Water pumping in mantle shear zones: From field observations to experimental evidence

International audienceWater plays an important role in geological processes. Providing constraints on what may influence the distribution of aqueous fluids is thus crucial to understanding how H2O impacts Earth's geodynamics. In a deep-seated environment, viscous shear zones have been identified as sites of massive fluid circulation, with many implications for ores deposits and rock rheology. However, although seismic pumping, fluid permeation and/or creep cavitation have been proposed as important processes, the source mechanism of such a fluid concentration remains unresolved. In this contribution based on both field and experimental data, we demonstrate that viscous flow exerts a dynamic control on H2O-rich fluid circulation in mantle shear zones. Using the distributions of amphibole and olivine dislocation slip-systems, we first highlight H2O accumulation around fine-grained shear zones in the Ronda peridotite massif (Spain). These observations give rise to a long-term and continuous process of fluid pumping during ductile deformation, which strongly suggest creep cavitation as the driving mechanism. Secondly, we used secondary ion mass spectrometry to document the H2O content of fine-grained olivine across an experimental shear zone. The latter developed with grain size reduction during a H2O-saturated shear experiment at 1.2 GPa and 900 °C. Through data interpolation, the olivine matrix reveals high H2O concentrations where shear strain is localized. These concentrations far exceed the predicted amount of H2O that grain boundaries can contain, excluding diffusive fluid permeation as a unique source of water storage. We also show that the H2O content increases per unit of grain boundary across the shear zone, highlighting an excess volume of H2O that depends on strain and/or strain rate. Based on tensile experiments in metals, we propose that a larger pore volume is produced with increasing strain rate due to competition between creep cavitation and "healing" processes, which include phase nucleation. Altogether, our findings therefore support creep cavitation to occur in mantle shear zones, providing a dynamic process for H2O to be infiltrated and stored in the deep lithosphere

Water pumping in mantle shear zones: From field observations to experimental evidence

International audienceWater plays an important role in geological processes. Providing constraints on what may influence the distribution of aqueous fluids is thus crucial to understanding how H2O impacts Earth's geodynamics. In a deep-seated environment, viscous shear zones have been identified as sites of massive fluid circulation, with many implications for ores deposits and rock rheology. However, although seismic pumping, fluid permeation and/or creep cavitation have been proposed as important processes, the source mechanism of such a fluid concentration remains unresolved. In this contribution based on both field and experimental data, we demonstrate that viscous flow exerts a dynamic control on H2O-rich fluid circulation in mantle shear zones. Using the distributions of amphibole and olivine dislocation slip-systems, we first highlight H2O accumulation around fine-grained shear zones in the Ronda peridotite massif (Spain). These observations give rise to a long-term and continuous process of fluid pumping during ductile deformation, which strongly suggest creep cavitation as the driving mechanism. Secondly, we used secondary ion mass spectrometry to document the H2O content of fine-grained olivine across an experimental shear zone. The latter developed with grain size reduction during a H2O-saturated shear experiment at 1.2 GPa and 900 °C. Through data interpolation, the olivine matrix reveals high H2O concentrations where shear strain is localized. These concentrations far exceed the predicted amount of H2O that grain boundaries can contain, excluding diffusive fluid permeation as a unique source of water storage. We also show that the H2O content increases per unit of grain boundary across the shear zone, highlighting an excess volume of H2O that depends on strain and/or strain rate. Based on tensile experiments in metals, we propose that a larger pore volume is produced with increasing strain rate due to competition between creep cavitation and "healing" processes, which include phase nucleation. Altogether, our findings therefore support creep cavitation to occur in mantle shear zones, providing a dynamic process for H2O to be infiltrated and stored in the deep lithosphere

Does mechanical morcellation of large glands compromise incidental prostate cancer detection on specimen analysis? A pathological comparison with open simple prostatectomy

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Bridge The Distance Between Breast Pathologists: When The Senopath Network Opens Up To The Telepathology

Introduction/ Background In clinical practice, pathologists commonly face breast lesions, which are difficult to diagnose and which re- quire discussion. In Midi-Pyrénées, the largest region ofFrance, this problem has led us to develop in 2011 a peer group for breast diseases entitled SENOPATH. Aims In order to reduce second opinion delay, erase geographical barrier and provide continuing education, we aimed to introduce an effective online and outline telepathology system in the SENOPATH network. Methods A case review by SENOPATH can be requested by any pathologist in the Midi-Pyrénées region, by filling a form through the ONCOMIP network (organization dedicated to oncology in the Midi- Pyrénées region). The slides are sent for digitalization at The University Cancer Institute - Oncopole, using a Hamamatsu 2.0-RS scanner (until 2014) and a 3DHISTECH Pannoramic 250 scanner, then anonymized and transferred to a shared storage space at Toulouse Paul Sabatier University. Virtual slides can be seen before and/or after the meeting by members of the group by login in the online 3DHISTECHCaseCentervia the Imag’IN platform website. The group, who meets on a monthly basis, has recently developed a synchronized webinar  (using 3DHISTECH Case Center and Pannoramic Viewer) coupled with a conference call in order to ease the attendance of pathologists from remote pathology laboratories. A consensual diagnosis and final pathology report are issued for each case and sent to the referent clinician via the patient medical file securely hosted by ONCOMIP. Results From January 2012 to December 2015, 211 cases (39 in 2012, 50 in 2013, 75 in 2014 and 47 in 2015) have been reviewed during 43 meetings. Ten out of 43 meetings (23%) used telepathology. Sixty-one cases out of 211 (29%) were actually digitalized, mainly using theHamamatsu2.0-RS scanner. In average, the number of attending pathologists was9 to 10from 2012 to 2015. The average number of cases reviewed per meeting was 3 in 2012 and 5 between 2013 and 2015. Two main motives for review were identified: diagnostic ‘routine difficulty’ (equivocal or discordant cases, invasive vs in situ lesion, atypical vs malignant lesions, immunohistochemistry scoring pitfalls) or rare tumours. The rare tumour category included among others syringomatous tumour of the nipple, low-grade adenosquamous, myoepithelial, mucoepidermoid or secretory carcinomas, adenomyoepithelioma, atypical microglandular adenosis, sclerosing papillary hyperplasia without myoepithelium and periductal stromal tumour. Molecular analyses requested by the group and implemented in the diagnosis process mainly included immunohistochemistry and fluorescence in situ hybridization (HER2, ETV6, MAML2, MYB). The SENOPATH network committee review for difficult or rare lesions of the breast has considerably improved the pathologist’s network in our region. This working group is regularly requested by oncologists to solve difficult cases. Our aims for the next few years are 1/ to digitalize all of the cases reviewed by the SENOPATH network, 2/ to use telepathology facilities provided by the Imag’IN platform in order to widen the group to a national level, and 3/ to construct a growing online library of virtual slides for breast challenging lesions.