新疆东准噶尔贝勒库都克锡矿带锡成矿的40Ar-39Ar年龄

位于新疆东准噶尔的贝勒库都克锡矿带是我国北方地区首次发现具独立锡矿床的锡成矿带。该成矿带自东向西发育萨惹什克、贝勒库都克、干梁子、卡姆斯特4个独立锡矿床。它们在主要矿石类型、脉石矿物组成上表现为两类。萨惹什克锡矿属于石英型,占优势的脉石矿物是石英,其次有长石,而白云母很不发育。其它3个锡矿则以云英岩型为特征,主要脉石矿物是石英和长石,次要矿物有白云母。本文报道了我们对发育白云母的卡姆斯特、干梁子、贝勒库都克锡矿床开展矿石⁴⁰Ar-³⁹Ar同位素定年的结果。3件与锡石平衡共生的白云母有很平坦的年龄谱,其⁴⁰Ar/³⁶Ar-³⁹Ar/³⁶Ar正等时线年龄与各自的坪年龄很一致,年龄值范围是305~315Ma。这些结果和我们已报道的萨惹什克锡矿的Re-Os等时线年龄一起,确定了全部4个锡矿床的成矿年龄,并证实它们构成一个锡成矿带。此外,锡矿石与花岗岩围岩年龄的一致性表明了研究区锡成矿与花岗岩浆作用间很可能存在成因关系。     

新疆东准噶尔贝勒库都克锡矿带成岩和成矿的年代学研究

新疆东准噶尔的贝勒库都克锡矿带是我国北方地区首次发现具独立锡矿床的锡成矿带,自西向东依次发育卡姆斯特、干梁子、贝勒库都克、萨惹什克4个独立锡矿床[1].     

新疆东准噶尔锡矿找矿的新进展

新疆东准噶尔地区继1986年、1987年发现贝勒库都克、萨惹什克两处锡矿之后,又发现卡姆斯特(喀拉萨依)锡矿及红土井子、苏吉泉锡矿(化)点。1988年新疆国家305项目Ⅳ-17课题组发现了干梁子锡矿与苏吉泉锡矿,使找锡矿取得新的突破。贝勒库都克、萨惹什克、卡姆斯特三处锡矿经钻探验证达到成型矿床,干梁子锡矿今年上钻验证,苏吉泉锡矿待进一步工作。东准噶尔地区锡矿的发现不仅首次在我国     

东昆仑祁漫塔格地区白干湖钨锡矿田白云母~(40)Ar/~(39)Ar定年及地质意义

东昆仑祁漫塔格地区白干湖钨锡矿田是认识中国西北地区钨锡矿床成矿规律的重要窗口。作者对采自含矿石英脉的2个白云母样品进行40Ar/39Ar定年,获得其坪年龄分别为(422.7±4.5)Ma和(421.8±2.7)Ma。2个样品的等时线年龄与反等时线年龄也在误差范围内一致,分别为(424±15)Ma和(418±24)Ma,表明分析数据可信。获得的白云母40Ar/39Ar坪年龄指示成矿作用发生在晚志留世,与原特提斯洋闭合事件密切相关,闭合后的陆陆碰撞使富含成矿物质的变质沉积物重熔而形成花岗岩浆;花岗岩浆侵入并析出含矿热液,导致钨锡成矿。     

桂东北水岩坝钨锡矿田白云母40Ar-39Ar年代学研究及其地质意义

水岩坝钨锡矿田位于桂东北姑婆山花岗岩体西南边缘,其成矿作用与姑婆山花岗岩体密切相关。为精确厘定其成矿年代,本文首次对烂头山矿床含钨石英脉中的白云母进行了40 Ar-39 Ar测年,获得白云母坪年龄为162.5±1.2 Ma,相应的等时线年龄为162.0±1.9Ma。表明其成矿年龄为162Ma左右,与姑婆山花岗岩体主体年龄一致,为燕山早期岩浆作用的产物。该成果为深入认识桂东北钨锡成矿年代学格架及成矿动力学背景提供了新的年代学证据。     

