Equilibrium-disequilibrium relations in the Monte Rosa Granite, Western Alps: Petrological, Rb-Sr and stable isotope data

Frey, Martin; Hunziker, Johannes C.; O’Neil, James R.; Schwander, H.

doi:10.1007/bf00372224

Cited by 110 publications

(46 citation statements)

References 18 publications

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“…Large fragments of low-density continental crust were deeply subducted and then exhumed together with ophiolitic remnants of the consumed oceanic lithosphere (Ernst, 1971;Dal Piaz et al, 1972). Petrologic estimates show that these units were variously buried to depths >30-40 km (in some cases >100 km), as clearly documented by blueschistand eclogite-facies assemblages (Frey et al, 1974(Frey et al, , 1976Compagnoni et al, 1977;Spalla et al, 1996;Oberhansli et al, 2004) that are locally coesite bearing (Dora Maira nappe; Chopin, 1984; Zermatt-Saas ophiolite at Lago di Cignana; Reinecke, 1991).…”

Section: Introductionmentioning

confidence: 94%

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

Gasco

Gattiglio

Borghi

2013

Journal of Geodynamics

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Section: Introductionmentioning

confidence: 94%

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

Gasco

Gattiglio

Borghi

2013

Journal of Geodynamics

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“…Assuming isotopic equilibration under greenschist-facies conditions among minerals in any given rock sample, the following order of minerals with decreasing #*O-values has to be expected, according to the theoretical calibrations of Zheng (1993aZheng ( , 1993b: quartz, calcite, albite, phengite/anorthite/ muscovite, chlorite, pyroxene, amphibole, oxides; this is slightly different from the order previously given by Faure (1986, chap. 25) and Frey et al (1976) particularly for chlorite -because their order was based on the observation from natural assemblages 92 C. Henry et al /Chemical Geology 127 (1996) which may have experienced isotopic re-equilibration during cooling. In most of the studied samples, this general order is respected, suggesting that the analyzed minerals have indeed approximated isotopic equilibrium with regard to oxygen.…”

Section: Oxygen Partitioning Between Minerals: Testfor Isotopic Equilmentioning

confidence: 99%

Evolution of synmetamorphic veins and their wallrocks through a Western Alps transect: no evidence for large-scale fluid flow. Stable isotope, major- and trace-element systematics

1996

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Quartz-rich synfolial veins and wallrocks from different areas of a Western Alps cross-section are examined in an attempt to constrain the scale and mechanisms of fluid flow through metamorphic terrains. Different portions of this cross-section underwent distinct P-T evolutions as reflected by the mineralogy of veins: (a) in the greenschist external Dauphinois domain, veins are characterized by quartz and calcite, together with an aluminosilicate (pyrophyllite), Na-K-bearing phyllosilicates and a FeMg-bearing silicate (chlorite) ; (b) in narrow domains of the Brianconnais and Piemontais zones, with a non-eclogitic HP-LT evolution followed by rapid cooling, veins are characterized by quartz, calcite, Ca-and Fe-Mg-bearing silicates (lawsonite and Fe-Mg-carpholite, respectively) ; and (c) in the major part of the Brianconnais andpiemontais zones, where low-grade blueschistfacies metamorphism is followed by a greenschist-facies evolution, veins are characterized by the replacement of earlier lawsonite and carpholite by Na-and K-bearing micas. In order to constrain the provenance of fluids involved in vein formation, we determined stable isotope (C, 0, H), and major-and trace-element compositions in minerals and whole rocks for a large set of veins and wallrocks. These rocks are compared with some non-metamorphic shales from the northern Paris Basin, considered as protoliths of the Alpine schists. Stable isotope compositions of calcites are regionally distinct: 6r80 = + 28%0 (SMOW) in the northern Paris Basin, + 26%0 in the Brianconnais zone, + 22%0 in the Piemontais zone and + 18%0 in the Dauphinois zone. Within each studied region, calcite G'*O-values are quite homogeneous regardless of rock type (vein or wallrock). This feature is explained as an isotopic "homogenization" with the most abundant lithology in each zone ("rock-buffered system") -where the overall ratio of calcite (of marine origin) to detrital silicate minerals determines the final isotopic composition of the whole rock (w.r.) after equilibration during Alpine metamorphism. G'*O/GD-values of analysed hydrated minerals and whole rocks ( Si80 = + 15 to -t-25%0 and 6D = -60%0 SMOW)' lie within the field of Alpine cover rocks and of fluids in equilibrium with these rocks: interaction with an external '*O-or D-depleted fluid, such as hydrothermal waters, meteoric water or "basement fluid", can be ruled out. Major-and trace-element systematics indicate an enrichment in Si, Ca, P, Sr, Y, Ta and locally Eu in the veins with respect to the wallrock, related to massive crystallization of quartz and carbonates, together with phosphate and oxide. Potential fluid sources, chemical composition of the fluid phase and the mechanisms of fluid flow during vein formation are discussed. Fluid flow takes place within tectonic units, at both hectometric and decimetric scale. Fluid may also have migrated along and across the major tectonic contacts but this process is poorly documented.

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“…Thus, the 87 Sr and 18 0 enrichments in the crust are a result of two completely different mechanisms, and the combination of the two effects clearly demonstrates a major contamination and involvement with the crust. Furthermore, Frey et al (1976) concluded from Rb-Sr and 18 0/ 16 0 measurements that the radiogenic isotopes in biotite appear to have been mobilized without breaking Al-0 or Si-0 bonds, that is without recrystallization. In another case, Taylor and Magaritz (1976) showed that there is an excellent agreement between areas of reset K-Ar ages and areas of low deuterium content.…”

Section: General Remarks On Sample Handlingmentioning

confidence: 99%

Stable Isotope Geochemistry

Hoefs¹

1980

Minerals and Rocks

203

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Equilibrium-disequilibrium relations in the Monte Rosa Granite, Western Alps: Petrological, Rb-Sr and stable isotope data

Cited by 110 publications

References 18 publications

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

Evolution of synmetamorphic veins and their wallrocks through a Western Alps transect: no evidence for large-scale fluid flow. Stable isotope, major- and trace-element systematics

Stable Isotope Geochemistry

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