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Crystal structure of methoxo-oxo[benzoylaceton-salicyl hydrazonato(2-)]vanadium(V), C18H17N2O5V
(1996)
Solution and refinement of the crystal structure of fac-Ir(ppy)(3) is severely hampered by systematic twinning and pseudo-symmetry.fac-Ir(ppy)(3) Crystallizes in the centrosymmetric space group P (3) over bar as has been deduced from single-crystal structure refinement and investigations of the second harmonic generation (SHG) of fac-Ir(ppy)(3) powder as compared to two standard materials. The topology of the molecular packing of fac-Ir(ppy)(3) is identical to the packing observed for [Ru(bpy)(3)](0), however, the site symmetry of all Ir(ppy)(3) molecules is necessarily lowered from D-3 to C-3. Packing motifs with intermolecular "pi-pi interactions" of T-shaped and "shifted pi stack" geometry are realized. The systematic twinning leads to the occurrence of crystalline domains with rigorously alternating chirality within the bulk of the domains but with homochiral fac-Ir(ppy)(3) contacts at the domain interfaces. These differences in packing motifs are displayed in the emission spectra and in the high-pressure-induced shifts of the emission. The emission maximum of the bulk material at 18 350 cm(-1) (545 nm) and of the domain interfaces at 19 700 cm-1 (507 nm) experience for p < 25 kbar and T = 295 K red shifts of Delta nu/Delta p = -(12 +/- 2) cm(-1)/kbar, and -(22 +/- 4) cm(- 1)/kbar, respectively
Bacteriophage HK620 infects Escherichia coli H and is closely related to Shigella phage Sf6 and Salmonella phage P22. All three Podoviridae recognize and cleave their respective host cell receptor polysaccharide by homotrimeric tailspike proteins. The three proteins exhibit high sequence identity in the 110 residues of their N-terminal particle- binding domains, but no apparent sequence similarity in their major, receptor-binding parts. We have biochemically characterized the receptor-binding part of HK620 tailspike and determined its crystal structure to 1.38 Å resolution. Its major domain is a right-handed parallel ;-helix, as in Sf6 and P22 tailspikes. HK620 tailspike has endo-N- acetylglucosaminidase activity and produces hexasaccharides of an O18A1-type O-antigen. As indicated by the structure of a hexasaccharide complex determined at 1.6 Å resolution, the endoglycosidase-active sites are located intramolecularly, as in P22, and not between subunits, as in Sf6 tailspike. In contrast, the extreme C-terminal domain of HK620 tailspike forms a ;-sandwich, as in Sf6 and unlike P22 tailspike. Despite the different folds, structure-based sequence alignments of the C-termini reveal motifs conserved between the three proteins. We propose that the tailspike genes of P22, Sf6 and HK620 have a common precursor and are not mosaics of unrelated gene fragments.
The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a, 2,3,5a, 7,8,8a, 9,10,10a-decahydro-3-hydroxy-4,10a-dimethyl-8-methylidene-7-oxooxireno[5,6] cyclodeca[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P2(1)2(1)2(1), and its molecular structure consists of a methacrylic ester of a ten-membered ring sesquiterpenoid annelated with an epoxide and a butyrolactone. The structure is stabilized by one intramolecular C-H center dot center dot center dot O hydrogen bond. An O-H center dot center dot center dot O hydrogen bond and further C-H center dot center dot center dot O interactions can be observed in the packing.
The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a, 2,3,5a, 7,8,8a, 9,10,10a-decahydro-3-hydroxy-4,10a-dimethyl-8-methylidene-7-oxooxireno[5,6] cyclodeca[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P2(1)2(1)2(1), and its molecular structure consists of a methacrylic ester of a ten-membered ring sesquiterpenoid annelated with an epoxide and a butyrolactone. The structure is stabilized by one intramolecular C-H center dot center dot center dot O hydrogen bond. An O-H center dot center dot center dot O hydrogen bond and further C-H center dot center dot center dot O interactions can be observed in the packing.
Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy- filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano) diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
Phase equilibria that are relevant for the growth of Bi2MO4 have been studied experimentally, and the ternary phase diagrams of Bi2O3-PdO2-Pd and Bi2O3-Cu2O-CuO and its isopleth section Bi2O3-CuO were redetermined. It is shown that every melting and crystallization process is always accompanied by a redox process at the phase boundary and that for both title compounds, the valence of the transition metal is lowered during melting. Vice versa, during crystal growth, O-2 must be transported through the melt to the phase boundary. Based on these new insights provided by our thermodynamic studies, Bi2CuO4 single crystals with a length of up to 7 cm and a diameter of 6 mm were grown by the OFZ technique to be used for investigations of magnetic, electronic and thermal transport properties. The grown crystals were characterized by powder X-ray diffraction, Laue, magnetization and specific heat measurements.
Ecological effects of alien species can be dramatic, but management and prevention of negative impacts are often hindered by crypticity of the species or their ecological functions. Ecological functions can change dramatically over time, or manifest after long periods of an innocuous presence. Such cryptic processes may lead to an underestimation of long-term impacts and constrain management effectiveness. Here, we present a conceptual framework of crypticity in biological invasions. We identify the underlying mechanisms, provide evidence of their importance, and illustrate this phenomenon with case studies. This framework has potential to improve the recognition of the full risks and impacts of invasive species.
Taxonomy plays a central role in biological sciences. It provides a communication system for scientists as it aims to enable correct identification of the studied organisms. As a consequence, species descriptions should seek to include as much available information as possible at species level to follow an integrative concept of 'taxonomics'. Here, we describe the cryptic species Epimeria frankei sp. nov. from the North Sea, and also redescribe its sister species, Epimeria cornigera. The morphological information obtained is substantiated by DNA barcodes and complete nuclear 18S rRNA gene sequences. In addition, we provide, for the first time, full mitochondrial genome data as part of a metazoan species description for a holotype, as well as the neotype. This study represents the first successful implementation of the recently proposed concept of taxonomics, using data from high-throughput technologies for integrative taxonomic studies, allowing the highest level of confidence for both biodiversity and ecological research.
Taxonomy plays a central role in biological sciences. It provides a communication system for scientists as it aims to enable correct identification of the studied organisms. As a consequence, species descriptions should seek to include as much available information as possible at species level to follow an integrative concept of 'taxonomics'. Here, we describe the cryptic species Epimeria frankei sp. nov. from the North Sea, and also redescribe its sister species, Epimeria cornigera. The morphological information obtained is substantiated by DNA barcodes and complete nuclear 18S rRNA gene sequences. In addition, we provide, for the first time, full mitochondrial genome data as part of a metazoan species description for a holotype, as well as the neotype. This study represents the first successful implementation of the recently proposed concept of taxonomics, using data from high-throughput technologies for integrative taxonomic studies, allowing the highest level of confidence for both biodiversity and ecological research.
Garnet of eclogite (formerly termed garnet clinopyroxenite) hosted in lenses of orogenic garnet peridotite from the Granulitgebirge, NW Bohemian Massif, contains unique inclusions of granitic melt, now either glassy or crystallized. Analysed glasses and re‐homogenized inclusions are hydrous, peraluminous, and enriched in highly incompatible elements characteristic of the continental crust such as Cs, Li, B, Pb, Rb, Th, and U. The original melt thus represents a pristine, chemically evolved metasomatic agent, which infiltrated the mantle via deep continental subduction during the Variscan orogeny. The bulk chemical composition of the studied eclogites is similar to that of Fe‐rich basalt and the enrichment in LILE and U suggest a subduction‐related component. All these geochemical features confirm metasomatism. In comparison with many other garnet+clinopyroxene‐bearing lenses in peridotites of the Bohemian Massif, the studied samples from Rubinberg and Klatschmühle are more akin to eclogite than pyroxenites, as reflected in high jadeite content in clinopyroxene, relatively low Mg, Cr, and Ni but relatively high Ti. However, trace elements of both bulk rock and individual mineral phases show also important differences making these samples rather unique. Metasomatism involving a melt requiring a trace element pattern very similar to the composition reported here has been suggested for the source region of rocks of the so‐called durbachite suite, that is, ultrapotassic melanosyenites, which are found throughout the high‐grade Variscan basement. Moreover, the Th, U, Pb, Nb, Ta, and Ti patterns of these newly studied melt inclusions (MI) strongly resemble those observed for peridotite and its enclosed pyroxenite from the T‐7 borehole (Staré, České Středhoři Mountains) in N Bohemia. This suggests that a similar kind of crustal‐derived melt also occurred here. This study of granitic MI in eclogites from peridotites has provided the first direct characterization of a preserved metasomatic melt, possibly responsible for the metasomatism of several parts of the mantle in the Variscides.
