Große Störungszonen vor dem apulischen orogenen Indenter im internen Bereich des Westalpenbogens haben sowohl eine NW-SE Verkürzung als auch einen vertikalen Versatz akkommodiert. Diese Störungen deformieren auch Gesteine mit alpidischen Hochdruckparagenesen. Das Hauptziel des Vorhaben ist festzustellen, wie diese Störungszonen zur Exhumierung der Hochdruckgesteine in der Sesia Zone beigetragen haben. Das vorgesehene Arbeitsgebiet eignet sich besonders gut zur Untersuchung von transpressiver Tektonik bei der Exhumierung subduzierter kontinentaler Kruste. Um die Kinematik und thermobarometrische Geschichte der Exhumierung zu rekonstruieren, sieht unser Projekt eine Kombination von strukturgeologischer Feldarbeit und mikrostrukturellen, petrologischen und geochronologischen Laborarbeiten vor. Das vorgesehene Projekt soll zwei wissenschaftliche Mitarbeiter für die Durchführung von struktur-petrologischen und strukturgeochronologischen Studien beschäftigen.
Die Erforschung der Bildung und Entwicklung des Vitiaz-Kermadec Arc und Backarc-Systems gewinnt international zunehmend an Bedeutung. Während der Expedition SO-255 sollen daher umfassende Kartierungen und Hartgesteinsbeprobungen in diesem System durchgeführt werden. Übergeordnete Ziele von SO-255 VITIAZ sind (1) die Rekonstruktion der Bildung des Vitiaz-Kermadec-Arc-Systems); (2) die Rekonstruktion der geochemischen Entwicklung dieses Arc-Systems von seiner Bildung bis zur Aufspaltung; (3) die Charakterisierung zeitlicher, petrologischer und geochemischer Änderungen, die der Aufspaltung des Arc vorangegangen sind und diese begleiteten; und (4) die Rekonstruktion des Übergangs von der Aufspaltung des Arcs zur Bildung eines Backarc-Beckens. SO-255 VITIAZ umfasst vulkanologische, petrologische, geochemische, geochronologische und geophysikalische Arbeiten. Die wichtigsten Arbeitsschritte sind: (1) vorbereitende Arbeiten; (2) Beprobung magmatischer Gesteine sowie bathymetrische und geophysikalische Untersuchungen auf Schiffsexpedition SO-255; (3) Dünnschliffmikroskopie und Gesteinsaufbereitung für die Analytik; (4) Gesteinsanalytik und -Datierung sowie der Auswertung der dabei anfallenden Daten; (5) Prozessierung der bathymetrischen und geophysikalischen Daten; (6) Integration und Modellierung der Daten sowie Ausarbeitung von Modellen und Publikationen.
The island of Holsnøy is located in southwestern Norway. It is composed of metastable granulite facies lower crust that was subducted at 430 Ma when fluid infiltrated the region and reacted with large portions of the area to form eclogite facies shear zones. The eclogite facies assemblages contain garnet with granulite facies cores and eclogite facies fractures and rims. This dataset contains quantitative electron microprobe transects from garnets from four different eclogite facies samples. They are divided into two groups: rim profiles that run from the garnet rims toward the cores, and fracture profiles that run perpendicular to eclogite facies fractures. Some profiles have 5–10 µm spacing and were collected at 15 kV accelerating voltage whereas others have 1 µm spacing and were collected at 10 kV which reduced analytical convolution and facilitated higher spatial resolution of the profiles.
