浙江漓渚矽卡岩型铁矿床的矿物学特征与成因

浙江漓渚铁矿床系钦杭成矿带东段一典型矽卡岩型矿床,矿体呈透镜状、似层状、不规则状等,产于广山复式花岗岩体外接触带的南华系、震旦系、寒武系和奥陶系层间的矽卡岩中。矿区发育透辉石、石榴子石、铁浅闪石、金云母、绿泥石、榍石等矽卡岩矿物,金属矿物主要包括磁铁矿、黄铁矿、方铅矿、闪锌矿、辉钼矿等。作者利用电子探针技术对漓渚铁矿床中的矽卡岩矿物进行了系统分析,结果表明:漓渚铁矿床矽卡岩演化经历了矽卡岩期和热液蚀变期,其中,矽卡岩期包括辉石-石榴子石阶段、磁铁矿阶段和角闪石-金云母阶段;热液蚀变期包括石英-硫化物阶段和石英-碳酸盐阶段。辉石以透辉石为主,有向钙铁辉石演化的趋势,即Mg+2→Fe+2演化;石榴子石由钙铝榴石向钙铁榴石转变,显示Al+3→Fe+3演化,这些矿物学特征反映了矽卡岩早期的成矿流体中Fe逐渐增加,且氧逸度f(O2)逐渐升高。铁浅闪石具有富Na、K的特征,且铁浅闪石、金云母和榍石等富F以及矽卡岩萤石化现象,反映成矿流体呈碱性、具有富F的特征,有利于Fe的迁移、富集、成矿。漓渚铁矿床的形成与区内广山-柵溪岩体的岩浆活动有关,Fe可能来源于多期岩浆热液。     

南秦岭柞水-山阳矿集区小河口矽卡岩型铜矿床矿物化学及其成矿意义

秦岭造山带燕山期斑岩-矽卡岩型铜矿床因过去发现的数量有限,限制了对区内铜矿床成矿机制的深入研究。小河口铜矿床是南秦岭柞水-山阳矿集区内的典型矽卡岩型铜矿床,矿体产于燕山期花岗闪长玢岩与泥盆系桐峪寺组地层接触处的矽卡岩带内。成矿作用划分为4个阶段:Ⅰ干矽卡岩阶段、Ⅱ湿矽卡岩-氧化物阶段、Ⅲ石英-硫化物阶段和Ⅳ碳酸盐-石英阶段。本文在对该矿床矽卡岩矿物(石榴子石和辉石)和金属矿物(磁铁矿和硫化物)详细的岩(矿)相学观察基础上,针对这些矿物进行系统的电子探针成分分析,来示踪矽卡岩的成因和形成环境,讨论成矿元素的沉淀富集过程。研究表明,小河口铜矿床为典型的接触交代成因钙质矽卡岩型矿床。干矽卡岩矿化阶段从早到晚依次形成钙铝榴石(Adr_(24-31)Gr_(68-74))、钙铝榴石组分-钙铁榴石组分交替系列(Adr_(26-68)Gr_(31-72))和透辉石(Di_(73-91)Hd_(8-24))-纯钙铁榴石(Adr_(68-100)Gr_(0-30))。伴随着岩浆结晶分异,初始岩浆-热液流体与灰岩发生接触交代作用首先形成无环带钙铝榴石(Grt-a)矽卡岩,此时成岩环境为低氧逸度、酸性还原环境,不利于矽卡岩铁、铜矿化的形成;成矿流体不断从岩浆中出溶并发生多次沸腾,引起残留热液的氧化还原状态发生周期性变化,成矿热液由酸性逐渐向弱碱性演化,进而导致Fe~(3+)和Al~(3+)活度的变化,在振荡的物理化学环境中形成了钙铝榴石-钙铁榴石组分交替生长的宽环带石榴子石(Grt-c)矽卡岩;随着岩浆演化和流体作用的扩大,成矿体系处于较稳定的碱性和高氧逸度环境,Fe和Al的过饱和程度此消彼长,形成了透辉石-密集振荡环带钙铁榴石(Grt-b和Grt-d)矽卡岩。成矿流体演化进入湿矽卡岩-氧化物阶段后,富含挥发分的热液活动起主导作用,沸腾作用将H~+和CO_2分离进入气相,导致流体体系碱性和氧逸度程度进一步升高,进而形成磁铁矿和镜铁矿大量沉淀富集。石英-硫化物阶段,随着温度和氧逸度骤减导致黄铁矿、磁黄铁矿和黄铜矿等硫化物发生沉淀,并以石英-硫化物脉的形式充填于构造裂隙或矽卡岩内。     

