Zircon U–Pb–Hf isotopes and geochemistry analyses of the Huyu igneous rocks in northwestern Beijing,China: possible new evidence for the initial destruction of the North China Craton     

Zejia Ji  Baofu Han  Haifei Yu  Yan Chen 《International Geology Review》2018,60(2):196-216

The timing and extent of cratonic destruction are crucial to understanding the crustal evolution of the North China Craton (NCC). Zircon U–Pb–Hf isotope data and the whole-rock major and trace element characteristics of the Huyu igneous rocks in northwestern Beijing, China, provide possible new evidence for the initial destruction of the NCC. The igneous rocks occur as several sills and dikes, including lamprophyre, monzonite porphyry, and aplite. The lamprophyres have high Mg^# and K₂O contents. The monzonite porphyries have high Mg^#, high K₂O contents, and negative ε_Hf(t) values with zircon U–Pb ages of 225.5–227.7 Ma. These two types of rocks are both enriched in large ion lithosphere elements (LILEs) and light rare earth elements (LREEs) but are depleted in high field strength elements (HFSEs) and high rare earth elements (HREEs) and have almost no Eu anomalies and relatively high total rare earth element (ΣREE) contents. In contrast, the aplites exhibit high silica and K₂O contents, low MgO contents, and more negative ε_Hf(t) values with a zircon U–Pb age of 206.2 Ma. The aplites are also enriched in LILEs and LREEs but are depleted in HFSEs and HREEs, with strongly negative Eu, Ti, P, La, Ce, and Sr anomalies and relatively low ΣREE contents. These results indicate that the lamprophyres and monzonite porphyries represent a continuous cogenetic magma evolution series after melt derived from an enriched metasomatized lithospheric mantle experienced crust assimilation and fractional crystallization. The aplites were produced by the fractional crystallization of low-Mg parental magma derived from melting of the ancient Archaean crust. The occurrence of the Huyu intrusive rocks with many other plutons of similar ages on the northern margin of the NCC suggests that the northern NCC entered an intraplate extensional tectonic environment in the Late Triassic.  相似文献   

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)     

Emily Keeble  David I. Whiteside  Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):99-119

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.  相似文献   

Early Carboniferous ophiolite in central Qiangtang,northern Tibet: record of an oceanic back-arc system in the Palaeo-Tethys Ocean     

Tian-Yu Zhang  Cai Li  Chao-Ming Xie  Ming Wang  Yan-Wang Wu 《International Geology Review》2018,60(4):449-463

Zircon U–Pb dating of two samples of metagabbro from the Riwanchaka ophiolite yielded early Carboniferous ages of 354.4 ± 2.3 Ma and 356.7 ± 1.9 Ma. Their positive zircon εHf(t) values (+7.9 to +9.9) indicate that these rocks were derived from a relatively depleted mantle. The metagabbros can be considered as two types: R1 and R2. Both types are tholeiitic, with depletion of high-field-strength elements (HFSE) and enrichment of large-ion lithophile elements (LILE) similar to those of typical back-arc basin basalts (BABB), such as Mariana BABB and East Scotia Ridge BABB. Geochemical and isotopic characteristics indicate that the R1 metagabbro originated from a back-arc basin spreading ridge with addition of slab-derived fluids, whereas the R2 metagabbro was derived from a back-arc basin mantle source, with involvement of melts and fluids from subducted ocean crust. The Riwanchaka ophiolite exhibits both mid-ocean ridge basalts- and arc-like geochemical affinities, consistent with coeval ophiolites from central Qiangtang. Observations indicate that the Qiangtang ophiolites developed during the Late Devonian–early Carboniferous (D₃–C₁) in a back-arc spreading ridge above an intra-oceanic subduction zone. Based on our data and previous studies, we propose that an oceanic back-arc basin system existed in the Longmuco–Shuanghu–Lancang Palaeo-Tethys Ocean during the D₃–C₁ period.  相似文献   

A New Ootype of Dinosaur Egg (Faveoloolithidae: Duovallumoolithus shangdanensis oogen. et oosp. nov.) from the Late Cretaceous in the Shangdan Basin,Shaanxi Province,China     

ZHENG Tingting  BAI Yi  WANG Qiang  ZHU Xufeng  FANG Kaiyong  YAO Yuan  ZHAO Yongqiang  WANG Xiaolin 《《地质学报》英文版》2018,92(3):897-903

A new ootype collected from the Upper Cretaceous Lijiacun Formation in the Shangdan Basin, Shaanxi Province is described in this paper. Based on general external shape, size, eggshell thickness and honeycomb‐like eggshell microstructure, eggs are referable to the oofamily Faveoloolithidae. Compared with other members of Faveoloolithidae, specimens described in this paper show special characteristics: adjacent pores are usually separated by two eggshell units between which often develop interspaces; columnar eggshell units are relatively closely arranged in radial view. According to these characteristics, we erect a new oogenus and a new oospecies: Duovallumoolithus shangdanensis oogen. et oosp. nov. The new discovery expands the diversity of Faveoloolithidae.  相似文献   

