【作者】 聂江涛；

【导师】 魏刚锋；

【作者基本信息】 长安大学 ， 构造地质学， 2010， 博士

【摘要】 煎茶岭金镍矿田位于扬子板块和秦岭造山带的结合部位,大地构造位置独特。只有弹丸之地的煎茶岭矿田聚集着金矿、镍矿、铁矿、石棉矿、菱镁矿、蛇纹石纳米管材料等多种金属和非金属矿产。目前,煎茶岭镍矿床已进入开采阶段,金矿也进行外围找矿。研究该区的构造变形不仅可以为恢复扬子板块和秦岭造山带区域构造演化规律提供最直接和最基本的地质素材,而且还可以分析矿田内金镍矿的控矿规律,指导今后找矿工作,因此,煎茶岭金镍矿田构造研究具有重大的理论和实际意义。本文采用构造解析的方法,以煎茶岭金镍矿田构造特征为研究中心,将区内控岩控矿作用作为研究重点,并以区域构造、构造地质学、构造岩石学、地球化学、同位素年代学和矿床学等学科理论为基础,系统研究矿田构造特征与演化规律、金镍矿的控矿构造特征和控岩控矿作用,进而探讨了研究区内找矿方向。取得的主要成果和认识可概括为以下几点：(1)分析了变质基底中元古界接官亭多期褶皱变形：中元古代初期,中基性火山岩、酸性火山岩以及火山凝灰岩生成之后,接官亭组沉积了少量碎屑岩和炭质泥岩；中元古代末期,接官亭组发生第一期褶皱,褶皱的北翼为正常翼,南翼为倒转翼,轴面产状S1≈216°∠45°,形成的重斜褶皱枢纽产状为β1≈215°∠50°,晚期褶皱叠加在早期重斜褶皱之上,致使早期轴面发生弯曲,形成背斜,其轴面产状165°∠75°,枢纽产状β2≈70°∠20°。加里东早期,盖层在构造运动作用下形成了一系列轴面近东西向褶皱,主要有：断头崖向斜、九道拐向斜、官地梁向斜、西渠沟背斜等,其中,九道拐向斜和断头崖向斜为似箱状褶皱,枢纽向东倾伏,倾伏角20°-30°；西渠沟背斜为线性褶皱,两者轴面走向115°-120°；官地梁向斜为短轴褶皱。本区地层受多期褶皱控制。(2)在煎茶岭金镍矿田厘定了两条区域韧性剪切带：北西西向区域韧性剪切带和北东向区域韧性剪切带(以下简称北西西向韧性剪切带和北东向韧性剪切带)。通过野外调研和室内定向薄片鉴定以及透射电子显微镜观察,对其运动学、动力学特征进行了系统总结。研究还发现,这两组共轭韧性剪切带的形成与演化不仅对煎茶岭超基性岩、花岗斑岩及钠长斑岩具有严格的控制作用,而且还是重要的控矿因素。矿田内新厘定两条韧性剪切带特征表现为：北西西向韧性剪切带和北东向韧性剪切带呈共轭产出,经历了三期活动。中元古代晚期,北西西向脆韧性剪切带为压扭性右行剪切,北东向脆韧性剪切带为压扭性左行剪切,σ1≈282°∠24°,古应力值约59.1MPa,动力变质作用达高绿片岩亚相,两者均为平面型应变；加里东期,北西西向脆韧性剪切带为张扭性右行剪切,北东向脆韧性剪切带为张扭性左行剪切,σ1≈344°∠78°,古应力值约86.5MPa,动力变质作用为中绿片岩亚相；印支期,随着脆性程度进一步增加,北西西向韧脆性剪切带经历了压扭性左行剪切,北东向韧脆性剪切带经历了压扭性右行剪切,σ1≈120°∠20°,古应力值约116.3MPa,动力变质作用为低绿片岩亚相,两者为压扁型应变特征。北西西向韧性剪切带总拉伸量为0.259%,第一、二期右行位移量为0.98km,第三期左行位移量为1.65km,二者相差0.67km。(3)对煎茶岭超基性岩和花岗斑岩的岩体构造进行了初步研究,提出了煎茶岭超基性岩体和花岗斑岩岩体的就位机制：北西西向和北东向韧性剪切带中期活动过程中,超基性岩体以岩墙扩展式侵入到韧性剪切带内后经历了剪切作用的改造生成蛇纹质糜棱岩、滑镁质糜棱岩和糜棱岩化菱镁岩等动力变质岩；两韧性剪切带第三期活动时,花岗斑岩体以气球膨胀式侵位。根据岩体与围岩的接触关系,对超基性岩形成的地质时代提出了新的认识。由于岩体与震旦纪白云岩和炭质片岩存在穿插关系,而且在超基性岩内多处发现它们的捕虏体,因此认为超基性岩形成的地质时代应晚于震旦纪。结合韧性剪切带活动期次,超基性岩形成于加里东期。(4)通过控矿因素和矿床地质特征的研究,针对煎茶岭金、镍矿床,提出了韧性剪切带-超基性岩-酸性岩体(脉)三位一体的成矿机制。认为煎茶岭金、镍矿床具有相同的控矿因素和相似的成矿作用,它们是在统一的成矿系统中不同的物理化学条件下,在同一地质时期形成的。(5)煎茶岭花岗斑岩体结晶时代确定为216±4Ma,其代表时代为三叠纪(印支期),通过综合研究,认为花岗斑岩与金、镍矿床和韧性剪切带具有密切的时间、空间和成因联系。说明煎茶岭金镍矿的成矿时代是印支期,同时限定了第三期韧脆性剪切活动发生在印支期。(6)总结了煎茶岭金镍矿田内控矿韧脆性剪切带特征和控矿规律。金矿控矿构造位于构造蚀变超基性岩体与白云质糜棱岩接触带附近的韧脆性剪切带之中,总体倾向100°-50°,局部东倾,倾角变化于50°-85°之间,无论沿走向还是顺倾向均呈舒缓波状；发育的动力变质岩主要以韧脆性变形为主；利用透射电镜观察,与金矿有关的脉石英形成大量的位错弓弯、位错环、位错列、位错壁、位错网、亚晶粒构造等；金矿体绕超基性岩分布,形成“金项链”控金格局。镍矿控矿构造位于以花岗斑岩为核的“σ”型“旋转碎斑系”拖尾内韧脆性剪切带之中,即花岗斑岩体西北和东南方位拖尾部位；控矿构造产状为170°-200°∠56°-80°,无论沿走向还是顺倾向均呈舒缓波状；发育的动力变质岩以韧脆性变形为主,构造岩中可见S-C面理、旋转碎斑系、亚颗粒、膝折带等；目前,发现的绝大部分镍矿体位于“旋转碎斑系”的北西向“拖尾”中,东南“拖尾”中也发现很好的镍矿化,具有极好的成矿条件。(7)根据本论文研究成果,笔者认为煎茶岭金镍矿田构造演化时序可能是：①晚太古代末期,鱼洞子群经历了强烈变形变质作用的改造,生成花岗质片麻岩、浅粒岩、变粒岩、磁铁石英岩等,同时发育褶皱,变质作用达(低)角闪岩相。随后,该区处于隆起剥蚀阶段。②中元古代末期,在接官亭组地层形成并发生多期变形之后,区内发生了韧性剪切变形,形成北西西向和北东向两条共轭韧性剪切带。随后地层挤压褶皱隆升,在接官亭组产生了一系列褶曲,同时在鱼洞子群,该期褶皱叠加在早期等斜、同斜及重斜褶皱之上。③晚元古代晚期,研究区随扬子板块一同进入稳定的被动大陆边缘演化阶段,广泛沉积了下震旦统断头崖组和九道拐组,断头崖组与中元古界接官亭组呈明显的角度不整合接触。④加里东期,研究区发生一期强烈挤压褶皱和推覆构造之后,再次发生韧性剪切活动,北西西向和北东向张扭性韧性剪切带交汇部位变形相对较强烈,形成薄弱地带,且向下有较大延伸,提供了超基性岩浆侵入的有利通道,形成了煎茶岭超基性岩,随着剪切活动的持续进行,岩体也随之发生了强烈的塑性变形。由于地壳上隆,区内缺失寒武纪-泥盆纪地层。⑤印支期,区内构造再次活动,引起北西西向和北东向韧性剪切带发生第三期活动,随之带内有花岗斑岩和钠长斑岩脉侵入。⑥印支运动之后(燕山-喜山期),三角区和扬子板块向秦岭俯冲碰撞造山,导致研究区内南北地层不同程度的剥蚀,F18以北九道拐组和略阳组地层大部分被剥蚀,其程度明显大于南部。(8)根据“韧性剪切带-超基性岩-酸性岩体(脉)三位一体”的原则,笔者圈出四个金、镍矿的成矿远景区：构造蚀变超基性岩体东南部金矿成矿远景区、花岗斑岩东南和西北部镍矿成矿远景区、九道拐金镍矿成矿远景区。本文创新点有如下两点：①笔者在煎茶岭金镍矿田新厘定了两条区域韧性剪切带：北西西向区域韧性剪切带和北东向区域韧性剪切带,详细研究了它们的几何学、运动学、动力学以及两韧性剪切带相互关系、变质相、变形期次和构造应力场等特征,进而探讨了它们对矿田内超基性岩体、花岗斑岩体、钠长斑岩脉以及金镍等矿产的控制作用。②总结了煎茶岭金镍矿田内控矿韧脆性剪切带特征和控矿规律。控金构造是蚀变超基性岩体与白云质糜棱岩接触带附近的韧脆性剪切带,金矿体绕超基性岩分布,形成“金项链”控金格局；镍矿控矿构造是以花岗斑岩为核的“σ”型“旋转碎斑系”拖尾内韧脆性剪切带。目前,发现的绝大部分镍矿体位于“旋转碎斑系”的北西向“拖尾”中,东南“拖尾”中也发现很好的镍矿化,具有极好的成矿条件。更多还原

