博格达陆内碰撞造山带挤压—拉张构造转折期的侵入活动   总被引：35，自引：17，他引：35  

顾连兴胡受奚  于春水赵明吴昌志  李宏宇 《岩石学报》2001,17(2):187-198

博格达造山带位于准噶尔与吐鲁番-哈密前寒武纪地块之间,是一个早-中石炭世的陆内裂谷带,该裂谷带于中-晚石炭世闭合.岩相学、岩石化学、稀土元素、微量元素和同位素研究表明,该造山带侵入岩以辉绿岩岩床、岩株和岩墙为主,仅有少数中-酸性岩岩株.这些侵入岩的橄榄拉斑玄武质原始岩浆可能来自轻度亏损的地幔源区,并在地壳深部形成过分层岩浆房.辉绿岩和中-酸性岩分别是分层岩浆房的上部和下部层位岩浆先后上侵和演化产物.野外地质关系及上大河沿中-酸性侵入体的298.4±0.76 Ma Rb-Sr等时线年龄,不但表明博格达地区晚于海西期的侵入活动并不重要,还表明该造山带侵入岩的定位紧随博格达裂谷的陆内碰撞,并代表了地球动力学环境由挤压变为拉张这个重大转折时期.  相似文献   

Petrology of Whiteschists and Associated Rocks at Mautia Hill (Tanzania): Fluid Infiltration during High-Grade Metamorphism?   总被引：2，自引：0，他引：2  

JONS  NIELS; SCHENK  VOLKER 《Journal of Petrology》2004,45(10):1959-1981

Talc–kyanite schists (whiteschists), magnesiohornblende–kyanite–talc–quartzschists and enstatite–sapphirine–chlorite schistsoccur at Mautia Hill in the East African Orogen of Tanzania.They are associated with metapelites and garnet–clinopyroxene–quartzmetabasites. Geobarometry (GASP/GADS equilibria) applied tothe latter two rock types indicates a peak pressure of P = 10–11kbar. These results are confirmed by the high fO₂ assemblagehollandite–kyanite–quartz and late-stage manganianandalusite that contains up to 19·5 mol. % Mn₂SiO₅. Maximumtemperatures of T = 720°C are inferred from late-stage yoderite+ quartz. A clockwise P–T evolution is constrained byprograde kyanite inclusions in metapelitic garnet and late-stagereaction rims of cordierite between green yoderite and talcthat reflect conditions at least 3–4 kbar below the peakpressure. Oxidizing conditions are recorded throughout the metamorphichistory of the whiteschists and chlorite schists, as indicatedby the presence of haematite coexisting with pseudobrookiteand/or rutile. Increasing water activity near peak pressuresis thought to have led to the breakdown of the high-pressureassemblages (Tlc–Ky–Hem and Mg-Hbl–Ky–Hem)and the subsequent formation of certain uncommon minerals, e.g.yellow sapphirine, Mn–andalusite, green and purple yoderite,piemontite and boron-free kornerupine. The proposed increasein water activity is attributed to fluid infiltration resultingfrom the devolatilization of underlying sediments during metamorphism. KEY WORDS: fluid infiltration; high-pressure amphibolite facies; East African Orogen; Pan-African; whiteschist  相似文献   

The Central Granites-Gneiss-Migmatite Belt (CGGMB) of Madagascar: the Eastern Neoproterozoic Suture of the East African Orogen   总被引：1，自引：0，他引：1  

R.A. Rambeloson  M. Yoshida  V. Ramasiarinoro  L. Le Duc  B. Ralison 《Gondwana Research》2003,6(4):641-651

The northeastern part of Madagascar is characterized by Archaean to early Proterozoic rocks composed principally of Archaean granite and greenstone/amphibolite as well as reworked migmatite with subordinate Proterozoic paragneisses. The southern part is mostly occupied by Proterozoic rocks, composed mostly of Meso to Neo-Proterozoic and less metamorphic metasediments (Itremo Group) in the northwest, para- and ortho-gneisses in most other areas, with minor granitic gneisses with some Archaean components in the southeast. The north-northwest trending Central Granite-Gneiss-Migmatite Belt (CGGMB) is situated at the western margin of the Archaean-early Proterozoic terrain. The CGGMB is composed of granite, gneiss and migmatite with distinct lithologies and structures. They are: i) many types of granites including alkaline to mildly alkaline granites, and calc-alkaline granites; ii) batholitic granites, migmatitic granites and granite dyke swarm, iii) eclogite, and iv) the Ankazobe-Antananarivo-Fianarantsoa Virgation.

