地表柯石英的实验室模拟合成及其形成机制的研究

 静高压合成柯石英的压力和温度的实验条件是提出地球板块折返假说的基础，然而，静高压没有反映局部碰撞和剪切应力的因素。考虑这些因素，提出了一种利用高能机械球磨与静高压相结合的、可以模拟地表柯石英合成的实验室研究方法，发现了一种由机械碰撞引起的α-石英中间亚稳相，其静高压致晶化成柯石英的条件为3.0 GPa、923 K、<1.0 min。如果沿袭传统的板块折返假设，对应此条件的板块俯冲深度应比Jr.L.Coes的结果浅20 km。发现了10 s量级的柯石英的短时间快速合成现象。由本方法合成的柯石英的Raman峰，涵盖了以前得到的天然柯石英和人工合成的柯石英的Raman信息。阐明了由本方法合成的柯石英在地质科学上的涵义，并提出了另一种可能的地表柯石英形成机制。

Modelling Synthesis in Laboratory of Coesite in the Earth's Crust and Its Formation Mechanism

The factors of collision and shear stress in the coesite formation has not been considered in the condition of high static pressure that was the base of the hypothesis of subduction-return of slab in the Earth. After considered these factors, a laboratory method of combining the high-energy mechanical ball milling ( HEMBM ) and high static pressure was suggested in this paper for modelling synthesis of coesite in the Earth's crust. A mechanical collision-induced intermediate phase of α-quartz has been discovered. Its condition of easily crystallizing into coesite induced by high static pressure is 3.0 GPa, 932 K, and <1.0 min. The Raman peaks for the coesite synthesized by the present method have covered over the all information of those natural and synthesized coesite obtained before. This implicated that the coesite in the Earth's crust and subduction-return of slab maybe not come from as deep as common accepted value because of its lower pressure 3.0 GPa than that suggested by Jr. L . Coes. However, according to the fact discovered in this paper that the coesite could be synthesized under a condition of very short time (about 10 s) by the high static pressure after pre-treated of HEMBM, the intermediate phase of α-quartz could be transformed into coesite instantaneously by the interaction of an earthquake wave and/or stress. Therefore we suggest some other possible formation mechanisms for coesite in the Earth's crust and show that the coesite in the Earth's crust could record some information about the collision dynamics of plates and an earthquake wave.