【作者】 谭满堂；

【导师】 姚书振；

【作者基本信息】 中国地质大学 ， 矿物学、岩石学、矿床学， 2013， 博士

【摘要】 小秦岭地区横跨陕西和河南两省,地质构造上是秦岭造山带的重要组成部分。秦岭造山带自早前寒武纪以来经历了多阶段、多体制的构造演化过程,印支期以来,扬子板块、南秦岭地块及华北板块的对接碰撞使得秦岭全面造山,营造了多地体拼贴的大地构造格局；尤其是燕山期又受到滨太平洋构造域的叠加影响,使区内经历了多个构造岩浆旋回,壳-幔物质交换、地表与深部地质作用强烈,形成了丰富多样的成矿系统和成矿系列。其中金成矿作用与印支期末—燕山期秦岭陆内造山运动中的构造-岩浆-热液流体作用有密切关系,小秦岭金矿田即是其中最重要的典型成矿系列之一。小秦岭地区北以太要断裂与渭河盆地相邻,南部以小河断裂与熊耳构造带相接,是秦岭造山带的北缘东段部分,呈东西向区域性褶皱隆起,北侧、东南侧均为第四纪沉积盆地,南侧为元古宙地层分布区。区内地层主要为太古界—古元古界太华群中深变质的花岗—绿岩岩系,是区内金矿的赋矿围岩；次为新元古界管道口群碎屑岩-海滨相碳酸盐岩建造。小秦岭地区构造复杂,褶皱、断裂极其发育,总体格局被归结为“一核、二界、三拆离”的变质杂核岩构造,形态上为一近东西向展布的复式背形构造,中部为老鸦岔主背形,南北两侧分别为五里村背形、七树坪向形和庙沟向形、上杨砦背形。区内发育数百条韧-脆性断裂,以近东西向为主,北西向、北东向和南北向次之。其中近东西向断裂是最主要的控矿断裂,以压扭性质为主,沿走向和倾向均呈波状起伏变化；其次为北东向的控矿断裂；主要的控矿断裂均是在早期韧性剪切带的基础上叠加发育而成的。区内火山-岩浆活动频繁,岩浆岩分布广泛,面积较大的有元古代花岗岩和中生代燕山期花岗岩,以燕山期花岗岩浆活动最为强烈,且与金矿的形成密切相关。小秦岭金矿田内含金石英脉及金矿床众多,具丛聚性、密集成带、近于平行排列等间距分布的特征,具体可分为西矿带、南矿带、中矿带、北矿带四个矿带：主要的成矿类型为石英脉型,伴有少量构造蚀变岩型。河南省灵宝市东闯金矿、杨砦峪金矿和陕西省潼关县东桐峪金矿是最典型的三个石英脉型矿床,均分布在老鸦岔主背斜轴部附近,赋矿围岩以太华群变质岩为主,含金石英脉主要分布在褶皱轴部附近的韧性剪切带和脆性断裂之中。东闯金矿规最大的矿脉为507脉,其次还有508、505、504等脉；杨砦峪金矿主要为S60脉；东桐峪金矿主要矿脉则有东西向的Q8、Q10以及北东向的Q12脉等。矿脉均具有分支复合、尖灭再现或侧现特征,矿体在脉体中则具有近等距多分段富集特征,品位与厚度具有较强的正相关性。矿石矿物主要有自然金、银金矿、石英和黄铁矿等,次有方铅矿、黄铜矿、闪锌矿等。主要结构有粒状结构、充填结构等,主要构造有条带状、网脉状、浸染状等。围岩蚀变以黄铁绢英岩化与成矿关系最为密切。主成矿期内,金矿化可以划分为四个成矿阶段：Ⅰ黄铁矿-石英阶段,以发育宽大的乳白色石英脉为特征,矿化弱；Ⅱ石英-黄铁矿阶段,以发育细脉状和条带状黄铁矿脉为特征,矿化强；Ⅲ多金属硫化物阶段,以同时发育团块状黄铁矿、方铅矿、闪锌矿和黄铜矿等为特征,矿化强；Ⅳ石英-碳酸盐阶段,矿化弱。小秦岭金矿受构造控制作用显著,区域网状复合构造格局是成矿基础,复式褶皱及断裂密集带控制金矿带分布,断裂活动控制矿体形态以及多阶段矿化富集。依据构造活动与金矿成矿演化之间的关系,可以分为成矿前、成矿期及成矿后构造活动。成矿前构造：随着秦岭造山运动的陆陆碰撞,小秦岭地区在印支期南北向挤压应力作用下形成了近东西向褶皱构造、韧性剪切带和在其基础上发展而成的脆性断裂带。韧性剪切带演变为脆性断裂,主要走向为北东向、近南北向和北西向,少数为近东西向或北西西向,大多被基性岩脉充填。成矿期：Ⅰ Ⅱ阶段时矿田区域内处于以近南北向挤压构造应力的作用下。Ⅰ阶段近东西向南倾断裂发生逆冲左行活动,走向上近东西向方位段以及剖面上缓倾部位形成主要的引张空间,充填了宽厚的乳白色石英脉,但矿化很弱。与其配套产生一组NE-NNE和NNW-SN向陡倾的共轭断裂组合,前者发生左行扭动,后者产生右行扭动。Ⅱ阶段断裂活动是Ⅰ阶段的继承和发展,主要断裂活动基本相似。但此阶段矿化强烈,形成含金黄铁矿-石英脉。Ⅲ阶段时区域构造应力转为伸展,主要的东西向南倾控矿断裂以右行扭动为主,使早期矿化(脉)体破碎,沿裂隙充填大量多金属硫化物,造成矿化叠加。Ⅳ阶段构造活动减弱,断裂活动仍以张裂为主,矿化弱。成矿后：构造活动减弱,主要发育微型的正断层和少量逆断层,错断矿(脉)体,对成矿影响不大。围岩和矿脉定向构造样品的分析可知：成矿前及早阶段的区域构造应力以南北向挤压为主,且具有压扭性质;成矿期Ⅰ Ⅱ阶段的应力场以NNE-SSW挤压为主,Ⅲ阶段则转为张性构造应力。小秦岭金矿成矿始于秦岭碰撞造山后期的构造体制转换时期,大规模成矿于燕山中晚期的伸展阶段。印支期及以前,秦岭造山使得小秦岭地区强烈褶皱隆起,形成复式褶皱和韧性剪切带为主的东西向构造体系。印支期末-燕山早期,秦岭碰撞造山开始由挤压逐渐向伸展转换,早阶段构造应力仍以挤压为主,发生同造山拆离伸展,形成变质核杂岩雏形,脆性断裂逐渐发育,形成早阶段矿化。燕山中晚期,受太平洋板块向欧亚板块俯冲影响,北东向构造体系逐渐叠加改造东西向构造体系,变质核杂岩成型,发生垮塌伸展,花岗岩基侵入,脆性断裂更加发育,成就了大规模的金矿化。对东闯金矿507脉、杨砦峪金矿S60脉以及东桐峪金矿Q8和Q12号脉进行了矿化趋势面分析,结果表明：矿脉趋势分析图解上显示出矿体厚度与金铅品位的总体相似、又有细微差异的特点,反映了“Ⅰ阶段成脉、Ⅱ阶段金矿化、Ⅲ阶段金铅叠加”的矿化规律：东西走向南倾矿脉总体呈现向南西深部侧伏的特征,指示控矿断裂活动由南西向北东斜上左行逆冲的活动特征；由矿体侧伏与断裂产状波状起伏联合控制的近平行等间距展布的两组结构线的交汇部位是矿化富集地段：沿着矿脉侧伏方向,依据两组线性结构的延伸交汇并兼顾厚度与品位高值中心的偏差是深部成矿预测的重点方向。利用计算机软件对构造应力场的有限元法数值模拟,验证了区域构造应力南北向挤压及剪切扭动对矿脉形成的控制作用,尤其是对东闯金矿3号勘探线剖面的构造应力的模拟结果,一方面表明断裂产状陡缓变化部位也是应力尤其是剪应力较强区域,有利于岩石破裂形成容矿空间,也是成矿流体压力变化较大位置,有利于成矿；另一方面通过先挤压后拉伸的应力模拟,所得到的图解能很好地与已知矿脉矿化富集特征吻合,验证了区域构造应力由挤压向伸展转化机制对矿化富集的控制作用。通过本文研究,从宏观到微观对小秦岭地区石英脉型金矿构造控矿规律有了较为系统的认识,揭示了成矿过程中构造应力转换对成矿的控制,探讨了主要构造活动与金成矿演化的关系,总结了矿化富集规律,指出了深部预测方向,从理论到实践上对区内石英脉型金矿的成矿规律研究和深部找矿预测均具有较好的实际意义和参考价值。更多还原

