苏州花岗岩的氧同位素研究

本文根据钻孔样品对苏州花岗岩主侵入阶段岩石作了较详细的氧同位素研究。内部相岩石全岩、石英与长石的δ18O值变化小,石英和长石的氧同位素组成处于同位素平衡状态,在δ18OQ－δ18Of图上分布于一个很小区域内,表明内部相岩石并未受到雨水热液作用影响;而边缘相岩石的全岩δ18O变化明显,石英和长石的氧同位素组成处于极端不平衡状态,在δ18OQ－δ18Of图上,呈近乎垂直状态分布,表明已受到雨水热液作用的显著影响。强烈的水一岩交换作用还导致了Nb、Ta、Zr、Hf、Th等稀有元素在边缘相的矿化作用。本文还对苏州花岗岩的源区物质特征作了讨论。     

大厂锡矿床硅,氧同位素地球化学

本文对大厂锡矿床不同类型石英和岩石进行系统的硅、氧同位素研究表明，各类矿化体中石英的硅同位素组成几乎相同，而且它们又与直接容矿硅质岩的δ30Si值十分接近，但完全不同于矿区侵入岩的有关值。这说明层状矿体中的石英与直接窑矿硅质岩有相同的硅质来源，后期各类脉状矿化过程中的硅质来自容矿硅质岩，而不是花岗岩。层状矿体中荣带状岩石和含冰长石混合样的δ30Si值为-0．3‰±0．2‰，这组负值可能是由冰长石引起的。但冰长石中的硅是由海底热水活动系统还是火山灰尘提供尚待研究。对比发现，本矿区硅质岩δ30Si值与部分深海（洋壳区）、半深海（陆壳区）放射虫硅质岩有关资料相似，但其δ18O值低于全球各类硅质岩，它们可能是在海底热水活动与生物化学作用共同参与下形成的。     

锂同位素在伟晶岩矿床成因研究中的应用

稀有金属矿产对现代工业和科技的发展极其重要,伟晶岩矿床作为稀有金属的主要来源,其成因与成矿作用有待深入研究,普遍争论的成因模式包括:花岗岩结晶分异、地壳部分熔融以及岩浆液态不混溶。研究表明地壳深熔过程中锂同位素不发生有意义的分馏,因此在解决花岗岩和伟晶岩的岩浆源区性质方面提供了强有力的证据。文章主要从花岗伟晶岩的成因、锂同位素分馏机制以及锂同位素在伟晶岩矿床中的应用三个方面系统综述了国内外近年来取得的一些研究进展。国内外学者以锂同位素分馏机制详细论述了花岗伟晶岩的Li同位素组成,认为伟晶岩矿床的成因主要为花岗岩结晶分异或地壳部分熔融。但是锂同位素应用于伟晶岩矿床成因方面的研究还不够成熟,需要开展更多的工作。     

安徽铜陵凤凰山铜矿床成矿流体研究

以安徽铜陵凤凰山铜矿床为例,通过对成矿流体特征的研究以及碳、氢、氧同位素分析,探讨矿床的成矿机制,分析成矿流体性质以及成矿流体来源。凤凰山铜矿床石榴子石、石英和方解石普遍发育流体包裹体,其类型为V-L型、V-L+S型、V-L富气相型和V型。石榴子石、石英和方解石中的流体包裹体分别集中于3个区,其流体包裹体的温度和盐度区间代表成矿流体演化的3个不同阶段。成矿流体经历了从高温度、高盐度向低温度、低盐度的持续演化过程,与成矿作用阶段基本对应,降温、流体沸腾是导致流体中巨量铜元素卸载的主要因素。氢、氧同位素组成表明成矿流体以岩浆水为主,可能在成矿晚期混有少量大气降水。     

