金矿勘查中的地面高精度磁法测量——以黑龙江乌拉嘎金矿外围十三公里勘查区为例

地面高精度磁测是可以间接找金的.它能够可靠地反映控矿地质体的磁性变化,了解隐伏的控矿岩体、构造和含矿蚀变破碎带的分布.为了提高黑龙江乌拉嘎金矿外围十三公里区的金矿勘查效果,利用地面高精度磁测在该区进行了扫面测量.通过该项研究表明了含矿构造破碎带的存在.在矿化带上方表现为正值磁测异常区与负值磁测异常区的接触带,尤其是梯度较大部位.矿体一般位于负值一侧的低缓正异常处.通过对优选靶区的工程查证,探槽、浅井双双见矿,共获得黄金资源量1.5吨.由此证明了应用该方法找金的有效性.     

综合地球物理方法在某金多金属矿区找矿中的应用

某金多金属矿区地表矿化痕迹较多,矿化体和围岩物性差异明显,为了准确查明区内矿体的空间分布以及控矿构造,在该区实施了对称四极装置的激电扫面和EH4连续电导率测深工作.激电测量获得了总体呈NE走向、与地表矿带对应的中高视电阻率(?s)及中高视极化率(?s)矿化异常带.异常带西窄东宽,矿化集中在测区327°向测线800～1350 m处;在与已知矿体对应的?s-2高极化率激电异常开展的EH4测深工作结果进一步确定了深部成矿潜力:含矿构造延深可达500 m,具有低阻异常特征,倾角近直立.激电扫面和EH4测深相结合的综合物探方法在该区达到了查明矿体分布规律、控矿构造的目的,是有效的多金属矿找矿方法之一.     

江西省于都县银坑贵多金属矿田矿化特征,成矿控制及找矿方向

于都银坑贵金属矿田有破岩蚀变型,层间破碎带型,岩体接触带型、硫锰矿型、铁锰帽型、黑土我砾型等六种矿化类型。主要控矿因素为地层、岩柱、岩浆岩、构造和次火山岩体接触带构造四种。     

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。     

有利岩性对微细浸染型金矿化的控制作用 ——以南秦岭金龙山金矿带为例

金龙山金矿带是我国南秦岭沉积岩地区新发现的金矿带,产于南秦岭晚古生代镇旬盆地上泥盆统-下石炭统细碎屑岩-碳酸盐建造中.通过地层、沉积环境、成矿有关微量元素、矿石化学成分及显微组构研究指出赋矿有利岩性为泥质钙质粉砂岩、泥质粉砂质灰岩等,典型的浸染状矿化产于以粉砂质为主(SiO2多变化于38%～73%),含一定钙质(CaO多在10%～25%之间)的岩石中,即以钙质粉砂岩为主要的赋矿岩石类型;主要赋矿地层南羊山组生物成因黄铁矿不富集金.微细浸染型金矿化受与断裂连通的有利岩性(可渗透性层位)控制;是"岩性控矿”,而非地层时代控矿.主要赋矿地层南羊山组是"赋矿之所”,而非"生矿之源”.以钙质粉砂岩为代表的沉积岩石控制微细浸染型金矿化具有普遍意义.断裂与有利岩性一起控制了浸染状矿化.     

江西省会昌县淘锡坝大型锡矿床构造控矿机制探讨

淘锡坝锡矿床是近年探明储量达大型的锡矿床,是一种新的锡矿类型-隐爆层间裂隙带型。文章介绍了该矿床的地质特征和矿化特征,对矿区的构造进行了重点解剖,对构造控矿机理进行了探讨,提出火山机构及北东向断裂是矿区的控岩构造,控制了白垩纪成矿花岗岩体的侵入就位。而火山岩中大范围的隐爆层间裂隙带是良好的容矿构造,矿体赋存其中呈似层状,局部膨大形成厚达数十米的＂锡矿包＂。通过研究构造与矿化富集的内在联系,总结了该矿床的成矿规律。     

EH4在危机矿山隐伏金矿体定位预测中的应用研究

EH4连续电导率成像仪是快速高效的第四代数字化大地电磁探测仪器,基本配置(10Hz～100kHz)能测量地表向下1000m深度范围内地质体的连续视电导率值,我们对25个不同类型金属矿床进行了隐伏矿定位预测,取得了显著的效果.2D模式图能清晰地反映不同电性体的精细电阻率结构,经钻孔验证后显示:(1)火山晚期热液型金矿床,很好地反映了火山机构控矿的漏斗状形态,体现了矿体的垂向延深大于水平延长的成矿规律,矿化异常的电阻率较低(1～150Ω·m);(2)剪切带型金矿床,明显区分了矿化蚀变构造带和围岩,确认矿化异常在围岩中呈脉状分布,电阻率小于260Ω·m;(3)隐爆角砾岩型金矿床,清晰地反映了隐爆角砾岩体控矿所形成的对称矿(化)体,区分了隐爆角砾岩体和矿化蚀变带,矿化异常的电阻率较高(1000～2000Ω·m).     

