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Search Results: 1 - 10 of 11132 matches for " zircon U-Pb age "
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Basement Lithology Characteristics and Forming Age of Bongor Basin Chad

张明瑜, 宋柏荣, 田志彬, 张乃丹, 施玉华, 王奇
Open Journal of Nature Science (OJNS) , 2016, DOI: 10.12677/OJNS.2016.41009
乍得Bongor盆地基底为早寒武世之前形成的一套结晶基岩,该套岩石富含油气,因此,对盆地基底岩石类型及形成时代的研究越显重要。本文主要以岩心观察、描述为基础,采用岩石薄片鉴定、单颗粒锆石U-Pb同位素测定等方法,对乍得Bongor盆地基底岩性进行鉴定和划分,并对其形成和演化时代进行分析。结果认为:岩性为由变质岩和岩浆岩组成的杂岩体,岩性包括2大类14个亚类;单锆石测年年龄集中在550~600 Ma,变质岩原岩年龄主要集中在616 ± 6~526.5 ± 2.7 Ma,最老的原岩年龄1006 ± 12~946 ± 5 Ma,变质年龄在553 ± 19~464 ± 5 Ma,岩浆岩的年龄主要集中在621 ± 16~525.3 ± 2.5 Ma。由于岩石类型、性质及形成时代的差异,造成后期地质作用改造和储层的发育程度不同。
The basement of the Bongor basin Chad is formed by a set of crystalline basement rocks before the Early Cambrian, which is rich in oil and gas. Therefore, it is more important to study the type of basement rocks and the formation age of the basin. This paper is mainly based on the core observation and description, by identification of rock slice, single grain zircon U-Pb isotope determination, Chad Bongor basin’s basement lithology of identification and delineation, and the formation and evolution of era were analyzed. The results show that the lithology is composed of metamorphic rocks and magmatic rocks, which are composed of 14 kinds of 2 sub categories; Single Zircon dating was concentrated in the age of 550 - 600 Ma, the age of metamorphic rocks was mainly con- centrated in 616 ± 6 - 526.5 ± 2.7 Ma, the oldest old rock age was 1006 ± 12 - 946 ± 5 Ma, metamorphic age was 553 ± 19 - 464 ± 5 Ma, the age of magmatic rock was mainly concentrated in 621 ± 16 - 525.3 ± 2.5 Ma. Because of the difference of the rock type, nature and the age of formation, the transformation of the geological function and the development of the reservoir are different in the later stage.
Geochronological, Sedimentary, Structural, and Metallogenic Characteristics of Southeast China during the Mesozoic: A General Review  [PDF]
Pengju Li, Hongying Li
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.69082
Abstract: The tectonic evolution of Southeast China during Late Mesozoic is a prominent topic. Numerous tectonic models on Late Mesozoic evolution ofSoutheast Chinahave beenpublished in the past 50 years. We synthesized many up-to-date and precise zircon U-Pb ages, sedimentary strata, and regional structures and discussed the oxygen fugacity of magmas and related ore deposits. We also analyzed the most current tectonic models published by some scholars. A multistage tectonic stress evolution history during Late Mesozoic was constructed, which included the following stages: 1) Early-Middle Jurassic (196 - 175 Ma) extension, in which many bimodal volcanics formed; 2) Middle-Late Jurassic (165 - 140 Ma) compression, which generated largescale gneissic granites, garnet-bearing granites, stratigraphic hiatus, and nappe structures; 3) Early Cretaceous (140 ± 5 - 120 Ma) extension, which formed weakly deformed or undeformed granites, alkali granites, metamorphic core complexes, graben basins, and basic dike swarms; 4) Early Cretaceous (120 - 110 Ma) compression, which generated nappe structures, volcanic hiatuses, and garnet-bearing granites; and 5) Early-Late Cretaceous (110 - 80 Ma) extension, which generated largescale bimodal volcanics, basic dike swarms, alkali granites, and graben basins. The Late Mesozoic tectonic evolution ofSoutheast Chinamay be attributed to the drifting history of the Paleo-Pacific plate. The drifting direction of the Paleo-Pacific plate has changed several times since 140 Ma, which led to major changes in the tectonicphenomena from Jurassic to Cretaceous and to the formation of Late Mesozoic mineral deposits.
