A P-T-t Path for an (ultra?-) High-Pressure Ultramafic/Mafic Rock-Association and Its Felsic Country-Rocks Based on SHRIMP-Dating of Magmatic And Metamorphic Zircon Domains. Example: Alpe Arami (Central Swiss Alps)

2013 ◽  
pp. 307-329 ◽  
Author(s):  
Dieter Gebauer
Keyword(s):  
High Pressure ◽  
Mafic Rock ◽  
Swiss Alps ◽  
Metamorphic Zircon ◽  
Shrimp Dating ◽  
Ultra High Pressure ◽  
T Path ◽  
Rock Association

Timing of HP/HT alpine metamorphism: new data from Cima di Gagnone (Central Alps)

2020 ◽  
Author(s):  
Stefania Corvò ◽  
Matteo Maino ◽  
Antonio Langone ◽  
Filippo Luca Schenker ◽  
Silvio Seno ◽  
...  
Keyword(s):  
High Pressure ◽  
Structural Control ◽  
Mafic Rock ◽  
Planetary Science ◽  
Swiss Alps ◽  
Central Alps ◽  
Sample Collection ◽  
Shrimp Dating ◽  
Mafic Rocks ◽  
Ultra High Pressure

<p>Keywords: HP-HT metamorphism, microstructures, U-Pb-Th dating, P-T-t-d path.</p><p>The occurrence of (ultra)high pressure and high temperature mineralogical assemblages developed during the Alpine phases makes the Cima di Gagnone area (Cima Lunga unit) one of the most studied area in the Central Alps. It consists of continental basement rocks (orthogneisses, paragneisses and metapelites) enveloping (ultra-) mafic bodies of oceanic crust (eclogite, amphibolites and peridotites) which record pressure and temperature up to 3 GPa and 800 °C, respectively (e.g. Nimis and Trommsdorff, 2001; Scambelluri et al., 2015). This high-grade metamorphism is constrained between 40 and 35 Ma by U-Pb dating from the ultra-mafic and mafic rocks (e.g. Gebauer, 1999). The metamorphism peak of the surrounding gneiss complex is instead constrained at considerably lower conditions (up to 0.8 GPa and 660 °C; Grond et al., 1995). The temperature peak in the felsic rocks is dated at ca. 32 Ma (Gebauer, 1996), coeval with the Bergell emplacement. Several models have been proposed to explain the coupling between ultrahigh- and middle- pressure rock pairs resulting in a large uncertainty in the adopted subduction-exhumation models.</p><p>We performed new petrological, micro-structural and geochronological data from the gneissic rocks, with the aim to investigate how the pressure and temperature conditions experienced by the felsic and mafic rocks are truly different. We explored the spatial variation of the metamorphic record through sample collection the structural control of the inclusion-matrix couples. Petrological and microstructural (SEM-EBSD) analyses are performed to define the deformation and metamorphic patterns of samples collected. Our results indicate that some portions of the gneissic matrix preserve relicts of higher pressure and temperature than previously suggested. The high-T conditions are temporally constrained by U-(Th)-Pb dating of monazite and zircon, which provides peak age estimations similar to the mafic rocks. The new data shed a light on heterogeneous metamorphism recorded by different rocks, providing new elements for the discussion on the most fitting geodynamic models.</p><p>REFERENCES</p><p>- Gebauer, 1996. A P-T-t Path for an (Ultra?-) High-Pressure Ultramafic/Mafic Rock-Association and its Felsic Country-Rocks Based on SHRIMP-Dating of Magmatic and Metamorphic Zircon Domains. Example: Alpe Arami (Central Swiss Alps). Earth Processes Reading the Isotopic Code, Geophysical Monograph 95, 307-329, AGU.</p><p>- Gebauer, 1999. Alpine geochronology of the Central Alps and Western Alps: new constraints for a complex geodynamic evolution. Schweiz. Mineral. Petrogr. Mitt., 79, 191-208.</p><p>- Grond, R., Wahl, F. and Pfiffner, M., 1995. Mehrphasige alpine Deformation und Metamorpshe in der nordlichen Cima Lunga-Einheit, Zentralalpen (Scweiz). Schweiz. Mineral. Petrogr. Mitt., 75, 371-386.</p><p>- Nimis, P. & Trommsdorff, V., 2001. Revised thermobarometry of Alpe Arami and other garnet peridotites from the central Alps. J. of Petrology, 42, 103-115.</p><p>- Scambelluri, M., Pettke, T., & Cannaò, E. (2015). Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps). Earth and Planetary Science Letters, 429, 45-59.</p>

scholarly journals Trans-lithospheric diapirism explains the presence of ultra-high pressure rocks in the European Variscides

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Petra Maierová ◽  
Karel Schulmann ◽  
Pavla Štípská ◽  
Taras Gerya ◽  
Ondrej Lexa
Keyword(s):  
High Pressure ◽  
Numerical Models ◽  
Classical Concept ◽  
Plate Interface ◽  
Ultra High Pressure ◽  
Common Process ◽  
Mountain Belts ◽  
Collisional Orogens ◽  
Rock Association ◽  
European Variscides

