Opaque mineralogy in the alteration zones of ore deposits

摘要

The changing style of opaque minerals during alteration was examined in different type ore deposits. In hydrothermally altered quartz diorite of pyrometasomatic deposits, magnetite is recrystallized into fine and pure magnetite grains. Finally pyrite is formed from them. Around Kuroko deposits, magnetite in dacite lavas is replaced by hematite, and pyrite is formed at advanced hydrothermal stage. In hydrothermal alteration zones of volcanic sulfur deposits, titanomagnetite in andesite lava changes to Ti poor phase, and finally to marcasite. It is shown that the oxidation state of each type ore deposits affects the changing style of opaque minerals.