青海三江北段拉地贡玛地区印支期花岗岩地球化学特征及地质意义

拉地贡玛地区花岗岩处于金沙江缝合带内,区域上隶属西金乌兰—金沙江缝合带的物质组成部分,在研究区属通天河构造岩浆岩带。据出露岩石类型,将其划分为3个单元: 拉地贡玛花岗闪长岩(T₃γδ)、日阿日曲石英闪长岩(T₃δο)、缅切英云闪长岩(T₃δi)。岩浆侵位时代为晚三叠世; 侵入岩体是以高硅富铝、多碱质和挥发组分为特征的兼具I型和S型花岗岩,属过铝质花岗岩; 轻重稀土分馏程度明显,轻稀土富集,Eu、Ce呈弱负异常,Rb、Th、Ba等元素富集,Y、Yb、Cr等元素亏损,具I型和S型花岗岩的特点,与火山弧钙碱性花岗岩特征相似。研究区花岗岩形成构造环境与晚三叠世多彩—当江构造混杂带的俯冲作用有关,是与俯冲汇聚构造环境有关的大陆碰撞弧型花岗岩。     

花岗岩类某些矿物中微量元素和挥发分离子探针[SIMS]研究

本文采用离子探针(SIMS)分析花岗岩类磷灰石、锆石和黑云母等矿物中微量元素和挥发分,来探讨花岗岩类成矿作用。结果证明,不同时代和不同成因的磷灰石和锆石具有某些指纹特征;并显示了花岗岩类所含微量元素和挥发分之间存在某种相关关系。     

中国东南部中生代含铀花岗岩成岩物质来源与铀成矿作用

几年来野外实地调查和室内大量的实际资料表明,我国东南部中生代含铀花岗岩体大多数属原来大陆壳硅铝层浅海相陆源沉积岩和火山沉积岩,以及少量的花岗岩等物质在深部增温增压下经受重熔作用而产生的酸性岩浆侵入于距当时地表约为2—4公里深处,经过充分而完善的结晶分异作用和射气     

A study of Sr isotopic characteristics and ore-search indicators of Gejiu Sn-bearing granites

Whole-rock Rb-Sr isochron dating of Sn-bearing granites and alkaline rocks from Gejiu, Yunnan Province has been conducted for their emplacement ages and initial⁸⁷Sr/⁸⁶Sr ratios. The Sr isotopic compositions of apatites from some basic rocks in Jiasha, and granite bodies also have been studied in detail. The genesis and evolution of Gejiu Sn-bearing granites as well as ore-search indicators are discussed on the basis of the available data in conjunction with the geochemical data on trace elements (such as Rb and Sr), Sr isotopic characteristics of the volcanic rocks, meta-diabase and host rocks and the isotopic features of ore leads.     

Volatile control of contrasting trace element distributions in peralkaline granitic and volcanic rocks

Anomalous enrichments of Zr (>500 ppm), Zn (> 100 ppm), Nb (>25 ppm), Y (>60 ppm), Th (>20 pm), U (> 5 ppm), LREE (>230 ppm) and HREE (>35ppm), and high Rb/Sr (>5) characterize peralkaline granites, in contrast to their peraluminous and calc-alkaline equivalents. Within the peralkaline suite, comenditic and pantelleritic volcanics exhibit two- to five-fold increases in the concentrations of these trace elements over comagmatic granites. These cannot be explained by crystal- liquid fractionation processes, and require the evolution of a sodium-enriched fluid. Corresponding trace element increases in the granites in areas of alkali metasomatism support this argument, and reflect the partial confinement of this volatile phase within the high-level magma chambers. REE studies in particular might eventually allow an evaluation of the role of Cl⁻ versus F⁻ and CO₃-complexing in the evolution of the volatile fluid.     

