The 41st Tectonic Conference of the Interagency Tectonic Committee, Division of Earth Sciences, Russian Academy of Sciences

The 41st Tectonic Conference on General and Regional Problems of Geotectonics and Geodynamics was held January 29–February 2, 2008 by the Interagency Tectonic Committee, Division of Earth Sciences, Russian Academy of Sciences (RAS). The Geological Institute, RAS, and the Faculty of Geology, Moscow State University (MSU), participated in the organization of the conference.     

Tectonic School of the Geological Institute,Russian Academy of Sciences

The tectonic school of the Geological Institute, Russian Academy of Sciences (GIN RAS), was created in the second half of the 1930s. Its founders were Academicians A.D. Arkhangel’sky and N.S. Shatsky. Three periods are distinguished in the history of the tectonic school. The first period lasted until the 1960s and was based on the geosyncline theory. The Tectonic Map of the USSR and Adjacent Territories (1956) was the acme of the scientific creative activity of this period. The second period corresponded to the 1960s and was characterized by transition to the mobilistic theory. The third period is characterized by the mobilistic theory itself. The concept of tectonic delamination of the lithosphere, which is widely claimed by geological mapping, is a great achievement of this period, which continues to the present day. The concept of involvement of the entire Earth’s mantle down to its core in the tectonosphere is developing currently. The final conclusion is that the work of the tectonic school of the GIN RAS continues in the areas of both regional and general tectonics.     

构造旋回与大地构造年表

构造旋回的划分是大地构造研究的基础之一。但板块学说兴起以来,一些学者基于均变论的哲学思想,却试图抛弃构造旋回的概念。然而,随着时间的推移,地球系统科学的提出,大规模、多学科地学观测,人们已认识到突变与灾变的重要性,认识到渐变与突变相结合的螺旋式向前发展的旋回演化论,才是更全面、更深刻地认识地质规律的有力武器。在大地构造研究中,一些学者常用地层年表,而不用构造旋回。然而,以生物地层学为主要依据的显生宙地层年表与构造旋回和构造岩浆事件并不完全耦合。这是因为,地层年表是在研究地球表生作用,即岩石圈、水圈、大气圈、生物圈之间相互作用的基础上建立的;而构造旋回则是地球内生作用,即壳、幔、核以及壳、幔、核不同层次间多层圈相互作用的历史记录。一些学者在研究大地构造时,只用同位素年龄表示的构造事件,不使用构造旋回。然而,"事件"只是单个现象的呈现,只是构造发展的片段,旋回则阐明过程,反映事物发展中各"事件"(片段)之间的内在联系,反映事物演化的本质。事实上,威尔逊旋回的建立,已为构造旋回和构造事件之间的联系赋予了全新的科学内涵,这也是地质科学发展过程中,正确处理继承与创新关系的一个光辉范例。一些学者由于对全球造山运动是否是同时性的质疑,认为建立全球统一构造年表是不可能的,也是不必要的。可是,地球作为一个整体,其动态活动应该基本上同时的,在受同一地球动力系统控制的一个大区域内,构造运动在各地虽然不是完全同时,但却大致是同时的。北美、欧洲、亚洲加里东、华力西旋回的各次构造运动基本上可以互相对比,就是证明。既然如此,我们就可以按照优先原则,将早古生代的构造旋回称为加里东旋回,将晚古生代的构造旋回称为华力西(海西)旋回。超大陆和超大陆旋回的提出,深化了构造旋回的研究,同时也为建立构造年表开辟了道路。目前已初步提出古元古代哥伦比亚、中元古代罗丁尼亚、新元古代冈瓦纳和显生宙潘吉亚等几个超大陆旋回,这样,我们便可以用超大陆旋回作为构造年表中最大一级的时间单位,每个超大陆旋回又可进一步分为几个旋回,如潘吉亚旋回可分为加里东、华力西两个旋回。我们相信,随着地质学、地球化学、地球物理学研究的深入,随着对固体地球系统和全球地质构造更加深入、全面、系统的观测研究,不久的将来我们将会像建立显生宙地层年表一样,建立起大区域以至全球的构造年表。     

