花岗岩研究的反思

Meditation on Granite Research

花岗岩是地壳生长、发展以及再循环的地质见证,是地质科学中壳-幔相互作用研究的一个重要课题,同时也是流体与固体地球化学相互作用领域的研究前沿。近二百年来,有关花岗岩的研究经久不衰,大致可分为4个阶段。(1)混合花岗岩派与岩浆花岗岩派的论争,代表花岗岩成因研究开始进入理性认识阶段。一派以变质作用条件下地壳重熔的地质观察为基础,另一派以简单的玄武岩浆分异为依据,而展开论争。(2)地壳重熔实验阶段。以地壳岩石为源岩的热力学实验的开展,是花岗岩热力学研究的开始。(3)随着重熔实验的全面开展,包括了微量元素及同位素的研究,促使热力学熔融体系在花岗岩成因研究上进入全面应用阶段,使地质上的共生组合法则得以与热力学接轨。同时由于微量元素应用于花岗岩,它的多元机理(multiple stage mechanism)进一步确立,为动态研究的开展打下了一定的基础。(4)花岗岩成因与大地构造结合阶段,属于近代花岗岩研究的范畴,代表着花岗岩体系与动态地质演化过程的接轨,并开始建立一个地质实际的观察模式,为进一步向动力理论发展做好准备。为此,对花岗岩研究发展过程中出现的几个问题,如平衡热力学的应用,流体在花岗岩中的重要性,花岗岩成因与大地构造的结合以及热在长期的演化过程中的变化等问题进行了讨论。

The granite petrogenesis evidenced as the growth and the recycling of the Earth＇ s crust has been known as one of the far-reaching problem related to the geodynamics of mantle vs. crust and the geochemistry of the liquid in filtration within the solid state of the Earth as well. During its development, the origin of granite may be accounted as follows ： （ 1 ） Migmatitic granite vs. magmatic granite. It signifies the beginning era geological observations of the metamorphic origin of granite on the one hand, and the elementary thermodynamic treatment of granite on the other hand. A bitter controversy has been argued nearly about one hundred years. （ 2 ） The stage of anatexis. A stage of laboratory experiment modelling the natural melting of crustal rocks into granite has been initiated. （ 3 ） The stage of prevailing of the anatexis. It comprises the major and minor elements all over the anatexis in order to verify the consistencies between geological observation, and those of the thermodynamic treatment, in aiming at the interconnection between geological observation, of the natural granite system and that of the thermodynamic system. （ 4 ） The origin of granite related to tectonics. It represents a beginning of the advancing stage toward the geodynamic prospective through the role of paragenesis, which is in connection with the thermodynamic principle in order to form a global pattern of granite petrogenesis. Various themes have been proposed and argued to their true aims it attained. Finally, some vital problems concerning the application of equilibrium thermodynamics, the role of fluid in the mechanism of granite petrogenesis, and some problems concerning the origin of granite with respect to tectonics as well as the heat dissipation through secular change have been discussed.