Lower mantle mineral associations in diamonds from Sao Luiz, Brazil-猫眼课题宝

巴西圣路易斯钻石中的下地幔矿物组合

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Joe Boyd;Yingwei Fei;C. Bertka;B. Mysen;B. Harte;2M. T J. W. HARRIS;Hutchison;3G. R. Watta;M. C. Wilding

-来自巴西冲积矿床Sao Luiz的一套钻石，显示出前所未有的(Mg，Fe)O(铁方镁石-镁铁榴石-fPer)包裹体，在正常情况下，这些包裹体最有可能来自下地幔。此外，同一钻石中偶尔出现无色包裹体，其成分为(Mg，Fe)Si03和CaSi03，与镁硅钙钛矿(MgSiPvk)和钙钙钛矿(CaSiPvk)相对应，这两种相也可能出现在下地幔常见的橄榄岩成分中。同一组金刚石中的铝相包括：(1)石榴石组成的相(TAPP)，(Mg，Fe)Al2Si30.12，但具有独特的四方晶体结构；(2)富Al的MgSiPvk；(3)Al203相。与其他地区钻石中偶尔报告的镁fPer包裹体不同，Sao Luiz fPer的成分范围非常广泛，Fe2+/(Fe2++mg)从0.14到0.62不等。在其中一些fPer包裹体中，镁铁氧体尖晶石的超细尺度出溶

-A suite of diamonds from the Sao Luiz, alluvial deposit, Brazil, shows an unprecedented abundance of (Mg,Fe)O (ferropericlase-magnesiowiistite - fPer) inclusions, which under normal circum-stances are most likely to be derived from the lower mantle. Furthermore, occasional colourless inclusions in the same diamonds have compositions of (Mg,Fe)Si0 3 and CaSi0 3, corresponding to those of the phases MgSi-perovskite (MgSiPvk) and CaSi-perovskite (CaSiPvk), which are also expected to occur in the common peridotitic compositions of the lower mantle. Aluminous phases in the same suite of diamonds include: (1) a phase (TAPP) of garnet composition, (Mg,Fe)AI 2 Si 3 0 12 but with a distinct tetragonal crystal structure; (2) an AI-rich MgSiPvk; (3) an Al 2 0 3 phase. Unlike the occasional and always magnesian fPer inclusions reported in diamonds from other localities, the Sao Luiz fPer have an extremely wide range of composition, with Fe 2 + /(Fe 2 + + Mg) ranging from 0.14 to 0.62. In some of these fPer inclusions very fine scale exsolution of a magnesioferrite spinel

Lower mantle mineral associations in diamonds from Sao Luiz, Brazil

巴西圣路易斯钻石中的下地幔矿物组合

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