【Abstract】 Jianchaling gold and nickel ore field, which has the unique tectonic structure position, is located in the combining site between the Yangtze plate and Qinling orogenic belt. Jianchaling is just a small place where gathers many kinds of minerals, such as gold minerals, nickel minerals, iron minerals, asbestos minerals, magnesite, serpentine nanotubes and other materials of metal and non-metallic minerals. Jianchaling nickel deposit has been exploiting, gold minerals has been prospecting external at present. The research of the tectonic deformation in this area not only provides the most directly and basically geological material to restore the tectonic evolution regularity of Yangtze plate and Qinling orogenic belt, but also analyzes the ore-controlling rule of the gold and nickel ore in ore field, which can be used to guide further exploration. Therefore, the research of the structure in Jianchaling gold and nickel ore field has great theoretical and practical significance.Using structural analysis methods, with the structure characteristics of Jianchaling gold and nickel ore field as the research center and focusing on the rock-controlling and ore-controlling structure, based on the theory of regional tectonic rule, structural geology, structural petrology, geochemistry, isotope chronology, the mineral deposit geology and other subjects, structure characteristics and evolution regularity of ore field, ore-controlling structure characteristics, rock-controlling and ore-controlling structure are studied systematically, and then discuss how to find other minerals. The main achievements and conclusions of this paper are as follows:(1) The multi-episodic deformation of Mesoproterozoic metamorphic basement in Jieguanting Formation is analysed:In the early Mesoproterozoic, after the intermediate-basic volcanic rocks, medium acid volcanic rocks and cinerite were formed, a small amount of clastic rocks and carbonaceous mudstone are deposited in Jieguanting Formation; in the later of Mesoproterozoic, the first-phase fold occured in the Jieguanting Formation, the north wing of the fold is normal and the south wing is reversed, axial surface occurrence is S1≈216°(?)45°, hinge of fold isβ1≈215°(?) 50°, late fold overlied on the early fold make early axial surface curve to form an antiform anticlinal fold, which axial surface occurrence is 165°(?)75°, hinge of fold isβ2≈70°(?)20°. In the early Caledonian, because of the tectonic movement, overlying strata formed a series of nearly east-westward folds, such as Duantouya syncline, Jiudaoguai syncline, Guandiliang syncline, Xiqugou anticline and so on. Jiudaoguai syncline and Duantouya syncline are box-like folds, pitching angle is 20°-30°; Xiqugou anticline is linear anticline fold, the occurrence of axis surface is 115°-120°; Guandiliang syncline is a short axis fold. The stratums are controlled by the folds in this area.