碱性花岗岩的动力学氧同位素交换和流体流动几何学：交换机制和平流冷却

新疆北部乌仑古塔斯嘎克碱性花岗岩体分为主体相和北部边缘相。条纹长石广泛发育出溶；石英与碱性长石复杂交生。条纹长石的出溶衍生出压应力，造成石英的变形。大部分钠铁闪石是由霓辉石交代形成的。在δ^18O石英-δ^18O条纹长石和δ^18O石英-δ^18O钠铁闪石协变图上，应用耦合的质量传输和动力学限制的同位素交换模型对样品进行了模拟。相对交换速率常数和3个矿物的显微组构特征共同指示，表面反应即溶解-再沉淀和管道扩散是氧同位素交换的主要机制。大气降水从塔斯嘎克碱性花岗岩的北部边缘相住主体相发生了平流渗透。北部边缘相样品的较陡的斜率、以及石英和条纹长石较低的^18O亏损程度，被解释为是由于与同位素组成未演化的短路径大气降水在相对较短的时限内发生氧同位素交换造成的。但是，与同位素组成演化了的长路径大气降水在相对较长的时限内的相互作用，导致了主体样品的较缓的斜率以及石英和条纹长石的较高程度的^18O亏损。对于一个侵入岩体的冷却来说，平流冷却与传导冷却一样重要。     

新疆大红柳滩稀有金属矿田花岗岩与伟晶岩成因关系探讨

西昆仑大红柳滩稀有金属矿田出露大面积的复式花岗岩体和数千条花岗伟晶岩脉,含锂和富锂伟晶岩脉分布在巴颜喀拉山群、石英闪长岩、黑云母二长花岗岩的内部以及二云母二长花岗岩和石榴子石电气石二云母二长花岗岩的边缘或者外围,围绕复式岩体存在明显的矿物组合分带特征。富锂伟晶岩与二云母二长花岗岩、石榴子石电气石二云母二长花岗岩的空间关系更加密切。野外地质特征和精确的年代学数据显示：复式岩体主要由先后侵入的片麻状石英闪长岩、黑云母二长花岗岩和二云母二长花岗岩组成,锆石U-Pb年龄分别为214.7～213.7 Ma,214～213 Ma和209.6～208.8 Ma;花岗伟晶岩的锡石、锆石、独居石、铌钽矿物U-Pb年龄分别为223～207.4 Ma,显示花岗伟晶岩与复式岩体具有密切的时空关系。石英闪长岩、黑云母二长花岗岩和二云母二长花岗岩具有不同的岩石地球化学、εHf(t)值、εNd(t)值和δ7Li同位素特征,显示三者来源于不同的岩浆源区。二云母二长花岗和石榴子石电气石二云母二长花岗岩具有相似的εHf(t)值（-9.49～-4.47）和εNd(t)值（-8.64～-7.81）,表明其源于下地壳物质的部分...     

四川甲基卡锂矿区二长花岗岩的地球化学、氢氧同位素组成及其地质意义

四川甲基卡锂矿床为超大型锂矿床,矿区南部呈岩株状产出的二云母花岗岩与稀有金属伟晶岩在时间、空间及成因上具有密切关系。通过对该岩体元素地球化学特征和氢氧同位素组成的研究,探讨了其在稀有金属成矿过程中的作用。研究结果表明,甲基卡二云母花岗岩为富硅、高钾、钙碱性、强过铝质S型花岗岩,其稀土总量较低,岩浆来源为三叠系西康群砂泥岩为代表的地壳物质的部分熔融,流体来源可能是岩浆水和变质水的混合水。岩体微量元素R型聚类分析显示,与稀有金属成矿最密切的元素为Li、Rb、Ti、W、Mn,而岩体稀有元素含量的变化规律指示岩体北侧成矿效率高于南侧,是下一步找矿工作的重点。综合地球化学、氢氧同位素及前人研究,认为花岗岩浆在底辟侵入过程中可能发生了不混溶作用,由此分离出的伟晶岩浆在运移过程中稀有金属得到不断富集,最终形成伟晶岩型稀有金属矿床。     

