| 其他摘要 | 粤北地区是我国重要的钨锡多金属产地，区内密集分布有多个钨多金属矿床/点。该区钨成矿作用以石英脉型黑钨矿矿化为主，并有矽卡岩型和蚀变花岗岩型白钨矿化。深入研究该区典型矿床的成矿机理，对于丰富南岭地区花岗岩成岩成矿理论和指导找矿具有重要的理论意义。本文以粤北地区5个典型的石英脉型钨矿（红岭、石人嶂、梅子窝、瑶岭和锯板坑）为研究对象，系统开展了典型矿床地质特征、矿物学、成矿年代学和硫同位素地球化学研究，结合矿区花岗岩类的地球化学和年代学研究，初步探讨了这些典型矿床的成矿时代、区域成矿规律以及钨成矿与区域花岗岩之间的成因联系。论文获得以下几点主要认识：1. 系统的矿物学和详细的电子探针研究表明，粤北石英脉型钨矿中钨主要以黑钨矿的形式存在，红岭钨矿中存在黑钨矿与白钨矿共生现象，并有铌锰矿、（含）钨铌锰矿晶体；锡以锡石、黝锡矿的形式存在，并有两种锡矿物共生现象；钼主要以辉钼矿的形式存在；银主要以种类众多的含银硫铅铋盐类、硫铜盐类矿物形式存在，并有银的独立矿物相及自然银；铋主要以辉铋矿、自然铋以及众多含银铅铋硫矿物形式存在，在红岭钨矿中发现楚碲铋矿。锯板坑钨矿中多浸染状分布的自然铋与方铅矿共生。闪锌矿在各矿床间成分变化较大。2. 红岭、梅子窝、瑶岭钨矿的辉钼矿Re-Os等时线年龄分别为159.1±1.5Ma、157.7±1.4Ma、159.2±2.3Ma；瑶岭钨矿辉钼矿具有较高的普通Os含量（最高可达0.6050 ng/g）；锯板坑钨矿两个主要方向脉组NNW向大脉、EW向细脉带中白云母的40Ar-39Ar坪年龄分别为138.07±1.52Ma和137.93±1.44Ma。这些高精度的年代学结果表明粤北地区存在两期钨成矿作用，早期的钨锡成矿以瑶岭、红岭、梅子窝钨矿为代表，成矿年龄为157-159Ma；晚期的钨锡成矿以锯板坑钨矿为代表，成矿年龄约为138Ma。3. 粤北地区典型钨矿床矿区花岗岩多为中细粒白云母花岗岩、二云母花岗岩，含原生白云母，均为弱过铝-强过铝质高钾钙碱性花岗岩，富硅，分异指数（DI）高。这些花岗岩富集大离子亲石元素和高场强元素Rb、Th、U和Ta，亏损Ba、Nb、Sr、Eu和Ti，弱亏损Zr，具有较低的Nb/Ta、Zr/Hf和较高的Rb/Nb、Rb/Sr比值。早阶段稀土元素配分模式呈右倾型，晚阶段近平坦型，部分样品表现出明显的稀土元素四分组效应，表明粤北钨矿区花岗岩演化过程中普遍经历斜长石及富钛矿物的分离结晶以及强烈的流体-熔体相互作用。梅子窝矿区花岗闪长岩的成岩年龄为457.7±3.1Ma，成岩时代为加里东期，并非梅子窝钨矿的成矿母岩。4．粤北典型钨矿床含矿石英脉与矿区花岗岩在空间上紧密共生，主要产在矿区花岗岩的顶部或者外接触带中；粤北地区钨矿床的主成矿期与区域大规模的花岗岩成岩时代具有一致性，也与南岭地区大规模钨锡成矿作用在同一时期；硫同位素分析结果表明，红岭、石人嶂、梅子窝、瑶岭、锯板坑钨矿硫化物δ34S平均值分别为1.50‰、-5.34‰、-4.65‰、-2.39‰、1.98‰，表明硫主要来自深部岩浆。这些结果暗示，粤北地区钨成矿与区域大规模花岗质岩浆活动一致，形成于区域强烈伸展的地球动力学背景。; Northern Guangdong province is an important region of tungsten-tin ploymetallic deposits in China, where concentrated many tungsten ploymetallic deposits. The tungsten mineralization type in this area consists of mainly quartz vein-type wolframite mineralization, with secondary altered granite-type and skarn-type scheelite mineralization. Intensive study of ore genesis and ore-forming mechanism of typical tungsten deposits in this region might shed lights on the metallogeny and prospecting of tungsten mineralization in whole Nanling region. Five deposits in northern Guangdong, Hongling, Shirenzhang, Meiziwo, Yaoling and Jubankeng vein type tungsten deposits, have been studied. Detailed research in mineralogy, mineralization chronology, sulfur isotopes of the deposits, the major and trace element characteristics of the granites in each mine area, and also the dating of the granodiorite in Meiziwo deposit have been carried out in this paper. 1. Systematic mineralogy and detailed electron probe research show that tungsten is mainly existed in wolframite in vein type tungsten deposits in northern Guangdong, and we found several grains of mangancolumbite and wolframoixiolite and observed a wide range of intergrowth phenomenon of wolframite and scheelite in Hongling deposit. Tin is existed in cassiterite and stannite, and two types of tin minerals intergrowth exists. Molybdenum is mainly existed in molybdenite. Silver is mainly existed in various types of silver bearing Pb-Bi-S