康滇地轴新元古代成矿作用与罗迪尼亚超大陆

康滇地轴在元古代时期形成了大量的金属矿床,研究表明,该时期的金属矿床形成与晋宁运动密切相关。近几年许多研究数据显示,康滇地轴在元古代地层中所形成的铜、铁、金和铀矿床大多集中在700～900Ma之间,与罗迪尼亚超大陆事件发生的时间一致。该时期的碰撞构造环境、花岗岩侵入以及沉积盆地的形成都与陆内板块俯冲作用和伸展作用关系密切。试图从同位素地质年代学、沉积一构造环境方面,探讨该时期的金属成矿作用对板块构造地质事件的响应,并探讨铀成矿作用与板块运动的关系。     

建立康滇地轴区中—晚元古代层型剖面的雏议

根据国际、国内新近作出的对元古宙年代地层单位划分方案,本文对康滇地轴区完好发育的元古宙地层,在已取得的研究程度的基础上,认为只要对昆阳群(会理群)和震旦系的层序、时代、顶底及造成不整合界面的几个地质事件取得共识,就有可能建立我国南方活动地槽—稳定地台区中-晚元古代时间地层单位的框架性层型剖面。本文综合已取得共识的若干重要方面和存在争议的问题,分析分歧的原因和解决问题的途径,根据地层接触关系、区域地层对比、底辟、叠层石、微古植物、同位素年龄、古地磁和放射性元素丰度对比等方面的成果,来建立原始沉积的地层柱和反映地壳运动的重大地质事件,提出年代地层表及纪的命名的建议。     

再论建立康滇地轴区中晚元古代层型剖面问题

在《建立康滇地轴区中—晚元古代层型剖面的雏议》一文（《云南地质》,１９９３）中,笔者根据国内外对元古宙年代地层单位的划分方案,结合康滇地轴区中元古代和晚元古代的昆阳群（会理群,不含河口组）及震旦系发育完好,顶底齐全,沉积旋回和地质事件明显,叠层石、微...     

康滇地轴元古代重大地质事件与拉拉IOCG矿床成矿响应

有关IOCG最新研究成果建议,将IOCG矿床限定于资源量大于1 Mt的大型/超大型矿床。对世界上已知的大型/超大型IOCG矿床的成矿背景和成矿作用进行分析对比,发现前寒纪大型/超大型IOCG矿床均位于前寒纪超大陆的边缘、形成于非造山期,与壳幔相互作用有关,与板底垫托、地幔柱等相关的重大地质事件关系密切。通过对康滇地轴元古代地质体岩石/矿物的同位素年龄数据分析研究,同时对拉拉IOCG矿床成矿特征及同位素测龄分析,认为扬子地台西缘康滇地轴存在早元古代早期(2 486～1 884 Ma BP)古陆壳,是Kenorland超大陆的一部分。在中元古代发育了康滇陆缘裂谷(1 725～1 466 Ma BP),与Columbia超大陆非造山期同时。新元古代的晋宁运动使该裂谷产物变质,及形成康定杂岩,成为康滇地轴的上层结晶基底(1 100～721 Ma BP)。其是Rodinia超大陆的拼贴与裂解事件的响应。拉拉矿床具有2期成矿作用。第一期火山喷发成矿期(1 712～1 680 Ma BP),是康滇裂谷事件的产物。第二期变质热液成矿期主成矿阶段(1 000～900Ma BP),是Rodinia超大陆的拼贴作用的响应。康滇地轴元代地层中具有形成IOCG矿床的巨大潜力。     

浅析康滇地轴构造运动与铀成矿的关系

本文根据现有资料,分析康滇地轴的区域地质构造运动及其演化与铀成矿的关系,提出晋宁期是康滇地轴第一次铀成矿期（960—1006Ma）。     

康滇地轴南段构造—岩浆活动与铀矿化关系探讨

康滇地轴南段构造－岩浆活动与铀矿化关系探讨李余华（核工业西南地质局二○九大队）１前言近年来,云南前寒武系地质工作取得了许多新成就,特别是对康滇地轴的研究更为引人注目,在放射性地质、同位素地球化学、地质年代学和地壳演化等领域都取得了突破性进展。通过近几...     