广西珊瑚钨锡矿床含钨石英脉中白云母40Ar-39Ar年龄及其地质意义

广西珊瑚钨锡矿床是中国南岭钨锡成矿带内的典型矿床之一,其矿石类型主要为钨锡石英脉型、钨锑萤石石英脉型及含钨石英角砾脉型等3种.本研究对采自该矿床长营岭75中段和35中段含钨石英脉的2件白云母样品进行了40Ar-39Ar快中子活化年龄测定,获得白云母的Ar-Ar坪年龄分别为(100.8±0.7)Ma和(102.7±1.7...     

新疆祁漫塔格柯可卡尔德钨锡矿床控矿构造及 40Ar-39Ar年代学研究

位处新疆东昆仑祁漫塔格地区的白干湖是中国西部最新探明的一个具超大型远景规模的钨锡矿田,柯可卡尔德是其中勘查程度最高、规模最大的钨锡矿床.文章在对柯可卡尔德钨锡矿地质特征详细野外调研和剖析的基础上,重点开展了控矿构造和白云母40Ar-39Ar定年研究.结果表明,该矿区内构造活动强烈且具多期次性,可划分为成矿前向西右旋剪切构造、成矿期以NE向为主的左旋张扭性断裂和成矿后近SN向正断层性质断裂等3期.应用白云母40 Ar-39 Ar同位素测年技术,分别测得了强云英岩化钨锡矿化花岗岩脉内白云母的积分年龄为(411.7±2.6) Ma,等时线年龄为(411.8±4.7) Ma(n=8,MSWD=0.21);黑钨矿-石英脉垂直脉壁生长的片状白云母的积分年龄为(412.8±2.4) Ma,等时线年龄为(414.6±3.9) Ma(n=10,MSWD=0.22),厘定了该矿床的成矿时代为晚志留世,认为其形成于东昆仑地区加里东造山旋回的后碰撞构造阶段.     

云南个旧老厂细脉带型锡矿白云母40Ar-39Ar年龄及其地质意义

细脉带型锡矿是云南个旧矿田老厂矿区的主要矿床类型之一.文章利用40Ar-39Ar同位素测年方法对老厂细脉带型锡矿床白云母-电气石-石英脉中的白云母进行了年龄测试.结果显示,该白云母的40Ar-39Ar同位素坪年龄为(827±07)Ma,表明其形成时代为晚白垩世.进一步结合区域资料,指出包括个旧锡多金属矿床在内的右江褶皱带内与岩浆作用有关的矿床具有相同的成矿地质背景,为华南晚中生代岩石圈大规模伸展的产物.     

湖南芙蓉锡矿床锡矿石和有关花岗岩的40Ar-39Ar年龄及其地球动力学意义

在研究和介绍湖南芙蓉锡矿矿床地质特征的基础上,对云英岩型锡矿石中的白云母和与成矿有关的骑田岭角闪黑云花岗岩中的黑云母进行了40Ar-39Ar年龄测定,获得角闪黑云花岗岩的坪年龄为(157.5±0.3)Ma;三门云英岩锡矿石的坪年龄为(156.1±0.4)Ma;淘洗窝云英岩锡矿石的坪年龄(160.1±0.9)Ma.这3组测年数据很一致,不仅精确地反应出成岩成矿的时间限制,而且表明了花岗岩成岩与锡矿成矿的密切关系.此外,三组数据坪年龄一致显示出,在成岩成矿之后矿体未受到后期热事件的扰动.芙蓉锡矿床是湘南大型钨锡多金属矿集区的组成部分,也是华南地区中生代钨锡成矿两大高峰期之一的160～135 Ma期间形成的代表性矿床,可能为中国东部地球动力学体制调整时晚期岩石圈减薄过程中的产物.     

