皖赣鄣公山地区新元古代地壳组成及造山过程

皖赣相邻的鄣公山地区位处江南造山带北缘,区内广布一套厚度巨大、低绿片岩相变质的以泥砂质细碎屑岩为主含少量火山物质的复理石建造体,大量高精度同位素测年数据显示,其形成于821～840Ma间的新元古代早期,以景德镇-鄣源-伏川区域断裂带为界,南部为形成于大陆边缘拉张构造环境下的溪口岩群;北部的双桥山群火山-陆缘细碎屑岩系是与岛弧有关盆地中的沉积物。北东—南西向展布于鄣公山北坡的蚀变枕状-块状基性火山熔岩、辉长岩、辉绿岩等基性岩类呈构造碎块或碎片产出于溪口岩群火山-陆缘细碎屑岩组成的复理石基质中,通过对其产出地质特征及岩石地球化学特征等的分析,认为其形成于低速扩张的陆缘小洋盆扩张脊环境,具初始洋壳基性岩特征,属皖南伏川蛇绿岩西延组成部分。呈夹层产出于双桥山群地层中的大量玻屑晶屑凝灰岩及少量变安山岩、变流纹岩等具相似的岩石地球化学特征,属中钾钙碱性岩石系列,形成于大陆边缘火山弧构造环境。综合区内沉积事件、岩浆事件和构造事件等,提出皖赣相邻区新元古代经历了古扬子板块东南缘裂开-陆缘小洋盆有限俯冲-弧陆碰撞造山-造山期后陆壳裂陷沉积的构造演化过程。     

皖赣相邻鄣公山地区新元古代地壳组成及造山过程

摘要：皖赣相邻的鄣公山地区位处江南造山带北缘,区内广布一套厚度巨大、低绿片岩相变质的以泥砂质细碎屑岩为主含少量火山物质的复理石建造体,大量高精度同位素测年数据显示,其形成于821-840Ma间的新元古代早期,以景德镇-鄣源-伏川区域断裂带为界,南部为形成于大陆边缘拉张构造环境下的溪口岩群;北部的双桥山群火山-陆缘细碎屑岩系是与岛弧有关盆地中的沉积物。北东-南西向展布于鄣公山北坡的蚀变枕状-块状基性火山熔岩、辉长岩、辉绿岩等基性岩类呈构造碎块或碎片产出于溪口岩群火山-陆缘细碎屑岩组成的复理石基质中,通过对其产出地质特征及岩石地球化学特征等的分析,认为其形成于低速扩张的陆缘小洋盆扩张脊环境,具初始洋壳基性岩特征,属皖南伏川蛇绿岩西延组成部分。呈夹层产出于双桥山群地层中的大量玻屑晶屑凝灰岩及少量安山岩、流纹岩等具相似的岩石地球化学特征,属中钾钙碱性岩石系列,形成于大陆边缘火山弧构造环境。综合区内沉积事件、岩浆事件和构造事件等,提出皖赣相邻区新元古代经历了古扬子板块东南缘裂开－陆缘小洋盆有限俯冲－弧陆碰撞造山－造山期后陆壳裂陷沉积的构造演化过程。     

江南造山带北缘鄣源基性岩地质-地球化学特征及成因机制

鄣源基性岩呈北东-南西向分布于皖赣相邻区鄣公山北坡瑶里-鄣源-江潭一带,以构造砰块或砰片形式严于新元古代火山-陆缘细碎屑岩组成的复理石基质中,总体显示构造混杂岩带特征.基性岩残块包括蚀变枕状-块状基性熔岩、辉长岩、辉绿岩等,它们在空间上紧密相伴,形成于新元古代.通过对鄣源基性岩地质及岩石地球化学特征等的分析,认为其形成...     

东昆仑造山带东段昆中复合蛇绿混杂岩带及"东昆中断裂带”地质涵义

东昆中断裂带中存在多期蛇绿岩组合,分别代表中元古代、新元古代-早古生代和晚古生代3次裂解成洋.断裂带中主要的3类各不相同的韧性剪切构造变形组合分别可与新元古代早期、加里东期末和晚海西期的3次碰撞缝合事件相匹配."东昆中蛇绿混杂岩带"不能仅限于东昆中断裂带,而应包括原东昆中蛇绿混杂岩带和整个东昆南单元,是一多旋回俯冲碰撞的复合蛇绿构造混杂岩带.东昆中断裂带作为统一的纵贯东昆仑造山带的线性构造变形带应形成于印支期陆内构造变形阶段,是碰撞后的陆内构造变形产物.     

