苏鲁高压—超高压变质带南部花岗片麻岩—花岗岩的多时代演化   总被引：20，自引：5，他引：20  

徐惠芬  J.G.Liou 《地质学报》2001,75(3):371-378,T003,T004

苏鲁高压－超高压变质带中，广泛分布有花岗片麻岩－花岗岩系列，有关其形成的时代和成因机制长期存在争议。岩石露头表现为强烈的片麻理，并且多数和榴辉岩及榴辉岩相岩石密切伴生。其岩石类型有变化，从斜长片麻岩－花岗闪长质片麻岩－二长花岗片麻岩演化到花岗岩。矿物和地球化学变化也较大。从残留的高压和超高压矿物及其退变质反应等。说明它们中有部分曾经历了高压－超高压变质作用。该变质部连云港地区4个二长花岗片麻岩－花岗岩岩体中精的单颗粒锆石，运用Pb-Pb法（质谱计双带源逐层发－沉积法）和U-Pb法（离子探针SHRIMP分析），获得的年龄值跨度大，从859Ma到150Ma，分别属于4个年龄段（时段），但是主要数据集中在600－859Ma和220－250Ma两个时段，锆石的形貌特征研究显示，这些花岗片麻岩－花岗岩是苏鲁高压变质带中长期演化的产物。其物质来源与古元古代，乃至太古变质表壳岩密切相关。元古代大量岩浆结晶型锆石指示了当时存在强烈的花岗岩浆活动，导致大量花岗岩类岩石的形成。古生代（加里东期）和中生代早期（印支期）分别经历了变质作用，尤其是印支期，至少一部分和榴辉岩源岩一起经历了高压－超高压变质作用，并且伴随有地壳部分熔融，引起又一次花岗岩浆活动，再生花岗岩，该区南部东海地区尤为明显，中生代晚期燕山期的岩浆，热液活动对花岗片麻岩也有影响，其中新元古代和印支期则是花岗片麻岩及至大别造山带中两个重要的地质构造时期。  相似文献   

大别山超高压榴辉岩流变强度——来自高温高压实验的证据   总被引：5，自引：3，他引：5  

金振民  章军锋  Green H.W.  金淑燕  王永锋 《地球科学》2001,26(6):574-580

利用Griggs型 5GPa高压仪器 ,在柯石英稳定域围压条件下 ( >3GPa)完成大别山超高压榴辉岩流变学实验 ,建立了榴辉岩流变状态本构方程 (流动律 ) : ε=Aexp( -Q/RT)σn ,应力指数 (n)为 3 .4 ,活化能 (Q)为 4 80kJ/mol,结构常数 (A)为 10 3.3.实验结果表明 :( 1)作为两相矿物组成的榴辉岩 ,其流变学强度在很大程度上取决于强相矿物 (石榴石 )和弱相矿物 (绿辉石 )含量比例 ;( 2 )天然榴辉岩塑性变形机制是以位错蠕变为主 ;( 3 )根据实验成果比较榴辉岩和上地幔方辉橄榄岩流变学强度相当 ,两者耦合在大陆深俯冲 10 0km左右深度发生拆沉作用可能性很小 ,与上地幔上隆 (upwelling)作用有关的造山期后伸展作用对超高压岩石折返更具有重要意义 .  相似文献   

大别山超高压变质带的构造背景   总被引：8，自引：4，他引：8  

江来利  徐树桐 《地质论评》1995,41(3):229-237

大别山南部的超高压变质带具有特征的榴辉岩相矿物组合，榴辉岩的岩石化学及稀土元素特征及其伴生的岩石组合，表明这个带是以陆壳成分为主混有少量上地幔及洋壳成分的混杂岩，榴辉岩相围岩和大别群具有不同的变质和变形特征。超高压变质带形成于扬子和中朝板块大陆碰撞的构造环境，是扬子板块陆壳向北俯冲到一定深度的变质产物。  相似文献   

