湘西西安白钨矿矿床的地球化学研究

使用微量元素、同位素和矿物包裹体等方法对湘西西安白钨矿矿床进行了较详细的地球化学研究。认为该矿床属于沉积-改造型层控矿床，并阐述了矿床的矿源层、成矿时代、成矿条件及控矿因素等问题。     

地球化学学科15年回顾

1　地球化学学科 1 5年回顾表 1列出了 1986— 2 0 0 0年期间地球化学学科面上申请项目和资助项目的概况 (1987— 1988和1989年含重点项目 ) ,共资助了 5 4 8项面上项目 (含自由申请项目、青年科学基金项目和地区基金项目 ) ,资助经费为 5 371 0 7万元。 1991— 2 0 0 0年期间批准实施的重点项目有 14项 ,总资助经费 132 6万元。另外 ,地球化学学科还参与了“超高压变质作用与碰撞造山动力学”、“应用于地球科学的加速器质谱计的研制与建立”和国家重点科技项目“夏商周断代工程”的专题之一“加速器质谱计的改进与14 Ｃ测年方法的完善”等…     

麻栗坡新寨锡矿床地质地球化学特征

新寨锡矿床位于滇东南褶皱带的文山－马关隆起，为近年发现的一大型锡矿，矿体产于中寒武统变质岩系，以顺层厚大矿体产出为特征。仅有锡石可利用。中下寒武统中锡丰度比地壳丰度高出数倍至百余倍。为矿源层。氧同位素分析证明有大气降水和变质水参予成矿作用。硫来自火山岩和海水硫酸盐。成矿年龄为２００Ｍａ左右，与区域变质年龄接近，为印支期变质热液改造成矿，属沉积─改造层控型锡矿床。     

江苏溧阳土包山金矿的地球化学特征

江苏溧阳土包山金矿的地球化学特征戴爱华，王华田，袁旭音南京师范大学，南京，２１００２４南京地质矿产研究所，南京，２１００１４关键词：金矿，地球化学，相关分析，聚类分析，江苏溧阳ＴｈｅＣｈｅｍｉｃａｌＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＴｕｂａｏｓｈａｎ...     

古海洋研究中的地球化学新指标

有机地球化学与微量元素地球化学古环境指标及其相关的同位素指标已成为追溯古全球变化与古海洋生物地球化学演化的有力工具。从古环境替代指标的示踪原理和应用的角度，综述了有孔虫碳同位素、有机地球化学整体指标、生物标志化合物、单体有机分子同位素、微量元素等在古海洋古环境研究中的应用及相关的研究动态与进展。指出古海洋研究正从以恢复古海洋的物理参数（温度、盐度、古洋流等）为主，向着揭示古水团演化、古生产力、古营养状况、碳贮库及碳循环等古生物地球化学演化过程方向纵深发展。     

湖南千里山复式花岗岩体的地球化学特征和物质来源

千里山复式花岗岩体是柿竹园大型稀有－有色金属矿床的成矿母岩。它具有高硅、过铝质、富不相容元素、强铕异常、低δＮｄ、较高的（８７Ｓｒ／８６Ｓｒ）ｉ、２０７Ｐｂ／２０４Ｐｂ和δ１８Ｏ值等特征，表明该岩体来源于地壳物质，属陆壳改造型花岗岩。弱的铈负异常以及较古老的Ｎｄ模式年龄进一步证实，原始岩浆主要由区内未出露的中元古宙变质沉积岩部分熔融形成。     

江西金山金矿床成矿地球化学特征

金山金矿床的微量元素，同位素和流体包裹体地球化学特征表明；（1）成矿过程明显复杂于成岩过程，成矿作用中与Au关系最为密切的微量元素是Ag,As,Sb，矿石中若干微量元素丰度低于区域含矿建造丰度，与产于动力变质环境下的韧性剪切带系列金矿床相似；（2）成矿物质主要来自浅变质的中元古界双桥山群含金建造。燕山期岩浆热液活动为该矿床的后期加富提供了部分成矿物质。金山金矿床的层控特征与江南金成矿带中其它金矿极为相似；（3）成矿流体主要为变质-变形过程中产生的变质热流体。再循环大气水和地球深部的高温，高压流体。     