The CGGMB was formed by the collision of the palaeo-Dharwar Craton to the east and the East African Orogen to the west at ca. 820-720 Ma and suffered indentation by a part of the western part of the East African Orogen at ca. 530 Ma that produced the Ankazobe-Antananarivo-Fianarantsoa Virgation at the centre of the CGGMB. Thus, the CGGMB is proposed to be the continuation of the eastern suture between the palaeo Dharwar Craton and the East African Orogen, and carries the main feature of the Pan-African collisional event in Madagascar.  相似文献   

DETACHMENT FAULT IN DINGGYE AREA IN THE MIDDLE PART OF THE HIMALAYAN OROGEN     

LIUDemin LIDewei 《大地构造与成矿学(英文版)》2003,27(1):70-80

Dinggye lies in the middle part of the Himalayan Orogen. A lot of low angle extension detachment faults have been developed in Dinggye area and some of them make up the main body of the South Tibet Detachment System. On the whole, the extension direction of all the detachment faults is perpendicular to the strike of the Himalayan Orogen. Each detachment fault has its distinct characteristics. Mylonite was extensively developed in the detachment faults and can be divided into a variety of types such as siliceous mylonite, felsic mylonite, granite mylonite, protomylonite, crystallization mylonite and so on. On the basis of our field survey works, these detachment faults can be classified according to their locations into three units listed as follows: (1) In the northern part of the study area, the detachment faults occur on large scale and in orbicular shape, and form the middle layer of the metamorphic core complexes. (2) In the southern part of the study area, the detachment faults occur in linear shape that is parallel to the Himalayan Orogen and has a stable attitude, and have undergone two phases of development. In the first phase, the Rouqiechun Group rocks were formed and make up the hanging wall, while in the second phase the Jiachun Group rocks were formed and make up the hanging wall. (3) In the southeastern part of the study area, the detachment faults strike nearly along southeast direction in a stable way and some of these detachment faults were distorted by the late-formed faults and folds. Furthermore, in the southwestern part of the study area, the ductile shear zones are parallel to the detachment faults.  相似文献   

辽吉地区古元古代造山作用的大陆动力学过程及其壳内响应   总被引：1，自引：0，他引：1       下载免费PDF全文

李三忠  刘永江  杨振升 《地球物理学报》1998,41(Z1):142-152

古元古代是地质演化历史中一个重要转折时期,探讨其大陆动力学特征、机制、过程及其壳内响应具有重要的科学意义．本文以辽吉地区古元古代造山带为例,结合同位素年代学资料,综合分析了该区大陆动力学过程的构造、变质、岩浆、沉积等方面壳内响应特征最后,将该区深部大陆动力学过程划分为三大历史阶段：1)造山期前伸展阶段,包括建造伸展期和改造伸展期,深部底侵发生,壳内响应出现基底裂解、盖层顺层滑脱、拉张型垂向递增变质、岩浆呈席状侵位等;2)造山期挤压收缩阶段,俯冲碰撞,岩石田地幢可能出现拆沉,壳内响应出现招皱逆冲、双侧造山、侧向递增变质、碰撞型岩浆作用发生、早期岩浆底辟再就位等;3)造山期后伸展塌陷阶段,大陆岩石田在重力均衡作用下发生微弱伸展塌陷,出现环斑花岗岩侵位,等压冷却为特征的退变质表明没有明显的伸展剥蚀,没有出现明显的山根．  相似文献   

