The tectono-metamorphic evolution of the very low-grade hangingwall constrains two-stage gneiss dome formation in the Montagne Noire (Southern France)

2014 ◽  
Vol 33 (1) ◽  
pp. 71-89 ◽  
Author(s):  
M. P. Doublier ◽  
S. Potel ◽  
K. Wemmer
Keyword(s):  
Low Grade ◽  
Metamorphic Evolution ◽  
Two Stage ◽  
Gneiss Dome ◽  
Southern France ◽  
Dome Formation ◽  
Montagne Noire

scholarly journals Thermal interaction of middle and upper crust during gneiss dome formation: example from the Montagne Noire (French Massif Central)

2016 ◽  
Vol 34 (5) ◽  
pp. 447-462 ◽  
Author(s):  
K. Fréville ◽  
B. Cenki-Tok ◽  
P. Trap ◽  
M. Rabin ◽  
A. Leyreloup ◽  
...  
Keyword(s):  
Thermal Interaction ◽  
Upper Crust ◽  
French Massif Central ◽  
Gneiss Dome ◽  
Massif Central ◽  
Dome Formation ◽  
Montagne Noire

On the origin of Early Proterozoic gneiss domes and metamorphic nodes, northern Michigan

1996 ◽  
Vol 33 (7) ◽  
pp. 1053-1053 ◽  
Author(s):  
David Schneider ◽  
Daniel Holm ◽  
Daniel Lux
Keyword(s):  
Gravity Anomaly ◽  
Gneiss Dome ◽  
Near Surface ◽  
Dome Formation ◽  
Crustal Shortening ◽  
Gneiss Domes ◽  
History Of ◽  
The Republic ◽  
Different Origins ◽  
Northern Michigan

Biotite 40αr/39αr cooling ages from medium-pressure (500–600 MPa) rocks in the Watersmeet district, northern Michigan, suggest significant cooling–uplift and concomitant deformation during gneiss dome formation at~1755 Ma, well after the close of the 1870–1830 Ma Penokean orogeny. However, an 1822 Ma hornblende plateau date indicates that the isograds surrounding the dome are Penokean in age. We attribute gneiss dome formation and doming of Penokean-aged isograds to an episode of orogenic collapse superimposed on an earlier history of crustal shortening. This contrasts with the compressional origin for gneiss domes preserved in the low-pressure (200–300 MPa) Republic district. The different origins may reflect the fact that collapse was localized along the overthickened region of the orogenic belt. In contrast to the Watersmeet area, hornblende and biotite 40Ar/39Ar ages obtained from the Republic area are 1720–1680 Ma. Given the relatively shallow depth of this region, it is unlikely that temperatures remained above 500 °C for over 100 Ma following collision. We interpret these ages to reflect a major thermal event that may have been responsible for formation of the Republic metamorphic node. This interpretation is supported by the recent identification of an ~1730 Ma pluton that is likely the cause of a large, near-surface, negative gravity anomaly coincident with the node, and by the fact that the metamorphic node crosscuts Penokean structures.

Isograds and mineral assemblages in the eastern axial zone, Montagne Noire (France): implications for temperature gradients and P–T history

1982 ◽  
Vol 19 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Peter H. Thompson ◽  
Jean-Pierre Bard
Keyword(s):  
Metamorphic Grade ◽  
Temperature Gradients ◽  
Low Grade ◽  
Reaction Sequence ◽  
Axial Zone ◽  
Rock Composition ◽  
Mineral Assemblages ◽  
Montagne Noire ◽  
Sequence Study

Detailed petrography across a metapelitic sequence in the eastern axial zone of the Montagne Noire, France, is the basis for a sequence of isograds marking the first appearance of biotite–cordierite, staurolite, andalusite, and sillimanite. The juxtaposition of low-grade biotite-free rocks against medium-grade rocks at the gently dipping biotite–cordierite isograd is attributed to tectonic telescoping of the metamorphic sequence. Study of mineral assemblages with respect to an AFM reaction sequence indicates the staurolite isograd is related to changes in rock composition, and complex assemblages in the sillimanite zone may be the result of unstable persistence of minerals formed when metamorphic grade was lower. These assemblages are interpreted to contain a record of part of the P–T history during which pressure decreased as temperature increased. P–T profiles show that temperature gradients of 200–300 °C/km suggested by previous workers are not required to explain the isograd pattern; gradients of 37 °C/km or less are sufficient.

Depositional controls on Early Cambrian microbial carbonates from the Montagne Noire, southern France

1998 ◽  
Vol 89 (3) ◽  
pp. 135-143 ◽  
Author(s):  
J. Javier Álvaro ◽  
Emmanuelle Vennin ◽  
Daniel Vizcaïno
Keyword(s):  
Lower Cambrian ◽  
Southern France ◽  
Microbial Structures ◽  
Subaerial Exposure ◽  
Open Sea ◽  
Montagne Noire ◽  
Constructed Self ◽  
Depositional Controls ◽  
First Time ◽  
Open Shelf

AbstractLower Cambrian shallow-water carbonates enclosing microbial structures are documented for the first time from the upper Lastours Member of the Montagne Noire (southern France). Microbial organisms constructed self-supported boundstones resulting in the formation of exclusively microbial-accreted buildups, which exhibit three main types of non-skeletal microbialites: planar stratiform stromatolites, dome-shaped stromatolites and nonlaminated (thrombolitic) biostromes. In addition, thrombolitic boundstones display four distinct microbial microstructures: clotted andRenalcis-like forms, branching bushy forms, clusters of unbranching straight filaments and crustose forms.The upper member of the Lastours Formation records an upward transition from a shalydominant open shelf to a protected shelf environment bounded by a surface representing a major subaerial exposure. Initially, at the inception of the highstand systems tract, flat stratiform stromatolites formed on open sea subtidal shaly substrates, while stacked domal stromatolites developed in peritidal areas which record subaerial exposure. In contrast, prograding shoal barriers of the transgressive systems tract favoured the establishment of thrombolitic boundstones in protected (back-shoal) environments.

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