【作者】 张健；

【导师】 杨兴科；

【作者基本信息】 长安大学 ， 构造地质学， 2018， 硕士

【摘要】 南秦岭石泉-旬阳金矿带,位于安康市石泉县、旬阳县北部,是秦岭重要的金矿带之一,从西向东分布有多个已经开采的金矿床,如羊坪湾金矿、黄龙金矿、鹿鸣金矿、长沟金矿、烂木沟金矿等,近年,在安康市汉滨区茨沟-早阳一带新发现一金矿床,是该矿带内金矿勘查工作的重大突破,然而其缺乏对控矿脆-韧性剪切带构造样式、蚀变岩相和金属矿物赋存状态等的研究,并且在该成矿带西段众多金矿区的研究中很少涉及显微构造的详细研究。本文依托于长安大学地调院“中国地质调查局整装勘查区基础地质调查与潜力评价工程项目“陕西石泉-旬阳金矿整装勘查区关键基础地质研究”与陕西省地质调查院“秦岭成矿带典型矿集区勘查成果集成与技术支撑研究”项目,以石泉-旬阳金矿整装勘查区已有的基础地质、矿产调查成果为基础,以茨沟-早阳一带金矿区地质矿产调研为重点研究对象,进行该区野外路线调查、探槽编录、剖面测量、钻孔岩心编录等,并进行室内岩石光片-薄片鉴定、相关样品测试分析等,借助韧性剪切带变形分析的宏观和微观构造研究手段,运用分形地质学、石英温度计、石英压力计等方法研究了区内脆-韧性剪切带变形特征,取得了一定的研究成果,得出以下相关研究认识:（1）针对茨沟-早阳一带研究区内,通过调研已经圈出受北西—南东向展布的脆-韧性剪切带控制、赋存于奥陶系洞河组第一岩性段(Odh^1-2)上部的强蚀变黑云母石英片岩中层状、似层状与片岩片理（S₂面理）产状一致的6条金矿体和3条金矿化体。经人工重砂测量,自然金粒径在1.36mm—0.03mm,大部分粒径为0.15mm-0.38mm,属粗粒-巨粒金。自然金形态多为不规则状、片状、树枝状等。矿石自然类型为浸染状强变形含黄铁矿黑云石英片岩型,矿物成分较为简单,矿石中主要贵金属矿物为自然金,矿石矿物主要为黄铁矿、白铁矿、赤铁矿、褐铁矿等,占矿物总量约5%左右,脉石矿物主要为石英、绢云母、黑云母、石榴子石、绿泥石、碳酸盐矿物等。（2）通过路线、剖面、钻探等调查手段,研究区内识别出两条沿北西向展布,倾向45-65°,倾角45-60°,长约2500m,宽10-30m的BDSZ₁、BDSZ₂脆-韧性剪切带。两条脆-韧性剪切带走向与茨沟-早阳断层F₂一致,剪切带中岩性主要为洞河组第一段第二层(Odh^1-2)深灰色黑云石英片岩。见S-C组构、糜棱岩化、石英晶内-晶间裂隙等强烈脆韧性变形构造,另可见石英透镜体、褶曲石英脉、膝折、层间揉皱等现象,发育褐铁矿化、硅化、绢云母化、碳酸盐化。该脆-韧性剪切带为中-高角度韧性逆冲推覆剪切带,部分地段叠加后期引张构造作用（显示为S-C组构之C面理）,显示上盘下降的构造行迹。脆-韧性剪切带内两处拉伸线理产状平均值分别为117°∠25°和122°∠26°,指示了斜向逆冲推覆构造活动。（3）脆-韧性剪切带内不同部位普遍发育不同程度的绢云母面理置换、显微揉皱、S-C组构、石英波状消光、石英变形纹、石英机械双晶、糜棱岩化、早期石英细脉揉皱、黑云母残斑破裂变形、石英颗粒边界迁移重结晶、石英静态恢复重结晶等脆-韧性变形,据矿物结晶先后顺序和构造发育次序,可将脆-韧性剪切带的构造活动以及后期脆性变形过程分为六个阶段:（1）低温高压条件下韧性剪切作用阶段;（2）高温高压阶段;（3）高温低压阶段;（4）强烈的低温高压韧性剪切阶段;（5）低温脆性变形阶段;（6）引张拉伸环境低温热液活动阶段。金矿成矿期对应（4）强烈的低温高压韧性剪切阶段。六个阶段的划分使脆-韧性剪切带的构造活动以及后期脆性变形过程更加细化,区别出有利于金元素富集的阶段和有利于金元素沉淀成矿的阶段,即能够细致了解金成矿过程。（4）在贯穿脆-韧性剪切带BDSZ₂且垂直其走向的TC1901探槽剖面上连续采集7个薄片样品,在光学显微镜下统计颗粒边界迁移重结晶石英颗粒的周长和面积值,使用P-A（周长-面积）分形模型计算7个样品的分维值分别为1.1512±0.049、1.1458±0.0506、1.151±0.0578、1.2572±0.1664、1.12±0.1016、1.1196±0.0464、1.0506±0.036,将分维值换算成温度显示其变质温度在590-780℃。在整个TC1901探槽剖面上石英重结晶颗粒分维值显示出明显的趋势,即由南西向北东,分维值逐渐减小,所表征的变质温度也越高。这说明在研究区脆-韧性剪切带内,石英发生颗粒边界迁移重结晶时,从南西到北东方向温度逐渐变高,且均达到低角闪岩相。采用石英重结晶颗粒粒径模拟计算古差应力的方法得出的7个平均古差应力值范围为:6.89 Mpa¹3.65 Mpa。（5）据地表宏观地质调查和光学显微镜下微观研究两个方面,对研究区内脆-韧性剪切带的研究,分析总结了成矿过程。强烈的韧性剪切在构造片岩中形成了局部扩容带,为成矿热液灌入提供了通道,岩石变形程度和金品位对比显示出岩石变形越强,金品位越高,绢云母含量越高,金属矿物含量越高。韧性剪切变形是多期次的,成矿热液的富集也是多期次的,只有这样才能形成高品位的矿石,同时也造成了脆-韧性剪切带内岩石及围岩中金含量普遍较高却不能都达到工业品位的现象。薄片中不透明矿物条带和光片中白铁矿条带分布的不均匀性,指示高应变带形成的强变形扩容带具有不均匀性,因此矿石的品位也具有不均匀性。（6）提出找矿预测建议。（1）BDSZ₁剪切带深部找矿,矿体在走向上和倾向上产状稳定,BDSZ₁剪切带内仅部分地段控制了矿体深部形态,并且脆-韧性剪切带延伸方向上利用探槽已经确定矿化带位置,因此推断这些矿化带的深部可能赋存矿体,圈出A类找矿预测区1个。（2）研究区南东段延伸的脆-韧性剪切带内找矿,研究区内脆-韧性剪切带只占整个茨沟-早阳预查区内脆-韧性剪切带的一部分,脆-韧性剪切带在研究区南东段沿145°方向一直延伸到预查区外,且已查明其内发育的构造样式和矿化蚀变与研究区相似,因此研究区南东方向脆-韧性剪切带延伸部位是下一步找矿预测的重点区域,圈出A类找矿预测区1个和B类找矿预测区2个。更多还原

【Abstract】 The Shiquan Xunyang gold belt in southern Qinling Mountains,located in the north of Shiquan County and Xunyang County,Ankang City,is one of the important gold fields in Qinling Mountains area.From west to East,there are several gold deposits that have been exploited,such as Yang Ping Wan gold deposit,Huanglong gold deposit,Lu Ming gold deposit,Chang Gou Gold deposit and Lan Mu Gou gold deposit.In recent years,the discovery of a new gold