大别山双河长英质片麻岩在1.0～4.5GPa下的结晶实验及其地质意义     

刘晓春  杨农  曲玮 《地球学报》1999,20(2):113-120

在７５０～１２００℃、１．０～４．５ＧＰａ条件下对取自于大别山双河的长英质片麻岩进行了重结晶实验。在７５０℃时,随压力增加矿物生成顺序为：角闪石在１．７５ＧＰａ时出现,２．５ＧＰａ时消失;黑云母在１．７５ＧＰａ时通过水化反应生成多硅白云母;绿帘石可以稳定到＞３．５ＧＰａ,在４ＧＰａ时转变成硬柱石;石榴石和绿辉石在１．５ＧＰａ时开始出现,而斜长石在１．７５ＧＰａ时消失;石英在３ＧＰａ时转变为柯石英。这表明角闪岩相与榴辉岩相的转变发生在１．５～１．７５ＧＰａ,并且,榴辉岩相可进一步划分出角闪榴辉岩相、柯石英榴辉岩相和硬柱石榴辉岩相等,它们分别指示不同的压力区间。多硅白云母是长英质岩石在高压－超高压条件下的主要共生矿物,其水化反应特性及结构水的保存致使陆壳在深俯冲过程中未发生明显的脱水作用,这是大别山碰撞带未能形成钙碱性岩浆弧的主要原因。  相似文献   

胶东地区基底长英质片麻岩的地球化学特征及其构造归属   总被引：18，自引：8，他引：10  

李永刚  郭敬辉 《岩石学报》1999,15(4):557-563

通过对胶东地区基底长英质片麻岩的地球化学研究发现, 莱西－栖霞一带的基底长英质片麻岩具有太古宙长英质片麻岩的典型特征, 微量元素组成与板内花岗岩类相似。该区应该属于华北陆块的一部分。荣成地区是苏鲁超高压变质带的典型地区, 其基底长英质片麻岩与栖霞一带不同, 是过铝型花岗岩类, 具有火山弧花岗岩类的地球化学特征, 结合普遍存在的０．８Ｇａ 的同位素年代资料, 可以确定荣成地区原来是扬子陆块的一部分。文登－威海地区的长英质片麻岩的常量和微量元素组成都与栖霞地区相当, 很可能也是华北陆块的一部分。从长英质片麻岩代表的基底岩石的地球化学差异来看, 超高压变质带与华北板块的界线应该在五莲－青岛－荣成断裂。威海一带含柯石英超高压岩块的出现很可能是因为大陆碰撞过程中复杂的构造原因, 使超高压岩片中的一部分进入了华北基底分布区。  相似文献   

High- and Ultrahigh-pressure Metamorphism and Retrogressive Textures of Gneiss in the Donghai Area——Evidence from gneisses in drillhole ZK2304   总被引：6，自引：1，他引：5  

LIU Fulai  XU Zhiqin  XU Huifen  YANG Jingsui Institute of Geology  CAGS  Baiwanzhuang Rd.  Beijing Zhu Xiling 《《地质学报》英文版》1999,73(3)

In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamorphic reactions. In addition to garnet, jadeititic-clinopyroxene and rutile, other peak stage (M2) minerals in some gneisses include phengite, aragonite and coesite or quartz pseudomorphs after coesite. The typical peak-stage mineral assemblages in gneisses are characterized by garnet + jadeitic-clinopyroxene + rutile + coesite, garnet + jadeitic-clinopyroxene + phengite + rutile ± coesite and garnet + jadeitic-clinopyroxene + aragonite + rutile ± coesite. The grossular content (Gro) in garnet is high and may reach 50. 1 mol%. The SiO2 content of phengite ranges from 54.37% to 54.84% with 3.54-3.57 p.f.u. Quartz pseudomorphs after coesite occur as inclusions in garnet.The gneisses of the Donghai area have been subjected to multistage recrystallization and exhibit a closewise P-T evolution  相似文献   

库鲁克塔格地区新太古代深沟片麻杂岩特征   总被引：10，自引：2，他引：8  

董富荣  李嵩龄  冯新昌 《新疆地质》1999,(1)

