广东河台金矿假玻状岩的形成机制及其与成矿的关系

THE FORMATION MECHANISM OF PSEUDOTACHYLITE AND ITS RELATION TO MINERALIZATION IN HETAI GOLD MINE, GUANGDONG

河台金矿假玻状岩的形成是碎裂机制、熔融机制和隐爆机制三者共同作用的结果，这是假玻状岩成因理论研究的重大进展。河台假玻状岩的原岩是糜棱岩。与糜棱岩的化学成分对比，假玻状岩具有ＳｉＯ２，Ｎａ２Ｏ含量减少，Ｋ２Ｏ，Ａｌ２Ｏ３，ＭｇＯ，ＦｅＯ含量增加的规律，但稀土配分型式保持不变。假玻状岩形成时间晚于糜棱岩，且形成于与碎裂岩相关的脆性变形域。假玻状岩事件发生在早期韧性成矿作用之后，晚期脆性成矿作用之前。其对早期韧性成矿没有控制作用，但对晚期脆性成矿具有明显的“屏蔽”控矿作用。假玻状岩可作为良好的找矿标志之一。

The pseudotachylite was formed by three mechanisms: comminution, melting and hidden explosion in Hetai Gold Mine, Guangdong. This is a significant advancement of study on the origin of pseudotachylite. The protolith of psedotachylite is mylonite. Comparing to mylonite, pseudotachylite is characterized by the decrease on SiO 2 , Na 2 O and the increase on K 2 O, Al 2 O 3 , MgO, FeO, but the REE pattern remains unchanged. Pseudotachylite was generated after mylonitization in brittle regime related to cataclasis. The pseudotachylite event occurred after earlier ductile mineralization and before later brittle mineralization. Pseudotachylite, which had no control on earlier ductile mineralization, controlled the later brittle mineralization by 'screening' process. It can be used as one of the best prospecting indicators.