TY - JOUR A1 - Kutzschbach, Martin A1 - Wunder, Bernd A1 - Wannhoff, Iris A1 - Wilke, Franziska Daniela Helena A1 - Couffignal, Frédéric A1 - Rocholl, Alexander T1 - Raman spectroscopic quantification of tetrahedral boron in synthetic aluminum-rich tourmaline JF - American mineralogist : an international journal of earth and planetary materials N2 - The Raman spectra of five B-[4]-bearing tourmalines of different composition synthesized at 700 degrees C/4.0 GPa (including first-time synthesis of Na-Li-B-[4]-tourmaline, Ca-Li-B-[4]-tourmaline, and Ca-bearing square-B-[4]-tourmaline) reveal a strong correlation between the tetrahedral boron content and the summed relative intensity of all OH-stretching bands between 3300-3430 cm(-1). The band shift to low wavenumbers is explained by strong O3-H center dot center dot center dot O5 hydrogen bridge bonding. Applying the regression equation to natural B-[4]-bearing tourmaline from the Koralpe (Austria) reproduces the EMPA-derived value perfectly [EMPA: 0.67(12) B-[4] pfu vs. Raman: 0.66(13) B-[4] pfu]. This demonstrates that Raman spectroscopy provides a fast and easy-to-use tool for the quantification of tetrahedral boron in tourmaline. The knowledge of the amount of tetrahedral boron in tourmaline has important implications for the better understanding and modeling of B-isotope fractionation between tourmaline and fluid/melt, widely used as a tracer of mass transfer processes. KW - Tourmaline KW - high pressure KW - synthesis KW - tetrahedral boron KW - Raman KW - SIMS KW - Lithium KW - Beryllium and Boron: Quintessentially Crustal Y1 - 2021 U6 - https://doi.org/10.2138/am-2021-7758 SN - 0003-004X SN - 1945-3027 VL - 106 IS - 6 SP - 872 EP - 882 PB - Mineralogical Society of America CY - Washington, DC [u.a.] ER - TY - JOUR A1 - Farkas, Márton Pál A1 - Hofmann, Hannes A1 - Zimmermann, Günter A1 - Zang, Arno A1 - Bethmann, Falko A1 - Meier, Peter A1 - Cottrell, Mark A1 - Josephson, Neal T1 - Hydromechanical analysis of the second hydraulic stimulation in well PX-1 at the Pohang fractured geothermal reservoir, South Korea JF - Geothermics : an international journal of geothermal research and its applications N2 - In this study, we investigate numerically the hydro-mechanical behavior of fractured crystalline rock due to one of the five hydraulic stimulations at the Pohang Enhanced Geothermal site in South Korea. We use the commercial code FracMan (Golder Associates) that enables studying hydro-mechanical coupled processes in fractured media in three dimensions combining the finite element method with a discrete fracture network. The software is used to simulate fluid pressure perturbation at fractures during hydraulic stimulation. Our numerical simulation shows that pressure history matching can be obtained by partitioning the treatment into separate phases. This results in adjusted stress-aperture relationships. The evolution of aperture adjustment implies that the stimulation mechanism could be a combination of hydraulic fracturing and shearing. The simulated extent of the 0.01 MPa overpressure contour at the end of the treatment equals to similar to 180 m around the injection point. KW - Enhanced Geothermal System KW - Pohang geothermal reservoir KW - hydraulic KW - stimulation KW - PX-1 KW - FracMan Y1 - 2021 U6 - https://doi.org/10.1016/j.geothermics.2020.101990 SN - 0375-6505 SN - 1879-3576 VL - 89 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Licht, Alexis A1 - Kelson, Julia A1 - Bergel, Shelly J. A1 - Schauer, Andrew J. A1 - Petersen, Sierra Victoria A1 - Capirala, Ashika A1 - Huntington, Katharine W. A1 - Dupont-Nivet, Guillaume A1 - Win, Zaw A1 - Aung, Day Wa T1 - Dynamics of pedogenic carbonate growth in the tropical domain of Myanmar JF - Geochemistry, geophysics, geosystems N2 - Pedogenic carbonate is widespread at mid latitudes where warm and dry conditions favor soil carbonate growth from spring to fall. The mechanisms and timing of pedogenic carbonate formation are more ambiguous in the tropical domain, where long periods of soil water saturation and high soil respiration enhance calcite dissolution. This paper provides stable carbon, oxygen and clumped isotope values from Quaternary and Miocene pedogenic carbonates in the tropical domain of Myanmar, in areas characterized by warm (>18°C) winters and annual rainfall up to 1,700 mm. We show that carbonate growth in Myanmar is delayed to the driest and coldest months of the year by sustained monsoonal rainfall from mid spring to late fall. The range of isotopic variability in Quaternary pedogenic carbonates can be solely explained by temporal changes of carbonate growth within the dry season, from winter to early spring. We propose that high soil moisture year-round in the tropical domain narrows carbonate growth to the driest months and makes it particularly sensitive to the seasonal distribution of rainfall. This sensitivity is also enabled by high winter temperatures, allowing carbonate growth to occur outside the warmest months of