Triassic magnetic overprints related to albitization in granites from the Morvan massif (France)

Ricordel, Caroline; Parcerisa, David; Thiry, Médard; Moreau, Marie-Gabrielle; Gómez‐Gras, David

doi:10.1016/j.palaeo.2007.04.001

Cited by 20 publications

(23 citation statements)

References 39 publications

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“…This haematite increase does not fit with fluids of basinal origin, but can be related to interactions with the atmosphere in shallower environments. It has to be emphasized that palaeomagnetic analysis has revealed an Early Triassic magnetic overprint in the albitised basement rocks of the Morvan massif (Ricordel et al 2007). The age obtained for this phenomenon, strengthens the hypothesis that albitisation developed in relation with palaeoweathering processes linked with the Triassic palaeosurface.…”

Section: Discussionmentioning

confidence: 99%

“…Likewise, K-Ar datings of the secondary minerals give Triassic ages for these albitised rocks (Bonhomme et al 1980;Schmitt et al 1984), and recent palaeomagnetic dating of the haematite bound with the albitised facies in the Morvan Massif lead also to ascribe a Triassic age to the albitisation of this region (Ricordel et al 2007). …”

Section: Deep Weathering Processes In Emerged Areasmentioning

confidence: 98%

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Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France)

Parcerisa

Thiry

Schmitt

2009

Int J Earth Sci (Geol Rundsch)

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The Carboniferous Morvan Massif, in the northern part of the French Massif Central, consists of granite and some rhyolite. A Triassic erosional unconformity has developed on the massif which is covered by Mesozoic sediments of the Paris Basin. The igneous rocks of the Morvan Massif show a strong alteration with pseudomorphic replacement of the primary plagioclases into albite, pseudomorphic replacement of primary biotite into chlorite and minor precipitation of neogenic minerals like albite, chlorite, apatite, haematite, calcite and titanite. The geometry and arrangement of these alterations give significant constraints about their development. Some of the altered facies develop in a pervasive manner; others are restricted to centimetric to metric-wide joints that imply fluid-flow phenomena. Moreover, the alteration facies are arranged in a clear succession with strongly altered facies at the top and weakly altered facies towards the depth, which point to a genetic relationship with the Triassic unconformity. Regional distribution of the alterations, which affect the Carboniferous igneous and volcanic formations beneath the Jurassic sedimentary cover, also leads to associate these alterations with the Triassic unconformity. Dating of the alterations provides even a further constraint, alterations are of Triassic age, that means the same age as the unconformity. Taking into account all these geological constraints, it is proposed that albitisation of the Morvan Massif was developed under low temperature subsurface conditions in relation to the Triassic palaeosurface.

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Section: Discussionmentioning

confidence: 99%

Section: Deep Weathering Processes In Emerged Areasmentioning

confidence: 98%

Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France)

Parcerisa

Thiry

Schmitt

2009

Int J Earth Sci (Geol Rundsch)

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“…Many of these remagnetizations reside in authigenic haematite and are interpreted to be caused by weathering fluids (e.g. Ricordel et al 2007;Franke et al 2010;Fàbrega et al 2012). A study of dolomite veins in the Precambrian-Early Palaeozoic Dalradian schist in Scotland reported a Carboniferous -Triassic CRM which was interpreted as being related to deep oxidizing weathering (Parnell et al 2000).…”

Section: Weathering Fluidsmentioning

confidence: 99%

Remagnetization and chemical alteration of sedimentary rocks

Elmore

Muxworthy

Aldana

2012

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Chemical remagnetization is a very common phenomenon in sedimentary rocks and developing a greater understanding of the mechanisms has several benefits. Acquisition of a secondary magnetization is usually tangible evidence of a diagenetic event that can be dated by isolation of the chemical remanent magnetization and comparison of the pole position to the apparent polar wander path. This can be important because diagenetic investigations are frequently limited by the difficulty in constraining the time frames in which most past events have occurred. Remagnetization can commonly obscure a primary magnetization; developing a better understanding of remagnetization could improve our ability to uncover primary magnetizations. Many chemical remagnetization mechanisms have been proposed, including those associated with chemical alteration by a number of different fluids (orogenic, basinal and hydrocarbons), burial diagenetic processes (clay diagenesis and maturation of organic matter) or other processes. This paper summarizes our current knowledge of these chemical remagnetization mechanisms, with a focus on examples where there is a connection with chemical alteration.