Garnet of eclogite (formerly termed garnet clinopyroxenite) hosted in lenses of orogenic garnet peridotite from the Granulitgebirge, NW Bohemian Massif, contains unique inclusions of granitic melt, now either glassy or crystallized. Analysed glasses and re‐homogenized inclusions are hydrous, peraluminous, and enriched in highly incompatible elements characteristic of the continental crust such as Cs, Li, B, Pb, Rb, Th, and U. The original melt thus represents a pristine, chemically evolved metasomatic agent, which infiltrated the mantle via deep continental subduction during the Variscan orogeny. The bulk chemical composition of the studied eclogites is similar to that of Fe‐rich basalt and the enrichment in LILE and U suggest a subduction‐related component. All these geochemical features confirm metasomatism. In comparison with many other garnet+clinopyroxene‐bearing lenses in peridotites of the Bohemian Massif, the studied samples from Rubinberg and Klatschmühle are more akin to eclogite than pyroxenites, as reflected in high jadeite content in clinopyroxene, relatively low Mg, Cr, and Ni but relatively high Ti. However, trace elements of both bulk rock and individual mineral phases show also important differences making these samples rather unique. Metasomatism involving a melt requiring a trace element pattern very similar to the composition reported here has been suggested for the source region of rocks of the so‐called durbachite suite, that is, ultrapotassic melanosyenites, which are found throughout the high‐grade Variscan basement. Moreover, the Th, U, Pb, Nb, Ta, and Ti patterns of these newly studied melt inclusions (MI) strongly resemble those observed for peridotite and its enclosed pyroxenite from the T‐7 borehole (Staré, České Středhoři Mountains) in N Bohemia. This suggests that a similar kind of crustal‐derived melt also occurred here. This study of granitic MI in eclogites from peridotites has provided the first direct characterization of a preserved metasomatic melt, possibly responsible for the metasomatism of several parts of the mantle in the Variscides.
Cryo-electron microscopy (cryo-EM) is a powerful structure determination technique that is well-suited to the study of protein and polymer self-assembly in solution. In contrast to conventional transmission electron microscopy (TEM) sample preparation, which often times involves drying and staining, the frozen-hydrated sample preparation allows the specimens to be kept and imaged in a state closest to their native one. Here, we give a short overview of the basic principles of Cryo-EM and review our results on applying it to the study of different protein and polymer self-assembled nanostructures. More specifically, we show how we have applied cryo-electron tomography (cryo-ET) to visualize the internal morphology of self-assembled poly(ionic liquid) nanoparticles and cryo-EM single particle analysis (SPA) to determine the three-dimensional (3D) structures of artificial protein microtubules.
Crux Scenica
(2016)
Despite a long history of plate convergence at the western margin of the South American plate that has been ongoing since at least the Early Paleozoic, the southern Peruvian fore-arc displays little to no evidence of shortening. In the light of this observation, we assess the deformation history of the southern Peruvian fore-arc and its geodynamic implications. To accomplish this, we present a new structural and geo-thermochronological data set (zircon U-Pb, mica Ar-40/Ar-39, apatite and zircon fission-track and zircon (U-Th)/He analyses) for samples collected along a 400km long transect parallel to the trench. Our results show that the Mesoproterozoic gneissic basement was mainly at temperatures 350 degrees C since the Neoproterozoic and was later intruded by Jurassic volcanic arc plutons. Along the coast, a peculiar apatite fission-track age pattern, coupled with field observations and a synthesis of available geological maps, allows us to identify crustal-scale tilted blocks that span the coastal Peruvian fore-arc. These blocks, bounded by normal faults that are orthogonal to the trench, suggest post-60Ma trench-parallel extension that potentially accommodated oroclinal bending in this region. Block tilting is consistent with the observed and previously described switch in the location of sedimentary sources in the fore-arc basin. Our data set allows us to estimate the cumulative slip on these faults to be less than 2km and questions the large amount of trench-parallel extension suggested to have accommodated this bending.