新疆阿尔泰将军山天河石花岗岩的岩石成因及其对铷成矿的制约

新疆阿尔泰盛产稀有金属伟晶岩,但缺乏数量上相当的高分异花岗岩。将军山天河石花岗岩是阿尔泰目前发现的唯一富Rb花岗岩,但其岩石成因、Rb的赋存状态及其与周边伟晶岩的关系尚不清楚,从而制约了对Rb富集机理和成矿潜力的认识。据此,本文对将军山天河石花岗岩和伟晶岩开展了全岩组成、年代学、同位素和矿物学研究。结果显示,阿尔泰将军山天河石花岗岩为高分异的A型花岗岩,独居石U-Pb年龄为276.9±2.7Ma,表明形成于早二叠世。独居石Nd同位素组成(ε_Nd(t)为+4.15～+6.05,二阶段模式年龄t_DM2为548～708Ma)显示亏损的源区特征,表明源自新生地壳或有幔源物质的参与。天河石花岗岩与周边的天河石伟晶岩具有空间、时间和成分上的联系,表明二者具有分异演化上的成因关系。将军山天河石花岗岩类型以及天河石伟晶岩矿物组合指示伟晶岩属于NYF族(富Nb、Y、F)。天河石花岗岩与伟晶岩都显示出Rb的矿化,矿石矿物主要为天河石和多硅白云母。从花岗岩到伟晶岩,天河石和云母中的Rb逐步富集。岩浆高度分异是天河石花岗岩Rb富集的主要机制,但新生地壳物源或幔源物质...     

甲基卡花岗岩及伟晶岩脉岩石学特征

通过甲基卡花岗岩体及伟晶岩脉实测剖面,研究其岩石学特征,分析其其构造背景及物质来源。岩体主要由二长花岗岩和正长花岗岩组成,以中-细粒结构为主,可见白云母、黑云母等矿物。组成伟晶岩脉的长石、石英等矿物普遍较粗大,岩脉中可见锂辉石矿物。由于岩石中普遍可见富铝矿物白云母,因此推测岩体可能来源于地壳物质。花岗质岩浆形成后发生了液态不混溶作用,分离出伟晶岩熔体并交代围岩使稀有金属元素富集成矿。     

华南幕阜山花岗伟晶岩的矿物化学特征及指示意义

华南晚中生代幕阜山花岗复式岩基内部及周缘广泛发育花岗伟晶岩脉,部分岩脉富含Li-Nb-Ta等元素,形成大型－超大型稀有金属矿床.本文以幕阜山北缘断峰山地区贫锂伟晶岩类和南缘仁里地区新发现的富锂伟晶岩为主要研究对象,通过详细的岩相学和主要及特征矿物（长石、云母、电气石、石榴子石、绿柱石、铌钽铁矿）的微区原位EPMA和LA-ICP-MS主微量元素地球化学的对比分析,深入探讨了伟晶岩的分类、成因演化及成矿潜力.按照特征矿物组合将伟晶岩划分为断峰山地区电气石伟晶岩、电气石－绿柱石伟晶岩、绿柱石伟晶岩、铌钽铁矿－绿柱石伟晶岩和仁里地区的锂电气石－锂云母伟晶岩5类.5类岩脉中的长石、云母、电气石和/或石榴子石的化学成分记录了不同程度花岗伟晶岩脉的演化阶段,按岩浆演化程度由低至高依次为电气石伟晶岩→电气石－绿柱石伟晶岩→绿柱石伟晶岩→铌钽铁矿－绿柱石伟晶岩→锂电气石－锂云母伟晶岩,并分别对应伟晶岩稀有金属富集程度分类中的无矿→（含Be）→富Be→富Be、Nb、Ta→富Li、Be、Nb、Ta阶段.这一结果表明仁里地区伟晶岩已演化至晚期富集多种稀有金属元素阶段,具有Li-Nb-Ta多金属成矿潜力,而断峰山地区的伟晶岩演化程度相对较低.断峰山电气石－绿柱石伟晶岩中的色带电气石晶体发育强烈成分环带,由内向外可明显分为5环,自核部至边部,Li、Zn、Ga、Ge、Nb、Ta、Sn、Pb等不相容元素和金属元素含量逐渐升高,清晰记录了正常岩浆演化序列及稀有金属富集过程.结合前人有关幕阜山花岗岩类的研究资料,本文认为幕阜山伟晶岩为该地区晚中生代巨量花岗质岩浆经历长期结晶分异作用晚期的分异产物.      