Characteristics of geochemical evolution of trace elements and REE in Gejiu granites,Yunnan Province

The evolution characteristics of Gejiu granites, Yunnan Province are described in terms of their petrology, especially their trace elements and REE geochemistry. The three major types of Gejiu granites: porphyritic biotite monzonitic granite (stage I), medium-coarse-grained biotite-K-feldspar granite (stage II) and two-mica alkali-feldspar granite (stage III) are thought to have been formed successively from the same granite magma source through fractional crystallization (Rayliegh fractionation), because linear correlations are found between log(Rb/Sr)-log Sn, log(Rb/Ba)-log Sn, log(Rb/Ba)-log(Rb/Sr), log La-log Sr, log Ce-log Sr, log Eu-log Sr, etc. In addition, the characteristics of REE distribution patterns in these three major types of granites also reflect the magmatic differentiation features of Gejiu granites. Of the three major types, the two-mica alkali-feldspar granite of stage III underwent the strongest differentiation, and thus has the closest genetic relationship with the Gejiu tin-polymetallic ore deposit. Such tin-polymetal mineralized granites are characterized by high Rb/Sr and Rb/Ba ratios, low K/Rb and ΣCe/ΣY ratios and remarkable Eu depletion.     

Geochemical features of rare-metal granites of the Zashikhinsky Massif,East Sayan

The paper presents detailed geochemical data on the rocks of the Zashikhinsky Massif and mineralogical–geochemical characteristics of the ores of the eponymous deposit. The rare-metal granites are divided into three facies varieties on the basis of the degree of differentiation and ore potential: early facies represented by microcline–albite granites with arfvedsonite, middle facies represented by leucocratic albite–microcline granites, and late (most ore-bearing) facies represented by quartz–albite granites grading into albitites. Microprobe data were obtained on major minerals accumulating trace elements in the rocks and ores. All facies of the rare-metal granites, including the rocks of the fluorite–rare-metal vein, define single compositional trends in the plots of paired correlations of rock-forming and trace elements. In addition, they also show similar REE patterns and spidergrams. The latter, however, differ in the depth of anomalies of some elements. Obtained geological, petrographic, and geochemical data suggest a magmatic genesis of the rocks of different composition and their derivation from a single magma during its differentiation. On the basis of all characteristics, the Zashikhinskoe deposit is estimated as one of the largest tantalum rare-metal deposits of alkaline-granite type in Russia.     

新疆东准噶尔北部碱性花岗岩的特征、成因及构造意义

新疆东准噶尔北部的碱性花岗岩呈带状分布于乌伦古断裂及额尔齐斯─玛因鄂博断裂之间地区。碱性花岗岩以出现碱性暗色矿物及铁质黑云母为特征，高硅、高碱、低钙、低镁铁，富含高场强元素，属典型的Ａ型花岗岩，它们产出的特定构造环境，据化学成分的构造环境判别为板内非造山的裂谷环境；成因类型相当于Ｅｂｙ（１９９２）的Ａ１类Ａ型花岗岩，明显不同于东准噶尔中部及南部碱性花岗岩带产出的造山期后张性构造环境。     

滇西户撒盆地新近系褐煤微量元素地球化学特征

为探讨滇西户撒盆地新近系褐煤的微量元素地球化学特征及指示意义,采集了5口验证钻孔内15层褐煤的新鲜样品,利用ICP-MS对微量元素含量进行测试。结果表明,与中国煤微量元素背景值进行比较,户撒盆地褐煤Rb、Cs、Th富集,Be、Sc、Cr、Cu、Ga、In、W、Pb、U稍富集。户撒褐煤富集的潜在有害微量元素有Be(5.32mg/kg)、Cr(39.8mg/kg)、Cu(39.7 mg/kg)、Pb(32.8 mg/kg)、Th(39.3 mg/kg)和U(7.39 mg/kg)。褐煤的REE总量为196.03~550.42 mg/kg,平均为306.71 mg/kg,远高于中国煤的REE总量均值(136 mg/kg),表现出LREE明显富集,HREE相对亏损特征。δCe值负异常与微量元素比值特征均表明户撒泥炭的沉积期主要为酸性还原环境。δE负异常与球粒陨石标准化分配模式表明户撒新近系褐煤稀土元素与盆缘酸性花岗岩的陆源供给有关。     

