Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
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巴伯顿绿岩带（南非）Onverwacht 群下部变玄武岩和变科岩岩的岩石成因演化
DOI：
10.1016/j.chemgeo.2019.02.020
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
Kröner
中科院分区：
文献类型：
--
作者：
Schneider;Hoffmann;Münker;Patyniak;Sprung;Roerdink;Garbe Schönberg;Kröner
按照太古宙的标准，保存完好的地幔来源的变质玄武岩和变质岩层序构成了巴伯顿绿岩带(南非)下Onverwacht群的大部分。为了阐明3.55~3.45 Ga序列中镁铁质和超镁铁质岩石的成因，我们提供了一套全面的地球化学数据集，包括各种变火山岩的常量元素和微量元素以及Lusingle键Hf和Sm单键Nd同位素组成。这些玄武岩包括角闪岩相砂砾岩组和泰斯普鲁伊特组的变质玄武岩，以及下绿片岩相科马提组的变质玄武岩和变玄武岩。根据其不相容的微量元素模式，砂岩和特普鲁伊特组的玄武岩可细分为轻稀土元素(LREE)亏损组、轻稀土未亏损组和LREE富集组。εHf(T)和εNd(T)的正值分别为+3~+4和0~+2，加上Th和LaCN/YbCN的亏损，表明轻稀土亏损玄武岩来自亏损地幔源区。轻稀土样品的球粒εHf(T)和εNd(T)值与正的Th和LaCN/YbCN值相结合，表明这些样品的成因来自较老的花岗岩壳。科马提组科马提岩和玄武岩的微量元素模式相对于原始地幔总体上是平坦的，重稀土元素和Th略有亏损，总体正εHf(T)为+2.5 ± 3.5(2 S.D.)εND(T)为+0.5 ± 2.2(2 S.D.)。微量元素特征的一致性表明玄武岩和科马提岩具有共同的岩浆成因。这两个熔岩来自同一地幔热柱，即科马提岩是由含有残余石榴石的贫乏地幔源区高度熔融形成的，玄武岩是由地幔较浅地区的中等程度部分熔融形成的。基于现有的数据集，结合已发表的数据，我们提出了巴伯顿绿岩带最古老单元的地球动力学模型，描述了大陆裂谷导致的从水下大陆环境(对于Sandspruit组和Theespruit组)到海底高原环境(对于Komati组)的发展。
A well-preserved sequence, by Archean standards, of mantle-derived metabasalts and metakomatiites forms large parts of the lower Onverwacht Group of the Barberton Greenstone Belt (South Africa). To elucidate the origin of mafic and ultramafic rocks from this 3.55 to 3.45 Ga sequence, we present a comprehensive geochemical dataset including major and trace elements as well as Lusingle bondHf and Smsingle bondNd isotope compositions for a variety of metavolcanic rocks. These include metabasalts of the amphibolite-facies Sandspruit and Theespruit Formations as well as metabasalts and metakomatiites of the lower greenschist-facies Komati Formation.Based on their incompatible trace element patterns, the basalts of the Sandspruit and Theespruit Formations can be subdivided into a light rare earth element (LREE) depleted group, a LREE-undepleted group, and a LREE-enriched group. Positive εHf(t)and εNd(t)values of ca. +3 to +4 and 0 to +2, respectively, together with depletions in Th and LaCN/YbCNindicate derivation of the LREE-depleted basalts from a depleted mantle source. However, chondritic εHf(t)and εNd(t)values combined with positive Th and LaCN/YbCNof the LREE-enriched samples indicate a contribution from older granitoid crust in the petrogenesis of these samples.Trace element patterns of komatiites and basalts of the Komati Formation are generally flat relative to primitive mantle with slight depletions in heavy rare earth elements and Th and overall positive εHf(t)of +2.5 ± 3.5 (2 s.d.) and εNd(t)of +0.5 ± 2.2 (2 s.d.). The coherence in trace element characteristics suggests a common magmatic origin for basalts and komatiites. This study reveals that the two lavas were derived from the same mantle plume, i.e. komatiites were formed by high degrees of melting of a depleted mantle source containing residual garnet and the basalts were formed by moderate degrees of partial melting in shallower regions of the mantle.Based on the current dataset, combined with published data, we propose a geodynamic model for the oldest units of the Barberton Greenstone Belt that describes the development from a submerged continental setting (for the Sandspruit and Theespruit Formations) to a submarine plateau setting (for the Komati Formation) as a consequence of continental rifting.
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评论：“早期太古宙大陆地壳的生长和再循环：来自澳大利亚皮尔巴拉克拉通的 Coonterunah 和 Warrawoona 群的地球化学证据”，Green, M.G. 等人 (Tectonophysicals 322, 69-88)
DOI：
--
发表时间：
2002
期刊：
影响因子：
--
作者：
R. Bolhar;J. Woodhead;J. Hergt
通讯作者：
J. Hergt
南非卡普瓦尔克拉通东部太古代火成岩中丰富且现代的 142 Nd 特征共存
影响因子：
5.3
作者：
Schneider;Hoffmann;Münker;Kröner
通讯作者：
Kröner
DOI：
10.1144/sp449.2
发表时间：
2016-09
期刊：
Special Publications
影响因子：
--
作者：
K. Szilas;J. Tusch;J. Hoffmann;A. Garde;C. Münker
通讯作者：
K. Szilas;J. Tusch;J. Hoffmann;A. Garde;C. Münker
DOI：
--
发表时间：
1977
期刊：
影响因子：
--
作者：
N. Arndt
通讯作者：
N. Arndt
南非巴伯顿花岗岩-绿岩地形最古老的部分：3.5 至 3.7 Ga 之间地壳形成的证据
影响因子：
3.8
作者：
A. Kröner;E. Hegner;J. Wendt;G. Byerly
通讯作者：
G. Byerly