微磁测量在坦桑尼亚构造蚀变岩型金矿床上的应用研究

构造蚀变岩型金矿床是坦桑尼亚绿岩带重要的金矿床类型.金矿脉和它所赋存的构造蚀变带与周围背景岩石磁性差异较小,高精度磁测难以反映出构造蚀变带和金矿脉引起的微弱磁场特征,为了获取构造蚀变带和金矿脉引起的精细磁场结构,在选择的单元测区(主要矿脉分布区)内进行了高密度、高精度、高分辨微磁测量(20 m×5 m)精细研究;微磁异常清晰地反映了构造蚀变带和金矿脉群引起的磁场特征,为钻探工程布置提供了充分的依据,起到了良好的找矿效果.研究认为寻找构造蚀变岩型金矿的微磁测量流程为:(1)开展1∶1万地面高精度磁力扫面测量,大致圈定找矿靶区和选择单元测区;(2)单元测区内进行微磁测量,获取精细地磁场结构;(3)微磁异常上布置微磁剖面测量(点距2 m),定位构造蚀变带和金矿脉.微磁测量对坦桑尼亚其他绿岩带以及我国(乃至世界)绿岩带地区寻找构造蚀变岩型金矿也具有良好的示范和指导意义.     

坦桑尼亚凯巴卡瑞地区构造蚀变岩型金矿航磁异常特征与找矿意义

坦桑尼亚是东非第一产金大国,构造蚀变岩型金矿是该国的一个重要金矿床类型,该类型金矿床与断裂构造中的构造蚀变带密切相关,主要分布在坦桑尼亚环维多利亚湖东部、西南部及东南部绿岩带中;凯巴卡瑞地区内岩石磁性表现为强-中-弱-微或无的强度等级,岩石相互之间磁性差异明显,其航磁异常显示的地质信息比较详尽,反映的磁性地层、岩体界线清晰,线性构造特征明显.依据坦桑尼亚凯巴卡瑞地区尼亚斯罗利金矿床上的航磁异常表现形式,对凯巴卡瑞地区航磁异常强度、规模、形态及延伸等特征进行了认真分析和对比研判,认为该区域航磁异常客观地反映了与构造蚀变岩型金矿有关联的断裂构造和绿岩分布区,构造蚀变带、金矿脉以及所赋存的绿岩地层在航磁异常上表现为低强度磁异常,其他岩石(条带状铁建造、辉绿岩、花岗岩)在航磁异常上表现为高强度磁异常,据此选择的找矿靶区通过地面物探方法(高精度磁测、微磁测量)查证,取得了明显的找矿效果;凯巴卡瑞地区航磁异常解译厘定的地质信息,为进一步预测成矿区域、圈定找矿靶区及间接发现构造蚀变岩型金矿床奠定了基础,因而预判坦桑尼亚凯巴卡瑞地区分布的航磁异常具有寻找构造蚀变岩型金矿的较大潜力.     

安徽省霍山县东溪-南关岭金矿地质特征与成矿条件

东溪-南关岭金矿为北淮阳东段发现的第一个原生金矿,产于磨子潭-晓天中生代火山盆地边缘,容矿围岩为安山质-英安质火山岩,矿化和蚀变受桐柏-桐城深大断裂带的次级构造带控制。该金矿发育陡倾斜的脉状矿体和缓倾斜的似层状矿体,成因类型为冰长石-绢云母型浅成低温热液金矿。火山岩盆地之下的变质基底可能起到了初始矿源层作用,桐柏-桐城断裂带及其次级构造破碎带为重要的导岩导矿构造,早白垩世强烈的岩浆活动提供了热源、动力源和部分矿源。参照国内外类似金矿的特征,认为本区成矿地质条件良好,有可能隐伏着与石英正长岩体有关的细脉浸染型矿化,晓天火山盆地具有良好的找矿前景。     

坦桑尼亚环维多利亚湖地区金矿勘查地球物理方法应用研究

坦桑尼亚环维多利亚湖地区绿岩带是东非重要的太古宙金成矿带,由于受到准平原化作用的影响,总体覆盖较厚、较广,常规的地质填图和找矿方法效果不佳,地球物理勘查方法在金矿资源勘查中发挥了至关重要作用,为大型隐伏铁建造(BIF)型姆瓦莫拉金矿和中型构造蚀变岩型尼亚斯罗利金矿的发现起到了关键性的指导作用;以环维多利亚湖地区金矿床的成矿地质条件、岩石物理性质、地球物理场特征等信息为基础,以姆瓦莫拉金矿和尼亚斯罗利金矿为典型案例,系统总结了坦桑尼亚金矿床有效的地球物理勘查技术方法,首次归纳建立了该国境内铁建造型金矿、构造蚀变岩型金矿的地球物理找矿模型,并提出了物探勘查这两种类型金矿床可采取的最佳方法组合模式,对进入坦桑尼亚的世界各国地勘部门寻找金矿具有一定的借鉴作用和参考意义.随着我国对海外矿产勘查热度的增大,坦桑尼亚金矿床地球物理勘探方法和工作模式对世界上其他国家或地区绿岩带型金矿勘查、评价及找矿方向也具有重要指导意义.     