西昆仑于田南部阿羌蛇绿构造混杂岩地质特征及意义

近年的区调工作在西昆仑于田南部阿羌一带新填绘出一套具有蛇绿岩特征的变质橄榄岩、蛇纹岩、变辉长岩、辉绿岩和玄武岩等岩石组合.其中,变质橄榄岩、蛇纹岩具有低SiO2、高MgO、低稀土特征;辉长岩、辉绿岩和玄武岩绝大多数样品岩石化学具有低K2O＜1％,TiO2含量为1.5％等特征;稀土元素及微量元素特征与N-MORB及E-M...     

新疆哈尔里克地区侵入岩浆构造序列确定及构造意义

通过对哈尔里克山地区侵入岩类岩性岩相、岩石地球化学、同位素年代学分析,确定研究区存在奥陶—志留纪(425~460 Ma)、泥盆纪(360~415 Ma)、石炭—二叠纪(270~335 Ma)3期岩浆侵入事件。利用O’Connor标准矿物分类系统,确定泥盆纪发育英云闪长岩-奥长花岗岩-花岗岩(T1T2G2)岩石组合,石炭纪发育石英闪长岩-花岗岩(G1G2)岩石组合。岩石组合极性显示俯冲带在南侧,即研究区南侧存在泥盆—石炭纪向北俯冲的洋盆。认为花岗质岩浆形成于洋壳向陆壳俯冲消减带中,其源岩主体来源于洋壳,并受陆源物质混染。     

伊朗扎格罗斯造山带构造演化与成矿

扎格罗斯造山带是特提斯构造域的重要组成,其内赋存有世界级规模的金属矿产资源。本文综述了扎格罗斯造山带构造格架、物质组成、矿床分布及特征,讨论了该区构造演化与成矿。扎格罗斯造山带由南至北由扎格罗斯褶皱冲断带(ZFTB)、萨南达杰-锡尔詹岩浆变质带(SSZ)、乌尔米耶-达克塔尔火山岩浆带(UDMA)和伊朗中部地块四个构造单元组成。新元古代—早寒武世时,萨南达杰-锡尔詹带和伊朗中部地块位于冈瓦纳大陆北缘,受始特提斯洋盆俯冲影响,边缘发育大陆岩浆弧。晚石炭世—二叠纪萨南达杰-锡尔詹带和伊朗中部地块与冈瓦纳大陆裂解,新特提斯洋盆形成。三叠纪伊朗中部地块与北侧的欧亚大陆汇聚,古特提斯洋盆闭合。侏罗纪—白垩纪新特提斯洋盆向北侧的萨南达杰-锡尔詹带俯冲,形成弧岩浆岩及弧后盆地,其中弧前蛇绿岩中发育铬铁矿床,弧后盆地双峰式火山岩中产有块状硫化物矿床,碳酸盐岩内发育梅迪阿巴德密西西比河谷型超大型铅锌矿床。白垩纪末—新生代初洋壳向萨南达杰-锡尔詹带仰冲,含铬铁矿的蛇绿岩就位。始新世末—渐新世新特提斯洋闭合,南侧的阿拉伯板块与北侧的萨南达杰-锡尔詹带和中伊朗地块所在的欧亚大陆碰撞,在阿拉伯板块前缘形成扎格罗斯褶皱冲断带,在欧亚大陆南缘形成乌尔米耶-达克塔尔火山岩浆带。伴随碰撞,在萨南达杰-锡尔詹带的碳酸盐岩中形成类密西西比河谷型铅锌矿床,中中新世以来扎格罗斯地区进入后碰撞阶段,在乌尔米耶-达克塔尔带内发育了包括萨尔切实梅和松贡超大型矿床在内的众多斑岩型铜矿床。     