论康滇地轴的深部构造

最近通过对康定-红河南北向构造带的研究,作者认为它不是扬子地台的边缘隆起带,而是特提斯型碰撞构造带。该带地壳上地幔构造可分三层。最上层为脆性上地壳,其主要运动形式为逆掩叠瓦。第二层为塑性下地壳及部分上地幔,表现为挤压缩短。其速度结构与青藏地区相似。认为是从青藏挤过来的异地体。第三层为上地幔。从岩石圈厚度来判断,应属扬子地台。     

对“康滇地轴”轴成矿环境的初步探讨

本文是根据“康滇地轴”的地壳演化历史和铀的地球化学特性来探讨“康滇地轴”的铀成矿环境,认为“康滇地轴”既有有利于铀成矿的地质环境和条件,又有不利的因素,因此,应加强基础地质研究,以各种成矿理论为指导选择有利地段,对“康滇地轴”进行第2轮找矿。     

华北陆块对Rodinia超大陆的响应及其特征

研究揭示华北陆块1300-1000Ma和800-650Ma都存在比较弱的岩浆-变质事件，它们可能对应于华南陆块的碰撞（四堡运动）和裂解事件。华北陆块的四堡期蛇绿混杂岩可能只见于新元古代秦岭造山带中。秦岭造山带北缘识别出了一些花岗质分清入体，它们具有碰撞或碰撞后花岗岩的特征。华北陆块北缘的火山沉积岩生活费不具有离散边界杂岩的特征，它们可能揭示了大陆边缘或者大陆伸展过程。华北陆块与800-650Ma事件相关的岩石主要为来自富集地幔的基性岩墙和来自陆内裂谷的沉积岩，它们很可能与Rodinia裂解有关。沉积学和古生物学特征表明元古宙华北陆块不同华南陆块，而与西伯利亚陆块相似。据此可以认为华北陆块是Rodinia超大陆的一部分，它位于超大陆的边缘，可以不与华南陆块紧邻，而与西伯利亚陆地较近。     

扬子板块北缘花山群沉积时代及其对Rodinia超大陆裂解的制约

出露于扬子板块北缘大洪山地区的花山群自下而上由一套以砾岩为主的粗碎屑沉积和一套以砂质板岩为主的细碎屑沉积组成,伴随有拉斑玄武质岩浆活动。花山群整体变质程度不高,形成构造环境复杂,对其构造属性及其与区内所谓的花山"蛇绿混杂岩"的时空关系一直存有争议,它们对新元古代Rodinia超大陆在扬子板块北缘的汇聚-裂解响应具有重要的制约意义。笔者在花山群六房咀组下部细砂岩中采集玄武质熔结凝灰岩夹层样品1件,碎屑岩样品2件,在上覆地层南华系莲沱组采集碎屑岩样品1件;对玄武质熔结凝灰岩进行了SHRIMP锆石U-Pb同位素测年,对碎屑岩样品进行了LA-MC-ICPMS锆石U-Pb同位素测年。获得玄武质熔结凝灰岩锆石U-Pb年龄814.7±7.3 Ma;花山群的碎屑锆石U-Pb年龄谱存在三个明显的峰值:~900 Ma、~2050Ma和~2650 Ma,最显著峰值为~2650 Ma,上覆莲沱组碎屑岩年龄谱的三个峰值为:~900 Ma、~2050 Ma和~2500 Ma,最显著峰值为~2050Ma,三件碎屑岩样品均与扬子板块的碎屑锆石U-Pb年龄统计峰值一致。花山群的碎屑源区可能包括下伏中元古代打鼓石群、太古宙鱼洞子杂岩以及崆岭杂岩。结合前人年代学研究资料和区域构造成果分析,花山群沉积时代应为820~815Ma,形成于伸展构造背景,与花山"蛇绿混杂岩"不是同期同构造背景的产物;花山"蛇绿混杂岩"与花山群沉积建造依次反映了扬子板块北缘由挤压构造背景向伸展构造背景的转换过程。花山群中的碎屑沉积物与基性火山岩、火山碎屑岩属于裂解背景下形成的同时代沉积-火山建造;结合前人在扬子板块周缘发现的大量约820 Ma酸性—基性岩浆活动记录以及同时代(820~800 Ma)的沉积地层,推测花山群形成于Rodinia超大陆裂解背景之下,与超级地幔柱活动有关。     

Emanation-Sedimentary Metallogenic Series and Models of the Proterozoic Rift in the Kangdian Axis

The Kangdian axis basement can be divided into two tectonic layers. The lower tectonic layer is the crystalline basement which is made up of the Archaean Dibadu Formation and early Proterozoic Dahongshan Group. The former is a kata-metamorphic basic volcano-sedimentary formation of the old geosyncline (old continental nucleus), and the latter is a medium-grade metamorphosed alkali-rich basic volcanic (emanation)-sedimentary formation of the Yuanjiang-Dahongshan marginal rift. They are in disconformable contact. The upper tectonic layer is the folded basement, and made up of the middle-late Proterozoic Kunyang Group. It is the result of Dongchuan-Yuanjiang intercontinental rifting with discordant contract with the underlying and overlying strata. Along with the evolution of Proterozoic from early to late, four types of emanation-sedimentary deposits in the Kangdian axis rift were formed in turn: (1) emanation-sedimentary iron-copper-gold deposits related to basic volcanic rocks in the Yuanmou-Dahongshan     