the year. This high sensitivity is expected to be more prominent in the geological record during times with higher temperatures and greater expansion of the tropical realm. Clumped isotope temperatures, δ13C and δ18O values of tropical pedogenic carbonates are impacted by changes of both rainfall seasonality and surface temperatures; this sensitivity can potentially be used to track past tropical rainfall distribution. KW - clumped isotopes KW - pedogenic carbonate KW - monsoon Y1 - 2022 U6 - https://doi.org/10.1029/2021GC009929 SN - 1525-2027 VL - 23 IS - 7 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Sharma, Shubham A1 - Hainzl, Sebastian A1 - Zöller, Gert T1 - Seismicity parameters dependence on main shock-induced co-seismic stress JF - Geophysical journal international N2 - The Gutenberg-Richter (GR) and the Omori-Utsu (OU) law describe the earthquakes' energy release and temporal clustering and are thus of great importance for seismic hazard assessment. Motivated by experimental results, which indicate stress-dependent parameters, we consider a combined global data set of 127 main shock-aftershock sequences and perform a systematic study of the relationship between main shock-induced stress changes and associated seismicity patterns. For this purpose, we calculate space-dependent Coulomb Stress (& UDelta;CFS) and alternative receiver-independent stress metrics in the surrounding of the main shocks. Our results indicate a clear positive correlation between the GR b-value and the induced stress, contrasting expectations from laboratory experiments and suggesting a crucial role of structural heterogeneity and strength variations. Furthermore, we demonstrate that the aftershock productivity increases nonlinearly with stress, while the OU parameters c and p systematically decrease for increasing stress changes. Our partly unexpected findings can have an important impact on future estimations of the aftershock hazard. KW - earthquake hazards KW - earthquake interaction KW - forecasting and prediction KW - statistical seismology KW - b-value Y1 - 2023 U6 - https://doi.org/10.1093/gji/ggad201 SN - 0956-540X SN - 1365-246X VL - 235 IS - 1 SP - 509 EP - 517 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Dutta, Rishabh A1 - Jónsson, Sigurjón A1 - Vasyura-Bathke, Hannes T1 - Simultaneous Bayesian estimation of non-planar fault geometry and spatially-variable slip JF - JGR / AGU, American Geophysical Union : Solid earth N2 - Large earthquakes are usually modeled with simple planar fault surfaces or a combination of several planar fault segments. However, in general, earthquakes occur on faults that are non-planar and exhibit significant geometrical variations in both the along-strike and down-dip directions at all spatial scales. Mapping of surface fault ruptures and high-resolution geodetic observations are increasingly revealing complex fault geometries near the surface and accurate locations of aftershocks often indicate geometrical complexities at depth. With better geodetic data and observations of fault ruptures, more details of complex fault geometries can be estimated resulting in more realistic fault models of large earthquakes. To address this topic, we here parametrize non-planar fault geometries with a set of polynomial parameters that allow for both along-strike and down-dip variations in the fault geometry. Our methodology uses Bayesian inference to estimate the non-planar fault parameters from geodetic data, yielding an ensemble of plausible models that characterize the uncertainties of the non-planar fault geometry and the fault slip. The method is demonstrated using synthetic tests considering slip spatially distributed on a single continuous finite non-planar fault surface with varying dip and strike angles both in the down-dip and along-strike directions. The results show that fault-slip estimations can be biased when a simple planar fault geometry is assumed in presence of significant non-planar geometrical variations. Our method can help to model earthquake fault sources in a more realistic way and may be extended to include multiple non-planar fault segments or other geometrical fault complexities. KW - non-planar fault geometry KW - Bayesian estimation KW - InSAR and GNSS KW - source modeling Y1 - 2021 U6 - https://doi.org/10.1029/2020JB020441 SN - 2169-9313 SN - 2169-9356 VL - 126 IS - 7 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Blanke, Aglaja A1 - Kwiatek, Grzegorz A1 - Goebel, Thomas H. W. A1 - Bohnhoff, Marco A1 - Dresen, Georg T1 - Stress drop-magnitude dependence of acoustic emissions during laboratory stick-slip JF - Geophysical journal international / the Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society N2 - Earthquake source parameters such as seismic stress drop and corner frequency are observed to vary widely, leading to persistent discussion on potential scaling of stress drop and event size. Physical mechanisms that govern stress drop variations arc difficult to evaluate in nature and are