江南造山带东段新元古代至早中生代多期造山作用特征

新元古代江南造山带远离晚中生代活动大陆边缘,是研究华南地区新元古代至早中生代多期造山作用的理想对象。文章通过对江南造山带东段沉积建造、岩浆活动、构造变形以及同位素年代学数据的综合分析,总结了其晋宁期、广西期以及印支期造山作用的特征。江南造山带东段在晋宁期经历了南北两侧大洋俯冲和两期碰撞造山作用。新元古代早期(880~860 Ma)双溪坞岛弧与扬子陆块东南缘发生弧-陆碰撞作用,形成淡色花岗岩、高压蓝片岩、NNE向褶皱-逆冲构造以及弧后前陆盆地。新元古代中期(约850 Ma),扬子陆块北缘开始发育由北向南的大洋俯冲。随着俯冲作用的进行,弧后盆地发生关闭,扬子陆块与华夏陆块发生陆-陆碰撞并形成新元古代(820~810Ma)江南造山带,导致近E-W走向褶皱-逆冲构造、韧性变形以及过铝质花岗岩的发育。江南造山带东段在约810Ma开始发生后造山垮塌和裂谷作用,以发育南华纪早期(805~750 Ma)花岗岩、中酸性火山岩、基性岩以及裂谷盆地为特征。江南造山带东段万载—南昌—景德镇—歙县断裂带以南地区卷入了华南广西期造山作用,发育近E-W走向由南向北的逆冲构造(465~450 Ma)、NNE向正花状构造(449~430 Ma)以及后造山近E-W走向韧性走滑剪切带(429~380 Ma)。印支期造山作用导致了NNE向褶皱-逆冲构造和花岗岩的发育,并奠定了江南造山带东段的基本构造面貌。     

湖南城步火成岩锆石SHRIMP U-Pb年龄及其对江南造山带新元古代构造演化的约束

目前对新元古代中期江南造山带构造演化及钦杭结合带南西段构造性质存在不同认识。本文对湘西南城步地区新元古代火山岩和花岗岩进行了锆石SHRIMPU-Pb年龄测定并厘定其构造环境,从而为区域构造演化提供了约束。城步新元古代花岗岩侵入于云场里组变质火山-沉积地层中。云场里组变质火山岩与花岗岩的锆石SHRIMPU-Pb年龄分别为828±10Ma和805.7±9.2Ma。构造环境的地球化学判别图解表明花岗岩形成于岛弧环境;区域地质背景指示云场里组可能形成于活动陆缘弧前盆地。以城步火山岩和花岗岩研究为基础,结合区域地质资料,提出新元古代中期江南造山带西段构造演化过程:872～835Ma期间为陆缘盆地;835～820Ma期间俯冲造山,江南造山带形成基性—超基性岩和早阶段岛弧花岗闪长岩,东侧的城步地区为弧前盆地;820～810Ma期间江南造山带发生弧-陆碰撞;810～800Ma期间江南造山带进入后碰撞环境并形成晚阶段强过铝(黑云母)花岗岩,东侧城步地区因华南洋洋壳俯冲而形成新的岛弧;800Ma后华南进入伸展裂陷盆地演化阶段。上述认识揭示出扬子陆块东南缘的连续岛弧增生过程,同时为钦杭结合带南西段雪峰期"残留洋盆"属性提供了新证据。     

