Evolution of the Hida metamorphic rocks from the view point of clinopyroxene mineralogy

从单斜辉石矿物学角度探讨了希达变质带的演化。主要结论如下：1.希达变质带的单斜辉石片麻岩是由变基性岩和灰岩机械混合而成，反应为tr+cc+qz=di+H2O+CO2。安山岩型岩石既有岩石机械混合的产物，也有角闪岩脱水熔融的产物.岩石的机械混合是交代反应的主要过程。这一过程导致了体系的成分变化，从而由于岩石简单混合物的自由能与产物的自由能之差而发生变质反应。这类变质反应属于非等化学反应，与一般认为变质反应是在等化学体系内随温度和压力变化而发生的观点不同.非等化学反应的概念扩展到流体轴承系统。研究发现，岩石机械混合变质反应导致流体相的突然释放和成分变化，从而可能发生不同的反应.在大陆前缘，即大陆移动的带，增生作用加强了岩石的机械混合作用，导致非等化学变质反应。由于非等化学反应是不可逆的过程，大陆移动的带的岩石学性质在威尔逊旋回后继续发生渐变。

Evolution of the Hida metamorphic belt was discussed from the view point of clinopyroxene mineralogy. Followings are major conclusions.1. Clinopyroxene gneiss of the Hida metamorphic belt was formed by mechanical mixing of metabasite and limestone, thereby the reaction tr+cc+qz=di+H2O+CO2 takes place. Inishi-type rocks include both the product of the mechanical mixing of the rocks and that of dyhydration melting of amphibolite.2. Mechanical mixing of rocks is a major process of metasomatic reaction. This process results in the compositional change of system, and therefore metamorphic reactions due to the difference between the free energy of simple mixture of rocks and that of products take place. This type of metamorphic reactions is of non-isochemical reaction, being in contrast to a general view that metamorphic reactions take place in response to the change of temperature and pressure within isochemical system.3. The concept of non-isochemical reaction extends to fluid bearing systems. We found that the metamorphic reactions by mechanical mixing of rocks results in the abrupt release and compositional change of fluid phases, and consequetly different reactions may occur.4. Mechanical mixing of rocks leading to the non-isochemical metamorphic reactions is enhanced by accretionary process at the leading edge of continents, in other words, continental mobile belts. Since non-isochemical reactions are of irreversible processes, the petrological properties of continental mobile belts continue to be progressively chanced upon Wilson cycle.