阿尔金碰撞造山带西段的构造特征   总被引：13，自引：2，他引：13  

覃小锋　李江陆济璞  许华胡贵昂  周府生李乾 《地质通报》2006,25(1):104-112

根据阿尔金山西段前早古生代变质岩的岩石组成、沉积建造、变形变质作用改造历史、岩石地球化学特征等研究,将阿尔金碰撞造山带西段划分为3个构造单元:北阿尔金地块、中阿尔金地块(包括英格里克构造-蛇绿混杂岩带、肖鲁克·布拉克高压变质岩带和塔什萨依玉石矿高绿片岩相-低角闪岩相变质岩带)和南阿尔金地块(包括南阿尔金中-新元古界隆起带和阿尔金南缘复合构造-蛇绿混杂岩带).提出该碰撞造山带经历了前长城纪古陆核形成阶段、长城纪-青白口纪不同基底联合阶段和早古生代洋陆转换阶段3个阶段的构造演化.  相似文献   

阿尔金碰撞造山带西段的构造特征     

覃小锋  李江  陆济璞  许华  胡贵昂  周府生  李乾 《地质通报》2006,(Z1)

根据阿尔金山西段前早古生代变质岩的岩石组成、沉积建造、变形变质作用改造历史、岩石地球化学特征等研究,将阿尔金碰撞造山带西段划分为3个构造单元:北阿尔金地块、中阿尔金地块(包括英格里克构造-蛇绿混杂岩带、肖鲁克·布拉克高压变质岩带和塔什萨依玉石矿高绿片岩相—低角闪岩相变质岩带)和南阿尔金地块(包括南阿尔金中—新元古界隆起带和阿尔金南缘复合构造-蛇绿混杂岩带)。提出该碰撞造山带经历了前长城纪古陆核形成阶段、长城纪—青白口纪不同基底联合阶段和早古生代洋陆转换阶段3个阶段的构造演化。  相似文献   

Petrological and geochronological constraints on the origin of the Palimé–Amlamé granitoids (South Togo, West Africa): A segment of the West African Craton Paleoproterozoic margin reactivated during the Pan-African collision     

Y. Agbossoumond  R.-P. Mnot  J.L. Paquette  S. Guillot  S. Yssoufou  C. Perrache 《Gondwana Research》2007,12(4):476-488

The Palimé–Amlamé Pluton (PAP) in southern Togo, consists of silica-rich to intermediate granitoids including enclaves of mafic igneous rocks and of gneisses. They are commonly called the “anatectic complex of Palimé–Amlamé” and without any convincing data, they were interpreted either as synkinematic Pan-African granitoids or as reworked pre Pan-African plutons. New field and petrological observations, mineral and whole-rock chemical analyses together with U–Pb zircon dating, have been performed to evaluate the geodynamic significance of the PAP within the Pan-African orogenic belt. With regard to these new data, the granitoids and related enclaves probably result from mixing and mingling processes between mafic and silicic magmas from respectively mantle and lower crust sources. They display Mg–calc-alkaline chemical features and present some similarities with Late Archaean granites such as transitional (K-rich) TTGs and sanukitoids.

The 2127 ± 2 Ma age obtained from a precise U/Pb concordia on zircon, points out a Paleoproterozoic age for the magma crystallization and a lower intercept at 625 ± 29 Ma interpreted as rejuvenation during Pan-African tectonics and metamorphism. Based on these results, a Pan-African syn to late orogenic setting for the PAP, i.e. the so-called “anatectic complex of Palimé–Amlamé”, can be definitively ruled out. Moreover according to its location within the nappe pile and its relationships with the suture zone, the PAP probably represents a fragment of the West African Craton reactivated during the Pan-African collision.  相似文献   

Early cretaceous granitoids and their implications for the collapse of the Dabie orogen, eastern China: SHRIMP zircon U–Pb dating and geochemistry     

