内蒙古红山子复式岩体地质时代的厘定及其地质意义

通过岩相学研究和LA-ICP-MS锆石U-Pb测年,对红山子岩体的主要侵入期次和侵入岩形成时代进行了厘定,明确了红山子岩体为复式岩体并探讨了其地质意义。岩相学研究表明,红山子复式岩体由粗粒碱长花岗岩、斑状黑云母花岗岩、细粒黑云母碱长花岗岩和花岗斑岩等组成; LA-ICP-MS锆石U-Pb测年结果显示:粗粒碱长花岗岩的年龄为153. 6±1. 2 Ma,斑状黑云母花岗岩年龄为151. 4±1. 1 Ma,与周边火山盆地赋矿火山岩的年龄一致,属晚侏罗世早期;细粒黑云母碱长花岗岩的年龄为131. 5±1. 8 Ma,花岗斑岩年龄为133. 3±1. 4 Ma,与侵入红山子盆地的花岗斑岩的年龄一致,属早白垩世早期。因此,红山子岩体是由燕山期2个相隔20 Ma的不同期次侵入体组成的复式岩体。研究表明,红山子铀矿床赋存在早白垩世早期花岗斑岩与晚侏罗世火山岩的内、外接触带中,暗示复式岩体早白垩世早期细粒黑云母花岗岩、花岗斑岩与晚侏罗世粗粒碱长花岗岩、斑状黑云母花岗岩的内、外接触带是有利的找矿部位,并得到了铀矿勘查实践的初步证实。     

甘肃北山南带沙枣园复式岩体年代学、地球化学特征及其构造意义

北山南带沙枣园复式岩体由中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩、中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩4个岩相单元组成。LA-ICP-MS锆石U-Pb定年结果表明,中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩侵位于晚二叠世(252.1±1.9Ma、252.2±2.1Ma和248.8±3.5Ma),为海西晚期的产物;而中粗粒黑云母正长花岗岩侵位于早三叠世(246.4±2.0Ma),为印支早期的产物。该花岗质岩石均具有稀土元素的球粒陨石标准化配分曲线呈右倾型,轻重稀土分馏大,轻稀土富集且分异明显,而重稀土亏损且分异不显著特征。中细粒黑云母花岗闪长岩和细粒黑云母石英闪长岩具有较高的SiO₂、Al₂O₃和Na₂O含量,以及较低的MgO含量,强烈富集Sr而亏损Yb和Y,具轻微的铕异常(δEu=0.75～1.16),表现出典型的埃达克岩特征;中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩总体富硅(SiO₂)、富钾(K₂O)、富碱(K     

湖南邓阜仙复式花岗岩体的锆石U-Pb年代学研究

邓阜仙钨矿及其所赋存的邓阜仙复式花岗岩体地处湘赣边境,位于茶陵县北东,距茶陵县城约50km。邓阜仙岩体由三期花岗岩体组成,分别是粗粒斑状黑云母花岗岩、中细粒二云母花岗岩和细粒白云母花岗岩,与石英脉型钨(锡)矿和岩体型铌钽矿有关。本文通过对黑云母花岗岩和二云母花岗岩样品的LA-ICP-MS锆石U-Pb年代学研究,初步探讨湖南邓阜仙复式花岗岩     

芙蓉锡矿田骑田岭花岗岩黑云母矿物化学组成及其对锡成矿的指示意义

芙蓉锡矿田骑田岭复式岩体主要由早阶段角闪石黑云母花岗岩和晚阶段黑云母花岗岩组成.电子探针分析结果表明角闪石黑云母花岗岩中的黑云母属于铁黑云母,黑云母花岗岩中的黑云母属于铁叶云母.相对于黑云母花岗岩,角闪石黑云母花岗岩中黑云母的MgO、TiO2含量偏高,Al2O3含量偏低.矿物化学研究结果显示,角闪石黑云母花岗岩中黑云母的结晶温度、氧逸度(logfO2)分别为680℃～740℃、-16.00～-15.31,黑云母花岗岩中黑云母的结晶温度、氧逸度分别为530℃～650℃、-19.20～-17.50.从角闪石黑云母花岗岩到黑云母花岗岩,岩浆结晶温度和氧逸度逐渐降低.与花岗岩有关的共存流体性质的研究发现,与角闪石黑云母花岗岩共存的热液流体log(fH2O/fHF)fluid,log(fH2O/fHCl)fluid,log(fHF/fHCl)fiuid值分别为4.22～4.39,2.78～3.24,-1.82～-1.73,而与黑云母花岗岩共存的热液流体log(fH2O/fHF)fluid,log(fH2OfHCl)fluid,log(fHF/fHCl)fluid值分别为3.27～3.53,2.85～3.22,-0.75～-0.22,可见与两种岩石类型共存热液流体的性质存在明显差异,且热液中Cl、Sn含量变化与岩浆结晶分异指数呈正相关关系.骑田岭岩体从角闪石黑云母花岗岩到黑云母花岗岩,随着岩浆的演化.岩浆结晶期后分异出的热液流体向富Cl和Sn方向演化.芙蓉锡矿田的成矿流体应主要来源于黑云母花岗岩岩浆结晶期后分异出的岩浆热液.     