新疆阿尔泰金矿断裂构造控矿规律研究

新疆阿尔泰地区金矿床,矿化点分布广泛,前人已该区金矿类型等方面做了多工作,但从断裂构造角度研究金矿床的成矿规律尚少。笔者从该区金矿床与断裂构造的空间关系分析了区内断裂构造及韧性剪切带控矿规律,指出区内金矿床严格受断裂构造及韧带切带控制,而且不同的构造分别控制着矿带、矿田、矿床直到矿体的分布及其形态和产状。     

时间域激电测深在坦桑尼亚金矿床勘查中的应用例析

铁建造(BIF)型金矿和构造蚀变岩型金矿是坦桑尼亚绿岩带中主要金矿床类型,应用时间域激电测深获得了这两种类型金矿床内、由探测目标体和目的物引起的良好异常,了解了它们在地下半空间内的电性分布特征;依据激电测深显示的"低阻高极化"断面异常对含矿标志层(条带状含铁建造)、含矿构造(蚀变带)和金矿(化)体进行空间定位,为钻探工程布置、进而发现隐伏-半隐伏金矿床提供了充分依据.以坦桑尼亚绿岩带内近几年发现的典型金矿床为实例,分析时间域激电测深在这两种类型金矿床中的应用效果,以期为成矿地质条件类似地区通过激电测深手段寻找金矿产提供借鉴.     

黑龙江省白石砬子地区音频大地电磁圈定金矿(化)

白石砬子地区位于黑龙江省黑河市东北部,属于森林沼泽浅覆盖区.近年来,沈阳地质矿产研究所在白石砬子地区发现大明山蚀变型金矿点.在该矿点已进行地质填图,土壤和水系沉积物地球化学调查,少量槽探工程和几个浅钻.该矿点已进行了几条高密度电法剖面,瞬变电磁剖面和可控源音频大地电磁剖面工作.这些地质、矿产、化探和物探工作并没有提供矿点深部结构.为了解矿化点深部结构和控矿信息,2015年在大明山金矿点布置3条音频大地电磁剖面.基于相位张量方法和阻抗旋转不变量分析,对AMT数据进行维数分析和走向判定.在经过阻抗张量旋转后,由于矿点地质复杂与地电维数特征,我们对TM模式,TE模式和TE+TM模式数据进行二维非线性共轭梯度反演.因为TM模式主要反映横切断面的地电结构,所以我们主要依赖TM模式反演电阻率模型.参考地质矿产和钻孔信息,对三条剖面电阻率模型进行地质推断.结果发现大明山矿化点下存在低阻剪切破碎带,该破碎带从北向南延伸到NN'剖面,推断为控矿构造.该低阻带边缘具有找矿潜力.总之,在白石砬子森林沼泽浅覆盖区,AMT可以更加可靠地探测1km以内的蚀变型金矿.     

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     

Geophysical exploration for interlayer slip breccia gold deposits: example from Pengjiakuang gold deposit, Shandong Province, China

Interlayer slipping breccia‐type gold deposit – a new type of gold deposit, defined recently in the northern margin of the Jiaolai Basin, Shandong Province, China – occurs in interlayer slip faults distributed along the basin margin. It has the features of large orebody thickness (ranging from 14 m to 46 m, with an average thickness of 30 m), shallow embedding (0–50 m thickness of cover), low tenor of gold ore (ranging from 3 g/t to 5 g/t), easy mining and ore dressing. This type of gold deposit has promising metallogenic forecasting and potential for economic exploitation. A ground gamma‐ray survey in the Pengjiakuang gold‐ore district indicates that the potassium/thorium ratio is closely related to the mineralization intensity, i.e. the larger the potassium/thorium ratio, the higher the mineralization. The gold mineralized alteration zone was defined by a potassium/thorium ratio of 0.35. A seismic survey confirms the location of the top and bottom boundaries and images various features within the Pengjiakuang gold mineralization belt. The gold‐bearing shovel slipped belt dips to the south at an angle of 50–55° at the surface and 15–20° at depth. The seismic profile is interpreted in terms of a structural band on the seismic section characterized by a three‐layered model. The upper layer is represented by weakly discontinuous reflections that represent the overlying conglomerates. A zone of stronger reflections representing the interlayer slip fault (gold‐bearing mineralized zone) is imaged within the middle of the section, while the strongest reflections are in the lower part of the section and represent metamorphic rocks at depth. At the same time, the seismic reflection survey confirms the existence of a granite body at depth, indicating that ore‐forming fluids may be related to the granite. A CSAMT survey showed that the gold‐bearing mineralized zone is a conductive layer and contains a low‐resistivity anomaly ranging from 2 Ωm to 200 Ωm.     

