斑岩型钼矿床的围岩蚀变

WALL ROCK ALTERATION OF PORPHYRY MOLYBDENUM DEPOSIT

斑岩型钼矿床系花岗斑岩侵入上地壳后反复演化、矿化和蚀变的结果,特别是矿化圈在形成过程中围岩蚀变同时发生。围岩蚀变首先是以细脉状的形式出现,与矿化最为密切的是辉钼矿石英细脉,其次为辉钼矿长英质细脉。围岩蚀变的另一种形式是环绕花岗斑岩岩株上部产生的的蚀变带,从内向外分别为强硅化蚀变带、强矿化蚀变带、矿化带外的边缘蚀变带3个带。主要工业矿体即产于强矿化蚀变带内。蚀变类型主要为硅化和钾化,硅化主要产生大量的含钼石英细脉,钾化则包括钾长石化、黑云母化及绢云母化。蚀变阶段到强烈硅化阶段,辉钼矿几乎完全从成矿热液中沉淀出来。

Porphyry molybdenum deposits are the result of repeated evolution,mineralization and alteration of granite porphyry after intrusion into the upper crust. Especially,the alteration of surrounding rock occurs simultaneously in the process of mineralization. Wall rock alteration first appears in the form of veinlets,closely related to mineralization is molybdenite quartz veinlets,followed by molybdenite felsic veinlets. The other form of wall rock alteration is the alteration zone around the upper part of granite porphyry rock,which is composed of three zones: strong silicification alteration zone,strong mineralization alteration zone and edge alteration zone outside the mineralization zone. The main industrial ore bodies occur in the zone of strong mineralization alteration. The alteration types are mainly silicification and kalitization,which mainly produce a large number of molybdenum-bearing quartz veinuli,while kalification includes feldspathization,biotization and sericitization. From alteration stage to strongly silicification stage,molybdenite almost completely precipitates from metallogenic hydrothermal solution.