东天山红柳河地区晚加里东期花岗岩类岩石锆石U—Pb年龄及其地质意义

本文对东天山红柳河地区 2个花岗岩类岩体进行了年代学和元素 同位素地球化学研究。锆石U Pb年龄表明 ,红柳河北闪长岩体 ( 4 41.4± 1.6Ma)和前进工区花岗岩体 ( 4 40 .9± 3 .1Ma)形成于晚加里东期。这两个花岗岩类岩体的形成不仅证实了东天山存在着晚加里东期岩浆活动 ,而且其形成与哈萨克斯坦 准噶尔大洋板块向塔里木板块俯冲密切相关。     

湖北省随州杨家棚地区辉长岩Rb-Sr同位素年龄

对湖北省随州地区组成花山蛇绿混杂岩的杨家棚MORB型辉长岩进行了RbSr同位素分析,其矿物(辉石、斜长石)等时线年龄为435±49(2σ)Ma,ISr为0.70516±28(2σ),与该地区出露的三里岗二长花岗岩的RbSr等时线年龄(422Ma)在误差范围内是一致的;反映了该地区在加里东期曾受到强烈地质事件的作用,并进一步表明花山洋盆可能是一个形成年龄较老的洋盆,以前有关花山洋盆存在时限(海西印支期)的推测在这里没有得到确证。     

祁连山东南段加里东造山期构造变形年代的精确限定及其意义

祁连山东南段呈北西-南东向展布着加里东期中祁连造山带和拉脊山造山带, 其基底为前加里东变质岩系, 在该变质结晶基底岩系中发育着菱形网格状韧性剪切带, 共轭韧性剪切带面对缩短方向的夹角为104°~114°, 其最大主应力方位为SW210°左右.在中祁连地块金沙峡和化隆地块科却两处韧性剪切带中的糜棱岩化岩石, 获取变质矿物白云母40Ar-39Ar坪年龄分别为(405.1±2.4) Ma和(418.3±2.8) Ma.这一年代学结果不仅确定了加里东基底变质岩系中韧性剪切带是加里东造山作用过程中形成, 更重要的是通过对基底韧性剪切带中变质变形岩石的年代学研究, 精确地限定了祁连山东南段的早古生代火山盆地(或岛弧盆地)、拉脊山小洋盆关闭的构造年代.这为造山带构造演化过程中盆地关闭时间的确定开辟了新的途径.      

Fluidized mixtures of magma and rock in a late Caledonian breccia dyke and associated breccia pipes in Appin,Scotland

This paper describes an unusual occurrence of igneous material as clasts in dyke and pipe breccias associated with late Caledonian minor intrusions. It is shown that the clasts were in a plastic condition when incorporated into the breccia rock. These igneous clasts were derived from magma disrupted at depth and then transported into the fluidized breccia columns where they were mixed with large numbers of clasts derived from the quartzite wall-rocks. Textures and planar fabrics developed during collapse of the fluidized system are described and shown to be separable from the later compaction associated with extensive pressure solution of the fine matrix. Most Caledonian breccia pipes lack igneous clasts and it is considered that this group of breccias represent the rarely-preserved boundary zone between active magma and breccia systems.     

鄂尔多斯盆地南部地区的加里东运动

鄂尔多斯盆地南部地区加里东运动的形变特征主要有三种表现形式：即在盆缘地带形成较宽缓褶皱、逆冲推覆构造，上、下古生界呈角度不整合接触，并构成具造山性质的加里东构造带；向盆地内部依次为和缓隆起、高角度断裂，中、下奥陶统不同层位与上覆上古生界不同层位呈微角度不整合接触；整体抬升，下奥陶统与石炭系不同层位呈平行不整合接触。加里东运动形成于奥陶纪晚期，可再细分为两期，分别与北秦岭构造带早古生代的弧－陆碰撞与陆－陆碰撞作用有关。     

Geology of the Severnaya Zemlya Archipelago and the North Kara Terrane in the Russian high Arctic

The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by décollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the décollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with those in the upper structural level along the major N-trending Fiordovoe Lake Fault Zone, which involved several kilometres of dextral strike-slip movement and downthrow to the west. A major Early Carboniferous unconformity separates the folded Mid-Palaeozoic and older rocks from overlying Carboniferous formations, as on Franz Joseph Land and Svalbard. Subsequent latest Palaeozoic to Early Mesozoic orogeny, as on Taimyr, apparently had little influence on the Severnaya Zemlya successions.     

