广西DC矿田成矿作用和物质成分研究

广西DC矿田是我国著名的锡矿产地,除锡以外,还有锌、铅、铜等多金属矿床,以及锑、砷、硫、汞、银、分散元素等可以综合利用。     

江西会昌锡坑迳斑岩型锡矿床成矿系统发育特征与找矿模型

锡坑迳矿田位于南岭成矿带东段与武夷山成矿带交会部位,以早白垩世连续的岩浆喷发-侵入活动与多类型锡多金属成矿作用为特色。矿田内围绕似斑状花岗岩和花岗斑岩发育了岩背斑岩型、淘锡坝和矿背隐爆层间裂隙带型、苦竹岽和凤凰岽云英岩-破碎带蚀变岩型等大中型锡矿床。这些矿床的矿化-蚀变特征可与玻利维亚锡矿带、银岩、维拉斯托和洋滨等国内外斑岩型锡矿床类比,又独具特色,是研究斑岩型锡成矿系统发育特征与找矿模型的理想区域。文章在详细的野外地质调查基础上,系统总结了锡坑迳矿田内各类锡多金属矿化组合特征和蚀变结构,并对岩背矿床和淘锡坝矿床锡石开展了电子探针和LA-ICP-MS原位微区分析。研究结果显示,所有锡石样品均具有La、Pr、Gd和Tb的正异常、Ce与Eu的负异常、明显的Zr/Hf分馏和不规则的稀土元素配分模式,指示成矿热液早期阶段及锡石沉淀阶段经历了流体不相容。岩背锡石较淘锡坝锡石具有高的Ti/Zr和Ti/Sc比值,指示其更为靠近矿化中心。笔者研究认为,锡坑迳斑岩型锡成矿系统矿化类型包括细脉状、浸染状和细网脉状,围岩蚀变由早到晚、由成矿中心向外依次发育黄玉石英带、绿泥石-黄玉石英岩化带、绿泥石-绢云母化带和黏土化-碳酸盐化带。与斑岩型铜钼成矿系统相比,其成矿岩浆岩不仅有花岗斑岩,还有似斑状黑云母花岗岩,矿体在斑岩、花岗岩及上覆火山岩中均有赋存。相较于玻利维亚斑岩型锡成矿带发育的大面积石英-电气石化,锡坑迳斑岩成矿系统更富F,蚀变矿物中出现了大量黄玉、萤石和白云母等。对比国内外典型锡矿床的矿化-蚀变结构和锡石矿物学特征,文章建立了锡坑迳式斑岩型锡成矿系统的找矿模型。     

大兴安岭南段主要金属矿物的成分标型特征

内蒙古东部的黄岗-甘珠尔庙矿带是地处大兴安岭南段的锡乡金属矿带。矿带中各矿床的磁铁矿、锡石、方铅矿、闪锌矿的主元素和微量元素数据表明,这些矿床是属与燕山期岩浆活动有关的矽卡岩型、热液型、斑岩型和云英岩型矿床;其成矿金属组分中的铁来源于区域晚古生代海相中-基性火山岩,部分铅锌来源于区域二叠纪地槽沉积物。研究还表明,与燕山期偏碱性花岗岩有关的锡钨矿床和与燕山期中酸性花岗岩类有关的铅锌矿床其方铅矿、闪锌矿的微量元素含量及比值存在明显的差别。     

Geology and Metallogeny of the Shizhuyuan Skarn-Greisen Deposit,Hunan Province,China

The Shizhuyuan deposit is the largest among the economically important polymetallic tungsten deposits in China. The deposit occurs within the thermal aureole of Yanshanian felsic intrusions that were emplaced into Devonian carbonates and marls. The mineralization can be divided into three phases that are genetically associated with three episodes of granitic emplacement-pseudoporphyritic biotite granite, equigranular biotite granite, and granite porphyry. During the emplacement of pseudoporphyritic biotite granite, thermal metamorphism and subsequent skarnization developed around the stock. The pure limestone was transformed to marble, whereas marls and argillite interlayers were changed to a series of metamorphic rocks such as grossular-diopside hornfels, wollastonite hornfels, diopside hornfels, wollastonite-vesuvianite hornfels, muscovite-K-feldspar-anorthite hornfels, and prehnitevermiculite hornfels. Because of the subsequent strong skarn development, most hornfelses later were transformed into skarns. The skarns distributed around the granite stock are mainly calcic. They are massive in structure, and are composed mainly of garnet, pyroxene, vesuvianite, and wollastonite, with interstitial fluorite, scheelite, and bismuthinite. Although there is no cassiterite in the early skarns, their tin contents average 0.1%. The distribution and compositional and mineralogical relationships of skarn minerals suggest that they formed as a result of progressive reactions of a hydrothermal solution with a limestone of generally constant composition, and that the dominant process was progressive removal of Ca and addition of other constituents to the rocks.