广西珊瑚钨锡矿床成矿年代学研究及其地质意义

珊瑚钨锡矿床位于富贺钟钨锡多金属成矿集中区的中部,是南岭钨锡多金属成矿带内典型的热液石英脉型矿床之一。本文采用白云母~(40)Ar-~(39)Ar法和石英流体包裹体Rb-Sr法,对矿床V32号含矿石英脉进行精细年代学研究,获得石英脉中白云母~(40)Ar-~(39)Ar坪年龄为101.7±0.7 Ma(MSWD=0.34),正等时线年龄为102.0±1.0 Ma(MSWD=1.17);石英流体包裹体Rb-Sr等时线年龄为106.4±3.5 Ma(MSWD=0.83)。它们在误差范围内一致,是华南地区燕山晚期成岩成矿高峰期的产物。同时通过石英包裹体H-O同位素组成的初步分析,认为成矿流体属于"再平衡岩浆水",主要来自岩浆,在矿床深部可能存在隐伏花岗岩体。该成果对研究区域成矿规律,指导类似地区的找矿勘查工作具有重要意义。     

The tin zone: sediment-hosted hydrothermal tin mineralization at Rooiberg,South Africa

The Rooiberg tin field, also known as the Rooiberg Fragment, is located within the western lobe of the Bushveld Complex. The fragment is triangular-shaped, consists of early Proterozoic Transvaal Sequence volcano-sedimentary rocks, and is surrounded by granitoid intrusives of the Lebowa Granite Suite. Practically all the significant tin deposits are hosted by arkoses, located towards the transition with shaly arkoses at the stratigraphic top of the Boschoffsberg Quartzite Member. This stratabound distribution of individual deposits gave rise to the concept of a regionally developed continuous stanniferous zone. On regional scale, the individual deposits are broadly similar and are collectively classified as replacement and open space-filling type. Particular styles of mineralization such as tourmaline pockets/orbicules, disseminated cassiterite, steep and flat dipping sulphidic fractures and hydrothermal carbonate breccias appear to dominate each mine. Petrological and geochemical investigations of four mineralized centres, indicated the presence of a 500–600 m thick stratified zone of pervasively altered clastic sedimentary rocks of possible arkosic precursor composition. Alteration displays a distinct zonal distribution consisting of a grey-green sodic (albitized) foot wall, an approximately 80 m transitional sericitized-tourmalinized sulphidic tin zone and red hematitic potassic hanging wall. The observed zonal pattern and localization of economically significant cassiterite, is explained by the evolutionary path of magmatic stanniferous hydrothermal fluids genetically related to the surrounding acid phase of the Bushveld Complex. Areas of high fracture density, the tectonic focal points, acted as conduits for the ascending reactive fluids. Factors such as fluid-lithostatic pressure equilibration, limited fracture evolution and/or impermeable shaly arkose retarded this ascent. As a result accumulation, lateral spreading of fluid and pervasive alteration occurred over a broad stratified front. Lateral overlapping of these fronts creates the impression of a continuous tin zone. Abundance of geochemical common denominators between the various focal points (mines) supports a shared composition and source for these contemporaneous fluids.     

The Pemali tin deposit,Bangka, Indonesia

The Pemali tin deposit is located in a Triassic granite pluton the magmatic evolution of which is characterized by a decrease of compatible Ca, Mg, Ti, P and Zr in the sequence: medium- to coarse-grained biotite granite, megacrystic medium-grained biotite granite, two-mica granite/muscovite granite. The tin mineralization is confined to the two-mica granite and consists of disseminated cassiterite as well as greisen-bordered veins. The highly evolved muscovite granite is tin-barren and is distinguished from the two-mica granite by its low mica content and low loss-on-ignition values. The fluid inclusions in quartz and fluorite of the two-mica granite and of the greisen homogenize in the 115–410 °C temperature range; the salinities are in the range of 0.4–23 equiv wt% NaCl and the CO₂ concentrations are < 2 mole%.     

