DOI: 10.1016/j.epsl.2021.117058
论文题名: Embryos of TTGs in Gore Mountain garnet megacrysts from water-fluxed melting of the lower crust
作者: Ferrero S. ; Wannhoff I. ; Laurent O. ; Yakymchuk C. ; Darling R. ; Wunder B. ; Borghini A. ; O'Brien P.J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 569 语种: 英语
中文关键词: crustal melting
; garnet
; megacrysts
; nanogranitoids
; trondhjemite
; TTG
英文关键词: Garnets
; Geodynamics
; Trace elements
; Crustal melting
; Experimental investigations
; Historical records
; Lower crust
; Megacrysts
; Nanogranitoids
; Phase equilibrium models
; Primary inclusions
; Tonalitic–trondhjemitic–granodioritic
; Trondhjemite
; Melting
; crustal evolution
; crustal thickening
; crystallography
; emplacement
; garnet
; geodynamics
; granodiorite
; lower crust
; megacryst
; melting
; tonalite
; trondhjemite
; Adirondack Mountains
; New York [United States]
; United States
英文摘要: The garnet megacrysts of Gore Mountain (Adirondacks, US) are world-renown crystals due to their size, up to 1 m in historical record, which makes them the largest known garnets on the planet. We show here that they are also host to the first primary inclusions of trondhjemitic melt found in natural mafic rocks. The petrological and experimental investigation of the inclusions, coupled with phase equilibrium modelling, shows that this melt is the result of H2O-fluxed partial melting at T>900 °C of a lower crustal gabbro. The compositional similarity between the trondhjemitic melt inclusions and tonalitic–trondhjemitic–granodioritic (TTGs) melts makes these inclusions a direct natural evidence that melting of mafic rocks generates TTG-like melts, and provides us with the possibility to clarify processes responsible for the formation of the early continental crust. These TTG embryos represent the trondhjemitic end-member of the melts whose emplacement at upper crustal levels, after being modified by mixing and crystallization-related processes, leads to the formation of the TTG terranes. Moreover, our study shows how the melt from H2O-fluxed melting of mafic lower crust has mismatched major and trace element signatures, previously interpreted as evidence of melting at very different pressures. This poses serious limitations to the established use of some chemical features to identify the geodynamic settings (e.g. subduction versus thickened crust) responsible for TTGs generation and the growth of early crust. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165466
Appears in Collections: 气候变化与战略
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作者单位: Universität Potsdam, Potsdam-Golm, 14476, Germany; Museum für Naturkunde (MfN), Berlin, 10115, Germany; Freie Universität Berlin, Berlin, 12249, Germany; ETH, Zurich, Department Erdwissenschaften, Institute for Mineralogy and Petrology, Zürich, 8092, Switzerland; CNRS, Observatoire Midi-Pyrénées, Géosciences Environnement, Toulouse, 31400, France; University of Waterloo, Waterloo, ON N2L 3G1, Canada; SUNY College at CortlandNY 13045, United States; GFZ, German Research Centre for Geosciences, Potsdam, 14473, Germany
Recommended Citation:
Ferrero S.,Wannhoff I.,Laurent O.,et al. Embryos of TTGs in Gore Mountain garnet megacrysts from water-fluxed melting of the lower crust[J]. Earth and Planetary Science Letters,2021-01-01,569