检索结果-南通市图书馆

New Insights into the Late Triassic Nadigangri Formation of Northern Qiangtang, Tibet, China： Constraints from u-pb ages and Hf Isotopes of Detrital and Magmatic Zircons

引用

Acta Geologica Sinica(English Edition) 2018年第4期92卷 1451-1467页

作者： LI Xueren WANG Jian CHENG Leli Fu Xiugen WANG Yuke Chinese Academy of Geological Sciences Beijing 100037 China China university of Geosciences (Beijing) Beijing 100083 China Key Laboratory for Sedimentary Basin and Oil and Gas Resources Ministry of Land and Resources Chengdu Sichuan 610081 China Chengdu Center of China Geological Survey Chengdu Sichuan 610081 China Institute of Mud Logging Technology and Engineering Yangtze University Jingzhou Hubei 434023 China

We report here u-pb age and in situ Hf isotopic results for detrital and magmatic zircons from one conglomerate and four tuffite samples from the Late Triassic Nadigangri Formation across the North Qiangtang depression, Tibet. Coupled with previously published data in the region, this paper proposes new insights into the geochronological framework for the Nadigangri Formation. The deposition ages of tuffite from top to bottom in the Woruo Mountain, Quem Co and Dongqu River, are 203 Ma, 226 Ma, 221.5 Ma and 221.1 Ma, respectively. The detrital zircons yield a younger cluster of ages of 201.5-225 Ma from the conglomerate of the Quem Co Formation. The Late Triassic Nadigangri Formation defines a temporal range approximately between 201 and 225 Ma （Norian-Rhaetian）, including three predominant groups of 220-225 Ma, 210-217 Ma and 201-205 Ma, which correspond with the three main rifting episodes of initial rifting, further rifting and final rifting. Positive ~Hf（t） value and low model ages in younger detrital zircons suggests a juvenile character. However, the Hf isotopes of magmatic zircons display the presence of reworked ancient crust with 1.1-1.8 Ga. These results provide strong constraints not only on the temporal range of the Late Triassic Nadigangri Formation, but also on the onset of the Qiangtang Mesozoic rift basin.

关键词： u-pb ages Hf isotope Nadigangri Formation Late Triassic Qiangtang

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Exoscopy of Detrital Zircons from Niamey Neoproterozoic Sandstones (Eastern Edge of the West African Craton, Southwestern Niger): Interpretation of Detrital Sediments Provenance

引用

Open Journal of Geology 2024年第5期14卷 617-628页

作者： Hassan Ibrahim Maharou Karimou Laouali Idi Diafarou Alzouma Amadou Salissou Abdoul Ganiou Amadou Gnissa Sidibé Moussa Konaté Department of Geology Faculty of Science and Techniques Abdou Moumouni University Niamey Niger Department of Life and Earth Sciences Ecole Normale Sup&#233rieure (ENS) Abdou Moumouni University Niamey Niger

This study focuses on exoscopic analyses of detrital zircon grains of Archean and Paleoproterozoic age, contained in the sediments from the Niamey Neoproterozoic sandstones (Niamey region), with a view to confirming the sediments sources already proposed (Kénéma-Man domain for Archean-age zircons and Baoulé Mossi domain for Paleoproterozoic-age zircons). Exoscopic analysis reveals that Archean zircon grains are more corroded, with rounded to sub-rounded shapes, while Paleoproterozoic zircon grains are less corroded and mostly angular in shape. The strong corrosion of Archean zircon grains, implying long-distance transport, is consistent with the remoteness of the Kenema-Man domain which are the source these sediments. The fact that the Paleoproterozoic zircon grains show little or no wear implies a proximal source of sediments, corresponding to the Baoulé Mossi domain.

关键词： Exoscopic Analysis Detrial Zircon Grains u-pb ages Niamey Neoproterozoic Sandstones Niamey Region

来源：

维普期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

In situ determination of u-pb ages and Sr-Nd-Hf isotopic constraints on the petrogenesis of the Phalaborwa carbonatite Complex,South Africa

In situ determination of U-Pb ages and Sr-Nd-Hf isotopic con...

引用

中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Roger H.Mitchell J.Barry Dawson Gnther Brandl Masaki Yuhara Department of Geology Lakehead UniversityOntarioCanada P7B 5EI Council for Geoscience Limpopo UnitP.O.Box 620Polokwane 0700South Africa Department of Earth System Science Faculty of ScienceFukuoka UniversityJonanFukuoka 814-0180Japan

