Terrestrial heat flow and crustal thermal structure of the Gonghe-Guide area, northeastern Qinghai-Tibetan plateau
Terrestrial heat flow and crustal thermal structure of the Gonghe-Guide area, northeastern Qinghai-Tibetan plateau
复制标题
DOI：
10.1016/j.geothermics.2017.11.011
复制
发表时间：
2018-03
期刊：
影响因子：
3.9
通讯作者：
Chao Zhang;G. Jiang;Yizuo Shi;Zhuting Wang;Yi Wang;Shengtao Li;X. Jia;Shengbiao Hu
中科院分区：
文献类型：
--
作者：
Chao Zhang;G. Jiang;Yizuo Shi;Zhuting Wang;Yi Wang;Shengtao Li;X. Jia;Shengbiao Hu
共和-贵德地区位于青藏高原东北缘，是中国地区热干岩地热资源勘查开发潜力最大的地区。研究区被瓦里贡构造岩浆带隔开，包括共和盆地和贵德盆地，它们具有明显不同的热状态和地表热表现。虽然进行了一些地球物理勘探，但关于地热基本理论的研究仍然很少，包括缺乏高质量的热流测定和热结构研究。在这项研究中，我们从共和盆地的GR2和DR3和贵德盆地的ZR1三个深井获得了连续的稳态温度测井。测量了两个盆地露头样品的热导率和辐射产热率。共和盆地的热流值为116.3-122.3 mW/m−2，平均值为119.3 mW/m−2。已有的两个热流点(R2和R3钻孔)的平均热流值为75 mW/m−2，大致相当于青藏高原东北部的区域背景热流水平。通过求解稳态热传导方程，建立了共和盆地和贵德盆地的一维理论地壳热结构。结果表明，贵德盆地的莫霍面温度和地幔热流分别为1016℃和27兆瓦/m−2。共和盆地的温度场显示地壳部分熔融。共和盆地的高温和热流可能表明地壳中存在异常热源体。通过对埋深5~6千米、水平尺寸12~14千米的冷却矩形岩浆室的数值模拟，成功地反演了共和盆地钻孔的垂直和水平温度变化。研究强调，共和盆地热流异常可能是以下因素共同作用的结果：(1)青藏高原东北部的高区域背景热流水平，这主要是由于增厚地壳的辐射热；(2)浅层岩浆房的冷却，这可能是由于高原的抬升和剥蚀造成的。
The Gonghe-Guide area, which is located at the northeastern edge of the Qinghai-Tibetan Plateau, has the greatest hot dry rock (HDR) geothermal resources exploration and development potential in China. Separated by the Waligong tectonomagmatic belt, the study area includes the Gonghe and Guide basins, which are characterized by distinctly different thermal state and surface thermal manifestations. Although a number of geophysical explorations have been undertaken, studies on fundamental geothermal theory remain scarce, including a lack of high-quality heat flow determinations and thermal structure studies. In this study, we obtained continuous steady-state temperature logs from three deep boreholes (GR2 and DR3 in the Gonghe basin and ZR1 in the Guide basin). The thermal conductivities and radiogenic heat production rates of the outcrop samples gathered from the two basins were measured. The heat-flow values were determined to be 116.3–122.3 mW m−2for the Gonghe basin, yielding a mean of 119.3 mW m−2. Two existed heat flow sites (R2 and R3 boreholes) gave an average heat flow of 75 mW m−2for the Guide basin, which is approximately that of the regional background heat flow level of the northeastern Tibetan Plateau. The 1-D theoretical crustal thermal structures of the Gonghe and Guide basins were constructed by solving steady-state heat conduction equation. The results show that the Moho temperature and mantle heat flow in the Guide basin were 1016 °C and 27 mW m−2, respectively. However, the temperature field in the Gonghe basin indicated partial melting in the crust. The high temperatures and thus heat flow in the Gonghe basin may suggest the existence of anomalous heat source body in crust. Successful inversions of vertical and horizontal temperature variations of boreholes in the Gonghe basin were obtained by numerically simulating a cooling rectangular magma chamber with a buried depth of 5–6 km and horizontal dimensions of 12–14 km. The study emphasizes that the anomalous heat flow in the Gonghe basin may be the joint thermal effect of: (1) the high regional background heat flow level of the northeastern Tibetan Plateau, which is mainly due to the radiogenic heat of thickened crust; (2) the cooling of a shallow magma chamber, which may be caused by the uplift and denudation of the plateau.