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
Chen ChenHuaQiuZhiliLuTaiJinRichard RichardStachelThomasSunYuanZhangJian JIANKe KeJie JiePeng PengShuYiQin QinSheCai
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Abstract:
在北方中国 Craton 和 Yangtze 下面的 subcontinental lithospheric 披风的部件和进化 Craton 是在钻石的同位素的作文是的中国和碳的地质的学习的一个当前的话题进 cratonic lithospheric 披风的最直接的探针之一处理。在这份报纸，在原处 SIMS (第二等的离子集体 Spectrometry ) 技术被用来在 Yangtze Craton 在北方中国 Craton 和湖南从山东和辽宁在钻石的不同内部生长地区分析碳同位素作文。这被发现从北方中国 Craton 的钻石的同位素的范围是的碳从那些相当不同 Yangtze Craton；前者有 6.0/ 的一个范围到 2.0 (相对 VPDB ) 在他们的核心区域 3.0 与一般水准珍视，它与全球 peridotitic 钻石一致；然而，从 Yangtze Craton 的钻石有碳有在他们的核心区域的 7.4 的平均价值的从 8.6 ～ 3.0 的同位素的范围，与全球 eclogitic 钻石更一致。在在单个钻石的不同内部生长地区之间的碳同位素比率的变化在地区学习了的三颗钻石是不同的。在在碳的变化之间有清楚的关联钻石溶解和新生长的同位素的作文和阶段，当没有关联在 13C 和内部包括之间被观察时。变化建议披风液体的同位素的作文在钻石结晶化的过程期间正在改变的碳，并且在披风碳水库的同位素的作文是的碳的异质一个更重要的因素比在控制碳的碳同位素分别在钻石的同位素的作文和他们的变化。另外，初步的结果在原处，氮分析证明碳的变化在核心之间的同位素的作文和外部生长地区不与氮丰富相关，暗示钻石在开的环境结晶或同位素的作文和氮在披风液体满足的碳被其它控制，不是还理解因素。试验性的结果提供碳和它的原来的来源的同位素的作文在在北方中国 Craton 和 Yangtze Craton 下面在披风控制钻石形成的交代矿床液体是不同的提示。Cite
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Research Article| September 01, 2001 Exotic lithosphere mantle beneath the western Yangtze craton: Petrogenetic links to Tibet using highly magnesian ultrapotassic rocks Yi-Gang Xu; Yi-Gang Xu 1Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou, China Search for other works by this author on: GSW Google Scholar Martin A. Menzies; Martin A. Menzies 2Department of Geology, Royal Holloway University of London, Egham TW20 OEX, UK Search for other works by this author on: GSW Google Scholar Matthew F. Thirlwall; Matthew F. Thirlwall 2Department of Geology, Royal Holloway University of London, Egham TW20 OEX, UK Search for other works by this author on: GSW Google Scholar Guang-Hong Xie Guang-Hong Xie 3Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou, China Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (9): 863–866. https://doi.org/10.1130/0091-7613(2001)029<0863:ELMBTW>2.0.CO;2 Article history received: 11 Dec 2000 rev-recd: 07 May 2001 accepted: 21 May 2001 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Yi-Gang Xu, Martin A. Menzies, Matthew F. Thirlwall, Guang-Hong Xie; Exotic lithosphere mantle beneath the western Yangtze craton: Petrogenetic links to Tibet using highly magnesian ultrapotassic rocks. Geology 2001;; 29 (9): 863–866. doi: https://doi.org/10.1130/0091-7613(2001)029<0863:ELMBTW>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Highly magnesian ultrapotassic rocks that erupted ca. 30–40 Ma on either side of the northern Ailao Shan–Red River fault (western Yunnan) have initial 87Sr/86Sr values of 0.7064–0.7094 and ϵNd values of −3.8 to −4.6. Such isotopic compositions are distinct from asthenospheric signatures and most likely probe the lower lithosphere. Sm-Nd model age and trace element data for the Yunnan lavas indicate that at the time of eruption the mantle source was an old (>1 Ga) mica-bearing spinel harzburgite. However, such Proterozoic enriched lithospheric mantle could not have survived the thermo-tectonic processes associated with continental flood volcanism that affected the same part of the western Yangtze craton 250 Ma. Emeishan flood basalt volcanism would have purged the shallow mantle of all its fusible constituents and any enrichments would be younger than 250 Ma. We propose that the lithosphere mantle beneath the western Yangtze craton is exotic and probably represents part of the Tibetan lithosphere extruded to the east 40– 50 Ma. The Indo-Asia collision provides a suitable mechanism and explains the link between the west Yangtze craton and northern Tibet in terms of provenance (Sr-Nd) and the similar two-dimensional seismic velocity structure. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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Abstract We present mineralogical and geochemical compositions of mantle xenoliths from two Cenozoic basalt localities of the northeastern North China Craton. These xenoliths include lherzolite, harzburgite, and websterite. They are generally fertile in major elements and different from the typical cratonic lithosphere, which is consistent with previous hypotheses regarding craton destruction. The ratios of 87Sr/86Sr and (La/Yb)N of clinopyroxenes (Cpx) in one lherzolite are relatively low in the core but high in the rim. The center of the Cpx grain has a high U concentration. Changes in trace elements and Sr isotopes indicate that later stage high 87Sr/86Sr melt metasomatism superimposed on the early hydrous melt/fluid. The Cpxs in some xenoliths are low in Ti/Eu but high in Ca/Al and light rare earth elements, which indicates carbonate melt metasomatism. 87Sr/86Sr is increased in the core and decreased in the rim of most Cpx grains, which reflects the superposition of two-stage metasomatism. The early agent should be high in 87Sr/86Sr, and the recent agent should be low in 87Sr/86Sr. The Cpxs in olivine websterite are low in 87Sr/86Sr (0.70220–0.70320), which reflects the recent metasomatism of asthenosphere-derived melt. Collectively, these observations reflect a three-stage modification of the lithospheric mantle. First-stage hydrous melt/fluid could come from the dehydration of young subducted plates. Second-stage melt/fluid of high 87Sr/86Sr could derive from the partial melting of the subducted altered oceanic crust, and the recent melt/fluid of low 87Sr/86Sr should be from the asthenosphere.
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