In order to understand present day earthquake kinematics at the Indian plate boundary, we analyse seismic broadband data recorded between 2007 and 2015 by the regional network in the Garhwal-Kumaun region, northwest Himalaya. We first estimate a local 1-D velocity model for the computation of reliable Green's functions, based on 2837 P-wave and 2680 S-wave arrivals from 251 well located earthquakes. The resulting 1-D crustal structure yields a 4-layer velocity model down to the depths of 20 km. A fifth homogeneous layer extends down to 46 km, constraining the Moho using travel-time distance curve method. We then employ a multistep moment tensor (MT) inversion algorithm to infer seismic moment tensors of 11 moderate earthquakes with Mw magnitude in the range 4.0–5.0. The method provides a fast MT inversion for future monitoring of local seismicity, since Green's functions database has been prepared. To further support the moment tensor solutions, we additionally model P phase beams at seismic arrays at teleseismic distances. The MT inversion result reveals the presence of dominant thrust fault kinematics persisting along the Himalayan belt. Shallow low and high angle thrust faulting is the dominating mechanism in the Garhwal-Kumaun Himalaya. The centroid depths for these moderate earthquakes are shallow between 1 and 12 km. The beam modeling result confirm hypocentral depth estimates between 1 and 7 km. The updated seismicity, constrained source mechanism and depth results indicate typical setting of duplexes above the mid crustal ramp where slip is confirmed along out-of-sequence thrusting. The involvement of Tons thrust sheet in out-of-sequence thrusting indicate Tons thrust to be the principal active thrust at shallow depth in the Himalayan region. Our results thus support the critical taper wedge theory, where we infer the microseismicity cluster as a result of intense activity within the Lesser Himalayan Duplex (LHD) system.
A seismological network was operated at the junction of the aseismic Walvis Ridge with the northwestern Namibian coast. We mapped crustal thickness and bulk V-p/V-s ratio by the H-k analysis of receiver functions. In the Damara Belt, the crustal thickness is similar to 35km with a V-p/V-s ratio of <1.75. The crust is similar to 30km thick at the coast in the Kaoko Belt. Strong variations in crustal thickness and V-p/V-s ratios are found at the landfall of the Walvis Ridge. Here and at similar to 150km northeast of the coast, the crustal thickness increases dramatically reaching 44km and the V-p/V-s ratios are extremely high (similar to 1.89). These anomalies are interpreted as magmatic underplating produced by the mantle plume during the breakup of Gondwana. The area affected by the plume is smaller than 300km in diameter, possibly ruling out the existence of a large plume head under the continent during the breakup.
Crustal structure of the southern Dead Sea basin derived from project DESIRE wide-angle seismic data
(2009)
As part of the DEad Sea Integrated REsearch project (DESIRE) a 235 km long seismic wide-angle reflection/ refraction (WRR) profile was completed in spring 2006 across the Dead Sea Transform (DST) in the region of the southern Dead Sea basin (DSB). The DST with a total of about 107 km multi-stage left-lateral shear since about 18 Ma ago, accommodates the movement between the Arabian and African plates. It connects the spreading centre in the Red Sea with the Taurus collision zone in Turkey over a length of about 1 100 km. With a sedimentary infill of about 10 km in places, the southern DSB is the largest pull-apart basin along the DST and one of the largest pull-apart basins on Earth. The WRR measurements comprised 11 shots recorded by 200 three-component and 400 one-component instruments spaced 300 m to 1.2 km apart along the whole length of the E-W trending profile. Models of the P-wave velocity structure derived from the WRR data show that the sedimentary infill associated with the formation of the southern DSB is about 8.5 km thick beneath the profile. With around an additional 2 km of older sediments, the depth to the seismic basement beneath the southern DSB is about 11 km below sea level beneath the profile. Seismic refraction data from an earlier experiment suggest that the seismic basement continues to deepen to a maximum depth of about 14 km, about 10 km south of the DESIRE profile. In contrast, the interfaces below about 20 km depth, including the top of the lower crust and the Moho, probably show less than 3 km variation in depth beneath the profile as it crosses the southern DSB. Thus the Dead Sea pull-apart basin may be essentially an upper crustal feature with upper crustal extension associated with the left- lateral motion along the DST. The boundary between the upper and lower crust at about 20 km depth might act as a decoupling zone. Below this boundary the two plates move past each other in what is essentially a shearing motion. Thermo-mechanical modelling of the DSB supports such a scenario. As the DESIRE seismic profile crosses the DST about 100 km north of where the DESERT seismic profile crosses the DST, it has been possible to construct a crustal cross-section of the region before the 107 km left-lateral shear on the DST occurred.