Following the primary skarn formation, some of the assemblages were retrograded to new assemblages such as fluorite-magnetite-salite rock, magnetite-fluorite-amphibole rock, and magnetite-fluorite-chlorite rock. The retrograde alteration of the skarns is characterized by a progressive addition of fluorine, alkali components, silica, tin, tungsten, and bismuth. A zonation from garnet-pyroxene skarn or garnet skarn, through fluorite-magnetite-salite rock, to magnetite-fluorite-chlorite rock frequently can be recognized in the deposit. All retrograde-altered rocks contain scheelite, cassiterite, molybdenite, and bismuthinite.

During the emplacement of equigranular biotite granite, skarn veins several tens of centimeters wide were developed; they contain large crystals of garnet and vesuvianite, and interstitial scheelite, wolframite, cassiterite, and molybdenite. This second stage of mineralization occurs predominantly as coarse and fine stockwork greisens, which were superimposed on the massive skarns and surrounding marble. Such W-Sn-Mo-Bi-bearing greisens can be divided into topaz greisen, protolithionite greisen, muscovite greisen, and margarite greisen. Besides calcic skarn veins and greisens, manganese skarn veinlets also were developed; they consist of rhodonite, spessartine-almandine solid solution, spessartine, and helvite. The distribution of greisens is responsible for a metal zonation—i.e., W-Sn-Mo-Bi and Sn-Be-Cu-F zones from the contact boundary between the granite stock and skarns outward in the deposit. A third stage of mineralization is represented by lead-zinc veins, which also are accompanied by manganese skarns consisting of spessartine, rhodonite, manganese-rich pyroxene, helvite, tephroite, fluorite, tourmaline, and manganese-rich phlogopite.     

广西花山花岗岩云英岩化分带与锡成矿过程的矿物学研究

云英岩脉型锡矿是广西花山花岗岩的主要矿化类型之一。花山花岗岩是氧化型花岗岩,岩体中的锡主要以Sn4+ 的形式,赋存于黑云母、角闪石、榍石、金红石、钛铁矿和锡石等含锡矿物中。通过矿物学研究发现,云英岩化过程是：经充 分分异和演化形成的残余岩浆流体与中细粒黑云母花岗岩相互作用。首先,黑云母等原生含锡矿物中的锡在岩浆流体的作 用下被淋滤出,进入流体或次生矿物相,如金红石、白云母等,发生初步富集;其次,在蚀变后期,成矿流体使早先沉淀 的含锡矿物发生重溶,锡溶解进入成矿流体再次富集。锡在流体中与丰富的F- ,Cl - 等络阴离子结合成稳定的配合物运移, 随着云英岩化加深,流体的pH值升高、温度降低、络阴离子浓度降低,流体中配合物的稳定性降低发生沉淀形成锡矿化     

湖南柿竹园矽卡岩-云英岩型W-Sn-Mo-Bi矿床地质和成矿作用

柿竹园钨多金属矿床由三个阶段不同成矿作用复合叠加而形成。它们分别与似斑状黑云母花岗岩、等粒黑云母花岗岩和花岗斑岩脉有着成因联系。第一阶段矿化包括含矿块状外质矽卡岩和含矿退化蚀变岩；第二阶段为云英岩矿化，在空间上叠加于块状矽卡岩及外部的大理岩；第三阶段为与锰质矽卡岩相伴生的铅锌银矿化。本文详细地描述了前两阶段矿化的地质和成矿地球化学特征，并探讨了其成矿过程。在此基础上，建立了柿竹园矿床的多阶段成矿模     

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。     

Geology and genesis of the Hehuaping magnesian skarn-type cassiterite-sulfide deposit,Hunan Province,Southern China