Graphic intergrowths of feldspars and quartz in some Czechoslovak pegmatites

Graphic intergrowths of alkali feldspar+quartz, and plagioclase+quartz, occur together in pegmatites in the eastern part of the Czechoslovak Moldanubicum. They form zones between the finer-grained wall zone and the central blocky feldspar+quartz core. The normative Or-Pig-Q compositions of the graphic intergrowths and the Or-Ab-An contents of their feldspars show broad variations generally, but have a restricted range within individual pegmatites. At two localities studied in more detail, coexisting feldspars show gradual changes in composition, from the margins up to the innermost graphic pegmatite, compatible with fractional crystallization along the feldspar solidus-solvus intersection in the Or-Ab-An-Q-H₂O system, at different vapour pressures in different pegmatites. Two models are demonstrated for low and high pressure cases. The feldspar compositions from central blocky zones deviate from the magmatic fractional crystallizations paths; this corresponds with the general assumption that they crystallized from supercritical gaseous fluids.In these and in similar pegmatites, coexisting alkali feldspar+quartz and plagioclase + quartz intergrowths are interpreted as the last products of cotectic crystallization from an ultimately fractionated granitic magma. Positive correlation of Ab solid solution and quartz content in the potassic intergrowths suggests that these characteristics may be indicative of the relative pressure and temperature effective during their crystallization, when compared in pegmatites of the same bulk composition.     

碾子山晶洞碱性花岗岩矿物-水氧同位素交换反应动力学

对黑龙江碾子山碱性花岗岩的全岩及其主要单矿物进行了氧同位素分析，结果表明，全岩和单矿物不仅δ^18O 值变化范围较大（全岩－2．4－2．0‰，石英0．0－5．8‰，碱性长石－3．8－0．1‰，磁铁矿－8．5－1．0‰），而且强烈亏损^18O。共生矿物之间表现出明显不平衡的氧同位素分馏特征，指示在花岗岩侵位之后与水之间发生了同位素交换，根据锆石和现代大气降水的氧同位素组成，对岩石与外来流体的δ^18O值进行了估计，多维矿水－岩反应时限约为0．3－3Ma，水／岩比（氧摩尔比）介于0．11－1．02之间。水－岩反应温度较高（约400度）和反应时间较长是导致石英δ^18O值降低的主要原因。     

Origin of the younger granites of northern Nigeria

The similarity of the lead isotopic composition in older granites, pegmatites and the younger granites, together with the distribution of tin and the absence of tourmaline in the Mesozoic ring-complexes, are utilised as evidence to establish that the Nigerian younger granites were derived from an initial peralkaline melt by fusion of local basement rocks. It is also suggested that the associated metaluminous trend is caused simply by more complete melting, and that peraluminous granites developed during subsequent cooling. When feldspar normative compositions of younger granites are plotted in the quartz-saturated ternary feldspar system (James and Hamilton, 1969), they support a cyclic event of fusion and cooling to account for the variation in rock-type. The actual source material has not been established but it could be similar to bauchite, a quartz-fayalite monzonite, which was melted by a linear zone of high heat flow from the mantle during the disruption of Gondwanaland.     

文象花岗岩的成分、结构和成因机制

文象花岗岩具有特殊文象结构,研究其三维拓扑结构和形成过程有助于了解花岗质岩石的结晶作用.以北京周口店房山岩体和湖北罗田蕙兰山的文象花岗岩为研究对象,综合利用光学显微镜、扫描电镜、电子探针和电子背散射衍射等技术方法,对岩石矿物组成、结晶学取向和拓扑结构进行了系统研究.结果表明:(1) 文象花岗岩的矿物组成与其形成地质环境有关,石英和长石的含量变化范围很大,其中石英含量通常在20%~45%,但是相同地区同期形成的文象花岗岩具有相对稳定的矿物组成;(2) 长石作为寄主矿物通常呈半自形－自形粗大晶体,可以是碱性长石或斜长石,其端元组分以钾长石和钠长石为主,低温下常分解为条纹长石;(3) 石英在长石寄主矿物中规则穿插生长,在三维空间通常呈近似平行板状、长条状/柱状或非连通枝杈状,并只在特定岩石断面形似象形文字;(4) 正交偏光显微镜下,石英可以具有多种消光位,但是通常在一定范围内同时消光;(5) 石英普遍发育道芬双晶,偶见日本双晶;(6) 条纹长石中钾长石与钠长石对应(100)、(010)、(001) 面和[001]轴近似平行;(7) 多数石英颗粒与寄主长石之间具有密切结晶学取向关系,即石英[1123]轴近似平行长石c[001]轴.该研究证实文象花岗岩是石英和长石同时生长的结果,而长石作为寄主矿物影响并控制着石英的成核与生长方向.      

