Tectonics and geochronology of the Rehamna massif (Morocco ... · Michard et al., 2008 Introduction...

Francis Chopin (Czech Geological Survey, UdS, UNS, now at the University of Helsinki)

Michel Corsini (University of Nice)

Karel Schulmann (Czech Geological Survey and University of Strasbourg)

Mohamed El Houicha (Chouaib Doukkali University, Morocco)

Jean-François Ghienne (University of Strasbourg)

Landscape in the Rehamna massif

Tectonic evolution of the Rehamna metamorphic dome (Morocco) in the context of the Alleghanian−Variscan Orogeny

Helsinki Seminar 27 February 2014

francis.chopin@helsinki.fi

Introduction Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Elevation map of Morocco and neighbouring countries

from GTOPO30 database

Michard et al., 2008

Present topography = Cenozoic Alpine belt (i.e 40 Ma to present): Maghrebides (Rif):

parautochthonous and allochthonous

Atlas: intracontinental belts

The post-variscan unconformity on top of a Variscan granite from the High Moulouya massif

Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Michard et al., 2008

Introduction

The post-variscan unconformity on top of Variscan basement (Eastern Rehamna, Daalat unit)

Upper Cretaceous cover

Variscan basement

Upper Cretaceous cover

Photo: F. Chopin

Introduction

Extension of the Paleozoic and Precambrian and Paleozoic outcrops

modified from Piqué and Michard (1989), in Michard et al., 2008

Introduction

Image Credit: Ray Troll’s (http://www.trollart.com/)

Alpine Orogeny (Atlas, Rif…)

Alleghanian−Variscan Orogeny (Meseta, Appalachian)

Svecofennian orogeny

Karelian craton

Introduction

Nance et al., 2008

Alleghanian−Variscan Orogeny

Lower Permian

Palaeogeographic reconstructions Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Cocks & Torsvik, 2006

Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi Palaeogeographic reconstructions

Objectives

• Tectonic at the Gondwana margin

• Time scale of tectonic and magmatic events

• Geodynamic of the Alleghanian−Variscan belt

Photo: F. Chopin

The Morocco variscides

• South-Western branch of the Variscan Belt at the NW Gondwana margin

• A late Carboniferous to early Permian orogen reworking Early Carboniferous intracontinental basins and its basement

Chopin et al., 2014

Modified after Hoeppfner et al., 2005 and Michard et al., 2008

Western Meseta

The Rehamna massif Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Lower metam. unit

Upper metam. unit

Wegmann ,1935 12

Chopin et al., 2014

The Rehamna massif Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Compilation: Chopin et al., 2014

Chopin et al., 2014

Lower metam unit

• Moderatly dipping to subhorizontal metamorphic foliation

• Top to the SW−SSW shearing Diot, 1989

Quartz CPO

D1: structure and kinematic Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Chopin et al., 2014

Photo: F.Chopin

Baguette Express – © Susan Eby Glass

Lower metamorphic unit:

E-W trending dome

Upper metam unit 2km

Lower metam unit

Upper metamorphic unit:

Fold and thrust belt

D1 to D2: structures Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Chopin et al., 2014

Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi D1 to D2: structures

Photo: F.Chopin

S2 β2

40Ar/39Ar Geochronology

Photo: Chrystele Verati

Photo: Nevada Isotope Geochronology Lab

Before measurement • Crushing, cleaning of selected samples • Hand-picking of single grains (e.g. micas, amphibole) • Irradiation (Nuclear reactor at the McMaster University in Hamilton) Measurement • Step heating using a CO2 Synrad laser • Isotopic measurements using mass spectrometer

Photo: Chrystele Verati

Before measurement • Crushing, cleaning of selected samples • Hand-picking of single grains (e.g. micas, amphibole) • Irradiation (Nuclear reactor at the McMaster University in Hamilton) Measurement • Step heating using a CO2 Synrad laser • Isotopic measurements using mass spectrometer

Relevant 40Ar/39Ar Plateau age: 1) at least 70% of released 39Ar 2) at least three successive steps in the plateau 3) the integrated age of the plateau should agree with each apparent age of the plateau within

a 1σ error confidence interval

McDougall and Harrison, 1999

Diagram illustrating accumulation of radiogenic argon in an igneous rock as it cools from magmatic temperatures