Magnesian skarn-type tin deposits are relatively rare in the world. The Hehuaping cassiterite-sulfide deposit in southern China, having a total reserve of approximately 130,000 t of tin, 50,000 t of lead and 10,000 t of zinc, is identified as such type. The deposit is related to the Late Jurassic (157 Ma) Hehuaping medium- to coarse-grained biotite granite that intruded the Middle Devonian Qiziqiao dolomite Formation and the Tiaomajian sandstone Formation. Four paragenetic stages of skarn and ore formation have been recognized: I. prograde stage, II. retrograde stage, III. cassiterite-sulfide stage and IV. carbonate stage. Alteration zoning between fresh granite and unaltered country rocks can be identified. The skarn are typified by Mg-mineral assemblages of forsterite, spinel, diopside, tremolite, serpentine, talc, and phlogopite. The geochemistry of various skarn minerals shows a gradually decrease of Mg end member and, correspondingly, an increase of Fe- and especially Mn end members along the process of skarn alteration.Tin mineralization developed during the late retrograde stage resulted in cassiterite–magnetite-diopside skarn. However, the deposition of cassiterite occurred predominantly as cassiterite-sulfide veins along fractures and interlayer fracture zones during stage III. The petrogeochemistry of Hehuaping granite, as well as S- and Pb isotopic analyses suggest that the ore-forming elements have a magmatic source originated from the upper crust. The HO isotopic and fluid-inclusion analyses indicate that high-temperature ore-forming fluids in early anhydrous skarn stage (stage I) are also magmatic origin. In comparison, the retrograde fluids are characterized by relatively low salinity (2 to 10 wt.% NaCl equiv) and low temperature (220 to 300 °C), suggesting a mixed origin of meteoric waters with magmatic fluids. The major ore-forming stage III fluids are characterized by lower temperature (170 to 240 °C) and salinity (1 to 6 wt.% NaCl equiv), indicating fluid mixing could be an efficient tin-mineralizing mechanism. Meteoric waters are dominant in stage IV, resulting in a further lowering of temperature (130 to 200 °C) and salinity (0.4 to 1 wt.% NaCl equiv).     

甘肃省沃尔给花岗岩体中黑云母的成分对其岩体碱度的响应及成岩成矿意义

矿床的形成与其成矿地质体的成因和岩石化学性质密切相关,因此有必要对岩体碱度与成矿关系进行深入研究。通过甘肃省沃尔给花岗岩体的采样测试,并对国内52个各类矿床中与成矿有关岩体中黑云母的主量元素化学成分进行统计和分析,进行寄主岩石碱度判别。研究结果显示：研究区与Cu、Au成矿有关的岩体位于高碱度区域内,而与Sn矿形成有关的岩体均属于低碱度岩石系列。岩浆熔体早期至岩浆后期热液阶段,氧逸度的变化由高到低,介质的碱度逐渐增强,Cu、Au矿床的形成大致经历上述的成岩成矿过程。岩浆结晶过程早期低氧逸度、高碱度有利于Sn的活化迁移,岩浆期后热液阶段的高氧逸度、低碱度有利于锡石的沉淀,但是由于锡石沉淀过程中不断消耗O2,致使其较高的氧逸度显著降低。认为碱度与氧逸度之间相互作用、相互影响进而引起矿化的发生。     

铜官山矿区金口岭铜金矿床围岩蚀变、成矿物理化学条件及成矿机理研究

本文在研究金口岭铜金矿床的围岩蚀变及其与矿化关系的基础上,运用包裹体矿物学、热力学、稳定同位素地球化学等方法,对矿床形成的物理化学条件、成矿物质来源和成矿机理作了深入研究,论证了成岩成矿物质具同源性。本文强调石英闪长岩株下部发生钾蚀变对矿床的形成起重要作用。     

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.     

Mineralisation from Vall de Ribes area (Eastern Pyrenees,Spain)

Vein mineralisation with no preferred orientation, cutting lower Palaeozoic rocks, and local replacement deposits in dolomite show a zoning in tungsten-bismuth, arsenic and antimony minerals away from the adjacent late-Hercynian Costabona granite. A local reversed zoning is related to higher temperatures indicated by fluid inclusion study. Many of the minerals have not previously been reported from this area.     