江苏东海毛发状水晶中金红石矿物学、地球化学特征

东海是中国著名的水晶产地,水晶矿床主要产于苏鲁超高压变质带东海境内中,发育于榴辉岩、片麻岩张裂隙中及其接触带中。本文利用背散射图象技术和电子探针定量分析相结合的方法,研究了水晶中的固体包裹体金红石的类型和地球化学特征。结果表明,水晶中金红石主要有4种类型。在背散射图象下,类型2和类型3金红石呈棱角状、不规则状镶嵌于类型1金红石中以及类型3金红石呈不规则状充填于类型2中。类型2金红石表面有较多的裂隙,而类型1、类型3和类型4金红石表面则比较光滑。还没有发现类型4金红石和其它类型金红石之间的明确关系。电子探针分析结果显示,相对其它金红石来说,水晶中的金红石Fe和Nb的含量较高(Fe为2500×10-6-26700×10-6,Nb为782×10-6-6000×10-6);而V和Cr地元素含量则基本相当。在此基础上,本文进一步探讨了水晶中金红石可能的源区。     

CCSD主孔揭示的东海超高压榴辉岩中的金红石：微量元素地球化学及其成矿意义

金红石是榴辉岩中的主要含钛副矿物。中国大陆科学钻探工程主孔100-2000m岩心样品中,金红石榴辉岩、多硅白云母榴辉岩和蓝晶石榴辉岩中都程度不等地含有金红石。金红石既可以与其它矿物一起包裹在主要变质矿物中,也可以呈粒间矿物,但在榴辉岩经受角闪岩相退变质作用过程中,金红石亦会退变为榍石。本文利用电子探针除了分析了金红石的主要元素外,还仔细测量了Nb、Cr、Zr含量。结果显示,Nb平均含量为147ppm,最高含量为670ppm,Cr的平均含量为614ppm,最高含量为3630ppm,低Nb特征(<1000ppm)显示榴辉岩原岩为镁铁质岩石;此外,三类榴辉岩也具有不同的金红石Nb、Cr地球化学特征,即金红石榴辉岩中的金红石表现为低Cr(<500ppm)、Nb变化大(0-670ppm)的特征,多硅白云母榴辉岩中的金红石以中等Cr含量(500-1200ppm)、Nb变化较大(0-480ppm)为特征,而蓝晶石榴辉岩中的金红石显著富Cr(2000-3630ppm),而Nb则非常贫乏(<140ppm)。在总共289个金红石Zr含量数据中,大部分Zr含量分布在150-240ppm之间,均值约为200ppm;利用Zacketal.(2004)提出的金红石温度计,计算得到金红石的形成温度介于690℃和7870℃之间。研究结果表明,金红石的微量元素分析是研究榴辉岩原岩特征及其钛成矿作用的实用方法之一。     

金红石-榍石转变过程中元素地球化学行为——以雅鲁藏布江缝合带角闪岩为例

金红石边缘形成榍石冠状边结构在变质中-基性岩中普遍存在,是金红石与退变质流体携带的SiO_2与CaO作用的结果,反应形成的榍石微量元素特征受到金红石和流体的共同影响。雅鲁藏布江缝合带中角闪岩LZ06-04在抬升过程经历近等温降压退变质作用,石榴子石分解导致同一样品中含石榴子石部分与不含石榴子石部分的退变质流体成分的差异。两种流体分别与金红石反应,对应形成的榍石具有相似的Nb、Ta含量和Nb/Ta比值特征,但截然不同的REE特征。榍石的Nb、Ta来源于金红石,残余金红石与含水流体再平衡Nb、Ta的分配系数增大,且D_(Nb)~(Rt/Fluid)≥D_(Ta)~(Rt/Fluid);虽然Nb和Ta在含水流体中都表现为不活动元素,但相对于Nb,Ta在含水流体中活动性较高。榍石的Zr-Hf体系特征受到锆石、石榴子石等矿物的综合影响,并且Zr-Hf在含水流体中表现出比Nb-Ta更高的活动性。榍石的REE特征受流体中REE特征、榍石与流体配分系数以及共生矿物的影响。在岩浆或变质体系,榍石形成过程中,REE富集矿物(如石榴子石、锆石、褐帘石、独居石、磷灰石等)形成或分解将影响榍石的REE分布特征或形成REE环带结构。含水流体中金红石退变质形成榍石反应的进行受流体中TiO_2、CaO和SiO_2活度的影响。因此榍石常见于钙碱性岩浆岩、富Ca基性变质岩和矽卡岩中。流体中CaO活度的变化影响榍石的形成,进而影响Ti、Nb、Ta在流体中的运移能力。俯冲板片产生流体在交代上覆富Ca地幔楔物质过程中形成榍石残留同样可以造成部分熔融体具有亏损HFSE特征。     

