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Retrograde metamorphism of the eclogite in North Qaidam,western China:Constraints by joint ^(40)Ar/^(39)Ar in vacuo crushing and stepped heating

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Geoscience Frontiers 2015年第5期6卷 759-770页

作者： Rongguo Hu jan wijbrans Fraukje Brouwer Linghao Zhao Min Wang Huaning Qiu State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of Sciences Department of Earth Sciences VU University Amsterdam University of Chinese Academy of Sciences

Two amphiboles and a syn-metamorphic quartz vein from the Yuka terrane,North Qaidam,western China,have been analyzed by joint40Ar/39Ar crushing in vacuo and stepwise heating *** crushing in vacuo results provide information to directly constrain the timing of fluid activity and the age of amphibolite-facies *** stepwise heating results could further be used to decipher the thermal history of the UHP *** from amphibolites and quartz vein within garnetamphibolite lens analyzed by in vacuo crushing yield similarly shaped age spectra and exhibit relatively flat age plateaus for the last several *** characteristics of gas release patterns and geochronological data testify to the presence of significant excess40Ar within the fluid *** age plateaux with weighted mean ages（WMA） ranges from 488 to 476 Ma for amphiboles and 403 Ma for quartz（2σ）.These data points constitute amphibole WMA yielding excellent isochrons with isochron ages of 469 and 463 Ma with initial40Ar/36Ar ratios of 520 and 334,*** isochron ages are interpreted to represent initial amphibolite-facies *** data points constituting the quartz age plateaux give an isochron age of 405 Ma with initial40Ar/36Ar ratio of 295,recording a significant aqueous fluid flow episode during the early *** spectra obtained by stepwise heating of amphibole residues remaining after crushing experiments are characterized by younger and relatively complex age spectra,which are probably influenced by the combined effects of resetting argon and/or mineral ***,we note that the spectra shapes have features in common:excluding the last two steps,minimum apparent ages are found at temperatures of around 500 ℃,corresponding to319 and 249 Ma,perhaps representing the time of isotopic resetting or resulting from release gas from mineral inclusions of,e.g.,biotite or *** apparent ages are obtained at temperatures of aro

关键词： 40Ar/39Ar techniques In vacuo crushing Amphibolite

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Metamorphic P-T Path Differences between the Two UHP Terranes of Sulu Orogen, Eastern China: Petrologic Comparison between Eclogites from Donghai and Rongcheng

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Journal of Earth Science 2018年第5期29卷 1151-1166页

作者： Zhuoyang Li Yilong Li jan R.wijbrans Qijun Yang Hua-Ning Qiu Fraukje M.Brouwer School of Earth Sciences State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Geology & Geochemistry Group Department of Earth Sciences VU Amsterdam College of Earth Sciences Guilin University of Technology Faculty of Earth Resources Key Laboratory of Tectonics and Petroleum Resources Ministry of Education China University of Geosciences

The Sulu Orogen constitutes the eastern part of the Sulu-Dabie Orogen formed by Triassic collision between the Sino-Korean and Yangtze plates. An HP Slice Ⅰ and two UHP slices Ⅱ and Ⅲ with contrasting subduction and exhumation histories within the Sulu Orogen were postulated. This study presents the metamorphic P-T paths of eclogites from the two UHP belts constructed by petrog- raphy, mineral chemistry and Perple_X P-T pseudosection modeling in the MnC（K）NFMASHO system. Eclogites from Slice Ⅲ mainly consist of omphacite, garnet and quartz, with minor rutile, ilmenite, amphibole and phengite. Eclogites from Slice Ⅱ show a porphyroblastic texture with epidote porphyroblasts and garnet, omphacite, phengite, quartz and rutile in matrix. Pseudosection modeling reveals that eclogites from Slice Ⅱ witness a peak metamorphism of eclogite-facies under conditions of 3.1-3.3 GPa and 660-690 ℃, and a retrograde cooling decompression process. The eclogites from Slice Ⅲ record a heating decompressive P-T path with a peak-P stage of 3.2 GPa and 840℃ and a peak-T stage of 2.4 GPa and 950 ℃, suggesting an apparent granulite-facies metamorphism overprint during exhumation. Both eclogites recorded clockwise P-T paths with peak P-T conditions suggesting a subduction beneath the Sino-Korean Plate to -100-105 km depth. Combined with tectonic scenarios from previous studies, it is concluded that the two UHP crustal slices in the Sulu terrane have a similar geodynamic evolution, but the UHP rocks in Slice Ⅱ exhumed after the eclogitic peak-pressure conditions earlier than that of Slice Ⅲ. The existence of Slice Ⅱ diminished the buoyancy force on Slice Ⅲ, resulting in a granulite-facies overprint on Slice Ⅲ. The Sulu orogenic belt is made up of different crustal slices that underwent different subduction and exhumation histories, rather than a single unit.

关键词： petrology UHP metamorphism exhumation process Sulu Orogen.

