Metapelite from the high‐ to ultrahigh‐pressure terrane of the Eastern Alps (Pohorje Mountains, Slovenia)—New pressure, temperature and time constraints on a polymetamorphic rock

Li, Botao; Massonne, Hans‐Joachim; Koller, Friedrich; Zhang, Junfeng

doi:10.1111/jmg.12581

Cited by 10 publications

(53 citation statements)

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“…In addition, it is also debated whether all paragneisses from the southeastern Pohorje Mts experienced UHP. Thus, one of our aims is to clarify this situation by studying metasedimentary rocks from the southwestern Pohorje Mts in addition to the micaschist reported by Li et al (2021).…”

Section: Introductionmentioning

confidence: 99%

“…In order to address the above problems, we continue our previous work on metasediments (subsequently called micaschists) from the southeastern Pohorje area (Li et al, 2021). During our study, we not only confirmed Eo‐Alpine HP conditions (hereafter termed Stage I) for micaschist obtained by our previous work (Li et al, 2021) but also we detected for the first‐time evidence for a reheating event (hereafter termed Stage III) caused by the Miocene Pohorje pluton in micaschist. Furthermore, we discuss the previously recognized imprint of an Eocene metamorphic event (hereafter termed Stage II) (Li et al, 2021), which we relate to intracontinental subduction.…”

Section: Introductionmentioning

confidence: 99%

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A wealth of P–T–t information from metasediments in the HP–UHP terrane of the Pohorje Mountains, Slovenia, elucidates the evolution of the Eastern Alps

Massonne

Yuan

2023

Journal Metamorphic Geology

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Contrasting views exist in the literature in regard of the evolution of metamorphic rocks in the southeastern Pohorje Mountains (Mts), located in the southeastern Eastern Alps. Major debated points are whether micaschists have experienced ultrahigh‐pressure metamorphism in the Late Cretaceous (Eo‐Alpine) and whether they were continuously exhumed or experienced a multiple subduction‐exhumation process from that time on. Therefore, we studied micaschist sample 18Slo39 with two generations of garnet and phengitic muscovite from this area. Our detailed study of this rock included petrographic observations, chemical analyses of minerals with the electron microprobe, pseudosection modeling, conventional geothermometry, and monazite in‐situ U‐Th‐Pb dating using laser‐ablation ICP mass spectrometry. The following results were obtained: The studied micaschist was subject to a peak‐pressure of 1.31±0.14 GPa at 603±26 °C in Eo‐Alpine times: 90.62±2.78 (2σ) Ma (Stage I). Contact metamorphism at pressure‐temperature conditions of 0.66±0.10 GPa and 577±23 °C was induced by the intrusion of the Pohorje pluton (Stage III). We determined an early Miocene age of 18.33±0.43 (2σ) Ma for this intrusion. Based on this study and the previously reported data for a micaschist (16Slo12) taken in the vicinity of sa 18Slo39, a geodynamic model is proposed for the region of the Pohorje Mts considering Eo‐Alpine subduction of oceanic crust and European continental crust, of which the micaschist was part of. Another high‐pressure event in the Eocene (Stage II) was the result of intracontinental subduction due to transpression by the Periadriatic fault system which separates the Eastern Alps from the Southern Alps. This type of subduction gave rise to magma generation and ascent to form the Pohorje pluton, which caused contact metamorphism in its vicinity.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A wealth of P–T–t information from metasediments in the HP–UHP terrane of the Pohorje Mountains, Slovenia, elucidates the evolution of the Eastern Alps

Massonne

Yuan

2023

Journal Metamorphic Geology

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“…This implication is strengthened by Spear (2017) who argued for kinetic factors (energetic barriers) being responsible for a significant overstepping of the P-T limit of garnet. Examples for this phenomenon in higher grade metasediments leading to nearly chemically homogeneous porphyroblastic garnet were recently presented by Li et al (2021Li et al ( , 2020. Indeed, the common garnet core in gneiss SWE3-2c is relatively chemically homogeneous.…”

Section: Discussion 61 Pressure-temperature Evolutionmentioning

confidence: 92%

Pressure-Temperature Evolution of a Mylonitic Gneiss from the Lower Seve Nappe in the Handöl Area, Central Sweden