Undisturbed Loss Excess

40Ar/39Ar age spectra

D1 to D2: geochronology

309.43 ± 7.16 Ma

10 20 30 40 50 60 70 80 90

Cumulative 39Ar Released (%)

Biotite R061A

Sidi Ali (North)

Mica schist (St + Grt)

Chopin et al., 2014

Interpretation: time of cooling during syn-convergent doming 23

309.4±7.1 Ma

Cumulative 39Ar Released (%)Cumulative 39Ar Released (%)

301.10 ± 6.30 Ma

10 20 30 40 50 60 70 80 90

Muscovite R147

Lalla Titaf (East)

Mica schist (Ms + Bt)

D1 to D2: geochronology

Chopin et al., 2014 Interpretation: time of cooling during syn-convergent doming 24

301.1±6.3 Ma

D3 structures

• Folding of the Coastal block (Cambrian) • Curvature of the upper metam anticline • Folding of isograds • Development of a circular subdome

Chopin et al., 2014

D3 structures

WNW-ESE compression

reworking of the upper and lower metamorphic units

Chopin et al., 2014

D3 structures Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

S3 β3

WNW ESE

D3 geochronology

285.46 ± 5.64 Ma

10 20 30 40 50 60 70 80 90

Muscovite 11-01B

Sidi Ali Dôme

Orthogneiss

Chopin et al., 2014

Interpretation: resseting of Argon system during D3 28

285.5±5.6 Ma

284.57 ± 6.39 Ma

10 20 30 40 50 60 70 80 90

Muscovite 12-02C

Lalla Tittaf (West)

Metarhyolite

D3 geochronology

WNW ESE

Chopin et al., 2014

Interpretation: resseting of Argon system during D3 29

284.6±6.4 Ma

D3 syn tectonic magmatism

WNW ESE

Associated dykes 285,4 ± 6,1 Ma (U-Pb zircon, Guerrot in Baudin et al., 2003)

284.16 ± 5.54 Ma

10 20 30 40 50 60 70 80 90

Muscovite R159

Rais El Biod (border)

Syn tectonic

Chopin et al., 2014

Interpretation: time of crystallization of the syntectonically (D3) emplaced granite 30

284.16 ± 6.54

284.2±5.5 Ma

Late variscan magmatism

274.85 ± 5.43 Ma

10 20 30 40 50 60 70 80 90Cumulative 39Ar Released (%)

Biotite (R166)

Sebt de Brikiine

Late/post tectonic

Similar to the datation made by Tisserand, 1977 (recalculated by Michard et al., 1982): 278 ±2 Ma (Rb/Sr)

Chopin et al., 2014

Interpretation: emplacement of the late/post tectonic batholith

274.8±5.4 Ma

Interpretation of orogenic fabrics

Late Carboniferous to Early Permian (315−290 Ma)

D1: top to the SSW stacking D2: NNE−SSW syn convergent doming

Early Permian (290−280 Ma)

+ post tectonic

Magmatism (275 Ma)

D3: WNW directed compression

Chopin et al., 2014

Cocks & Torsvik, 2006 33

Alleghanian−Variscan Orogeny Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Gutiérrez-Alonso et al., 2012 Buckling an orogen: The Cantabrian Orocline GSA Today, v. 22, no. 7, doi: 10.1130/GSATG141A.1.

34 Gutiérrez-Alonso et al., 2012

Gutiérrez-Alonso et al., 2012

Buckling an orogen: The Cantabrian Orocline

Chopin et al., 2014

Engelder and Whitaker, 2006

Study of cleat (natural fractures in coal) and joint in the Alleghanian orogeny

Terry Engelder, 2008, AAPG presentation

Older, deeper coal, Appalachian Wide Field Stress cleat joint Terry Engelder, 2008, AAPG presentation

Younger, shallower coal: Alleghanian trending cleat and joint

Terry Engelder, 2008, AAPG presentation

Engelder and Whitaker, 2006

Hatcher, 2002 Hatcher, 2010

Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi Palaeogeographic reconstructions

Alleghanian−Variscan Orogeny

Paleogeographic reconstructions after Cocks & Torsvik [2006] at 310 and 280 Ma.