藏东怒江板块结合带郭庆复式花岗岩体特征及其成因

根据作者在“三江”地区进行１∶２０万洛隆幅区域地质调查工作中收集的资料,对产出于怒江板块结合带东侧的郭庆复式花岗岩体进行了解体,将岩体划分为燕山早期的黑云母二长花岗岩,燕山晚期的黑云母石英正长岩、黑云母花岗闪长岩三种岩石类型。通过对它们的地质学、岩石学、岩石地球化学特征的研究表明,这三种侵入岩分属陆壳改造Ｓ型花岗岩和壳幔同熔Ⅰ型中酸性岩。燕山早期花岗岩形成于同碰撞造山期,燕山晚期黑云母石英正长岩形成于板块碰撞后的抬升阶段,燕山晚期黑云母花岗闪长岩形成于造山晚期构造环境,是区内板块构造不同演化阶段的产物。郭庆复式岩体的形成与三江地区板块构造演化密切相关     

内蒙古贺根山北乌兰德勒花岗岩体锆石U——Pb 测年、地球化学特征及其构造意义

乌兰德勒岩体为一个由两次岩浆侵入形成的大型复式岩体,主要由黑云母正长花岗岩和黑云母二长花岗岩组成,两种岩石的形成年龄分别为140 ± 2 Ma 和161 ± 1 Ma。黑云母正长花岗岩显示高分异花岗岩的地球化学特征,该类岩石与成矿关系密切。黑云母二长花岗岩表现为低Sr 高Yb 的地球化学特征。地球化学资料显示黑云母二长花岗岩为A 型花岗岩,形成时的构造环境为伸展体制。     

桂东北苗儿山-越城岭东北部界牌钨-铜矿区成矿岩体锆石U-Pb年龄及华南加里东期成矿分析

界牌W-Cu矿床产于苗儿山-越城岭复式岩体东北部斑状黑云母花岗岩与灰岩接触带的矽卡岩中,是苗儿山-越城岭复式岩体矿集区最大的矽卡岩型W-Cu矿床。矿区出露的主要岩体为斑状黑云母花岗岩及后期浅色花岗岩体,矿区外围则大面积出露斑状黑云母二长花岗岩。矿化产于斑状黑云母花岗岩与灰岩接触带矽卡岩,及斑状黑云母花岗岩中灰岩捕虏体矽卡岩化带中。黑云母花岗岩发育花岗岩型钨矿床成矿早期常见的钠长石化、云英岩化及从岩体至外接触带蚀变矿物组合显示形成温度逐渐降低。这些现象表明斑状黑云母花岗岩与矿床具有紧密成因联系。本文获得矿区斑状黑云母花岗岩、斑状黑云母二长花岗岩和浅色花岗岩体锆石LA-ICP-MS U-Pb年龄分别为:422±11 Ma,428±7 Ma,410±7 Ma,表明界牌W-矿床及区内主要岩体均形成于加里东期。本文的同位素年龄及前人报道的苗儿山-越城岭矿集区和华南加里东期与花岗岩有关矿床同位素年龄表明苗儿山-越城岭矿集区W-Mo-Cu矿床成矿主要发生在加里东期和印支期,U矿成矿主要发生在燕山期,华南在加里东期发生了分布广泛、成矿元素组合多样的与花岗岩有关的成矿事件,有很好的找矿前景,今后应加强华南加里东期矿床的找矿工作。     

湖南沩山岩体多期云母的Rb-Sr同位素年龄和矿物化学组成及其成岩成矿指示意义

华南分布了大量的印支期-燕山期复式花岗岩体,其成岩及相关成矿过程一直存有争议。本文选择湖南典型的花岗质复式大岩基——沩山岩体为例,通过细致研究其中多期云母的单颗粒Rb-Sr年龄及地球化学组成,探讨了它们对相关成岩成矿过程的指示意义。单颗粒云母Rb-Sr等时线定年结果显示,沩山复式花岗岩主体唐市黑云母二长花岗岩中黑云母结晶年龄为221.9±5.8Ma(MSWD=3.8),主体边部的新浦高演化花岗岩中黑云母结晶年龄为227.0±13Ma(MSWD=1.6),主体内部的巷子口二云母花岗岩中白云母结晶年龄为210.1±3.3Ma(MSWD=0.21)。电子探针主量元素及激光探针LA-ICM-MS微量元素测定结果表明,沩山复式花岗岩中黑云母或白云母的成分存在明显差异,由此指示该岩体多期岩浆的温度、氧逸度以及源岩浆成分的差异。本文研究还表明,巷子口二云母花岗岩中白云母属于次生白云母,不能用来限定岩浆源区深度及岩石成因。鉴于多期云母的成分分异趋势及指示意义,我们认为沩山复式花岗岩多期岩浆具有同源关系,均来自于同一深部大岩浆房,是在不同时期不同构造背景下经历分离结晶和/或同化混染作用侵位而成。其中,印支晚期及之后的二云母花岗岩可能最具铀矿找矿前景。     

