【作者】 杨振；

【导师】 王汝成； 张文兰；

【作者基本信息】 南京大学 ， 矿物学、岩石学、矿床学， 2012， 硕士

【摘要】 苗儿山-越城岭地区位于桂北与湘东南交界处。区内成矿条件较好,众多的钨锡矿床(点)主要沿着苗儿山-越城岭复式岩体与地层的接触部位呈环带状分布,是南岭西段最重要的W-Sn成矿带,同时也是研究前燕山期岩浆活动及其成矿作用的首选地。本文在前人工作的基础上,着重选取了处于苗儿山-越城岭复式岩体南缘的牛塘界钨矿和油麻岭钨矿作为研究目标,两个钨矿床的研究程度均不高,特别是还都缺乏有效的成岩和成矿年龄数据。牛塘界钨矿属层状矽卡岩型白钨矿床,岩株状细粒二云母花岗岩在时空上与其有密切的成因联系。本文利用LA-ICP-MS锆石U-Pb原位定年方法,获得花岗岩的侵位年龄为(421.8±2.4)Ma,与相邻的越城岭花岗岩体同属于加里东期岩浆活动产物；首次对矽卡岩中的白钨矿进行了Sm-Nd同位素分析,获得了钨成矿年龄为(421±24)Ma,岩体与成矿作用都发生在加里东期。花岗岩中锆石的εHf(t)值为-6.5～-11.6,Hf同位素两阶段模式年龄为1.79～2.11Ga,表明花岗岩的源区可能为中元古代的地壳物质；矽卡岩中的白钨矿对应的εNd(t)为-13.06～-13.26,其成矿流体也来源于古老的地壳物质。油麻岭钨矿的矿化类型具有多样性,其中外接触带似层状矽卡岩型白钨矿是矿区最重要的矿床类型。本文对矿区成矿母岩中-细粒二云母花岗岩进行了详细的锆石U-Pb年代学和岩石地球化学的研究。LA-ICP-MS锆石U-Pb定年结果表明,年龄为212-215Ma,属印支期岩浆活动的产物。地球化学分析显示,花岗岩具有高硅(Si02=73.73%～78.68%)、富碱(ALK=6.99%～8.36%)、贫Ca(CaO=0.13%～0.96%)、贫Ti(Ti02=0.05%～0.27%)、弱过铝-强过铝质(ACNK=1.03～1.28)的特征,稀土元素总量偏低(∑REE=61.39×10-6161.22×10-6),富集Rb、Cs大离子亲石元素及Th、U、Ta等高强场元素,富成矿元素W(平均含量6.55ppm),贫Ba、Sr,强烈的Eu亏损(8Eu=0.04～0.20)。岩石学和地球化学特征表明成矿母岩与南岭地区典型的高分异S型花岗岩相似,具备了为钨矿的形成提供物源的能力。以上对桂北苗儿山-越城岭地区牛塘界钨矿和油麻岭钨矿的研究,再一次表明了在南岭地区西段确实存在着加里东期和印支期的岩浆活动,且这两次前燕山期的岩浆岩均为矿区钨矿的成矿矿母岩。更多还原

【Abstract】 The Miaoershan-Yuechengling area is located in the border region between Northern Guangxi and Southeastern Hunan. Many W-Sn deposits occurred in the contact zone between the complex pluton and the adjacent strata, forming the most important metallogenic belt in the western Nanling. It is also an ideal place to research pre-Yanshanian magmatism and its mineralization. Based on the previous researches, We selected Niutangjie and Youmaling tungsten deposits as the research goal. These two deposits are all located in the southern margin of the Miaoershan-Yuechengling granitic complex, the extent of their research is still in a very low level, especially, little work has been done on the ages of ore-forming and related granite.Niutangjie tungsten deposit belongs to bedded skarn-related scheelite deposit. The mineralized intrusion, which occurs as small stockwork. is spatially and temporally associated with the scheelite deposit in the orefield. Petrologically, it is fine-grained two-mica granite. Based on LA-ICP-MS zircon U-Pb ages, the Niutangjie granitic pluton emplaced at (421.8+2.4) Ma, similar to the adjacent Yuechengling pluton. Wi--th the use of Sm-Nd isotope analysis techniques in the scheelite for the first time, we acquired the Sm-Nd isochron age (421+24Ma). Although the data error is larger, but it still clearly shows the mineralization epoch is coupled with the emplacement of the magmatism within the error range. Zircon εHf(t) values and Hf two-stage model ages range from-6.5to-11.6and1.79to2.11Ga, which propose the granite was derived from the Mesoproterozoic crustal materials. The εNd(t) values of the scheelite samples range from-13.06to-13.26, which mean the ore-forming fluid are also derived from the ancient crustal materials.The mineralization types of the Youmaling tungsten deposit are diverse, and the main type is stratoid skarn-type scheelite in outer contact zone of the granite. In this study, we carried out a comprehensive research including zircon U-Pb dating; petrology and geochemical studies on the granite related to the tungsten deposit. Petrologically, it is medium-fine grained two-mica granite. LA-ICP-MS zircon U-Pb chronology indicates that the granitic pluton emplaced at212-215Ma, during the Indosinian period. Chemical analyses show that the granite has high SiO2(SiO2=73.73%-78.68%), high alkalies(ALK=6.99%-8.36%), low Ca and Ti (CaO=0.13%-0.96%, TiO2=0.05%-0.27%), and is weakly-strongly peraluminous (ACNK=1.03-1.28); The granite also displays low total REE contents (ΣREE=61.39X10"6-161.22xl0-6), with strong negative Eu anomalies (8Eu=0.04-0.20), and is enriched in Rb, Cs, etc. LILEs; Th, U, Ta, etc. HFSEs and ore-forming element W (averaging6.55ppm), depleted in Ba、 Sr. These characteristics are similar to the typical highly fractionated S-type granites in Nanling region. Our petrological and geochemical data suggest that the granite has the ability to provide material for formation of tungsten depositThe above studies once again have shown that the Caledonian and Indosinian magmatism indeed existed in the western Nanling region and these two pre-Yanshanian magmatic rocks are tungsten ore mineralization host rock.更多还原