Geochemistry of K‐feldspar and Muscovite in Rare‐element Pegmatites and Granites from the Totoral Pegmatite Field,San Luis,Argentina

The geochemistry of K‐feldspar for K, P, Sr, Ba, Rb, Cs, Ga, and of muscovite for the same elements plus Nb and Ta, was used for proving the parental relationships of S‐type granites and LCT (Li, Cs, Ta) rare‐element pegmatites in the southernmost pegmatitic field of the Pampean pegmatite province in Argentina. The variation of K/Rb‐Cs, K/Cs‐Rb, K/Rb‐Rb/Sr, K/Rb‐Ba in K‐feldspar from the granites and pegmatites show that they form an association with the evolutional sequence: granites → barren‐ to transitional pegmatites → beryl type, beryl‐columbite‐phosphate pegmatites → complex type of spodumene subtype pegmatites → albite‐spodumene type → albite type pegmatites. This sequence reflects the regional distribution of the different magmatic units. The Ta‐Cs diagram for muscovite reveals that none of the studied pegmatites exceed the threshold established in previous studies for being considered with important tantalum oxide mineralization. The granites and pegmatites constitute a rare‐element pegmatitic field in which different magmatic units form a continuous fractionation trend, extended from the less evolved granitic facies to the most geochemically specialized pegmatites     

Geochemical characteristics and spectrometric prospecting in the muscovite-bearing pegmatites and granites,southeastern Aswan,Egypt

Rare metal mineralization of Sn, Nb-Ta and W is encountered in the Gebel Dihmit area （GDA）, southeastern Aswan, Egypt. The mineralization is related to muscovite granites and their pegmatite derivatives. The pegmatites are divided into three types according to their main mineral assemblages： K-feldspar-muscovite-tourmaline, K-feldspar-albite-muscovite and albite-K-feldspar-lepidolite veins. Petrogenetic studies indicate that Sn and Nb-Ta mineralization extends from the late-magmatic stage to the pegmatite and hydrothermal stages of the （GDA） suite. The albite-K-feldspar-lepidolite granite is composed dominantly of albite, lepidolote, and quartz, with topaz, K-feldspar and amblygonite. The accessory minerals are zircon, monazite, pollucite, columbite-tantalite, microlite and Ta-rich cassiterite. Phenocrysts of quartz, topaz and K-feldspar contain abundant inclusions of albite laths and occasional lepidolite crystals along growth zones （snowball texture）, indicating simultaneous crystallization from a subsolvus, residual magma. The origin of the pegmatites is attributed to extreme differentiation by fractional crystallization of a granitic magma. The economic potential for rare metals was evaluated in the geochemical discrimination diagrams. Accordingly, some of the pegmatites are not only highly differentiated in terms of alkalis, but also the promising targets for small-scale Ta and, to a less extent, Sn. The pegmatites also provide the first example of Fe-Mn and Nb-Ta fractionation in successive generations of granites to cassiterite-bearing pegmatites, which perfectly ex- hibit similar fractionation trends established for primary columbite-tantalite in the corresponding categories of pegmatites. Uranium and Th of magmatic origin are indicated by the presence of thorite and allanite, whereas evidence of hydrothermal mineralization is the alteration of rock- foring minerals such as feldspar and the formation of secondary minerals such as uranophane..     