Tin-bearing minerals at the Furong tin deposit,South China: Implications for tin mineralization

It remains poorly constrained whether remobilization of Sn from granites and prograde skarns plays an essential role in forming economic (skarn-type) tin mineralization. Using both electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry methods, in-situ Sn contents, as well as major elements, were analyzed for numerous silicates and magnetite from fresh granite, altered granite, and skarn at the large Furong Sn deposit (530,000 t Sn @ 0.8% Sn) in the Nanling Range, South China. Hornblende and biotite in fresh granite are the main Sn-bearing phases (Sn = 44–321 ppm), while plagioclase and K-feldspar are poor in Sn (< 5 ppm). In altered granite, tin is hosted mainly by hydrothermal muscovite (299–583 ppm) replacing plagioclase, but rarely by chlorite (mostly <10 ppm) replacing hornblende and biotite. In contrast, most silicates (garnet, diopside, vesuvianite, pargasite and epidote) and magnetite from tin skarn are Sn-rich (47–44,241 ppm), except for Sn-poor phlogopite and scapolite (< 10 ppm). In particular, garnet, pargasite, and epidote reach tin concentrations in the percent range. Tin generally enters the stannous silicates and magnetite through substitutions for octahedral Al^vi and Fe³⁺. Comparisons of Sn contents between magmatic and hydrothermal minerals in granite, prograde and retrograde minerals related to tin skarn indicate that remobilization of Sn from granite and prograde skarn is not a pre-requisite to form tin mineralization.     

广东长埔—吉水门锡矿带某些成矿规律和矿床成因

广东长埔—吉水门锡矿带内的锡矿床(点)几乎毫无例外地赋存于下侏罗统金鸡群第二亚群中,锡矿带的展布格局和矿体的形态、产状等特征说明,锡矿受地层层位控制。锡矿带受莲花山断裂带的次一级断裂制约,矿床、矿体主要产于NE-NEE向层间滑动断裂及其派生裂隙中,锡矿具有构造定位的特征。矿床一般经历了早、晚两个成矿期,第一成矿期发生于晚侏罗世火山作用之前,第二成矿期形成于晚侏罗世末期至早白垩世。成矿物质是多来源的,但主要来自地层。金鸡群地层富含锡等成矿组分,是重要的矿源层。成矿溶液以变质水为主,并有大气降水混入。锡矿床属沉积-变成层控矿床。     

Unusual sphalerite,chalcopyrite, and stannite intergrowths at tin deposits

Unusual intergrowths of sphalerite, chalcopyrite, and stannite have been described in two samples from the St. Agnes (Cornwall) and Sinancha (southern Primorye) tin deposits. Possible origins of these sulfide intergrowths and their implications for understanding the formation conditions of the deposits are discussed on the basis of ore microscopy and analytical data. At the St. Agnes deposit, the intergrowths appeared due to the breakdown of a high-temperature solid solution with formation of a Zn-stannite matrix, chalcopyrite lamellae, and rounded drop-shaped inclusions of sphalerite. At the Sinancha deposit, the rare myrmekite stannite-sphalerite intergrowths are interpreted as eutectic textures of mutual penetration that resulted from ore metamorphism at the contact of a dike.     

Compositional characteristics of wolframite in tin deposits,Dupangling, Guangxi

Statistical data on major, trace and rare-earth elements in wolframite from the quartz vein-and greisen-type tin deposits in the Dupangling orefield reveal: (1) The components in wolframite can be divided into two relatively independent groups: the WO₃-Nb-Ta-Sc-REE group, in which WO₃ is negatively correlated with the others and the FeO-MnO-Sn group, in which MnO is negatively correlated with the other two; (2) In general, REE fractionation is not significant, reflected mainly by the separation of Eu from other REE’s. LREE and HREE increase or decrease simultaneously, with HREE being more variable; (3) Nb, Ta, Sc, REE substitute for W, and Sn may enter into wolframite lattice accompanied by Fe-Mn substitution; (4) In contrast to wolframite in quartz veins, which is poor in REE, Nb, Ta and Sc and has highδ Eu values and LREE / HREE and Nb/Ta ratios, wolframite in greisen is rich in REE, Nb, Ta, Sc and has lowδ Eu values and LREE/HREE and Nb/Ta ratios; and (5) The contents and ratios of trace elements and REE partitioning parameters of wolframite can be used as guide for prospecting.     

