格陵兰伊犁马萨克铌-钽-铀-稀土矿床研究进展

随着科学技术的日益发展,人们对稀有元素资源,特别是稀土元素(REE)资源的需求日益增大。位于格陵兰岛西南部可凡湾(Kvanefjeld)的伊犁马萨克杂岩体(Ilimaussaq complex)是目前世界上第二大的稀土矿富集地,仅次于我国的白云鄂博稀土矿。该矿床储量大,且重稀土所占比例高。该杂岩体以其独特的过碱性岩(agpaitic rocks)组合和超过225种稀有矿物而闻名于世,其中有11种矿物目前在世界其他地方并未发现,为该杂岩体所独有。伊犁马萨克独特的地质背景、极大的矿床价值以及独特的岩石矿物组合等无不吸引着全世界的地质学家。基于前人对伊犁马萨克的研究,从产出环境、地质特征、矿床成因和找矿模型等方面进行了总结和介绍。     

安康双龙桥碱性辉长杂岩中磷灰石和榍石的矿物成分研究

X射线衍射分析和化学成分研究表明,磷灰石为氟磷灰石,榍石成分中存在着的主要类质同象替代是(Fe~(3+)、Al)+(F,OH)~-=Ti~(4+)+O~(2-)。磷灰石和榍石是碱性辉长岩的REE、Ba、Zr等微量元素的主要载体;它们是在较高氧逸度的条件下结晶的。磷灰石的Sr同位素特征说明形成双龙桥碱性辉长杂岩的物质来源于上地幔。     

塔什库尔干新生代碱性杂岩造岩矿物化学成分及成因意义

新疆塔什库尔干碱性杂岩体主要由苦子干碱性正长岩体和卡日巴生碱性花岗岩体组成，是帕米尔地区最大的新生代碱性杂岩体。本文在岩相学和矿物化学的基础上，着重研究了苦子干岩体主要造岩矿物的种属、共生关系和结晶顺序。研究表明，苦子干岩体中的不同岩石类型系同源岩浆演化的产物；岩浆在整个演化过程中平衡结晶作用占主导，分离结晶作用的影响极小。据岩浆房中矿物结晶时的温度和压力条件、矿物的结晶特征及演化趋势，推测岩浆上升速度较快，侵位较浅。     

中国碱性杂岩的成因及其成矿作用

本文从碱性杂岩的产出和分布、地质特征、地球化学特征、成因、成矿作用几个方面综述了近年来对于我国碱性杂岩的研究成果与进展:(1)岩石学和同位素特征表明,硅不饱和的碱性杂岩类多属地幔低度部分熔融的原始岩浆为主侵位的产物;而硅饱和或过饱和碱性杂岩类多属深源岩浆与陆壳混染的产物。(2)地幔源区的低度部分熔融导致了稀土元素和大离子亲石元素等不相容元素的富集,同时富集的挥发份构成了矿化剂,对成矿具有重要控制作用。(3)深大断裂控制着碱性杂岩的产出,同时伴随着地质历史时期的重要地质事件,中国受深大断裂控制的碱性杂岩带主要有郯城-庐江碱性杂岩带、攀西碱性杂岩带和哀牢山-金沙江碱性杂岩带等9条。     

冀西北与碱性杂岩有关的金矿床的成因探讨

冀西北的东坪、中山沟、后沟等金矿床产于碱性正长岩杂岩体的内外接触带，与岩体有成因联系。矿石为少硫化物型。矿体有三种类型：石英脉型；石英脉＋脉旁蚀变岩型；钾、硅化蚀变岩型。对微量元素、稀土元素及Ｓ、Ｐｂ、Ｃ、Ｏ和Ｓｉ的同位素的研究结果表明，成矿物质主要来源于碱性杂岩体，成矿流体混合热液，成矿时代为燕山期（钾长石Ａｒ－Ａｒ年龄为１５６￣１７７Ｍａ）。矿床为燕山期强烈岩浆活动产生的岩浆水与大气降水作用形     

