Zhang Baohua, Fei Hongzhan, Ge Jianhua, Zeng Lingsen, Xia Qunke
Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province, School of Earth Sciences, Zhejiang University, Hangzhou, 310027, China.
Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, D-95440, Germany.
Nat Commun. 2022 Aug 9;13(1):4673. doi: 10.1038/s41467-022-32484-w.
Partial melting in the continental crust may play a critical role on the behavior of continents during collision. However, the occurrence of partial melt in orogenic continental crust is not well understood. Since the temperature of the orogen is controlled by the thermal properties of constituent rocks, we measured the thermal conductivity and diffusivity of eclogite, the most important ultrahigh pressure metamorphic rocks, as a function of pressure, temperature, composition, and water content, and simulated the thermal structure of the Sulu and Himalaya-Tibet orogens in eastern and southwestern China, respectively. Our results show that the temperature at 30-km depth beneath the orogens reaches the solidus of wet granite and phengite (940 K), therefore, the partial melting in the orogenic continental crust is well explained. The melt may facilitate the exhumation of subducted crust, produce the low seismic-velocity zone, and cause the high-conductivity anomaly in the shallow depth of orogenic belts.
大陆地壳中的部分熔融可能在碰撞过程中大陆的行为方面发挥关键作用。然而，造山带大陆地壳中部分熔体的出现情况尚未得到很好的理解。由于造山带的温度受组成岩石的热性质控制，我们测量了榴辉岩（最重要的超高压变质岩）的热导率和扩散率，作为压力、温度、成分和含水量的函数，并分别模拟了中国东部的苏鲁造山带和中国西南部的喜马拉雅 - 西藏造山带的热结构。我们的结果表明，造山带下约30公里深度处的温度达到了湿花岗岩和多硅白云母的固相线（约940K），因此，造山带大陆地壳中的部分熔融得到了很好的解释。熔体可能促进俯冲地壳的折返，产生低速地震波带，并在造山带浅部引起高电导率异常。
