THE MAJUAGAA KIMBERLITE DIKE, MANIITSOQ REGION, WEST GREENLAND: CONSTRAINTS ON AN Mg-RICH SILICOCARBONATITIC MELT COMPOSITION FROM GROUNDMASS MINERALOGY AND BULK COMPOSITIONS
THE MAJUAGAA KIMBERLITE DIKE, MANIITSOQ REGION, WEST GREENLAND: CONSTRAINTS ON AN Mg-RICH SILICOCARBONATITIC MELT COMPOSITION FROM GROUNDMASS MINERALOGY AND BULK COMPOSITIONS
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西格陵兰岛马尼特索克地区马朱阿加金伯利岩岩脉：来自地块矿物学和块体成分对富镁硅碳质熔体成分的限制
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发表时间：
2008
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影响因子：
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通讯作者：
K. Sand
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作者：
T. Nielsen;K. Sand
西格陵兰南部Maniitsoq地区的Majuagaa金伯利岩岩脉有564 Ma的历史，长2.5 km，宽达2 m。它暴露良好，非常新鲜，可以进行详细的岩相学和化学研究。很少或没有观察到蛇纹化，主要的岩相特征和颗粒形态被保留。岩脉是含金刚石的，并携带捕虏体（高达30厘米），巨晶和金伯利岩的特点macrocrysts。根据基质金云母、硅镁云母和富镁钛尖晶石的共生和成分，岩脉被归类为金伯利岩，尽管富含碳酸盐，并且明显缺乏真正的浅成金伯利岩的特征。橄榄石巨晶、大晶和微晶都是捕晶，而微斑晶是捕晶微晶被平衡橄榄石过度生长。大多数橄榄石（最大37重量%）根据Ni的质量平衡，发现是捕虏晶。平均散装组成的熔体中涉及的堤比较以及组-1金伯利岩。校正为捕虏晶橄榄石和钛铁矿，熔体具有硅碳酸岩的组成，并与实验熔体在非常低的程度的部分熔融的CO2轴承二辉橄榄岩形成比较。
The Majuagaa kimberlite dike in the Maniitsoq region, southern West Greenland, is 564 Ma old, 2.5 km long, and up to 2 m wide. It is well exposed and very fresh, allowing detailed petrographic and chemical investigations. Little or no serpentinization is observed, and primary petrographic characteristics and grain morphologies are preserved. The dike is diamondiferous and carries xenoliths (up to 30 cm), megacrysts and macrocrysts characteristic of kimberlite. On the bases of the paragenesis and compositions of groundmass phlogopite, geikielite and Mg–Ti-enriched spinel, the dike is classified as kimberlite, despite being carbonate-rich and the apparent absence of monticellite characteristic of many occurrences of bona fide hypabyssal kimberlite. Olivine megacrysts, macrocrysts and microcrysts are all xenocrystic, whereas microphenocrysts are xenocrystic microcrysts overgrown by equilibrium olivine. Most olivine (max. 37 wt.%) is found to be xenocrystic on the basis of Ni mass balance. The average bulk composition of the melt involved in the dike compares well with Group-1 kimberlite. Corrected for xenocrystic olivine and ilmenite, the melt has the composition of a silicocarbonatite and compares with experimental melts formed at very low degrees of partial melting of CO2-bearing lherzolite.