桂东北越城岭—苗儿山地区印支期成矿作用:油麻岭和界牌矿区成矿花岗岩锆石U-Pb年龄和Hf同位素制约  

Indosinian metallogentic activity in Yuechengling-Miaoershan area, northeastern Guangxi: implications from zircon U-Pb ages and Hf isotopic constraint on ore-forming granites in Youmaling and Jiepai deposits

作　　者：程顺波 付建明 马丽艳 蒋桂新 陈希清 卢友月 童喜润[1,4] 

机构地区：[1]武汉地质调查中心,湖北武汉430205 [2]花岗岩成岩成矿地质研究中心,湖北武汉430205 [3]广西壮族自治区二七一地质队,广西桂林541100 [4]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《中国地质》2013年第4期1189-1201,共13页Geology in China

基　　金：中国地质调查局地质大调查项目(1212010981028和1212011120804)资助

摘　　要：油麻岭和界牌矿床是越城岭—苗儿山地区两个钨多金属矿床,规模均达到中型,主要矿体均产在中细粒(斑状)二长花岗岩接触带附近矽卡岩和破碎带中。本研究利用LA-MC-ICP-MS微区原位测试技术,对油麻岭矿化花岗岩和界牌内接触带花岗岩中的锆石进行了U-Th-Pb和Hf同位素分析。结果显示,油麻岭矿化花岗岩锆石U-Pb年龄为(220±1)Ma(MSWD=0.035),界牌内接触带花岗岩锆石U-Pb年龄为(215±1)Ma(MSWD=0.055),间接指示越城岭—苗儿山地区存在印支期成矿作用。油麻岭花岗岩样品εHf(t)值在-2.47^-6.67,界牌花岗岩样品εHf(t)值在-3.52^-6.79,表明这两个矿区花岗岩都是源于地壳物质的重熔。与南岭地区其他成钨花岗岩比较,两者源区均具有高εHf(t)值特征,可能是较多εHf(t)值>0的新元古代新生岛弧地壳组分加入引起的。本文获得及前人发表的印支期同位素年龄表明,桂北地区经历了较强的印支期成岩成矿事件,有较好的找矿前景,今后应注意区内印支期花岗岩出露区的勘查评价工作。Youmaling and Jiepai are two newly-discovered tungsten-tin polymetallic deposits with middle-scale metal resources.Their main ore bodies occur in skarn and fractured rocks adjacent to the fine to medium grained monzogranite contacts.In this paper,in situ LA-MC-ICP-MS technology was employed to measure the UTh-Pb and Hf isotopes of these granites from inner contacts of the Youmaling and Jiepai deposits.Zircon U-Pb isotopic results show that the granites were formed at Ca.220±1 Ma（MSWD=0.035） and 215±1 Ma（MSWD= 0.055） respetively,indicating that Indosinian metallogentic activity took place in Yuechengling-Miaoershan area.ε Hf（t） values of granite from Youmaling vary between-2.47 and-6.67,and those from Jiepai vary between 3.52 and-6.79,suggesting that they were both remelted from crust rocks.In contrast to other tungsten mineralized granites in the Nanling Mountains,the sources of two granites have higher ε Hf（t） values.A appropriate reason is that some Neoproterozoic island arc materials with positive ε Hf（t） values were involved during the remelting of the source materials.Isotopic ages from this paper and previous work indicate that intense Indosinian petrogenetic and metallogentic activities took place in this area.As we all know,fruitful exploration achievements have been obtained in the vicinity of contacts of Indosinian granites in the Nanling Mountains,so more attention must be paid to the exploration and evaluation in this area in the next few years.

关 键 词：印支期 成矿花岗岩 LA-MC-ICP-MS 锆石U-Pb年龄 HF同位素 桂东北 

分 类 号：P597.3[天文地球—地球化学]