more readily studied in controlled laboratory experiments. We perform two stick-slip experiments on fractured (rough) and cut (smooth) Westerly granite samples to explore fault roughness effects on acoustic emission (AE) source parameters. We separate large stick-slip events that generally saturate the seismic recording system from populations of smaller AE events which are sensitive to fault stresses prior to slip. AE event populations show many similarities to natural seismicity and may be interpreted as laboratory equivalent of natural microseismic events. We then compare the temporal evolution of mechanical data such as measured stress release during slip to temporal changes in stress drops derived from Alis using the spectral ratio technique. We report on two primary observations: (1) In contrast to most case studies for natural earthquakes, we observe a strong increase in seismic stress drop with AE size. (2) The scaling of stress drop with magnitude is governed by fault roughness, whereby the rough fault shows a more rapid increase of the stress drop magnitude relation with progressing large stick-slip events than the smooth fault. The overall range of AE sizes on the rough surface is influenced by both the average grain size and the width of the fault core. The magnitudes of the smallest AE events on smooth faults may also be governed by grain size. However, AEs significantly grow beyond peak roughness and the width of the fault core. Our laboratory tests highlight that source parameters vary substantially in the presence of fault zone heterogeneity (i.e. roughness and narrow grain size distribution), which may affect seismic energy partitioning and static stress drops of small and large AE events. KW - Acoustic properties KW - Body waves KW - Earthquake dynamics KW - Earthquake source observations KW - Dynamics and mechanics of faulting Y1 - 2021 U6 - https://doi.org/10.1093/gji/ggaa524 SN - 0956-540X SN - 1365-246X VL - 224 IS - 2 SP - 1372 EP - 1381 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Najman, Yani A1 - Sobel, Edward A1 - Millar, Ian A1 - Luan, Xiwu A1 - Zapata, Sebastian A1 - Garzanti, Eduardo A1 - Parra, Mauricio A1 - Vezzoli, Giovanni A1 - Zhang, Peng A1 - Wa Aung, Day A1 - Paw, Saw Mu Tha Lay A1 - Lwin, Thae Naung T1 - The timing of collision between Asia and the West Burma Terrane, and the development of the Indo-Burman Ranges JF - Tectonics N2 - The West Burma Terrane (WBT) is a small terrane bounded to the east by the Asian Sibumasu Block and to the west by the Indo-Burman Ranges (IBR), the latter being an exhumed accretionary prism that formed during subduction of Indian oceanic lithosphere beneath Asia. Understanding the geological history of the WBT is important for reconstruction of the closure history of the Tethys Ocean and India-Asia collision. Currently there are major discrepancies in the proposed timings of collision between the WBT with both India and Asia; whether the WBT collided with India or Asia first is debated, and proposed timings of collisions stretch from the Mesozoic to the Cenozoic. We undertook a multi-technique provenance study involving petrography, detrital zircon U-Pb and Hf analyses, rutile U-Pb analyses and Sr-Nd bulk rock analyses on sediments of the Central Myanmar Basins of the WBT. We determined that the first arrival of Asian material into the basin occurred after the earliest late Eocene and by the early Oligocene, thus placing a minimum constraint on the timing of WBT-Asia collision. Our low temperature thermochronological study of the IBR records two periods of exhumation, in the early-middle Eocene, and at the Oligo-Miocene boundary. The Eocene event may be associated with the collision of the WBT with India. The later event at the Oligo-Miocene boundary may be associated with changes in wedge dynamics resulting from increased sediment supply to the system; however a number of other possible causes provide equally plausible explanations for both events. KW - Central Myanmar Basin KW - Indo-Burman Ranges KW - low temperature thermochronology KW - detrital provenance KW - West Burma Terrane Y1 - 2022 U6 - https://doi.org/10.1029/2021TC007057 SN - 0278-7407 SN - 1944-9194 VL - 41 IS - 7 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Toumoulin, Agathe A1 - Tardif-Becquet, Delphine A1 - Donnadieu, Yannick A1 - Licht, Alexis A1 - Ladant, Jean-Baptiste A1 - Kunzmann, Lutz A1 - Dupont-Nivet, Guillaume T1 - Evolution of continental temperature seasonality from the Eocene greenhouse to the Oligocene icehouse BT - a model-data comparison JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - At the junction of greenhouse and icehouse climate states, the Eocene-Oligocene Transition (EOT) is a key moment in Cenozoic climate history. While it is associated with severe extinctions and biodiversity turnovers on land, the role of terrestrial climate evolution remains poorly resolved, especially the associated changes in seasonality. Some paleobotanical and geochemical continental records