and Cu-S minerals, also silver minerals and natural silver. Bismuth is mainly existed in bismuthinite and natural bismuth and numerous Ag-bearing Pb-Bi-S minerals, and several grains of tsumoite was found in Hongling deposit. There are plenty of intergrowth of bismuth and galena disseminated in Jubankeng deposit. The composition of sphalerite in these five deposits varied differently.2. The Re-Os isochorn ages of molybdenite of Hongling, Meiziwo, Yaoling deposits are 159.1±1.5Ma, 157.7±1.4Ma and 159.2±2.3 Ma, and 40Ar-39Ar plateau ages of muscovite of the NNW and EW direction veins of Jubankeng deposit are 138.07±1.52 Ma and 137.93±1.44Ma. These high precision ages show that there are two stages of tungsten mineralization in northern Guangdong, the earlier stage is represented by Hongling, Meiziwo, Yaoling tungsten deposits and the age is 157-159 Ma, while the latter is represented by Jubankeng deposit and the age is 138Ma.3. The granites in the tungsten mine areas of northern Guangdong mostly are medium to fine grain two-mica or muscovite granite, which include protogenesis muscovite, are all weakly to strongly peraluminous high-K calc-alkaline granite, with the same characteristic of silicon-rich, high differentiation index. These granites are rich in Rb、Th, U and Ta, loss of Ba, Nb, Sr, Ti, and tiny loss of Zr, with low values of Nb/Ta, Zr/Hf ratios and high values of Rb/Nb, Rb/Sr ratios. The rare earth distribution patterns of earlier stage granites are right-wing type, while the later are nearly flat type, and part of the samples show REE tetrad effect. These characteristics show that the occurrence of crystallization differentiation of plagioclase and Ti-rich mineral and strong fluid-melt interaction in the granitic magma processes at these tungsten mining areas. Also we have obtained the zircon U-Pb age 457.7 ± 3.1Ma of the granodiorite in Meiziwo mine, showing that the granodiorite is formed in Caledonian and is not the metallogenic granite of Meiziwo tungsten deposit. 4. The W-bearing quartz veins in each tungsten deposit in Northern Guangdong show close space relations with granites in the mine, which mainly locate at the top or outer contact zone of the granites. The main period of tungsten mineralization in northern Guangdong is consistent with the regional large-scale granite formations in this era, and are in the same period with regional large scale tungsten and tin metallogenesis. The average value of δ34S of sulfides in Hongling, Shirenzhang, Meiziwo, Yaoling and Jubankeng deposits are 1.50‰, -5.34‰, -4.65‰, -2.39‰, 1.98‰, which reflect the deep magma source of sulfur. All these show that the large scale W mineralization, consistent with regional granitic magmatism, happens at the strongly extensional geodynamics. |
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