Early Paleozoic gabbro-granitoid associations in eastern segment of the Mongolian-Okhotsk foldbelt (Amur River basin): Age and tectonic position     

A. A. Sorokin  A. B. Kotov  E. B. Sal’nikova  N. M. Kudryashov  V. P. Kovach 《Stratigraphy and Geological Correlation》2007,15(3):241-257

Magmatic rocks of the Pikan and Un’ya massifs situated in eastern segment of the Mongolian-Okhotsk foldbelt are studied using isotopic-geochronological (U-Pb zircon dating) and geochemical methods. Two rock complexes different in age are recognized in the Pikan massif: the high-Al gabbro-tonalite association of the Middle Ordovician (468 ± Ma) and granodiorite-granite association of the Late Silurian-Early Devonian (415 ± 7 Ma). The Late Ordovician age (454 ± 5 Ma) is established for leucocratic granites of the Un’ya massif. As is suggested, the Pikan and Un’ya massifs are “allogenic blocks” detached from continental framework of the Mongolian-Okhotsk foldbelt and tectonically emplaced into the foldbelt structure at the last stage of its development.  相似文献   

A New Specimen of Liaoceratops yanzigouensis (Dinosauria: Neoceratopsia) from the Early Cretaceous of Liaoning Province, China          下载免费PDF全文

YOU Hailu  Kyo TANOUE  Peter DODSON 《《地质学报》英文版》2007,81(6):898-904

A new specimen of basal neoceratopsian dinosaur Liaoceratops yanzigouensis is described. The specimen comes from the Lujiatun Bed of the Lower Cretaceous Yixian Formation in Beipiao City of western Liaoning Province, and is represented by a very well preserved three-dimensional partial skull and mandible. It is also the smallest among the three specimens of L. yanzigouensis, and several features in the new specimen, such as the short preorbital length and the round rostroventral orbital rim, can be ontogenetically-related. The superb exposure of the palatal complex may be caused by the removing of its brain by a small predator in the contemporary Jehol Biota.  相似文献   

Stratigraphy of the Lower Cretaceous Sediments from the Carpathian Bend Area, Romania          下载免费PDF全文

Mihaela-Carmen MELINTE-DOBRINESCU  Dan C. JIPA 《《地质学报》英文版》2007,81(6):949-956

The Lower Cretaceous sediments of the Ceahl?u Nappe (from the bend region of the Romanian Carpathians) were investigated from lithological and micropaleontological (calcareous nannoplankton) points of view. Our investigations revealed that the studied deposits were sedimented within the latest Tithonian-Albian interval. The calcareous nannofossil assemblages of the turbidite calcareous successions (the Sinaia Formation) were assigned to the NJK-?NC5 calcareous nannofossil zones, which cover the Late Tithonian-Early Barremian interval. The sandy-shaly turbidites, which followed the calcareous turbidites of the Sinaia Formation, are Early Barremian-Early Albian in age (interval covered by the ?NC5-NC8 calcareous nannofossil zones). Because the studied deposited are mainly turbidites, many reworked nannofossils from older deposits are present in the calcareous nannofloras. Thus, some biozones (i.e., NC5), defined based on the last occurrences of nannofossils, could not be identified. The calcareous nannofossil assemblages are composed of Tethyan taxa (which dominate the nannofloras) and cosmopolitan taxa. During two intervals (the Late Valanginian and across the Barremian/Aptian boundary), Tethyan and cosmopolitan nannofossils, together with Boreal ones, were observed. This type of mixed calcareous nannoplankton assemblage is indicative for sea-level high-stand, which allows the nannofloral exchange between the Tethyan and Boreal realms, within the two-above mentioned intervals.  相似文献   