(2) Two area ductile shear belt in Jianchaling ore field are determined:NWW area ductile shear belt and NE area ductile shear belt(NWW ductile shear belt and NE ductile shear belt for short below). Based on the methods of field geological survey, ultramicrostructural and microstructural observation in laboratory, the kinematics and kinetics characteristics of two ductile shear belts are studied systematically. It is also found that the formation and evolution of the two ductile shear belts are not only strict controlling role, but also an important ore-controlling factors to Jianchaling ultrabasic rocks, granite porphyry and albitophyre.The characteristics of two ductile shear belts in the ore field are as follows:NWW ductile shear belt and NE ductile shear belt are conjugate, and both have the three activitie stages:At the late of Mesoproterozoic, NWW ductile shear belt is compressive and shear, surname cut; NE ductile shear belt is compressive and shear, sinistral cut,σ1≈282°(?)24°, paleostress value is about 59.1MPa, dynamometamorphism reached high greenschist-facies, both of which are flat-type strain; In Caledonian-Hercynian, NWW ductile shear belt is tension-shear, surname cut; NE ductile shear belt is tension-shear, sinistral cut,σ1≈344°(?)78°, paleostress value about 86.5MPa, dynamometamorphism reached middle greenschist-facies; in the Indo-Chinese epoch, with the degree of brittle further increasing, NWW shear ductile belt is compressive and shear, sinistral cut, NE ductile shear belt is compressive and shear, surname cut,σ1≈120°(?)20°, paleostress value is about 116.3MPa, dynamometamorphism reached low greenschist-facies, both are the flattening strain. the total draft of NWW ductile shear belt is about 0.259%, the total displacement of the first and second phases is about 0.98km, the sinistral displacement of the third phase is about 1.65km, and the difference between both is 0.67km.(3) By the preliminary study of Jianchaling ultrabasic rocks and granite-porphyry structures, the emplacement mechanism of Jianchaling ultrabasic rocks and granite-porphyry are proposed. During the medium-term activity of NWW ductile shear belt and NE ductile shear belt, ultrabasic rocks intruded into two ductile shear belts by the way of dike propagation, and then the shear transformated formed serpentinite mylonite, mylonitization magnesite and other dynamic metamorphism rocks; during the third phase of activities of two ductile shear belts, the granite-porphyry emplaced like a expandable balloon. According to the contact relation between rock mass and the surrounding rocks, a new understanding of the ultrabasic rocks formation period is proposed. Because some intrusive relation and many xenoliths are found in the rock mass and Sinian dolomite or the carbonaceous schist, the formation of ultrabasic rocks should be later than the Sinian; according to the activity issue of two ductile shear belts, it is formed in Caledonian.(4) According to the research of ore-controlling factors and geological features of mineral deposits, "three factors and one orebody" ore-forming mechanism, which is the ductile shear belts-ultrabasic rocks-acid-instrusions(veins), is proposed. Jianchaling gold and nickel deposits have the similar ore-controlling factors and mineralization, they are in a unified metallogenic system, but in the different physical and chemical conditions and formed at same time.