【作者】 冯佳睿；

【导师】 裴荣富； 毛景文；

【作者基本信息】 中国地质科学院 ， 矿产普查与勘探， 2011， 博士

【摘要】 滇东南老君山是我国一个重要的锡钨多金属成矿区,己发现矿种26种以上,这些矿床主要分布在南秧田-茶叶山(W)、大竹山-新寨(Sn-W)、曼家寨-铜街(Sn-Zn)三个矿集区,矿床成因类型主要为矽卡岩型。本论文在前人研究成果的基础上,选择南秧田白钨矿矿床进行系统研究,重点进行了矿床地质特征、流体包裹体、稳定同位素、成岩成矿年代学及综合分析对比等方面的研究,探讨了成矿流体来源、演化、矿床成因及成矿动力学背景,并将南秧田与新寨矿田、南秧田与都龙矿田分别进行了对比研究,取得了如下成果：1.滇东南老君山锡钨多金属成矿区属于滇东南-桂西锡钨多金属成矿带,大地构造位置位于滨太平洋构造域,华南褶皱系越北隆起北缘。赋矿地层主要为寒武系变质岩系,主要岩性为片岩、二云二长片麻岩、斜长片麻岩、变粒岩等；岩浆岩主要为酸性-基性火山岩和酸性侵入岩,区域构造以NW向、NS向和EW向断裂为主。2.对南秧田白钨矿矿床西侧的老君山花岗岩体进行了LA-ICPMS锆石U-Pb测年、地球化学特征、岩石学等方面的研究。三期岩体的LA-ICP-MS锆石U-Pb年龄分别为87.2±0.6Ma、86.8±0.4Ma和85.9±0.4Ma。老君山花岗岩体的岩石地球化学特征为强过铝质、富硅、富碱,铝饱和指数A/CNK范围为1.10～1.38；岩体的哈克图解表明在岩浆演化过程中岩体经历了强烈的分离结晶作用;岩体富集Rb、La、Zr等大离子亲石元素,强烈亏损Ba、Sr、Ti等不相容元素；稀土元素球粒陨石标准化配分曲线呈均一趋势,并发育明显的负Eu异常；岩体源岩来源于陆壳物质的部分熔融。3.南秧田白钨矿矿体主要赋存在下寒武统冲庄组变质岩系中。矿体形态简单,主要呈层状和似层状产出,空间上与矽卡岩密切相关。矿石类型主要为矽卡岩白钨矿型。矿床的形成经历了4个成矿阶段,分别为矽卡岩阶段、退化蚀变阶段、石英硫化物阶段和方解石硫化物阶段。白钨矿主要形成于退化蚀变阶段。4.南秧田钨矿床流体包裹体主要有三种类型：富液相包裹体、富气相包裹体和含子矿物多相包裹体。包裹体气相成分以H2O、CH4和N2为主,含少量C02,液相成分以H20为主。成矿早期流体包裹体均一温度分布于200～340℃,盐度ω(NaCleq)为6.45～53.26％,流体密度范围为0.83-1.15g/cm~3；成矿晚期均一温度主要集中于160～300℃,ω(NaCleq)主要介于4-8％,流体密度变化于0.67-0.96g/cm~3,与早期相比,温度、盐度和密度明显降低。5.石榴石、石英和方解石的δ18 OsMOW值变化于3.78‰～16.23‰,δ~18OH2O值介于4.52‰～10.28‰,δD值为-83‰0～59‰,说明成矿流体主要为岩浆水,可能混合少量变质水；矿石中方铅矿的铅同位素组成较为一致,206pb/204pb变化范围为18.5301～18.5325,207pb/204pb变化范围介于15.7332～15.7369,208pb/204pb变化范围为39.0456～39.0587,表明矿石铅的来源较浅,成矿物质以壳源为主；634S值变化范围集中在4.2‰～8.1‰,表明硫源主要来自地幔,但受到地壳混染影响。6.选取南秧田白钨矿矿床矿石中辉钼矿和新寨锡矿床中与锡石共生的金云母为研究对象,分别运用Re-Os同位素定年和40Ar-39Ar阶段加热方法进行成矿年代测定。研究表明,辉钼矿Re-Os年龄为209.1±3.3Ma～214.1±3.1Ma,金云母40mr-39A1.坪年龄为209.5±1.1Ma,等时线年龄为209.0±2.2Ma,暗示华南地区存在晚三叠世成矿作用。7.南秧田钨矿区钨的成矿作用可能与热液叠加作用有关。老君山花岗岩体是较晚期形成的部分岩体,可能还有未被发现的较早期形成的“体中体”。矿床形成于印支期后造山晚期或后碰撞阶段,它们的形成受控于拉张－裂解的动力学背景。8.南秧田矿田与新寨矿田它们在地层、矿体特征、成矿流体及成矿时代等方面有一定的相似之处：(1)主要出露的地层均为寒武系变质岩系；(2)钨、锡矿体均顺层呈层状产出,产状与围岩基本一致；(3)流体包裹体均一温度变化范围较大,盐度普遍较低；(4)矿化作用均发生于印支期晚三叠世末；南秧田矿田与都龙矿田在地层、岩体控矿因素、构造控矿因素及成矿时代等方面有一定的差异性。9.区域主要的控矿构造为北西向构造、南北和东西十字型构造、老君山褶皱构造、岩浆侵入接触构造和层间滑脱构造。更多还原

【Abstract】 Laojunshan is an important Sn-W-related metallogenic province in Southeastern Yunnan where more than 26 Sn (W) deposits have been explored, locating at the ore concentration areas named Nanyangtian-Chayeshan, Dazhushan-Xinzhai, Manjiazhai-Tongjie, respectively. The main genetic type of ore deposit is skarn type. Based on the pervious researchers and detail field investigation, we selected the Nanyangtian deposit to conduct the detail study. Focusing on the geological characteristics, fluid inclusions, stable isotope, chronology and synthetically comparative study etc., in order to clarify the source and evolution of ore fluids, deposit genesis and geodynamic settings, and compare Nanyangtian with Xinzhai and Nanyangtian with Dulong, respectively. The main advance achievements from this study are as follo wings:1.The Laojunshan area occurred in