The Phalaborwa carbonatite Complex,situated in the northeastern part of South Africa,is characterized by copper and zirconium mineralization,and is composed principally of pyroxenites,phoscorite and carbonatite (banded and transgressive).The complex is transected by mafic dykes,and is geographically associated with a satellite syenite and minor granite intrusions.Zircon and baddeleyite u-pb isotopic age determinations using CAMECA 1280 secondary ion mass spectrometry have shown that the outer pegmatitic pyroxenite at the Loolekop pipe was emplaced at 2060±4 Ma,and the main phoscorite at 2062±2 Ma.Both ages are identical to those of 2060±2 and 2060±1 Ma for the banded and transgressive carbonatites,respectively.The satellite syenite,which forms plug-like bodies outside of the border of the main complex,and the later mafic dyke have "similar" emplacement ages of 2068±17 and 2062±53 Ma,indicating that these intrusions were apparently near-synchronously emplaced.In contrast to other carbonatites,the Phalaborwa Complex is characterized by high initial Sr and low initial Nd and Hf isotopic compositions.to situ isotopic analyses of apatite, calcite,zircon and baddeleyite indicate that the primary magma was derived from an enriched mantle. As the complex was emplaced slightly earlier at～2060 Ma than the nearby mafic phase of the Bushveld Complex (-2055 Ma),it is proposed that the Phalaborwa carbonatite magmatism was triggered by the same mantle plume activity,which partially melted the overlying lithospheric mantle.This contribution also highlights that isotopic studies used to constrain the genesis of ancient igneous complexes should concentrate on minerals with low parent/daughter elemental ratios,such as apatite and calcite for Sr isotopes,and zircon and baddeleyite for Hf isotopes.

关键词： u-pb ages Zircon and baddeleyite Sr-Nd-Hf isotopes Carbonatite Phalaborwa

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

WANCE:A possibly Volcanism-Induced Ediacaran Carbon Isotope Excursion

引用

Journal of Earth Science 2022年第3期33卷 778-788页

作者： Zhongwu Lan State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China

Four carbonate carbon isotope(δ^(13)C_(carb))excursions are recognized in the Ediacaran Doushantuo Formation in South China,the genesis of which remains disputed.Whereas three of these δ^(13)C_(carb) excursions possibly record secular biogeochemical variations,the other one,namely Weng'an negative carbonate carbon isotope excursion(WANCE)with an age of ca.620 Ma occurs mainly within the northern Yangtze Platform.In this study,a SIMS u-pb age of ca.620 Ma was documented from continental rift volcanism within the adjacent South Qinling terrane.Its temporal overlap with WANCE suggests a possible causal link.Volcanism-induced seafloor uplift may have prompted DOC oxidation in surficial oxygenated oceans,inducing the occurrence of WANCE.

关键词： Early Ediacaran δ^(13)C_(carb)excursion magmatism zircon u-pb ages

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Tonalites and plagiogranites of the Char suture-shear zone in East Kazakhstan:Implications for the Kazakhstan-Siberia collision

引用

Geoscience Frontiers 2016年第1期7卷 141-150页

作者： M.L.Kuibida I.Yu.Safonova P.V.Yermolov A.G.Vladimirov N.N.Kruk S.Yamamoto lnstitute of Geology and Mineralogy SB RAS Koptyuga ave.3Novosibirsk630090Russia Novosibirsk State university Pirogova St.2Novosibirsk630090Russia IPCON Joint Venture Academy of Sciences of Kazakhstanlppodromnaya 5100019KaragandaKazakhstan Tomsk State university Lenina St.36Tomsk634050Russia university of Tokyo MeguroTokyo153-8902Japan

The paper presents first ue pb zircon ages and geochemical data from Carboniferous granitoids（tonalites and plagiogranites） of the Char sutureeshear zone in East Kazakhstan, which is located in the northwestern Central Asian Orogenic Belt（CAOB）. The study included analysis of geological setting, major and trace elements, and rock petrogenesis. The Char tonalites and plagiogranites occur as NW-striking linear chains inside Visean serpentinite mélange. Petrographycally, the tonalites show signs of syntectonic deformation, and the plagiogranites are less deformed suggesting their later intrusion. The tonalites yielded a LA-ICP-MS zircon age of ca. 323 Ma, i.e. exactly at the boundary between the early and late Carboniferous. Compositionally, the tonalites and plagiogranites are characterized, respectively, by high SiO2（67-70 and 73-74 wt.%） and Al2O3（17-19 and 14-15 wt.%）, Sr/Y 〉 40 and low Yb=0.2-0.5 ppm.Their multi-element patterns show clear Nb-Ta negative anomalies. The low Nb/Ta ratios（7-15） and Zr（114-191 ppm） suggest a MORB-type protolith（amphibolite） with subchondritic Nb/Ta（8-17） and low Zr（1-72 ppm）. The low contents of K and Rb suggest weak assimilation of the melts by island arc felsic crust. The subchondritic Nb/Ta ratios exclude their derivation by the melting of subducted/dehydrated MORB. We argue that the Char high-Al tonalites and plagiogranites formed by the melting of hydrated MORB at the base of the mafic lower crust at pressures of 10-15 kbar. The occurrences of the Char tonalites and plagiogranites inside the Visean serpentinite mélange overlapped by Serpukhovian conglomerates, their alignment parallel to deformation zones, and their geochemical features suggest their origin by the melting of mafic lower crust in relation to the collision of the Siberian and Kazakhstan continents.

