Geochemistry of soil gas in the seismic fault zone produced by the Wenchuan Ms 8.0 earthquake, southwestern China

The spatio-temporal variations of soil gas in the seismic fault zone produced by the 12 May 2008 Wenchuan Ms 8.0 earthquake were investigated based on the field measurements of soil gas concentrations after the main shock. Concentrations of He, H2, CO2, CH4, O2, N2, Rn, and Hg in soil gas were measured in the field at eight short profiles across the seismic rupture zone in June and December 2008 and July 2009. Soil-gas concentrations of more than 800 sampling sites were obtained. The data showed that the magnitudes of the He and H2 anomalies of three surveys declined significantly with decreasing strength of the aftershocks with time. The maximum concentrations of He and H2 (40 and 279.4 ppm, respectively) were found in three replicates at the south part of the rupture zone close to the epicenter. The spatio-temporal variations of CO2, Rn, and Hg concentrations differed obviously between the north and south parts of the fault zone. The maximum He and H2 concentrations in Jun 2008 occurred near the parts of the rupture zone where vertical displacements were larger. The anomalies of He, H2, CO2, Rn, and Hg concentrations could be related to the variation in the regional stress field and the aftershock activity

2020 Clinical practice guidelines for Myocarditis in adults

Russian Society of Cardiology (RSC)With the participation: Eurasian Association of Therapists (EUAT), Society of Specialists in Heart Failure (OSSN), Russian Scientific Medical Society of Therapists (RNMOT), Russian Society of Pathologists, Russian Society of Radiologists and Radiologists (RSR)Endorsed by: Research and Practical Council of the Ministry of Health of the Russian Federatio

Deformation-enhanced diagenesis and bacterial proliferation in the Nankai accretionary prism

International audienceUnderstanding diagenetic reactions in accreted sediments is critical for establishing the balance of fluid sources and sinks in accretionary prisms, which is in turn important for assessing the fluid pressure field and the ability for faults to host seismic slip. For this reason, we studied diagenetic reactions in deformation bands (shear zones and veins) within deep mud sediments from the Nankai accretionary prism (SW Japan) drilled at site C0001 during IODP Expedition 315, by means of microscopic observation, X-ray diffraction, and major-trace element analyses. Deformation bands are not only more compacted than the host sediment, but are also enriched in framboidal pyrite, as observed under microscopy and confirmed by chalcophile element enrichments (Fe, S, Cu, As, Sb, Pb). In tandem, clays in deformation bands undergo a destabilization of smectite or illite/smectite mixed layers, and/or a slight crystallization of illite, which is matched by a correlated increase in B and Li compared to the host sediment. The two diagenetic reactions of sulfide precipitation and clay transformation are both explained by a combined action of sulfate-reducing and methanogen bacteria, which strongly suggests an increased activity of anaerobic microbial communities localized in deformation bands. This local bacterial proliferation was possibly enhanced by the liberation of hydrogen from strained phyllosilicates. We suggest that the proliferation of anoxic bacteria, boosted by deformation, may participate in the pore water freshening observed at depth in accretionary prisms. Deformation-enhanced metabolic reactions may also explain the illitization observed in major faults of accretionary prisms. Care is therefore needed before interpreting illitization, and other diagenetic reactions as well, as evidence of shear heating, as these might be biogenic instead of thermogenic

Data for: The Comoros archipelago: a right-lateral transform boundary between the Somalia and Lwandle plates

Structural data (including fault-slip data, extension fractures, dykes, and bedding stratifications) collected in the islands of Mayotte, Anjouan and Mohéli in 2018 and 2019.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Layered gabbros and peridotites from Piton des Neiges volcano, La Réunion Island

co-auteur étrangerInternational audienceWe conducted a petrological study of the layered gabbros and peridotites outcropping in the cirque of Salazie, combining field investigations, geochemistry, petrography and, mineralogy to constrain the magmatic evolution of Piton des Neiges volcano (La Réunion). Three new hectometer-long outcrops are reported here (Sites 1, 2 and 3) in addition to the gabbroic series (hereafter named Site 4) previously described in the literature. The Sites 1 and 2 are located in the upper parts of the Mât River and show dunite and wehrlite units with no apparent foliation, lineation, or layering. The Sites 3 and 4 are located in the lower parts of the river and are made of olivine-gabbro, gabbro and ferrogabbro units showing marked foliation and lineation, and abundant layering. The mean composition of primary phases varies between Sites 1–2 and Sites 3–4: Fo89.5 to Fo69.8 in olivine, Mg# of 90 to 69 in clinopyroxene, and Mg# of 44 to 0 in Cr-spinel, titanomagnetite and, ilmenite, respectively. Here we show that the layered gabbros and peridotites exposed at the four sites represent multiple levels of magma storage. Based on the results of previous gravimetric studies and a drill hole related to geothermal exploration, we propose that the gabbroic series belongs to a magmatic system predating the building of Piton des Neiges and centered underneath the cirque of Salazie. The high volume of erupted materials in the NE quadrant of the volcanic edifice, and the southward magmatic flow direction in the layered gabbros suggest that the initial eruptive center of Proto-Piton des Neiges was above the cirque of Salazie, ~3 km north of the present-day summit. The landscape of Piton des Neiges may have changed when its NE flank experienced a major lateral collapse, after complete solidification of the gabbroic bodies. The magmatic activity, then, shifted southward after the flank collapse. Finally, we suggest that peridotites outcrops are associated with the present-day Piton des Neiges