Lithium isotopic systematics of peridotite xenoliths from Hannuoba, North China Craton: Implications for melt-rock interaction in the considerably thinned lithospheric mantle
Lithium isotopic systematics of peridotite xenoliths from Hannuoba, North China Craton: Implications for melt-rock interaction in the considerably thinned lithospheric mantle
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华北克拉通汉诺坝橄榄岩捕虏体锂同位素系统学：岩石圈地幔减薄中熔岩相互作用的意义
DOI：
10.1016/j.gca.2007.07.006
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发表时间：
2007-09
影响因子：
5
通讯作者：
J. F. Ying
中科院分区：
文献类型：
--
作者：
T. Moriguti;K. Kobayashi;H. F. Zhang;E. Nakamura;Y. J. Tang;J. F. Ying
汉诺坝第三纪玄武岩中橄榄岩捕虏体中共存矿物（ol、opx和cpx）的Li含量和同位素组成，揭示了在相当薄的岩石圈地幔中熔体-岩石相互作用过程中地幔矿物间Li同位素分馏的规律。矿物分析表明，相对于橄榄石（1.2-1.8ppm），cpx中Li明显富集（2.4-3.6ppm），表明橄榄岩受到了镁铁质硅酸盐熔体的地幔交代作用。块状橄榄石分离物（δ 7 Li =+3.3‰ ~+6.4‰）的同位素比共存的辉石（cpx中δ 7 Li =-3.3 ‰ ~-8.2 ‰，opx中δ 7 Li =-4.0 ‰ ~-6.7 ‰）重。如此大的变化表明Li元素和同位素不平衡。这一结论得到了现场西姆斯分析的矿物颗粒中存在显着的锂元素和同位素分带的结果。橄榄石和opx具有较低的锂浓度和较重的锂同位素的边缘比核心。δ 7 Li与Li浓度的这种反向相关表明Li同位素的扩散分馏作用。然而，在共存cpx的分区模式显示同位素较重的轮辋具有较高的锂丰度。δ 7 Li和Li浓度之间的这种正相关性表明存在熔融混合趋势。我们属性锂浓度和同位素分带矿物的两阶段扩散分馏耦合熔体-岩石相互作用的影响。最早期的熔体可能来自俯冲洋壳板片，其低δ 7 Li值是海水蚀变板片脱水过程中同位素分馏产生的。后期熔体来源于软流层，与橄榄岩相互作用，产生矿物颗粒中Li元素和同位素分带。这些数据为华北北方陆下岩石圈地幔中橄榄岩-熔体的多阶段相互作用提供了证据。
Li concentrations and isotopic compositions of coexisting minerals (ol, opx, and cpx) from peridotite xenoliths entrained in the Hannuoba Tertiary basalts, North China Craton, provide insight into Li isotopic fractionation between mantle minerals during melt–rock interaction in the considerably thinned lithospheric mantle. Bulk analyses of mineral separates show significant enrichment of Li in cpx (2.4–3.6ppm) relative to olivine (1.2–1.8ppm), indicating that these peridotites have been affected by mantle metasomatism with mafic silicate melts. Bulk olivine separates (δ7Li∼+3.3‰ to +6.4‰) are isotopically heavier than coexisting pyroxenes (δ7Li∼−3.3‰ to −8.2‰ in cpx, and −4.0‰ to −6.7‰ in opx). Such large variation suggests Li elemental and isotopic disequilibrium. This conclusion is supported by results from in situ SIMS analyses of mineral grains where significant Li elemental and isotopic zonations exist. The olivine and opx have lower Li concentrations and heavier Li isotopes in the rims than in the cores. This reverse correlation of δ7Li with Li concentrations indicates diffusive fractionation of Li isotopes. However, the zoning patterns in coexisting cpx show isotopically heavier rims with higher Li abundances. This positive correlation between δ7Li and Li concentrations suggests a melt mixing trend. We attribute Li concentration and isotope zonation in minerals to the effects of two-stage diffusive fractionation coupled with melt–rock interaction. The earliest melts may have been derived from the subducted oceanic slab with low δ7Li values produced by isotopic fractionation during the dehydration of the seawater-altered slab. Melts at later stages were derived from the asthenosphere and interacted with the peridotites, producing the Li elemental and isotopic zoning in mineral grains. These data thus provide evidence for multiple-stage peridotite–melt interaction in the lithospheric mantle beneath the northern North China Craton.
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影响因子：
5
作者：
Brenan, JM;Ryerson, FJ;Shaw, HF
通讯作者：
Shaw, HF
影响因子：
2.6
作者：
Yanjie Tang;Hong‐fu Zhang;Jifeng Ying
通讯作者：
Yanjie Tang;Hong‐fu Zhang;Jifeng Ying
影响因子：
3.9
作者：
T. Moriguti;Eizo Nakamura
通讯作者：
T. Moriguti;Eizo Nakamura
影响因子：
5
作者：
R. Tanaka;E. Nakamura
通讯作者：
R. Tanaka;E. Nakamura
DOI：
--
发表时间：
1980-05
期刊：
The West Virginia medical journal
影响因子：
--
作者：
Ullrich Ih;Lyons Mh;Guy Es
通讯作者：
Ullrich Ih;Lyons Mh;Guy Es