高校地质学报2012，Vol.18Issue(1)：62-73,12.
山东蓬莱新生代岩石圈地幔的异常锂同位素组成:橄榄岩包体的离子探针分析
Anomalous Lithium Isotopic Compositions of the Cenozoic Lithospheric Mantle Beneath Penglai, Shandong Province:The ion Probe Analyses of Peridotite Xenoliths
摘要
Abstract
Li contents and isotopic compositions of minerals in the peridotite xenoliths hosted by Cenozoic basalts from Penglai, Shandong Province have been measured using ion probe. The results show that the Li abundance ranges from 2.0 to 10.4 x 10 , 2.8 to 23.8 × 10‐6 and 3.3 to 59.7 × 10‐6 in olivine (ol), orthopyroxene (opx) and clinopyroxene (cpx), respectively, and the δ7 Li values varies from‐28.6 %o to +0.5 %o, ‐12.7 %o to +12.8%o and ‐41.5 %o to +22.6 %o in ol, opx and cpx, respectively. Both the Li contents and isotopic ratios deviate strongly from the normal mantle range and the equilibrated trend. These extreme disequilibria imply that the strong Li enrichments were induced by strong mantle metasomatic events. The high Li and δ7li enrichments of pyroxene reflected the nature of the recent mantle metasomatism that fed them, whereas the moderate Li enrichment and strong δ7 Li depletion in the olivines may record a relatively ancient low‐ δ7 Li signature. The reproduction of the measured profiles andthe decoupling of Li enrichment from the LREE‐depleted pattern in cpx suggest that both enrichment processes were relatively recent and transient. Accordingly, we conclude that the ‐pristine‐ recycled components with anomalous Li composition existed in the upper mantle beneath the eastern North China Craton (NCC). The fractionation of Li isotopic compositions in the recycled components was linked to the subduction of the Pacific plate beneath East Asia since the Mesozoic, and the recycled components were reactivated recently to feed these anomalous Li enrichments as recorded by the Penglai peridotite xenoliths.关键词
华北克拉通/地幔橄榄岩/锂同位素/地幔交代/再循环物质Key words
North China Craton/ mantle peridotite/ lithium isotopes/ mantle metasomatism/ recycled material分类
天文与地球科学引用本文复制引用
李佩,夏群科,Etienne DELOULE..山东蓬莱新生代岩石圈地幔的异常锂同位素组成:橄榄岩包体的离子探针分析[J].高校地质学报,2012,18(1):62-73,12.基金项目
国家自然科学基金项目(91014007,90714009) （91014007,90714009）
中-法合作项目和国家公派留学基金(2008634061)共同资助 （2008634061）