Tectonic zoning of Wrangel Island,Arctic region

The Northern, Central, and Southern zones are distinguished by stratigraphic, lithologic, and structural features. The Northern Zone is characterized by Upper Silurian–Lower Devonian sedimentary rocks, which are not known in other zones. They have been deformed into near-meridional folds, which formed under settings of near-latitudinal shortening during the Ellesmere phase of deformation. In the Central Zone, mafic and felsic volcanic rocks that had been earlier referred to Carboniferous are actually Neoproterozoic and probably Early Cambrian in age. Together with folded Devonian–Lower Carboniferous rocks, they make up basement of the Central Zone, which is overlain with a angular unconformity by slightly deformed Lower (?) and Middle Carboniferous–Permian rocks. The Southern Zone comprises the Neoproterozoic metamorphic basement and the Devonian–Triassic sedimentary cover. North-vergent fold–thrust structures were formed at the end of the Early Cretaceous during the Chukchi (Late Kimmerian) deformation phase.     

Tectonic stresses South Bay Mine,Canada

The South Bay copper-zinc-silver orebody, 52 miles east of Red Lake in northwestern Ontario, lies in refolded siliceous volcanic rocks near the close of an Archaean volcanic cycle. The rock mass mechanics events at South Bay mainly happened during the endogenesis and uplift of the earth's crust at the Birch-Uchi greenstone belt. After the uplift the geological history of this region was of little significance for the structure of the ore-body. The paleographic properties of the mineral deposits have been deformed by two phases of geological events; namely, first, Rotational Stress — confined pressure (geometry of torsion structures) and, second, Spherical Stress — compressive pressure (geometry of ellipsoidic structures). And, finally the structure formation in the rock mass induced natural stresses which have components determined by the geometry of the deformations.

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Zusammenfassung Das South-Bay Kupfer-Zink Lager, 80 km östlich des Red Lake im Nordwesten von Ontario gelegen, ist in gefalteten archaischen Vulkaniten von hohem Silikatgehalt eingebettet. Die gesteinsverformenden Bewegungen der South-Bay Region erfolgten hauptsächlich während der Endogenetik und der Anhebung der Erdkruste der Birch-Uchi Greenstone Zone. Nach dieser Anhebung haben die geologischen Ereignisse dieser Region die Struktur des Erzlagers kaum mehr beeinflußt. Die Petrogefüge des Minerallagers zeigen Deformationen während zweier tektonischer Phasen: zuerst freie Verdrehungsspannungen, die Torsionsstrukturen verursachten, gefolgt von allseitigem Druck, der dem Erzlager ellipsoidähnliche Strukturen aufprägte. In den Gesteinen existieren Spannungen, deren Komponenten durch die Geometry der Verformungen bestimmt sind.

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Résumé La mine de Cuivre-Zinc-Argent de South-Bay, située à 80 km à l'est de Red-Lake dans le nort-ouest de l'Ontario, se trouve dans des volcanites, à haute teneur en silicates, plissées au cours de l'Archéen. Les mouvements déformatifs dans la région de South-Bay eurent lieu principalement durant l'endogénese et le soulèvement de la cróute terrestre, le long de la ceinture de roches vertes de Birch-Uchi. Aprèsce soulèvement, les manifestations géologiques dans cette région n'eurent guère d'influence sur la structure du gisement. Les textures pétrographiques du gisement montrent des déformations se rapportant à deux phases tectoniques: d'abord, une rotation engendrant des structures de torsion, et ensuite une compression qui imprima une structure ellipsoÏdale. Il a existé dans la masse rocheuse des tensions dont les composantes ont été déterminées par la géométrie des déformations.

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东南亚及哀牢山红河构造带构造演化的讨论

通过对东南亚和哀牢山红河构造带演化已有模式的分析,在近年来本区海上研究资料的了,结合滇西地质情况,认为东南亚的构造格局是由印度洋、太平洋和欧亚三大构造体系共同作用形成的。６０￣１５ＭａＢＰ,欧亚构造体系分别与太平洋和印度洋构造体系作用在东南亚东、西部形成两个弧后盆地扩张体系。两体系扩张强度和方向的不同,形成转换调节构造带－哀牢山红河构造带。东部较强的扩张作用使扬子板块向北运动,形成哀牢山以东的逆冲     