Tectonic datas from this study (Morocco) and

bibliography

Chopin et al., 2014

310 Ma

280 Ma

Chopin et al., 2014

Conclusion

• Late Carb. to Early Permian (315−290 Ma): SSW directed compression

• Early Permian (290−275 Ma): WNW directed compression + Magm

• Late/post tectonic magmatism at 275 Ma

Major change in tectonic regime in Morocco

Correlation with Alleghanian−Variscan belt

• 315−290 Ma: convergence of the Gondwana landmass with the European Variscan collage to the north. At the same time the eastern margin of Laurentia was undergoing dextral strike slip deformation

• 290−275 Ma: Head-on collision between Gondwana and Laurentia while Europe was subject to major dextral wrench deformation

Photo: F.Chopin

Landscape and peoples Helsinki Seminar 27 February 2014 francis.chopin@helsinki.fi

Photo: F.Chopin

Landscape and peoples

48 Photo: F.Chopin

Landscape and peoples

Photo: F.Chopin

Tectonics and geochronology of the Rehamna massif (Morocco ... · Michard et al., 2008 Introduction...

Documents

The Variscan fore land in Po land re vis ited: new data

Supplementary Material to Johansson, Wulfetange, Porée, Michard, Gajdanowicz, Lacombe, Sentenac, Thibaud, Mueller-Roeber, Blatt, Dreyer External [K + ]

Structure of late Variscan Millevaches leucogranite massif ... · Structure of late Variscan Millevaches leucogranite massif in the French Massif Central: AMS and gravity modelling

Pre-Alpine (Variscan) Inheritance: A Key for the Location

A two-stage exhumation of the Variscan crust: U–Pb LA-ICP-MS and

THE VARISCAN EVOLUTION OF THE CULM BASIN, … · THE VARISCAN EVOLUTION OF THE CULM BASIN, SOUTH-WEST ... orogenic wedge produced tectonic ... formation were first recognized by Brooks

Franz Kossmat – Subdivision of the Variscan … › 4085 › 1 › Meinhold_2017_HGSS.pdf30 G. Meinhold: Franz Kossmat – Subdivision of the Variscan Mountains mat, 1921). Amongst

Bosse_Early-orogenic Exhumation Eclogites Champtoceaux Complex (Variscan belt, France)_Geological Journal 2000

Association Nationale des Plaisanciers en Eaux Intérieures (ANPEI) Le projet de port « Vieille Montagne » 8 décembre 2010 Alain Michard Administrateur

New U-Pb SHRIMP zircon ages for pre-variscan orthogneisses … · 2006-03-13 · pre-Variscan plutonic activity is more evident than in the northern part of the Iberian Massif and

VariScan Documentation - Universitat de Barcelona

La pression artérielle sanglante comme outil prédictif du ...reamed.ujf-grenoble.fr/seminaires/archives/2008/juin08/1lundi/PA... · Delta PP [Michard F, AJRCCM, 2000] Delta PP [Michard

Middle Carboniferous crustal melting in the Variscan Belt - HAL

Distinct sources for syntectonic Variscan granitoids: Insights … · Distinct sources for syntectonic Variscan granitoids: Insights from the Aguiar da Beira region, Central Portugal

Листа уџбеника за школску 2016/2017. годину udzbenika... · Collection littéraire Lagarde et Michard Bordas, 1985 - André Lagarde, Laurent Michard, 1

The shape of the Variscan Belt in Central Europe: Strike-slip ......Seismic constraints on the position of the Variscan deformation front come from (1) the GRUNDY 2003 seismic experiment,

4. Variscan Orogenesis. 1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North Atlantic Tertiary Igneous Province (NATP)

Variscan Skarn Ores in South·West Sardinia: their ... · Variscan Skarn Ores in South·West Sardinia: their relationships with Cambro·Ordovician stratabound deposits FABIO AroNTE,

VARISCAN BASEMENT IN NORTH SARDINIA AND CORSICA Field …

THE VARISCAN BASEMENT OF NORTHERN SARDINIA (ITALY): …