An insight into the first stages of the Ferrar magmatism: ultramafic cumulates from Harrow Peaks, northern Victoria Land, Antarctica
An insight into the first stages of the Ferrar magmatism: ultramafic cumulates from Harrow Peaks, northern Victoria Land, Antarctica
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深入了解费拉尔岩浆作用的第一阶段：来自南极洲维多利亚地北部哈罗峰的超镁铁质堆积物
DOI：
10.1007/s00410-019-1579-1
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发表时间：
2019
影响因子：
3.5
通讯作者：
M. Coltorti
中科院分区：
文献类型：
--
作者：
Beatrice Pelorosso;C. Bonadiman;T. Ntaflos;M. Grégoire;S. Gentili;A. Zanetti;M. Coltorti
哈罗峰（南极洲北方维多利亚地）新生代浅成岩石中的一组超镁铁质捕虏体，其结构和地球化学特征与该地区和南极洲其他地区的地幔捕虏体中所观察到的特征相去甚远。它们由含尖晶石的二辉橄榄岩和方辉橄榄岩组成，其特征在于具有明显较高的二辉橄榄岩（18-26体积%）相对于方辉橄榄岩（13体积%），一个斜方辉石岩和三个复合捕虏体的优势等粒结构。后者由以橄榄石为主的组合（橄榄石> 70%）被大型单矿物（角闪石或单斜辉石）或双矿物（角闪石+单斜辉石）脉横切而成。橄榄石的Fo含量（90.21-82.81）与岩石的岩性没有明显的相关性，表明这些岩石可能是由积云作用形成的。正辉石岩的存在表明，推断熔体/S从他们源于接近（甚至以上）的二氧化硅饱和。根据主要和微量元素矿物/熔体和矿物/矿物平衡模型，这些岩石是通过从高镁（Mg = 72）高温（~ 1300 °C）熔体中逐步提取橄榄石，然后经过非常短的分馏线形成的。温压测量结果表明，哈罗峰的堆积位于1.3 ± 0.2（纯橄榄岩）-0.5 ± 0.2（正辉石岩）GPa的P场中。这些值与该地区的地壳/地幔边界（莫霍面）非常吻合。结合地球化学和岩石学数据表明，哈罗峰熔体可能与侏罗纪Ferrar岩浆活动的初始阶段，其深堆随后受到新生代碱性交代作用的影响，广泛发现于北方维多利亚陆岩石圈，并负责形成晚角闪石/角闪石+单斜辉石脉。
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 (~ 1300 °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.
DOI：
10.7185/geochemlet.1728
发表时间：
2017-07
期刊：
--
影响因子：
--
作者：
S. Lambart
通讯作者：
S. Lambart