塔里木盆地西北缘震旦系玄武质岩墙和西南缘奥陶系中辉绿岩脉地质年代及构造环境的对比研究          下载免费PDF全文

钱一雄  张洪安杨圣彬李慧莉雷明陈  跃贾存善邵志兵 《地质科学》2017,(4):1079-1096

本文对塔西北震旦系中的苏盖特布拉克组玄武质岩墙以及塔西南奥陶系玛列兹肯群中辉绿岩脉的区域地质、岩石学、地球化学等进行了对比研究,同时对锆石的微区 U-Pb 同位素年代学及其构造环境等进行了研究。 前者为顺层侵入、包裹了中酸性的捕虏体, 发育了枕状构造、球形风化和柱状节理等玄武岩喷发等特征;后者穿插于韧性剪切带中碳酸盐质糜棱岩化中。 它们的常量组分变化较大：不包括 SiO₂ 外其它 9 种常量组分的含量为 36.3%～45.3%, 全碱 （Na₂O+K₂O）为 3.83%～7.16%;TiO₂ 含量较低, 为 0.63%～1.89%;MgO 为 3.72%～6.74%;前者中的常量组分、微量元素 Sr 、Ta、Nb、Ti、Yb、Ni、Cu、Zn、Y 含量明显高于后者对应值, 但大离子亲石、造岩元素中 Cs、Rb 等元素、La/Nb、K/T 元素比相对较低。 相比于原始地幔, 两者均相对富集造岩元素 Li、Rb、Ba、Ga、Sr 和稀有元素 Nb、Ta, 轻稀土中等富集;相对亏损铁族元素 Cr、Co 及 Mo、Pb、Bi、U 等;前者 ΣREE 为 227.72×10^-6～426.32×10^-6 、L/H = 2.51～2.61、δEu = 0.48～0.52、δCe = 0.56;后者的 ΣREE 为 142.37×10^-6 ～187.92×10^-6 、L/H = 2.34～3.99、δEu = 0.63～0.84、δCe = 0.52～0.54;综合判识表明, 前者主要来自于未混染或较弱混染的幔源、发育于新元古（878～808.6 Ma）板内伸展的构造环境, 变质和残留核锆石谐和年龄为 2 090 Ma, 记录了早元古的联合大陆的形成时代, 蚀变锆石 455.4±10.8 Ma 代表了加里东中晚期的岩浆热事件;后者岩浆锆石的 U-Pb 年龄为晚奥陶世 478±48 Ma, 发育于弧后盆地、与韧性剪切带有关的加里东中晚期岩浆活动。  相似文献   

库鲁克塔格基性岩墙群K—Ar等时年龄测定及其有关问题讨论   总被引：16，自引：1，他引：15  

刘玉琳  张志诚  郭召杰  黄宝玲  穆志国 《高校地质学报》1999,5(1):54-58

新疆库鲁克塔格基性岩墙群的四个样品的Ｋ－Ａｒ表观年龄为４５５－６７３Ｍａ,等时年龄为２８７±１３Ｍａ。这一年龄与近几年报道的沿天山构造带的早二叠世火山岩年龄一致。氩初始值为５０８,在Ｐ型岩浆范围内,结合稀土、微量元素特征,认为岩墙群与地幔热柱有成因联系。  相似文献   

Permian felsic magmatism in the Neoproterozoic Nagar Parkar Igneous Complex of the Malani Igneous Suite: Evidence from zircon U–Pb age     

Hafiz U. Rehman  Tahseenullah Khan  Hao‐Yang Lee  Sun‐Lin Chung  Mamoru Murata  M. Qasim Jan 《Island Arc》2019,28(6)