Haijin Xu  Changqian Ma  Kai Ye   《Chemical Geology》2007,240(3-4):238-259

Two stages of early Cretaceous post-orogenic granitoids are recognized in the Dabie orogen, eastern China, which recorded processes of extensional collapse of the orogen. The early stage granitoids ( 132 Ma) are foliated hornblende quartz monzonites and porphyritic monzogranites. They are of high-K calc-alkaline series and metaluminous to weakly peraluminous, with high K₂O and low MgO contents (Mg^# values: 32.0–46.0), they contain high Sr, low Y and heavy rare earth elements (HREE), and have high Sr/Y and (La/Yb)_N ratios, without clear negative Eu, Sr and Ti anomalies. The early stage deformed granitoids have adakitic geochemical compositions and are equilibrated with residues rich in garnet and poor in anorthite-rich plagioclase, and thus indicate the existence of an over-thickened (> 50 km) crustal root beneath the orogen at  132 Ma. The later stage granitoids ( 128 Ma) are undeformed fine-grained monzogranites, fine-grained K-feldspar granites and coarse-grained K-feldspar granite-porphyry. They belong to a peraluminous and high-K calc-alkaline to shoshonite series, and display a flat HREE pattern and have strong negative Eu, Sr and Ti anomalies, with low Sr/Y and (La/Yb)_N ratios. The late stage granitoids are equilibrated with residues rich in anorthite-rich plagioclase, hornblende, ilmenite/titanite and poor in garnet, indicating that the crust of the Dabie orogen became thinner (< 35 km) at  128 Ma. SHRIMP zircon U–Pb ages and changing compositional trends for these two stages of granitoids indicate that the over-thickened crust formed by the Triassic continental subduction/collision under the Dabie orogen remained until the early Cretaceous, and collapsed quickly in a few million years during the early Cretaceous.  相似文献   

大陆科学钻探先导孔（CCSD—P1）橄榄岩地幔属性及动力学意义     

郑建平汤华云  张志海余淳梅张瑞生  路凤香杨经绥 李天福 《现代地质》2007,21(2):275-285

早中生代的扬子大陆向华北大陆的深俯冲碰撞作用以及中、新生代的华北东部岩石圈减薄作用是国际大陆动力学问题研究的两个热点。然而，把它们有机联系起来，探讨深部岩石圈演化动力学过程的研究还很少。报道了中国大陆科学钻探先导孔（CCSD-PP1）橄榄岩的矿物岩石化学分析结果。这些橄榄岩亏损玄武质组分（如低w（CaO＋Al2O3）、高Mg^#等），并经历了中元古代来自软流圈的碳酸岩熔体的交代作用和早中生代的超高压再平衡过程。结合已发表的华北捕虏体橄榄岩资料，对这一橄榄岩的原始地幔属性进行了分析。发现CCSD-PP1橄榄岩与华北古老岩石圈地幔组成相似，是早中生代来自华北岩石圈的构造侵入体。早中生代华北岩石圈的伸展减薄与苏鲁超高压变质岩石的折返提供了早期软流圈物质上涌的构造体制。  相似文献   

大别山超高压榴辉岩和花岗片麻岩中锆石Lu-Hf同位素研究   总被引：2，自引：11，他引：2  

郑永飞陈仁旭  张少兵唐俊赵子福  吴元保 《岩石学报》2007,23(2):317-330

对大别山超高压榴辉岩和花岗片麻岩进行了锆石Lu-Hf同位素分析,结果为原岩来源提供了制约,表明扬子陆块在Rodinia超大陆裂解时的裂谷岩浆活动中发生了显著的陆壳生长。对这些锆石的不同区域进行的U-Pb和Lu-Hf同位素分析和比较表明,不同成因的锆石在~(206)Pb/~(238)U年龄、初始Hf同位素组成、Th/U及Lu/Hf比值等方面具有明显的差异。与年龄较老的岩浆核部和幔部相比,年轻的变质增生边具有低的Th/U和Lu/Hf比值但高的ε_(Hf)(t)值。不同成因锆石的Th/U和Lu/Hf比值存在着正相关性,表明变质作用对锆石的U-Th-Pb和Lu-Hf同位素体系有着相似的影响。高级变质作用有时能够引起岩浆锆石增生边~(176)Hf/~(177)Hf比值的显著升高,导致变质新生颗粒或增生边类似于新生地壳的高ε_(Hf)(t)值假象。对榴辉岩和片麻岩锆石核部的分析发现,镁铁质和长英质原岩在大约750Ma左右形成一个双峰式火山岩套,另外包含少量的年龄约为2.15Ga的陆壳。初始Hf同位素组成可分成两组:第一组具有正的ε_(Hf)(t)值,为5.9±0.9～12.9±0.7;第二组ε_(Hf)(t)值在零左右,为-4.3±0.5-2.3±0.3。正的ε_(Hf)(t)值与较年轻的模式年龄相对应,负的ε_(Hf)(t)值与古元古代模式年龄相对应。前者表明,在扬子陆块北缘裂谷岩浆作用将亏损地幔物质加入到大陆地壳中,同时在新元古代中期的裂谷构造带中存在同时期的壳-幔相互作用。因此,在扬子陆块北缘新元古代中期裂谷岩浆活动中,既有新生地壳生长和即时再造,也有古老地壳再造。  相似文献   