新疆北部花岗岩─水~18O/~16O交换反应动力学──对于造山带岩浆熔融与流体循环的意义          下载免费PDF全文

刘伟  刘建明  储雪蕾  孙世华 《地球物理学报》1998,41(Z1):195-205

对新疆北部花岗岩的两个典型岩体-阿拉尔和二台北岩体进行了系统的氧同位素组成测定,以探讨造山带的流体循环以及岩浆源区的熔融两个岩体的岩浆源区相对亏损18OZ它们在上部地壳侵位的次团相冷凝过程中共生矿物向富集18O的方向不平衡偏转推覆到阿尔泰山区热板片之下的晚古生代沉积物冷板片,通过进变质过程中的脱水反应提供了大量的含水流体．在倒转地温梯度驱动下,含水流体从下伏冷板片释放到上覆热板片,与富18O的早古生代变质沉积物发生18O／16O交换反应,并且最终导致造山花岗岩源区的熔融,产生相对亏损18O的过铝质花岗岩浆．对于以二台北岩体为代表的非造山花岗岩而言,幔源岩浆的下垫诱导的进变质反应造成流体对流,促进了幔源岩浆与花岗岩源区岩石的18O／16O交换反应,从而降低了后者的δ18O值．流体循环是深熔作用的先驱事件．与两个岩体侵位相联系的流体具有围绕岩体分布的外封皮性质．当岩浆温度下降到某一数值时,它们迅速进入岩体,瞬间流动速率较大．随着18O／16O交换反应的进行,流体来源迅速枯竭.  相似文献   

Geology and tectonic evolution of the Palaeoproterozoic Bryah, Padbury and Yerrida Basins (formerly Glengarry Basin), Western Australia: implications for the history of the south-central Capricorn Orogen     

F. Pirajno  S. A. Occhipinti  C. P. Swager 《Precambrian Research》1998,90(3-4)

The Palaeoproterozoic Bryah, Padbury and Yerrida Basins are situated along the northwestern margin of the Archaean Yilgarn Craton, central Western Australia. These basins form part of the Capricorn Orogen, which developed between 2.0 and 1.8 Ga as a result of the collision between the Archaean Pilbara and Yilgarn cratons. The Bryah, Padbury and Yerrida Basins, which at the present day cover a total area of ca 20 000 km², were formerly considered as one geological entity, the Glengarry Basin. These three basins are characterized by distinct stratigraphy, igneous activity, structural and metamorphic history, and mineral deposit types. Igneous activity only affected the Bryah and Yerrida Basins, with voluminous eruptions of tholeiitic magma. In the Bryah Basin tholeiitic volcanic rocks are Mg-rich and have mixed MORB to oceanic island chemical signatures, but with a boninitic (subduction-related) component. In the Yerrida Basin tholeiites are Fe-rich and have chemical signatures that suggest a mixed tectonic environment ranging from oceanic to continental. It is considered possible that this tholeiitic magmatism is related to a mantle plume. Two models for the tectonic evolution of the Bryah, Padbury and Yerrida Basins are proposed: (1) the Bryah and Yerrida Basins were formed in a back-arc setting, whilst the Padbury Basin developed as a retro-arc foreland basin over the Bryah Basin; and/or (2) strike-slip transtension, during and following the Pilbara-Yilgarn collision, created the Bryah and Yerrida strike-slip pull-apart Basins. A change in regional stress regime resulted in the inversion of the basins and the development of a foreland basin in the northwest (Padbury Basin).  相似文献   

中央山系大别-东秦岭和东昆仑造山带最古老岩系变质过程对比   总被引：3，自引：2，他引：1  

陈能松  朱杰  游振东  张克信 《地球科学》1998,23(5):88

大别造山带、东秦岭造山带和东昆仑造山带是中国中央山系的主要构成部分,每个造山带古老岩系的变质作用过程各具特色．大别山最古老岩系大别岩群于印支期陆内俯冲碰撞,发生了区域性的中偏高压区域变质作用,顺时针型ｐｔ轨迹上ｔｍａｘ和ｐｍａｘ近于同时达到,退变质轨迹段斜率陡,埋深后受构造驱动快速抬升到上中地壳．东秦岭最古老岩系秦岭岩群在晋宁期（约１．０Ｇａ前）初始板块构造总背景下发生强烈的中压型碰撞变质作用,顺时针型ｐｔ轨迹上ｔｍａｘ在压力大幅度降低的过程中达到,反映弧陆碰撞增厚后深埋岩系受重力均衡抬升;至加里东期,秦岭岩群再次在板块构造的总背景下发生岛弧型变质,局部叠加中压型接触变质作用;晚海西以来北秦岭东段缺乏高于低角闪岩相条件的区域变质作用记录．东昆仑造山带最古老岩系于吕梁或早吕梁期发生中压碰撞区域变质,主体为角闪岩相,局部高角闪岩相－麻粒岩相条件,造山带剥露较浅使低压变质带得以良好保存．  相似文献   

