A detailed analysis on the generation and alteration hysteresis of high temperature skams

在冈山县福冈和广岛钏路的高温矽卡岩中，辉长岩和辉长岩以原生矿物的形式赋生。矽卡岩是侵入二黄长岩和石英二长岩的石灰岩形成的。这些火成岩似乎是同一岩浆成因的产物。火成岩岩浆的温度影响夕卡岩的类型。地温计测得形成辉长辉长矽卡岩的火成岩温度在690 ~ 930℃之间。辉长岩和辉长岩晶体大部分蚀变为逆行矿物。本研究通过织构分析和化学分析阐明了辉长石晶体的蚀变过程。经详细分析，其蚀变过程按形成顺序依次为：(1)径向蚀变过程（辉长岩蚀变为方解石、埃姆塞特、石榴石和维苏岩）。(2) Ti-Fe相的形成过程（钛矿和钙钛矿的形成）。(3)白岩脉蚀变过程（向维苏岩蚀变）。(4)黑质脉蚀变过程（对不明矿物的蚀变）。(5)分区蚀变过程（向hydrogrossular的蚀变）。

In the high-temperature skarns at Fuka, Okayama Prefecture and Kushiro, Hiroshima Prefecture, spurrite and gehlenite occur characteristically as primary minerals. The skarns were formed by the intrusion into limestone of monzodiorite and quartz-monzonite. The igneous rocks appear to be products of the same magmatic origin. The temperature of the igneous magma affects the type of skarns. The temperatures of the igneous rocks forming the gehlenite-spunite skarns range from 690℃ to 930℃, using the geothermometer. Most of the gehlenite and spurrite crystals were altered to retrograde minerals. In the present study, the alteration process of the gehlenite crystals was clarified by texture and chemical analysis. As a result of detailed analysis, there are five alteration processes in order of formation as follows : (1) Radial alteration process (alteration from gehlenite to calcite, amesite, garnet and vesuvianite). (2) Ti-Fe phases formation process (formation of schoiiomite and perovskite). (3) Leucocratic vein alteration process (alteration to vesuvianite). (4) Melanocratic vein alteration process (alteration to unidentified mineral). (5) Zoning alteration process (alteration to hydrogrossular).