辽西地区燕山板内造山带早中生代构造变形的年代学限定   总被引：4，自引：0，他引：4  

胡健民刘晓文  杨之青 《岩石学报》2007,23(3):605-616

在辽西进行的构造研究确认了这里曾经在早中生代期间发生过几次重要的构造变形事件,地质上,这几次构造变形的时代被限定在中三叠世老虎沟组沉积之后到晚侏罗世髫髻山/蓝旗组火山岩喷发之前。期间,第一期逆冲推覆构造被水泉沟组不整合覆盖,第二期逆冲推覆构造被髫髻山组/蓝旗组不整合覆盖。本文通过对水泉沟组火山岩、邓杖子组火山岩砾石、髫髻山组底部火山岩以及侵位到逆冲构造岩片中的安山玢岩脉体进行锆石SHRIMP法U-Pb定年,比较准确地限定了燕山板内造山带早中生代几次构造变形的时代。这对于研究燕山板内造山带早期变形特征和变形历史、研究整个燕山造山带的变形过程都具有重要的意义。  相似文献   

Ultrahigh-pressure eclogite transformed from mafic granulite in the Dabie orogen, east-central China   总被引：1，自引：0，他引：1  

Y.-C. LIU  S.-G. LI  X.-F. GU  S.-T. XU  G.-B. CHEN 《Journal of Metamorphic Geology》2007,25(9):975-989

Although ultrahigh‐pressure (UHP) metamorphic rocks are present in many collisional orogenic belts, almost all exposed UHP metamorphic rocks are subducted upper or felsic lower continental crust with minor mafic boudins. Eclogites formed by subduction of mafic lower continental crust have not been identified yet. Here an eclogite occurrence that formed during subduction of the mafic lower continental crust in the Dabie orogen, east‐central China is reported. At least four generations of metamorphic mineral assemblages can be discerned: (i) hypersthene + plagioclase ± garnet; (ii) omphacite + garnet + rutile + quartz; (iii) symplectite stage of garnet + diopside + hypersthene + ilmenite + plagioclase; (iv) amphibole + plagioclase + magnetite, which correspond to four metamorphic stages: (a) an early granulite facies, (b) eclogite facies, (c) retrograde metamorphism of high‐pressure granulite facies and (d) retrograde metamorphism of amphibolite facies. Mineral inclusion assemblages and cathodoluminescence images show that zircon is characterized by distinctive domains of core and a thin overgrowth rim. The zircon core domains are classified into two types: the first is igneous with clear oscillatory zonation ± apatite and quartz inclusions; and the second is metamorphic containing a granulite facies mineral assemblage of garnet, hypersthene and plagioclase (andesine). The zircon rims contain garnet, omphacite and rutile inclusions, indicating a metamorphic overgrowth at eclogite facies. The almost identical ages of the two types of core domains (magmatic = 791 ± 9 Ma and granulite facies metamorphic zircon = 794 ± 10 Ma), and the Triassic age (212 ± 10 Ma) of eclogitic facies metamorphic overgrowth zircon rim are interpreted as indicating that the protolith of the eclogite is mafic granulite that originated from underplating of mantle‐derived magma onto the base of continental crust during the Neoproterozoic (c. 800 Ma) and then subducted during the Triassic, experiencing UHP eclogite facies metamorphism at mantle depths. The new finding has two‐fold significance: (i) voluminous mafic lower continental crust can increase the average density of subducted continental lithosphere, thus promoting its deep subduction; (ii) because of the current absence of mafic lower continental crust in the Dabie orogen, delamination or recycling of subducted mafic lower continental crust can be inferred as the geochemical cause for the mantle heterogeneity and the unusually evolved crustal composition.  相似文献   

Rational function model for sensor orientation of IRS-P6 LISS-4 imagery     

V. Nagasubramanian    P. V. Radhadevi    R. Ramachandran    R. Krishnan 《The Photogrammetric Record》2007,22(120):309-320

  相似文献   

中国南方中新生代大地构造属性和南华造山带褶皱过程   总被引：35，自引：3，他引：32  

郭福祥 《地质学报》1998,72(1):22-23

笔者阐述了中国南方中新生代大地构造属性是陆上三向造山带,是在陆上无海侵的大地构造环境下,由特提斯,北西太平洋和昆仑－秦岭三大构造域相互作用形成的具有ＮＷ、ＮＥ、ＷＮＷ三向优徒选大地构造线的造山带 ,是由晚二叠世以来多期次继承性造山运动累积辍  相似文献