(5) The crystallization age of the Jianchaling granite-porphyry is 216±4Ma, and it is belong to the Triassic (Indosinian), by the comprehensive study, the granite-porphyry and gold and nickel deposits are close connection with time, space and cause of formation, So Jianchaling gold nickel mineralization era is Indosinian, and the third activity of ductile-brittle shear occurred in Indosinian too.(6) The characteristics and ore-controlling disciplines of the ore-controlling ductile-brittle shear belts in the Jianchaling gold and nickel ore field are summarized. Gold ore-controlling structure is in ductile-brittle shear zone which is near contact zone between the structural alteration ultrabasic rocks and dolomitic mylonites contact zone, the general tendency is 10°-50°, the local tendency is east, obliquity changes are between 50°and 85°, both along the strike and the tendency show the wave-like. The dynamic metamorphic rock mainly consisted of ductile deformation, using transmission electron microscopy, and gold-related quartz veins formed a lot of dislocation arches, dislocation loops, dislocation lines, dislocation walls, dislocation nets, second grain structure and so on. Ore bodies are around the ultrabasic rocks and form the "gold necklace" ore-controlling pattern. Nickel ore-controlling structures are the ductile-brittle shear belts among the granite porphyry northwest and southeast direction trailing position, which the core of "a-type rotating porphyroclasts system" is granite porphyry. The occurrence of Ore-controlling structures is 170°-200°(?) 56°-80°, both along the strike and the tendency show the wave-like, the dynamic metamorphic rock is mainly ductile deformation, S-C surface is visible in the tectonic foliation, also the rotating porphyroclasts system, sub-particles, kink band. Currently, most of nickel ore bodies are found in the north-western "tail" of "rotating porphyroclasts system", the south-east "tail" is also a very good nickel mineralization with excellent mineralization conditions.(7) According to the research of this paper, the tectonic evolution of Jianchaling gold nickel ore field should be:①At the end of the late Archean, Yudongzi Group has a strong transformation of deformation and metamorphism to generate granitic gneiss, leucoleptite, granulite, magnetite-quartzite and so on, and folds were formed simultaneously, metamorphism was (low) amphibolite facies. Subsequently, the district is in the uplift denudation phase.②At the late Mesoproterozoic, a ductile shear deformation occured in the ore field after Jieguanting Formation generated, formed the NWW and NE direction ductile shear belts. Series of heavy oblique folds were formed in Jieguanting Formation, because of extrusion, the strata folded and uplifted, at the same time in Yudingzi Group, these folds superposed those earlier inclined and oblique folds.