Massonne

Yuan

2021

J. Earth Sci.

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Ultrahigh-pressure metamorphism has recently been reported from various crustal rocks in the Seve Nappe Complex (SNC) in which microdiamonds were found. However, in gneiss from the Lower Seve Nappe (LSN), neither any direct petrographic indication for UHP was reported nor the metamorphic evolution was well constrained. We studied a mylonitic gneiss from the Handöl area of the LSN and applied phase-diagram modeling and Ti-in-biotite thermometry. Based on the compositions of garnet and biotite and observed mineral assemblages, a path was reconstructed passing through about 8 kbar and 730 °C at prograde metamorphism. Peak-pressure and initial retrograde stages occurred at 9.0-10.2 kbar at 745-775 °C, and 7-9 kbar at <750 °C, respectively. No ultrahigh-pressure evidence was recognized compatible with medium-pressure metamorphism deduced in earlier studies of gneiss from the SNC. As higher peak pressures were reported recently for metamorphic rocks of the LSN, a possible interpretation is that slices or erased blocks were subducted, metamorphosed at different depths, and exhumed in a subduction channel. However, the dominant gneiss of the SNC experienced only a medium-pressure metamorphism in the upper part of the downgoing Baltica Plate. Rocks from different depth levels were brought together in an exhumation channel located between Baltica and the overlying plate.

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“…In the Prijakt Subgroup of the BSTW, with a similar P-T path, this age classification was not free of doubt, as a distinct population of Carboniferous monazite exists there. However, a Permian metamorphism at an intermediate P-T regime has been reported from regions adjacent to the Saualpe [82][83][84]. It should have preceded a Permo-Triassic low pressure stage with the intrusion of pegmatites.…”

Section: Discussionmentioning

confidence: 99%

Petrochronology of Monazite-Bearing Garnet Micaschists as a Tool to Decipher the Metamorphic Evolution of the Alpine Basement

Schulz

2021

Minerals

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Garnet-bearing metapelites in the Helvetic and Austroalpine pre-Mesozoic polymetamorphic basement are characterised by pressure-temperature path segments reconstructed by microstructurally controlled geothermobarometry, and the Th-U-Pb monazite age distribution pattern revealed by the electron probe microanalyser (EPMA). In the Helvetic Aiguilles Rouges Massif and the Austroalpine Oetztal-Stubai basement to the NW an Ordovician-to-Silurian high temperature event preceded a pressure-dominated Carboniferous metamorphism. In the Austroalpine basement units to the south of the Tauern Window, the maximal pressures of the Carboniferous amphibolite-facies metamorphism range from 12 to 6 kbar. The decompressional P-T path segments signal a transition to low pressure conditions. A subsequent high pressure overprint is restricted to the Prijakt Subgroup unit in the Schobergruppe and documented by Cretaceous monazite crystallisation at 88 ± 6 Ma. In the Austroalpine Saualpe basement to the SE, a distinct early Permian metamorphism which started at low pressures of ~4 kbar/500 °C and reached maximal 6 kbar/600–650 °C predated the intrusion of Permian pegmatites. Permian monazite crystallised in line with the intrusion of pegmatites. Corona microstructures around the Permian monazites indicate retrogression previous to a Cretaceous high pressure metamorphism. That way, pressure-temperature-time paths resolve the spatial and temporal evolution in the polymetamorphic Alpine basement prior to the Tertiary collision.

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Metapelite from the high‐ to ultrahigh‐pressure terrane of the Eastern Alps (Pohorje Mountains, Slovenia)—New pressure, temperature and time constraints on a polymetamorphic rock

Abstract: This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Cited by 10 publications

References 118 publications

A wealth of P–T–t information from metasediments in the HP–UHP terrane of the Pohorje Mountains, Slovenia, elucidates the evolution of the Eastern Alps

A wealth of P–T–t information from metasediments in the HP–UHP terrane of the Pohorje Mountains, Slovenia, elucidates the evolution of the Eastern Alps

Pressure-Temperature Evolution of a Mylonitic Gneiss from the Lower Seve Nappe in the Handöl Area, Central Sweden

Petrochronology of Monazite-Bearing Garnet Micaschists as a Tool to Decipher the Metamorphic Evolution of the Alpine Basement

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