SHRIMP U-Pb Zircon Age and Its Implications of Quartz Syenite in Hadamengou, Inner Mongolia

任康绪, 阎国翰, 蔡剑辉, 邹天仁, 牟保磊, 李凤棠
Advances in Geosciences (AG) , 2013, DOI: 10.12677/AG.2013.31007
采用同位素稀释法(TIMS)和二次离子探针法(SHRIMP)对内蒙古哈达门沟大型金矿床主矿体控矿岩石进行了锆石测年研究,最终确定了石英正长岩形成于古元古代早期,其锆石SHRIMP U-Pb谐和年龄为(2483 ± 10) Ma(1σ),上交点年龄为(2508 ± 41) Ma(1σ)。哈达门沟石英正长岩是国内迄今报道的元古代最古老的富碱侵入岩,其时空分布具有重要大地构造意义,指示了华北古陆在经历太古代末的碰撞拼合事件已经结束,地壳具有一定厚度,并已经开始向拉张性构造环境转变。
Based on dating zircon TIMS and SHRIMP U-Pb ages for the ore-controlling quartz syenite of Hadamengou large gold deposit, Inner Mongolia, the authors confirmed that the quartz syenite intruded upon during the early of Pa-leoproterozoic. Its zircon SHRIMP U-Pb concordant point age was (2483 ± 10) Ma(1σ) and the upper intersection age gived (2508 ± 41) Ma(1σ) on the disaccording line respectively. The quartz syenite in Hadamengou was proved the oldest Paleoproterozoic alkali-rich intrusive rock inChinatill now. Its old age and its distribution of the alkali-rich intrusive rock had important tectonic significance. It revealed that after the amalgamation at the end period of Archean, the crust of North China Craton had reached some thickness and had transformed into a kind of extensional tectonic settings since the intrusion of the alkali-rich intrusive rock in Hadamengou.
Zircon U-Pb dating of basement gneisses in the super-large Bayan Obo REE-Fe-Nb deposit, Inner Mongolia
Kaiyi Wang,Hongrui Fan,Yihan Xie,Huimin Li
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9058
Abstract: Zircon U-Pb ages have been determined for basement gneisses in the Bayan Obo REE-Fe-Nb deposit. On the U-Pb concordia diagram data of three samples yield upper intercept ages of 1948–1917 Ma. Thus, these basement gneisses are of Paleoproterozoic. Rock association of these basement gneisses includes tonalite, syenite and paragneiss, not belonging to a sedimentary package. It is more appropriate to consider this association as a basement complex rather than a stratigraphic “Group”.
Geochronological evidence for existence of South Mongolian microcontinent—A zircon U-Pb age of grantoid gneisses from the Yagan-Onch Hayrhan metamorphic core complex
Tao Wang,Yadong Zheng,G. E. Gehrels,Zhiguo Mu
Chinese Science Bulletin , 2001, DOI: 10.1007/BF02901917
Abstract: A zircon U-Pb age of (916±16) Ma is measured for grantoid gneisses from the Yagan-Onch Hayrhan metamorphic core complex and represents the crystallization age of the grantoid magma. This age provides evidence for the existence of the South Mongolian microcontinent, which is consistent with the analysis of the regional geology.
Zircon U-Pb ages of olivine pyroxenite xenolith from Hannuoba: Links between the 97–158 Ma basaltic underplating and granulite-facies metamorphism
Yongsheng Liu,Honglin Yuan,Shan Gao,Zhaochu Hu,Xuance Wang,Xiaoming Liu,Wenli Lin
Chinese Science Bulletin , 2004, DOI: 10.1007/BF03184037
Abstract: U-Pb zircon dating by LA-ICP-MS and SHRIMP for one olivine pyroxenite yields complex age populations including Mesozoic ages of 97–158 Ma and 228 ± 8.7 Ma, Early Paleozoic ages of 418–427 Ma, Paleoproterozoic age of 1844±13 Ma, Neoarchean age of 2541 ± 54 Ma and middle Archean age of 3123 ± 4.4 Ma. The 97–158 Ma and 228 ± 8.7 Ma zircons show typical igneous oscillatory zonation in CL images, suggesting two episodes of magmatic events. Overlapping of the 97–158 Ma ages with that of granulite xenoliths indicates that the Mesozoic granulite-facies metamorphism was induced by heating from the basaltic underplating at the base of the lower crust. Both processes lasted at least from about 158 to 97 Ma. Ages of 418 –427 Ma could be records of the subduction of Mongolia oceanic crust under the North China craton. Ages of 1.84 Ga, 2.54 Ga and 3.12 Ga correspond to the three important crust-mantle evolutionary events in the North China craton, and imply preservation of Precambrian lower crust in the present-day lower crust.