华南鹰扬关构造带的大地构造属性与构造演化过程：基于构造解析的认识

北北东向鹰扬关构造带位于华南板块西南部,其大地构造属性尚存在蛇绿混杂岩、裂谷带与陆内构造变形带之争。笔者等在物质组成与年代学综述的基础之上开展了详细的构造解析,厘定了鹰扬关构造带的大地构造属性和构造演化过程。鹰扬关构造带主体由新元古代中—晚期岛弧型安山岩和玄武岩、裂谷型双峰式火山岩、盖帽碳酸盐岩与泥砂岩等物质组成。不同时代和不同岩性的混杂是新元古代晚期裂谷和伸展构造背景下重力作用的产物。新元古代沉积混杂岩在显生宙经历了广西期、印支晚期与燕山期造山作用的叠加,导致了不同岩块之间往往呈断层接触。广西期（450~415 Ma）造山作用使新元古代沉积混杂岩发育近E—W向紧闭褶皱和逆断层并被花岗岩侵位。印支晚期（227~220 Ma）造山作用导致NNE向鹰扬关构造带的形成,表现为NNE—SSW向褶皱、逆断层与左旋韧性剪切带。燕山期造山作用使鹰扬关构造带中NNE—SSW向断裂发生构造活化,强烈的正断作用和右行走滑控制了白垩纪上叠盆地的发育。综合物质组成、年代学和构造解析证据,鹰扬关构造带不是新元古代或早古生代蛇绿混杂岩,而是印支晚期陆内构造变形带,不具有板块缝合带的大地构造属性。     

华南鹰扬关构造带的大地构造属性与构造演化过程：基于构造解析的认识

北北东向鹰扬关构造带位于华南板块西南部,其大地构造属性尚存在蛇绿混杂岩、裂谷带与陆内构造变形带之争。笔者等在物质组成与年代学综述的基础之上开展了详细的构造解析,厘定了鹰扬关构造带的大地构造属性和构造演化过程。鹰扬关构造带主体由新元古代中—晚期岛弧型安山岩和玄武岩、裂谷型双峰式火山岩、盖帽碳酸盐岩与泥砂岩等物质组成。不同时代和不同岩性的混杂是新元古代晚期裂谷和伸展构造背景下重力作用的产物。新元古代沉积混杂岩在显生宙经历了广西期、印支晚期与燕山期造山作用的叠加,导致了不同岩块之间往往呈断层接触。广西期（450~415 Ma）造山作用使新元古代沉积混杂岩发育近E—W向紧闭褶皱和逆断层并被花岗岩侵位。印支晚期（227~220 Ma）造山作用导致NNE向鹰扬关构造带的形成,表现为NNE—SSW向褶皱、逆断层与左旋韧性剪切带。燕山期造山作用使鹰扬关构造带中NNE—SSW向断裂发生构造活化,强烈的正断作用和右行走滑控制了白垩纪上叠盆地的发育。综合物质组成、年代学和构造解析证据,鹰扬关构造带不是新元古代或早古生代蛇绿混杂岩,而是印支晚期陆内构造变形带,不具有板块缝合带的大地构造属性。     

阿尔金山中段清水泉-茫崖蛇绿构造混杂岩带地质特征

清水泉—茫崖蛇绿构造混杂岩带沿阿尔金山南坡分布,呈醒目的“绿色岩带”,其主要由蛇绿岩、蛇绿岩上覆岩系和元古代外来岩片或岩块组成,现多为构造透镜体,蛇绿岩上覆岩系具远洋深海沉积特征;岩石地球化学资料研究证明,蛇绿岩中的玄武岩与洋内岛弧拉斑玄武岩相似;同位素测年结果显示蛇绿岩形成于早古生代,蛇绿岩源自亏损的软流圈地幔,同时有富集地幔物质加入,暗示早古生代研究区曾出现过小洋盆构造环境。     

西藏措勤盆地北缘麦堆构造混杂岩带及变质超基性岩

麦堆构造混杂岩带位于班公湖-怒江结合带南侧、措勤盆地的北缘,由性质不同的各种构造岩片组成,岩片呈近东西向展布,之间多为构造接触,多期变形明显。其中的变质超基性岩岩片宽数米—数十米不等,经历了强烈的蛇纹石化、硅化及碳酸盐化。变质超基性岩虽然化学成分变化很大,但仍具较高的MgO、Cr、Co、Ni含量和m/f比值,属阿尔卑斯型超镁铁质岩,是残余地幔的组成部分。该带变质超基性岩及其伴生硅质岩应属蛇绿岩构造残片,是麦堆构造混杂岩的一部分,其形成与班公湖-怒江特提斯洋向南的俯冲有关,是早中侏罗世弧后或弧间小洋盆环境的产物。     