河南省嵩县东湾—蛮峪金矿床地质特征及找矿意义

本文通过对东湾金矿矿区的地质概况、矿床地质特征的分析研究，得出东湾金矿是岩浆热液形成的构造蚀变岩型金矿，成矿时代属燕山晚期，燕山期岩浆活动不仅提供强大的热动力条件，而且还从矿源层中携带大量的成矿物质，在构造有利部位，尤其是NNE向断裂构造部位沉淀富集成矿，总结出了找矿标志和预测了今后的找矿方向。     

江苏盱眙金矿化带的基本特征及找矿远景

江苏盱眙金矿化带位于古桑乡石牛山－小团山－带,根据土壤和基岩的化探资料,确定了６个金异常点;通过１：１万地质草测,确定了区内矿化带的空间分布、规模和产状。金矿化主要与南北向断裂有关。围岩蚀变主要有硅化、碳酸盐化及褐铁矿化。金矿化可分两类：一是破碎蚀变岩型,二是侵入接触带型。前者是在地层间的平缓碎裂岩和糜棱岩带,具泥化或红土化现象;后者系岩体与地层接触,形成硫化的或铁帽。盱眙一带金矿找矿前景以断裂附     

坦桑尼亚条带状铁建造和辉绿岩磁异常特征的识别与找矿研究

含铁建造型金矿和构造蚀变岩型金矿是坦桑尼亚国主要的金矿类型,含铁建造型金矿与条带状含铁建造(BIF)密切相关,而构造蚀变岩型金矿则与热液构造活动有一定的联系,条带状含铁建造(磁铁石英岩)和辉绿岩二者具有强磁性,不仅都能够在地表引起很强的ΔT负磁异常,而且其异常形态有很大的相似性,均呈线性串珠状展布;为分辨识别隐伏异常源,圈定与各自有关联的找矿靶区、间接发现这两种类型的金矿床,归纳总结了从五个方面对隐伏的条带状含铁建造和辉绿岩所引起的磁异常特征进行识别:(1)岩石半出露特征,(2)区域地层(或构造)分布特征,(3)磁异常强度的高低,(4)2.5维反演计算,(5)磁异常的排列关系;对磁异常特征进行解译判别,有效地指导了在隐伏绿岩带内圈定找矿靶区、进而间接发现与各自有关联的含铁建造型金矿和构造蚀变岩型金矿的作用.     

苏联巴列伊矿区石英-硫化物金矿床地球物理找矿模式

巴列伊矿区内分布最广的金矿类型是赋存在花岗闪长岩(间或在喷出岩)中含中等硫化物的中温脉型矿床.矿结和矿床的结构-构造形态取决于它们在区域构造中的位置.区域构造可通过卫片和航片判读进行划分.矿床地质构造特点是:围岩有广泛发育的交代蚀变,存在不同走向构造断裂,岩浆作用不均匀(有多种脉岩系列).上述特点的形成与中生代构造岩浆活动     

时间域航空电磁、航磁在五龙沟金矿整装勘查区中的应用研究

五龙沟金矿整装勘查区地处青藏高原中北部,开展地面电磁法难度大.以直升机为平台搭载VTEM系统,在整装勘查区东南缘开展了1∶1万时间域航空电磁、航磁测量,结果显示矿体航电异常明显,呈双峰、高时间常数和低阻特征;同时,矿体处于-60~-40 n T的负磁场梯度带上,周围可见局部升高5~10 n T的低幅磁异常.对该航电异常进行板状体反演,板状体埋深、规模和产状等参数与后续收集到的矿体产状等信息基本一致,表明该方法对已知构造蚀变岩型金矿反映好.结合地质、化探等资料,建立了构造蚀变岩金矿的找矿模型,圈定了靶区6片,其中1片经钻孔验证发现隐伏矿体.时间域航空电磁、航磁对构造蚀变岩型金矿找矿效果好,能克服地面电磁法受制于高海拔、复杂地形等恶劣条件影响的诸多困难,可用于勘查区已知矿区深边部和空白区的"攻深找盲"以及其他地区的金及多金属矿勘查工作.     

