Ar-Ar geochronology of Late Mesozoic volcanic rocks from the Yanji area, NE China and tectonic implications   总被引：2，自引：0，他引：2  

LI ChaoWen    GUO Feng  FAN WeiMing & GAO XiaoFeng  Key Laboratory of Marginal Sea Geology  Guangzhou institute of Geochemistry  Chinese Academy of Sciences  Guangzhou  China  Graduate University of the Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2007,50(4):505-518

Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined “Triassic-Jurassic” volcanic rocks (including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.) were erupted during 118―106 Ma, corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage (130―120 Ma) of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. were extruded at ca. 55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as: Tuopangou Fm., Sanxianling/Tuntianying Fm. (118―115 Ma), Malugou/Tianqiaoling Fm. (K1), Huoshanyan/Jingouling Fm. (108―106 Ma), Changcai Fm. (K2), Quanshuicun Fm. (~55 Ma) and Dalazi Fm. Our results suggest that subduction of the Pa- laeo-Pacific Ocean beneath the East Asian continental margin occurred during 106 to 55 Ma, consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95―65 Ma.  相似文献   

花岗岩成因研究的若干问题   总被引：124，自引：127，他引：124  

吴福元李献华  杨进辉郑永飞 《岩石学报》2007,23(6):1217-1238

花岗岩是大陆地壳的重要组成,是地质学研究的重要课题。本文对当前花岗岩研究中的几个重要问题进行了讨论,内容包括:(1)花岗岩的成因分类,(2)花岗岩浆起源的温度与压力条件,(3)结晶分异作用与花岗岩成分变化,(4)花岗岩成因与壳幔演化,(5)花岗岩形成的构造环境等。通过分析认为,高分异花岗岩成因类型的确定是比较困难的,在有些情况甚至不可能准确分类。花岗岩的锆饱和温度和锆石钛温度计可对花岗岩浆形成的温度提供重要信息,但花岗岩浆起源的压力条件确定相对困难。花岗岩主要形成于俯冲带或碰撞造山带后造山的拉张构造背景中,在这两种情况下,挥发份和热的加入可使地壳发生部分熔融而形成花岗岩。本文还对我国近年来花岗岩研究的进展情况做了概要性叙述,并就我国东部中生代花岗岩研究的近期突破问题进行了分析。  相似文献   

浙东晚中生代壳幔相互作用的新例证——新昌儒岙辉绿岩-花岗岩复合岩体的年代学与地球化学   总被引：6，自引：4，他引：6  

董传万  徐夕生闫强林秀斌  竺国强 《岩石学报》2007,23(6):1303-1312

在浙东新昌地区,新发现了一个由辉绿岩和花岗岩组成的复合岩体。辉绿岩主要由斜长石(An=45～55,50%～60%)、普通辉石(20%～30%)、普通角闪石(10%～15%)等组成,全岩 Ar-Ar 同位素年龄为109.1±2.8Ma;花岗岩主要由石英(25%～30%),钾长石(50%～60%),斜长石(An=20±,10%～15%)及少量的黑云母(<5%)组成,锆石 SHRIMP U-Pb 年龄值为129～109Ma,其最小年龄值109Ma 与辉绿岩的相同,证明辉绿岩和花岗岩近同时冷凝固结。在岩石地球化学上,它们同属钙碱性岩石系列,具有轻稀土元素和大离子亲石元素富集、高场强元素亏损等特点,稀土元素、微量元素配分型式基本相同,(~(87)Sr/~(86)Sr)_i=0.7074～0.7079,ε_(Nd)(t)=-3.5～-4.4,指示它们的微量元素和同位素发生过充分的交换。这与浙东晚中生代玄武岩-流纹岩复合岩流的相似,也与福建沿海同时代复合火成岩的基本一致。它们是起源于受消减作用影响的岩石圈地幔部分熔融而产生的玄武岩浆底侵,并与深融的壳源花岗岩浆相互作用的结果,是壳幔作用的产物。新昌复合岩体的发现与研究,为研究浙东地区和浙闽沿海的壳幔作用和构造-岩浆作用提供了一个新的实例。  相似文献   

青海西秦岭地区晚中生代基性火山岩地球化学特征及构造意义   总被引：4，自引：0，他引：4  

范立勇  王岳军  李晓勇 《矿物岩石》2007,27(3):63-72

对青海省同仁县多禾茂地区火山岩进行系统的元素同位素地球化学研究表明:该地区白垩纪地层中发育的中基性火山岩,属于碱性火山岩系,岩石类型主要为玄武岩,该套玄武岩具有低且变化较小的Si O2质量分数(44.98%~48.20%),低MgO的质量分数高,变化较大(8.15%~10.98%),具有较高的Cr(208×10-6~418×10-6)和Ni(166×10-6~231×10-6)质量分数。所有样品都表现出轻稀土富集的右倾平滑分布模式,轻重稀土分异中等,(La/Yb)CN=10.09~27.2,重稀土弱分异,(Gd/Yb)CN=2.92~4.67,Eu异常不明显,Eu*/Eu=0.99~1.04。Ba,Nb-Ta和Th-U不亏损,Rb,K相对亏损,Sr正异常。该区火山岩具有亏损的Sr-Nd同位素组成,Sr-Nd同位素组成变化范围不大[87Sr/86Sr(t)=0.7033~0.7039,εNd(t)=6.13~8.03,t=110 Ma],与Hawaii-OIB的Sr-Nd同位素组成相似。其所有地球化学特征表明该火山岩具有类似OIB的特征,可能是含石榴子石橄榄岩低度部分熔融的产物。结合对西秦岭地质构造背景和演化历史的分析,暗示该地区晚中生代岩浆源区来源于软流圈,其起源可能与岩石圈拆沉作用,软流圈地幔上涌和岩石圈伸展减薄有关,可为秦岭大别造山带中生代岩石圈演化提供了有利的直接证据。  相似文献   

