面波相速度的大型数据集现已纳入反演中，并为岩石圈厚度和温度提供基本约束，这在很大程度上影响了地壳地温。我们还包括地壳内表面热流、放射热产生（RHP）和热导率的所有可用测量值，以进一步限制温度和地温梯度，特别是在地壳顶部几公里处。我们以爱尔兰为案例研究，展示了我们的新方法如何能够重现以前的工作结果，同时又如何改进它们，这要归功于全方位数据的互补敏感性。岩石圈和地壳厚度对温度梯度具有主要控制作用，岩石圈较薄的区域显示出较高的地温梯度。在某些地方，异常温暖的地温是由于地壳花岗岩、泥岩和页岩内的高 RHP 造成的。 RHP 高于整个爱尔兰的大陆平均水平，可能是由于地壳主要为长英质岩性。新方法提供了一个强大的工作流程，用于确定直接温度测量有限的地区的地热潜力，促进向可持续能源过渡和能源自给自足的知识创造。
High quality maps of the geothermal gradient and temperature are essential when assessing geothermal potential for a region. However, determining geothermal potential is a challenge as direct measurements of in situ temperature are sparse and individual geophysical methods are sensitive to a range of parameters, not solely temperature. Here, we develop a novel approach to determine the geothermal gradient using a new joint geophysical-petrological inversion where seismic velocities and density in the mantle are related to temperature and bulk composition within a thermodynamic framework. Large datasets of phase velocities of seismic surface-waves are now incorporated into the inversion, and provide essential constraints on the lithospheric thickness and temperature, which shape the crustal geotherms to a significant extent. We also include all available measurements of the surface heat flow, radiogenic heat production (RHP) and thermal conductivity within the crust, to further constrain the temperature and geothermal gradient, in particular in the top few kilometres of the crust. We use Ireland as a case study and show how our new methodology can reproduce the results of previous work but also improve on them, thanks to the complementary sensitivities of the full range of data. Lithospheric and crustal thicknesses have primary controls on the temperature gradient, with areas of thinner lithosphere showing higher geothermal gradients. In some locations, anomalously warm geotherms result from high RHP within crustal granitic rocks, mudstone and shales. RHP is above continental averages across all Ireland, likely due to a crust with mostly felsic lithology. The new methodology provides a robust workflow for determining the geothermal potential in areas with limited direct temperature measurements, facilitating knowledge creation for the transition to sustainable energy sources and energy self-sufficiency.