华中榴辉岩带地球化学和年代学研究   总被引：8，自引：0，他引：8  

张泽明  游振东 《矿物学报》1994,14(3):215-222

根据地质产状，华中高压超高压变质带中的榴辉岩可划分为与超基性岩伴生的P类和与片麻岩、斜长角闪岩等伴生的G类。它们具有不同的地球化学特征，但均为大洋基性火成岩经复杂成分演化作用的产物。全岩-矿物Sm－Nd和颗粒锆石207Pb-206Pb年代学研究表明，超高压变质作用很可能发生在加里东期（480Ma）；而印支期（265Ma）则可能是超高压变质岩的后期高压退变质改造阶段。  相似文献   

Petrogenesis of garnet-bearing ultramafic rocks and associated eclogites in the Su-Lu ultrahigh-P metamorphic terrane, eastern China   总被引：10，自引：3，他引：10  

R. Y. ZHANG  J. G. LIOU  BOLIN. CONG 《Journal of Metamorphic Geology》1994,12(2):169-186

Ultramafic blocks that themselves contain eclogite lenses in the Triassic Su-Lu ultrahigh-P terrane of eastern China range in size from hundreds of metres to kilometres. The ultramafic blocks are enclosed in quartzofeldspathic gneiss of early Proterozoic age. Ultramafic rocks include garnetiferous lherzolite, wehrlite, pyroxenite, and hornblende peridotite. Garnet lherzolites are relatively depleted in Al₂O₃ (<3.8wt%), CaO (<3.2%) and TiO₂ (<0.11 wt%), and are low in total REE contents (several p.p.m.), suggesting that the rocks are residual mantle material that was subjected to low degrees of partial melting. The eclogite lenses or layers within the ultramafic rocks are characterized by higher MgO and CaO, lower Al₂O₃ and TiO₂ contents, and a higher CaO/Al₂O₃ ratio compared to eclogites enclosed in the quartzofeldspathic gneiss. Scatter in the plots of major and trace elements vs. MgO, REE patterns and La, Sm and Lu contents suggest that some eclogites were derived from melts formed by various degrees (0.05–0.20) of partial melting of peridotite, and that other eclogites formed by accumulation of garnet and clinopyroxene ± trapped melt in the upper mantle. Both ultramafic and eclogitic rocks have experienced a complex metamorphic history. At least six stages of recrystallization occurred in the ultramafic rocks based on an analysis of reaction textures and mineral compositions. Stage I is a high temperature protolith assemblage of Ol + Opx + Cpx + Spl. Stage II consists of the ultrahigh-pressure assemblage Ol + Cpx + Opx + Grt. Stage III is manifested by the appearance of fine-grained garnet after coarse-grained garnet. Stage IV is characterized by formation of kelyphitic rims of fibrous Opx and Cpx around garnet, and replacement of garnet by spinel and pargasitic-hornblende. Stage V is represented by the assemblage Ol + Opx + Prg-Hbl + Spl. The mineral assemblages of stages VI_A and VI_B are Ol + Tr-Amp + Chl and Serp + Chl ± talc, respectively. Garnet and orthopyroxene all show a decrease in MgO with retrogressive recrystallization and Na₂O in clinopyroxene also decreases throughout this history. Eclogites enclosed within ultramafic blocks consist of Grt + Omp + Rt ± Qtz ± Phn. A few quartz-bearing eclogites contain rounded and oval inclusion of polycrystalline quartz aggregates after coesite in garnet and omphacite. Minor retrograde features include thin symplectic rims or secondary amphiboles after Cpx, and ilmenite after rutile. P-T estimates indicate that the ultrahigh-metamorphism (stage II) of ultramafic rocks occurred at 820-900d? C and 36-41 kbar and that peak metamorphism of eclogites occurred at 730-900d? C and >28 kbar. Consonant with earlier plate tectonic models, we suggest that these rocks were underplated at the base of the continental crust. The rocks then underwent ultrahigh-pressure metamorphism and were tectonically emplaced into thickened continental crust during the Triassic collision between the Sino-Korean and Yangtze cratons.  相似文献   

变质地质学的三大前缘课题     

游振东 《地学前缘》1994,(Z1)