Structural framework and Mesozoic–Cenozoic evolution of Ponta Grossa Arch, Paraná Basin, southern Brazil     

Michael Strugale  Sidnei Pires Rostirolla  Fernando Mancini  Carlos Vieira Portela Filho  Francisco Jos Fonseca Ferreira  Rafael Corrêa de Freitas 《Journal of South American Earth Sciences》2007,24(2-4):203-227

  相似文献   

New concepts on the composition, structure, and age of the Lower Amur fragment of the Late Jurassic-Early Cretaceous accretionary prism, Russian Far East     

V. I. Anoikin  G. L. Kirillova  L. P. Eichwald 《Russian Journal of Pacific Geology》2007,1(6):556-571

On the basis of geological observations and the study of conodont and radiolarian microfauna, a new stratigraphic scheme was proposed for the Mesozoic deposits of the Komsomolsk district of the Amur region. The lower Khorpy Group (T₂-J₃) consists of two units: the Boktor (T₂-J₂) and Kholvasi (J_2–3). The Boktor Sequence (400 m thick) is represented by pelagic cherts with an admixture of cherty-clayey shales and volcanic rocks. The Kholvasi Sequence (500 m thick) is built up of the predominant siltstones and clayey shales with rare intercalations and lenses of clayey cherts and cherty-clayey shales. The upper Komsomolskaya Group (K₁) has a terrigenous composition and includes the Gorin, Pionerskaya, and Pivan formations of 5 km total thickness. It is made up of intercalated sandstones, siltstones, mudstones, and often turbidites (proximal to distal). The rocks contain abundant buchia fauna of Volgian-Valanginian age, as well as carbonized plant detritus and flora of the Early Cretaceous habit. The described complex is characterized by a nappe-fold structure typical of the accretionary prisms in the ocean-continent convergence zones. The predominance of the coherent type of accretionary prisms reflects the simple morphology of the oceanic plate.  相似文献   

Evolution of the Mesozoic Granites in the Xiong''ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications          下载免费PDF全文

Franco PIRAJNO 《《地质学报》英文版》2007,81(2)

Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.  相似文献   

寿昌—临浦火山岩带赋矿流纹岩特征及归属雏议     

周家志 《华东地质学院学报》1998,21(3):213-219

本文介绍的火山岩带,有层状流纹岩及穹丘状、岩颈状等非层状流纹岩,分别属溢流相、侵出相及火山管道相,三种流纹岩均受火山岩带核中断裂及晚期火山构造控制,复盖或穿发寿昌组一段地层,又被寿昌组一段之后的次火山岩及隐爆岩所穿切,局部被横山组不整合复盖。该类流纺岩同位素年龄值较小,多数在１３０Ｍａ左右,处于晚侏罗世与早白垩世过渡期。根据其层序、穿切关系及同位素年龄等,认为三种流纹岩均属火山岩带晚期不同岩相的产  相似文献   

二连断陷盆地群伸展构造系统及其发育的深部背景   总被引：14，自引：0，他引：14       下载免费PDF全文

任建业  焦贵浩 《地球科学》1998,23(6):567-572

二连盆地形成于侏罗纪到早白垩世期间,是东北亚断陷盆地系内的一个典型的盆岭式断陷盆地群,其内蕴藏丰富的煤和油气资源,综合分析了二连盆地油气勘探中积累的地质资料,系统地研究了与盆地形成有关的构造,并与北美西部盆岭省进行了对比,揭示了二连盆地宽裂陷作用和低拉伸率条件下的伸展构造系统。以上述研究和前人的研究成果为基础,探讨了盆地发育的深部背景。  相似文献   

内蒙额尔古纳在矿带中生代火山岩浆活动与金属成矿的关系   总被引：1，自引：0，他引：1  

韩丽  李广慧 《岩石矿物学杂志》1998,17(1):9-16

在岩石学和微量元素地球化学研究的基础上,通过对不同类型矿床的成矿岩体及围岩条件的分析,探讨了中生代火山岩浆活动与金属成矿的关系。认为晚侏罗世火山岩浆活动为成矿提供了有利的围岩的构造空间;早白垩世岩浆活动提供了成矿岩体及热力学条件,该期次火山岩浆的侵入并作用于不同的围岩、形成了由斑岩型Ｃｕ、Ｍｏ矿,浅成熟液型Ａｇ、Ｐｂ、Ｚｎ矿等组成的一系列矿床组合。  相似文献