【Abstract】 Xiaoqinling area was located on the border between Shanxi and Henan. Its tectonic position were important part of Qinling orogenic belt. Qinling orogenic belt experienced multi-stage and multi-system tectonic evolution from early Precambrian. Since Indosinian period, Qinling orogeny was formed by the collision among Yangtze Plate, southern Qinling massif and northern China plate and caused a mulit-terrain tiled geotectonic framework. Especially in the Yanshannian, it was superposed evidently by the effect of the peri-Pacific tectonic domain. During the continental collision and later tectonic superposition, it had several tectonic-metallogenetic cycles and crust-mantle exchange and geological processes in the surface or deep were strongly, then it formed abundant and various metallogenic systems and series. The gold mineralization was closely related to the structure-magma-hydrothermal fluid effects in the orogenic movement from the end of Indosinian period to Yanshan period. Xiaoqingling gold area is an important one of these metallogenic series.Xiaoqingling area was the eastern part of the northern margin of Qinling orogenic belt and upliftied as a regional EW fold. It was adjacented to a Quaternary sedimentary basin named as Weihe basin at the north side with a fault boundary named as Taiyao fault, adjacented to another Quaternary sedimentary basin at the southeast side, and connected Xiong’er tectnic belt with a fault boundary named as Xiaohe fault.The regional stratum were mainly a mesometamorphic granitic-greenstone series of archeozoic and paleoproterzoic Taihua group which was the gold ore host rock and secondarily a clastic rock-littoral carbonate formations of neo-proterozoic Guandaokou group.Xiaoqinling area had complex fold and fault structures and its general pattern was summarized as a metamorphic core complex which had one core, two boundaries and three detachment. Its shape was a EW complex anticline whose centarl was Laoyacha main anticline and bilateral were Wulicun anticline, Qishuping syncline, Miaogou syncline and Shangyangzhai anticline separately. There were hundreds ductile-brittle faults whose tendency were mainly nearly EW and secondarily NW, NE and NS. The most major ore-controlling fault was the nearly EW compresso-shearing fault which had undulatory shape along their strikes and dips and the secondary ore-controlling fault was the NE fault. These ore-controlling faults developed multiply on the base of early ductile shear belts.The regional volcanic-magmatic activity was frequently and magmatic rock was widely distributed, such as the lager-area proterozoic and mesozoic yanshannian magmatic rocks.There were plenty of gold-bearing quartz veins and gold deposit in Xiaoqinling gold ore field which were characterized by concentration, zonation and nearly parallel alignment and were divided into the west ore belt, the south ore belt, the middle ore belt and the north ore belt.The major gold metallogenic type was quartz vein type and a few was structural altered rock type.Dongchuang gold deposit, Yangzhaiyu gold deposit in Lingbao county, Henan province and Dongtongyu gold deposit in Tongguan county, Shanxi province were three most typical quartz vein type gold deposits which distributed near the axis of Laoyacha main anticline. The ore-bearing rock was mainly metamorphic rock of Taihua group and gold-bearing quartz veins chiefly distributed in the ductile shear belts or brittle fractures near the axis of the fold.The largest ore vein of Dongchuang gold deposit is vein No.507whose strike is nearly EW. Beside it, there are other EW larger veins such as No.508, No.505and No.504. The main ore vein of Yangzhaiyu gold deposit is EW vein No.S6O. The typical veins of Dongtongyu gold deposit are vein No.Q8and vein No.Q10whose strikes are EW and vein No.Q12whose strike is NE.All