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扬子克拉通及华北克拉通大陆岩石圈地幔碳同位素组成及其差异:金刚石碳同位素原位测试证据 被引量:11
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作者 陈华 丘志力 +7 位作者 陆太进 STERN Richard stachel thomas 孙媛 张健 柯捷 彭淑仪 秦社彩 《科学通报》 EI CAS CSCD 北大核心 2013年第4期355-364,共10页
金刚石碳同位素组成和对比是了解克拉通大陆岩石圈地幔物质组成及其演化的窗口.本文用二次离子质谱(SIMS)方法对产于华北克拉通(山东蒙阴和辽宁瓦房店)和扬子克拉通(湖南沅水流域)的11颗金刚石不同生长层的碳同位素组成进行了123个点高... 金刚石碳同位素组成和对比是了解克拉通大陆岩石圈地幔物质组成及其演化的窗口.本文用二次离子质谱(SIMS)方法对产于华北克拉通(山东蒙阴和辽宁瓦房店)和扬子克拉通(湖南沅水流域)的11颗金刚石不同生长层的碳同位素组成进行了123个点高精度原位(in-situ)测试.结果显示,华北克拉通和扬子克拉通金刚石碳同位素组成存在一定差异;华北克拉通金刚石早期生长"核心"碳同位素??13C组成平均为?3.0‰(VPDB),分布范围为?6.0‰~?2.0‰,与全球橄榄岩型金刚石一致;扬子克拉通金刚石早期"核心"??13C平均为?7.4‰,分布范围为?8.6‰~?3.0‰,和榴辉岩型金刚石特点一致;3个产地单颗金刚石不同生长层碳同位素变化不具有一致性,与是否含包裹体无关,但与金刚石是否存在溶蚀间断明显有关,证实金刚石生长过程地幔流体碳同位素组成不均一,碳储库(介质)不均一性对金刚石生长过程碳同位素变化的影响较分馏作用更为明显;与此同时,现有的测试结果显示,华北和扬子克拉通金刚石中心-边缘生长层碳同位素变化与氮含量之间缺乏相关性,反映我国两个克拉通金刚石生长过程中地幔流体碳和氮元素之间存在复杂的交换、地球化学环境可能相对开放.上述结果暗示,金刚石形成时扬子克拉通和华北克拉通地幔交代流体碳的组成及来源存在差异. 展开更多
关键词 金刚石 碳同位素 SIMS原位(in-situ)分析 大陆岩石圈地幔 克拉通
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Variations in carbon isotopic composition in the subcontinental lithospheric mantle beneath the Yangtze and North China Cratons:Evidence from in-situ analysis of diamonds using SIMS 被引量:7
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作者 CHEN Hua QIU ZhiLi +7 位作者 LU TaiJin STERN Richard stachel thomas SUN Yuan ZHANG Jian KE Jie PENG ShuYi QIN SheCai 《Chinese Science Bulletin》 SCIE EI CAS 2013年第1期99-107,共9页
The components and evolution of subcontinental lithospheric mantle beneath the North China Craton and the Yangtze Craton is a current topic in the geological study of China and the carbon isotopic composition of diamo... The components and evolution of subcontinental lithospheric mantle beneath the North China Craton and the Yangtze Craton is a current topic in the geological study of China and the carbon isotopic composition of diamond is one of the most direct probes into cratonic lithospheric mantle processes.In this paper,in-situ SIMS(Secondary Ion Mass Spectrometry) techniques were used to analyze the carbon isotope compositions at different internal growth zones of diamonds from Shandong and Liaoning in the North China Craton and Hunan in the Yangtze Craton.It was found that the carbon isotopic range of diamonds from the North China Craton are rather distinct from those of the Yangtze Craton;the former has a range of 6.0‰ to 2.0‰(relative to VPDB) with an average value of 3.0‰ in their core areas,which is consistent with global peridotitic diamonds;the diamonds from the Yangtze Craton,however,have a carbon isotopic range from 8.6‰ to 3.0‰ with an average value of 7.4‰ in their core areas,being more consistent with global eclogitic diamonds.The variations of carbon isotope ratios between different internal growth zones in individual diamonds were different in the three diamond localities studied.There was a clear correlation between changes in carbon isotopic composition and phases of diamond dissolution and new growth,while no correlation was observed between δ13C and internal inclusions.The variations suggest that the carbon isotopic compositions of mantle fluids were changing during the process of diamond crystallization,and that the heterogeneity of the carbon isotopic composition in mantle carbon reservoirs was a more important factor than carbon isotope fractionation in controlling the carbon isotopic compositions and their variation in diamonds.In addition,the preliminary results of in-situ nitrogen analyses demonstrated that the variation of carbon isotopic compositions between the core and outer growth zones does not correlate with nitrogen abundances,implying either that diamonds crystallized in an open environment or that the carbon isotopic composition and nitrogen contents in mantle fluids were controlled by other,not yet understood factors.The experimental results provide hints that the isotopic composition of carbon and its original sources were different in metasomatic fluids controlling diamond formation in the mantle beneath the North China Craton and the Yangtze Craton. 展开更多
关键词 碳同位素组成 扬子克拉通 岩石圈地幔 中国北方 原位分析 SIMS 钻石 证据
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