乌拉嘎金矿主要控矿因素与激电法找金效果

乌拉嘎金矿主要控矿因素是构造破碎带及裂隙带、斜长花岗斑岩体和老基底变质杂岩.其中构造破碎带是最主要控矿因素.矿化富集与含金玉髓状石英细脉或细网脉、黄铁一白铁矿脉和碳酸盐脉的发育程度密切相关.含金热液脉体的形态产状受构造破碎带和裂隙带控制，经过多期次叠加，往往造成矿化的进一步富集.矿体呈脉状、复脉状、扁豆状等形态.上述特点为该区电法找金提供了先决条件.金矿石是本区主要极化体.在乌拉嘎金矿区的张才沟靶区获得低阻高极化和高阻高极化异常，可望找到含金石英脉及含矿破碎带.     

江西葛源黄山铌（钽）矿床地质特征及成因分析

江西葛源黄山铌（钽）矿床位于灵山花岗岩体西侧的内外接触带上,受赣东北深大断裂及其次级北东向和北西西向断裂的控制。围岩蚀变主要为角岩化、矽卡岩化和黑鳞、铁锂云母岩化等。总体矿化特征,近岩体富铌,远岩体而富钽。     

Evidence from pseudomorphous β-quartz phenocryst for decompression of rock-forming and ore-forming processes in Shapinggou porphyry Mo deposit

The Shapinggou porphyry molybdenum(Mo) deposit, located in Jinzhai County, Anhui Province, China, is the largest in the Qinling-Dabie Mo Metallogenic Belt. The intrusive rocks in the Shapinggou Mo ore district formed in the Yanshanian can be divided into two stages based on zircon U-Pb dating and geochemical features. This study focuses on the late stage intrusions(quartz syenite and granite porphyry), which are closely genetically related to molybdenum mineralization. Petrographic observations identified two quartz polymorphs in the quartz syenite and granite porphyry, which were derived from the same magmatic sources and similar evolutionary processes. The quartzes were identified as a xenomorphic β-quartz within quartz syenite, while the quartz phenocrysts within the granite porphyry were pseudomorphous b-quartz, characterized by a hexagonal bipyramid crystallography. The pseudomorphous b-quartz phenocrysts within the granite porphyry were altered from b-quartz through phase transformation. These crystals retained b-quartz pseudomorph. Combined with titanium-inzircon thermometry, quartz phase diagrams, and granitic Q-Ab-Or-H_2O phase diagrams, it is suggested that the quartz syenite and granite porphyry were formed under similar magmatic origins, including similar depths and magmatic crystallization temperatures. However, the β-quartz within quartz syenite indicated that the crystallization pressure was greater than 0.7 GPa, while the original b-quartz within the granite porphyry was formed under pressures between 0.4 and 0.7 GPa. The groundmass of the granite porphyry which formed after the phenocryst indicated a crystallizing pressure below 0.05 GPa. This indicates that the granite porphyry was formed under repetitive and rapid decompression. The decompression was significant as it caused the exsolution of the ore-forming fluids, and boiling and material precipitation during the magmatic-fluid process. The volumetric difference during the phase transformation from b-quartz to β-quartz caused extensive fracturing on the granite porphyry body and the wall rocks. As the main ore-transmitting and ore-depositing structures, these fractures benefit the hydrothermal alteration and stockwork-disseminated mineralization of the porphyry deposit. It is considered that the pseudomorphous β-quartz phenocrysts of the porphyritic body are metallogenic indicators within the porphyry deposits. The pseudomorphous β-quartzes therefore provide evidence for the formation of the porphyry deposit within a decompression tectonic setting.     

Gold mineralization age of the Anjiayingzi gold deposit in Chifeng County,Inner Mongolia and implications for Mesozoic metallogenic explosion in North China

The Anjiayingzi gold deposit in Chifeng County, Inner Mongolia is located in the central part of the gold mineralization belt of the northern margin of the North China Craton (NCC), and is adjacent to the Paleozoic Inner Mongolia-Da Hinggan Mountains orogenic belt in the north. The Chifeng-Kaiyuan fault, which separates the NCC from this orogenic belt, is considered to be a regional ore-controlling structure. The Anjiayingzi gold deposit is a mediate-size quartz lode-gold deposit and is hosted by the Anjiayingzi quartz monzonite that was emplaced into the basement composed of early Precambrian gneisses. Rhyolitic and porphyritic dikes are generally associated with the gold mineralization. Zircon U-Pb analyses suggest that the Anjiayingzi granite was emplaced from 132 Ma to 138 Ma, while the rhyolitic dikes that occupy the same fracture system as the gold-bearing quartz veins and locally crosscut the gold lodes crystallized from 125 Ma to 127 Ma. These results constrain the mineralization age between 126     

Geochemical evidence for contribution of ore-forming materials from peraluminous granite basement —— Taking Fucheng pluton and No. 6722 uranium deposit in southern Jiangxi Province as examples