The Late Triassic I–Type Granites from the Longmu Co–Shuanghu Suture Zone in the interior of Tibetan Plateau, China: Petrogenesis and Implication for Slab Break–Off     

ZHAO Zhen  WU Zhenhan  LU Lu  YU Junqiu  WU Yanjun 《《地质学报》英文版》2018,92(3):935-951

The Jiangaidarina granitic mass(JM) is an important part of the magmatic belt in Longmu CoShuanghu Suture Zone(LSSZ) in the central Tibetan Plateau. An integrated research involving wholerock geochemistry, zircon LA-ICP-MS U-Pb ages and Hf isotopic compositions was carried out to define the timing, genesis and tectonic setting of the JM. Zircon LA-ICP-MS U-Pb ages have been obtained ranging from 210 to 215 Ma, rather than the Early Jurassic as previously thought. Fifteen granite samples contain hornblendes and show a negative correlation between P_2 O_5 and SiO_2, indicating that the JM is an I-type granite. All the granites are enriched in LREE relative to HREE, with negative Eu anomalies(Eu/Eu*=0.56-0.81), and have similar trace elements patterns, with depletion of Ba, Nb, Sr and P. These suggest that the JM was fractionated, and this is also proved by the characteristic of negative correlations between oxide elements(TiO_2, MgO, FeOt, MnO, CaO) and SiO_2. Almost all ε_(Hf)(t) values of the granites are between-10.3 and-5.8, implying that the JM has a crustal source intimately related with the South Qiangtang Block(SQB), except for one(+10.2), showing a minor contribution from mantle source.Moreover, relatively low Na_2 O/K_2 O ratios(0.42-0.93) and high A/CNK values(0.91-1.50) reflect that the JM was predominately derived from the medium-high potassium basaltic crust, interacted with greywacke. Our new geochemical data and geochronological results imply that the Late Triassic magmas were generated in a post-collisional tectonic setting, probably caused by slab break-off of the Longmu Co-Shuanghu Tethyan Ocean(LSTO). This mechanism caused the asthenosphere upwelling, formed extension setting, offered an enormous amount of heat, and provided favorable conditions for emplacement of voluminous felsic magmas. Furthermore, the LSTO could be completely closed during the Middle Triassic, succeed by continental collision and later the slab broke off in the Late Triassic.  相似文献   

Late Cenozoic Sedimentary Evolution of Pagri‐Duoqing Co graben,Southern End of Yadong‐Gulu Rift,Southern Tibet   总被引：1，自引：0，他引：1  

HA Guanghao  WU Zhonghai  HE Lin  WANG Shubing 《《地质学报》英文版》2018,92(3):972-987

The north trending rifts in southern Tibet represent the E–W extension of the plateau and confirming the initial rifting age is key to the study of mechanics of these rifts. Pagri–Duoqing Co graben is located at southern end of Yadong–Gulu rift, where the late Cenozoic sediments is predominately composed of fluvio-lacustrine and moraine. Based on the sedimentary composition and structures, the fluvio-lacustrine could be divided into three facies, namely, lacustrine, lacustrine fan delta and alluvial fan. The presence of paleo-currents and conglomerate components and the provenance of the strata around the graben indicate that it was Tethys Himalaya and High Himalaya. Electron spin resonance (ESR) dating and paleo-magnetic dating suggest that the age of the strata ranges from ca. 1.2 Ma to ca. 8 Ma. Optically stimulated luminescence (OSL) dating showed that moraine in the graben mainly developed from around 181–109 ka (late Middle Pleistocene). Combining previous data about the Late Cenozoic strata in other basins, it is suggested that 8–15 Ma may be the initial rifting time. Together with sediment distribution and drainage system, the sedimentary evolution of Pagri could be divided into four stages. The graben rifted at around 15–8 Ma due to the eastern graben-boundary fault resulting in the appearance of a paleolake. Following by a geologically quiet period about 8–2.5 Ma, the paleolake expanded from east to west at around 8–6 Ma reaching its maximum at ca. 6 Ma. Then, the graben was broken at about 2.5 Ma. At last, the development of the glacier separated the graben into two parts that were Pagri and Duoqing Co since the later stages of the Middle Pleistocene. The evolution process suggested that the former three stages were related to the tectonic movement, which determined the basement of the graben, while the last stage may have been influenced by glacial activity caused by climate change.  相似文献   