广西姑婆山锡矿田矿床地质特征及矿床成因

姑婆山锡矿田锡矿床类型丰富，其中以矽卡岩型、矽卡岩-蚀变断裂破碎带复合型锡矿床为主，矿床主要产于燕山早期姑婆山花岗岩西南接触带2km范围内，且具一定的分带性，从接触带往外，依次为矽卡岩型→矽卡岩与蚀变断裂破碎带复合型→锡石硫化物型→石英脉型。矿床受成矿花岗岩、有利赋矿层位及构造复合等因素的控制，与成矿花岗岩关系尤为密切，成岩、成矿时间接近，成矿物质主要来自岩浆，矿床为与花岗岩有关的岩浆期后热液矿床。     

安徽庐枞沙溪斑岩铜矿蚀变及矿化特征研究

沙溪斑岩铜矿是长江中下游成矿带中部庐枞火山岩盆地外围的一个大型铜矿床.本文在前人工作基础上,基于详细的野外观察和系统的岩相学、矿相学工作,详细研究了矿床的蚀变特征及分带.结果表明,矿床的蚀变类型有钾硅酸盐化、青磐岩化、长石分解蚀变和高岭土化,从深到浅依次发育有钾硅酸盐化、长石分解蚀变叠加钾硅酸盐化、长石分解蚀变和高岭土化等蚀变.确定了矿化特征、矿物生成顺序并划分了成矿阶段,即:钾硅酸盐阶段、石英硫化物阶段和石英碳酸盐阶段,其中,石英硫化物阶段又可进一步分为石英硫化物亚阶段和绿帘石-绿泥石亚阶段.基于蚀变及矿化特征认为,沙溪铜矿床的矿化始于钾硅酸盐阶段的晚期,石英硫化物亚阶段是黄铜矿主要的沉淀阶段,石英碳酸盐阶段也对成矿贡献了部分铜质.与世界上不同构造环境的典型斑岩铜矿床对比认为,沙溪矿床总体上与这些矿床的蚀变、矿化特征类似;与陆缘弧、岛弧、陆内碰撞造山后伸展环境矿床在矿体产出位置、蚀变分带方面相似;而由于围岩性质的差异,与板内环境的德兴矿床在矿体位置、蚀变分带方面存在差异,但是二者在脉体类型特别是与矿化关系密切的脉体特征上较为一致.因此,对于斑岩型矿床而言,构造背景可能控制了其岩浆的形成、演化以及含矿性,而岩浆岩最终定位的深度、围岩等条件则控制了其蚀变、矿化特征.     

“岩浆热场”说及其成矿意义(下)

上篇(张旗等[1])初步讨论了岩浆热场说的概念,本文为下篇,主要谈应用,探讨它与成矿作用的关系。研究表明,岩浆热场说对热液成矿作用有重要的意义,可能解决了岩浆热液成矿作用中许多很难解释和争议很大的问题:如钨锡与金铜为什么相伴的问题,矿床为什么大多是多金属成矿的问题,远离侵入体的夕卡岩成因问题,成矿为什么滞后于花岗岩的问题,为什么有些岩体成矿,有些岩体不成矿的问题,为什么大规模岩浆活动与大规模成矿作用息息相关的问题等。岩浆热场与煤和油气成藏有关是一个重要的发现。岩浆热场对煤和油气生成、运移、聚集的影响主要表现在加速烃源岩的热演化,使生油门限变浅,使烃源岩进入高成熟或过成熟,使烃源岩中残余有机质丰度降低。令人感兴趣的是,岩浆热场说还导出了一个"成矿组合"的概念,所谓成矿组合是指在一个或大或小的区域内,在岩浆活动集中的时间段范围内,在热场的统一作用下所形成和影响的所有矿床,不论成因和矿种,均属于一个成矿组合。它包括下述4种类型的矿床:岩浆热液矿床、热泉型矿床、层状热液矿床及生物有机质矿床等。岩浆热场说对于找矿也有启示:首先,我们可以从3个不同的级别上(大规模岩浆活动级别;成矿带、成矿区、矿集区级别;单个矿床级别)规划找矿布局;其次,在岩浆热场的统一影响下将金属矿床和非金属矿床、热液矿床和沉积矿床、无机质矿床和有机质矿床联系起来;第三,推进不同类型矿床研究的互补和交流。看来,岩浆热场对于成矿的作用是最值得学术界关注的,它也许可以改变我们目前对成矿作用的某些根深蒂固的认识,开拓出一个新的领域,推进矿床学研究进入新的时代。     