俄罗斯阿尔丹地块西部穆龙斯克杂岩体中的碱性交代岩

含紫硅碱钙石、镁钠钙闪石（钠透闪石－石棉）及蓝色办透闪石的碱性交代岩的形成首先是由硅酸和碱（Ｎａ２Ｏ和Ｋ２Ｏ的不同作用）的惰性及ＦｅＯ,ＭｇＯ,ＣａＯ和Ａｌ２Ｏ３的强烈活性决定的,含蓝色软透闪石和镁的钙闪石（钠透闪石－石棉）的交换岩是岩浆期后溶解演化的中期产物,而含紫硅碱钙石的交换岩却是其晚期的产物。     

华北某些富磷碱性-偏碱性杂岩岩浆成分和熔体结构与含矿性关系

华北富磷碱性-偏碱性杂岩的岩浆成分和岩浆熔体结构对岩浆的含磷性和磷的富集起着控制作用。磷的富集作用发生在岩浆起源阶段和岩浆分异作用(岩浆不混溶作用、结晶分异作用)阶段。在这两个阶段的演化过程中,P_2O_5含量及其变化趋势严格受岩浆成分、熔体结构(如NBO/T,M/F)和α_(SiO_2)、μ_(K_2O)控制,表现为P_2O_5含量与SiO_2、K_2O、K_2O+Na_2O及CaO/(MgO+SiO_2)等有密切关系。     

Clinopyroxenes and Coexisting Mafic Minerals from the Alkaline Ilimaussaq Intrusion, South Greenland

The Ilímaussaq intrusion consists of an augite syeniteshell and a central cumulitic series of layered peralkaline(agpaitic) nepheline syenites with both roof and bottom cumulates.Microprobe analyses of the strongly zoned mafics show that thepyroxenes range from ferro-salite through hedenbergite to aegirine,the amphiboles from hastingsite through katophorite to arfvedsonite,and the olivines from Fo_16.8 to F_O0.2. Aenigmatite analysesare also presented. The crystal chemistry of the pyroxenes isdiscussed in detail. The behaviour of the various elements isdiscussed in relation to the conditions in the coexisting magma.The relation between oxygen fugacity and silica activity andthe stability of fayalite and Na-poor pyroxenes in over-andundersaturated magmas is considered. The persistent stabilityof these minerals in the strongly undersaturated Ilimaussaqmagma shows that the oxygen fugacities in Ilímaussaqwere lower than in any other known alkaline suites. Based onthe compositional development in the mafic minerals it is inferredthat the intrusion formed from at least three separate pulsesof successively more differentiated magma: (1) an augite syenitemagma congealed inwards from the sides, (2) a peralkaline undersaturatedmagma gave rise to the roof cumulates which congealed successivelydownwards. The differentiating magma was water-undersaturatedand underwent depletion in Mg and enrichment in Zr and Na. Thecontemporaneous bottom cumulates are hidden beneath the nowvisible bottom cumulates which possess a still more differentiatedliquidus mineral assemblage and are ascribed to a third separatemagma pulse.     

Phase Equilibrium Constraints on Intensive Crystallization Parameters of the Ilimaussaq Complex, South Greenland

The 1·13 Ga Ilímaussaq intrusive complex, SouthGreenland, is composed of various types of alkali granite andsilica-undersaturated alkaline to agpaitic nepheline syenitesrelated to three subsequently intruded magma batches. Mineralchemistry indicates continuous fractionation trends within eachrock type, but with distinct differences among them. The last,peralkaline magma batch is the most fractionated in terms ofX_Fe^{mafic mineral}, feldspar composition and mineral assemblage.This indicates that an evolving magma chamber at depth discontinuouslyreleased more highly fractionated alkaline melts. Fluid inclusionsin some sodalites record a pressure drop from 3·5 to1 kbar indicating that crystallization started during magmaascent and continued in the high-level magma chamber. On thebasis of phase equilibria and preliminary fluid inclusion data,crystallization temperature drops from >1000°C (augitesyenite liquidus) to <500°C (lujavrite solidus) and silicaactivity decreases from     

Ca-rich Ilvaite-Epidote-Hydrogarnet Endoskarns: a Record of Late-Magmatic Fluid Influx into the Persodic Ilimaussaq Complex, South Greenland