We report Permian (ca. 272 Ma ±5.4 Ma) felsic dykes that intrude into the Neoproterozoic (ca. 750 Ma) magmatic suite of the Nagar Parkar Igneous Complex (NPIC), the western extension of the Malani Igneous Suite (MIS). The NPIC consists of Neoproterozoic basement amphibolites and granites (riebeckite–aegirine gray granites and the biotite–hornblende pink granites), all of which are intruded by several generations of mafic and felsic dykes. Granitic magmatism occurred in the Late Neoproterozoic (ca. 750 Ma) due to the subduction‐, followed by the rift‐related tectonic regime during the breakup of the Rodinia supercontinent. U–Th–Pb zircon and monazite CHIME age data of 700–800 Ma from the earlier generation porphyritic felsic dykes suggest the dyke intrusion was coeval or soon after the emplacement of the host granites. Our findings of Permian age orthophyric felsic dykes provide new insights for the prevalence of active tectonics in the MIS during late Paleozoic. Textural features and geochemistry also make the orthophyric dykes distinct from the early‐formed porphyritic dykes and the host granites. Our newly obtained age data combined with geochemistry, suggest the existence of magmatism along the western margin of India (peri‐Gondwana margin) during Permian. Like elsewhere in the region, the Permian magmatism in the NPIC could be associated with the rifting of the Cimmerian micro‐continents from the Gondwana.  相似文献   

青岛灵山岛南背来石下白垩统大型砂脉的发现及其形成动力学研究     

钟建华  倪良田  汪立东  宋全友  孙宁亮  宋冠先  薛纯琦  郝兵  邵珠福  毛毳  刘闯  曹梦春 《地质论评》2020,66(6):1457-1475

青岛灵山岛南背来石剖面发育了两层大型不规则砂脉。其主要特征如下：上层大型不规则砂脉呈分散团块状顺黄褐色凝灰质泥岩分布,断续延伸约60 m,宽数米;有17个侵入砂团块。砂团块多呈浅灰色,主要岩性为砂岩、砂砾岩;砂团块直径在1~2 m。砂团块的形态非常复杂,侧向极易尖灭或突然中止。边界与围岩多突变,某些地方与节理发育方向相同。下层大型不规则砂脉浅灰色,主要底部为砂岩、顶部为砂砾岩,呈透镜状顺层产于灰黑色薄层砂泥岩中,均一团块状和边缘含大量泥砾;厚18 m,宽度和高度不详;上层砂脉发育在浅湖中;下层大型不规则砂脉发育在三角洲前缘。与此同时还探讨了上层砂脉的形成的动力学机制,建立了顺层砂脉的形成深度与液化层的深度之间的关系式（h=0.29H）。该公式可以用来预测顺层的侵位深度和寻找砂脉,为含油气盆地砂脉储层预测提供理论依据和新方法。通过流化公式计算获得了形成上层砂脉的流体上侵速度为1.26 m/s。通过本文的论述,进一步为理解灵山岛地区下白垩统的沉积环境和沉积动力学特征提供了新的岩石学证据。  相似文献   

西藏拉萨地块北部晚白垩世晚期基性岩墙的成因:来自锆石U-Pb年代学及地球化学的制约     

于云鹏  王明  解超明  范建军  罗安波  曾孝文 《岩石学报》2020,36(2):443-454

拉萨地块北部阿索地区新发现的晚白垩世晚期基性岩墙对于讨论班公湖-怒江洋盆闭合后的碰撞过程具有重要研究意义。本文报道了阿索地区目思基性岩墙的全岩地球化学组成和LA-ICP-MS锆石U-Pb年龄。研究表明,目思基性岩墙中一组最年轻锆石的U-Pb加权平均年龄为74Ma。岩墙内的辉绿玢岩SiO2含量介于51.90%~53.55%之间,MgO含量介于3.98%~4.97%之间,Mg^#为50.0~57.5,低Cr(51.30×10^-6~79.48×10^-6)和Ni(55.94×10^-6~74.17×10^-6)含量。岩墙具有轻稀土元素富集的特征,明显的负Eu异常。在微量元素方面,富集Ba、Th、U、K等大离子亲石元素富集,亏损Nb、Ta、Ti等高场强元素,并具有Pb的正异常。La/Sm-Sm/Yb投图结果显示基性岩墙来自于尖晶石+石榴石二辉橄榄岩地幔源区1%~5%的部分熔融,并在演化过程中发生了橄榄石、单斜辉石及斜长石的结晶分异,同时在岩浆上升过程中受到地壳混染。结合区域地质背景,拉萨地块与羌塘地块碰撞后下地壳增厚并发生榴辉岩化,导致拆沉作用。目思基性岩墙的锆石U-Pb年龄表明拆沉作用持续到晚白垩世晚期。  相似文献   