河南内乡县银洞沟银矿地质和流体包裹体特征及成因类型   总被引：31，自引：5，他引：31  

张静  陈衍景  李国平  李忠烈  王志光 《矿物岩石》2004,24(3):55-64

河南内乡县银洞沟银(多金属)矿床位于东秦岭北部的二郎坪地体,属于断控脉状矿床。矿石有石英脉型和蚀变岩型,围岩蚀变以硅化、绢云母化、碳酸盐化、绿泥石化为主,主要银矿物为银黝铜矿、辉银矿、自然银等。成矿过程可以划分为早、中、晚3个阶段,分别形成含黄铁矿和/或毒砂的石英脉、多金属硫化物网脉和石英-碳酸盐细脉。脉石矿物石英、碳酸盐等含大量流体包裹体,包括富/纯CO2、含CO2水溶液和水溶液3种组分类型的包裹体。矿床形成于中温(270℃～370℃)、低盐度(<11.4%)、低密度流体系统。成矿早阶段以深源富碳流体为主,中阶段流体发生沸腾,晚阶段为盐水溶液。从早到晚,包裹体捕获压力由280MPa～320MPa降为90MPa～92MPa,成矿深度略有变浅,流体系统静岩压力变为静水压力体系,趋于开放,指示区域应力场由挤压向伸展转变。银洞沟银矿的地质特征和成矿流体系统与造山型金矿一致,应属造山型银矿;结合区域构造背景,认为银洞沟银矿形成于陆陆碰撞体制,并可以借助CMF模式解释成因。  相似文献   

八达岭基性岩和高Ba—Sr花岗岩地球化学特征及成因探讨：华北和大别—苏鲁造山带中生代岩浆岩的对比   总被引：27，自引：15，他引：27  

钱青  钟孙霖等 《岩石学报》2002,18(3):275-292

八达岭杂岩侵位于华北北部，由辉长闪长岩岩、石英闪长岩、石英二长岩、二长闪长岩、二长花岗岩、碱长花岗岩和石英正长岩等组成，主要属高钾钙碱性系列。除了含V-Ti磁铁矿的堆晶辉长闪长岩，整套岩石的主量元素变化范围较大，SiO2=46.5%-75.3%,MgO=5.6%-0.2%，中酸性岩石的K2O/NaO为0.59-1.09。碱长花岗岩和少数石英二长岩Ba和Sr含量较低，且具有明显（Eu）负异常。大多数中酸性岩石（高Ba-Sr花岗岩）具有如下显著的微量元素地球化学特征：Ba,Sr和轻稀土（LREE）富集，Y和重稀土（HREE）亏损，LREE/HREE强烈分离，Sr/Y和La/Yb比值较高；在原始地幔标准化的蛛网图中具有显著的Nb,Ta和Ti亏损，不具明显的Sr和Eu亏损。在Harker图解中，基性岩石和高Ba-Sr花岗岩的主量元素相关性明显，两者还具有相似的微量元素和稀土（REE）分配特征，并且，REE,Y,Sr,P和Ti含量从基性到酸性逐渐降低。辉长闪长岩和高Ba-Sr花岗岩的Sr-Nd同位素初始值呈EMI特征（Isr=0.7051-0.7068,εNdi=-8.2-20.2），大致呈负相关。地球化学特征表明基性岩浆为富集的大陆岩石圈地幔部分熔融形成，而高Ba-Sr花岗岩则为基性岩浆通过陆壳混染和结晶分离形成；富P和Ti的副矿物（如磷灰石和的榍石）的分离结晶导致了REE,P和Ti丰度的逐渐降低。另外，华北板块内部和大别-苏鲁造山带基性岩和高Ba-Sr花岗岩分别具有相似的地球化学特征，这表明，上述地区燕山期大规模岩浆活动具有相似的地球动力学机制，大别-苏鲁造山带岩浆岩的地球化学特征并不反映其地幔源区一定受到过来自深俯冲的扬子板块的流体的富集作用。岩石圈的拆沉和减簿作用可能导致了华北板块和大别-苏鲁造山带下古老岩石圈地幔的部分熔融，岩石圈地幔的富集作用可能主要性发生于元古代。  相似文献