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“…(1) Triassic: the albitization of bedrock outcrops is widely reported from the Variscan basement uplands of Europe (French Massif Central: Schmitt and Simon-Coincon, 1985;Ricordel et al, 2007;Parcerisa et al, 2010a;Bohemian Massif: Franke et al, 2009;Yao et al, 2010;Iberia: Franke et al, 2009;Parcerisa et al, 2010b). The dating of this event is based on their location beneath the Jurassic sedimentary cover (Schmitt and Simon-Coincon, 1985;Ricordel et al, 2007;Parcerisa et al, 2010a) and the early Triassic magnetic overprints (95% reference pole confidence cone between 235 Ma and 255 Ma, Ricordel et al, 2007).…”

Section: Is the Geomorphological Evolution Of The Armorican Massif Unmentioning

confidence: 99%

“…The dating of this event is based on their location beneath the Jurassic sedimentary cover (Schmitt and Simon-Coincon, 1985;Ricordel et al, 2007;Parcerisa et al, 2010a) and the early Triassic magnetic overprints (95% reference pole confidence cone between 235 Ma and 255 Ma, Ricordel et al, 2007).…”

Section: Is the Geomorphological Evolution Of The Armorican Massif Unmentioning

confidence: 99%

Planation surfaces of the Armorican Massif (western France):Denudation chronology of a Mesozoic land surface twice exhumed in response to relative crustal movements between Iberia and Eurasia

et al. 2015

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The Armorican Massif, an extensive outcrop of Variscan basement in western France, is shaped by several planation surfaces of debated origin and age. We propose an evolution model for these landforms and their deformation based on detailed mapping of the planation surfaces, their relative chronology and their relationships with dated outcrops of sediments and weathering products. The Armorican landscape consists of six stepped planation surfaces (labeled PS1 to PS6) later incised by two successive river networks. These landforms are pediments and pediplains or polygenic landforms (Armorican Planation Surface -PS5) resulting from two periods of etchplanation. These planation surfaces are mostly pre-late Cretaceous in age, based on the age of the sediments overlapping these pediments. The three older ones (PS1 to PS3) are pre-Pliensbachian (191-183 Ma); PS4 is preBajocian (170-168 Ma), PS5 (here called the "Armorican Planation Surface") is polygenic and ranges from the base of the early Cretaceous to the base of the Bartonian (140-40 Ma); and the youngest (PS6), which is poorly constrained, is older than 40 Ma (base of the Bartonian) or 15 Ma (base of the middle Miocene). Most of these "old" landforms are exhumed, i.e. they were buried by sediments and later re-exposed by denudation. At least two phases of burial and exhumation have been identified: (1) burial in Jurassic time followed by denudation during the early Cretaceous and (2) burial in late Cretaceous time followed by denudation during the latest Cretaceous to early Eocene. The depth of burial is unknown but is probably low due to the small amount of coeval siliciclastic sediments in the surrounding basins. The two periods of exhumation correspond to critical periods in the plate movements between Africa, Iberia and Eurasia. The first is probably related to the initiation and break-up of the rift between Iberia and Eurasia and the second to the convergence between these two plates.

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Triassic magnetic overprints related to albitization in granites from the Morvan massif (France)

Cited by 20 publications

References 39 publications

Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France)

Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France)

Remagnetization and chemical alteration of sedimentary rocks

Planation surfaces of the Armorican Massif (western France):Denudation chronology of a Mesozoic land surface twice exhumed in response to relative crustal movements between Iberia and Eurasia

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