冀东陆壳热结构─—由岩石学模型推导
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摘要
本文根据变质岩矿物对的平衡热力学研究结果，提出冀东地区早前寒武纪陆壳平均地温分布曲线，并讨论现代陆亮地温曲线的两种可能形态．早前寒武纪在相当于中、下地壳的部分，地温的平均梯度约为７．３℃／ｋｍ，它预示了对流热传输占有重要地位（约占６５％）．基于传导热传输的假设，现代地温分布是一条平滑的曲线，而基于中地壳是一个含水的低速层以及对流热传输的假设，现代地温分布则可能是一条折线．退变质作用引起的放热与扩容可能是诱发地震的能量来源之一．
he author presents average crustal geotherm of Eastern Hebei Province in Early Precambrian and discusses two possible types of the present geotherm.The average geotherm gradient within the middle and lower crust of Eastern Hebei Province in Early Precambrian is about 7.3℃/km,which suggests that the convective heat transfer may be a main way controlling the geotherm distribution.The estimated contributions of the convective and conductive heat transfer are about 65% and 35%,respectively.The geotherm with 7.3℃/km is believed to be a representative of perturbation of the thermal structure resulted from the tectonothermal events in Early Precambrian.Based on the model of conductive heat transfer,the present geotherm has a smooth curve.But on the basis of that the middle crust is a low-velocity layer with interstitial hydrous fluids and the convective heat transfer,there is another possibility that the present geotherm may have a broken curve.Retrogressive metamorphism may occur in the middle crust because the present geotherm is much lower than the Early Precambrian geotherm and the middle crust contains hydrous fluids. The exothermal and volume expansion processes caused by the retrogressive metamorphism may be one of the energy-source inducing earthquakes.
he author presents average crustal geotherm of Eastern Hebei Province in Early Precambrian and discusses two possible types of the present geotherm.The average geotherm gradient within the middle and lower crust of Eastern Hebei Province in Early Precambrian is about 7.3℃/km,which suggests that the convective heat transfer may be a main way controlling the geotherm distribution.The estimated contributions of the convective and conductive heat transfer are about 65% and 35%,respectively.The geotherm with 7.3℃/km is believed to be a representative of perturbation of the thermal structure resulted from the tectonothermal events in Early Precambrian.Based on the model of conductive heat transfer,the present geotherm has a smooth curve.But on the basis of that the middle crust is a low-velocity layer with interstitial hydrous fluids and the convective heat transfer,there is another possibility that the present geotherm may have a broken curve.Retrogressive metamorphism may occur in the middle crust because the present geotherm is much lower than the Early Precambrian geotherm and the middle crust contains hydrous fluids. The exothermal and volume expansion processes caused by the retrogressive metamorphism may be one of the energy-source inducing earthquakes.
引文
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