Isotopic systematics of the rocks of the Khalyuta carbonatite complex of western Transbaikalia

This paper reports the results of isotopic investigations of the rocks of the Khalyuta carbonatite complex (carbonatites, comagmatic silicate rocks, fenites, and hydrothermal rocks) and host limestones and granites. Pyroxene, amphibole, magnetite, potassium feldspar, apatite, phlogopite, calcite, dolomite, strontianite, celestite, and barite were investigated. The isotopic compositions of C, O, Sr, and S were analyzed. The character of the distribution of oxygen isotopic composition in minerals (carbonates, silicates, phosphates, and oxides) suggests their equilibrium formation. It was supposed that the evolutionary trend of C and O isotopic compositions is mainly related to the processes of differentiation in the melt-fluid system and indicates the absence of significant contamination by carbon and oxygen from a crustal source during rock formation from the magmatic stage to the hydrothermal stage. The isotopic compositions of S and Sr did not change.     

Petrological and mineralogical characteristics of younger granites and pegmatites in the Wadi Haleifiya area,southeastern Sinai,Egypt

This study is concerned with the radioactivity and mineralogy of the younger granites and pegmatites in the Wadi Haleifiya area, southeastern Sinai Peninsula, Egypt. The area is occupied by metasediments, migmatites, older and younger granites. Most of these rocks, especially granites, are dissected by mafic and felsic dykes as well as pegmatites. The younger granites are represented by three main varieties: monzogranites, syenogranites and alkali feldspar granites. The monzogranite consists essentially of quartz, plagioclase, potash feldspar and biotite with minor musco-vite. Iron oxide, titanite, zircon and allanite are the main accessory minerals. Syenogranite is massive, medium- to coarse-grained and commonly exhibits equigranular and hypidiomorphic textures. It is made up essentially of potash feldspar, quartz, plagioclase and biotite. Iron oxides, allanite, epidote, titanite, and zircon are accessory minerals. The alkali feldspar granite consists mainly of perthite, quartz, alkali amphibole (arfvedsonite and riebekite), biotite, sub-ordinate plagioclase and aegirine. Iron oxide, zircon and apatite are accessory minerals, whereas chlorite and sas-surite are secondary minerals. The altered monzogranite and pegmatite recorded high radioelement contents. The eU reaches up to 120 (av.=82×10-6) in the altered monzogranite and up to 55 (av.=27×10-6) in the pegmatites. The high radioactivity in the altered monzogranite is due to the presence of thorite, uranothorite and metamict zircon. In the pegmatites, it is re-lated to the presence of uranophane, uranothorite, thorite, zircon, samarskite, monazite, xenotime, magnetite, ilmen-ite, hematite and rutile.     

巴尔喀什成矿带阿克沙套云英岩型钨钼矿床地质特征与铼-锇同位素测年分析

哈萨克斯坦阿克沙套大型钨钼矿床处于中亚成矿域巴尔喀什成矿带内。该矿床为云英岩型浸染状矿床, 具有云英岩型矿床的典型矿物组合、围岩蚀变、矿体形态和结构构造。矿区产出有伟晶岩、石英长石脉, 含有钨钼矿、石英和黄玉云英岩矿体等。本文对阿克沙套钨钼矿床辉钼矿样品进行了铼-锇同位素分析, 得到辉钼矿模式年龄(平均值)为289.3 Ma, 处在早二叠世。分析认为, 阿克沙套云英岩型钨钼成矿作用是晚石炭世中亚成矿域大规模斑岩型铜钼成矿作用延续的结果, 属中亚造山带海西晚期构造-岩浆活动的产物。      

低18O碱性花岗岩成因讨论——以内蒙巴尔哲碱性花岗岩为例

巴尔哲花岗岩是一个罕见的亏损^18O的碱性花岗岩体，其中的石英、长石、钠闪石、锆石以及全岩的氧同位素含量都是国内碱性花岗岩中最低的。根据其氧同位素资料，结合岩体地质地球化学特征，讨论了该岩体以及我国东部低^18O碱性花岗岩的成因，认为用岩石与大气降水间同位素交换和开放体系下的岩浆去气作用解释该类岩石成因较为合理，但也有缺陷，有待进一步研究。