【作者】 张克信；

【导师】 殷鸿福；

【作者基本信息】 中国地质大学 ， 古生物学与地层学， 2000， 博士

【摘要】 正确展示造山带现今三维结构,恢复其铸就现今三维结构之形成演化历程是造山带地质调查与研究的核心内容。造山带类型复杂多样,不同类型的造山带有着各自不同的形成机制、演化历程和各自不同的三维结构,但各类造山带有其共性,其共性就是在造山带的整个演化历程中,曾经历过强烈的构造搬运和构造混杂过程,即非史密斯化过程。造山带非史密斯地层构成具如下独特性和复杂性:造山带在俯(仰)冲碰撞和陆内造山阶段,发生过强烈的构造搬运和构造混杂,构造形迹多样化,垂直不长的地层体往往是众多不同来源、不同时代,不同变形变质程度,不同大小的各种构造岩片拼贴体,地层原始层序被严重肢解、破坏;尤以产于俯冲带的俯冲增生杂岩楔的原始形成方式与史密斯地层学的“层序叠覆律”老下新上的顺序正好相反,其混杂岩增生方式是老的“片体”在上,新的“片体”阶段性拼贴在老的“增生片体”的斜下方,这种增生片体的原始位置亦与“原始水平律”相悖,即增生片体一般保持较高角度倾斜;在岩石类型和变质程度上,造山带海相和古陆缘火山岩以及变质岩普遍发育,尤其是超基性、基性岩系分布广泛,变质作用较强,伴有从百余公里以下深部超高压变质岩片的折返和同造山期与造山后期岩浆活动,构成极为复杂的地质景观。非史密斯化过程使造山带地区变为极其复杂的物质混合场,传统的史密斯地层研究方法已难以适应满足造山带地层研究、填图与生产实践的需要,如何对造山带混杂岩区进行精细的地层学调查就变成了亟待解决的问题,这就要求我们必须更新观念,非史密斯地层(non-Smithian strata)这一新的地层学概念因之应运而生,旨在精细恢复造山带组成、结构、形成和演化历程,进一步提高我国造山带区地质研究与环境资源调查评价水平。研究区位于东昆仑与西秦岭以及柴达木板块与华南板块结合带,其洋陆转化阶段经历了元古代,早古生代,晚古生代-早中生代多期造山旋回,地层、岩石和构造十分复杂,区内存在两条时代各异的蛇绿混杂岩带,北为东昆中—东昆南复合蛇绿混杂岩带,南为阿尼玛卿蛇绿混杂岩带,它们代表两条时代各异的缝合带,为研究运用非史密斯地层理论方法,进行造山带组成、结构、演化模式调查研究,进而研究秦昆巨型造山带及中国西部南北板块演化研究提供了一个十分理想的场所。本文通过对东昆仑造山带东段混杂岩区大量野外调查(实测混杂岩剖面21条总长160km;混杂岩区1:25万地质填图路线总长1640KM)和室内测试分析研究的基础上,对混杂岩带内各类岩石建造体从地层学角度进行了详实的野外划分和室内测试及综合分析,并在充分收集和借鉴前人研究成果的基础上,取得如下主要结论:1.从理论上阐述了非史密斯地层的概念、研究对象和基本构件:非史密斯地层(non-Smithian strata)是指那些经历过不同程度的混杂建造,并经历了变位,变形、变质,全部无序或部分无序的地(岩)层,主要指造山带地层中的无序部分;混杂岩是非史密斯地层的唯一研究对象;混杂岩中的构造岩片(块)是非史密斯地层基本构件之一,亦是非史密斯地层和地质填图基本单位之一,岩片(slice)是指以构造拼合边界所分割的具有一定物质构成的地质体;物质建造形成于同一大的构造旋回期(如晋宁期、加里东期、海西期等)、亲源关系密切、大致经历了相似变形、变质历程的一套岩片组合体被称之为超岩片(superslice)。2.以殷鸿福等(1998)归纳总结的非威尔逊旋回理论为指导,从理论上阐述了非史密斯地层形成过程:造山带区古大洋相当复杂,尤其是中国古特提斯域古大洋,多为多岛洋(海),多岛洋是一个宽阔(可达数十纬度)的但不干净的洋,它在其各个演化阶段,始终充满着由裂解地块、裂谷、海道、微板块与次级小洋(海)盆、火山岛弧、海山与边缘海等不同裂离与聚合程度的、海陆相间的多岛洋盆;多岛洋盆在其整个洋陆转化进程中,往往所经历的是多期开合与多期次软碰撞,故由非威尔逊旋回转化而来的造山带混杂岩带地层一般都经历过多期强烈的构造混杂,使造山带演化不同期次、同期次不同阶段、不同大地构造相、不同沉积古地理单元、不同构造层次(深部-浅表构造层次)地层体在极短程内相互拼贴、无序叠置。3.对研究区造山带混杂岩非史密斯地层单元系统建立、划分、名词术语、命名原则、和生产应用(造山带混杂岩区地质填图技术路线)等首次提出了一套系统的理论方法体系:提出了造山带非史密斯地层“构造岩片四维裂拼复原原理”和构造岩片的“物态、时态、相态、位态和变形、变质历程”分析法。并从野外实际出发,将1:25万冬给措纳湖幅混杂岩区划分为两大混杂岩带,两亚带,14个超岩片。14个超岩片按岩性岩相不同,又划分出15类岩片,并对它们均进行了较深入的“物质构成、时、相、位和变形、变质历程”调查分析。4.在岩片和超岩片时态调查方面取得如下重要进展:(1)在沟里、龙什更公坞等地区的由中浅变质岩岩片构成的“哑地层”中获取较丰富的疑源类和少量放射虫化石,使该套地层从化石方面首次获得了确切的时代证据,并新获一大批同位素年龄数据(14个),年龄值主要分布在1000—500Ma之间,化石时代与同位素测年吻合较好。(2)首次在花石峡—长石头山一带的“马尔争组”中发现与该带(布青山蛇绿混杂岩带)蛇绿岩岩片有密切联系的紫红色放射虫硅质岩,并分离出丰富的深海相早二叠世放射虫化石,为该带蛇绿岩的形成时代提供了有重要价值的参考年龄。(3)对构成布青山蛇绿混杂岩带相关的各类沉积岩岩片,按岩片类型不同分别进行了详细的生物地层研究,获得丰富的有孔虫、蜒、珊瑚动物、海绵动物、钙藻、孢粉和遗迹化石,首次从生物群角度详细阐明了有关岩片(块)的地质年代、形成时的古生态与古环境,充分刻画了该带混杂岩构成的的细部特征,为阿尼玛卿造山带的形成演化研究从古生物角度提供了详实的基础地质资料。5.通过对东昆仑东段造山带细致解剖,对运用大地构造相方法剖析混杂岩带非史密斯地层方面进行了有益尝试。以造山带时间演化为主线,据造山带不同演化阶段、不同部位出现的构造古地理单元、盆地类型和物质建造类型,对1:250000冬给措纳湖幅大地构造相进行了较精细深入划分,共划分出7大相类,21种相,运用大地构造相理论与方法,较全面细致地揭示了东昆仑造山带东段造山带形成、物质组成及演化过程。6.对东昆仑造山带东段前晋宁—印支期多期洋陆转化过程和非史密斯地层形成历程进行了研究。研究表明,沿东昆中断裂带分布的蛇绿岩具有多期性,是多旋回裂拼作用的综合产物,蛇绿岩至少存在中元古代、加里东期和海西期三个时代,混杂岩带不能仅限于东昆中断裂带附近,整个东昆南地区实际上都是一系列不同时代、不同来源、不同构造变形型式的构造岩片组成的构造混杂物质场。由于构造混杂岩表现为不同时代的相互交织,故以“东昆南复合混杂岩带”相称。根据带内基底岩石性质的不同和演化历史的不同,可进一步划分为北部蛇绿构造混杂岩带和南部构造混杂岩带。北部蛇绿构造混杂岩带不同时代蛇绿岩广泛分布,至少经历了前晋宁旋回,晋宁——加里东旋回,海西一印支旋回三大旋回的洋陆转换。南部构造混杂岩带结构和演化相对较简单,其基底岩系相对年青,为中元古界角闪岩相变质的苦海杂岩。苦海杂岩在变质岩石学方面与北部白沙河岩群或小庙岩群存在明显差别,是不同于北部的独立块体。基底岩系块体外围为活动类型的晚古生代早石炭世—中二叠世沉积建造,这些晚古生代沉积区域与更南部的阿尼玛卿海西期大洋存在成因联系,具分支海槽特点。上二叠统—中三叠统(包括格曲组、洪水川群和闹仓坚沟组)角度不整合于下覆岩系之上,代表碰撞后的前陆盆地堆积。从沉积建造反映的南部构造混杂岩带似乎只经历了海西期一印支期单旋回的洋陆转换,但在该构造带基底岩系中发育较多的加里东期同构造花岗岩类,说明加里东旋回的构造活动在该亚带也有较深的印迹。东昆仑阿尼玛卿蛇绿构造混杂岩带包含了准原地系统的布青山—花石峡超岩片、马尼特超岩片和外来系统的推覆体超岩片。