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首页> 外文期刊>Contributions to Mineralogy and Petrology >An insight into the first stages of the Ferrar magmatism: ultramafic cumulates from Harrow Peaks, northern Victoria Land, Antarctica
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An insight into the first stages of the Ferrar magmatism: ultramafic cumulates from Harrow Peaks, northern Victoria Land, Antarctica

机译：洞察法拉尔山岩的第一阶段：来自哈罗峰，维多利亚州北部的Ultramafic累积，南极洲

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A group of ultramafic xenoliths hosted in Cenozoic hypabyssal rocks from Harrow Peaks (northern Victoria Land, Antarctica) show textural and geochemical features far removed from anything previously observed in mantle xenoliths of this region and elsewhere in Antarctica. They consist of spinel-bearing lherzolites and harzburgites, characterised by a predominant equigranular texture with orthopyroxene modal contents remarkably higher in lherzolites (18-26 volume%) with respect to the harzburgite (13 vol%), one orthopyroxenite, and three composite xenoliths. The latter are formed by an olivine-dominant assemblage (olivine>70%) crosscut by large monomineralic (amphibole or clinopyroxene) or bimineralic (amphibole+clinopyroxene) veins. No significant correlation was observed between the lithology and the Fo content (90.21-82.81) of olivine, suggesting that these rocks could be derived from a cumulus process. The presence of the orthopyroxenite suggests that the inferred melt/s from which they stemmed was close (or even above) to silica saturation. Based on major and trace-element mineral/melt and mineral/mineral equilibrium modelling, these rocks were formed by progressive extraction of olivine from a high magnesium (Mg=72)high temperature (similar to 1300 degrees C) melt following a very short fractionation line. Thermobarometric results indicate the stationing of Harrow Peaks cumulates in the P field of 1.3 +/- 0.2 (dunites)0.5 +/- 0.2 (orthopyroxenite)GPa. These values well match the crust/mantle boundary (Moho) of the region. The combined geochemical and petrological data suggest that Harrow Peaks melts could be related to the initial stage of the Jurassic Ferrar magmatism, whose deep cumulates were subsequently affected by the Cenozoic alkaline metasomatism, widely detected in the northern Victoria Land lithosphere and responsible for the formation of the late amphibole/amphibole+clinopyroxene veins.
机译：一群超微的闭合象鼻型超卓越的Xenoliths来自哈罗峰（维多利亚州北部土地，南极洲）显示出纹理和地球化学特征，从这个地区的地幔Xenoliths和南极洲的其他地方观察到的任何东西。它们包括尖晶石的Lorzolites和Harzburgites，其特征在于，具有正交的围绕甲状腺素含量的主要围岩纹理，在Lherzbolites（18-26体积％）上相对于麦芽伯（13体积％），一个偏异素和三种复合氙岩。后者由大型单体（锥形或粘合剂）或氨髓鞘（Amphibole + Clinopogroxene）静脉的橄榄石优势组装（Olivine> 70％）伴体形成。在橄榄石的岩性和FO含量（90.21-82.81）之间没有观察到显着的相关性，表明这些岩石可以源自积云。矫形性的存在表明，它们源于它们的推断熔体是靠近（或甚至以上）到二氧化硅饱和度。基于主要和微量元素矿物/熔体和矿物/矿物平衡建模，通过在非常短的分馏之后通过从高镁（Mg = 72）高温（类似于1300℃）熔体来形成这些岩石通过从高镁（Mg = 72）的高温（类似于1300℃）熔体形成线。热磁化术结果表明，耙峰的驻留在1.3 +/- 0.2（Dunites）0.5 +/- 0.2（邻象）GPA的P场中累积。这些值很好地匹配该区域的地壳/地幔边界（Moho）。合并的地球化学和岩石学数据表明，耙峰熔化可能与侏罗纪法拉尔山岩的初始阶段有关，其巨大累积随后受新生代碱性弥扑主义的影响，在维多利亚北部岩石圈广泛检测到，负责形成后半吡啶/壮键+临床静脉静脉。

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