Reconnaissance assessment of the Stenian-Tonian granitoids of southern Tanzania for metal resources by using geological remote sensing and geochemical techniques

This study presents the use of geological remote sensing and geochemistry to determine spatial extents, geochemical characteristics and petrogenetic origin of Ndanda-Masasi metagranitoids in order to explore for important metals (Sn, W, Ta and Nb) in the metagranitoids. Geological remote sensing was done using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, and major and trace elements were analysed using a combination of Inductively Coupled Plasma Mass Spectrometer (ICP-MS) and Inductively Coupled Plasma Emission Spectrometer (ICP-ES). It has been revealed that the metagranitoids and other rocks in the Ndanda-Masasi area crop out in a larger spatial coverage than how it is depicted in available geological maps. Moreover, the meta-granitoids have variable SiO₂ contents, low Mg, Ni and Cr concentrations and moderate to large Fe-numbers. They classify mainly as magnesian- and ferroan-type granites and minor granodiorite and quartz monzonite. The chondrite normalized Rare Earth Elements (REE) patterns of the rocks show slight to strong enrichment of light REE over middle REE and heavy REE ((La/Yb)_N = 4.2–289.1), due to their variable contents of MREE and HREE. The rocks show flat patterns of middle REE and heavy REE and have negative Eu-anomalies (mean Eu/Eu* = 0.7), with the exception few rocks in some localities yielding positive Eu-anomalies. They are characterised by variable Sr/Y (4.7–356.7), Nb/Ta (2.6–44.5) and well correlated trends with negative slopes of SiO₂ vs MgO, TiO₂, CaO, and Al₂O₃ diagrams. These geochemical features reflects a most likely magmatic formation of the rocks in the presence of plagioclase, hornblende, garnet and rutile, or/and fractionation of the phases at variable crustal depths. Numerous myrmekites forming convex grain boundaries around K-feldspar in the rocks indicate Ca- and Na-metasomatism as an important process affecting the rocks in their evolution. The omnipresent retrograde assemblage of titanite, chlorite, epidote and muscovite forming at the expense of plagioclase, hornblende, biotite and opaque (Fe-Ti-oxides?) reflects their formation during uplifting history of the rocks. Contrary to granitoids of similar age such as those of the Karagwe-Ankolean Belt, which are metalliferous, our reconnaissance survey found that the Ndanda-Masasi meta-granitoids have uneconomic concentration of most important metals.     

金红石中锆含量温度计及其微量元素地球化学特征

Zack et al.(2004a)、Watson et al.(2006)以及Tomkins et al.(2007)(在2GPa条件下)的金红石中锆含量温度计计算结果显示,徐淮地区中生代侵入杂岩所含榴辉岩类包体所经历的榴辉岩相变质的温度范围分别为776～1099℃(平均898℃)、663～923℃(平均750℃)和714～981℃(平均804℃),这些温度结果可能并非榴辉岩相峰期变质温度;其角闪岩相退变质作用过程中保存的温度范围分别为555～777℃(平均697℃)、541～663℃(平均6170C)和588～714℃(平均667℃),这些结果不能代表角闪岩相退变质再平衡后的温度,而只能代表角闪岩相退变质作用过程中某-阶段的温度.微量元素地球化学特征研究表明,榴辉岩类包体所含金红石中的某些微量元素(如Nb、Ta、Cr、Fe、V等)含量与其原岩有继承和对应关系,其原岩主要为镁铁质岩石;榴辉岩类包体与其寄主岩石中部分高价态/高场强元素(HFSE)呈相互消长的关系.榴辉岩的形成与扬子地块和华北地块之间的俯冲,碰撞作用有关.     