本文主要从三个方面反映１９８７年以来国内外变质地质学研究的新进展：（１）变质Ｐ－Ｔ－ｔ轨迹与区域岩石学研究；（２）变质流体与岩石的相互作用；（３）高压、超高压变质。变质ｐ－Ｔ－ｔ轨迹按地壳拉张区、地壳增厚区、俯冲带和麻粒岩相变质地区等不同构造环境予以论列；变质流体岩石的相互关系是按区域变质、接触变质和麻粒岩相变质地区等三个类型对比描述。高压、超高压变质研究近年来得到快速发展，也提出了许多问题。本文主要介绍柯石英榴辉岩岩石学和榴辉岩相岩石学的主要问题。  相似文献   

榴辉岩相的重新评价   总被引：1，自引：0，他引：1  

刘晓春  胡克 《地质科技情报》1994,13(1):29-35

给出了超基性，基性，泥质，长英质，硅质和碳酸盐等不系列岩石榴辉岩相的典型矿物组合，重新确认了榴辉岩相的存在，榴辉岩相的Ｐ－Ｔ区间大致为１．０－４．０ＧＰａ和４００－９００℃可进步划分出低温，中温，高温和超高压等４个亚相，除少数地区蓝片岩相在空间上可直接过渡为低温榴辉岩亚相外，榴辉岩相与其它变质相不构成相系，它们之间属相变关系，最后对榴辉岩相的复杂性进行了讨论。  相似文献   

大别山杂岩中两类斜长角闪岩的矿物学鉴别标志及对榴辉岩成因的意义   总被引：3，自引：1，他引：3  

李曙光  肖益林 《矿物学报》1994,14(2):115-122

鉴别造山带斜长角闪岩由含柯石英榴辉岩退变而成，还是未经过超高压变质作用的普通斜长角闪岩，对研究榴辉岩成因有重要意义，本文提出用斜长角闪岩中两个最常见矿物，石榴长石和角闪石的ＭｎＯ和ＭｇＯ含量以及四次配位Ａ１和六次配位Ａ１数可有效地区分这两种不同成因的斜长角闪岩，本文提供的数据表明：大别群变质杂岩中有一部分斜长闪岩并未经历过超高压变质作用，因此，大别群中的超高压变质岩是构造侵入到角闪岩相岩石中的产物  相似文献   

中国中部河南省榴辉岩中柯石英的发现及其构造意义   总被引：12，自引：2，他引：12  

张儒媛  刘忠光 《岩石学报》1993,9(2):186-191

  相似文献   

Thermobaric structure of a traverse across western Dabieshan: implications for collision tectonics between the Sino-Korean and Yangtze cratons   总被引：18，自引：0，他引：18  

X. Liu  C. Wei  S. Li  S. Dong  J. Liu 《Journal of Metamorphic Geology》2004,22(4):361-379

As the best preserved high‐ and ultrahigh‐pressure (HP and UHP) metamorphic terrane in the Qinling‐Dabieshan‐Sulu orogen, western Dabieshan is divided into six lithotectonic units along a traverse across the orogen, i.e. from north to south, the Nanwan, Balifan, Huwan, Xinxian, Hong'an and Mulanshan units. In this terrane five eclogite‐bearing zones (I–V) are developed. The garnet and clinopyroxene in eclogites from these zones exhibit chemical zoning, suggesting that the rims record general peak temperature and pressure. Thermobarometric study indicates that the peak P–T conditions of eclogite are 550–570°C and 21 kbar for Zone I, 470–500°C and 14–17 kbar for Zone II, 620–670°C and 26–29 kbar for Zone III, 530–560°C and 20–22 kbar for Zone IV, and 490–510°C and 19–20 kbar for Zone V. The symmetrical thermobaric pattern, in conjunction with structural and geochronological data, demonstrates that the Huwan and Hong'an units belong to the same HP slice overlying the UHP slice. This pattern, together with the Mulanshan LT/HP blueschist–greenschist belt in the south, roughly constitutes a ‘normal’ metamorphic zonation. However, clear metamorphic gaps occur between different slices. It is inferred that the LT/HP, HP and UHP slices were broken up from the downgoing slab during subduction and reached different depths along different geothermal gradients. The successive subduction of underlying slices leads to a nearly concomitant uplift of overlying slices, whereas exhumation of the deepest UHP slice was effected by underthrusting of the lower crust of the Yangtze craton.  相似文献