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Occurrence of Excess ^40Ar in Amphibole： Implications of ^40Ar/^39Ar Dating by Laser Stepwise Heating and in vacuo Crushing

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Journal of Earth Science 2018年第2期29卷 416-426页

作者： Rong-Guo Hu Xiu-Juan Bai jan wijbrans Fraukje Brouwer Yi-Lai Zhao Hua-Ning Qiu College of Earth Sciences Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration Guilin University of Technology Guilin 541004 China Geology & Geochemistry Cluster Department of Earth Sciences VU Amsterdam De Boelelaan 1085 1081 HV Amsterdam The Netherlands Key Laboratory of Tectonics and Petroleum Resources Ministry of Education China University of Geosciences Wuhan 430074 China State Key Laboratory of Isotope Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China

ABSTRACT： The joint methods of ^40Ar/^39Ar laser stepwise heating and in vacuo crushing have been applied to date amphiboles from the North Qaidam ultra-high pressure metamorphic amphibolites. Two amphibole samples analyzed by laser heating yielded saddle-shaped age spectra with total gas ages of 574.5±2.5 and 562.5=±2.5 Ma. These ages are much older than the reported zircon U-Pb ages （-495 Ma） from Yuka eclogite, indicating the presence of excess ^40Ar. In order to decipher the occur- rence of excess ^40Ar and constrain the age of amphibolite-facies retrogression, two duplicate amphibole samples were further employed for ^40Ar/^39Ar in vacuo crushing analyses. Both samples exhibit similar monotonically declining release spectra, which are characterized by rapid decline of anomalously old apparent ages in the early steps. The data of the late steps yielded concordant apparent ages with pla- teau ages of 460.9±1.2 and 459.6±1.8 Ma. We interpret that gases released in the early steps derive from the significant excess ^40Ar containing secondary fluid inclusions （SFIs） due to their distribution characteristics along cracks leading to be easily extracted, whereas those released in the later steps rep- resent the contribution of the small primary fluid inclusions （PFIs）.

关键词： ^40Ar/^39Ar dating in vacuo crushing amphibole fluid inclusions.

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柴北缘鱼卡多硅白云母40Ar/39Ar年代学研究及其外来40Ar来源探讨

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地学前缘 2014年第1期21卷 216-227页

作者：胡荣国邱华宁 jan wijbrans Fraukje BROUWER 王敏同位素地球化学国家重点实验室中国科学院广州地球化学研究所广东广州510640 Department of Petrology VU University AmsterdamDe Boelelaan 1085 中国科学院大学北京100049

采用激光阶段加热40Ar/39Ar定年技术,选取柴北缘超高压变质带鱼卡地体超高压变质岩及其围岩的6个多硅白云母进行了Ar同位素分析,获得丰富年代学数据。榴辉岩和云母斜长角闪岩多硅白云母具有高Si、高Mg含量的特征,阶段加热给出复杂的表... 详细信息

采用激光阶段加热40Ar/39Ar定年技术,选取柴北缘超高压变质带鱼卡地体超高压变质岩及其围岩的6个多硅白云母进行了Ar同位素分析,获得丰富年代学数据。榴辉岩和云母斜长角闪岩多硅白云母具有高Si、高Mg含量的特征,阶段加热给出复杂的表观年龄图谱,总气体年龄(708~534 Ma)和等时年龄(681~513Ma)都明显老于区内榴辉岩锆石U-Pb年龄,暗示样品含大量外来40Ar。相比之下,围岩花岗质片麻岩和白云母石英片岩多硅白云母具有相对低Si高Fe的特征,阶段加热给出平坦的40Ar/39Ar年龄谱,对应坪年龄分别为454和418Ma。构成年龄坪的数据点形成了线性关系良好的反等时线,并获得同坪年龄一致的等时年龄,能与区域地质年龄很好地吻合。坪年龄454Ma解释为花岗质片麻岩冷却到约400℃时的时间,同时也代表了鱼卡变质岩在经历了深俯冲超高压变质作用后,从上地幔折返抬升至中-上地壳深度的时限;片岩多硅白云母坪年龄418Ma纪录的则是区内一次强韧性剪切事件发生的时代。考虑到榴辉岩和斜长角闪岩原岩为变基性玄武岩类,其主要含钾矿物角闪石的Ar封闭稳定性较高,同时在超高压变质过程中,它们处在一个相对封闭和缺乏流体活动的极端地质环境,所以认为鱼卡榴辉岩多硅白云母外来40Ar来自原岩而非后期渗入的流体,属于"继承"40Ar的范畴。

关键词：外来40Ar 继承40Ar 多硅白云母鱼卡地体超高压变质岩

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柴北缘锡铁山榴辉岩退变质成因角闪石^40Ar/^39Ar年代学研究

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岩石学报 2013年第9期29卷 3031-3038页

作者：胡荣国王敏 jan R wijbrans Fraukje M BROUWER 邱华宁中国科学院广州地球化学研究所同位素地球化学国家重点实验室广州510640 Department of Earth Sciences VU University AmsterdamDe Boelelaan 10851081HV AmsterdamNetherlands 中国科学院大学北京100049