in parts of the Northern Hemisphere suggest the EOT is associated with a marked cooling in winter, leading to the development of more pronounced seasons (i.e., an increase in the mean annual range of temperature, MATR). However, the MATR increase has been barely studied by climate models and large uncertainties remain on its origin, geographical extent and impact. In order to better understand and describe temperature seasonality changes between the middle Eocene and the early Oligocene, we use the Earth system model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO(2) decrease (1120, 840 and 560 ppm), the Antarctic ice-sheet (AIS) formation and the associated sea-level decrease. Our simulations suggest that pCO(2) lowering alone is not sufficient to explain the seasonality evolution described by the data through the EOT but rather that the combined effects of pCO(2) , AIS formation and increased continentality provide the best data-model agreement.pCO(2) decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands particularly strong in the northern high latitudes (up to 8 degrees C MATR increase) due to sea-ice and surface albedo feedback. Conversely, the onset of the AIS is responsible for a more constant surface albedo yearly, which leads to a strong decrease in seasonality in the southern midlatitudes to high latitudes (> 40 degrees S). Finally, continental areas that emerged due to the sea-level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes (1MATR) patterns. The Delta MATR patterns we reconstruct are generally consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere and provide insights on their underlying mechanisms. Y1 - 2022 U6 - https://doi.org/10.5194/cp-18-341-2022 SN - 1814-9324 SN - 1814-9332 VL - 18 IS - 2 SP - 341 EP - 362 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Smith, Taylor A1 - Boers, Niklas T1 - Global vegetation resilience linked to water availability and variability JF - Nature Communications N2 - Quantifying the resilience of vegetated ecosystems is key to constraining both present-day and future global impacts of anthropogenic climate change. Here we apply both empirical and theoretical resilience metrics to remotely-sensed vegetation data in order to examine the role of water availability and variability in controlling vegetation resilience at the global scale. We find a concise global relationship where vegetation resilience is greater in regions with higher water availability. We also reveal that resilience is lower in regions with more pronounced inter-annual precipitation variability, but find less concise relationships between vegetation resilience and intra-annual precipitation variability. Our results thus imply that the resilience of vegetation responds differently to water deficits at varying time scales. In view of projected increases in precipitation variability, our findings highlight the risk of ecosystem degradation under ongoing climate change. Vegetation dynamics depend on both the amount of precipitation and its variability over time. Here, the authors show that vegetation resilience is greater where water availability is higher and where precipitation is more stable from year to year. Y1 - 2023 U6 - https://doi.org/10.1038/s41467-023-36207-7 SN - 2041-1723 VL - 14 IS - 1 PB - Springer Nature CY - London ER - TY - JOUR A1 - Repasch, Marisa A1 - Scheingross, Joel S. A1 - Hovius, Niels A1 - Vieth-Hillebrand, Andrea A1 - Mueller, Carsten W. A1 - Höschen, Carmen A1 - Szupiany, Ricardo N. A1 - Sachse, Dirk T1 - River organic carbon fluxes modulated by hydrodynamic sorting of particulate organic matter JF - Geophysical research letters N2 - Rivers regulate the global carbon cycle by transferring particulate organic carbon (POC) from terrestrial landscapes to marine sedimentary basins, but the processes controlling the amount and composition of fluvially exported POC are poorly understood. We propose that hydrodynamic sorting processes modify POC fluxes during fluvial transit. We test this hypothesis by studying POC transported along a similar to 1,200 km reach of the Rio Bermejo, Argentina. Nanoscale secondary ion mass spectrometry revealed that POC was either fine, mineral-associated organic matter, or coarse discrete organic particles. Mineral-associated POC is more resistant to oxidation and has a lower particle settling velocity than discrete POC. Consequently, hydraulic sorting and downstream fining amplify the proportion of fine, mineral-associated POC from similar to 55% to similar to 78% over 1,220 km of downstream transit. This suggests that mineral-associated POC has a greater probability of export and preservation in marine basins than plant detritus, which may be oxidized to CO2 during transit. KW - compound-specific stable isotopes KW - carbon fluxes KW - rivers KW - NanoSIMS; KW - sediment transport KW - hydrodynamic sorting Y1 - 2022 U6 - https://doi.org/10.1029/2021GL096343 SN - 0094-8276 SN - 1944-8007 VL - 49 IS - 3 PB - American Geophysical Union CY - Washington ER -