Constraining the process of Eoarchean TTG formation in the Itsaq Gneiss Complex, southern West Greenland
Constraining the process of Eoarchean TTG formation in the Itsaq Gneiss Complex, southern West Greenland
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DOI：
10.1016/j.epsl.2013.11.050
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发表时间：
2014-02-15
影响因子：
5.3
通讯作者：
Rosing, Minik T.
中科院分区：
文献类型：
--
作者：
Hoffmann, J. Elis;Nagel, Thorsten J.;Rosing, Minik T.
我们提出了新的主要和微量元素，高精度的高场强元素，铪和钕同位素数据保存完好的始新世TTG在伊萨克片麻岩复杂（IGC）的西格陵兰南部。这些数据与部分熔融和分离结晶的热力学模型预测相结合，以获得新的见解在太古代大陆地壳的形成。我们的研究结果表明，所观察到的始太古代TTG的成分范围可以解释为两个过程的组合：（1）5-25%的部分熔融角闪岩在加厚的镁铁质地壳和（2）随后的分离结晶过程。格陵兰西南部的始新世TTG套件可能是通过混合熔融批次，最初形成于不同的源深度之间的10和14千巴，并在中地壳的水平作为岩体积水。一些TTG的微量元素组合物指向随后的分离结晶过程，涉及斜长石，单斜辉石，角闪石和石榴石。我们的模型是一致的，最近的研究提出，始新世Itsaq片麻岩复杂TTG从IGC形成的重新工作的镁铁质原地壳，稳定的增积的幼年地壳在始新世。该模型也与该地区的实地观测结果吻合良好。(C)2013 Elsevier B. V.保留所有权利。
We present new major and trace element, high-precision high-field-strength-element, hafnium and neodymium isotope data for well preserved Eoarchean TTGs within the Itsaq Gneiss Complex (IGC) of southern West Greenland. These data are combined with thermodynamic model predictions of partial melting and fractional crystallization to gain new insights into continental crust formation in the Archean. Our results show that the observed compositional range of Eoarchean TTGs can be explained by a combination two processes: (1) 5-25% partial melting of amphibolite within thickened mafic crust and (2) subsequent fractional crystallization processes. The Eoarchean TTG suite of SW Greenland probably formed through mixing of melt batches that originally formed at different source depths between 10 and 14 kbar and ponded as plutons at mid-crustal levels. The trace element compositions of some TTGs point to subsequent fractional crystallization processes involving plagioclase, clinopyroxene, amphibole and garnet. Our model is consistent with recent studies proposing that the Eoarchean Itsaq Gneiss Complex TTGs from the IGC formed by re-working of mafic protocrust that stabilized as accreted juvenile crustal terranes in the Eoarchean. The model is also in good agreement with field observations from the area. (C) 2013 Elsevier B.V. All rights reserved.