河南罗山县母山钼矿床成矿作用特征及锆石LA-ICP-MS U-Pb同位素年代学  

Characteristics of Mo mineralization and zircon LA-ICP-MS U-Pb geochronology of Mushan Mo deposit from Luoshan County,Henan Province

作　　者：杨梅珍[1,2] 曾键年[2] 任爱群[3] 陆建培[2] 潘思东[2] 

机构地区：[1]地质过程与矿产资源国家重点实验室,中国地质大学,湖北武汉430074 [2]中国地质大学,湖北武汉430074 [3]河南省地质矿产勘查开发局第三地质调查队,河南信阳464000

出　　处：《矿床地质》2011年第3期435-447,共13页Mineral Deposits

基　　金：地质过程与矿产资源国家重点实验室开放课题(编号:GPMR201014);河南省国土资源厅2007年度省“两权价款”地质科研计划项目(编号:2882)的资助

摘　　要：母山钼矿床是大别山北缘地区斑岩型钼矿床的典型代表,以发育于花岗斑岩体内、外接触带的细网脉浸染型矿化为特征,并具有以岩体顶部由早期硅化形成的无矿石英核为中心的典型的斑岩热液体系蚀变分带模式。在无矿石英核的石英中,富气相包裹体和含石盐子矿物的三相包裹体共存,说明其原始岩浆流体曾发生过低压相分离。流体包裹体均一温度测试结果表明,成矿热液体系的冷却作用是Mo、Cu等成矿元素沉淀的重要原因。成矿岩体地球化学研究表明,母山成矿花岗斑岩体的特征是,低Sr(<400×10-6)、低Yb(1.8×10-6)、轻、重稀土元素分异强烈〔(La/Yb)N=32.13~68.69〕、Eu负异常中等—较弱(δEu=0.66~0.92)以及较高的(87Sr/86Sr)i值(0.70 962~0.71 076)和较低的εNd(t)值(-14.77^-13.36)。锆石LA-ICP-MS U-Pb同位素精细年代学测试结果显示,母山成矿花岗斑岩的侵位年龄为(142.0±1.8)Ma,表明其是大别造山带碰撞造山后加厚陆壳部分熔融的产物,其成岩成矿时间比大别山地区早白垩世岩浆活动峰期(~130 Ma)早约10 Ma,代表了大别山地区较早的一次钼多金属成矿事件。Mushan Mo deposit,a typical porphyry molybdenum deposit occurs in the northern margin of Dabie Mountain,is characterized by veinlet-disseminated mineralization and typical porphyry hydrothermal system alteration envelope centering the unmineralized quartz core formed by silicification early at the top of granitic porphyry.The coexistence of vapour-rich and halite-bearing three-phase inclusions indicates that the primitive magmatic fluid has experienced phase separation under low pressure.The results of homogenization temperatures of fluid inclusions show that the ore-forming element including Mo,Cu deposited by cooling of ore-forming hydrothermal system.Mushan granitic porpphry related to mineralization exhibits low Sr（400×10-6）,low Yb（1.8×10-6）,strong fractionation of LREE and HREE（（La/Yb）N=32.13～68.69）,moderate to slight Eu negative anomaly（δEu=0.66～0.92）,and high（87Sr/86Sr）i（0.70 962～0.71 076）,extremely low εNd（t）（-14.77～-13.36）.The result of zircon LA-ICP-MS U-Pb geochronology that Mushan granitic porphyry emplaced at（142.0±1.8） Ma.It concluded that rock forming and Mo mineralization of Mushan Mo deposit are resulted from the thickened continental crust by partial melting during post-collision of Dabie Mountain,and it happened nearly 10 Ma earlier than granitic magmatism peak（～130 Ma） in early Cretaceous in Dabie region.

关 键 词：地球化学 细脉浸染型矿化 母山钼矿床 锆石U-PB年龄 河南省 

分 类 号：P618.65[天文地球—矿床学]