Southeastern Yunnan-Western Guangxi tin-tungsten polymetallic ore belt. Its geotectonic position locates at Peri-Pacific tectonic domain, and the northern margin of North Vietnam in South China fold system. The host rocks are Cambrian metamorphic rocks, comprising of schist, two-mica monzonitic gneiss, plagioclase gneiss, leptynite. The major types of magmatic rocks are the felsic-basic volcanic rocks and felsic intrusive rocks. The main regional structure are the NW-trending, NS-trending and EW-trending faults.2. In this paper we report zircon U-Pb ages, geochemical and petrological characteristics for the Laojunshan granites located in the western part of Nanyangtian tungsten deposit. Three samples from three phases of the granitic rocks in Laojunshan intrusion have been analyzed by the LA-ICPMS zircon U-Pb techniques, yielding ages of 87.2±0.6Ma, 86.8±0.4Ma and 85.9±0.4Ma, respectively. Bulk analysis reveals that three phases are strongly-peraluminous, silicon-rich and alkali-rich granites and their ACNK values fall mainly into a small range of 1.10-1.38. Moreover, Harker diagrams show that these granitoids experienced strong fractional crystallization during magmatic evolution. All granites show enriched Rb, La and Zr and depleted Ba, Sr and Ti, as well as a uniformly flat REE-pattern with a marked negative Eu anomaly. The granites were possibly derived from partial melting of continental crust.3. The Nanyangtian tungsten deposit occurs in metamorphic rocks of the Lower Cambrian Chongzhuang Formation. Ore bodies, with the simple shape, are largely concordant with the bedding of the strata and the distribution of the ore bodies is spatially related to skarn. The main ore type is skarn-scheelite. The formation of tungsten deposit experienced a period composed of skarn stage, retrogressive alteration satge, quartz-sulfide stage and calcite-sulfide stage. Tungsten mineralization is probably in the retrogressive alteration satge.4. There are three dominant types of fluid inclusions, as evidenced by petrography characteristic of fluid inclusions of garnet, epidote, quartz, fluorite and calcite formed at different ore-forming stages in the Nanyangtian tungsten deposit; they are liquid-rich inclusions, gas-rich two-phase inclusions and daughter-minerals bearing polyphase inclusions. Systemic measurements of homogeneous and freezing temperatures, salinities and laser Raman spectroscopic analysis of fluid inclusions were conducted. The gas composition of ore-forming fluids in the Nanyangtian tungsten deposit mostly are H2O, CH4 and N2, with a small amount of CO2, whereas liquid composition primarily is H2O. Fluid inclusions in early stage show a range of homogenization temperatures and salinity from 200℃to 340℃and from 6.45% to 53.26 wt% NaCleqv respectively, with