闽西北加里东期混合岩及花岗岩的成因:同变形地壳深熔作用

本文选取闽西北前寒武纪变质基底中的混合岩和花岗岩为研究对象,以探讨两者之间的成因联系.详细的岩石学和主量、微量元素地球化学以及锆石U-Pb年代学研究表明,闽西北混合岩是同变形地壳深熔作用的产物,基底变质岩中的黑云母在较低温(约800℃)、H2O不饱和的条件下发生脱水熔融反应产生熔体,构造变形作用在熔体的分离和迁移过程中起到了重要作用.闽西北基底变质岩可能为形成混合岩和花岗岩的源岩,其深熔产生的初始熔体发生结晶分异作用,堆晶产物形成了混合岩的浅色体,而残余熔体继续演化形成花岗岩.混合岩和相关花岗岩形成基本同时,其成岩年龄为437～441Ma.它们均为华南加里东期构造热事件的产物.     

Precise Dating and Geological Significance of the Caledonian Shangyou Pluton in South Jiangxi Province

The zircon SHRIMP dating age for the Shangyou granites is 464±11 Ma. The geological feature of the pluton is consistent with the isotopic age, which shows that it is a product of Caledonian orogenesis. The Shangyou granites are regarded as peraluminous crust-derived granites to possess the typical geochemical characteristics of calc-alkaline rocks on the active continental margin with enriched Si, K, Al （A/CNK -- 1.11 on average）, HREE, Rb, U, Th and heavily depleted V, Cr, Co, Ni, as well as Ti-Y, Nb-Ta, Zr, Sr, P and Ba, to be commonly corundum normative （av C -- 1.44）. The Shangyou granites with higher 87Sr/86Sr ratios （0.707126-0.712186）, ENd（t） values （-7.29 to -10.22） and （tDM） values （1.52-1.63 Ga）, which are considered to result from partial melting of continental crust metamorphic sedimentary rocks with relatively low of crust maturation degree corresponding to the Middle Proterozoic, to have some possible contributions of mantle-derived components. The Shangyou granites are regarded as post-collision granites, which were formed in a transitional tectonic setting from compression to extension in the Middle Ordovician period after the Yangtze plate was subducted beneath the Cathaysian plate. The Ar-Ar total ages of K-feldspar and biotite are 292.1 Ma and 295.5 Ma respectively, which have recorded information of a late-stage thermal alteration event.     

西昆仑山加里东期花岗岩类浅识

西昆仑山可能有一个呈NW-SE向展布的加里东期花岗岩带存在.除了地质上的依据和判断以外.带内曾获得两个岩体单矿物钾-氩法年龄资料(445Ma、527.6Ma)及一个锆石铀-铅法年龄值(480.43±5Ma).岩体多属钙碱性系列,可能是一个铜、铅、金、稀有金属成矿远景区.岩带西侧的喀拉塔什—依萨克阿特—他龙深断裂可能是加里东期古板块的边界;而这一深断裂的西南侧的木吉—安大力达坂—康西瓦深断裂则是华力西期塔里木板块与伊朗—冈底斯板块间的界线.     

西昆仑加里东期花岗岩带的地质特征

西昆仑地区加里东期花岗岩极为发育,主要沿库地北构造带南侧成带分布,岩体数量多、规模大,不同测试方法获同位素年龄主要为４００￣４８０Ｍａ;岩石组合类型大致可分为石英闪长岩－花岗闪长岩－二长花岗岩组合－钾长花岗岩－二长花岗岩组合和石英闪长岩－花岗闪长岩－斜长花岗岩组合;岩石化学表明该区花岗岩主要为钙碱性系列;构造环境判别岩石为同造山和造山期前岩浆活动产物。结合区域地质资料及与之相伴生蛇绿岩带的地质特征