该带北以沿冬给措纳湖经红水川向阿拉克湖一线的NWW向昆南活动大断裂与东昆南构造混杂岩带相邻,南以NWW向的长石头山大断裂与巴颜喀拉地块相接。布青山一花石峡超岩片组成较复杂,包括中元古界角闪岩相变质的苦海杂岩岩片、不同时代蛇绿岩岩片、早二叠世—早三叠世复理石楔岩片、中酸性火山岩岩片和碳酸盐岩片以及早侏罗世羊曲组的陆相碎屑岩岩片。其中蛇绿岩组合至少可分出两套,其一就位于变质的苦海杂岩中,被加里东期岛弧型花岗岩侵入切割,可能属加里东期或前加里东期的蛇绿岩组合;其二就位于早二叠世—早三叠世布青山群马尔争组中,包括超镁铁质岩、玄武岩、辉绿岩墙及远洋硅泥质岩组合,其中硅质岩中发现有早二叠世放射虫,说明其形成于海西期。马尼特超岩片的物质组成相对较简单,主要由布青山群马尔争组的复理石楔岩片、蛇绿岩岩片、碳酸盐岩片等构成,未见深变质岩岩片。两超岩片中的化石资料均显示出二叠纪与三叠纪沉积物质的复杂交织,但北侧布青山一花石峡超岩片中的远洋硅质岩属早二叠世,与其成带相伴的蛇绿岩组合也应属早二叠世,因此,总体来说布青山—花石峡超岩片要较南侧的马尼特超岩片原岩的发育略早些,两超岩片中的蛇绿岩分别成带出现可能反映往南后退式的俯冲增生混杂。国际地层指南(赫德伯格H.D.,1976)的一个重大贡献就是推动了地层的多重(种)划分对比研究。该理论认为:岩层有多少可用作地层划分的特性,就可能作多少种划分。但仅据岩层任一性质和属性划分的地层位置不一定与其它的任一种性质或属性划分的地层位置一致,其界线往往互相交叉。非史密斯地层的出现,同近二十年其它地层学科分支(如事件地层、成因地层、生态地层、层序地层、构造地层等)如雨后春笋般出现一样,是旨在从“构造岩片的四维裂拼复原”方面细致刻画造山带各类混杂建造特征。显然这一新的学科分支的研究目标与其它地层学学科分支是一致的,都是设法“据岩层的某种性质和属性”来刻画岩层的不同特征,最后达到对岩层所有属性的全面认识。因此,非史密斯地层的提出,不是对从前所有地层学学科分支的冲击和排斥,而是一种重要补充,尤其是与构造地层的关系,是相辅相成的两姊妹学科,两学科同都是解开造山带无序或部分无序地(岩)层特征的两把钥匙:构造地层侧重于地(岩)层构造形变样式和期次的分析,而非史密斯地层则侧重于通过混杂堆积中构造岩片四维裂拼复原分析,着重了解各构造岩片的物质组成、原生成生时代、相环境、古大地构造背景和变形变质历程。更多还原

【Abstract】 The key target of the study in orogenic belt is to properly reconstruct their three-dimension architecture and uncover their evolution. Though orogenic belts are varied, and different orogenic belts have different mechanisms, evolutions and three-dimension architectures, all orogenic belts have experienced strong tectonic migration and mixing, which are called non-Smithization .The orogenic strata have following characteristics: During the subduction (obduction) and intracontinental orogeny, the strata experienced dramatic tectonic migration and mixing, resulting in various tectonic features. A short sequence usually composed of tectonic slices of various origins, times, deformations and metamorphisms, and scales. The original sequence was badly destroyed. The extant fragments of orogenic belt usually took form as melanges, especially the accretion complex wedge generated in subduction zone, which is contrary to the Law of Superposition. The original location of the accretion is also contradicted with the Law of Original Horizonality, because the accretion is oblique with high degree. Marine rocks, volcanic rocks of continental margin and metamorphic rocks were well-developed in the orogenic belt, especially ultra-basic, basic rocks were wide spread and were intensely metamorphosed, accompanied by metamorphic slices returned from hundred kilometers underground with ultra-high pressure and magma movements during syn-orogeny and post-orogeny, thus formed the colorful landscapes. During the non-Smithization, the orogenic belt became the integration of mixed materials, and the traditional Smith methods are no longer fit the need of the study and practice in orogenic belt. How to carry out detail study in orogenic belt need prompt solution. Thus urged us to change our old thoughts and turn to non-Smith stratigraphy for help to reconstruct and restore the architecture, component and evolution of orogenic belt, and it will enhance Chinese level on geological research and environmental surveying and appraisal.The studied area located at the junction of Eastern Kunlun and West Qinling, and the Qaidam Plate and the South China Plate. Its ocean—continent transitions underwent Proterozoic, Early Paleozoic and Late Paleozoic—Early Mesozoic cycles, so the strata, sediments