deposit in Han Bin District Cigou-Zaoyang Ankang city is a major breakthrough in the exploration of gold deposits in this field.However,it lacks the research on the structural style of the ductile shear zone,the alteration of rock facies and the occurrence of metal minerals,and in the study of many gold deposits in the western section of the metallogenic belt,the detailed study of microstructure is rarely involved.This paper is based on the project of"the key basic geological research in the Shaanxi Shiquan and Xunyang gold deposit exploration area"from"the key basic geological survey and potential evaluation project,China Bureau of the Geological Survey”,carry out by Chang’an University.Based on the geological and mineral investigation in the mining area,the field route survey and the large scale exploration trough are carried out.The characteristics of the structure and alteration of the mining area are summarized and analyzed.The following understanding is drawn:（1）6 gold orebodies and 3 gold mineralization bodies in the strong altered black mica schist in the upper part of the first lithologic section of the Ordovician Donghe formation(Odh^1-2)and controlled by the brittle-ductile shear zone have been trapped in the study area,And the natural gold particle size is 1.36mm-0.03mm,and most of the particle size is0.15mm-0.38mm.The forms of natural gold are mostly irregular,flaky,dendrite and so on.The natural mineral type of the ore is dipping and strong deformed pyrite-containing black mica quartz schist type.The mineral composition is simple.The main precious metal minerals in the ore are natural gold.The ore minerals are mainly pyrite,hematite,hematite and limonite,accounting for about 5%of the total minerals,and the gangue minerals are mainly quartz,sericite and biotite.Garnet,chlorite,carbonate minerals,etc.（2）In the study area,two BDSZ₁ and BDSZ₂ brittle ductile shear zones were identified along the NW direction,with a tendency of 45 degrees-65 degrees,a dip angle of 45-60degrees,a length of 2500m,and a width of 10-30m.The two ductile shear zones are consistent with the Cigou-Zaoyang fault F2,and the lithology in the shear zone is mainly the second layer(Odh^1-2)dark gray black mica quartz schist in the first section of the Donghe formation.Strong brittle ductile deformation structure,S-C fabric,mylonitization,quartz lens,fold quartz vein,knee fold and interlayer crumple are also seen,and browning,silicification,sericite and carbonation are developed.The ductile shear zone is a moderate angle ductile thrust nappe shear belt,and some parts are superimposed by late extensional tectonics,showing structural traces falling on the upper plate.There are two lines in the brittle ductile shear zone,with the average value of 117°∠25°和122°∠26°respectively.The formation of the foliation is concentrated at 50 degrees 55 degrees,indicating the oblique thrust nappe structure.