西藏山南地区明则斑岩钼矿床蚀变矿化特征与成矿时代  

Characteristics of Alteration and Mineralization and Chronology of the Mingze Porphyry Mo Deposit in the Shannan Area of Southern Tibet

作　　者：范新[1,2] 陈雷[1,2] 秦克章[1] 肖波[1,2] 李金祥[1] 李秋平[3] 陈玉水[3] 陈金标[3] 赵俊兴[1,2] 李光明[1] 黄树峰[3] 琚宜太[4] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]中国科学院研究生院,北京100039 [3]中国冶金地质总局第二地质勘查院,福建甫田351111 [4]中国冶金地质总局,北京100025

出　　处：《地质与勘探》2011年第1期89-99,共11页Geology and Exploration

基　　金：中国冶金地质总局"冈底斯东段南部矽卡岩-斑岩Cu-Au-Mo矿床成矿条件及成矿模式综合研究";国家自然科学基金项目(编号:40772066)资助

摘　　要：明则斑岩钼矿床位于冈底斯成矿带的东南缘,雅鲁藏布江缝合带北侧。矿区内主要出露有钾长花岗岩、黑云母二长花岗岩、花岗闪长岩、似斑状二长花岗岩及花岗斑岩,其中花岗斑岩为成矿岩体。围岩蚀变较为强烈,主要的蚀变特征有:钾化、硅化、绿泥石化、高岭土化和矽卡岩化,而且各种蚀变现象具有垂向分带特征,其中矽卡岩化主要发育在地表浅部,岩体与地层的接触部位,形成了石榴石、透辉石、绿帘石等矽卡岩矿物,而钾化、硅化等蚀变分布在相对较深的部位。矿化类型主要是斑岩型和矽卡岩型矿化,具有垂向分带的特征,上部是矽卡岩型铜矿化和弱的钨矿化,下部斑岩型的铜钼矿化,其中斑岩型的矿化也具有垂向分带特征,铜矿化分布在相对上部,钼矿化分布在相对靠下的深部区域。矿石主要以块状、细脉浸染状和浸染状为主,矿石矿物主要有辉钼矿、黄铜矿、黄铁矿、白钨矿和少量的斑铜矿。选取钻孔中新鲜的黑云母二长花岗岩中穿插的黑云母-黄铁矿脉,对其中的黑云母进行40Ar-39Ar定年,得到坪年龄为28.2±0.33Ma,该年龄值与辉钼矿的Re-Os年龄相吻合。同时结合冈底斯南带上已知的成矿时代,说明整个冈底斯东段南带的成矿时代可能是介于30.26～23.62Ma之间,这明显不同于冈底斯东段北带和中带的斑岩型或斑岩-矽卡岩型矿床,说明在冈底斯成矿带东部除发育有后碰撞阶段的斑岩型铜(钼)或铜多金属矿床外,还发育有晚碰撞阶段的成矿作用。对明则斑岩钼矿成矿时代的厘定,为深入研究冈底斯成矿带的多期次成矿及冈底斯成矿带与板块俯冲到碰撞再到碰撞后伸展的构造岩浆活动有关的成矿演化过程提供了有力的支持。The Mingze porphyry Mo deposit is located in the southeastern margin of the Gandese metallogenic belt,north of the Yarlung Zangbo River suture zone.A variety of intrusions outcrop such as moyite,biotite monzogranite,granodiorite,porphyaceous adamellite and granite porphyry.The granite porphyry is the ore-froming related intrusion which is completely mineralized.Wall rocks suffered extensive alteration,mainly as potassic,silicification,chloritization,kaolinization and skarn alteration.Various types of alteration have the characteristics of vertical variations,and skarn formed where the intrusions interact with carbonate wall rocks.Potassic and silicification alteration occurred at deeper levels.Mineralization of the Mingze deposit also shows vertical variation.Cu and W mineralization in skarn formed in the relatively shallow subsurface,and Mo（Cu）mineralization in porphyry occurred at larger depths.Porphyry mineralization has vertical zoning characteristics.Texture of ores mainly includes massive,veinlet and disseminated form.Ore minerals mainly consist of molybdenite,chalcopyrite,pyrite and a little of bornites and scheelit.We selected pure biotite for the 40Ar-39Ar dating from the biotite-pyrite vein.The results show the plateau age is 28.2±0.33Ma,which coincides with the age of Re-Os.Combined with metallogenetic age previously reported,this age represents the metallogentic age of the southern belt of Gangdese between 30.26Ma-23.62Ma,which is obviously different from the northern or middle belt of the Gandese metallogenic belt.Dating of the metallogenic epoch of the Mingze deposit provides sound evidence for the multi-stage mineralization and the evolution of ore-forming related to the extensive tectono-magmatic activities.

关 键 词：蚀变矿化特征 明则斑岩Cu(Mo)矿40Ar-39Ar年代学 成矿时代 冈底斯南缘 

分 类 号：P618.51[天文地球—矿床学]