Transition from eclogite to amphibolite-facies metamorphism in the Austroalpine Ulten Zone

Hauzenberger, Christoph; Höller, W.; Hoinkes, G.

doi:10.1007/bf01172092

Cited by 24 publications

(10 citation statements)

References 19 publications

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“…Based on Fe-Mg zoning in garnet and petrological considerations, i.e. lack of Na-pyroxene, rather Si-poor phengite and retrograde biotite, Godard et al (1996) and Hauzenberger et al (1996) considered the UZ gneiss and associated migmatites as entirely retrogressed rocks. In this study, however, petrography and phase-diagram modelling indicate that minerals such as Fe-rich garnet, epidote, chlorite, staurolite and amphibole included in kyanite are related to prograde stages of the metamorphic evolution.…”

Section: Discussionmentioning

confidence: 99%

“…In sample NONS17, large porphyroblasts of kyanite and garnet are set in a foliated matrix defined by quartz and plagioclase (Ô K-feldspar) layers alternating with biotite, garnet, kyanite, rutile (Ô white mica) melanocratic levels. Kyanite occurs as two different types (previously recognized by Hauzenberger et al, 1996): (1) coarsegrained crystals (up to 6 mm long in the selected thin section) with subhedral to anhedral shape and numerous mineral inclusions; and (2) smaller crystals (41 mm) with rare inclusions. The cores of a few kyanite porphyroblasts contain inclusions of minerals such as garnet, white mica, biotite, rutile, staurolite, epidote, amphibole and chlorite ( Fig.…”

Section: Geological Outline and Sample Petrographymentioning

confidence: 99%

“…1) represents a remnant of Variscan basement that was subject to metamorphism at high P and T. The UZ mainly comprises strongly foliated garnet-kyanite g n e i s s e s a n d l e u c o c r a t i c m i g m a t i t e s . Amphibolite-facies mafic rocks, which rarely preserve eclogitic assemblages (Godard et al, 1996;Hauzenberger et al, 1996) and spinel Ô garnet-bearing peridotite lenses (Obata and Morten, 1987;Godard et al, 1996) are locally present. Field, petrological and radiometric data permit correlation of the UZ with contemporaneous (~340 Ma) basement units (e.g.…”

Section: Geological Outline and Sample Petrographymentioning

confidence: 99%

“…In this study we provide petrographical and thermobarometric evidence that kyanite can indeed preserve records of early metamorphic stages. This kyanite appears in the strongly-foliated garnet-kyanite gneisses from the Variscan Ulten Zone (UZ) for which the early metamorphic path is essential to discriminate between an early high-pressure event (515 kbar, Hauzenberger et al, 1996) and an ultrahigh pressure event recently suggested by Tumiati et al (2003).…”

Section: Introductionmentioning

confidence: 99%

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An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite

Braga¹,

Massonne²,

Morten³

2007

Mineral. mag.

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The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution of these relics to the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11–12 kbar and 600–650°C followed by decompressional heating to 720°C and 9–10 kbar and final cooling at 7 kbar, 550–600°C. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330–340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Outline and Sample Petrographymentioning

confidence: 99%

Section: Geological Outline and Sample Petrographymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite

Braga¹,

Massonne²,

Morten³

2007

Mineral. mag.

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show abstract

“…In contrast, problems arise with garnet from mafic metaigneous rocks, where especially eclogite and amphibolite facies (A1, B1, respectively) show considerable overlap. The latter has long been known (e.g., Mange and Morton, 2007) and is caused by several reasons, among them (i) similar protolith composition (e.g., basalt) limiting the potential contrast in garnet composition and (ii) problems in clearly distinguishing metamorphic grade of mafic metaigneous rocks at the amphibolite-eclogite facies transition, e.g., rocks appearing as garnet-bearing amphibolite may have suffered eclogite-facies metamorphism or vice versa, the exception being garnet grains with clear chemical zonation (e.g., Hauzenberger et al, 1996;Endo et al, 2013; see Section 5.3). Granulite-facies mafic (C1) and felsic (C2) metaigneous rocks appear rather similar with respect to garnet composition.…”

Section: Discrimination Of Metamorphic Garnetsmentioning

confidence: 99%

A multivariate discrimination scheme of detrital garnet chemistry for use in sedimentary provenance analysis

Tolosana‐Delgado

Eynatten

Krippner

et al. 2018

Sedimentary Geology

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Garnet chemistry provides a well-established tool in the discrimination and interpretation of sediment provenance. Current discrimination approaches, however, (i) suffer from using less variables than available, (ii) subjective determination of discrimination fields with strict boundaries suggesting clear separations where in fact probabilities are converging, and (iii) significant overlap of compositional fields of garnet from different host-rock groups. The new multivariate discrimination scheme is based on a large database, a hierarchical discrimination approach involving three steps, linear discriminant analysis at each step, and the five major host-rock groups to be discriminated: eclogite-(A), amphibolite-(B) and granulite-(C) facies metamorphic rocks as well as ultramafic (D) and igneous rocks (E). The successful application of statistical discrimination approaches requires consideration of the a priori knowledge of the respective geologic setting. This is accounted for by the use of prior probabilities. Three sets of prior probabilities (priors) are introduced and their advantages and disadvantages are discussed. The user is free to choose among these priors, which can be further modified according to the specific geologic problem and the level of a priori knowledge. The discrimination results are provided as integrated probabilities of belonging to the five major host-rock groups. For performing calculations and results a supplementary Excel® spreadsheet is provided. The discrimination scheme has been tested for a large variety of examples of crystalline rocks covering all of the five major groups and several subgroups from various geologic settings. In most cases, garnets are assigned correctly to the respective group. Exceptions typically reflect the peculiarities of the regional geologic situation. Evaluation of detrital garnets from modern and ancient sedimentary settings of the Western Gneiss Region (Norway), Eastern Alps (Austria) and Albertine Rift (Uganda) demonstrates the power to reflect the respective geologic situations and corroborates previous results. As most garnet is derived from metamorphic rocks and many provenance studies aim at reconstructing the tectonic and geodynamic evolution in the source area, the approach and the examples emphasize discrimination of metamorphic facies (i.e., temperature-pressure conditions) rather than protolith composition.

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Paleozoic Evolution and Variscan Inheritance in the Alps

JACOB,

GUILLOT,

THIÉBLEMONT

et al. 2024

Geodynamics of the Alps 2

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Transition from eclogite to amphibolite-facies metamorphism in the Austroalpine Ulten Zone

Cited by 24 publications

References 19 publications

An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite

An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite

A multivariate discrimination scheme of detrital garnet chemistry for use in sedimentary provenance analysis

Paleozoic Evolution and Variscan Inheritance in the Alps

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