新疆库鲁克塔格地区深沟片麻杂岩是由新太古代阜平期表壳岩组合、灰色片麻岩及古元古代红色片麻岩组成的杂岩体。表壳岩组合为变火山－沉积岩、灰色片麻岩为太古宙ＴＴＧ岩浆岩组合,红色片麻岩为深沟变质核杂岩同构造侵入的“Ｉ”型花岗岩。深沟片麻杂岩组成内核,古元古界兴地塔格岩群组成滑脱系,古元古界南辛格尔塔格岩组组成盖层,它们构成一个完整的深沟变质核杂岩构造。灰色片麻岩、表壳岩组合的Ｓｍ－Ｎｄ全岩等时线年龄（２８３０．２±７９．７）Ｍａ,红色片麻岩锆石Ｕ－Ｐｂ年龄（２０５９±１４）Ｍａ。  相似文献   

辽西叶柏寿片麻岩的特征与成因探讨     

王来春 《国土资源》1994,(4)

辽西建平地区太古宙变质杂岩主体岩石为叶柏寿片麻岩，经历了麻粒岩相的高级变质作用，由于后期退变质作用，部分退变为角闪岩相片麻岩和绿片岩相片麻岩。叶柏寿片麻岩的原岩为中性侵入岩，为钙碱性系列的岩石，同于壳源分异花岗岩。其形成环境为构造活动带。  相似文献   

早前寒武纪克拉通内的叠瓦拼贴构造     

杨书桐  胡受奚 《国土资源》1993,(2)

从早期地幔热对流的动力学特点出发,针对早前寒武纪克拉通内的一些有争议的问题进行了解释;认为不少绿岩地块或地体之间,绿岩与花岗片麻岩之间并非是因垂直运动造成的原地不整合接触,而是因大规模水平运动产生的叠瓦拼贴,这一思想将会帮助我们重新认识克拉通区早前寒武纪地壳演化,并进一步指导填图和地层划分以及找矿工作。  相似文献   

北京城南平原区钻孔中发现太古宙片麻岩   总被引：1，自引：0，他引：1  

吕金波  李良景  丁长顺  王泽龙  孙永华 《城市地质》2008,3(2):28-32

北京市地质调查研究院在进行1：5万庞各庄镇幅和1：25万北京市幅区域地质调查过程中,相继在北京市大兴区安定镇（兴热2井）、榆垡镇（兴热1井）两个地热钻孔中发现了太古宙片麻岩,不但对全面了解太古宙片麻岩在北京地区的分布范围及深度有重要意义,而且对确定地热井的隔水底板下限有重要的现实意义。兴热2井位于北京市大兴区安定镇铁道部培训中心,埋深2050m以下为太古宙片麻岩。兴热1井位于北京市大兴区榆垡镇,埋深1610m以下为太古宙变质岩。从△T磁异常图可见,固安、榆垡、安定、廊坊一带为片麻岩隆起区。  相似文献   

Determination of magnetic anisotropy and a ca 1.2 Ga palaeomagnetic pole from the Bremer Bay area,Albany Mobile Belt,Western Australia     

S. A. Pisarevsky  L. B. Harris 《Australian Journal of Earth Sciences》2013,60(1):101-112

Granulite facies tonalitic gneiss, mafic granulite and late metadolerite dykes from Bremer Bay in the Mesoproterozoic Albany Mobile Belt yield palaeomagnetic remanence that were acquired between ca 1.2 Ga and 1.1 Ga. A well‐constrained pole (66.6°N, 303.7°E) fits the ca 1.2 Ga part of the Precambrian Australian apparent polar wander path. This pole is in agreement with the high‐latitude position of Australia at ca 1.2–1.1 Ga shown on some Rodinia reconstructions. More data are required before any significance can be attributed to a second, poorly defined pole (41.8°S, 243.7°E) that falls at some distance from the ca 0.8 Ga part of the Australian apparent polar wander path. Magnetic anisotropy measurements from all samples except late granite dykes indicate northeast‐southwest elongation (i.e. parallel to the local trend of the orogenic belt) and northwest‐southeast contraction. This is in agreement with the orientation of principal strain axes deduced from structures formed during late stages of ductile deformation. The mean magnetic fabric lineation (long axis of the strain ellipsoid) is subparallel to a mineral elongation lineation and the axes of late upright to inclined folds. Short axes of the strain ellipsoid determined from magnetic fabric measurements are in a similar orientation to poles to the axial surfaces of these folds and to the associated cleavage. This mean shortening axis bisects late conjugate ductile shear zones that overprint the folds. This study has shown that structurally complex high‐grade gneisses and intrusive rocks with variable timing relationships may yield meaningful palaeomagnetic results for late stages of metamorphism. Magnetic anisotropy analysis is also seen to be a valuable tool in providing principal strain directions for late ductile deformation.  相似文献   

