Project

Back to overview

High pressure evolution in the internal Western Alps

English title High pressure evolution in the internal Western Alps
Applicant Engi Martin
Number 126946
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geology
Start/End 01.10.2009 - 31.03.2013
Approved amount 692'805.00
Show all

Keywords (12)

metamorphic petrology; geochronology; high pressure; continental subduction; Western Alps; Rare Earth minerals; Sesia Zone; Dent Blanche nappe; PTt-paths; thermal evolution; polycyclic orogen; in situ geochronology

Lay Summary (German)

Lead
Lay summary
In tektonischen Subduktions- bzw. Kollisionszonen entstehen Hochdruck-Gesteine, z.B. Eklogite und Blauschiefer. Die internen Westalpen gelten als klassischer Gebirgsgürtel mit einem Spektrum solcher HP-Gesteine. So finden sich in der Sesia-Zone km-grosse Decken von kontinentaler Kruste, die zunächst in Tiefen von 40-70 km versenkt wurden, um dann rasch wieder zur Erdoberfläche zu gelangen. Obschon von fundamentaler Bedeutung in der Geodynamik, versteht man die komplexen Prozesse an destruktiven Plattenrändern noch immer ungenügend. Speziell ist in den Westalpen die räumlich-zeitliche Entwicklung der HP-Metamorphose kontrovers.Dieses Projekt erforscht die Gesteinsbildung, Deformation und geochemischen Prozesse, welche die Entstehung der HP-Gesteine am Nordrand des adriatischen Kontinents bedingt haben. Strukturell kontrollierte Proben von metamorphen Gesteinen aus mehreren tektonischen Einheiten werden untersucht, von denen die meisten bereits prä-alpin in Gebirgsgürteln gebildet worden sind. Mittels mikrochemischer Analyse von lokalen Mineralgleichgewichten werden die in HP-Gesteinen gespeicherten Druck-Temperatur Bedingungen rekonstruiert und die relative zeitliche Abfolge zur mehrphasigen Deformation geklärt. In geeigneten Proben wird das Alter der HP-Stadien datiert, v.a. mittels Monazit, Allanit und Titanit. Dazu werden Methoden der in situ U-Th-Pb Chronometrie (LA-ICP-MS) verbessert. Diese Mineralalter und P-T-Resultate haben in der ersten Phase des Projekts robuste Daten zur Frühphase der Orogenese in den Westalpen liefern. Die Untersuchung mehrfach metamorpher Gesteine wird das Verständnis der geochemischen Mobilität und Fluid-Gesteins Interaktion im Bereich der tiefen Subduktion vertiefen.High pressure rocks, such as blueschists and eclogites, form in suduction and collision zones. The internal Western Alps (e.g. Sesia zone) are considered a classic area of (largely continental) high pressure metamorphism, encompassing a broad spectrum of HP-rocks. However, the dynamics of processes leading to HP-terranes, notably the timing and conditions of the early collisional history in the Western Alps, remain poorly understood.This project focuses on the processes leading to the formation of high pressure terranes. Structurally controlled samples from several (mono- and polycyclic ones) tectonic units of the Western Alps shall be analyzed. Local mineral equilibria are used for thermobarometry, and assemblages are related to the polydeformation. The best suited samples are used to date the early HP-metamorphism using improved in situ dating techniques based on U-Th-Pb isotopic analysis of allanite, monazite, and titanite by LA-ICP-MS.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
The pre-Alpine tectonic history of the Austroalpine continental basement in the Valpelline unit (Western Italian Alps)
Manzotti Paola, Zucali Michele (2013), The pre-Alpine tectonic history of the Austroalpine continental basement in the Valpelline unit (Western Italian Alps), in Geological Magazine, 150(1), 153-172.
From Permo-Triassic lithospheric thinning to Jurassic rifting at the Adriatic margin: Petrological and geochronological record in Valtournenche (Western Italian Alps)
Manzotti P, Rubatto D, Darling J, Zucali M, Cenki-Tok B, Engi M (2012), From Permo-Triassic lithospheric thinning to Jurassic rifting at the Adriatic margin: Petrological and geochronological record in Valtournenche (Western Italian Alps), in LITHOS, 146, 276-292.
Dating emplacement and evolution of the orogenic magmatism in the internal Western Alps: 1. The Miagliano Pluton
Berger A., Thomsen T.B., Ovtcharova M., Kapferer N., Mercolli I. (2012), Dating emplacement and evolution of the orogenic magmatism in the internal Western Alps: 1. The Miagliano Pluton, in Swiss Journal of Geoscience, 105, 49-65.
Redistribution of REE, Y, Th and U at high pressure: Allanite-forming reactions in impure meta-quartzites (Sesia Zone, Western Italian Alps)
Regis D., Cenki-Tok B., Darling J., Engi M. (2012), Redistribution of REE, Y, Th and U at high pressure: Allanite-forming reactions in impure meta-quartzites (Sesia Zone, Western Italian Alps), in Amer. Mineral., 97, 315-328.
Allanite U-Th-Pb geochronology by laser ablation ICP-MS
Darling J., Storey C., Engi M. (2012), Allanite U-Th-Pb geochronology by laser ablation ICP-MS, in Chemical Geology, 292-293, 103-115.
Petro-structural map of the Dent Blanche tectonic system between Valpelline and Valtournenche valleys, Western Italian Alps
Manzotti Paola (2011), Petro-structural map of the Dent Blanche tectonic system between Valpelline and Valtournenche valleys, Western Italian Alps, in JOURNAL OF MAPS, 340-352.
Allanite behaviour during incipient melting in the southern Central Alps
Gregory C., Rubatto D., Hermann J., Berger A., Engi M. (2011), Allanite behaviour during incipient melting in the southern Central Alps, in Geochim. Cosmochim. Acta, 84, 433-458.
Preservation of Permian allanite within an Alpine eclogite facies shear zone at Mt Mucrone, Italy: Mechanical and chemical behavior of allanite during mylonitization
Cenki-Tok B, Oliot E, Rubatto D, Berger A, Engi M, Janots E, Thomsen TB, Manzotti P, Regis D, Spandler C, Robyr M, Goncalves P (2011), Preservation of Permian allanite within an Alpine eclogite facies shear zone at Mt Mucrone, Italy: Mechanical and chemical behavior of allanite during mylonitization, in LITHOS, 125(1-2), 40-50.
Permian tectonometamorphic evolution of the Dent-Blanche Unit (Austroalpine domain,Western Italian Alps)
Zucali M, Manzotti P, Diella V, Presenti C, Rispendente A, Darling J, Engi M (2011), Permian tectonometamorphic evolution of the Dent-Blanche Unit (Austroalpine domain,Western Italian Alps), in Rendiconti online Soc. Geol. It, 15, 133-136.
Yo-yo subduction recorded by accessory minerals in the Italian Western Alps
Rubatto D, Regis D, Hermann J, Boston K, Engi M, Beltrando M, McAlpine SRB (2011), Yo-yo subduction recorded by accessory minerals in the Italian Western Alps, in NATURE GEOSCIENCE, 4(5), 338-342.
Physico-chemical control on the REE minerals in chloritoid-grade metasediments from a single outcrop (Central Alps, Switzerland)
Janots E, Berger A, Engi M (2011), Physico-chemical control on the REE minerals in chloritoid-grade metasediments from a single outcrop (Central Alps, Switzerland), in LITHOS, 121(1-4), 1-11.