and structures are rather complex. There lied two ophiolite melange belts of different ages in Eastern Kunlun Orogenic Belt, i.e., middle-south Eastern Kunlun compound ophiolite belt in the north, A’nimaqing ophiolite melange belt in the south, which stands for two sutures of different ages. All these favor the study on the components, architectures and evolutions of the orogenic belt, and further on the Qinling—Kunlun orogenic belt and on the evolution of the south and north plates of West China.Based on lots of field work (21 surveyed melange sections, totally 160 km, 1 640 km mapping route of 1∶250 000 geologic map), indoors assays and referring former researcher’s results, following conclusions are summarized.1.The conception, studied objects and basic constituents of non-Smith strata are elaborated from theory level: Non-Smithian strata are the strata that have undergone mixing of different degrees, thus were deformed, metamorphosed and displaced into disorder totally or partially. They are the disorder parts in orogenic belts. Melange is the solo studied object of non- Smithian stratigraphy. The slices (blocks) in melange is one of the basic constituents of non- Smithian strata, and also one of the basic units in the non-Smithian mapping. The slices used in this paper refer to blocks divided by small-scale tectonic boundaries and have certain constitutes. Superslices used in this paper refer to a set of slice association with similar tectonic deformation bounded by large-scale tectonic mixing.2. Guided by non-Wilson cycle theory generalized by Yin et al. (1998), the forming of non- Smithian strata are expounded at theory level. The paleo-oceans in orogenic belts were rather complex, especially the oceans in Chinese paleo-Tethys, most were archipelagos, which were broad (up to several latitudes) and unclean, with many archipelagos, a mosaic of seas and lands including rifted blocks and valleys, seaways, microplates and micro-oceans, and island arcs, seamount and marginal seas. The archipelagic oceans experienced polystage opening, closing and soft-collision during its ocean-basin transitions, so the strata in orogenic belt devolved from non-Wilson cycle usually underwent polystages strong tectonic mixings, inducing the geologic bodies of various episodes, stages of the same episodes, tectonic facies, paleogeographic units and tectonic levels patching and non-sequence imbricating one another in short distance.3. A set of systematic theory pertaining to the setting, division, terms, defining principles and practice were put forward:“four-dimension splitting-converging model of tectonic slices”and“material, age, facies, location and process of deformation and metamorphism”analysis method. 1∶250 000 Dongi Conag melange region are divided into two belts, two sub-belts, and 14 superslices, which are further divided into 15 slices according to their lithology, and are analyzed for“constituents, age, facies, location and process of deformation and metamorphism”.4. Important advance are made in the date of slices and superslices: (1) Abundant acritarch and a few radiolarian fossils are collected in the“barren strata”formed by epi-middle metamorphic slices at Gouli, Longshigenggongwu, thus provide data evidence for this set of strata. A series of isotopic