（3）The different parts of the brittle ductile shear zone generally develop different degrees of Sericite replacement,micro crumple,S-C fabric,quartz wave extinction,quartz deformable pattern,quartz mechanical double crystal,mylonitization,early quartz vein crumple,black mica rupture and deformation,stone particle boundary migration recrystallization,quartz static The ductile deformation,such as recrystallization,indicates that the brittle ductile shear zone has undergone many stages of metamorphism,such as high temperature metamorphism,high temperature and low stress stage,low temperature mineralization,low temperature brittle deformation and so on,at the temperature of 500-600degrees（low amphibolite facies）.（4）The fractal dimensions of the quartz grain boundary migration recrystallization of 7samples on the TC1901 probe section are 1.1512±0.049、1.1458±0.0506、1.151±0.0578、1.2572±0.1664、1.12±0.1016、1.1196±0.0464、1.0506±0.036,respectively,indicating that the metamorphic condition reaches the phase of the low amphibolite-granulite.The temperature is at 590-780 degrees centigrade.The metamorphic temperature shows a partial inconsistency,but it is in the range of 600-800 degrees.Using the method of quartz recrystallization grain size simulation to calculate the paleo differential stress,the 7 average paleo differential stress values obtained are:6.89 Mpa¹3.65 Mpa.（5）According to macroscopic and microscopic two aspects,the research on the brittle ductile shear zone in the study area has analyzed and summarized the mineralization process.The strong ductile shear formed a partial dilatation zone in the tectonic schist,which provided a channel for ore forming hydrothermal irrigation.The stronger the rock deformation,the higher the gold grade.The ductile shear deformation is many times,and the enrichment of the metallogenic hydrothermal solution is also multiple.Only in this way can the high grade ore be formed,and the gold content in the ductile shear zone is generally high,but the industrial grade can not be reached.Owing to the heterogeneity of the strong deformation expansion zone formed by the high strain zone,the ore grade is also uneven.（6）Some suggestions for ore prospecting are put forward.（1）the deep prospecting for the ductile shear zone,the development of the metallic minerals in the ductile shear zone in the study area and the development characteristics of the quartz vein with the filling tendency of 330 degrees in the post tensional fissures after the main metallogenic period and the three stage metallogenic model proposed by Chen Bailin（1998）,that is,the quartz vein type gold deposits are superimposed on the early fine net veins and mylonite type gold deposits.Therefore,the deep part still has fine vein type and mylonite type gold deposit,and the gold element comes from the deep part of the ductile shear zone.（2）The scope of the ductile shear zone epitaxy is only a small part of the whole Cigou-Zaoyang precheck area,and the unexplored region in the brittle ductile shear zone is the key area for the next prospecting.更多还原