Endoskarn assemblages involving the Ca-silicates ilvaite, epidoteand Ca-rich garnet occur along fracture zones in the persodicIlímaussaq intrusion, South Greenland. The 1·16Ga intrusion solidified at a depth of about 3–4 km, belowa cover of sandstones and pillow-basalts of the Eriksfjord Formation.In contrast to typical skarn assemblages, the Ilímaussaqendoskarns contain albite as a main phase and they did not formin metacarbonate rocks, as these are completely lacking in thevicinity of Ilímaussaq. Instead, they record late- topost-magmatic interaction of possibly external Ca-rich fluidswith the alkaline to agpaitic magmatic rocks. Accordingly, endoskarntextures clearly reflect the magmatic textures of the precursorrocks. Phase relations in two endoskarn varieties with epidote+ albite + andradite-rich garnet ± ilvaite ± retrogradeprehnite suggest their formation at about 500°C at highoxygen fugacities slightly above the hematite–magnetiteoxygen buffer [FMQ (fayalite–magnetite–quartz) +5 to FMQ + 7] with later small modifications as a result offluid influx or cooling of the original fluid at about 300–350°C(formation of prehnite) and at about 200–250°C (oxygenisotopic re-equilibration of the albite). One model for theformation of the observed assemblages is the decomposition ofCa-bearing minerals, such as primary eudialyte, clinopyroxeneor ternary feldspar, and redistribution of the Ca by a metasomatizinglate-magmatic fluid. Stable isotope (O, H) investigations, however,favour a model in which seawater was the metasomatizing fluid,which entered the Eriksfjord basalts above the intrusion, reactedwith them (spilitization) and brought about 10^–3 mol/lCa along fractures into the metasomatized rocks. Fluid–rockinteraction in the Eriksfjord basalts is documented by abundantchlorite–epidote–quartz assemblages; high fluid/rockratios allowed the fluid to retain its seawater oxygen isotopecomposition. KEY WORDS: agpaite; endoskarn; Ilímaussaq; ilvaite; metasomatism; seawater     

Fractionation and Assimilation Processes in the Alkaline Augite Syenite Unit of the Ilimaussaq Intrusion, South Greenland, as Deduced from Phase Equilibria

The early augite syenite unit in the 1·13-Ga-old Ilímaussaqintrusive complex, South Greenland, consists of a magmatic assemblageof ternary alkali feldspar + fayalitic olivine + augite + titanomagnetite+ apatite + baddeleyite ± nepheline ± quartz ±ilmenite ± zircon. Feldspar, nepheline and QUILF thermometryyield T = 1000–700°C, at P = 1 kbar, which is derivedfrom fluid inclusion data from other parts of the complex. Ternaryfeldspar was the first major liquidus phase. It crystallizedat temperatures between 950 and 1000°C from a homogeneousmagma with a_SiO2 = 0·8 and f_O2 about 1·5–2log units below the fayalite–magnetite–quartz (FMQ)buffer. Later, closed system fractionation produced nepheline-bearingassemblages with a_SiO2 = 0·4 and log f_O2 = FMQ –3 to FMQ – 5. Assimilation of wall rocks produced localvariations of melt composition. Four traverses through the unitwere sampled parallel to the assumed direction of crystallization.They exhibit significant differences in their mineral assemblagesand compositions. The chemical zoning and calculated intensiveparameters of four sample suites reflect both closed systemfractional crystallization and local assimilation of wall rocks. KEY WORDS: alkaline magmatism; assimilation; fractionation; redox equilibria; QUILF     

Microsyenitic dykes from the Northern Part of the Ilimaussaq Peninsula,Southern Greenland

Summary Among the igneous rocks of the Gardar period of the Precambrian of Southern Greenland numerous dykes occur. Microsyenitic types are an outstanding feature among these. Many of them can be traced over 15 km in length; widths over 10 m are not uncommon. There are porphyritic and non-porphyritic varieties. Alkali feldspars form the main-constituents and are accompanied by aegirine-augite, riebeckite, fayalitic olivine, ilmeno-magnetite, apatite. Riebeckite seems to appear in quartz-bearing types only. Quartz or nepheline appear in slight amounts in some of these rocks.There is no differentiation in the dykes. Undersaturated, saturated and slightly oversaturated types can be distinguished. The undersaturated types are closely connected with the augite syenites. of the main-masses which are supposed to be the original magma of the alkaline province. In many places the dykes are prior to the main intrusions. The saturated and slightly oversaturated dykes are thought to belong to the main quartz-syenites which are hybridization products of the augite syenite magma contaminated by later alkalic acidic magmas.