班公湖-怒江成矿带西段角西石英脉型钨矿床地质特征及黑钨矿地球化学特征

角西矿床是班公湖-怒江成矿带上目前发现的首例石英脉型钨矿床。本文对该矿床的地质特征及黑钨矿微量、稀土元素进行了系统的研究。结果表明,角西矿床主要发育与中新世花岗岩密切相关的含黑钨矿(±白钨矿)石英脉,矿脉主要受张性裂隙控制,宽度在0. 02～2m之间,"五层楼"分带模式较为明显,蚀变类型主要为云英岩化和角岩化。矿化可以分为氧化物阶段、硫化物阶段和萤石-碳酸岩阶段。与华南同类型矿床相比,角西黑钨矿的稀土元素含量极低(∑REE=0. 560×10~(-6)～1. 186×10~(-6)),具有较为明显的正Eu异常。黑钨矿中相对富集Sc元素(平均31. 15×10~(-6))的特征表明成矿流体富含F-和/或PO_4~(3-)离子。以上研究成果不仅有助于加深该矿床成因的认识,而且为后续矿床勘查提供了重要信息。     

Defining the geochemical baseline: a case of Hong Kong soils

A geochemical baseline provides the means to distinguish between the pedogenic origin and the anthropogenic origin of the trace element in the environmental compartments. We collected 271 soil samples representative of different parent rocks and soil types from the whole territory of Hong Kong and analyzed the composition of clay mineralogy and the contents of 15 chemical elements (Fe, Cd, As, etc.) for these samples. The baseline was predicted with the method of the normalization procedure combined with the relative cumulative frequency curve. The result indicated that Fe was the best reference element for the normalization procedure among the five potential reference elements (Fe, Al, Sc, Ti, and Mn), followed by Sc and Ti. A poor correlation was found between Sc, Ti, and Cu. The predicted baseline was much lower than the A-value of the Dutch List used usually in screening the polluted soil of Hong Kong, implying that the extent of heavy metal pollution might have been underestimated with respect to local lands. We also applied the cluster analysis to distinguish the geochemical associations of the trace elements due to its importance to the baseline. Approximately three major associations including the Fe–Mn-oxides related, Al oxides or Al-bearing-clay-mineralogy related and sulfide- related associations were observed from the dendrogram.     

阿尔金山南缘长沙沟镁铁-超镁铁质层状杂岩体的发现与地质意义——岩石学和地球化学初步研究

阿尔金山南缘地区,侵入于新太古界—新元古界变质地层中的长沙沟镁铁-超镁铁质岩由四个呈断层接触的镁铁-超镁铁质岩块组成,形成年龄为462~470Ma。不同岩块内岩石的地球化学特征虽有差异,但均以LREE及强不相容元素的富集和高的Zr/Y比值（＞4.1）为特征,形成于大陆裂谷环境。其中,清水泉北段可以划分出3~4个主体由辉橄岩-角闪辉长岩构成的岩浆旋回,具有层状岩体的特征,其母岩浆的Mg^#=53.7~55.9,为演化型母岩浆,暗示其经历了富镁矿物的分离结晶,且(Th/Nb)_N＞1.0、Nb/La比值＜1.0、以及发育的矿物逆序包裹现象等表明经历了明显的地壳混染和岩浆混合作用;而清水泉南和长沙沟中段镁铁-超镁铁质岩的(Th/Nb)_N＜1.0、Nb/La比值＞1.0,基本未遭受地壳混染,并且此Mg^#与FeO^T、TiO₂负相关、与SiO₂正相关,呈现良好的Fenner演化趋势特征;清水泉南纯橄岩-辉橄岩具有极高的Mg^#（90.6~84.5）,而赋存有钛-磁铁矿工业矿体的长沙沟中段镁铁-超镁铁岩的Mg^#值较低（75.8~49.2）,推测它们是同一母岩浆（Mg^# =78.2）经Fenner演化趋势后分别形成的早期富Mg矿物堆晶相和稍晚期的富Fe-Ti残余岩浆相。长沙沟中奥陶世裂谷型层状镁铁-超镁铁质杂岩体的发现,意味着这一时期阿尔金山南缘地区处于伸展背景下,具有形成岩浆型PGE-Cu-Ni硫化物矿床和V-Ti-Fe氧化物矿床的地质背景和重要的成矿物质载体。作为该地区一种新的找矿思路,该地区同一构造带内其它镁铁-超镁超镁铁质岩体的性质及可能的金属矿化作用等也是值得进一步研究探索的。     

