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通过对采自河北汉诺坝玄武岩中的下地壳和上地幔包体的详细研究 ,建立了本区下地壳—上地幔地温线。该地温线高于大洋地温线和古老地盾地温线 ,接近克拉通边缘的地温线 ,符合该区的大地构造环境。由该地温线建立的下地壳—上地幔地质结构剖面表明 ,该区下地壳主要由不同类型的麻粒岩相岩石组成 ,其化学成分以镁铁质为主 ,深度范围为 2 5～ 4 2km。上地幔由超镁铁质的二辉橄榄岩组成 ,在尖晶石二辉橄榄岩和石榴石二辉橄榄岩之间有一过渡层。由地温线确定的壳幔边界位于 4 2km附近 ,与地震资料确定的莫霍面一致 ,但在壳幔边界之上的下地壳底部有下地壳麻粒岩和超镁铁质岩的互层。这一现象可以解释在下地壳底部常见的层状反射层。该区岩石圈底界大约在 95km ,其下的软流层仍由石榴石二辉橄榄岩组成。
Based on the detailed study of the lower crust and upper mantle crust collected from the basalt of Hannuoba in Hebei Province, the lower crust-upper mantle geothermal line in this area has been established. The geothermal line is higher than the geothermal and ancient geotemperature geothermal lines, close to the craton edge of the geothermal line, in line with the geotectonic environment of the area. The section of the lower crust-upper mantle geologic structure established by this geothermal line shows that the lower crust in this area is mainly composed of different types of granulite-facies rocks, and its chemical composition is dominated by mafic and its depth ranges from 25 to 42 km . The upper mantle is composed of ultramafic lherzolites with a transitional layer between spinel lherzolites and garnet lherzolites. The crust-mantle boundary determined by the geothermal line is located near 4 2 km, which is consistent with the Moho determined by the seismic data. However, there is an interbedded layer of lower crustal granulites and ultramafic rocks at the bottom of the lower crust above the crust and mantle boundaries. This phenomenon can explain the layered reflective layer commonly found in the bottom of the lower crust. The bottom of the lithosphere in this area is about 95 km, and the underlying asthenosphere is still composed of garnet lherzolite.