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71.
Hf isotopic compositions of the standard zircons for U-Pb dating 总被引:48,自引:4,他引:48
XU Ping WU Fuyuan XIE Liewen & YANG Yueheng Institute of Geology Geophysics Chinese Academy of Sciences Beijing China Correspondence should be addressed to Wu Fuyuan 《科学通报(英文版)》2004,49(15):1642-1648
Zircon, a common accessory mineral in various kindsof rocks, is an important subject for U-Pb isotopic dating.With requirements for high spatial resolution with highprecision and accuracy, SHRIMP (Sensitive High Resolu-tion Ion Micro Probe) and LA-ICPMS (Laser AblationInductively Coupled Plasma Mass Spectrometry) nowserve as the important tools in zircon U-Pb dating. Sinceboth methods need standard zircon for external age cali-bration, an ideal standard zircon is critical for obtai… 相似文献
72.
卓勒萨依一带的乌郎组火山岩位于温泉县城东南25km处,岩石类型主要为安山岩和流纹岩,火山岩浆具有由酸性—中性—酸性演化的特点,以裂隙式喷发类型为主。LA-ICP-MS锆石U-Pb年龄为(293±3)Ma(MSWD=0.34、Probability=0.997),时代为早二叠世早期。该火山岩里特曼指数(σ)为1.71~2.60;碱度率(AR)为2.13~2.85,K2O/Na2O比值为0.31~1.83,属钙碱性系列。Nb/Ta值为18.65~22.85,略高于原始地幔值,Zr/Hf值为28.54~41.08,与原始地幔值相近。RbN/YbN比值为9.82~20.04,大于1,属于强不相容元素富集分配形式。稀土总量∑REE为 (118.41~194.70)×10-6;(Ce/Yb)N值为2.55~3.70,(La/Yb)N值为2.98~4.17,均大于1,属于轻稀土富集型,且轻稀土分馏明显;δEu值为0.19~0.59,远小于1,显示为负铕异常,铕亏损明显。根据相关构造环境判别图解,结合火山岩的地球化学特征及其所处的区域地质背景,认为在早二叠世发生大规模的陆陆叠覆造山作用,卓勒萨依一带火山活动较强烈,所反映的构造环境为陆内岛弧造山带火山岩环境。 相似文献
73.
U-Pb dating of zircon grains from the ore-bearing plagioclase amphibolite in the Dashuigou Te deposit 总被引:2,自引:0,他引:2
Shijin Xu Weizhou Shen Rucheng Wang Jianjun Lu Xiaoming Chen Yuping Lin 《科学通报(英文版)》1998,43(17):1486-1486
The Dashuigou Te deposit is a unique independent one found in the world, and hosted in the plagioclase arnphibolite. The upper
intercept age of single zircon from the arnphibolite can be considered to be the crystallization age of the source-rock of
the amphibolite (tholeiitic basalt), while the lower intercept is nearly consistent with the time of the tectono-thermal event. 相似文献
74.
Geochronology and geochemistry of the Fangcheng Neoproterozoic alkali-syenites in East Qinling orogen and its geodynamic implications 总被引:5,自引:0,他引:5
ZhiWei Bao Qiang Wang GuoDian Bai ZhenHua Zhao YaoWu Song XiaoMing Liu 《科学通报(英文版)》2008,53(13):2050-2061
Finding of Neoproterozoic syenites at Fangcheng in the northern Qinling region of the East Qinling orogen provides an important constraint on timing of tectonic transformation to extensional regime. The alkaline pluton consists mainly of nepheline syenite, aegirine syenite, and alkali-feldspar syenite. The syenites are of intermediate (SiO2 = 54%-62%), rich in alkali (K2O+Na2O = 12%-15%), aluminum (Al2O3= 16.81%-23.26%) and large ion lithophile elements (LILE), without any obvious Nb, Ta, Zr, and Hf anomalies. The Fangcheng syenites are geochemically characterized by relative enrichment of LREE, minor differentiation of HREE, significant negative Eu anomalies (Eu = 0.13-0.23), less negative εNd(t) values of -1.37 to-3.90, young Nd model ages of 1364 to 1569 Ma, and high zircon saturation temperatures of 915 to 1044℃. The syenitic magmas probably originated from small proportion melting of upper mantle in an extensional regime of intraplate-anorogenic tectonic setting, and have been slightly contaminated by crustal materials during ascending and/or emplacement. LA-ICP-MS zircon U-Pb dating yields ages of 844.3±1.6 Ma (MSWD=0.86), suggesting that the Fangcheng alkaline syenites formed in the early Neoproterozoic. They are the oldest Neoproterozoic alkaline rocks ever recognized in the Qinling orogen as well as in South China. This implies that the tectonic regime of the Qinling region would have transformed from post-collisional stretch to intraplate-anorogenic extension no later than 844 Ma. 相似文献
75.