③At the end of Late Proterozoic, the studying area along with the Yangtze plate went to the evolution stage of stably passive continental margin, the Lower Sinian Duantouya Formation and the Jiudaoguai Formation are deposited extensively, and the Duantouya Formation and the Middle Proterozoic Jieguanting Formation emerged a clear angle unconformity.④During the Caledonian, a strong compressive folds and nappe structure occurred in the studying area, and the deformation of the intersection between NWW direction and the NE ductile shear was stronger, and produced some weak areas and extended downwards, which provided the good invasion channel for ultrabasic magma, and the ultrabasic rocks were formed, with the last shearing activities. The strong plastic deformation of the ultrabasic rocks has taken place. As the crust uplifting, the Cambrian-Devonian stratas are worn away.⑤In the Indo-China period, tectonic active took place in the region again, and caused the third shear of the NWW direction and NE ductile shear belts, the granite-porphyry, diabase dikes, and albite porphyry invaded.⑥After Indo-China movement (Yanshan-Himalayan), triangle area and the Yangtz plate subducted to the Qinling, and formed Qinling orogenic belt, which resulted differnet degree erosion between north strata and south strata, In the north of F18, Jiudaoguai Formation and the majority of the Carboniferous Lueyang Formation were denudated greater than the south significantly.(8) According to the " three factors and one orebody " principle, four gold and nickel mineralization prospect areas are pointed out. They are gold mineralization prospective areas in southeast structure altered ultrabasic rocks, nickel mineralization prospective areas in the southeast and northwest of graniteporphyry, gold and nickel mineralization prospective areas in Jiudaoguai. What is new?Firstly, two area ductile shear belts are determined in Jianchaling ore field:NWW ductile shear belt and NE ductile shear belt, the author studies the characteristics of geometry, kinematics,kinetics detailedly, and correlation between the two ductile shear belts, metamorphic facies, phase of deformation and structure stress field. And the author further discussed their control action to ultrabasic rocks, granite porphyry, albitophyre and gold and nickel deposits in the ore field.Secondly, the characteristics of ductile brittle shear belts and ore-controlling regulation in Jianchaling gold and nickel ore field are summed up. The gold-controling structure is the ductile brittle shear belts, which is near contact zone between the altered ultrabasic rocks and dolomitic mylonites, and formed the ore-controlling pattern like " gold necklace" around the ultrabasic rocks. Nickel ore-controlling structures are the ductile-brittle shear belts among the granite porphyry northwest and southeast direction trailing position, which the core of "a-type rotating porphyroclasts system" is granitic porphyry. At present, the main nickel ore bodies were found in the the northwestern "tail" of "rotating porphyroclasts system", the southeast "tail" was also found a very good nickel mineralization, with excellent mineralization conditions.更多还原