Ziel des Projektes ist die Rekonstruktion der magmatischen und tektonischen Entwicklung der Beringsee und ihrer Randbereiche während der letzten größer als 50 Mill. Jahre. Insbesondere sollen Prozesse, die die Initiation und Entwicklung von Subduktionssystemen kontrollieren sowie die Auswirkungen von Subduktionsvulkanismus auf die Umwelt untersucht werden. Die Erweiterung der Erkenntnisse über Subduktionsprozesse und ihre Auswirkungen(Vulkanausbrüche und Erdbeben) ist von grundlegender Bedeutung sowohl für die Klimaentwicklung als auch in Hinblick auf ihre möglichen gesellschaftlichen Folgen. Im Detail sollen Proben von magmatischen Gesteinen, die von den Chukotka und Beringia Kontinentalrändern, den westlichen Aleuten und der unter die Aleuten und Nordkamtschakta subduzierten Ozeankruste stammen, geochronologisch, petrologisch und geochemisch bearbeitet werden, um die Entwicklung der Subduktion in dieser Region besser zu verstehen. Die Ergebnisse von BERING werden zusammen mit Ergebnissen früherer Projekte in angrenzenden Gebieten (z. B. KOMEX und KALMAR) in die Untersuchungen der laufenden 'World Oceans' und 'GeoPRISMS' (Geodynamic Processes at Rifting and Subducting Margins) Programme integriert.
This data publication contains (i) a slab model of the Cascadia subduction zone, derived from receiver functions, parameterized as depth to the three interfaces: t (top), c (central) and m (Moho), in NetCDF format; (ii) the station measurements of all parameters in the model in tabular and Raysum model file format; (iii) the raw receiver functions in SAC format; and (iv) auxiliary scripts for loading and plotting the data. A total of 45,601 individual receiver functions recorded at 298 seismic stations distributed across the Cascadia forearc contributed to the slab model. For each station, 100 s recordings symmetric about the P -wave arrival (i.e. 50 s noise and 50 s signal) of earthquakes with magnitudes between 5.5 and 8, in the distance range between 30 and 100 degree, were downloaded from the Incorporated Research Institutions for Seismology (IRIS) data center, the Northern California Earthquake Data Center (NCEDC), and the Natural Resources Canada Data Center (NRCAN). After quality control, radial and transverse receiver functions were computed through frequency-domain simultaneous deconvolution, with an optimal damping factor found through generalized cross validation. The continental forearc and subducting slab were parameterized as three layers over a mantle half-space, with the subduction stratigraphy bounding interfaces labeled as t (top), c (central) and m (Moho). Synthetic receiver functions were calculated through ray-theoretical modeling of plane-wave scattering at the model interfaces. The thickness, S -wave velocity (VS) and P - to S -wave velocity ratio (VP/VS) of each layer, as well as the common strike and dip of the bottom two layers and the top of the half space (in total 11 parameters) were optimized simultaneously through a simulated annealing global parameter search scheme. The misfit was defined as the anti-correlation (1 minus the cross-correlation coefficient) between the observed and predicted receiver functions, bandpass filtered between 2 and 20 s period duration. In total, 171, 143 and 137 quality A nodes were determined to constrain the t, c and m interfaces, respectively. At the trench, 105 nodes at 3 km below the local bathymetry were inserted to constrain the t and c interfaces, and at 6.5 km deeper to constrain the m interface, representing typical sediment and igneous crustal thicknesses. A spline surface was fitted to these nodes to yield margin-wide depth models. The spline coefficients were found using singular value decomposition, with the nominal depth uncertainties supplied as weights. The solution was damped by retaining the 116, 117, and 116 largest singular values for the t, c and m interfaces, respectively, based on analysis of L-curves and the Akaike information criterion. The data set is the supplemental material to Bloch, W., Bostock, M. G., Audet, P. (2023) A Cascadia Slab Model from Receiver Functions. Geochemistry, Geophysics, Geosystems.