Source of ore-forming material is always one of the fundamental subjects in the study of mineral deposits. Recently, in order to probe deep sources of ore-forming materials, many interna-tional and Chinese investigators have paid much attention to the rel…     

岩浆对热泉型金矿化作用的热影响

岩浆的余热为热泉型金矿化作用浅成热液循环系统提供热源,促使热液迁移循环并改变热液性质和状态。使近岩浆热液达到超临界的高温,为热泉型金矿化作用提供热力学条件。本文根据腾冲－梁河地热系统的特点及岩浆活动的一般特征,模拟计算了岩浆余热在热泉型金矿化作用中的演化过程。     

鄂东南富水金矿带成矿地质特征及找矿标志

本文介绍了富水金矿带区域地质、金矿带地层、构造及典型矿床地质特征,矿床属中、低温渗滤热卤水型金矿-卡林型金矿,金为微细粒浸染型金,肉眼甚至一般光学显微镜中均不可见。作者根据本区金矿体的分布及赋存情况,结合区域成矿地质条件和化探异常分布,对金矿带找矿标志进行了总结。     

Geochemical characteristics and origin of the Neoproterozoic high-K calc-alkaline granitoids in the northern part of Mandara hills,northeastern Nigeria

The high-K calc-alkaline granitoids in the northern part of the Mandara Hills are part of the wellexposed post-collisional plutons in northeastern Nigeria.The calc-alkaline rock association consists of quartz monzodiorite,hornblende biotite granite,biotite granites and aplite which intruded the older basement consisting mainly of low-lying migmatitic gneisses and amphibolites during the Neoproterozoic Pan-African Orogeny.Petrological and geochemical studies have revealed the presence of hornblende,iron oxide,and metaluminous to slightly peraluminous characteristics in the granitoids which is typical of I-type granite.The granitoids are also depleted in some high field strength elements(e.g.Nb and Ta) as well as Ti.Plots of Mg#versus SiO_2 indicate that the granite was derived from partial melting of crustal sources.Lithospheric delamination at the waning stage of the PanAfrican Orogeny possibly triggered upwelling of hot mafic magma from the mantle which underplated the lower crust.This,in turn,caused partial melting and magma generation at the lower to middle-crustal level.However,the peculiar geochemical characteristics of the quartz monzodiorite especially the enrichment in compatible elements such as MgO,Cr,and Ni,as well as LILE element(e.g.K,Ce,Cs,Ba,and Sr),signify that the rock formed from an enriched upper mantle source.The emplacement of high-K granites in the Madara Hill,therefore,marked an important episode of crustal reworking during the Neoproterozoic.However,further isotopic work is needed to confirm this model.     

地球化学勘查综合定量评价在赣东南大墩矿区的应用

赣东南大墩地区铜金多金属矿化主要产于晚三叠世黑云正长花岗岩与南华系接触带附近,受南华系浅变质岩地层岩性及断裂破碎带控制明显。本文以该区1：5万矿产远景调查项目大墩靶区成功找矿为例,基于M APG IS软件系统,对勘查区进行了化探数据处理、化探异常剖析、元素聚类分析、元素定量统计分析、剥蚀程度定量评价等综合定量评价。工作成果表明,勘查区显示铜金为主要矿种、银铅锌为伴生矿种的中低温热液型矿床特征,矿化类型主要为石英脉型,矿床可达小型-中型规模。在风化剥蚀面显露出金铜等近矿地球化学原生晕指示元素。根据地球化学勘查综合定量指标分析,认定大墩地区为面积约15 km2具有中型铜金多金属矿产地勘查前景的找矿靶区。应用以上成果,该区已取得明显找矿效果。     

Geochemical evidence for contribution of ore-forming materials from peraluminous granite basement

Using the induced fission-track method, mobile uranium leaching and lead isotope analysis, this work obtianed geochemical features of the peraluminous Fucheng granite basement and the host rock (shoshonite) of the No. 6722 uranium deposit in southern Jiangxi Province, (i) Uranium contents of the leucocratic rock-forming minerals (0.18 μg/g for quartz, 0.36 μg/g for feldspar) are lower than the uranium content of the whole rock (4.6 μg/g). Biotite and some accessory mineral inclusions (zircon, monazite and uraninite) are the main uranium carriers of the Fucheng granite pluton. The fissure uranium in altered minerals (hydromica and chlorite) increased evidently, (ii) Leachable rate of mobile uranium in the biotite granite is 10.4⨴; while that in the altered granite increased to 31· · (iii) Caculation based on lead isotopes shows that during alteration the Fucheng granite lost uranium (AU = −37%–−65· · ), whereas the Caotaobei shoshonite gained uranium (AU = +37· ·–+58 · ·). These features suggest that the ore-forming material of the No. 6722 uranium deposit was mainly derived from the altered peraluminous granite basement of Fucheng pluton.