these veins had complex-thin,thinning-out and recurrence shape. Orebodies distributed nearly isometrically in the veins and mineralized in several stages. The Au grade was positively correlated with thickness. The main ore minerals were native gold, electrum, quartz, pyrite, galenite, chalcopyrite and sphalerite or so. The major texture were granular and filling texture. The typical structures were banding, net-work and impregnated structure. Pyritephyllic alteration had a close relationship with mineralization.In the major mineralize period, gold mineralization could be divided into four stages. The first one was pyrite-quartz stage which grew ivory white thick quartz vein and mineralization weakly. The second one was quartz-pyrite stage which grew banding or thin vein pyrite veins strongly. The third one polymetallic sulfide stage which grew massive pyrite, galenite, chalcopyrite and sphalerite and mineralization strongly. The last one was quartz-carbonate stage which mineralized very weakly.The quartz vein type gold deposits in Xiaoqinling were controlled strongly by geological structure. Regional reticulate complex structure was mineralization basic. Complex fold and fault concentrated zones controlled the distribution of gold ore zone. Fault activity controlled orebody shape and multistage mineralization.According to the relationship with gold mineralization evolution, the tectonic activity could be divided into pre-mineralized, mineralized and later mineralized tectonic activities.Because of the continental collision before the mineralization, the EW complex anticline, ductile shear zones and brittle fractures which were developed from ductile shear zones formed in Xiaoqinling area in NS bearing stress in Indosinian. In the first two stages of main mineralization period, the area was also in the near NS extrusion stress. In the first stage, the faults which struck EW and dipped to south thrust from SW to NE obliquely with leftward contortion. The ivory white thick quartz veins filled at EW strike or gentle inclined parts, but the mineralization was weakly. Besides, NE-NNE and NNW-SN conjugate fractures developed. The former had contorted leftward and the later contorted rightward. In the second stage, fault activity inherited and developed from the first stage and grew gold bearing pyrite-quartz veins strongly. In the third stage, regional tectonic stress converted from extrusion to extension. The EW faults had rightward contortion. The early orebodies or veins crushed and were filled with plenty of polymetallic sulfide. In the last stage, fault extended very weakly.After mineralization, tectonic activity weakened continuely. Only small normal faults and reverse faults grew and leaped orebodies or veins slightly.The research of directional structure samples showed the stress conversion mechanism during the mineralized process. Regional tectonic stress was N-S extrusion with left contortion. It was NNE-SSW extrusion in the first and second stages but extension in the third stage.Xiaoqinling gold mineralization started in the tectonic mechanism converting period of Qinling collisional orogeny then mineralized greatly in the extension stage of Yanshannian. Before and in the Indosinian, Qinling orogeny caused Xiaoqinling area folding and upwarping and formed EW tectonic system including a complex fold and many ductile