大别超高压变质地体四道河地区岩石学研究

对四道河地区超高压变质岩剖面的研究分析显示,该剖面有3种岩石类型:榴辉岩类、片麻岩和面理化含榴花岗岩。榴辉岩具不同程度的退变质现象,呈透镜体状产出于斜长角闪岩、片麻岩和面理化含榴花岗岩中,原生矿物组合为石榴石、绿辉石、柯石英和金红石。榴辉岩退变为斜长角闪岩近于等化学系列;片麻岩在主量成分上与榴辉岩及其退变产物(斜长角闪岩)存在突变关系,但微量元素与榴辉岩有一定的相似性;面理化含榴花岗岩主量元素和微量元素地球化学特点为:富SiO2 、K2 O Na2 O和高价阳离子Ga、Y以及REE ,K2 O/Na2 O值低,贫Al、Ca、Mg、Ti、P ,结合构造环境、同位素及年代学资料分析,其应属于后碰撞造山A型花岗岩。基于以上认识推断:大陆板片俯冲至上地幔经历了超高压变质作用,表壳岩变质形成榴辉岩;当超高压变质岩石折返至中下地壳时发生了强烈的减压退变质作用形成斜长角闪岩,随后,与片麻岩及面理化含榴花岗岩一道从中下地壳向地表进一步折返,并一同经历了后期的变质变形作用。     

福建沙县壳源型晶洞花岗岩的基本特征

福建沙县地区晶洞花岗岩的发现，在闽中尚属首次。该区内晶洞花岗岩特征与闽西南地区及闽东地区晶洞花岗岩存在较明显的差异：矿物成分相对富含黑云母；副矿物富含铁的高价氧化物及稀有、稀土矿物；岩石化学成分相对富铝、富挥发组分而贫Ca、Mg和Na；微量元素相对富Sn、Rb、Ba、Sc、U和Th；轻、重稀土比值小于1，具强烈的Eu负异常，稀土元素配分型式呈特殊的“海鸥”型。其物质来源主要为地壳物质的部分熔融，属壳源型花岗岩。岩浆经过长石的分离结晶后，在浅成的环境中侵位固结，其形成时代为白垩纪。     

A型花岗岩的微量元素地球化学

本文总结和评述了A型花岗岩典型的微量元素特征,如富集Ga、稀土元素（除Eu外）和高场强元素,亏损Ba、Sr和明显的Eu负异常。分别讨论了影响微量元素特征的多种制约因素,主要包括源区性质、岩浆的物理化学条件、岩浆作用过程和络合作用。通过对比世界范围内几个地区相伴生的碱性A型花岗岩和铝质A型花岗岩的微量元素地球化学特征,发现前者Ga、F含量更高,而轻重稀土比值小,Eu、Ba、Sr等元素含量更低,显示了前者的岩浆分异作用更强,同时说明了碱性A型花岗岩可以由与之伴生的铝质A型花岗岩分异而来。     

云南绿春黄草岭地区花岗岩SHRIMP锆石U-Pb年代学特征及地质意义

金沙江-哀牢山缝合带系三江特提斯构造域东缘一条重要的古特提斯缝合带,其南段哀牢山缝合带闭合的时限及其岩浆活动响应,尚缺乏精确的年代学与岩石地球化学制约。本文对出露于哀牢山缝合带南部绿春地区黄草岭的花岗岩类进行了SHRIMP锆石U-Pb年代学与全岩主量、微量元素地球化学研究,获得花岗岩的形成年龄为249.8±4.3Ma。地球化学特征表明,该花岗岩具有K、Rb、U、Th和Pb正异常、Nb、Ta、Ti、Hf和Eu(0.29~0.37)负异常、过铝质与高钾钙碱质特征,属于S型花岗岩,形成于岛弧构造背景中。年代学和地球化学特征表明,哀牢山洋在早三叠世向西俯冲消减,绿春地区已出现成熟岛弧,并向陆-陆碰撞过渡。     

Trace elements and evolution of granite melt as exemplified by the Raumid Pluton,Southern Pamirs