关键词： Earlyelate Carboniferous boundary NW Central Asian Orogenic Belt u-pb ages Whole-rock geochemistry Petrogenesis Mafic crust melting

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

In situ u-pb age determination and Nd isotopic analysis of perovskites from kimberlites in southern Africa and Somerset Island,Canada

In situ U-Pb age determination and Nd isotopic analysis of p...

引用

中国科学院地质与地球物理研究所第十届(2010年度)学...

作者： Roger H.Mitchell Department of Geology Lakehead UniversityThunder BayOntarioCanada P7B 5E1

Determination of the emplacement ages and initial isotopic composition of ldmberlite by conventional isotopic methods using bulk rock samples is unreliable as these rocks usually contain diverse clasts of crustal-and mantle-derived materials and can be subject to post-intrusion sub-aerial alteration.In this study,8 samples from 5 kimberlites in southern Africa and twelve samples from 7 kimberlites from Somerset Island,Canada have been selected for in situ perovskite u-pb isotopic age determination and Nd isotopic analysis by laser ablation using thin sections and mineral separates.These fresh perovsldtes occur as primary groundmass minerals with grain-sizes of 10-100μm.They were formed during the early stage of magmatic crystallization,and record data for the least contaminated or contamination-free ldmberlitic magma.u-pb isotopic data indicate that the majority of the southern Africa kimberlites investigated were emplaced during the Cretaceous with ages of 88±3 to 97±6 Ma, although one sample yielded an Early Paleozoic age of 515±6 Ma.Twelve samples from Somerset Island yielded ages ranging from 93±4 Ma to 108±5 Ma and are contemporaneous with other Cretaceous ldmberlite magmatism in central Canada(103-94 Ma).Although whole-rock compositions of the kimberlites from southern Africa have a large range ofε(t)values(-0.5 to +5.1),the analysed perovsldtes show a more limited range of +1.2 to +3.1. Perovsldtes from Somerset Island haveε(t)values of-0.2 to +1.4.These values are lower than that of depleted asthenospheric mantle,suggesting that kimberlites might be derived from the lower mantle.This study shows that in situ u-pb and Nd isotopic analysis of perovskite by laser ablation is both rapid and economic,and serves as a powerful tool for the determination of the emplacement age and potential source of ldmberlite magmas.

关键词： Laser ablation u-pb ages Nd isotopes Perovskite Kimberlite Southern Africa Canada

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

In situ u-pb,Sr,Nd and Hf isotopic analysis of eudialyte by LA-(MC)-ICP-MS

In situ U-Pb,Sr,Nd and Hf isotopic analysis of eudialyte by ...

引用

中国科学院地质与地球物理研究所第十届(2010年度)学...

作者： Michael A.W.Marks Roger H.Mitchell Gregor Markl Institut fur Geowissenschaften Eberhard-Karls-Universitat TubingenWilhelmstrasse 56D-72074 TubingenGermany Department of Geology Lakehead UniversityThunder BayOntarioCanada P7B 5E1

Eudialytes are a group of complex Na-Ca zirconosilicate minerals that generally occur in peralkaline agpaitic syenites.Given that eudialytes are easily altered and commonly contain inclusions of earlier-crystallized minerals,in situ laser ablation is considered as the most suitable method to determine their u-pb ages,and Sr,Nd and Hf isotopic compositions.Electron microprobe and LA-ICP-MS analysis of eudialytes from nepheline syenites from Ilimaussaq(Greenland),Khibiny and Lovozero(Russia),Saima(China),Tamazeght (Morocco),Kipawa and Mont Saint Hilaire(Canada),Pocos de Caldas(Brazil)and Langesund Fjord (Norway),indicate that this mineral typically has high contents of u,pb,Nb,Ta,Zr,Hf and rare earth elements(REE). Analysis of an in-house standard eudialyte by both solution and laser ablation methods demonstrates that precise and accurate u-pb ages can be obtained from eudialyte after correction for the common pb content. The high Sr,Nd and Hf contents in eudialyte,coupled with the generally low Rb/Sr and Lu/Hf ratios,also permit the precise determination of in situ Sr,Nd and Hf isotopic ratios by LA-(MC)-ICP-MS methods. However,some eudialytes with Rb/Sr ratio of>0.02 and Yb/Sr>0.1,and Lu/Hf>0.08(or Yb/Hf>0.4-0.5) cannot be used for in situ Sr and Hf isotopic measurement.Eudialyte is the only mineral investigated to date for which it is possible to determine simultaneously u-pb ages and Sr,Nd and Hf isotopic compositions.

关键词： u-pb ages Sr,Nd and Hf isotopic ratios Eudialyte Laser ablation Agpaitic syenites

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：