the densities ranging from 0.83 to 1.15g/cm3. Homogenization temperatures and salinity of fluid inclusions in late stage mainly vary from 160℃to 300℃and from 4% to 8 wt% NaCleqv respectively, and the density of the fluids is 0.67-0.96g/cm3, which are obviously lower than the fluid inclusions in early stage.5. Theδ18OSMOW values of garnet, quartz and calcite range from 3.78‰to 16.23‰, with the correspondingδ18OH2O values between 4.52‰and 10.28‰, and 8D values of fluid inclusions between-83‰and-59‰. The combined isotopic data imply that the ore-forming fluids in the Nanyangtian tungsten deposit were mainly derived from magmatic fluids, with a minor part from the metamorphic water. Theδ34S values of pyrite from the Nanyangtian tungsten deposit define a narrow range of 4.2%o-8.1‰, reflecting the characteristics of the sulfur from mantle source, with the affect of crustal contamination.6. We present Re-Os dating of three molybdenite samples separated from the Nanyangtian tungsten deposit and new 40Ar-39Ar phlogopite closely coexisting with cassiterite ages for the Xinzhai tin deposit to constrain timing and duration of mineralization. The Re-Os model ages were obtained ranging from 209.1±3.3Ma to 214.1±4.3Ma; Phlogopite from the Xinzhai tin deposit yielded a 40Ar-39Ar pleatu age of 209.5±1.1Ma and isochronal age of 209.0±2.2Ma. The ages above provided the mineralization information during the Indosinian in southeastern Yunnan.7. The mineralization in Nanyangtian tungsten deposit may be related to hydrothermal superposition. Laojunshan granite is the later formed part of the rock, there may be the earlier undetected "body in body". The Sn and W mineralization were formed in late post-orogenic or post-collisional stage during the Indosinian in Southern China and controlled by a geodynamic setting of the extension-cracking.8. There are some similarities between the Nanyangtian and Xinzhai in the following aspects:the formation in mining area, ore body characteristics, ore-forming fluid and metallogenic epoch. (1) The main exposed strata are the Cambrian metamorphic rocks; (2) The tungsten-tin ore bodies are basically concordant with the bedding of the strata, with the same shape of the rock; (3) Fluid inclusions generally have widely varying homogenization temperatures and low salinity; (4) The mineralization of the Nanyangtian and Xinzhai both occurred in the Late Triassic during the Indosinian; There are differences between Nanyangtian and Dulong in the following areas:the strata, ore-controlling rock, ore-controlling structure, mineralization age.9. The main ore-controlling structures in region are NW-trending faults, NS-EW-trending cross-type structure, Laojunshan fold, magmatic intrusive contact structure and interlayer detachment structure.更多还原