快速筑堤技术——鲎式轻质堤坝的结构和筑堤方法     

陶松垒  傅晓航 《海洋学研究》2006,24(Z1):83-90

针对软基堤坝稳定性差,容易沉陷滑移,土石方堆不上,工期长,无法快速施工等问题,提出了鲎式轻质堤坝结构和筑堤方法,又称"松垒筑堤法".它减轻了易沉陷部位的质量,均衡堤坝荷重,增强整体稳定性,提高强度,使堤坝与地基溶为一体,消除了堤坝的不均匀沉降;是一种在软弱地基上应用仿生结构的筑堤方法.  相似文献   

湖南板溪脉岩的年代学、岩石学、地球化学及其构造环境   总被引：9，自引：0，他引：9  

赵军红  彭建堂  胡瑞忠  符亚洲 《地球学报》2005,26(6):525-534

湘中地区的锑(金)成矿多与脉岩相伴生,对其成因及对矿床成矿作用的贡献至今仍不清楚。本文通过对板溪石英斑岩脉的研究表明,全岩KAr年龄为200Ma±,至少比板溪锑矿成矿晚200Ma,因此脉岩与成矿不存在成因联系。板溪脉岩显示过铝质特征,其A/CNK为1.08～2.61,A/NK为1.08～2.71,K2O为0.9%～3.66%,K2O+Na2O为4.28%～7.5%,大多数样品的K2O/Na2O小于1。稀土元素以相对富集LREE,LREE分馏不明显、HREE分馏明显,配分曲线右倾为特点,其(La/Yb)n为14.47～28.11,(Gd/Yb)n为9.8～14.3,并且具强负Eu异常,δEu为0.05～0.14,这表明岩石在成岩演化过程中,经历了强的分异结晶作用。在原始地幔标准化蛛网图上,脉体相对富集LILE,并具Ti和P负异常。(87Sr/86Sr)i变化范围较大,为0.6653～0.7149,其中B3样品的(87Sr/86Sr)i为0.7149,与来自地壳上部的花岗岩的87Sr/86Sr初始比值相当。在构造环境判别图中,样品显示岛弧/同碰撞花岗岩的特点。结合前人的研究成果,笔者推测板溪脉岩为地壳上部岩石部分熔融的产物,并经历了混染和高度的分异演化。其动力来源为200Ma左右,地壳叠置加厚作用后幔源岩浆的底侵作用。  相似文献   

Dating synmagmatic folds: a case study of Schlingen structures in the Strona-Ceneri Zone (Southern Alps, northern Italy)   总被引：1，自引：0，他引：1  

R. ZURBRIGGEN  B. S. KAMBER  M. R. HANDY  & T. F. NÄGLER 《Journal of Metamorphic Geology》1998,16(3):403-414

The Strona-Ceneri Zone (Southern Alps) contains folds with moderately to steeply inclined axial planes and fold axes, and amplitudes of up to several kilometres (so-called 'Schlingen'). These amphibolite facies folds deform the main schistosity of Late Ordovician metagranitoids and are discordantly overlain by unmetamorphic Permian sedimentary rocks. Mutually cross-cutting relationships between these folds and garnet-bearing leucotonalitic dykes indicate that these dykes were emplaced during folding. Sm–Nd systematics and the strongly peraluminous composition of these dykes point to an anatectic origin. Pb step leaching of magmatic garnet from a leucotonalitic dyke yielded a 321.3±2.3  Ma intrusive age. Rb–Sr ages on muscovites from leucotonalitic dykes range from 307 to 298  Ma, interpreted as cooling ages during retrograde amphibolite facies metamorphism. Conventional U–Pb data of zircons from an older granodioritic dyke that pre-dates the Schlingen folds yielded discordant U–Pb ages ranging from 371 to 294  Ma. These ages reflect a more complicated multi-episodic growth history which is consistent with the observed polyphase structural overprint of this dyke. Schlingen folding was accompanied by prograde amphibolite facies metamorphism, during the thermal peak of which the leucotonalitic dyke material was generated by partial melting in a deeper source region from where these S-type magmas intruded the presently exposed level. Because partial melting may occur in a relatively late stage of a clockwise P–T–t path, or even during decompression on the retrograde path, we do not exclude the possibility that Schlingen folding had already started in Early Carboniferous time. Schlingen folds also occur in Penninic and Austroalpine basement units with a very similar pre-Alpine history, indicating that Variscan folding affected large segments of the future Alpine realm.  相似文献   