赣南珠兰埠岩体锆石U-Pb年代学研究及其含矿性评价

珠兰埠岩体是南岭地区大面积出露的岩体之一,也是缺少精确年龄数据的复杂岩体之一,在以往工作中被认为是燕山期早期岩体,此后相关研究较少,由于时代和方法的限制未见确切的同位素年龄数据发表。本文采用LA-(MC)-ICPMS锆石U-Pb法对珠兰埠复式岩体的粗粒斑状黑云母花岗岩、中细粒含斑黑云母花岗岩进行同位素年代学研究,探讨其成矿可能性。获得粗粒斑状黑云母花岗岩、中细粒含斑黑云母花岗岩等时线年龄分别为228.7±2.0 Ma和231.0±1.2 Ma,表明珠兰埠复式花岗岩体主体形成于印支期,而不是前人认为的燕山早期,由此修正了岩体成岩时代,同时结合珠兰埠岩体的地球化学特征与印支期花岗岩的成矿特点,较好印证了目前在该岩体及其周边,并未发现钨矿床的现象。本研究成果为赣南地区花岗岩研究提供了新的实例。     

湖南瑶岗仙复式岩体的年代学特征

瑶岗仙复式岩体位于湖南省东南部,属于南岭花岗岩北带,它是瑶岗仙钨矿床的成矿母岩.根据野外接触关系和岩石学特征将瑶岗仙复式岩体划分为三个期次的侵入岩,即第一期的粗粒黑云母花岗岩、第二期的细粒斑状花岗岩和第三期的石英斑岩.对瑶岗仙复式岩体进行锆石SHRIMP定年,分别得到三期岩体的年龄为155.4+2.2Ma(MSWD=0...     

Unity of the national and the international in the socio-cultural development of the peoples of the USSR

International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen.     

Report of the restudy of the defined global stratotype of the base of the Silurian System

The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.     

Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth

It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T ₃ = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″.     

The Tendencies of the Development of the Mineral-Resources Sector at the Turn of the Century

Important tendencies in development of the world mineral-resources sector at the beginning of the 21st century were an increase in production and consumption of mineral materials differentiated by types of metals and nonmetallic mineral raw materials, by countries and regions, as well as the concentration of the production of mineral raw materials in a small number of countries, and a reduction in industrial reserves of minerals in the world economy, even at the current stage of their extraction. These tendencies should be taken into account in working out a strategy for development of the Russian mineral raw-material base.     

Causes of the famine among the rural population of the Sahelian zone of the Sudan

Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators.     

东濮凹陷北部沙河街组三段中亚段沉积环境分析

东濮凹陷北部沙三中亚段广泛发育盐岩和烃源岩,这两个看似不能共存的物质却在这里互层共生。该时期研究区沉积特征为多盐韵律与多层烃源岩互层共生、连续沉积,单个盐韵律厚度从几米到十几米,烃源岩有机质丰度高、类型好。平面上,两者在湖盆沉积沉降中心共生;垂向上,高有机质丰度、好干酪根类型与高盐度地层具有较好的对应关系。因而成为恢复古气候和古环境的重要研究对象。通过岩石学、古生物学以及Sr/Ba、B/Ga、(V+Ni+Mn)、Fe/Mn、Sr/Cu、Mg/Ca、V/(V+Ni)、稀土元素含量和氯同位素等方法对凹陷北部沙三中亚段的沉积环境进行研究。结果表明,凹陷北部沙三中亚段为深水沉积的还原环境,古盐度较高,达到半咸水-咸水沉积;微量元素和孢粉化石特征表明研究区沙三中亚段为温暖潮湿的环境。     

On the consistency of proposed models for the Pyrenees with the structure of the eastern parts of the belt

The structure of the eastern Pyrenees consists mainly of south-directed thrusts involving basement and cover rocks. An antiformal stack developed by the piling up of basement thrust sheets which outcrop in the Axial zone. These structures account for a thin-skinned thrust model rather than a vertical fault model in which the Axial zone would be essentially autochthonous, and the North-Pyrenean fault the axial plane of a fan thrust system. New data from the Eastern Pyrenees and the thin-skinned model suggest that(1) the structure east of the Pedraforca nappe is similar to that of the Central Pyrenees; (2) the cover rocks of the South-Pyrenean units and of the Axial zone-after restoration—built up a northwards-thickening prism consistent with the existence of a unique Pyrenean sedimentary basin during Mesozoic time; (3) the Axial zone is only a complex antiformal stack developed as a part of South-Pyrenean system related to the Paleogene thrusting-tectonics. The Axial zone palaeogeographic area had no special meaning during Mesozoic time.     

The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads

In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning.