Pre-metamorphic 40Ar/39Ar and U–Pb ages in HP metagranitoids from the Hercynian belt (France)

Maurel, O.; Monié, Patrick; Respaut, Jean-Patrick; Leyreloup, A.; Maluski, H.

doi:10.1016/s0009-2541(02)00351-0

Cited by 39 publications

(21 citation statements)

References 51 publications

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“…This interpretation is consistent with findings in other high-pressure terranes of white mica Ar dates recording different burial and exhumation stages (Maurel et al, 2003;Gray and Foster, 2004;Putlitz et al, 2005;Di Vincenzo et al, 2006). The only sample that clearly exhibits excess Ar is sample ALP04-01, which demonstrates a textural equilibration and a perfectly equilibrated Rb-Sr systematics ( Figure 7c), but has nevertheless yielded erratic 40 Ar/ 39 Ar step heating results (Figure 8j, k).…”

Section: Significance Of the New 40 Ar/ 39 Ar Data 20supporting

confidence: 90%

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Rosenbaum

Menegon

Glodny

et al. 2012

Lithos

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The Gran Paradiso massif, situated in the internal part of the Western Italian Alps, records a complex tectono-metamorphic history involving high-pressure metamorphism and subsequent exhumation during retrograde metamorphism. The exact timing of deformation and, consequently, the geodynamic evolution of this part of the Western Alps is still debated and is addressed here by the application of Rb/Sr geochronology, 40 Ar/ 39 Ar step heating and 40 Ar/ 39 Ar total fusion dating techniques. forming an extruding wedge. The kinematics associated with this wedge involved topto-W shearing within the Gran Paradiso nappe (e.g. Pont area shear zones) and top-to-E shearing at the top of the extruding wedge (e.g. Orco shear zone). Subsequent deformation (after ~34 Ma) was characterised by coaxial strain involving orogenicscale backfolding and backthrusting.

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Section: Significance Of the New 40 Ar/ 39 Ar Data 20supporting

confidence: 90%

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Rosenbaum

Menegon

Glodny

et al. 2012

Lithos

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“…ARA-23 and JM-8a) were infiltrated by hydrothermal fluids during the late stage D 4 gold event (in contrast to SD-534). Recent work has suggested that thermally reactivated diffusion is less effective in resetting the 40 Ar/ 39 Ar system compared to recrystallisation and/or infiltration of hydrothermal fluids (Maurel et al 2003).…”

Section: Interpretation Of the New 40 Ar/ 39 Ar Agesmentioning

confidence: 99%

Evolution of a reworked orogenic zone: The boundary between the delamerian and lachlan fold belts, southeastern Australia *

Miller

Phillips

Wilson

et al. 2005

Australian Journal of Earth Sciences

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“…(2000) reported from the Bergen Arc Complex (Norway) the retention of Rb–Sr phlogopite ages, which were related to Precambrian granulite facies metamorphism, through Caledonian HP metamorphism at minimum temperatures of at least 650 °C. Maurel et al. (2003) described pre‐metamorphic 40 Ar– 39 Ar biotite ages from the French Variscan belt, which survived overprints under HP and amphibolite facies conditions at temperatures more than 400 °C above those normally estimated for Ar retention in biotite.…”

Section: Miocene Hp Metamorphism In the M1 Marbles On Tinos?mentioning

confidence: 99%

High‐Si phengite records the time of greenschist facies overprinting: implications for models suggesting mega‐detachments in the Aegean Sea

Bröcker¹,

Bieling²,

Hacker

et al. 2004

Journal Metamorphic Geology

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In the lower main unit of the Attic-Cycladic crystalline belt (Greece), white mica geochronology (Rb-Sr, K-Ar, 40 Ar-39 Ar) has established the timing of at least two metamorphic events: well-preserved highpressure/low-temperature (HP/LT) rocks yielded Eocene ages (c. 53-40 Ma) and their greenschist facies counterparts provided Oligocene-Miocene dates (c. 25-18 Ma). Marbles from Tinos Island contain high-Si phengite with Rb-Sr (phengite-calcite) and 40 Ar-39 Ar white mica ages between 41 and 24 Ma. All Ar age spectra are disturbed and 40 Ar-39 Ar total fusion ages generally are 3-6 Ma older than corresponding Rb-Sr ages. Due to the polymetamorphic history, we consider inheritance from the HP stage as the most likely cause for the complex Ar age spectra and the older 40 Ar-39 Ar dates. This concept also suggests that the Rb-Sr system is more sensitive to modification during overprinting than the Ar isotope system, because resetting of the Sr isotope system can be accomplished more quickly by Sr exchange with other Ca-rich phases, whereas lack of pervasive deformation and/or restricted availability of synmetamorphic fluids has favoured partial inheritance of the Ar isotope system. On Tinos, the lowermost part of the metamorphic succession has experienced a pervasive greenschist facies overprint. Si-rich phengite from marbles representing this lithostratigraphic level yielded Rb-Sr ages of c. 24 Ma. If the earlier metamorphic history is not taken into account, such data sets may lead to the erroneous conclusion of Miocene HP metamorphism. This study indicates that this phengite experienced pervasive rejuvenation of the Rb-Sr isotope system during overprinting, without significant changes in Si content, due to bulk-compositional constraints. This leads to the conclusion that in the absence of critical mineral assemblages the Si value of phengite is not a reliable indicator for metamorphic pressures in impure marbles. Recent studies have reported large displacements (>100 km) for detachment faults in the Aegean Sea. A critical parameter for such models is the age of HP metamorphism as deduced from white mica dating in the basal units of the Cyclades. We question the underlying idea of Miocene HP metamorphism and suggest, instead, that this age constrains the timing of the greenschist facies overprint and that the existence of mega-detachments in the study area requires further investigation.

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Pre-metamorphic 40Ar/39Ar and U–Pb ages in HP metagranitoids from the Hercynian belt (France)

Cited by 39 publications

References 51 publications

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Evolution of a reworked orogenic zone: The boundary between the delamerian and lachlan fold belts, southeastern Australia *

High‐Si phengite records the time of greenschist facies overprinting: implications for models suggesting mega‐detachments in the Aegean Sea

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