采用激光阶段加热^40Ar/^39Ar技术,对柴达木盆地北缘锡铁山榴辉岩退变质作用形成的榴闪岩和斜长角闪岩之角闪石进行了定年分析。09NQ44Amp来自榴闪岩,各阶段表观年龄（以现代空气氩^40Ar/^36Ar比值295.5扣除非放射性成因^40Ar）构成了... 详细信息

采用激光阶段加热^40Ar/^39Ar技术,对柴达木盆地北缘锡铁山榴辉岩退变质作用形成的榴闪岩和斜长角闪岩之角闪石进行了定年分析。09NQ44Amp来自榴闪岩,各阶段表观年龄（以现代空气氩^40Ar/^36Ar比值295.5扣除非放射性成因^40Ar）构成了单调下降的阶梯状年龄谱。在反等时线图解上,2~4阶段数据点和5~18阶段数据点分别构成了两条等时线,等时年龄分别为427.6±10Ma和425.1±2.6Ma,对应的初始40Ar/36Ar比值则分别为435.2±6.1和705.3±13。角闪石09NQ43Amp来自榴辉岩强烈退变质作用形成的斜长角闪岩,40Ar/39Ar阶段加热分析也获得单调下降的年龄谱,在反等时线图解上其数据点3~6阶段和7~16阶段分别构成了两条等时线,等时年龄分别为418.9±2.9Ma和418.1±2.1Ma,对应的初始40Ar/36Ar比值则分别为493.7±2.8和685.8±34.3。等时线截距值高于现代大气40Ar/36Ar比值,表明角闪石中含过剩40Ar。同时,由低温和中-高温阶段加热数据点分别构成两条等时年龄基本一致,截距值却明显不同的等时线,表明在角闪石热力学性质不同的源区,存在两期明显不同且未混合的初始捕获Ar组分。等时年龄425~418Ma代表的是锡铁山榴辉岩角闪岩相退变质作用发生的时间。等时线图解法虽然有效的校正了角闪石中的过剩40Ar,但仅根据表观年龄图谱和等时线图谱还无法清晰判断过剩40Ar在角闪石中的赋存状态,有待进一步探讨。

关键词： 40Ar/39Ar法捕获Ar 角闪石激光阶段加热等时线图解

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柴北缘锡铁山花岗质片麻岩深熔作用年代和冷却历史:来自浅色体^(40)Ar/^(39)Ar年代学证据

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大地构造与成矿学 2016年第1期40卷 125-135页

作者：胡荣国邱华宁 jan R.wijbrans Fraukje M.BROUWER 何立言王敏桂林理工大学广西隐伏金属矿产勘查重点实验室广西桂林541004 中国科学院广州地球化学研究所同位素地球化学国家重点实验室广东广州510640 Department of Petrology VU University Amsterdam

长英质浅色体广泛出露于柴北缘造山带中段锡铁山地体花岗质片麻岩中,多呈脉状、不规则透镜状顺区域片麻理走向产出,主要由钾长石、斜长石、角闪石、石英以及少量黑云母组成,是黑云母花岗质片麻岩深融作用的产物。温压估算获得其形成条件... 详细信息

长英质浅色体广泛出露于柴北缘造山带中段锡铁山地体花岗质片麻岩中,多呈脉状、不规则透镜状顺区域片麻理走向产出,主要由钾长石、斜长石、角闪石、石英以及少量黑云母组成,是黑云母花岗质片麻岩深融作用的产物。温压估算获得其形成条件为P=(6.5~9.6)′102 MPa,T=640~690℃,达麻粒岩相。选取浅色体角闪石和钾长石单矿物进行激光阶段加热^(40)Ar/^(39)Ar定年。角闪石共进行了17个阶段,其中3~17阶段数据形成平坦年龄谱,坪年龄为442.5±4.0 Ma;构成年龄坪的数据对应的等时线年龄为441.6±3.9 Ma,相应初始捕获氩比值为303±4,暗示该角闪石样品不含过剩^(40)Ar。坪年龄~442.5 Ma解释为角闪石初始结晶年龄,代表了锡铁山地区黑云母片麻岩发生深融(混合岩化)的时代。共生钾长石阶段加热获得一个低温和一个高温坪,坪年龄分别为307.5±2.9 Ma和323.3±3.0 Ma;等时线图谱暗示该钾长石样品未受过剩^(40)Ar干扰。坪年龄分别代表浅色体冷却到钾长石封闭温度~200℃和~250℃的时间。^(40)Ar/^(39)Ar定年结果显示锡铁山黑云母片麻岩深熔作用后经历了低速抬升(0.1~0.2 km/Ma)和缓慢冷却(3~3.6℃/Ma)的演化历史。

关键词：浅色体花岗质片麻岩深熔作用 40Ar/39Ar定年冷却历史锡铁山地体

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