湖北铜绿山矽卡岩型铜铁矿床同位素地球化学研究

湖北铜绿山铜铁矿床处于长江中下游铁铜成矿带西部鄂东成矿区内,是鄂东南地区典型的矽卡岩型铜铁矿床。矿体呈透镜状产于下三叠统大冶群第3至第7岩性段大理岩与铜绿山岩体的接触带。矿床成矿过程大致划分为干矽卡岩阶段(Ⅰ)、湿矽卡岩阶段(Ⅱ)、氧化物阶段(Ⅲ)、石英硫化物阶段(Ⅳ)和碳酸盐阶段(Ⅴ)。矿石矿物主要有磁铁矿、黄铜矿、赤铁矿;脉石矿物以石榴石、石英、碳酸盐矿物为主。通过对铜绿山铜铁矿床硫、氢、氧、碳和铅同位素组成研究,探讨成矿流体来源和成矿物质来源。研究表明,成矿流体早期以岩浆热液为主,有少量大气降水加入,后期大气降水比重加大;热液中的碳主要为深源岩浆来源,少量来自海相碳酸盐岩的溶解作用;矿石中硫化物的硫同位素组成特征反映了硫来自深源岩浆;矿石铅同位素组成稳定,为正常铅,矿石铅源于上侵过程中受地壳物质混染的幔源岩浆。     

宁芜地区梅山铁矿床矿物的电子探针分析和稀土元素地球化学特征

梅山铁矿床位于长江中下游成矿带宁芜盆地北段,矿体赋存于辉长闪长玢岩和下白垩统大王山组辉石安山岩的接触带。研究表明,梅山铁矿的石榴石以钙铁榴石为主,为钙铁-钙铝榴石系列,与传统意义矽卡岩矿床的石榴石组成相似;磁铁矿和赤铁矿具有斑岩铜矿和Kiruna型矿床的双重特征;赤铁矿和菱铁矿显示热液交代成因特征,但赤铁矿至少有2个成矿世代。成矿母岩辉长闪长玢岩、磁铁矿及磷灰石具有相似的稀土配分模式,暗示三者具有同源性。辉长闪长玢岩无Eu异常,代表了高氧逸度下岩浆的分离结晶作用;磁铁矿和磷灰石均具有中度负Eu异常,可能是在辉长闪长玢岩发生钠长石化的过程中,Eu以Eu2+形式在钠长石内富集,造成流体Eu亏损,后来生成的磷灰石和磁铁矿继承了流体的Eu含量特征,辉长闪长玢岩的钠长石化导致富Fe2+硅酸盐矿物淋滤铁元素进入流体,为矿床提供了铁物质。     

新疆西天山智博铁矿床地球化学及同位素特征

智博铁矿位于新疆西天山阿吾拉勒铁成矿带东段,矿体以层状、似层状、透镜状产出于下石炭统大哈拉军山组玄武质安山岩中。智博铁矿成矿作用主要划分为岩(矿)浆期和热液期2个成矿期次,包括3个成矿阶段:磁铁矿+透辉石阶段、磁铁矿+绿帘石+钾长石阶段和石英+硫化物+碳酸盐阶段。智博铁矿地球化学特征表明,其成矿构造背景为早石炭世南天山洋向伊犁板块俯冲形成的岛弧环境;火山岩与磁铁矿石具有相同的物质来源,均来源于受俯冲带流体交代的亏损地幔楔部分熔融形成的玄武质岩浆。智博铁矿为岩浆(主要)-热液(次要)复合型矿床,受俯冲流体交代的亏损地幔楔部分熔融形成富铁的玄武质岩浆,岩浆沿深大断裂上侵形成早期火山岩,上侵过程中由于物理化学条件的改变在不混溶作用下形成铁矿浆,铁矿浆侵入早期火山岩地层形成岩浆期磁铁矿体;后期富铁的岩浆或矿浆热液使围岩发生矿化与蚀变,形成热液期磁铁矿体。     

印尼某矿区铁矿床地质特征及成因分析

通过对印尼某矿区磁铁矿矿床区域地质背景、矿床地质特征分析,认为该矿床形成于印支期,其形成与强烈的区域性花岗质岩浆侵位活动有关,成矿物质主要来自花岗质岩浆晚期—期后热液.研究表明,花岗岩浆经过了充分的分异演化,在结晶成岩的过程中,大量铁质从岩浆中分离出来,形成富铁熔浆贯入充填成矿,随着温度的降低,形成的含铁质成矿流体与Pzmm中的碳酸盐层或钙质粉砂岩发生接触交代而形成矽卡岩型铁矿.矽卡岩型是矿区的主要成因类型.     

巴音布鲁克铁矿床成矿特征及找矿标志研究

新疆和静县巴音布鲁克铁矿床位于南天山造山带北部,产于上志留统巴音布鲁克组与海西中晚期中酸性侵入岩接触带矽卡岩中矿床成矿母岩为正长花岗岩,成矿方式主要为交代作用.围岩蚀变强烈,主要为各种矽卡岩矿物组合,与磁铁矿关系密切.该矿床成因类型属以酸性岩浆与碳酸盐地层接触交代形成的矽卡岩型铁矿床研究对比发现,可利用区域侵入岩标志、...     

