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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >Primary magmatic amphibole in Archaean meta-pyroxenite from the central zone of the Limpopo Complex, South Africa
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Primary magmatic amphibole in Archaean meta-pyroxenite from the central zone of the Limpopo Complex, South Africa

机译：来自南非的林蛙复合物中央区的大型岩石态锥形

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摘要

Mapping of a section along the Sand River in the high-grade metamorphic Central Zone of the Limpopo Complex, South Africa, delineated meta-peridotite, meta-pyroxenite and meta-gabbro occurring as conformable layers in the host supracrustal rocks. The ultramafic to mafic rocks form part of the Palaeoarchaean Messina layered intrusion. Modal mineralogy of the pyroxenite is typical of an amphibole websterite. Although metamorphic re-equilibration of the pyroxenite is obvious, no new metamorphic mineral had formed. Detailed evaluation of grain margins between the prominent minerals (amphibole, clinopyroxene, orthopyroxene and olivine) indicated two types of grain margins, with their mutual relation used to support the poly-metamorphic nature of overprint on the pyroxenite. Inclusion-host relations between the prominent minerals helped to infer the original igneous order of crystallization. Petrographic and mineral chemical analyses permitted distinction of two varieties of amphiboles, the earlier occurring as polygonal grains as well as inclusions in olivine and pyroxenes, and the later occurring along grain margins, often replacing clinopyroxene. Two varieties of magnetite were also recognized, an earlier Cr-rich variety occurring as inclusions and interstitial grains, and a later Cr-poor variety occurring together with serpentine. Application of geothermobarometers indicate metamorphic re-equilibration conditions (-830 to 879 degrees C; 5.3 to 6.1 kbars). Comparison with compositional characteristics of primary and secondary/metamorphic amphiboles reported from Archaean ultramafic rocks occurring elsewhere, Alaskan-type layered intrusions, and metasomatised rocks from the vicinity of the study area, helped to place constraints on the nature of amphiboles reported here. The identification of primary magmatic amphiboles in the meta-pyroxenite implies likely formation from a hydrous parental magma in the Archaean mantle.
机译：沿着林蛙复合物，南非，划清的荟萃岩石，Meta-Pyroxenite和Meta-Gabbro的高档变质中心区沿沙滩沿着砂河映射，作为主持人的适系层。 MAFIC ROCKS的uterAMAFIC构成了PaleoAthaean Messina分层侵入的一部分。曲克氏岩的模态矿物是典型的锥形织物。虽然曲克酸盐的变质重新平衡显而易见，但没有形成新的变质矿物。详细评估突出矿物质（锥形，斜曲烯，矫酯，橄榄石和橄榄石）之间的谷物边缘的评价表明了两种类型的晶粒余量，其相互关系用于支持冰六岩上的套印的多变质性质。涵盖着名矿物质之间的宿主关系有助于推断出原始的结晶秩序。岩体和矿物化学分析允许两种倒像的倍数分析，较早发生的糖粒以及橄榄石和辉石中的夹杂物，以及沿谷物边缘发生的后来发生，通常更换临床。还认识到两种磁铁矿，较早的CR丰富的品种作为夹杂物和间质性谷物，以及与蛇形一起发生的后期CR差异。地热测定仪的应用表示变质重新平衡条件（-830至879摄氏度; 5.3至6.1 kbars）。与来自研究区域附近的阿拉斯加型分层侵入和从研究区附近发生的初级和次要/变质倒话的组成特征的比较，从研究区域附近，有助于对这里报道的两栖组的性质进行限制。在Meta-冰石中鉴定原发性岩石吡摩尔意味着来自古老的父母岩石中的湿父母岩石中的形成。

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