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Zusammenfassung Unter den magmatischen Gesteinen der Gardar Periode im Präkambrium Südgrönlands sind Ganggesteine sehr zahlreich vertreten, unter denen wiederum Mikrosyenite eine ausschlaggebende Rolle spielen. Manche lassen sich über 15 km hin verfolgen; Breiten von über 10 m sind keine Seltenheit. Man kann porphyrische und nicht-porphyrische Typen unterscheiden. Alkalifeldspate sind die Hauptgemengteile, die von Aegirin-Augit, Riebeckit, fayalitischem Olivin, Ilmeno-Magnetit, Apatit begleitet werden. Riebeckit scheint nur in Quarz führenden Typen aufzutreten. Quarz oder Nephelin sind in untergeordnetem Maße in einigen Gesteinen vorhanden.Es ist keinerlei Differentiation festzustellen. Es werde untersättigte, gestättigte und übersättigte Typen unterschieden. Die untersättigten sind eng mit den Augitsyeniten der Hauptmassive verbunden, von denen angenommen wird, daß sie aus dem ursprünglichen Magma dieser Alkaliprovinz erstarrien. In vielen Fällen sind die Gänge vor den Hauptintrusionen eingedrungen. Die gesättigten und leicht übersättigten Typen werden den Quarzsyeniten der Hauptmassive genetisch zugeordnet. Diese werden als Hybridisationsprodukte aus dem Originalmagma der Augitsyenite mit späteren kieselsäurereichen, alkalischen Magmen gedeutet.

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With 5 Figures     

相山矿田居隆庵矿床钍矿物特征研究

居隆庵矿床是相山矿田中一个大型的铀-钍混合矿床。通过系统的镜下显微特征研究和电子探针分析,查明了主要钍矿物和含钍矿物的种类,分析了钍的赋存状态和蚀变特征。钍的赋存状态有独立钍矿物、类质同象替换铀矿物和类质同象存在于副矿物中。相关的矿化蚀变有碳酸盐化、钠长石化、绢云母化、黄铁矿化、绿泥石化、水云母化和萤石化。本文还总结了钍(铀)矿物的赋存位置。     

桐柏-大别山南缘志留纪黄羊山碱性杂岩的暗色矿物

黄羊山碱性杂岩体位于桐柏-大别山南缘,其SHRIMP U-Pb年龄为(439±6) Ma.该杂岩体由石英正长岩和碱性花岗岩组成,其中以石英正长岩为主体,从中心到边缘粒度变化由粗到细.利用电子探针对该杂岩体中的特征暗色矿物的分析结果表明,角闪石和辉石的成分变化较小,角闪石显示出从铁钠透闪石到钠铁闪石的成分演化趋势,辉石主要为霓石,另外岩体中大量出现三斜闪石.根据矿物间的相互接触关系、环带结构、矿物组合的相平衡关系等识别了原生的岩浆矿物组合和次生的岩浆期-岩浆期后矿物组合,建立了矿物结晶顺序,重建了过碱性岩浆或流体的成分、温度、氧逸度的演化历史.从矿物组合的相平衡关系角度表明,黄羊山碱性杂岩体为大陆裂谷环境的产物.     

黑龙江省砂宝斯金矿床矿石矿物与金矿物特征研究

为给砂宝斯金矿床的勘探和利用提供依据,本文总结了多年的野外观察资料,并通过镜下鉴定、人工重砂、电子探针等方法对该矿床的矿石矿物、金矿物特征进行了系统研究。结果表明,该矿床的矿石类型为贫硫化物微细粒浸染型金矿石,矿石矿物主要为黄铁矿,次为毒砂,含有较多的微量元素;脉石矿物主要为石英。矿石结构主要为半自形-自形、他形、交代、固溶体分离结构,浸染状或细脉浸染状构造。金矿物主要为自然金,其赋存状态以硫化物中包裹金和脉石粒间金为主,主要为微粒金及次显微金,呈微细分散状态。除Au元素外,矿床中其他元素均不具有综合利用价值,有害元素含量低。     

Gold and Silver Minerals in Sulfide Ore

Geology of Ore Deposits - Abstract—Gold and silver are capable of forming stable natural compounds with different elements. For gold 36 minerals are known: 10 in the class “Native...