Geological setting and tectonic subdivision of the Neoproterozoic orogenic belt of Tuludimtu, western Ethiopia

The N–S trending Tuludimtu Belt in the extreme west of Ethiopia has been subdivided into five lithotectonic domains, from east to west, the Didesa, Kemashi, Dengi, Sirkole and Daka domains. The Kemashi, Dengi and Sirkole Domains, forming the core of the belt, contain volcano-sedimentary successions, whilst the Didesa and Daka Domains are gneiss terranes, interpreted to represent the eastern and western forelands of the Tuludimtu Belt. The Kemashi Domain, which consists of an ophiolitic sequence of ultramafic and mafic volcanic and plutonic rocks together with sedimentary rocks of oceanic affinity, is interpreted as oceanic crust and is considered to represent an arc-continent suture zone. The Dengi Domain, composed of mafic to felsic volcanic and plutonic rocks, and a sequence of volcanoclastic, volcanogenic, and carbonate sediments, is interpreted as a volcanic arc. The Sirkole Domain consists of alternating gneiss and volcano-sedimentary sequences, interpreted as an imbricated basement-cover thrust-nappe complex. All the domains are intruded by syn- and post-kinematic Neoproterozoic granitoids. Structural analysis within the Didesa and Daka Domains indicate the presence of pre-Pan African structures, upon which Neoproterozoic deformation has been superimposed. The gneissic rocks of these two domains are regarded as pre-Pan African continental fragments amalgamated to West Gondwana during Neoproterozoic collision events. Unconformably overlying all of the above are a series of tilted but internally undeformed conglomerate–sandstone–shale sequences, regarded as post-accretionary molasse-type deposits, formed during gravitational collapse of the Tuludimtu Belt. The Tuludimtu Belt is interpreted as a collision orogenic belt formed during the assembly of West Gondwana prior to final closure of the Mozambique Ocean.     

皖赣相邻地区双桥山群沉积序列及沉积环境分析

皖赣相邻地区位于江南造山带东段北缘,双桥山群为区内广泛分布的一套厚度巨大低绿片岩相变质的以泥砂质细碎屑岩为主含少量火山岩的复理石建造。综合岩石组合及沉积构造分析,其可能为一套形成于大陆边缘岛弧构造背景下的陆棚斜坡－滨浅海相火山－陆缘碎屑岩建造组合体,具体可划分出次深海-陆棚边缘斜坡相、浅海陆棚相、陆棚斜坡相、陆棚斜坡相-陆棚相4个阶段的沉积相,显示该时期海盆演化已处于萎缩闭合阶段。横涌组和安乐林组中近源间断不完整“鲍马序列”,主要为浊流和部分砂质碎屑流成因,分别形成于古华南洋新元古代陆缘俯冲作用下有限俯冲过程中和俯冲之后洋盆狭缩海退环境;从火山作用随沉积作用协同演化角度对沉积作用与大地构造的关系分析来看,源于洋壳俯冲作用的火山活动可能始于研究区南西。研究结果从沉积地层学角度,为新元古代皖赣相邻地区大地构造演化提供了重要证据。     

大陆碰撞环境沉积岩或变质岩容矿Pb—Zn矿床的发育特点和成矿机制

笔者等通过对不同类型大陆碰撞造山带环境下铅锌矿床进行归纳总结,并进行对比分析,认为在陆陆碰撞的主碰撞阶段,由于板块的汇聚挤压,在碰撞造山带两侧或一侧形成的前陆盆地中发育碳酸盐岩台地,碳酸盐岩未变形或弱变形,来自盆地的卤水在造山带隆升造成的重力势的驱动下,向盆地边缘汇聚,萃取盆地中的成矿元素,在碳酸盐岩的岩溶或断裂中形成MVT型铅锌矿床。在晚碰撞走滑转换阶段,盆地卤水和地层水萃取盆地地层或基底内的成矿物质形成成矿流体,陆陆碰撞持续挤压力使盆地强烈变形,同时在盆地内发育一系列逆冲推覆系统,并驱动成矿流体发生侧向迁移;在挤压后的短暂松弛阶段,成矿流体灌入逆冲断裂及其伴生的次级走滑断裂或张裂隙中形成独具特色的沉积岩容矿铅锌多金属矿床。大陆碰撞造山带挤压至伸展这一应力转换阶段,成矿流体灌入张性构造中,形成类似秦岭碰撞造山带环境产出的脉状铅锌矿床。     