SHRIMP U-Pb zircon age of the youngest exposed pluton in eastern China
Wu Fuyuan,S. A. Wilde,Sun Deyou
Chinese Science Bulletin , 2001, DOI: 10.1007/BF02900661
Abstract: Analysis using the Sensitive High Resolution Ion Microprobe (SHRIMP) shows that the Yongsheng pluton, located to the south of Huadian County, Jilin Province, in the North China Craton, has a zircon U-Pb isotopic emplacement age of (31.6±1.3) Ma. It is therefore the youngest exposed pluton so far recognized in eastern China. Although geochemical data indicate intensive crystal fractionation, the Sr-Nd isotopic features suggest that the magmatic source region of the lithospheric mantle was weakly depleted. This implies that the previous enriched lithospheric mantle had been replaced by juvenile asthenospheric mantle before or during the Palaeogene. This recognition has great significance for future work on the Mesozoic-Cenozoic geological evolution and deep geological processes in eastern China.
Zircon U-Pb ages of the basement rocks beneath the Songliao Basin, NE China
Fuyuan Wu,Deyou Sun,Huimin Li,Xiaolin Wang
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02898900
Abstract: The basement of the Songliao Basin is mainly composed of slightly-metamorphosed or unmetamorphosed Paleozoic strata, granites and gneiss. Petrographical studies indicate that the gneiss was originally the granitic intrusions which were deformed in the later stage. One undeformed granitic rock sample gives a U-Pb age of (305±2) Ma, and the mylonitic granite yields a U-Pb age of (165±3) Ma. Both of the two samples contain no inherited zircon, which suggests that there is no large-scale Precambrian crystalline basement beneath the Songliao Basin.
Zircon U-Pb dating of basement gneisses in the super-large Bayan Obo REE-Fe-Nb deposit, Inner Mongolia

WANG Kaiyi,

科学通报(英文版) , 2002,
Abstract: Zircon U-Pb ages have been determined for basement gneisses in the Bayan Obo REE-Fe-Nb deposit. On the U-Pb concordia diagram data of three samples yield upper intercept ages of 1948-1917 Ma. Thus, these basement gneisses are of Paleoproterozoic. Rock association of these basement gneisses includes tonalite, syenite and paragneiss, not belonging to a sedimentary package. It is more appropriate to consider this association as a basement complex rather than a stratigraphic "Group".
Crustal evolution of the Shiwandashan area in South China: Zircon U-Pb-Hf isotopic records from granulite enclaves in Indo-Sinian granites
Liang Zhao,Feng Guo,WeiMing Fan,ChaoWen Li,XiaoFeng Qin,HongXia Li
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-3225-1
Abstract: U-Pb dating coupled with Hf isotope analyses on zircon from metasedimentary granulite enclaves in the Jiuzhou peraluminous granite from the Shiwandashan area in southeastern Guangxi Province, South China are presented in this paper. The results show that the protoliths of these granulite enclaves were mainly composed of Neo-Mesoproterozoic (564–1061 Ma) clastic materials with a peak age at ~822 Ma. These materials were probably derived from the igneous rocks that were emplaced during the Neoproterozoic breakup of Rodinian Supercontinent. Subordinate sediments include the Paleoproterozoic (1778–2227 Ma) and even the Meso-Paleoarchean materials with the oldest U-Pb age at 3551±8 Ma, indicating the existence of ancient crustal rocks in the area and/or its surrounding regions. Younger grains include the early Mesozoic (234±2 Ma) magmatic zircon populations and the late Permian (253±3 Ma) metamorphic zircon populations. Further zircon Hf isotope analyses reveal that their protoliths were complex, containing both recycled crustal rocks and juvenile materials. Combined zircon U-Pb ages and Hf isotope compositions indicate that at ~253 Ma, the Shiwandashan area experienced an intensive thermal event that resulted in the granulite-facies metamorphism; and that crustal remelting occurred at ~234 Ma to form the S-type granitoids during the uplifting stage. The metasedimentary granulite enclaves are resitites of these granitoids.
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