To better constrain the heat source of the geothermal system and lithospheric thinning mechanism of the Paleo-Pacific subduction zone, data from 35 broadband magnetotelluric (MT) stations were collected in 2020 along a 180-km-long NW-trending profile in the Cathaysia Block. Based on the measured data, we obtained the lithospheric electrical structure of the Cathaysia Block in South China using the 3D MT inversion code of ModEM. The final resistivity structure along the profile shows a series of highly conductive anomalies and highly resistive anomalies. The highly resistive anomalies in the upper crust correspond well with the distribution of magmatic rocks, which extend downwards to depths of 20 km. The highly resistive anomalies with a depth of 20–40 km are interpreted as crustal mafic sills derived from the mantle. The crustal conductors at depths of 5–15 km are typically interpreted as accumulations of aqueous fluids, which originate from the dehydration of the slab during the flat-slab subduction of the Paleo-Pacific Plate and are confined in the crust by impermeable layers. Fluid fractions of 0.8–9% would be required to explain the observed conductance values. The MT results indicate that there is no magma chamber or partial melt beneath the geothermal system. Therefore, the heat source of the geothermal system in the Cathaysia Block is radiogenic heat produced by the decay of radioactive elements in the crust. Thermal erosion has played a central role in lithospheric thinning and crust–mantle interaction of the Cathaysia Block.

为了更好地约束古太平洋俯冲带的地热系统热源和岩石圈减薄机制，2020年沿华夏地块180公里长的西北走向剖面收集了35个宽带大地电磁（MT）站的数据. 根据实测数据，利用ModEM 3D MT反演码获得华南华夏地块岩石圈电性结构。沿剖面的最终电阻率结构显示了一系列高导电异常和高电阻异常。上地壳的高电阻异常与岩浆岩的分布非常吻合，岩浆岩向下延伸至20公里深处。深度为 20-40 公里的高电阻异常被解释为来自地幔的地壳基性基岩。5-15 公里深处的地壳导体通常被解释为含水流体的聚集，它源于古太平洋板块平板俯冲期间板片的脱水，并被不透水层限制在地壳中。需要 0.8-9% 的流体分数来解释观察到的电导值。MT 结果表明地热系统下方没有岩浆房或部分熔体。因此，华夏地块地热系统的热源是地壳中放射性元素衰变产生的辐射热。热侵蚀在华夏地块的岩石圈减薄和壳幔相互作用中发挥了核心作用。源于古太平洋板块平板俯冲过程中板块的脱水作用，并被不透水层限制在地壳中。需要 0.8-9% 的流体分数来解释观察到的电导值。MT 结果表明地热系统下方没有岩浆房或部分熔体。因此，华夏地块地热系统的热源是地壳中放射性元素衰变产生的辐射热。热侵蚀在华夏地块的岩石圈减薄和壳幔相互作用中发挥了核心作用。源于古太平洋板块平板俯冲过程中板块的脱水作用，并被不透水层限制在地壳中。需要 0.8-9% 的流体分数来解释观察到的电导值。MT 结果表明地热系统下方没有岩浆房或部分熔体。因此，华夏地块地热系统的热源是地壳中放射性元素衰变产生的辐射热。热侵蚀在华夏地块的岩石圈减薄和壳幔相互作用中发挥了核心作用。MT 结果表明地热系统下方没有岩浆房或部分熔体。因此，华夏地块地热系统的热源是地壳中放射性元素衰变产生的辐射热。热侵蚀在华夏地块的岩石圈减薄和壳幔相互作用中发挥了核心作用。MT 结果表明地热系统下方没有岩浆房或部分熔体。因此，华夏地块地热系统的热源是地壳中放射性元素衰变产生的辐射热。热侵蚀在华夏地块的岩石圈减薄和壳幔相互作用中发挥了核心作用。