Magmatic‐Hydrothermal Mineralization Sequence in Xinlu Ore Field,Guangxi, South China: Constraints from Zircon U‐Pb,Molybdenite Re‐Os,and Muscovite Ar‐Ar Dating

The Xinlu Sn‐polymetallic ore field is located in the western Nanling Polymetallic Belt in northeastern Guangxi, South China, where a number of typical skarn‐, hydrothermal vein‐type tin deposits have developed. There are two types of Sn deposits: skarn‐type and sulfide‐quartz vein‐type. The tin mineralizations mainly occur on the south side of the Guposhan granitic complex pluton and within its outer contact zone. To constrain the Sn mineralization age and further understand its genetic links to the Guposhan granitic complex, a series of geochronological works has been conducted at the Liuheao deposit of the ore field using high‐precision zircon SHRIMP U‐Pb, molybdenite Re‐Os, and muscovite Ar‐Ar dating methods. The results show that the biotite‐monzogranite, which is part of the Xinlu intrusive unit of the Guposhan complex pluton, has a SHRIMP U‐Pb zircon age of 161.0 ± 1.5 Ma. The skarn‐type ore has a ⁴⁰Ar‐³⁹Ar muscovite plateau age of 160 ± 2 Ma (same as its isochron age), and the sulfide‐quartz vein‐type ore yields an Re‐Os molybdenite isochron age of 154.4 ± 3.5 Ma. The magmatic‐hydrothermal geochronological sequence demonstrated that the hydrothermal mineralization took place immediately following the emplacement of the monzogranite, with the skarn metasomatic mineralization stage predating the sulfide mineralization stage. Geochronologically, we have compared this ore field with 26 typical Sn deposits distributed along the Nanling Polymetallic Belt, leading to the suggestion of the magmatic‐metallogenic processes in the Xinlu ore field (ca. 161–154 Ma) as a component of the Early Yanshanian large‐scale Sn‐polymetallic mineralization event (peaked at 160–150 Ma) in the Nanling Range of South China. Petrogenesis of Sn‐producing granite and Sn‐polymetallic mineralization were probably caused by crust–mantle interaction as a result of significant lithospheric extension and thinning in South China in the Late Jurassic.     

湖南骑田岭芙蓉锡多金属矿田锡的赋存状态及迁移形式

芙蓉矿田锡矿床按成因可分为构造蚀变带-矽卡岩复合型、构造蚀变带型、蚀变岩体型、矽卡岩型、脉状云英岩型等五种类型。各类型矿体中锡主要以锡石锡的形式出现,其分布率由92.17~97.77%,硫化锡、胶态锡、硅酸锡的分布率<8%。锡元素在钠长石化成矿作用阶段,很可能是以氧的络阴离子SnO33-、氢氧络阴离子〔Sn(OH)6〕2-的形式迁移;在云英岩化成矿作用阶段,主要以氟的络合物,如Na2SnF6,Na2〔Sn(OH、F)6,〕SnF4,K2SnF6等形式搬运;到了绿泥石化锡石硫化物阶段,锡又以硫化锡酸盐、硫化物(Na2SnS3,SnS2,SnS)和氯的络合物(Na2SnC l6)、氟的络合物等形式进行迁移和搬运。     

Ore and Skarn Mineralogy of the Yamato Mine,Yamaguchi Prefecture,Japan, with Emphasis on Silver‐, Bismuth‐, Cobalt‐, and Tin‐bearing Sulfides

Assemblages and chemical compositions of ore minerals from the Yamato mine, Yamaguchi Prefecture, Japan, were investigated in detail to clarify its characteristics as a skarn deposit. Special attention was paid to silver‐, bismuth‐, cobalt‐, and tin‐bearing sulfide minerals and native gold at the mine, which are described here for the first time. Samples of arsenopyrite‐dominant massive ore, and garnet‐rich, clinopyroxene‐garnet‐rich, and wollastonite‐bearing skarn ores were collected from the mine dump. Arsenopyrite is the most abundant ore mineral (>80 vol.%) in the massive ore, in association with both As‐poor/free and As‐bearing pyrite. The major ore minerals in the skarn specimens are pyrite, pyrrhotite, arsenopyrite, chalcopyrite, galena, and sphalerite, along with minor argentite, Ag‐Pb‐Bi sulfate, matildite, bismuthinite, native bismuth, molybdenite, scheelite, stannite, stannoidite, cassiterite, cobaltite, gersdorffite, and Co‐rich violarite. In addition, native gold is observed in the interstices of gangue minerals. Based on the mineral assemblages and textures of the specimens examined, the major ore minerals formed in the early stage of mineralization, and the Bi‐, Ag‐, Co‐, Ni‐, As‐ and Sn‐mineralization occurred in the middle stage. Native gold was deposited in the late stage. The estimated formation temperature of the middle mineralization stage was 312±5 °C, according to iron and zinc partitioning between stannite and coexisting sphalerite. The mineralogical properties and mineralization process of the Yamato mine are consistent with those of common skarn‐ and vein‐type ore deposits associated with ilmenite‐series granitoids in the San‐yo and San‐in districts.     