东天山红云滩铁矿稳定同位素地质特征及其对成矿作用过程的指示

东天山觉罗塔格红云滩铁矿大多被认为是海相火山岩型铁矿, 该类矿床的成矿机理通常被描述为早期形成的矿源层被后期热液交代改造富集。本文通过对红云滩铁矿稳定同位素特征的研究发现, 该矿床其实为特定火山岩层经过前期广泛碱交代,然后叠加矽卡岩化而形成的热液交代矿床。成矿过程先后分为五个阶段: 火山岩矿源层形成、碱交代、矽卡岩蚀变、磁铁矿生成和石英-硫化物沉淀。在红云滩铁矿成矿过程中, 成矿流体是不断的演化的: 在最初红云滩岩体石英形成阶段, 可能就有少量大气降水的参与使其石英的氢同位素亏损2H; 在大量矿石矿物磁铁矿形成阶段, 可能有较多大气降水的流体加入使磁铁矿亏损18O; 在成矿后期大量石英和硫化物形成阶段, 有大量大气降水加入, 此时成矿流体则不但继承了先前岩浆热液低?D值的特征, 也继承了磁铁矿形成期流体?18O值稍低的特征, 不同于岩浆水也区别于变质水。     

黑龙江省三矿沟夕卡岩型铁铜矿床矿物学特征及成矿物理化学条件

黑龙江三矿沟铁铜矿床位于大兴安岭北段多宝山矿集区,矿体产于燕山期侵入岩与奥陶系多宝山组大理岩接触带的夕卡岩内。根据矿物共生组合及交代关系,确定热液成矿过程包括夕卡岩阶段、退夕卡岩阶段和石英硫化物阶段。铁矿化主要发生在退夕卡岩阶段,形成磁铁矿、镜铁矿等铁氧化物,呈浸染状、条带状、块状产于钙铁榴石夕卡岩中。铜矿化主要发生在石英硫化物阶段,形成黄铜矿、斑铜矿等硫化物,交代早期矿物。电子探针分析等研究表明,三矿沟铁铜矿床发育钙质夕卡岩矿物组合,其石榴子石主要为钙铝榴石和钙铁榴石,辉石为透辉石钙铁辉石系列,角闪石属于钙角闪石系列,绿泥石属于I型三八面体富铁绿泥石。石榴子石有3种类型：早期自形粗粒的钙铝榴石(Grt-Ia)和钙铁榴石(Grt-Ib),以及晚期呈脉状产出的钙铁榴石(Grt-Ⅱ)。夕卡岩阶段成矿流体具有高温、弱酸性、高氧逸度的特征;退夕卡岩阶段流体温度降低,pH升高,形成大量铁氧化物;石英硫化物阶段流体温度和氧逸度降低,金属硫化物沉淀。     

山东大张矽卡岩型铁矿床中铁的富集机制 ——来自流体包裹体和氢、氧同位素的证据

大张铁矿是鲁西地区近年来新发现的一个重要的矽卡岩型矿床.矿体主要赋存于石英二长闪长岩与奥陶系马家沟组灰岩接触带及其附近.根据脉体穿插关系和交代蚀变特征,将大张矽卡岩型铁矿床成矿过程划分为矽卡岩阶段、氧化物阶段、硫化物阶段和碳酸盐阶段.通过对透辉石、绿帘石、石英和方解石等透明矿物显微观察发现,大张铁矿中流体包裹体类型主要...     

截潜工程在计算山前侧向补给量中的应用

在计算山前侧向补给量的方法中,最常用的就是达西断面法,但达西断面法需要获取较多的参数,对于山前无钻孔或只有少量钻孔且水文地质研究程度较低的区域,很难采用达西断面法来计算得到山前侧向补给量。对于无法运用达西断面法但存在完整式截潜工程的山丘区,可以结合完整式截潜工程的截潜量利用水量均衡法计算山前侧向补给量。     

Global repeating events in the history of the Earth and the motion of the Sun in the Galaxy

