IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Trachyte Phase Relations and Implication for Magma Storage Conditions in the Chaîne des Puys (French Massif Central)

Abstract: Petrological data have been acquired on the natural trachytes from the Chaine des Puys, French Massif Central, and on experimental products from phase equilibria in order to (i) constrain the storage conditions of the trachytic magmas that lead to explosive eruptions (dome destructions as block-and-ash flows or pumice-and-ash flows) and (ii) provide phase relationships and chemical compositions for differentiated alkaline liquids in intraplate continental context. Phase assemblages, proportions, and compositions have been determined on six trachytes with SiO2 contents varying from 62 to 69 wt % and alkali contents of 10.5-12.0 wt %. The samples contain up to 30 % of phenocrysts, mainly consisting of feldspar (15-17 %; plagioclase and/or alkali-feldspar), biotite (2-6 %; except in the SiO2-poorest sample), Fe-Ti oxides (1-3 %) ± amphibole (< 5 %), ± clinopyroxene (~1 %). All samples have apatite and zircon as minor phases and titanite has been found in one sample. Pristine glasses (melt inclusions or residual glasses) in pumice from explosive events are trachytic to rhyolitic (65-73 wt % SiO2 and 10.5-13.0 wt % alkali). H2O dissolved in melt inclusions and the biotite+alkali feldspar+magnetite hygrobarometer both suggest pre-eruptive H2O contents up to 8 wt %. These are so far the highest H2O contents ever reported for alkaline liquids in an intraplate continental context. Melt inclusions also contain ~3400 ppm chlorine, ~700 ppm fluorine, and ~300 ppm sulphur. Crystallisation experiments of the six trachytes have been performed between 200 and 400 MPa, 700 and 900°C, H2O saturation, and oxygen fugacity of NNO +1. The comparison between the natural and experimental phase assemblage, proportion, and composition suggests magma storage conditions at a pressure of 300-350 MPa (~10-12 km deep), melt H2O content ~8 wt % (close to saturation), an oxygen fugacity close to NNO~0.5, and temperatures increasing from 700 to 825°C with decreasing bulk SiO2 of the trachyte. The high H2O contents of the trachytes show that wet conditions may prevail during the differentiation of continental alkaline series. Regardless of the size of the magma reservoir assumed to have fed the trachyte eruptions, calculation of the thermal relaxation timescales indicates that the tapped reservoir(s) are likely to be still partially molten nowadays. The four northernmost edifices may correspond to a single large reservoir with a lateral extension of up to 10 km, which could be possibly reactivated in weeks to months if intercepted by new rising basalt batches.

Source tomography by simulated annealing using broad‐band surface waves and geodetic data: application to the Mw= 8.1 Chile 1995 event

Abstract: SUMMARY We invert surface-wave and geodetic data for the spatio-temporal complexity of slip during the Mw=8.1 Chile 1995 event by simulated annealing. This quasi-global inversion method allows for a wide exploration of model space, and retains the non-linearity of the source tomography problem. Complex source spectra are obtained from 5 to 45 mHz from first- and second-orbit fundamental-mode Rayleigh waves using an empirical Green's function cross-correlation technique. Coseismic displacement vectors were measured at 10 GPS sites near Antofagasta. They are part of a French-Chilean experiment which monitors the Northern Chile seismic gap. The spectra, together with the geodetic data, are inverted for the moment distribution on a 2-D dipping fault, under the physical constraints of slip positivity and causality. Marginal a posteriori distributions of the model parameters are obtained from several independently inverted solutions. In general, features of the slip model are well resolved. Data are well fitted by a purely unilateral southward rupture with a nearly uniform velocity around 2.5–3.0 km s−1, and a total duration of 65 s. Several regions of moment release were imaged, one near the hypocentre, a major one 80 km south of it and a minor one 160 km south of it. The major patch of moment release seemed to have propagated to relatively shallow depths near the trench, 100 km SSW of the epicentre. The region of major slip is located updip of the 1987, Mw=7.5 earthquake, suggesting a causal relationship. Most of the slip occurred updip of the hypocentre (36 km), but the entire coupled plate interface (20–40 km) ruptured during the Chile 1995 event.

Double origin of hydrothermal convective flux variations in the Fossa of Vulcano (Italy)

Abstract: Soil-temperature measurements can provide information on the distribution of degassing fissures, their relationship to the internal structure of the volcano, and the temporal evolution of the system. At Vulcano Island (Italy), heat flux from a <3 km-deep magma body drives a hydrothermal system which extends across the main Fossa crater. This heat flux is also associated with variable magmatic gas flow. A high-density map of soil-temperatures was made in 1996 at a constant depth of 30 cm on the central and southern inner flanks of the Fossa crater. These measurements extended over an area covering about 0.04 km2, across which the heat flux is predominantly associated with a shallow boiling aquifer. The map shows that hot zones relate to structures of higher permeability, mainly associated with a fissure system dating from the last eruptive cycle (1888–1890). From 1996 to January 2005, we studied the evolution of the heat flux for the high temperature part of the map, both by repeating our measurements as part of 14 visits, during which temperatures were measured at a constant depth, and using data from permanent stations which allowed soil-temperatures to be continuously measured for selected vertical profiles. These data allowed us to calculate the heat flux, and its variation, with good precision for values lower than about 100 W m−2, which is generally the case in the study area. Above 100 W m−2, although the heat flux value is underestimated, its variations are recorded with an error less than 10%. During the period 1996–2004, two increases in the thermal flux were recorded. The first one was related to the seismic crisis of November 1998 which opened existing or new fissures. The second, in November 2004, was probably due to magma migration, and was associated with minor seismic activity.