Characteristic Features of Tin–iron–copper Mineralization in the Anle-Huanggangliang Mining Area, Inner Mongolia, China

Abstract: The Anle Sn‐Cu and Huanggangliang Fe‐Sn deposits have been exploited in the Linxi district, which is located 165 km northwest of Chifeng City in northern China. In this study the formation mechanisms of the tin deposits in the Anle and Huanggangliang mining area were investigated to understand the mechanisms of tin mineralization in northern China. The veins of the Anle deposit are divided into cassiterite–quartz–chlorite veins, chalcopyrite‐bearing quartz veins, cassi–terite–chalcopyrite–bearing quartz veins and sphalerite‐quartz veins. The sequence of mineralization is tin mineralization (stage I), copper mineralization (stage II), and lead‐zinc mineralization (stage III). The Huanggangliang tin deposit consists of magnetite skarn orebodies and many cassiterite‐bearing feldspar–fluorite veins and veinlets cutting the magnetite orebodies. The fluid inclusions in quartz and fluorite in ores from the Anle and Huanggangliang tin deposits are divided into two‐phase fluid inclusions, vapor‐rich fluid inclusions and poly‐phase fluid inclusions. The final homogenization temperatures of fluid inclusions of quartz in the ores of the Anle deposit and fluorite of tin‐bearing feldspar veins in the Huanggangliang tin deposit range from 195 to 425C and from 215 to 450C, respectively. The fluids responsible for the Anle and Huanggangliang tin deposits were of very high temperature and NaCl‐rich ones containing K, Ca, Al, Si, Ti, Fe and Cl in addition to ore metals such as Sn and Cu. The temperature and chemical composition of fluid in fluid inclusions of igneous rocks in the mining area are very similar to those of fluid in fluid inclusions in the ores of these deposits. The fluid for these ore deposits had a close relation with the fluid coexisting with melt of Late Jurassic granitic rocks in this mining area. Salinities of fluid inclusions from these ore deposits and granitic rocks in the mining area were estimated to range from 35 to 50 wt % NaCl equivalent. Based on arsenopy‐rite geothermometry and fluid inclusion studies, a fluid containing 40 wt% NaCl (eq.) could be formed by phase separation of fluid having 6 wt% NaCl (eq.) at a temperature of 420 to 500C and a pressure of 0.3 to 0.4 kb. The temperatures and pressures presented above indicate an NaCl‐rich magmatic fluid derived from granitic melt that had intruded into a shallow level of crust caused the Sn–Fe–Cu mineralization of the mining area. The geological relationship between these ore deposits and granitic bodies around the ore deposits, and the similarity of fluids forming these ore deposits and coexisting with granitic melt, suggest that these ore deposits were formed by the activity of fluid derived from granitic melt in Late Jurassic age.     

Distribution of fluorite deposits in Japanese Islands

The occurrence of fluorite deposits in Japan is limited in the provinces characterized by tin and tungsten mineralization within Southwest Japan. The deposits were formed near acidic igneous rocks of Cretaceous to Tertiary age. The ores in limestone are generally associated with skarn and metallic ore minerals such as cassiterite, scheelite and chalcopyrite. Granitic rocks in the provinces are the ilmenite-series (Ishihara, 1977) having enhanced fluorine contents and high initial strontium ratios. A reducing condition of the ilmenite-series granitic magma may have been more favorable for the concentration of fluorine in the residual magma because of the crystallization of relatively Fe-rich mafic minerals. Presence of thick crust bearing carbonaceous matter at the site of magmatism could have involved in the enrichment of fluorine as well as the reducing condition.