Migmatizacion of the basal paragneisses of the Filali Unit (Beni Bousera massif, Morocco) during polyphase extensional tectonics

Los paragneises basales de la Unidad de Filali registran dos episodios migmatíticos: (a) un episodio de media-presión (710-810°C y 6.6-9 kbar) relacionado con el colapso extensional tardi-Varisco que afectó a la sección litosférica de los Sebtides inferiores; y (b) un episodio de baja-presión de edad Alpina, que produjó cordierita durante una descompresión casi isotérmica (640-760°C y 4.5-5 kbar), asociado a la apertura durante el Oligoceno superior-Mioceno del dominio de Alboran

Oligo-Miocene exhumation of the Beni-Bousera peridotite through a lithosphere-scale extensional shear zone

New structural data and P-T estimates of syn-deformational assemblages within the Beni Bousera peridotites and their crustal envelope are used to explain their Alpine exhumation. The Beni Bousera peridotites occur as thin sheets within high grade crustal units of the lower Sebtides (inner Rif, Morocco) and are composed of weakly deformed spinel lherzolite in the core of the massif and garnet-spinel mylonite at the rim. The main foliation trajectories in both the peridotites and overlying crustal units show systematic rotation towards their mutual contact, indicating a kilometer-scale top to the NW shearing with a dextral component along this crust/mantle contact. Widespread top to the NW shear criteria within the crustal units overlying the peridotite support this feature. Available ages constrain the development of the main foliation in both the peridotites and crustal rocks between 25 and 20 Ma. New P-T data from the peridotites show that deformation occurs during decompression from approximate to 22 kbar, 1050 degrees C to approximate to 9-15 kbar, 800 degrees C. As a consequence, exhumation of the Beni Bousera peridotites takes place during the Oligo-Miocene lithosphere thinning in the footwall of a lithospheric extensional shear zone. The exceptional preservation of garnet within the mylonitic peridotites results from rapid cooling of the border of the massif due to the juxtaposition with colder crustal rocks along this shear zone. Uplifting of the hot mantle rocks simultaneously induces high temperature metamorphism in the overlying crustal units. These new findings allow us to reconstruct the deformation history of the Beni Bousera region and the Alboran domain in the framework of the western Mediterranean geodynamics during the last 40 Myrs.. (C) 2011 Lavoisier SAS. All rights reserve

Etude métamorphique des micaschistes et gneiss de l'unité de Filali du Massif de Beni Bousera (Rif interne, Maroc)

Les péridotites du massif de Béni Bousera sont, avec les péridotites de Ronda, des péridotites sous-continentales appartenant aux domaines internes des chaînes Alpines du Rif et des Bétiques, respectivement. Leurs exhumations et leurs insertions dans la croûte se font dans un contexte de recul de la subduction Alpine vers le Sud et l'Ouest durant l'Oligo-Miocéne. Pour étudier l'amincissement crustal dans ce contexte d'extension arrière-arc, lié à la mise en place de ces péridotites, nous avons étudié les conditions P-T associées à des différents épisodes déformationels dans leur encaissant (Sébtides inférieures, unité de Filali). Cette unité présente une évolution tectonométamorphique polyphasée. En s'approchant du massif des péridotites, une première schistosité (S1) est associée à des paragenèses allant de grenat-biotite; grenat-staurotide-disthène-biotite à grenat-biotite-feldspath potassique ± disthène. La deuxième schistosité (S2) est associée à des paragenèses à biotite-andalousite loin des péridotites et sillimanite-biotite prés des péridotites. Le grade métamorphique de terrain augmente vers les péridotites pour les deux schistosités. En utilisant les pseudosections calculées dans le système MnO-Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-FeO3 (MnNCKFMASHTO) avec le logiciel THERMOCALC, nous montrons que les échantillons ont enregistrés des chemins P-T horaires, dominés par une décompression entre S1 et S2. Les conditions P-T associées à S1 varient entre 5,4 kbar / 550°C et 8,5 kbar / 620°C, et représentent donc un gradient métamorphique de type barrovien. Les conditions P-T associées à la schistosité S2 évoluent entre 2,5 kbar / 550°C et 4 kbar / 700°C et sont caractéristiques des gradients de haute température / basse pression de type Abukuma. Dans notre interprétation, les deux épisodes tectonométamorphiques sont d'âge alpin. Le développement de la schistosité S1 résulte de l'épaississement crustal dû à la subduction Alpine entrainant le métamorphisme HP-BT dans les Bétiques (unité Alpujarides) et le Rif (unité des Sebtides). Le deuxième épisode est associé à l'amincissement crustal dû à l'étirement de la croûte dans un contexte d'extension arrière-arc Oligo-Miocène. Nous discuterons de l'amplitude de cet amincissement et nous le comparerons à celui observé dans les unités équivalentes des chaînes Bétiques

Structures et métamorphisme des péridotites de Béni Bousera et de leur encaissant (Rif interne, Maroc): Implications géodynamiques durant l'extension arrière-arc à l'Oligo-Miocène

National audienc

HKROC: an integrated front-end ASIC to readout photomultiplier tubes for the Hyper-Kamiokande experiment

International audienceThe HKROC ASIC was originally designed to readout the photomultiplier tubes (PMTs) for the Hyper-Kamiokande (HK) experiment. HKROC is a very innovative ASIC capable of readout a large number of channels satisfying stringent requirements in terms of noise, speed and dynamic range. Each HKROC channel features a low-noise preamplifier and shapers, a 10-bit successive approximation Analog-to-Digital Converter (SAR-ADC) (designed by AGH Krakow) for the charge measurement (up to 2500 pC) and a Time-to-Digital Converter (TDC) (designed by CEA IRFU group) for the Time-of-Arrival (ToA) measurement with 25 ps binning. HKROC is auto-triggered and includes all necessary ancillary services as bandgap circuit, PLL (Phase-locked loop) and threshold DACs (Digital to Analog Converters). This paper will describe the ASIC architecture and the experimental results of the first HKROC prototype received in January 2022

HKROC: an integrated front-end ASIC to readout photomultiplier tubes for the Hyper-Kamiokande experiment

International audienceThe HKROC ASIC was originally designed to readout the photomultiplier tubes (PMTs) for the Hyper-Kamiokande (HK) experiment. HKROC is a very innovative ASIC capable of readout a large number of channels satisfying stringent requirements in terms of noise, speed and dynamic range. Each HKROC channel features a low-noise preamplifier and shapers, a 10-bit successive approximation Analog-to-Digital Converter (SAR-ADC) (designed by AGH Krakow) for the charge measurement (up to 2500 pC) and a Time-to-Digital Converter (TDC) (designed by CEA IRFU group) for the Time-of-Arrival (ToA) measurement with 25 ps binning. HKROC is auto-triggered and includes all necessary ancillary services as bandgap circuit, PLL (Phase-locked loop) and threshold DACs (Digital to Analog Converters). This paper will describe the ASIC architecture and the experimental results of the first HKROC prototype received in January 2022

HKROC: an integrated front-end ASIC to readout photomultiplier tubes for the Hyper-Kamiokande experiment

The HKROC ASIC was originally designed to readout the photomultiplier tubes (PMTs) for the Hyper-Kamiokande (HK) experiment. HKROC is a very innovative ASIC capable of readout a large number of channels satisfying stringent requirements in terms of noise, speed and dynamic range. Each HKROC channel features a low-noise preamplifier and shapers, a 10-bit successive approximation Analog-to-Digital Converter (SAR-ADC) (designed by AGH Krakow) for the charge measurement (up to 2500 pC) and a Time-to-Digital Converter (TDC) (designed by CEA IRFU group) for the Time-of-Arrival (ToA) measurement with 25 ps binning. HKROC is auto-triggered and includes all necessary ancillary services as bandgap circuit, PLL (Phase-locked loop) and threshold DACs (Digital to Analog Converters). This paper will describe the ASIC architecture and the experimental results of the first HKROC prototype received in January 2022

HKROC: an integrated front-end ASIC to readout photomultiplier tubes for the Hyper-Kamiokande experiment

International audienceThe HKROC ASIC was originally designed to readout the photomultiplier tubes (PMTs) for the Hyper-Kamiokande (HK) experiment. HKROC is a very innovative ASIC capable of readout a large number of channels satisfying stringent requirements in terms of noise, speed and dynamic range. Each HKROC channel features a low-noise preamplifier and shapers, a 10-bit successive approximation Analog-to-Digital Converter (SAR-ADC) (designed by AGH Krakow) for the charge measurement (up to 2500 pC) and a Time-to-Digital Converter (TDC) (designed by CEA IRFU group) for the Time-of-Arrival (ToA) measurement with 25 ps binning. HKROC is auto-triggered and includes all necessary ancillary services as bandgap circuit, PLL (Phase-locked loop) and threshold DACs (Digital to Analog Converters). This paper will describe the ASIC architecture and the experimental results of the first HKROC prototype received in January 2022