Chronological analyses of correlations between certain global repeating events (mass extinctions of marine organisms, meteorite impacts, and flashes in the frequency of geomagnetic reversals) during the Phanerozoic Eon and the motion of the solar system in the Galaxy are presented for five rotationally symmetrical models for the regular Galactic gravitational field. Thirteen of sixteen mass-extinction events can be described by a repetition interval of 183±3 million years. This is in agreement with the anomalistic period (interval between two subsequent passages of the Sun through the apocenter of its Galactic orbit) in the model of Allen and Martos. The positions of the minima and maxima in Gaussian functions approximating the frequency distribution for geomagnetic reversals also agree with the times of passage of the Sun through the apocenter and pericenter, respectively, of its Galactic orbit in this model. The maximum in the distribution of the deviations of the dates of mass extinctions from the nearest dates of impacts of large, crater-forming bodies is close to zero, providing evidence that many such events are correlated. As a rule, extinctions follow impact events. The impacts of large bodies have occurred most often when the solar system passes through the Galactic plane, while mass extinctions occur more often at some distance from the Galactic plane (about 40 pc). As a rule, intervals of increases in the frequency of geomagnetic reversals coincide with dates of impacts of large bodies. At the same time, these intervals do not show a clear correlation with the dates of mass extinctions. The intensity of mass extinctions, like the energy released by impacts, is consistently higher in periods when the Sun is moving from the apocenter toward the pericenter of its orbit, than when it is moving from the pericenter toward the apocenter. Thus, there is evidence for a variety of relationships between repeating global events in the Phanerozoic and the motion of the Sun in the Galaxy. Long-period variations in the frequency of geomagnetic reversals are correlated with the orbital motion of the Sun, and increases in the frequency of geomagnetic reversals are correlated with impacts. Mass extinctions are correlated with the impacts of large bodies, whose motions may have been perturbed by clouds of interstellar material concentrated toward the Galactic plane and by the shock front associated with the Perseus spiral arm, through which the solar system passes. The velocity of the Sun relative to the spiral pattern is estimated.     

"青藏高原南部空白区基础地质调查与研究"计划项目新成果、新进展

通过2004年度各相关图幅的大力工作，在基础地质、矿产和资源等方面取得了大量实际材料，综合研究区域构造．地层格架、青藏高原地质图和青藏高原南部火山岩及其地球动力学意义等，取得重要进展和新认识，在矿产资源、旅游和人文景观等方面也取得重要阶段性成果。     

“青藏高原南部空白区基础地质调查与研究”计划项目新成果、新进展

通过2 0 0 4年度各相关图幅的大力工作,在基础地质、矿产和资源等方面取得了大量实际材料,综合研究区域构造地层格架、青藏高原地质图和青藏高原南部火山岩及其地球动力学意义等,取得重要进展和新认识,在矿产资源、旅游和人文景观等方面也取得重要阶段性成果。     

关中盆地大荔地区地下水氟水文地球化学规律

为了研究关中盆地大荔地区氟的水文地球化学规律,采集239个地下水样品及35个土壤样品,分析了水化学类型和水化学组分对氟的影响,结果表明在弱碱性环境下,重碳酸钠型是促进氟富集并增强围岩向地下水中转化的主要因素;硫酸钙镁型的地下水抑制氟富集。水化学组分中Na+、Cl-、HCO3-、pH与氟呈正相关,而Ca2+则抑制水溶液中氟含量增加;迁移系数与HCO3-、pH呈正相关关系,与其他主要离子呈负相关关系。利用Preeqic软件分析了饱和指数和Ca2+、F-的离子活度,得出萤石的平衡控制着氟和钙的水文地球化学行为,F-可能来源于萤石和方解石的分解。     

Determination of Emissions in the City by the Rate of Change in the Integral Content of Impurities in the Atmospheric Boundary Layer

Doklady Earth Sciences - A new approach to the problem of determining the density of emission fluxes of anthropogenic impurities from distributed urban sources by the rate of growth of the integral...     

Terrane tectonics in the formation of the groundwater runoff in the active water-exchange zone of mountainous river valleys in the cryolithozone

The significant role of the drainage area’s geological background in the formation of the groundwater runoff in the active water-exchange zone was revealed for the first time on the basis of long-term observations of streams of the Upper Kolyma River region during the autumn-winter low-water period, when the rivers are fed only by the groundwater recharge. The analysis of all the available data made it possible to define the characteristic periods in the autumn-winter low-water season. The waters of the seasonally thawed layer play the dominant role in the river’s recharge in September; the suprapermafrost water, in January; and the subgelisol water (nonfreezing water streams) during the 30-day-long period of the minimal flow. The quantitative parameters of the groundwater runoff corresponding to its module during this period reflect the water influx to the active water-exchange zone. It is established that the latter is minimal in the In’yali-Debin synclinorium, which consists of sedimentary rocks formed in deepwater trough environments. Their subsequent transformation proceeded under the action of subduction-accretionary and shear strains. The water availability in the active water-exchange in the Ayan-Yuryakh anticlinorium zone is substantially higher, although the Late Paleozoic and Early Mesozoic sedimentary formations of this area were also deposited in deepwater trough settings, but their subsequent evolution was related to the uplift of the anticlinorium. The maximal watering is observed in the active water-exchange zone of the Omulevka terrane, which is composed of Paleozoic terrigenous-carbonate and carbonate formations. The differences in the hydrogeological regimes of the terranes may be significant with respect to their geoecology.