秦岭镇-旬地区微细浸染型锑金矿床成矿条件及其找矿前景分析

镇（安）旬（阳）地区锑金矿化分布，与其区域地质地球化学因素，陆源断陷盆地沉积岩相变化，后期构造作用密切相关，认为镇旬地区为扬子与华北板块边缘对接过渡活动带，形成局部扩张断陷沉积盆地环境。海底同生断裂的发育，使盆地中心局限台盆环境造成陆源物质、内源组份和深部物质的混生，以及为深部含矿热液上升提供通道；在后期脆－韧性剪切变形构造叠加，地下热卤水循环改造作用，形成层控式细脉浸染型锑金矿床。该地区锑金成矿物质来源丰富，沉积构造环境优越，后期控矿构造发育，显示了潜在的细脉浸染型锑金矿床的找矿前景。     

The Quebradagrande Complex: A Lower Cretaceous ensialic marginal basin in the Central Cordillera of the Colombian Andes

The Quebradagrande Complex of Western Colombia consists of volcanic and Albian–Aptian sedimentary rocks of oceanic affinity and outcrops in a highly deformed zone where spatial relationships are difficult to unravel. Berriasian–Aptian sediments that display continental to shallow marine sedimentary facies and mafic and ultramafic plutonic rocks are associated with the Quebradagrande Complex. Geochemically, the basalts and andesites of the Quebradagrande Complex mostly display calc-alkaline affinities, are enriched in large-ion lithophile elements relative to high field strength elements, and thus are typical of volcanic rocks generated in supra-subduction zone mantle wedges. The Quebradagrande Complex parallels the western margin of the Colombian Andes’ Central Cordillera, forming a narrow, discontinuous strip fault-bounded on both sides by metamorphic rocks. The age of the metamorphic rocks east of the Quebradagrande Complex is well established as Neoproterozoic. However, the age of the metamorphics to the west – the Arquía Complex – is poorly constrained; they may have formed during either the Neoproterozoic or Lower Cretaceous. A Neoproterozoic age for the Arquía Complex is favored by both its close proximity to sedimentary rocks mapped as Paleozoic and its intrusion by Triassic plutons. Thus, the Quebradagrande Complex could represent an intracratonic marginal basin produced by spreading-subsidence, where the progressive thinning of the lithosphere generated gradually deeper sedimentary environments, eventually resulting in the generation of oceanic crust. This phenomenon was common in the Peruvian and Chilean Andes during the Uppermost Jurassic and Lower Cretaceous. The marginal basin was trapped during the collision of the Caribbean–Colombian Cretaceous oceanic plateau, which accreted west of the Arquía Complex in the Early Eocene. Differences in the geochemical characteristics of basalts of the oceanic plateau and those of the Quebradagrande Complex indicate these units were generated in very different tectonic settings.     

Geology,geochemistry, and source characteristics of Neoproterozoic arc-related clastic metasediments,Central Eastern Desert,Egypt

The present work concerns two occurrences of Neoproterozoic volcaniclastic metasediments in the Central Eastern Desert (CED) of Egypt namely Alam occurrence and Atalla occurrence. They are mainly composed of bedded successions of feldspathic and feldspathic-lithic metagreywackes, arkosic metagreywackes, metasiltstones, and subordinate metaconglomerates. The rocks have been subjected mainly to various ductile deformational events (D₁ and D₂) due to NE–SW compression and later deformation (D₃). The D₁ deformation is synchronous with greenschist facies metamorphism (M₁). The Alam metagreywackes show oceanic arc tectonic setting. The greywackes have clasts of quartz, feldspar, and metamorphic amphibole after pyroxene and show variable abundances of Cr, Ni, and V. Their provenance components are mainly of evolved felsic and mafic (bimodal) island arcs. The rocks are suggested to be deposited in a localized “intra-arc basin.” The metagreywackes of Atalla show tectonic setting affinity similar to continental sland arc or active continental margin. Their geochemical characteristics reflect the presence of felsic rocks as the main sources, together with minor inputs of intermediate rocks and reworked mineral grains of quartz and feldspar. They are deposited in a localized “retro-arc basins” of an active continental margin. The whole sequences of both Atalla and Alam sediments have been subjected to deformation and contemporaneous regional metamorphism during arc-arc or arc-continent collision. Newproterozoic clastic metasedimentary rocks in the CED appear to have been deposited in arc-related basins, including interarc or back-arc basins, intra-arc basins, and retro-arc basin of active continental margin.     

