DOI: 10.1016/j.epsl.2020.116170
论文题名: Primary CO2-bearing fluid inclusions in granulitic garnet usually do not survive
作者: Carvalho B.B. ; Bartoli O. ; Cesare B. ; Tacchetto T. ; Gianola O. ; Ferri F. ; Aradi L.E. ; Szabó C.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 536 语种: 英语
中文关键词: carbonic metamorphism
; COH fluids
; fluid regime
; granulites
; post-entrapment reactions
; primary fluid inclusions
英文关键词: Calcite
; Carbon dioxide
; Corundum
; Garnets
; Kaolinite
; Magnesite
; Mica
; Mineralogy
; carbonic metamorphism
; Fluid inclusion
; Fluid regime
; granulites
; post-entrapment reactions
; Temperature
; carbon dioxide
; fluid inclusion
; garnet
; granulite
; high temperature
; host rock
; metamorphism
; retrograde metamorphism
英文摘要: CO2-bearing fluid inclusions (FI) from granulites have been the main advocate for an active role of fluids during high-temperature metamorphism, yet the fluid regime of the deep crust and the role of fluids remain largely debated topics. In this dispute, one of the most controversial issues is the timing of FI entrapment relative to peak metamorphic conditions. Here we investigate three world-renowned high- to ultra-high temperature metamorphic terranes to evaluate the fate of primary CO2 and COH fluid inclusions certainly trapped during the prograde path. Fluid inclusions coexist along with nanogranitoids in peritectic garnet. Combination of cutting-edge techniques indicates that the FI are composed of fluid and aggregates of solid phases. The latter usually comprises siderite, ferroan magnesite, pyrophyllite, calcite, corundum, quartz, and in some cases kaolinite, dolomite, biotite and muscovite. In the fluid phase, low-density CO2 is the most common component and no free H2O has been detected. Methane and N2 may be also present. The high proportion of solids in the FI with carbonates and OH-bearing phases cannot have precipitated as daughter phases directly from a simple COH-fluid as daughter phases. These minerals require additional cations (e.g. Fe, Mg, Ca, Al, Si) which may be dissolved in very small amounts in crustal fluids and yet are very abundant in the host. The solids, therefore, imply that the initial composition of high-density carbonic inclusions must have been changed by the interaction with the host garnet during cooling. Thermodynamic modelling of such fluid-garnet interaction demonstrates that the assemblages found in FI are metastable and that, whatever retrograde path is followed by the host rock, primary C-bearing FI must change their nature to a multiphase assemblage of stepdaughter minerals as a natural consequence of cooling. It follows that supposed primary unmodified FI in garnet previously reported in the literature are, in most cases, secondary, retrograde features whose low temperature of entrapment inhibited fluid-host interaction. Our finding undermines the main pillar of the theory of carbonic fluid-assisted metamorphism (the presence of superdense CO2 inclusions in granulites), but at the same time it offers a novel perspective to identify prograde COH fluids in the deep hot crust. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164906
Appears in Collections: 气候变化与战略
There are no files associated with this item.
作者单位: Dipartimento di Geoscienze, Università degli Studi di Padova, Via G. Gradenigo, 6, Padova, 35131, Italy; School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; Lithosphere Fluid Research Lab, Institute of Geography and Earth Sciences, Eötvös Lorand University Budapest (ELTE), Pázmány P. stny. 1/C, Budapest, H-1117, Hungary
Recommended Citation:
Carvalho B.B.,Bartoli O.,Cesare B.,et al. Primary CO2-bearing fluid inclusions in granulitic garnet usually do not survive[J]. Earth and Planetary Science Letters,2020-01-01,536