Formation of the strata-bound Kellhuani tin deposits,Bolivia

A magmatic-hydrothermal model of tin ore formation can best explain the geological, petrographical and geochemical data on the strata-bound Kellhuani tin district. The tin specialization of the magmatic system of the Chacaltaya porphyry stock, centered in the Kellhuani mining area, is the result of advanced fractional crystallization. The regional tin background of the least fractionated members of the Cordillera Real granite series and of their sedimentary country rocks corresponds to average crustal tin contents.Dedicated to Prof. H.-J. Schneider on the occasion of his 60th birthday     

Metallogenesis of a B-F-metasomatic skarn tin deposit,Gejiu, Yunnan Province

Recently, a new type of skarn tin ore formed by B-F-metasomatism has been found in the central part of the Malage ore field at Gejiu, Yunnan Province, which contains 1–7% Sn. The principal tin minerals are nordenskiöl dine, schoenfliesite, varlamoffite, etc., accounting for about 4%. Cassiterite is rarely seen (less than 0.2%). Outward from endoskarns are distinguished four alteration zones, ore fluids were rich in Al and Si in the early stage of skarnization, and became enriched in Fe, Mg, Sn, B, F, H₂O, etc. in the later stages. Two episodes of hydrothermal metasomatism of B and F took place during post-skarnization, and the different alteration zones may be due to reaction between B-and F-bearing hydrothermal solutions and country rocks (calcareous carbonates). The stability of tin minerals is controlled by μB₂O₃, μCO₂,μF₂O_-1 and μF(OH)_-1. It has been concluded from the discussion in terms of the system CaO-SnO₂-SiO₂-H₂O-B₂O₃-CO₂-F₂O_-1 proposed by Burt (1978) and the topological diagrams constructed by the author that nordenskiöldine was formed in the depletion of Si at about 400°C in the skarn environment, where metallogenetic conditions are characterized by rich oxygen but poor sulfur, and high boron but low fluorine, while schoenfliesite and varlamoffite were formed at the lower temperature (about 150°C) in response to hydrothermal metasomatism of fluorine. In comparison with the metallogenetic conditions for adjacent endoskarn tin ores and other tin ore deposits at Gejiu, the role of the characteristic elemental association Sn-B-F is emphasized in this paper.     

滇西松山锡矿锡石LA-SF-ICP-MS U-Pb年代学及其对区域锡成矿作用的指示

松山锡矿位于滇西临沧花岗岩基的西北侧。矿体主要赋存于临沧黑云母二长花岗岩与松山组绢云石英片岩接触带矽卡岩以及花岗岩和围岩的裂隙中。由于缺乏精确的成矿年代学数据,在一定程度上限制了对矿床成因的认识,并制约了进一步的找矿勘查工作。本文首次利用LA-SF-ICP-MS微区原位U-Pb同位素测年技术对松山锡矿床矽卡岩型和电气石石英脉型矿石中的锡石矿物开展了 U-Pb年代学研究获得2件锡石样品的~(207) Pb/~(206)Pb-~(238) U/~(206) Pb谐和年龄分别为76.6±1.5Ma和79.6±3.6Ma,说明松山锡矿锡的成矿作用主要发生在晚白垩世,与临沧花岗岩主体侵位时间(三叠纪)明显不同。结合地质特征和前人年代学研究成果本文认为该地区存在明显的晚白垩世锡的成矿事件,研究区下一步的找矿工作应围绕岩体与围岩接触带,以及岩体和围岩中的断裂展开。