New trace element data were obtained by ICP-MS for 58 samples representing eight intrusive phases of the Raumid granite Pluton. All of the rocks, except for one sample that was deliberately taken from a greisenized zone, were not affected by postmagmatic fluid alteration. The sequential accumulation of incompatible trace elements (Rb, Ta, Nb, Pb, U, and others) in the Raumid Pluton from the early to late phases coupled with a decrease in incompatible element contents (Sr, Eu, Ba, and others) indicates a genetic link between the granites of all phases via fractional crystallization of a granite melt. The REE distribution patterns of final granite phases are typical of rare-metal granites. The Ta content in the granites of phase 8 is only slightly lower than that of typical rare-metal granites. Greisenization disturbed the systematic variations in trace element distribution formed during the magmatic stage. The ranges of trace element contents (Rb, Sr, Ta, Nb, and others) and ratios (Rb/Sr, La/Lu, Eu/Eu*, and others) in the Raumid granite overlap almost entirely the ranges of granitic rocks of various compositions, from the least differentiated with ordinary trace element contents to rare-metal granites. This indicates that the geochemical signature of rare-metal granites can develop at the magmatic stage owing to fractional crystallization of melts, which is the case for the melt of the Raumid granite.     

云南个旧杂岩体年代学与地球化学:岩石成因和幔源岩浆对锡成矿贡献

锡矿往往与长英质岩浆岩伴生,然而锡矿形成的热能源区尚不清楚,其可能与地幔物质相关。我国云南锡矿带中出露的中-酸性岩石及碱性岩杂岩体为研究锡矿及其周围岩浆成因提供了良好的物质条件。本文报道了云南个旧地区代表性的花岗岩、辉长-闪长岩和碱性岩类新的全岩地球化学、锆石U-Pb年代学和Hf同位素数据。LA-ICP-MS锆石U-Pb定年表明上述岩石分别形成于81.43±0.46Ma(82.89±0.58M)、81.35±0.22Ma和80.35±0.72Ma,指示它们为晚白垩世近同期岩浆活动的产物。其中闪长岩、碱性岩和花岗岩中锆石的Hf同位素组成不均一,ε_(Hf)(t)分别为-4.2~+0.8、-7.5~-1.9和-8.4~+0.4。尽管这些岩体的侵入时代一致,但它们的地球化学特征和同位素特征存在差异,表明这三类火成岩来自不同的岩浆源区,三者不是同一母岩浆相互演化的关系。个旧杂岩体中花岗岩为弱过铝质岩石,SiO_2与P_2O_5含量呈负相关的关系,排除S型花岗岩的可能。亏损Zr、Nb、Sr、Eu等大离子亲石元素的特征可能为锆石、磷灰石、长石类造岩矿物分离结晶作用的结果;Zr、Nb、Ce和Y总量较低,低的FeOT/MgO比值和低的锆石饱和温度表明,指示出个旧地区的花岗岩应为高分异I型花岗质岩石而非A型花岗岩。个旧地区形成于晚白垩世时期的中基性、碱性岩石可能为不同的幔源岩浆近同时侵入的产物,底侵的幔源熔体带来热量诱发中、下地壳岩石发生部分熔融形成含矿的花岗岩,幔源岩浆对于成矿至少在能量也可能在成矿物质上有重要的贡献。     

LA-ICP-MS微区原位准确分析含水硅酸盐矿物主量和微量元素

通过描述一种利用LA-ICP-MS准确测定含水硅酸盐矿物主量元素和微量元素含量的多外标、无内标分析方法.总结出该方法基于矿物化学计量式计算含水硅酸盐矿物中挥发分的相对含量,再将全部分析元素归一化到总金属氧化物含量(100%减含水量)的原理,利用多种天然成分的岩石标准玻璃(如MPI-DING玻璃和USGS玻璃)作为外标进行校正计算.利用该方法对角闪石、绿帘石、电气石和透闪石等含水硅酸盐矿物进行了分析,并与利用电子探针和微钻(直径300 μm)取样溶液-ICP-MS分析的结果进行了对比研究.研究结果表明:对于组成均一的主量元素的分析结果与电子探针分析数据一致,相对偏差集中在5%以内.除了那些分布异常不均一的元素(在300 μm尺度上),对微量元素的分析结果与溶液-ICP-MS分析结果具有很好的一致性,二者之间的相对偏差大部分集中在10%以内.研究结论为采用归一化校正策略,选择MPI-DING和USGS玻璃作为外标,利用LA-ICP-MS微区分析方法可以准确测定含水硅酸盐矿物中的主、微量元素含量.      