Metamorphic history of eclogites and country rock gneisses in the Aktyuz area,Northern Tien‐Shan,Kyrgyzstan: a record from initiation of subduction through to oceanic closure by continent–continent collision     

R. T. OROZBAEV  A. TAKASU  A. B. BAKIROV  M. TAGIRI  K. S. SAKIEV 《Journal of Metamorphic Geology》2010,28(3):317-339

Eclogites and related high‐P metamorphic rocks occur in the Zaili Range of the Northern Kyrgyz Tien‐Shan (Tianshan) Mountains, which are located in the south‐western segment of the Central Asian Orogenic Belt. Eclogites are preserved in the cores of garnet amphibolites and amphibolites that occur in the Aktyuz area as boudins and layers (up to 2000 m in length) within country rock gneisses. The textures and mineral chemistry of the Aktyuz eclogites, garnet amphibolites and country rock gneisses record three distinct metamorphic events (M1–M3). In the eclogites, the first MP–HT metamorphic event (M1) of amphibolite/epidote‐amphibolite facies conditions (560–650 °C, 4–10 kbar) is established from relict mineral assemblages of polyphase inclusions in the cores and mantles of garnet, i.e. Mg‐taramite + Fe‐staurolite + paragonite ± oligoclase (An_<16) ± hematite. The eclogites also record the second HP‐LT metamorphism (M2) with a prograde stage passing through epidote‐blueschist facies conditions (330–570 °C, 8–16 kbar) to peak metamorphism in the eclogite facies (550–660 °C, 21–23 kbar) and subsequent retrograde metamorphism to epidote‐amphibolite facies conditions (545–565 °C and 10–11 kbar) that defines a clockwise P–T path. thermocalc (average P–T mode) calculations and other geothermobarometers have been applied for the estimation of P–T conditions. M3 is inferred from the garnet amphibolites and country rock gneisses. Garnet amphibolites that underwent this pervasive HP–HT metamorphism after the eclogite facies equilibrium have a peak metamorphic assemblage of garnet and pargasite. The prograde and peak metamorphic conditions of the garnet amphibolites are estimated to be 600–640 °C; 11–12 kbar and 675–735 °C and 14–15 kbar, respectively. Inclusion phases in porphyroblastic plagioclase in the country rock gneisses suggest a prograde stage of the epidote‐amphibolite facies (477 °C and 10 kbar). The peak mineral assemblage of the country rock gneisses of garnet, plagioclase (An_11–16), phengite, biotite, quartz and rutile indicate 635–745 °C and 13–15 kbar. The P–T conditions estimated for the prograde, peak and retrograde stages in garnet amphibolite and country rock are similar, implying that the third metamorphic event in the garnet amphibolites was correlated with the metamorphism in the country rock gneisses. The eclogites also show evidence of the third metamorphic event with development of the prograde mineral assemblage pargasite, oligoclase and biotite after the retrograde epidote‐amphibolite facies metamorphism. The three metamorphic events occurred in distinct tectonic settings: (i) metamorphism along the hot hangingwall at the inception of subduction, (ii) subsequent subduction zone metamorphism of the oceanic plate and exhumation, and (iii) continent–continent collision and exhumation of the entire metamorphic sequences. These tectonic processes document the initial stage of closure of a palaeo‐ocean subduction to its completion by continent–continent collision.  相似文献   

含榴花岗片麻岩 Lu-Hf 年代学初探     

张超  程昊  J D Vervoort 《地球化学》2012,(4):371-379

对西大别四道河含石榴子石花岗片麻岩进行了锆石 U-Pb 和石榴子石 Lu-Hf 年代学测试,锆石 U-Pb谐和年龄为(223±1) Ma,石榴子石-全岩 Lu-Hf 等时线年龄为(212.2±0.7) Ma.石榴子石具有极高的母子体同位素比值(176Lu/177Hf =~300).结合锆石和石榴子石的微量元素特征,该锆石 U-Pb 年龄代表的可能是超高压/高压变质时间,石榴子石 Lu-Hf 年龄代表的是石榴子石重结晶时间,可能指示了后期退变质作用流体活动  相似文献