碾子沟金红石矿床变质作用特征及其与成矿的关系

碾子沟金红石矿区发生了两次变质作用,第一次距今1862±24.8Ma,变质温压为600-650℃、4～7kPa,使本区岩石普遍发生了变质;第二次较晚,约为晋宁运动后期,变质温压低于第一次,主要使碾子沟组榴闪岩、斜长角闪片岩等岩石中的石榴子石及晋宁期基性岩中的石榴子石、直闪石及钛铁矿不同程度地变质。两次变质作用均与成矿关系密切,第一次使碾子沟组基性岩中约30％的TiO2转变为金红石,第二次使晋宁期基性岩中约50％的TiO2转变为金红石。从两次变质作用波及范围较广来看,本区具良好成矿远景。

METAMORPHIC PROCESS OF NIANZIGOU RUTILE DEPOSIT AND ITS RELATION TO RUTILE MINER

Once two metamorphic events took place where the Nianziguo rutile deposit developed. One occurred 1862±24.8Ma ago at 600℃- 650℃, leading to regional metamorphism of the whole rocks while the other happened, later or in the late stage of the Jinning movement, making not only the garnet of the garnet amphi-bololite and plagioclase hornblendite of the Nianzigou formation but also the garnet, anthophyllite, and il-menite of the Jinning age basic rock, to be metamorphosed to different levels. Either of the two events had a close link to rutile mineralization, the first translating 30% TiO2 of the basic rock of the Nianzigou formation into rutile and the second changing about 50% TiO2 of the basic rock of Jinning age basic rock. The scope of two metamorphic processes was such wide in the study area that a larger range of prospects for rutile formation should exist in the area.