Isotopic composition of carbon in diamonds of diamondites: record of mass fractionation in the upper mantle
Isotopic composition of carbon in diamonds of diamondites: record of mass fractionation in the upper mantle
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DOI：
10.1016/j.gca.2003.10.007
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发表时间：
2004-04
影响因子：
5
通讯作者：
T. Maruoka;G. Kurat;G. Dobosi;C. Koeberl
中科院分区：
文献类型：
--
作者：
T. Maruoka;G. Kurat;G. Dobosi;C. Koeberl
已经获得了来源不明（可能来自南部非洲）的金刚石（框架石，多晶金刚石）中金刚石的碳同位素数据，其中含有少量石榴石（加上稀有的单斜辉石）。碳同位素丰度比显示出很宽的样本间和样本内范围。金刚石与“橄榄岩”或“榴辉岩”石榴石的δ 13 C变化是无法区分的，范围为−3.2至−27.9‰，峰值约为−18‰，表明相对于大多数含硅酸盐的单晶金刚石，13 C有所减少。这种13 C亏损可能是由C-O-H流体系统中同位素均匀的地幔源中C的质量分馏产生的。地幔中氧化还原条件不同的区域之间流动的流体可能提供了必要的载体。δ 13 C的变化可以用流体/熔体上升过程中氧化程度的不同来解释。
Carbon isotope data have been obtained for diamonds in diamondites (framesites, polycrystalline diamond) of unknown origin (presumably from southern Africa), which contain minor amounts of garnet (plus rare clinopyroxene). The carbon isotope abundance ratios show wide inter- and intra-sample ranges. The δ13C variations of diamonds from diamondites with “peridotitic” or “eclogitic” garnets are indistinguishable from each other, with a range from −3.2 to −27.9‰, and a peak around −18‰, indicating a depletion in13C relative to most silicate-bearing single crystal diamonds. This13C depletion could have been produced by mass fractionation of C from an isotopically homogeneous mantle source in a C-O-H fluid system. Fluids traveling between regions of varying redox conditions in the mantle could have provided the necessary vehicle. The variations of δ13C can be explained by different degrees of oxidation during the fluid/melt ascent.