Identification of 3.5 Ga detrital zircons from Yangtze craton in south China and the implication for Archean crust evolution 总被引:5,自引:0,他引:5
The LA-ICP-MS U-Pb dating of hundreds of detrital zircon grains from the Sinian sandstones of Liantuo formation and tillites of Nantuo formation at Sanxia area in Yichang identified 3319?3508 Ma zircon grains. Their 207Pb/206Pb and 206Pb/238U ages show excellent agreement (concordia degree 99%?100%). Their CL images exhibit well-developed oscillatory zoning and the Th/U ratios are within 0.46?0.76, implying that they are igneous zircons which formed during middle-early Archean. These zircons are the oldest ones discovered in Yangtze craton until now. However, the detrital zircons with ages older than 3.3 Ga in the metamorphic rocks of Kongling group were not found by further investigation, which suggests the presence of crust older than high-grade metamorphic Kongling terrain in Yangtze craton. 相似文献
76.
First SHRIMP zircon U-Pb ages for Hutuo Group in Wutaishan: Further evidence for Palaeoproterozoic amalgamation of North China Craton 总被引:10,自引:0,他引:10
S. A. Wilde ZHAO Guochun WANG Kaiyi & SUN MinDepartment of Applied Geology Curtin University of Technology PO Box U Perth Australia Department of Earth Science University of Hong Kong Pokfulam Road Hong Kong China Institute of Geology Geophysics Chinese Academy of Sciences Beijing ChinaCorrespondence should be addressed to S. A. Wilde 《科学通报(英文版)》2004,49(1):83-90
A felsic tuffaceous rock, obtained from a metamorphosed sequence of volcanics and sediments of the Hutuo Group, 8 km south of Taihuai in Wutaishan, contains two zircon populations. These record SHRIMP 207Pb/206Pb weighted mean ages of 2180±5 Ma and 2087±9 Ma, respectively. The older date is within error of the age of the Dawaliang Granite in Wutaishan and is considered to be 相似文献
77.
Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Formation in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma, which is consistent with the age of the Early Mesozoic underplating granulites, and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma, which is highly consistent with the Ar-Ar dating of the host volcanic rocks. Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites, indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic. 相似文献
78.
Zircon SHRIMP U-Pb geochronology and petrogenesis of the plagiogranites from the Lagkor Lake ophiolite, Gerze, Tibet, China 总被引:6,自引:0,他引:6
Field relationship, along with petrographical, petrological, and geochemical characteristics, and zircon populations, indicates that the plagiogranites from the Lagkor Lake ophiolite in the Bangong-Nujiang suture zone (~ 20 km south of Gerze County, central Tibet, China), derived from anatexis of hydrated gabbros by ductile shearing during transport of the oceanic crust. Therefore, this kind of plagiogranite is coeval to or little later than the spreading of the oceanic crust. Zircon SHRIMP age of 166 ± 2.5 Ma for the plagiogranites indicates that an oceanic basin existed in the western part of the Bangong-Nujiang zone in the Middle Jurassic. 相似文献
79.
通过对藏东地区芒康盆地拉屋拉组高钾岩体(粗面岩体)2个代表性样品的LA-ICP-MS锆石U-Pb同位素年龄测试,获得该岩体的形成时代。岩石蚀变较轻,主要由长石(斜长石、钾长石)和黑云母组成;其LA-ICP-MS锆石U-Pb测年得到的加权平均年龄分别为(35.2±1.3)Ma和(36.4±0.3)Ma。这些测年值为高钾岩体的形成提供了一个准确时限。同时表明,芒康盆地高钾岩体属晚始新世的产物,为藏东地区金沙江-红河构造带的重要组成部分,也是金沙江-红河构造带发生局部的陆内俯冲的又一具体表现。 相似文献
80.
Zircon U-Pb SHRIMP ages of eclogites from the North Qilian Mountains in NW China and their tectonic implication 总被引:9,自引:5,他引:4
SONG Shuguang ZHANG Lifei NIU Yaoling SONG Biao ZHANG Guibing & WANG Qianjie . MOE Key Laboratory of Orogenic Belts Crustal Evolution De-partment of Geology Peking University Beijing China . Department of Geology University of Houston Houston TX USA . Beijing SHRIMP Centre Institute of Geology CAGS Beijing China Correspondence should be addressed to Zhang Lifei 《科学通报(英文版)》2004,49(8):848-852
TheNorthQilianMountainsattheboundarybe-tweenGansuandQinghaiProvincesareafamousCaledo-nianplatesuturezoneinthenorthwesternChina.Thissuturezoneis80to100kmwideandextendsintheNWdirectionparalleltotheNorthQaidamUHPbeltinthesouth[1,2].Itconsistspredominantlyofophiolite,island-arccomplexandhigh-presuremetamorphicrocks[38],andshowstypicalfeaturesofPacific-type[9](orB-type)sub-ductionzone.Spatially,thehigh-pressurerockscanbesubdividedintohigh-gradeblueschistbeltandlow-gradeblueschistbelt[5,6].Th… 相似文献