Radial patterns of bitumen dykes around Quaternary volcanoes,provinces of northern Neuquén and southernmost Mendoza,Argentina     

《Journal of South American Earth Sciences》2014

Where the Neuquén Basin of Argentina abuts the Andes, hundreds of veins of solid hydrocarbon (bitumen) are visible at the surface. Many of these veins became mines, especially in the last century. By consensus, the bitumen has resulted from maturation of organic-rich shales, especially the Vaca Muerta Fm of Late Jurassic age, but also the Agrio Fm of Early Cretaceous age. To account for their maturation, recent authors have invoked regional subsidence, whereas early geologists invoked magmatic activity. During 12 field seasons (since 1998), we have tracked down the bitumen localities, mapped the veins and host rocks, sampled them, studied their compositions, and dated some of them. In the provinces of northern Neuquén and southernmost Mendoza, the bitumen veins are mostly sub-vertical dykes. They tend to be straight and continuous, crosscutting regional structures and strata of all ages, from Jurassic to Palaeocene. Most of the localities lie within 70 km of Tromen volcano, although four are along the Rio Colorado fault zone and another two are at the base of Auca Mahuida volcano. On both volcanic edifices, lavas are of late Pliocene to Pleistocene age. Although regionally many of the bitumen dykes tend to track the current direction of maximum horizontal tectonic stress (ENE), others do not. However, most of the dykes radiate outward from the volcanoes, especially Tromen. Thicknesses of dykes tend to be greatest close to Tromen and where the host rocks are the most resistant to fracturing. Many of the dykes occur in the exhumed hanging walls of deep thrusts, especially at the foot of Tromen. Here the bitumen is in places of high grade (impsonite), whereas further out it tends to be of medium grade (grahamite). A few bitumen dykes contain fragments of Vaca Muerta shale, so that we infer forceful expulsion of source rock. At Curacó Mine, some shale fragments contain bedding-parallel veins of fibrous calcite (beef) and these contain some bitumen, which is geochemically of low grade. In contrast, a large crosscutting bitumen dyke is of higher grade and formed later. At other localities, near basement faults, bitumen dykes have cap-rocks of hydrothermal calcrete. Other dykes or their wall rocks contain hydrothermal minerals. Finally, some dykes splay upward towards the current land surface. We conclude that (1) the bitumen dykes formed during volcanic activity in Pliocene–Pleistocene times, and that (2) heat advection by hydrothermal fluids helped to generate oil, which migrated upwards or downwards from the source rock and filled intrusive veins, before solidifying to bitumen, by loss of volatile elements. This unconventional hydrocarbon system may have significant implications for regional exploration in the foothills of the Andes.  相似文献   

北阿尔金拉配泉米兰群片麻岩及其中两期基性岩墙群LA-ICP-MS锆石U-Pb年龄及地质意义   总被引：2，自引：1，他引：1  

刘函  王国灿 《地质通报》2012,31(9):1461-1468

北阿尔金拉配泉北侧米兰群混合角闪斜长片麻岩被2期基性岩墙群(辉绿玢岩和棕闪煌斑岩)侵位。本次分别对三者进行了LA-ICP-MS锆石U-Pb同位素侧年。混合岩化角闪斜长片麻岩中锆石结晶年龄为2007Ma±25Ma,结合西北地区2.0Ga左右广泛的构造-热事件,可能与Columbia超大陆汇聚有关。辉绿玢岩和棕闪煌斑岩的年龄结构相似,锆石较老年龄组分分别为1962～2093Ma和1804～2038Ma,系在侵位时从围岩(混合角闪斜长片麻岩)中捕获的锆石的年龄;最年轻的年龄组分(79～94Ma)代表基性岩墙群的侵位时间,与阿尔金北缘断裂伸展活动有关;古生代年龄(288～504Ma)为岩墙群上侵过程中同化混染北阿尔金蛇绿混杂岩带部分岩石的年龄。  相似文献