Tectonometamorphic evolution of the Neoproterozoic Delgo suture zone,Northern Sudan

In the area around Delgo in north-east Sudan a narrow NNE-trending Neoproterozoic belt of low grade volcanosedimentary rocks is fringed by high grade migmatitic basement blocks. The volcanosedimentary sequence is structurally overlain by a rock body of several kilometres length, which is composed of metamorphosed ultramafic and mafic rocks. This sequence is interpreted as an island arc-ophiolite association representing a suture zone.With respect to their degrees of metamorphism and their structural characteristics, the lithological units of the Delgo area are significantly different from the adjacent basement rocks in the east and west. The lithological contacts of the metavolcanic-metasedimentary rocks with the basement rocks are often marked by intermediate-dipping mylonites which are locally overprinted by ductile to brittle-ductile strike-slip faults.The Delgo suture evolved through the subduction-related closure of an oceanic basin and final collision of the island arc with the migmatitic basement blocks on either side of the oceanic basin. Peak metamorphism of deeply buried back-arc basin sequences occurred at around 700 Ma ago. During the collision stage, island arc rocks, passive margin sequences and ophiolitic rocks were thrust to the east and west over the basement blocks, causing limited crustal thickening and a minor isostatic rebound.Lithospheric extension associated with increasing heat flow caused migmatization in the basement between ca. 580 and 540 Ma ago. The development of numerous intermediate-dipping mylonitic shear zones at decreasing temperatures post-dates the migmatization. Lithospheric extension may explain the juxtaposition of rocks which were formed and/or metamorphosed at significantly different crustal levels.     

沉积大地构造相划分与鉴别

沉积大地构造相是反映陆块区、洋区、洋与陆块之间的陆缘区(活动和被动陆缘)形成演变过程中, 在各个演化阶段及其特定的大地构造环境中形成的沉积盆地及其充填序列, 是表达大陆岩石圈板块在离散、汇聚、碰撞、走滑等动力学过程中形成的不同类型沉积盆地及其综合产物, 具有恢复陆块区和造山系形成演化的功能.为从大地构造环境和沉积盆地分析角度系统剖析中国大陆新元古代以来纷繁复杂的大陆增生历程, 根据中国大陆形成演化特点, 提出一套沉积大地构造相(沉积盆地类型)划分方案, 并简述其大地构造环境鉴别标志.该划分方案分4级(相系、大相、相和亚相): 一级为陆块区(含地块)相系和造山系相系.陆块区按构造古地理位置和区域构造应力场进一步划分出二级和三级单元.造山系由弧盆系、叠接带和对接带大相构成, 是岩石圈板块大规模水平运动, 在洋陆转换过程中岛弧增生、弧-弧碰撞、弧-陆碰撞、陆-陆碰撞和陆内俯冲的产物, 常表现为复杂岩石组成、复杂褶皱和断裂构造的巨大山系; 叠接带大相主要由弧-弧碰撞和弧-陆碰撞时, 在陆缘形成的洋-陆转化增生带, 是软碰撞产物; 对接带大相由陆-陆碰撞形成, 是硬碰撞产物.在造山系的弧盆系、叠接带和对接带大相之下, 按洋盆演化-洋陆转化历程所产生的系列构造古地理环境和建造, 进一步划分出洋盆、弧前盆地、弧间盆地、弧后盆地、残余海盆、周缘前陆盆地、弧后前陆盆地等大地构造相单元.