佳木斯地块构造演化

佳木斯地块位于中亚造山带东段,是我国东北地区一个重要的大地构造单元,古生代以来经历了复杂的多构造体系叠合的演化过程。本文在总结近二十年已报导的相关研究成果基础上,结合笔者近年工作,探讨了佳木斯地块的基底属性和来源,重塑了佳木斯地块西缘碰撞拼贴,以及东缘俯冲-增生的构造演化过程。研究表明,佳木斯地块具有亲冈瓦纳大陆的构造属性,裂离后经历了长距离的北漂。与松辽地块先后两次拼合,首次发生于中志留世(～425Ma),在晚二叠世前后(～250Ma)沿原缝合带位置发生裂解,拉张出新的有限洋盆(牡丹江洋),并于侏罗纪(185～145Ma)与松辽地块沿牡丹江-依兰构造带再次碰撞拼贴,形成了高压变质的黑龙江增生杂岩带。而佳木斯地块东缘受晚石炭世-晚三叠世(305～250Ma)泛大洋的俯冲-增生事件影响,形成了跃进山增生杂岩,随后于中侏罗世-早白垩世(165～128Ma)在古太平洋板块的西向俯冲作用下,形成了饶河增生杂岩。因此,佳木斯地块的构造演化既涉及了晚古生代古亚洲洋构造域的消亡,又经历了中生代古太平洋构造域的叠加与改造,而黑龙江杂岩的形成标志着古太平洋构造体制与古亚洲洋构造体制的转换始于晚三叠世(～210Ma)。     

Metamorphic, Thermal, and Tectonic Evolution of Central New England

A new, detailed tectonic model is presented for the Acadianorogenic belt of central New England (Vermont and New Hampshire)that accounts for a wide range of petrological and structuralobservations. Three belts are considered: the Eastern Vermont,Merrimack, and intervening Bronson Hill belts. Specific observationsin eastern Vermont that are accounted for in the model includethe following. P–T paths are clockwise with maximum pressuresnear the Athens, Chester, and Strafford domes of 8–11kbar, but with maximum pressures decreasing to 3–5 kbarat the boundary with the Bronson Hill belt. Differential exhumationof the Vermont domes relative to the rocks in easternmost Vermontis required by the recorded differences in maximum pressure(5–6 kbar; 15–20 km) and the present-day geographicalseparation (7–10 km). Specific observations in New Hampshirethat are explained include the following. P–T paths inthe Merrimack belt are counter-clockwise with maximum pressuresof 4–5 kbar and are related to high regional heat flowand heat transfer by early Acadian plutons. P–T pathsin the Bronson Hill belt are intimately associated with structuralposition. An early contact metamorphism is evidenced in theSkitchewaug and Fall Mountain nappes near contacts with theearly Acadian Bethlehem gneiss (     

Tectonic evolution of the Iceland region,North Atlantic

Major hypotheses on the formation of the Iceland region are considered. It is noted that plate- and plume-tectonic genesis is the most substantiated hypothesis for this region. Model estimations of the effect of hot plume on the formation of genetically different oceanic ridges are obtained. Computer calculations are performed for the thermal subsidence rate of aseismic ridges (Ninetyeast and Hawaiian-Emperor) in the asthenosphere of the Indian and Pacific oceans. Comparative analysis of the calculated subsidence rates of these ridges with those in the Iceland region (Reykjanes and Kolbeinsey ridges) is performed. The results suggest that the thermophysical processes of formation of the spreading Reykjanes and Kolbeinsey ridges were similar to those of the aseismic Ninetyeast and Hawaiian-Emperor ridges: the genesis of all these ridges is related to the functioning of a hotspot. Analysis of the heat flux distribution in the Iceland Island and Hawaiian Rise areas is carried out. Analysis and numerical calculations indicate that the genesis of Iceland was initially characterized by the plume-tectonic transformation of a continental rather than oceanic lithosphere. The level of geothermal regime near Iceland was two times higher (100 mW/m²) relative to the Hawaiian Rise area (50 mW/m²) because the average lithosphere thickness of the Reykjanes and Kolbeinsey ridges near the Iceland was approximately two times less (40 km) relative to the thickness of the Pacific Plate (80 km) in the Hawaiian area. The main stages of evolution of the Iceland region are based on geological and geothermal data and numerical thermophysical modeling. The Cenozoic tectonic evolution of the region is considered. Paleogeodynamic reconstructions of the North Atlantic in the hotspot system at 60, 50, and 20 Ma are obtained.     