AbstractThe classical concept of collisional orogens suggests that mountain belts form as a crustal wedge between the downgoing and overriding plates. However, this orogenic style is not compatible with the presence of (ultra-)high pressure crustal and mantle rocks far from the plate interface in the Bohemian Massif of Central Europe. Here we use a comparison between geological observations and thermo-mechanical numerical models to explain their formation. We suggest that continental crust was first deeply subducted, then flowed laterally underneath the lithosphere and eventually rose in the form of large partially molten trans-lithospheric diapirs. We further show that trans-lithospheric diapirism produces a specific rock association of (ultra-)high pressure crustal and mantle rocks and ultra-potassic magmas that alternates with the less metamorphosed rocks of the upper plate. Similar rock associations have been described in other convergent zones, both modern and ancient. We speculate that trans-lithospheric diapirism could be a common process.

scholarly journals Late Orogenic Heating of (Ultra)High Pressure Rocks: Slab Rollback vs. Slab Breakoff

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 499 ◽  
Author(s):  
Elena Sizova ◽  
Christoph Hauzenberger ◽  
Harald Fritz ◽  
Shah Wali Faryad ◽  
Taras Gerya
Keyword(s):  
High Pressure ◽  
Continental Collision ◽  
Crustal Material ◽  
Ultra High Pressure ◽  
Slab Rollback ◽  
Slab Breakoff ◽  
T Path ◽  
Slab Bending ◽  
Lower Crustal ◽  
Collisional Orogens

Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) path. Based on a two-dimensional (2D) coupled petrological–thermomechanical tectono-magmatic numerical model, we propose a possible sequence of tectonic stages that could lead to these overprinting metamorphic events along an orogenic β-shaped P–T–t path: the subduction and exhumation of continental crust, followed by slab retreat that leads to extension and subsequent asthenospheric upwelling. During the last stage, the exhumed crustal material at the crust–mantle boundary undergoes heating from the underlying hot asthenospheric mantle. This slab rollback scenario is further compared numerically with the classical continental collision scenario associated with slab breakoff, which is often used to explain the late heating impulse in the collisional orogens. The mantle upwelling occurring in the experiments with slab breakoff, which is responsible for the heating of the exhumed crustal material, is not related to the slab breakoff but can be caused either by slab bending before slab breakoff or by post-breakoff exhumation of the subducted crust. Our numerical modeling predictions align well with a variety of orogenic P–T–t paths that have been reported from many Phanerozoic collisional orogens, such as the Variscan Bohemian Massif, the Triassic Dabie Shan, the Cenozoic Northwest Himalaya, and some metamorphic complexes in the Alps.

Pressure–temperature–deformation paths of closely associated ultra-high-pressure (diamond-bearing) crustal and mantle rocks of the Kimi complex: implications for the tectonic history of the Rhodope Mountains, northern Greece

2006 ◽  
Vol 43 (12) ◽  
pp. 1755-1776 ◽  
Author(s):  
E Mposkos ◽  
A Krohe
Keyword(s):  
High Pressure ◽  
White Mica ◽  
Temperature Deformation ◽  
Low Grade ◽  
Uhp Metamorphism ◽  
Northern Greece ◽  
Crustal Rocks ◽  
Ultra High Pressure ◽  
T Path ◽  
Static Annealing

The ultra-high-pressure (UHP) Kimi complex (uppermost eastern Rhodope Mountains) is a tectonic mixture of crustal and mantle derived associations. Pressure–temperature (P–T) paths and microtextural and geochronological data reveal that crustal and mantle parts juxtaposed against each other at a depth corresponding to ~15 kbar (1 kbar = 100 MPa) had separate ascend histories. The crustal rocks comprise amphibolitised eclogites, orthogneisses, marbles, and migmatitic pelitic gneisses. The latter document UHP metamorphism within the dehydration-melting range of pelitic gneisses, with maximum P–T conditions of >45 kbar at ~1000 °C, as determined by diamond inclusions in garnet and rutile needle exsolutions in Na-bearing garnet. Decompression was combined with only little cooling before 15 kbar, followed by more significant cooling between 15 and 10 kbar. This P–T path probably reflects ascent of UHP rocks within a subduction channel, followed by accretion in the lower crust of a thickened wedge. Although the first ascend phase was probably rapid, the overall time span for UHP metamorphism and final exhumation may have extended over more than 70 Ma. A U–Pb sensitive high-resolution ion microprobe (SHRIMP) age on zircons of ±149 Ma was suggested to date the UHP metamorphism, whereas Rb–Sr white mica and U–Pb zircon ages from syn-shearing pegmatites of ±65 Ma constrain medium- to low-grade shearing and final exhumation of UHP rocks. Mantle parts consisting of spinel–garnet metaperidotites and garnet pyroxenites reached maximum P–T conditions in the garnet-peridotite field at T > 1200 °C and P > 25 kbar. This was associated with plastic flow and followed by severe near isothermal cooling to T < 800 °C at 15 kbar and static annealing. A garnet–clinopyroxene whole-rock Sm–Nd age from a garnet pyroxenite of ±119 Ma probably reflects the age of metamorphic mantle processes (static annealing following the high P/high T strain episode), rather than constraining the age of UHP metamorphism.

scholarly journals Advances in ultra‐high‐pressure and multi‐dimensional liquid chromatography instrumentation and workflows

2021 ◽  
Author(s):  
Jelle De Vos ◽  
Dwight Stoll ◽  
Stephan Buckenmaier ◽  
Sebastiaan Eeltink ◽  
James P. Grinias
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Ultra High Pressure
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