Assembly and Breakup of Rodinia (Some results of IGCP project 440)

The principal results of project 440 “Assembly and Breakup of Rodinia” of the International Geological Correlation Programme (IGCP) are reviewed in this work. A map of that supercontinent compiled using geological and paleomagnetic data describes global paleogeography 900 Ma ago. The assembly of Rodinia, which comprised most of Precambrian continental blocks, lasted ca. 400 m.y. (from 1300 to 900 Ma). Its breakup presumably triggered by mantle superplume took place between 830 and 650 Ma. The correlation between tectonic events in different continental blocks is considered. Some problems concerning the Rodinia reconstruction and history, e.g., the slow growth of juvenile crust and effects of mantle-plume events during the amalgamation period and of glaciations at the breakup time, are discussed. The latter caused changes in the biosphere and climate, whereas postglacial periods stimulated progress in biota evolution.     

The Paranapanema Lithospheric Block: Its Importance for Proterozoic (Rodinia, Gondwana) Supercontinent Theories.

This work considers the tectonics of the southeastern portion of the South American Platform based on new geological and geophysical grounds. For the last decade, only three (Amazonic, São Francisco and La Plata) of the many other cratonic blocks have been attributed/remarked to the South America portion for most of the usual Rodinia reconstitutions. The possibility of the existence of other blocks has rarely been mentioned. The postulation of the presence of a considerable Paleoproterozoic (pre-Brasiliano) fragment as part of Paraná Basin basement is highly probable. In order to infer the basement structure of Paraná Basin, previous to the sedimentation process, an isostatic modeling was applied to a large-scale gravity survey looking to correlate topographic and gravity anomalies caused by sub-surface loads. The Bouguer anomaly obtained from the gravity survey represents the crustal contribution of crystalline basement, in addition to the sedimentary and volcanic layers of the basin. Following the isostatic modeling and the basin load stripping, the residual anomaly allows observing similarities between the basement gravity signature and outcropping units. Besides, the stress pattern of the two earlier events obtained through the back stripping analysis presents a geographically coincident maximum, and a new E-SE high emerging for the second event, suggesting continuous change of the stress field as a precursor for South American plate rotation. The evident correlation between gravity highs and main attenuation suggests the presence of some pre-existing suture zones. The weakened lithosphere during Ordovician and Carboniferous provided the magma conduits to form in Early Cretaceous tectonic stress field pattern. The resultant mosaic of gravity blocks and the main faults site give support to the presence of this cratonic Proterozoic unit, here on referred to as the Paranapanema Block, which had been neglected in most of the models reported for the reconstruction of Gondwana (and Rodinia).     

LA-ICPMS U-Pb Ages of Zircon from Metaleucosomes, Olongbuluke Microcontinent, North Qaidam, and Implications on the Response to the Global Rodinia Supercontinent Assembly Event in NW China

INTRODUCTION The Olongbuluke microcontinent , which wasdisintegratedfromthe northern margin of the Qaidamblock (Lu,2002) ,is composed of a two-fold base-ment with cover strata . The lower basement is themedium- to high-grade Delingha complex and theDakendaban Group, and the upper is the low-gradeWandonggou Group. The Wandonggou Group of theupper basement experienced a Late Mesoproterozoicmetamorphic event (see Yu et al .,1994) ,consistentwith the early isotopic geochronological respo…     

Palaeomagnetic constraints on the position of the Kalahari craton in Rodinia

A comparison of late Mesoproterozoic palaeomagnetic poles from the Kalahari craton and its correlative Grunehogna craton in East Antarctica shows that the Kalahari–Grunehogna craton straddled the palaeo-Equator and underwent no azimuthal rotation between ca. 1130 and 1105 Ma. Comparison of the Kalahari palaeopoles with the Laurentia APWP between 1130 and 1000 Ma shows that there was a latitudinal separation of 30±14° between Kalahari and the Llano–West Texas margin of Laurentia at ca. 1105 Ma. The Kalahari craton could have converged with southwestern Laurentia between 1060 and 1030 Ma to become part of Rodinia by 1000 Ma. In Rodinia, the Kalahari craton lay near East Antarctica with the Namaqua–Natal orogenic belt facing outboard and away from the Laurentian craton.     

A Rifting Story of South China, With Particular Reference to Rodinia Breakup

A RIFTING STORY OF SOUTH CHINA, WITH PARTICULAR REFERENCE TO RODINIA BREAKUP