湖北麻城市四道河地区面理化含榴花岗岩的成因

野外和室内研究结果表明,四道河地区面理化含榴花岗岩由古生代沉积岩变质而成。在元素地球化学特征上,具有与岩浆成因的碱性花岗岩一致的特点:高硅(SiO2=75.24%～77.23%)、富碱(Na2O+K2O=6.87%～8.84%)、低铝(Al2O3=11.00%～12.78%);富Rb、Ba、Th、U等大离子亲石元素和Pb,贫Nb、Ta、Zr、Hf等高场强元素;稀土元素含量较高(∑REE=101.08～180.1μg/g),轻稀土元素相对富集(LREE/HREE=3.1～6.8),铕有中等负异常(δEu=0.30～0.68);锆石成因类型及定年结果表明,老核(继承锆石)是异地多时代(元古代-古生代),其寄主岩的原岩是沉积岩,时代不会早于古生代。     

四川冕宁稀土矿床脉石矿物的微量及稀土元素地球化学特征

包裹体地球化学研究表明，四川冕宁稀土矿床中存在着岩浆成因的萤石、重晶石和方解石，它们的微量元素地球化学特征与热液成因对应矿物有明显差别：岩浆成因重晶石相对富集亲石元素，贫亲硫元素；无论是岩浆成因重晶石，还是萤石均明显富集挥发分。稀土元素地球化学研究显示，不同成因萤石、重晶石在稀土元素总量、ＬＲＥＥ／ＨＲＥＥ、（Ｌａ／Ｙｂ）Ｎ、δＥｕ及δＣｅ等一系列稀土元素地球化学参数上都存在明显的差异。该项研究还揭示了岩浆成因萤石、重晶石是在相对还原和酸性体系内结晶而成的。     

滇西剑川始新世富碱岩浆岩锆石U-Pb年代学与Sr-Nd-Hf同位素地球化学及其对岩石成因的制约

滇西剑川富碱岩浆岩位于青藏高原东南缘的三江南段,是金沙江-红河富碱岩浆岩带的重要组成部分。剑川富碱岩浆岩包括花岗岩和正长岩两类岩石,前者主要有花岗斑岩和石英二长斑岩,后者主要是正长斑岩和粗面岩。本文对剑川富碱岩浆岩进行了主微量元素、锆石U-Pb年代学和Sr-Nd-Hf同位素特征研究。锆石U-Pb测年结果显示,剑川花岗岩结晶年龄为35. 1～36. 1Ma,正长岩结晶年龄为35. 7～35. 8Ma,均形成于始新世。花岗斑岩和石英二长斑岩的SiO_2含量为67. 92%～69. 93%,K_2O/Na_2O比值介于0. 86～1. 22,具有高钾钙碱性特征;正长斑岩和粗面岩的SiO_2含量为53. 94%～63. 51%,K_2O/Na_2O比值介于1. 30～2. 68,属于钾玄质岩石系列。两类岩石都富集轻稀土元素(LREE)和大离子亲石元素(LILE),相对亏损高场强元素(HFSE)。其中,花岗斑岩和石英二长斑岩有着较高的Sr、Sr/Y、La/Yb值和低的Y、Yb含量,具有埃达克质岩浆属性。结合Sr-Nd-Hf同位素研究认为,滇西剑川地区花岗岩起源于增厚的镁铁质新生下地壳部分熔融,正长岩是由交代富集的岩石圈地幔熔融产生的基性岩浆演化而来的产物。滇西剑川新生代富碱岩浆活动是对印度与欧亚板块晚碰撞阶段,岩石圈地幔发生对流减薄和软流圈物质上涌过程的响应。     

赣南大吉山与漂塘花岗岩及有关成矿作用特征对比

对江西南部大吉山和漂塘两个钨矿床有关的花岗岩的岩石化学和微量元素地球化学特征、成因及其与成矿的关系等方面进行了对比研究，认为两者不同的成矿作用特征主要是由于大吉山花岗岩比漂塘花岗岩的分异演化程度更高而造成的。对前人提出的含钨花岗岩、含钽铌花岗岩及花岗岩产出的动力学背景等问题，也进行了一些初步讨论。