The Weihe basin possesses abundant in medium-low temperature geothermal resources. However, the primary source of heat in the basin, whether it stems from the mantle or crust, remains a subject of debate. In this study, we employ three-dimensional inversion of gravity and magnetic anomalies to ascertain the basement depth, Moho depth, Curie point depth, and spatial distribution of magnetic bodies within the Weihe basin. Our findings reveal that there is no correlation between heat flow and mantle uplift and the uplift area of the Moho does not coincide with the depocenter of the basin. These results suggest that the mantle heat brought by lithosphere thinning and stretching is not the predominant heat source in the Weihe basin. Furthermore, we observe a significant discrepancy in Curie point depth between the northern and southern sides of the Weihe fault within this region, indicating its role as a suture zone connecting two structural units throughout geological history. Through three-dimensional susceptibility inversion analysis, we identify a widespread distribution of magnetic bodies (primarily Yanshanian granites) beneath sediments within the Weihe basin which are connected to the granites located in the North Qinling area. This suggests that the granites formation within the Weihe basin may have occurred concurrently with the magmatic activity in the North Qinling area. Since Cenozoic timescale, northeastward compression exerted by the Tibet Plateau has resulted in passive strong fault depression within the Weihe basin while burying the previously intruded granites under thick sedimentary layers on a massive scale. These buried granites release heat through radioactive decay processes making them an essential heat source for the medium-low temperature geothermal fields.

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3D重磁反演揭示渭河盆地花岗岩放射性产热主导的地热结构

渭河流域拥有丰富的中低温地热资源。然而，该盆地的主要热源是来自地幔还是地壳，仍然是一个争论的话题。本研究利用重磁异常三维反演技术，确定了渭河盆地基底深度、莫霍面深度、居里点深度以及磁体空间分布。我们的研究结果表明，热流与地幔隆起之间不存在相关性，并且莫霍面的隆起区域与盆地沉积中心并不重合。这些结果表明，岩石圈减薄和拉伸带来的地幔热量并不是渭河盆地的主要热源。此外，我们观察到该地区渭河断裂带北侧和南侧的居里点深度存在显着差异，表明其在整个地质历史中作为连接两个构造单元的缝合带的作用。通过三维磁化率反演分析，我们发现渭河盆地沉积物下广泛分布着磁性体（主要是燕山期花岗岩），这些磁性体与北秦岭地区的花岗岩相连。这表明渭河盆地内花岗岩的形成可能与北秦岭地区的岩浆活动同时发生。新生代以来，青藏高原的北东挤压作用导致渭河盆地内部出现被动性强断陷，同时将先前侵入的花岗岩大规模埋藏在厚厚的沉积层之下。这些埋藏的花岗岩通过放射性衰变过程释放热量，使其成为中低温地热田的重要热源。