dating data (14) showed that the date are between 1 000 Ma and 500 Ma, close to that of the fossils. (2) Amaranth radiolarian silicate close connected with ophiolite slices are discovered in“Ma’erzheng Fm.”along Huashxia—Long Stone Hill for the first time, and abyssal Early Permian radiolarians are got, thus provide important reference date for the forming age of ophiolite in this belt. (3) The slices constituting Buqingshan ophiolite melange belt are detailed studied on biostratigraphy, getting abundant foraminifers, fusulinida, coral, spongiaria, calcareous algae, sporopollen and trace fossils. The geologic age, paleoecology and paleoenvironment of the relative slices (blocks) are discussed from biotic standpoint for the first time. The detail biotic features of the melange provide abundant and detail data for the understanding of the forming of A’nimaqing orogenic belt.5. Based on thorough study on the east part of Eastern Kunlun Orogenic belt, a valuable try by using tectonic facies to analyze non- Smithian strata are took. Dominated by the evolution time of the orogenic belt, according to the paleogeographic units, basins and formation occurred in different stages and locations, the tectonic facies of 1∶250 000 Dongi Conag sheet are divided into 7 facies types and 21 facies. The forming, constituent and evolution of the east part of Eastern Kunlun orogenic belt are detail uncovered by using tectonic theory and method.6. Pre-Jinning—Indo-sinian polystage ocean-continent transitions and the forming of non-Smith strata are studied. Our study show that the ophiolites in the fault were the products of polycycle dispersal and convergence, and there existed at least three periods, i.e., Middle Proterozoic, Caledonian and Hercynian. The melange belt occurred not only near the fault, but the whole south part of the Eastern Kunlun, which is the integration of mixed materials formed by tectonic slices of different origins, stages and deformations. The tectonic melange are interfingered by slices of different stages, so come the name“Compound Melange Belt of the South Kunlun”, which can be subdivided into northern ophiolite melange belt and southern melange belt according to the lithology of the basements and the evolution. The northern ophiolite melange belt contains various ophiolites of different times, and at least experienced three ocean-continent cycles, i.e., pre-Jinning cycle, Jinning—Caledonian cycle and Hercynian —Indo-sinian cycle. The structure and evolution of the south tectonic melange are relative simple, and its basement, Middle Proterozoic metamorphosed diorite (Kuhai complex), is relative younger. Kuhai complex is remarkable different from the northern Baishahe Gr. or Xiaomiao Gr. in metalithology, so it is an isolated block. The outer of the basement are active Early Carboniferous-Middle Permian sediments. The Late Paleozoic sediment areas are related to the Hercynian A’nimaqing ocean in genesis, and both are branch troughs. Upper Permian—Middle Triassic (including Gequ Fm., Hongshuichuan Gr. and Naochangjiangou Fm.), which are representatives of foreland accumulation after collision, angular contacting the underlying strata. It seemed the south tectonic melange has only undergone the Hercynian—Indo-sinian ocean—continent transition from the