广丰盆地早白垩世火山-侵入杂岩稀土元素地球化学特征及成因探讨     

刘平华  吴仁贵  余达淦  周万蓬 《华东地质学院学报》2007,30(4):321-327

江西广丰早白垩世盆地火山-侵入杂岩稀土元素地球化学特征表明,本区火山-侵入杂岩可能是一套具有成因联系的岩石系列,杂岩中基性岩可分出稀土特征不同两类岩石,中酸性岩石亦可分出稀土特征不同两类的岩石,其中(橄榄)玄粗岩与钾长斑岩、橄辉粗玄岩与花岗斑岩稀土元素标准化曲线和稀土元素特征参数具有相似性。这些信息对揭示本区早白垩世基性岩浆的底侵作用具有重要的启迪意义。  相似文献   

Zircon age and Nd–Hf isotopic composition of the Yunnan Tethyan belt,southwestern China     

Fukun Chen  Xiang-Hui Li  Xiu-Li Wang  Qiu-Li Li  Wolfgang Siebel 《International Journal of Earth Sciences》2007,96(6):1179-1194

The Baoshan block of the Tethyan Yunnan, southwestern China, is considered as northern part of the Sibumasu microcontinent. Basement of this block that comprises presumably greenschist-facies Neoproterozoic metamorphic rocks is covered by Paleozoic to Mesozoic low-grade metamorphic sedimentary rocks. This study presents zircon ages and Nd–Hf isotopic composition of granites generated from crustal reworking to reveal geochemical feature of the underlying basement. Dating results obtained using the single zircon U–Pb isotopic dilution method show that granites exposed in the study area formed in early Paleozoic (about 470 Ma; Pingdajie granite) and in late Yanshanian (about 78–61 Ma, Late Cretaceous to Early Tertiary; Huataolin granite). The early Paleozoic granite contains Archean to Mesoproterozoic inherited zircons and the late Yanshanian granite contains late Proterozoic to early Paleozoic zircon cores. Both granites have similar geochemical and Nd–Hf isotopic charateristics, indicating similar magma sources. They have whole-rock T _DM(Nd) values of around 2,000 Ma and zircon T _DM(Hf) values clustering around 1,900–1,800 and 1,600–1,400 Ma. The Nd–Hf isotopic data imply Paleoproterozoic to Mesoproterozoic crustal material as the major components of the underlying basement, being consistent with a derivation from Archean and Paleoproterozoic terrains of India or NW Australia. Both granites formed in two different tectonic events similarly originated from intra-crustal reworking. Temporally, the late Yanshanian magmatism is probably related to the closure of the Neotethys ocean. The early Paleozoic magmatism traced in the Baoshan block indicates a comparable history of the basements during early Paleozoic between the SE Asia and the western Tethyan belt, such as the basement outcrops in the Alpine belt and probably in the European Variscides that are considered as continental blocks drifting from Gondwana prior to or simultaneously with those of the SE Asia.  相似文献   

Discovery of Radiolarian Fossils from the Aiketik Group at the Western End of the South Tianshan Mountains of Chinaand Its Implications   总被引：1，自引：0，他引：1  

LI Yuejun  WANG Zhaoming  WU Haoruo  HUANG Zhibin  TAN Zejinand LUO Juncheng Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing Tarim Oil Field Company  PetroChin  Korl  Xinjiang Zhu Xiling 《《地质学报》英文版》2002,76(2):146-154

The Aiketik Group, distributed at the western end of the South Tianshan Mountains, China, is an important lithostratigraphic unit involved in the South Tianshan orogen. It is separated from the adjacent rocks by faults. Generally, the geologists ascribed it to the Upper Carboniferous according to Pseudostaffella sp., Profusulinella sp. and Fusulinella sp. found from the limestone and sandy limestone of Aiketik. Our radiolarian fossils were obtained from the chert samples collected from the Haladaok section located at the upper Tuoshihan River. The fossils mainly include Albaillella undulata Deflandre, Albaillella paradoxa Deflandre, Albaillella sp. aff. A. paradoxa Deflandre, Albaillella sp. cf. A. deflandrei Gourmelon, Albaillella sp., Albaillella excelsa Ishiga, Kito and Imoto (?), Belowea variabilis (Ormiston et Lane), Callella cf. C. parvispinosa Won, Entactinia cf. E. tortispina Ormiston et Lane, Entactinia aff. E. tortispina Ormiston et Lane, Entactinia variospina Won, Entactinia sp., Eostylodicty  相似文献   