shear zones. From late Indosinian to early Yanshannian, Qinling collisional orogeny started converting from extrusion to extension. The early tectonic stress was also extrusion. The rudiment of Xiaoqinling metamorphic core complexes formed and produced synorogenic detachment-extension. Brittle fractures grew gradually and produced early mineralization. In the middle-late Yanshannian, affected by the subduction of Pacific plate beneath Eurasian plate, the NE tectonic system superimposed and reformed the EW tectonic system gradually. Xiaoqinling metamorphic core complexes formed and produced collapse extension. Granitic batholiths invaded and brittle fractures grew greatly. These caused large-scale mineralization.By trend surface analysis of ore body thickness, Au and Pb grades on vein No.507in Dongchuang gold deposit, vein No.S60in Yangzhaiyu gold deposit, veins No.Q8and No. Q12in Dongtongyu gold deposit, the graphics revealed the characteristics of fault ore-controlling and the mineralized enrichment regular of these deposits well. Those graphics showed general morphological similarities and microscopic difference among orebody thickness, Au grade and Pb grade. These reflected that vines formed primarily in the first stage, gold mineralized strongly in the second stage and Au-Pb superposed mineralization in the third stage. The main mineral veins with EW strike pitched to southwest and it showed that the ore-controlling faults thrust from SW to NE obliquely with leftward contortion. Controlled by orebody plunging direction and wavelike fault occurrence jointly, the intersection parts of two structure lines which distributed proximal parallel and equidistantly were mineralization enrichment areas. So, the major deep prediction direction should include the lateral trending direction of orebody, the intersection parts of two structure lines and the center aberrations between orebody thickness and grade.By the computer numerical simulation of tectonic stress on the base of finite elem ent method, this paper verified the ore-controlling effect of the regional N-S extrusion stress and leftward shearing contortion.Using the software of ABAQUS, this paper simulated the tectonic stress on No.3prospecting line section in Dongchuang gold deposit. One hand, the position where the fault occurrence changed from precipitous to placid was the favorable mineralized place where the shear stress concentrated strongly and broke the rocks easily. On the other hand, through the stress simulation from early extrusion to extension, the result graphics could be in accordance with the mineralized enrichment characteristics of known ore veins. It would verify the ore-controlling effect of the tectonic stress conversional mechanism from early extrusion to extension.This paper studied the structural ore-controlling rules of quartz gold deposit in the Xiaoqinling area systematically from macro to micro. It analyzed ore-controlling effect by the tectonic stress conversion in the mineralization process, discussed the relationship between the main tectonic activity and the gold mineralization evolution, summarized mineralized enrichment regular and pointed out the major deep prediction direction of several typical ore veins. All these results would be helpful for mineralization regular research and deep prediction in Xiaoqinling gold ore field.更多还原