sedimentary formation, but a few Caledonian syntectonic granites are found in the basement, which showed the Caledonian movement has also left some traces in this subzone. The A’nimaqing Melange consists of Buqingshan—Huashxia superslice, Manite superslice and allochthonous nappe superslice. The A’nimaqing Melange bordered the south melange belt on the north with the NWW South Kunlun Fault extending along Dongi Conag Lake—Hongshuichuan—Alag Lake, and the Bayan Har block on the south with NWW Long Stone Hill Fault. The Buqingshan—Huashxia superslice is complex, including Middle Proterozoic diorite-facies Kuhai melange slice, ophiolite slice of different times, Early Permian—Early Triassic flysch wedge, basic-acid volcanic slice and carbonate slice and Late Triassic—Early Jurassic Yangqu Fm. terrestrial clastic slice. The ophiolites can be divided into two groups at least; one lies in the Kuhai complex and intersected by Caledonian island granite, which may be attributed to Caledonian or pre-Caledonian ophiolite association; the other lies in the Early Permian—Early Triassic Ma’erzheng Fm. of Buqingshan Gr., including ultramafic rock, basalt, diabase dike and pelagic siliceous-argillaceous association, and Early Permian radiolarian are found in the silicates, which reflect that the time is Hercynian. Manite superslice is relative simple, dominated by the flysch wedge, ophiolite, carbonate slice of Ma’erzheng Fm. of Buqingshan Gr., lacking deep metamorphosed slice. The fossils in the two slices show mixture of Permian and Triassic, but the pelagic silicate in the Buqingshan—Huashxia slice dated as Early Permian, so the associated ophiolite should be Early Permian. So the Buqingshan—Huashxia superslice developed a little earlier than the Manite slice, and the zoned ophiolite in them may due to the southward retrogression subduction, accretion and mixing.One important attribution of International Stratigraphic Guide lies in that it encourages the study on the multiple classification and correlation of the strata. The strata can be divided into as many kinds as the dividing standards, though the dividing limits are not consistent. Like other branches of stratigraphy (evento-, geneto-, econo-, tectono- and sequence stratigraphy, and so on) appeared successively in recent twenty years, non- Smithian stratigraphy is aimed to deeply demonstrate the characteristics of various melanges in the orogenic belt from four-dimension splitting-converging of tectonic slices. Obviously, the standpoint of this new branch is different from that of the other branches, yet their aims are the same, which is to demonstrate the colorful features of the strata. Therefore, non-Smithian stratigraphy is not excluding the other branches, but an important supplement for them, especially for the tectonostratigraphy. They are twin sister branches, and they are the two keys to uncover the disorder or partially order strata in the orogenic belt. Tectonostratigraphy emphasize on the analysis of the patterns and episodes of the deformation, while non-Smithian strata stressing on understanding of the constituent, original time, environment, paleo-tectonic settings and process of deformation and metamorphism of various slices through the four-dimension splitting-converging of the tectonic slices.更多还原