Tectonic geomorphology in parts of Koyna region,Maharashtra

Geomorphic signatures in parts of Koyna region were analysed using satellite images and morphometric indices (stream length gradient index and valley width to height ratio) with limited field checks in key areas for understanding the role of tectonics in this seismically active zone. The Koyna River zone, particularly downstream of Koyna dam wall up to Kajali Nadi, is characterised by incised narrow valleys, steep escarpments and structurally controlled drainage. Presence of knick points at consistent elevations between 825 m to 675 m, steep gradients in an otherwise gradual longitudinal profile and valley width to height ratio less than 1.0 suggest readjustment of the streams along NW-SE and N-S directions. The escarpment slopes in general have en echelon arcuate ridge pattern ～ N45°-N 225° in the western part, and then becomes ～N 10°- N 190° near Donachiwadi, almost orthogonal to the E-W Koyna River. The Donachiwadi fault runs parallel to the escarpment slopes observed near Kodoli. The fluvial system in Koyna thus indicates rejuvenation controlled by basement propagated structures.     

甘肃寨上金矿床构造地球化学特征

寨上金矿位于西秦岭中部岷-礼成矿带西部,所发现的三十余条金矿化脉体的空间分布及其产出特征严格受断裂和褶皱的双重控制,以扎麻树背斜为界分为南北2个成矿带,产出的已知矿脉均严格受控于NWW向断裂.通过对寨上金矿50件构造地球化学样品16种微量元素数据的聚类分析、因子分析,以及对样品元素的组合特征研究,北矿带含矿断裂的元素组合为Au,Bi,Pb,Zn;南矿带的为Au,Sb,Hg,Cu,Zn,Pb,Co,Bi,As.以已知的矿与非矿构造样品为母体,利用多元统计判别分析,建立了断裂含矿性的判别函数,并对未知的17个样品进行判别分析,其判别结果与野外验证一致.     

三江南段勐海布朗山地区早古生代变火成岩岩石成因及其大地构造意义

滇西昌宁-孟连蛇绿混杂岩带保存了晚古生代古特提斯洋演化的记录,近年来在该带内还识别了一套早古生代的SSZ型蛇绿岩以及早古生代洋岛型高压变质岩原岩,证实了带内具有与青藏高原内部龙木措-双湖蛇绿混杂岩带相对应的原特提斯演化的记录.通过对昌宁-孟连蛇绿混杂岩带东南部布朗山地区澜沧岩群中变火山岩和变辉长岩岩石学、岩石地球化学、锆石U-Pb年代学及锆石原位Hf同位素研究,年代学结果显示,变辉长岩年龄为480.2±1.8 Ma,变火山岩年龄分别为465.5±1.2 Ma和472.5±2.9 Ma,代表了变辉长岩和变火山岩原岩形成时代.地球化学特征显示,变辉长岩具有典型的E-MORB微量、稀土元素特征,亏损锆石Hf同位素组成(εHf(t)=12.8～13.6),为洋中脊玄武岩(N-MORB)和洋岛玄武岩(OIB)混合的产物,代表了早古生代原特提斯洋演化的洋壳残片;变火山岩由高镁安山岩和高镁玄武岩组成,具有典型的岛弧岩浆岩亏损高场强元素(Nb、Ta和Ti)的特征,指示它们来源于俯冲交代富集的岩石圈地幔部分熔融,代表的是早古代原特提斯洋俯冲消减过程的产物.因此,昌宁-孟连原特提斯洋在早古生代早期就具有现今太平洋多岛洋的格局,这一研究为深入理解昌宁-孟连蛇绿混杂岩带原-古特提斯发展和演化提供了新的、重要的信息.