Grand Comore Island:: A well-constrained "low 3He/4He" mantle plume
Grand Comore Island:: A well-constrained "low 3He/4He" mantle plume
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DOI：
10.1016/j.epsl.2005.02.029
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发表时间：
2005-05-15
影响因子：
5.3
通讯作者：
Schlosser, P
中科院分区：
文献类型：
--
作者：
Class, C;Goldstein, SL;Schlosser, P
我们报告了来自大科摩罗岛的碱性玄武岩和玄武质熔岩流样品中He同位素（He-3/He-4）的变化，并补充了现有的[1，2] [C.同学们，S.L.海洋盆地中的地幔柱-岩石圈相互作用：来自源矿物学的约束。地球星球。Sci.信件：150（1997）245-260，C.同学们，S.L.戈尔茨坦河Altherr，P. Bachechlery，洋盆中羽流-岩石圈相互作用的过程--大科摩罗的案例。J. Petrel.，39（5）（1998）881903]和新的Sr-Nd-Pb同位素比值以及主元素和微量元素丰度。本文还报道了来自特里斯坦-达库尼亚和戈夫群岛以及肯尼亚胡里山的样品的He同位素数据。大科摩罗He-3/He-4比率在5.05至7.08 R-A之间（He-4/He-3约为141，000至101，000）。大科摩罗熔岩的化学和Sr-Nd-Pb同位素变化以前被证明反映了来自深地幔柱和浅岩石圈地幔的熔体[1-3] [C.同学们，S.L.海洋盆地中的地幔柱-岩石圈相互作用：来自源矿物学的约束。地球星球。Sci.信件：150（1997）245-260，C.同学们，S.L.戈尔茨坦河Altherr，P. Bachechlery，洋盆中羽流-岩石圈相互作用的过程--大科摩罗的案例。J.汽油，39（5）（1998）881-903，C. Claude-Ivanaj，B. Bourdon，C. J. Allegre，《大科摩罗岛的镭-钍-锶同位素系统学：地幔柱-岩石圈相互作用的案例研究》。地球星球。Sci. Lett. 164（1998）99-117]。以岩石圈为主的端元（拉格里尔火山）在[He]=36-428 x 10（-9）ccSTP/g的范围内显示出均匀的He-3/He-4比值，误差在6.75-7.08 R-A（He-4/He-3近似为106，000 - 101，000）范围内。受到Sr、Nd、Pb同位素比值的限制，（Karthala火山岩套的）羽流端元显示出一致较低的He-3/He-4比值，在[He]= 11-136 x 10（-9）ccSTP/g的范围内，为5.05-5.41 R-A（He-4/He-3约为141，000 - 132，000）。所有样品的Sr-Nd-He同位素比值之间表现出良好的相关性，表明大科摩罗He-3/He-4比值没有显着的地壳污染的影响，并反映最近的混合羽和岩石圈衍生的熔体。大科摩罗岩石圈保留了类似于MORB的氦同位素组成，这表明岩石圈地幔的角闪石交代作用[1] [C。同学们，S.L.海洋盆地中的地幔柱-岩石圈相互作用：来自源矿物学的约束。地球星球。Sci.信件：150（1997）245-260]发生在科摩罗羽流到达之前。科摩罗地幔柱的He-3/He-4 = 5.2 +/- 0.2 R-A（He-4/He-3约为137，000 +/- 5000）证实了“低He-3/He-4”地幔柱的存在。OIB的全球汇编表明，来自“低He-3/He-4”羽流的OIB形成了全球OIB数据集的大致三角形分布的一个“侧面”，即Nd-143/Nd-144与Pb-206/Pb-204和Pb-208/Pb-204，包括最低的Nd与最高的Pb同位素比值。低He-3/He-4羽流相对于其它羽流更富集Th和U。(C)2005 Elsevier B.V保留所有权利。
We report He isotope (He-3/He-4) variations in samples from alkali basaltic and basanitic lava flows from Grande Comore Island complemented by existing[1,2] [C. Class, S.L. Goldstein, Plume-lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245-260, C. Class, S.L. Goldstein, R. Altherr, P. Bachechlery, The process of plume-lithosphere interaction in the ocean basins-the case of Grande Comore. J. Petrel., 39 (5) (1998) 881903] and new Sr-Nd-Pb isotope ratios and major and trace element abundances. He isotope data in samples from Tristan da Cunha and Gough islands and the Huri Hills in Kenya are reported also. Grande Comore He-3/He-4 ratios vary between 5.05 and 7.08 R-A (He-4/He-3 approximate to 141,000-101,000). Chemical and Sr-Nd-Pb isotopic variations of Grande Comore lavas were previously shown to reflect melts derived from the deep mantle plume and the shallow lithospheric mantle[1-3] [C. Class, S.L. Goldstein, Plume-lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245-260, C. Class, S.L. Goldstein, R. Altherr, P. Bachechlery, The process of plume-lithosphere interaction in the ocean basins-the case of Grande Comore. J. Petrol., 39 (5) (1998) 881-903, C. Claude-Ivanaj, B. Bourdon, C.J. Allegre, Ra-Th-Sr isotope systematics in Grande Comore Island: a case study of plume-lithosphere interaction. Earth Planet. Sci. Lett. 164 (1998) 99-117]. The lithosphere-dominated end-member (La Grille volcano) shows uniform He-3/He-4 ratios within error of 6.75-7.08 R-A (He-4/He-3 approximate to 106,000-101,000) over a range of [He]=36-428 x 10(-9) ccSTP/g. The plume end-member (of the Karthala volcano suite), as constrained by Sr, Nd, Pb isotope ratios, shows uniformly lower He-3/He-4 ratios with 5.05-5.41 R-A (He-4/He-3 approximate to 141,000-132,000) over a range of [He]= 11-136 x 10(-9) ccSTP/g. All samples show good correlations between Sr-Nd-He isotope ratios, indicating that the Grande Comore He-3/He-4 ratios are not significantly influenced by crustal contamination and reflect recent mixing between plume- and lithosphere-derived melts. The lithosphere beneath Grande Comore has retained its MORB-like helium isotopic composition, which suggests that the previously identified amphibole-forming metasomatism of the lithospheric mantle [1] [C. Class, S.L. Goldstein, Plume-lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245-260] occurred prior to the arrival of the Comoro plume. The well-constrained He-3/He-4 = 5.2 +/- 0.2 R-A (He-4/He-3 approximate to 137,000 +/- 5000) of the Comoro plume confirms the existence of "low He-3/He-4" mantle plumes. A global compilation of OIB shows that OIB from "low He-3/He-4" plumes form one "side" of the roughly triangular distribution of the global OIB data set in Nd-143/Nd-144 versus Pb-206/Pb-204 and Pb-208/Pb-204, encompassing the lowest Nd to the highest Pb isotope ratios. It is also shown that "low He-3/He-4" plumes are more enriched in Th and U relative to other plumes. (C) 2005 Elsevier B.V All rights reserved.