Raman spectroscopy of carbonaceous matter (RSCM) is commonly used to derive metamorphic peak- temperature estimates of metasedimentary rocks. This thermometry method exploits that the degree of graphitization of carbonateous matter (CM), which is measured via Raman spectroscopy, increases with metamorphic temperature. This dataset provides the raw data of RSCM, spectrum fitting results and calculated peak temperatures of more than 100 samples from the central Tauern Window. We used this data to constrain the distribution of metamorphic peak temperatures in this area. Raman analysis was performed on polished thin and thick sections. We exclusively measured grains of CM that were enclosed in translucent minerals (quartz, white mica, chlorite, carbonates, chloritoid, garnet) and therefore not exposed on the section surface, in order to avoid destruction of the CM during the sample preparation process. Raman spectra were acquired in the first-order region of graphite (ca. 1000-1900 cm^-1). Further details on the analytical setup, spectrum fitting and temperature calculation are provided in the following sections. The data is distributed in the form of simple text files and raster images.
The southern Central Andes (SCA, 29°S-39°S) are characterized by the subduction of the oceanic Nazca Plate beneath the continental South American Plate. One striking feature of this area is the change of the subduction angle of the Nazca Plate between 33°S and 35°S from the Chilean-Pampean flat-slab zone (< 5° dip) in the north to a steeper sector in the south (~30° dip). Subduction geometry, tectonic deformation, and seismicity at this plate boundary are closely related to the lithospheric strength in the upper plate. Despite recent research focused on the compositional and thermal characteristics of the SCA lithosphere, the lithospheric strength distribution remains largely unknown. Here we calculated the long-term lithospheric strength on the basis of an existing 3D model describing the variation of thickness, density and temperature of geological units forming the lithosphere of the SCA. The model consists of a continental plate with sediments, a two-layer crust and the lithospheric mantle being subducted by an oceanic plate. The model extension covers an area of 700 km x 1100 km, including the orogen (i.e. magmatic arc, main orogenic wedge), the forearc and the foreland, and it extents down to 200 km depth.
This supplement contains GNSS displacement time series, fluid loading displacement time series predictions, and trajectory models for these time series. The time series are for the study regions of the paper: "Months-Long thousand-km-scale wobbling before great subduction earthquakes". These study regions are (1) Japan and surrounding countries and (2) Chile and surrounding countries. Network solution daily GNSS time series displacements in Chile and surrounding countries in the South American network have been produced by GFZ. Network solution daily GNSS time series of displacements in Japan have been produced by the Geospatial Information Authority of Japan (GSI). PPP daily GNSS time series of displacements in Japan and surrounding countries have been produced by the Nevada Geodetic Laboratory, Nevada Bureau of Mines and Geology, University of Nevada, Reno. Fluid loading predictions have been made using the HYDL, NTOL, NTAL, and SLEL products of the ESMGFZ. Readme ascii files in this data supplement contain instructions on how the data are ordered. Furthermore, the Readme file contains the relevant references and acknowledgments for readers who want to use these data in their own published studies.
The Central Andes (~21°S) is a subduction-type orogeny formed in the last ~50 Ma from the subduction of the Nazca oceanic plate beneath the South American continental plate. However, the most important phases of deformation occur in the last 20 Ma. Pulses of shortening have led to the sudden growth of the by the Altiplano-Puna plateau. Previous studies have provided insights on the importance of various mechanisms on the overall shortening such as the weakening of the overriding plate from crustal eclogitization and delamination, or the importance of a relatively high friction at the subduction interface, and weak sediments in foreland. However none of them has addressed the mechanism behind these shortening pulses yet. Therefore, we built a series of high resolution 2D visco-plastic subduction models using the ASPECT geodynamic code, in which the oceanic plate is buoyancy-driven and the velocity of the continent is prescribed. We have also implemented a realistic geometry for the south American plate at ~30 Ma. We propose a new plausible mechanism (buckling and steepening of the slab) as the cause of these pulses. The buckling leads to the blockage of the trench. Consequently, the difference of velocity between the South American plate and the trench is accommodated by shortening. The data presented here includes the parameters files, for the reference model (S1) and the following alternative simulations: models with variation of the friction at the subduction interface (S2a-c), a model without eclogitization of the lower crust (S3) and a model with higher thermal conductivity of the upper crust (S4). Additionally, this publication includes the initial composition and thermal state of the lithosphere used for the models and a Readme file that gives all the instructions to run them.
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