An experimental study of the grain-scale processes of peridotite melting: implications for major and trace element distribution during equilibrium and disequilibrium melting

The grain-scale processes of peridotite melting were examined at 1,340°C and 1.5 GPa using reaction couples formed by juxtaposing pre-synthesized clinopyroxenite against pre-synthesized orthopyroxenite or harzburgite in graphite and platinum-lined molybdenum capsules. Reaction between the clinopyroxene and orthopyroxene-rich aggregates produces a melt-enriched, orthopyroxene-free, olivine + clinopyroxene reactive boundary layer. Major and trace element abundance in clinopyroxene vary systematically across the reactive boundary layer with compositional trends similar to the published clinopyroxene core-to-rim compositional variations in the bulk lherzolite partial melting studies conducted at similar P–T conditions. The growth of the reactive boundary layer takes place at the expense of the orthopyroxenite or harzburgite and is consistent with grain-scale processes that involve dissolution, precipitation, reprecipitation, and diffusive exchange between the interstitial melt and surrounding crystals. An important consequence of dissolution–reprecipitation during crystal-melt interaction is the dramatic decrease in diffusive reequilibration time between coexisting minerals and melt. This effect is especially important for high charged, slow diffusing cations during peridotite melting and melt-rock reaction. Apparent clinopyroxene-melt partition coefficients for REE, Sr, Y, Ti, and Zr, measured from reprecipitated clinopyroxene and coexisting melt in the reactive boundary layer, approach their equilibrium values reported in the literature. Disequilibrium melting models based on volume diffusion in solid limited mechanism are likely to significantly underestimate the rates at which major and trace elements in residual minerals reequilibrate with their surrounding melt. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spatial distribution of major and trace elements in shallow reservoir sediments: an example from Lake Waco, Texas

 Sediment geochemistry of a shallow (6-m average) reservoir (Lake Waco) was evaluated for the spatial distribution of major and trace elements. Sixty bottom and core samples along a 21-km transect within the reservoir, 18 overbank sediment samples, and 8 rock types in the drainage area were collected and analyzed for major (Al, Ca, Fe) and trace elements (As, Ba, Cr, Cu, Hg, Mn, Ni, Pb, Sr, V, Zn). Elemental concentrations in the reservoir sediments closely correspond to concentrations in the regional rocks and represent a mixture of overbank sediment composition of the tributaries. Elemental concentrations were statistically regressed against Al concentrations in order to establish regional baseline levels and thereby distinguish natural from anthropogenic sources. Spatial geochemical trends, considered in terms of element-to-Al ratio versus V-to-Al ratio, relate to the natural and anthropogenic sources contributing to the elemental concentrations. The spatial elemental distribution in the reservoir, which receive sediments from two mineralogically contrasting basins, reflect textural and mineralogical transition within the reservoir and suggest a progressive mixing of sediment from the tributaries. The spatial elemental distribution and sediment texture suggest that the sediment-source, which determines the sediment-type, has a greater influence on the major- and trace-element distributions in shallow reservoir sediments than bathymetry. Received: 25 September 1997 · Accepted: 3 February 1998     

MATPLOT:一款基于MATLAB的地球化学数据分析成图软件

地球化学数据统计分析图解是目前岩石地球化学研究工作中常用的手段。目前常用的软件或多或少都存在一些不足之处。本文提出的MATPLOT是一款应用MATLAB编写而成的地球化学数据成图软件,可以在Windows/Mac OS/Linux多种操作系统平台中运行。与现有常用软件相比,该软件更具优势：可以更方便地实现较大地球化学数据量的导入,无需对数据进行繁琐的格式整理;更便捷地对数据进行二元散点图、三角图、标准化折线图、柱状图、概率密度图和同位素演化图等6种常用图解类型的成图,以及对数据图的展示内容和效果进行各种调整。此外,MATPLOT还可以对数据进行多种平均值计算（普通平均值、图基双权加权平均值和误差相关加权平均值）和相关性分析。