松辽盆地西斜坡中—晚二叠世古沉积环境演化及油气地质意义     

何大双  吕琴音  张耀阳  张鹏辉  裴发根  张小博 《地质学报》2023,97(2):507-522

大兴安岭南部—松辽盆地西斜坡晚二叠世古沉积环境一直以来备受争议,关于该地区中—晚二叠世古环境演化方面的研究也鲜见报道。本文采用元素地球化学和有机地球化学相结合的研究方法,对松辽盆地西斜坡蒙科地1井中—晚二叠世古沉积环境演化特征进行综合研究。结果表明,中二叠世为明显的海相沉积,沉积水体相对较深,期间可能存在多次干热—暖湿波动,其中中二叠世ZSI晚期—ZSII早期较为明显,水体性质体现为咸水—微咸水—半咸水,水体还原性—偏氧化性—还原性,气候干热—温湿—干热。晚二叠世早期为微咸水—半咸水海相沉积,至晚二叠世晚期转变为淡水—微咸水海陆过渡相沉积,期间存在两次明显的气候环境波动,与中二叠世哲斯组沉积中期气候环境变化相似,表现为水体变浅、咸度降低、还原性减弱,气候由干热转向温湿。晚二叠世以来气候逐渐向温暖湿热转变,水体逐渐变浅,可能与二叠纪—三叠纪之交气候变暖有关。至三叠纪、侏罗纪时期,区域处于构造抬升阶段,沉积环境由海陆过渡相环境转变为陆相沉积。结合TOC、古生产力指标分析得出,中二叠世ZSI晚期—ZSII2早期、晚二叠世LXI晚期、晚二叠世LXII中期、晚二叠世LXIII沉积期偏湿润的气候条件和低咸度、弱还原—偏氧化性的沉积水体环境,是形成厚度较大、富有机质烃源岩的有利的气候环境条件。  相似文献   

东昆仑拉陵高里河沟脑地区晚三叠世花岗闪长斑岩年代学、岩石地球化学及Hf同位素特征     

刘建栋  张焜  王秉璋  王春涛  李五福  张新远  曹锦山  袁锦鹏  李青  陈丽娟 《地质论评》2023,69(1):2023010019-2023010019

本文对东昆仑拉陵高里河沟脑花岗闪长斑岩开展详细的全岩地球化学、LA- ICP- MS锆石U- Pb年代学、锆石Hf同位素研究,确定其形成时代,并探讨其岩石成因及成岩构造背景。结果显示,花岗闪长斑岩LA- ICP- MS锆石U- Pb年龄为231. 1±1. 2 Ma,指示其侵位于晚三叠世早期。全岩K2O/Na2O值为0. 69～0. 71,Mg#值为40. 5～41. 6,里特曼指数σ为1. 90～2. 09,A/CNK=1. 01～1. 03,属弱过铝质中—高钾钙碱性岩石系列。岩石的轻重稀土元素分异明显,(La/Yb)N值为19. 54～25. 52,具弱负Eu异常（δEu为0. 96～0. 97）,富集大离子亲石元素K、Rb、Ba、Th,亏损高场强元素Nb、Ta、Ti等,具有高的Sr含量(606. 0×10-6～647. 9×10-6)和Sr/Y值(60. 38～62. 99),较低的Y(9. 62×10-6～10. 66×10-6)和Yb(0. 86-6～0. 92×10-6)含量,显示Adakite（高锶低钇中酸性岩）的地球化学特征。锆石Hf同位素εHf(t)值介于-6. 93~-2. 94,地壳模式年龄（TDM2）范围为1. 45~1. 70 Ga。综合分析表明,拉陵高里河沟脑花岗闪长斑岩形成于东昆仑洋壳俯冲末期至局部碰撞的转换阶段,岩浆源于高压条件下的加厚下地壳部分熔融。  相似文献   

晚更新世以来珠江三角洲钻孔年代及沉积演化     

林鹏辉  李宏卫  詹伟琪  凌恳  宋盈瑾  徐晓琳  赖忠平 《地质论评》2023,69(Z1):333-335

  相似文献   

华北克拉通奥陶纪岩浆活动——来自河南安阳岭头地区白垩纪闪长岩中继承锆石U- Pb年龄的证据     

杨长青  巴燕  王艳慧  何凯  白国典 《地质论评》2023,69(3):1150-1160

通过高精度的LA-ICP-MS锆石U-Pb同位素测年,在太行山南段河南安阳县岭头一带白垩纪闪长质侵入岩中获得一批443.6±6.1 Ma(MSWD=6.3)的年龄数据,相当于晚奥陶世晚期,这是在华北克拉通内部发现的首例反映加里东期岩浆侵入活动的高精度锆石U-Pb定年数据,为揭示华北克拉通早古生代构造岩浆演化提供了依据。结合区域上同期构造岩浆事件的特点,认为443.6±6.1Ma的锆石可能为华北克拉通板内裂解拉张作用的产物,它是奥陶纪晚期(440 Ma前后)古劳亚大陆分裂,华北克拉通漂离加拿大地盾和北美内陆地台,同时形成北太平洋——这一影响全球的构造地质事件在华北克拉通内部的响应。鉴于稳定克拉通地区奥陶纪岩浆侵入活动与金刚石原生矿存在极高的关联度,本次发现也为在鹤壁地区寻找金刚石原生矿提供了重要参考。  相似文献