Conditions and processes leading to large-scale gold deposition in the Jiaodong province,eastern China

The gold deposits in the Jiaodong Peninsula constitute the largest gold mineralized province in China. The mineralization shows common characteristics in their tectonic setting, ore-forming fluid and metallogenic system. Sulfidation and fluid immiscibility are two important mechanisms controlling gold precipitation, both of which consume sulfur in the oreforming fluids. The escape of H_2S from the main ore-forming fluids and the decrease of total sulfur concentration not only lead to the efficient precipitation of gold, but also result in the crystallization of reducing minerals such as pyrrhotite and oxidizing minerals such as magnetite. Quartz solubility shows strong dependence on temperature, pressure, and CO_2 content. The dependence of quartz solubility on pressure is weak at low temperatures, and progressively stronger at higher temperatures.Similarly, the temperature dependence of quartz solubility is relatively low at low pressures, but becomes gradually stronger at high pressures. The results of solubility modeling can constrain the dissolution and reprecipitation behavior of quartz in the oreforming veins and the formation mechanism of different types of quartz veins. The multi-stage mineralization fluid activity resulted in the complex dissolution structure of quartz in the Jiaodong gold veins. Pyrite in the main metallogenic period in the Jiaodong gold deposits shows complex microstructure characteristics at single crystal scale. The trace elements(mainly the coupling of As-and Au-rich belt) and sulfur isotope composition also display a certain regularity. The As-rich fluids might have formed by the initial pulse of ore-forming fluids through As-rich metasedimentary strata, while the As-Au oscillation zone at the margin of pyrite grains is related to the pressure fluctuation caused by fault activity and the local phase separation of fluids. There is a temporal and spatial evolution of gold fineness in the Jiaodong gold deposits. Water/rock reaction(sulfidation) was the main ore-forming mechanism of early gold mineralization, forming relatively high fineness gold, while significant pressure drop in the shallow part accompanied by fluid phase separation promoted the late gold mineralization, forming low fineness gold. Under cratonic destruction setting, dehydration of the amphibolite and granulite facies metamorphic lower-crust resulted in the formation of Au-CO_2-rich ore-forming fluids, which rose along the deep fault and secondary structure, and formed the largescale fault-controlled gold deposits in Jiaodong.     

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。     

Metallogenesis of the Ertix gold belt, Xinjiang and its relationship to Central Asia-type orogenesis

The Ertix gold belt is located on the boundary of the Kalatongke arc and the Kelan back-arc basin of D-C1. Most scholars used to interpret the formation and distribution of the gold deposits in the Ertix tectonic belt in terms of the petrogenic and metallogenic models for active continental margins. However, enormous data of isotopic dating and geologic research show that the mineralization was obviously later than the oceanic subduction, whereas exactly simultaneous with the collisional orogenesis during C₂-P, especially at the transition stage from collisional compression to extension. Based on study of metallogenic time, tectonic background, ore geology, ore fluid nature, ore material source, etc., we reveal that all the gold deposits possess the character of orogenic deposits formed in collisional orogenic system, and that their ore-forming materials mainly have derived from the stratigraphic terranes south to individual deposits. Accordingly, the theoretical tectonic model for collisional metallogenesis and petrogenesis is employed to explain the formation of the Ertix gold belt and to determine the gold exploration directions.     

Geological and geochemical character and genesis of the Jinlongshan-Qiuling gold deposits in Qinling orogen: Metallogenic mechanism of the Qinling-pattern Carlin-type gold deposits

The Qinling Carlin-type gold deposit belt is the second largest Carlin-type gold ore concentrated area in the world and occurs in Mesozoic intracontinental collisional orogen, contrasting to the Carlin-type gold deposits in the Basin and Range province in Cenozoic active continental margin of West America. With ore-forming ages focussed at the range of 197.45–129.45 Ma, its metallogenic geodynamic background was the decompression-pyrogenation regime at the transition stage from collisional compression to extension, indicating that gold mineralization synchronized with the Mesozoic continental collision. Geochemical studies discover that ore fluids and materials mainly came from the Hercynian-Indosinian tectonic layer. Mesozoic intracontinental subduction of Hercynian-Indosinian association along the Shuanghe-Gongguan fault led to the formation of Jinlongshan-Qiuling gold deposits. Accordingly, the tectonic metallogenic model is established for Qinling-pattern Carlin-type gold deposits.     

Pb-Sr isotopic evidence for contribution of deep crustal fluid to the Hishikari epithermal gold deposit, southwestern Japan

The gold-bearing quartz-adularia veins of the world-class Hishikari mine in southwestern Japan occur in a geological regime where the rocks of the upper to middle crust are simple and their chemical and Sr-Nd-Pb isotopic compositions are well studied. Detailed comparison of Pb and Sr isotopic data of the Hishikari veins with those of all possible source materials demonstrates that metals in the veins were essentially derived from a mixture of magmatic fluid with a deep crustal fluid that originated near the boundary between the Shimanto middle crust and the underlying subcontinental crustal materials. We propose that the release of the deep crustal fluid was triggered by intrusion of the Shishimano rhyodacite magma related to timing of the mineralization. This fluid mixture carried metals to the brittle upper crust along fissures created by extensional stress forming the ore deposits. Although the deep crustal fluid has not been paid much attention, it may be distributed over a large scale in the deep crust from the continent to the arc system and play an important role in the genesis of magmatic-hydrothermal ore deposits and in the generation of flow-induced deep tremor.