The role of intercumulus residua in the formation of pegmatoid associated with the UG2 chromitite, Bushveld Complex
The role of intercumulus residua in the formation of pegmatoid associated with the UG2 chromitite, Bushveld Complex
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积云间残余物在与 UG2 铬铁矿、布什维尔德杂岩相关的伟晶石形成中的作用
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
S. Barry
中科院分区：
文献类型：
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作者：
R. Cawthorn;S. Barry
Bushveld杂岩临界带中的UG2铬铁矿被辉石岩包裹，最上层50 cm为辉石岩。其上为橄榄石辉石岩。与表层和下部硅酸盐岩石相比，K2O、Ba、Zr和P2O5在类伟晶中没有明显的富集性。全岩镁/(镁+铁)比值和标准斜长石组成在粗粒岩性和相邻细粒岩性之间没有系统差异。坑洞与UG2有关，但UG2和Merensky之间不存在地理或结构关系。通过正常的和凹陷的UG2铬铁矿的地球化学特征的比较表明，没有证据表明流体通过Merensky凹坑的通道。这些观察结果不支持岩浆阶段残留液体或流体优先被捕获或与之反应的假设，即在这些伟晶状层位或坑洞的形成过程中。火成岩指示有热的原始岩浆注入。
The UG2 chromitite in the Critical Zone of the Bushveld Complex is underlain by pyroxenite, the uppermost 50 cm of which is a pegmatoidal pyroxenite. Overlying it is an olivine pyroxenite. Concentrations of K2O, Ba, Zr and P2O5 show no enrichment in pegmatoid relative to over‐ and underlying silicate rocks. Whole rock Mg/(Mg+Fe) ratios and normative plagioclase compositions show no systematic differences between coarsegrained and adjacent finer‐grained lithologies. Potholes are associated with the UG2 but no geographic or structural relationships exist between UG2 and Merensky potholes. Comparison of geochemical profiles through normal and potholed UG2 chromitite show no evidence of fluid channelling as has been documented through Merensky potholes. These observations do not support the hypotheses of preferential trapping of, or reaction with, residual liquid or fluid at the magmatic stage in these pegmatoidal horizons or in the formation of potholes. Injection of hot primitive magma is indicated by the f...