新疆库车新生代前陆褶皱冲断带的变形特征、时代和机制

库车前陆褶皱冲断带自北向南可分为基底冲断带、箱状背斜带、梳状背斜带和挠曲褶皱带,东西方向上可分为西段、中段和东段。本文分段叙述了各变形带的变形特征,指出东段箱状背斜带不发育,秋里塔格山脉(构造带)东延未进入东段,因而总体看自西向东变形强度减弱,地形上趋于夷平。该冲断带的形成经历了两次重大的冲断活动,分别发生在中新世和早(-中)更新世;相应地,该带可分为南、北两个"盆""山"亚系统,两者在地层记录、变形期次和变形机制上尚有若干差异。库车前陆褶皱冲断带的发育,除了受南天山的冲断和向南扩展引起的近南北向挤压应力场控制外,还受到基底断裂在新生代的活化和膏盐层底辟的制约,前者以近北西向的构造变换带及其共轭发育的近北东向断层最为重要,后者既控制了秋里塔格山脉的形成(主要受垂直的挤压应力场作用),也在库车前陆褶皱冲断带东西方向的变形分段中起了重要作用。文章还讨论了变形与地貌发育的关系和在油气勘探中的指导意义。     

赣东北“金三角区”成矿带的划分及成矿模式

在对赣东北"金三角区"成矿带划分的基础上,分析总结了各重点成矿带的成矿模式.由于区内不同构造单元基底性质、深部构造和壳幔结构方面的差异,产生各地质单元中不同的矿床集结,如东乡-德兴成矿带以Cu,Au矿床为主,Pb,Zn,Ag矿床为次;信江南侧成矿带以Cu,Pb,Zn,Ag多金属矿床产出为主,Au矿床次之;而灵山-怀玉山成矿带则以Nb,Ta等稀有金属矿床为特点,其次为Pb,Zn,W,Sn等矿床.     

Diapirism synchronous with regional deformation and gold mineralisation,a new concept for granitoid emplacement in the Southern Cross Province,Western Australia

The Southern Cross Province in the Archean Yilgarn Block of Western Australia comprises large dome-shaped granitoid bodies surrounded by narrow greenstone belts. Determination of the emplacement mechanism of these domes is fundamental for understanding the tectonic history of this region. Many structures in the greenstone belts show trends which reflect their tectonic relationships with the granitoid domes. Some of these structures host large gold occurrences. The domes have concentric foliation patterns, both within the granitoids themselves, and in the neighbouring greenstone belts. The smaller domes only have radial mineral lineation patterns in their wall rocks, but the largest dome, the Ghooli Dome, has also a tangential pattern. The prevailing gentle dip of the foliation in the centre of this dome and the abundance of greenstone xenoliths suggest that the present exposures are close to its roof. Geothermometry and geobarometry on mineral assemblages in the Ghooli granitoid and its xenoliths show that its crystallisation temperature was just above 700 °C at a relatively high pressure of 4.3 to 6.2 kbar. These P-T conditions are higher than those inferred for peak metamorphism in the greenstones. Therefore, this granitoid must have been emplaced initially at crustal levels deeper than the maximum burial of the greenstones which flank the dome. The Ghooli Dome has a SHRIMP U-Pb zircon age of 2691 ± 7 Ma. Diapiric rise of the granitoid plutons taking place in a regional compressive tectonic regime is considered to be the most likely mechanism for the final emplacement of these bodies into their host rock at about 2636–2620 Ma. This concept is preferred over the alternatives because it best reconciles the calculated P-T data, the observed structural patterns, the presence of pegmatites and aplites in the host rock, and the orientation of the mineral-bearing structures.     

华中榴辉岩及其成因的若干问题

榴辉岩是华中高压变质带的特征岩类之一。根据其共生的矿物组合可划分出四类榴辉岩:角闪(蓝闪)榴辉岩,蓝晶石榴辉岩、柯石英榴辉岩和石英榴辉岩。其中蓝闪榴辉岩主要分布于团麻断裂以西地区;柯石英榴辉岩均出露于团麻断裂以东地区。根据矿物对地质温压计和变质矿物组合估测,西部地段榴辉岩的形成条件为p=1.1～1.5GPa,t=540～600℃,中东部地段榴辉岩为p≥2.5GPa,t=700～800℃。 根据岩石组合、矿物组合和构造环境分析,绝大多数(如果不是全部的话)榴辉岩与围岩经历了相同的高压—超高压变质作用,是同一构造运动旋回中不同构造部位的变质产物。蓝闪榴辉岩和柯石英榴辉岩的地质环境和退变质作用特征具有重要的大地构造意义。     

造山带与前陆盆地结构构造及动力学研究思路和进展

运用大量的研究成果，综合分析了大陆岩石圈结构和动力学特征，在此基础上探讨了造山带研究的思路和方法，总结了造山带结构、构造及其形成演化研究的新进展。指出前陆盆地的研究是深入研究造山带的关键，前陆盆地是前陆冲断作用引起岩石圈挠曲变形的结果，阐述了前陆盆地形成机制的研究进展     

Transitional environments of the lower Maastrichtian South-Pyrenean Basin (Catalonia,Spain): The Fumanya Member tidal flat

Sedimentological, palaeontological and geochemical data provide detailed evidence of a marine-to-lagoon environmental succession around the Campanian-Maastrichtian boundary in the Ibero-Armorican domain. This regression is recorded by the succession of several environments of the south-central Pyrenees basin: open marine mixed shelf, marine restricted mixed shelf (both rudist-rich), tidal flat, lagoon and fluvial dominated. The tidal flat setting belongs to the Fumanya Member here described, which is the base of the Posa and Massana formations (Tremp Group). The Fumanya Member is 5 m thick, is built up of marly limestones and was an elongated tidal mudflat (100 km long, 25 km wide) developed in a foreland trough and was separated from the Atlantic Ocean by an island-barrier system. In the lagoon environment, marginal marine waters and continental fresh waters alternated as documented by geochemistry and fossil molluscs. The Fumanya Member is a dinosaur megatracksite, reporting the roaming activity only of sauropods in tidal flats, a likely secure area against predators. Feeding activity of these herbivores took place in the lagoonal-lacustrine environments of the Posa Formation above the Fumanya Member.     

Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine,USA

We report the ages of cleavage development in a normally intractable lower greenschist facies slate belt, the Central Maine-Aroostook-Matapedia belt in east-central Maine. We have attacked this problem by identifying the minimum ages of muscovite in a regional Acadian cleavage (S₁) and in a local ductile fault zone cleavage (S₂) using ⁴⁰Ar/³⁹Ar geochronology and the ages of crosscutting plutons. Our success stems from the regional low-grade metamorphism of the rocks in which each crystallization event preserves a⁴⁰Ar/³⁹Ar crystallization age and not a cooling age. Evidence for recrystallization via a pressure solution mechanism comes from truncations of detrital, authigenic, and in some rocks S₁ muscovite and chlorite grains by new cleavage-forming muscovite and chlorite grains. Low-blank furnace age spectra from meta-arkosic and slaty rocks climb from moderate temperature Devonian age-steps dominated by cleavage-forming muscovite to Ordovician age-steps dominated by a detrital muscovite component. S₁- and S₂-cleaved rocks were hornfelsed by granitoids of ∼407 and 377 Ma, respectively. The combination of these minimum ages with the maximum metamorphic crystallization ages establishes narrow constraints on the timing of these two cleavage-forming events, ∼410 Ma (S₁) and ∼380 Ma (S₂). These two events coincide in time with a change in the plate convergence kinematics from the arrival of the Avalon terrane (Acadian orogeny), to a right-lateral transpression arrival of the Meguma terrane in the Neoacadian orogeny.     

中蒙边界地区成矿区带划分

中蒙边界地区成矿区带划分是近年来该区成矿规律研究中的重要科学问题之一。以板块构造-地球动力学理论为指导,在中蒙合作完成的该区1∶100万建造-构造图和成矿规律图的基础上,对中蒙边界地区成矿区带进行了统一厘定和划分。该区Ⅰ级成矿域隶属于古亚洲成矿域和滨太平洋成矿域。古亚洲成矿域可划分为阿尔泰、准噶尔-南蒙古和塔里木3个成矿省、12个成矿带和21个成矿亚带。滨太平洋成矿域划分出大兴安岭和华北陆块2个成矿省、4个成矿带和15个成矿亚带。研究提出,蒙古的欧玉陶勒盖-查干苏布尔嘎大型-超大型斑岩型矿床成矿亚带向西与中国的东天山-北山成矿亚带相连,为该区寻找同类型斑岩型矿床指明了方向。     

褶皱冲断带构造砂箱物理模型研究进展

地壳浅层次褶皱冲断带普遍受控于具耦合互馈特性的多种机制或边界条件,从而具有长期的构造演化过程和复杂的构造特征。自19世纪初以来,基于地质构造过程自相似性和"无理有效性"的砂箱物理模型,为解译褶皱冲断带的演化过程及其动力学机制等提供了独立有效的手段。本文主要基于国内外地壳浅表褶皱冲断带构造变形过程为研究对象的构造砂箱物理模型研究结果与进展进行综述性报道,以期为同行提供参考与借鉴。基于与地壳浅表地层具相似流变学特性的砂箱物理模拟研究,揭示出地壳浅层次构造变形过程普遍自相似性生长过程,符合库伦临界楔理论。褶皱冲断带挤压变形过程中,基底特性(基底几何学、有效摩擦角、基底耦合性和流体超压)、变形物质特性(空间几何学、能干层、流变学和非均一性)、动力学机制(砂箱几何边界、汇聚速率和汇聚方向)、浅表作用(剥蚀和沉降)等对于地壳浅表构造变形过程具有明显的控制作用。构造砂箱物理模型在解译不同构造变形过程与机制的研究中发挥着越来越突出的作用。     

中国锗矿成矿规律概要

锗是一种重要的稀散元素,在半导体、光电器件和其他工业领域扮演着重要角色。文章通过对已有研究成果的系统梳理,初步总结了中国锗矿的资源特征和成矿规律,并建立了成矿谱系。研究认为,中国主要的锗矿床和富锗矿床可被划分为煤层型锗矿、碳酸盐岩容矿型锗矿、岩浆热液型富锗矿床、火山岩型富锗矿床和沉积型矿产中的潜在锗资源5种类型,较为重要的类型包括煤层型和碳酸盐岩容矿型。锗成矿作用时间跨度较大,从元古代到新生代均有矿床形成,但相对集中于中生代。空间上,不同类型锗矿的分布各具特点,煤层型锗矿主要分布于大兴安岭和西南三江地区;碳酸盐岩容矿型锗矿主要分布于川滇黔地区;岩浆热液型富锗矿床、火山岩型富锗矿床主要分布于长江中下游地区和南岭地区。根据锗矿的时空分布特征及其与构造演化的关系,文章共划分出15个锗成矿带,建立了21个与锗成矿作用有关的成矿系列。