Collaboration

Group / person Country
Types of collaboration
University of Portsmouth Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Università di Torino Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Exchange of personnel
Université de Montpellier France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
ANU Canberra Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Università di Milano Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Universität Basel Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Swiss Geoscience Meeting 17.11.2012 Bern
Erdwissenschaftliches Kolloquium 03.05.2012 ETH Zürich
Goldschmidt Conference 14.08.2011 Prag
ILP-Workshop (Internat. Lithoprobe Porgram) 02.07.2011 Sampeyre, Itlien
Alpine Workshop 10.04.2011 Corsica
Metamorphic Studies Group 22.03.2011 Cambridge, UK
AGU 13.12.2010 San Francisco
Swiss Geoscience Meeting 19.11.2010 Fribourg


Associated projects

Number Title Start Funding scheme
117996 High pressure evolution in the internal Western Apls 01.10.2007 Project funding (Div. I-III)
146175 High pressure evolution in the internal Western Alps 01.04.2013 Project funding (Div. I-III)

Abstract

A field-based project aims to reconstruct the tectonometamorphic evolution of the internal Western Alps, a classic high-pressure terrain. Characterized by predominantly continental rocks, most of the polycyclic, the current picture of this important orogenic segment is wrought with discrepant age data and a paucity of data relating to the initial convergence at the Apulian margin. This project concentrates on monometamorphic units uints first, to work out the Alpine history by integrating structural, petrological, and geochronological methods. In the second part, polymetamorphic units are investigated as well, and the processes and scale of crustal recycling as well as the assembly of the orogen are worked out.Much emphasis is laid on extending the possibilities of in situ isotopic age dating of robust mineral chrono¬meters, notably allanite and monazite, using Th-Pb and U-Pb analysis. An improved procedure for LA-ICP-MS analysis is developped and applied in conjunction with ion probe (SHRIMP) dating. Work on isotopic standard materials is proposed, again primarily for allanite. The reaction mechanisms of allanite and its potential for integrated petrochronometry are investigated. Field work in the Dent Blanche nappe, the central and southern Sesia Zone, and in several Austroalpine klippen units includes detailed mapping, structurally controlled sampling, and correlation. Petrological and geochronological analysis of samples aims to quantify the spatial and temporal evolution of tectonic units. Quantitative PTDt-paths are derived, yielding constraints on the rates of tectonometamorphic processes (heating, subduction, mineral reaction, and exhumation). A number of currently hot problems of metamorphic petrology and geochemistry are addressed as part of this comprehensive study. These include the extent of re-equilibration of polymetamorphic rocks (including eclogite facies superimposed on granulite facies), the mobility of trace element, and the REE-budget in various metamorphic environments under high pressure conditions.
-