东南大陆边缘早侏罗世火成岩特征及其构造意义   总被引：36，自引：4，他引：36  

邢光福  舒良树等 《地质通报》2002,21(7):384-391

东南大陆边缘早侏罗世火成岩主要呈双峰式火山岩、基性超基性杂岩体及A型花岗岩等形态产出。本文运用岩石学探针技术,通过早侏罗世火成岩岩石学与地球化学研究,并与晚中生代火成岩作对比,提出早侏罗世火成岩的形成与南岭东段近EW向张性断裂活动有关,标志着印支挤压造山的结束;之后东南大陆进入晚中生代NE向活动大陆边缘俯冲造山阶段,经历了挤压造山—剪切拉张过程,并在晚白垩世末期进入又一轮后造山拉张裂解阶段,即中生代时东南大陆边缘经历了早中生代(三叠纪—早侏罗世)和晚中生代(中侏罗世—晚白垩世)两期造山事件,其中早侏罗世的区域拉张作用是特提斯构造域向滨太平洋构造域转换的前奏,构造域转换可能始于中侏罗世(165Ma)。  相似文献   

Studies on⁴⁰Ar/³⁹Ar thermochronology of strike-slip time of the Tan-Lu fault zone and their tectonic implications   总被引：6，自引：0，他引：6  

ZHU Guang  SONG Chuanzhong  WANG Daoxuan  Liu Guosheng  XU Jiawei 《中国科学D辑(英文版)》2001,44(11):1002-1009

Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for⁴⁰Ar/³⁹Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded⁴⁰Ar/³⁹Ar plateau ages of 128 —132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu uplift gave the same⁴⁰Ar/³⁹Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists. Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during formation of the Dabie orogenic belt.  相似文献   

宜溧地区花岗岩类岩石谱系单位的划分     

张祥云 《江苏地质》2001,25(3):150-157

宜溧地区中生代侵入体经地面调查和对比分析,依据花岗岩类岩石谱系单位划分原则,可划分为2个超单元(序列)、7个单元以及1个独立侵入体和2类脉岩.戴埠序列岩石化学特征为钙碱质,平桥序列为弱碱质,反映两个序列岩浆有着明显的差异,组合变异图进一步表明两序列的岩浆演化机理不同,是不连续和彼此独立存在.戴埠序列为轻稀土富集型,平桥序列属于重稀土富集型,应归属A型花岗岩系列.  相似文献   

张广才岭燕山早期白石山岩体成因与壳幔相互作用   总被引：34，自引：19，他引：34  

孙德有  吴福元  林强  路孝平 《岩石学报》2001,17(2):227-235

出露于东北地区张广才岭的白石山岩体,其全岩-矿物Rb-Sr等时线年龄为196士4 Ma,表明形成于中生代的燕山早期,而非传统认识上的印支期.岩体主岩和闪长质包体均具有低ISr(≈0.705)和正εNd(t)(+1.7～+2.2)值的特点,反映岩体成因与地幔具有密切的联系.地质学、岩石学和地球化学的详细研究表明该岩体具有壳幔混合成因,闪长质包体是较基性的地幔岩浆进入主岩浆中淬火结晶而成,花岗质岩浆的源区主要为新生的地壳物质.动力学分析表明,本区在华北板块和西伯利亚板块碰撞拼合后,由于东侧大洋板块的俯冲及后续的岩石圈拆沉效应,导致软流圈地幔上隆及幔源岩浆的板底垫托,并进而造成先存和新生地壳的部分熔融和不同源区岩浆的混合作用.底垫的新生地壳是兴蒙造山带造山后晚期形成的.因此,古生代-中生代是本区地壳生长的重要时期,且这种地壳生长是在垂向构造机制下进行的.  相似文献