In March 2010, the project CoCoCo (incipient COntinent-COntinent COllision) recorded a 650 km long amphibian N-S wide-angle seismic profile, extending from the Eratosthenes Seamount (ESM) across Cyprus and southern Turkey to the Anatolian plateau. The aim of the project is to reveal the impact of the transition from subduction to continent-continent collision of the African plate with the Cyprus-Anatolian plate. A visual quality check, frequency analysis and filtering were applied to the seismic data and reveal a good data quality. Subsequent first break picking, finite-differences ray tracing and inversion of the offshore wide-angle data leads to a first-arrival tomographic model. This model reveals (1) P-wave velocities lower than 6.5 km/s in the crust, (2) a variable crustal thickness of about 28 - 37 km and (3) an upper crustal reflection at 5 km depth beneath the ESM. Two land shots on Turkey, also recorded on Cyprus, airgun shots south of Cyprus and geological and previous seismic investigations provide the information to derive a layered velocity model beneath the Anatolian plateau and for the ophiolite complex on Cyprus. The analysis of the reflections provides evidence for a north-dipping plate subducting beneath Cyprus. The main features of this layered velocity model are (1) an upper and lower crust with large lateral changes of the velocity structure and thickness, (2) a Moho depth of about 38 - 45 km beneath the Anatolian plateau, (3) a shallow north-dipping subducting plate below Cyprus with an increasing dip and (4) a typical ophiolite sequence on Cyprus with a total thickness of about 12 km. The offshore-onshore seismic data complete and improve the information about the velocity structure beneath Cyprus and the deeper part of the offshore tomographic model. Thus, the wide-angle seismic data provide detailed insights into the 2-D geometry and velocity structures of the uplifted and overriding Cyprus-Anatolian plate. Subsequent gravity modelling confirms and extends the crustal P-wave velocity model. The deeper part of the subducting plate is constrained by the gravity data and has a dip angle of ~ 28°. Finally, an integrated analysis of the geophysical and geological information allows a comprehensive interpretation of the crustal structure related to the collision process.
In 2010, project CoCoCo (incipient COntinent-COntinent COllision) recorded a 650 km long amphibian N-S wide-angle seismic profile, extending from the Anatolian plateau across southern Turkey and Cyprus to just south of the Eratosthenes Seamount (ESM). The aim of the project is to reveal the impact of the transition from subduction to continent-continent collision of Africa with Anatolia. Arrival picking, finite-differences ray-tracing and inversion of the offshore and on-offshore data produced a tomographic model across southern Cyprus, the accretionary wedge and the ESM. The main features of this model are (1) crustal P-velocities predominantly lower than 6.5 km/s beneath the ESM, (2) crustal thickness between 28 and 37 km, (3) an upper crustal reflection at 5 km depth beneath the ESM, (4) the likely presence of oceanic crust south of the ESM and a transform margin north of it and (5) a 12 km thick ophiolite sequence on Cyprus. Land shots on Turkey, also recorded on Cyprus, gravity data and geological and previous seismic investigations allow to derive a layered velocity model beneath Anatolia and the northern part of Cyprus. The main features of this model are (1) Moho depths of 38–45 km beneath the Anatolian plateau, (2) an upper and lower crust with large lateral changes in velocity and thickness, (3) a north-dipping subducting plate below Cyprus with a steepening of the dip-angle of the plate at about 45 km depth. Thus, the wide-angle seismic and gravity data provide detailed insights into the 2-D geometry and velocity structures associated with the Cyprus Arc collision zone. Finally, integrated analysis of the geophysics and geology allows a comprehensive interpretation of the crustal structure related to the collision process.
The Dead Sea Transform (DST) is a major left-lateral strike-slip fault that accommodates the relative motion between the African and Arabian plates, connecting a region of extension in the Red Sea to the Taurus collision zone in Turkey over a length of about 1100 km. The Dead Sea Basin (DSB) is one of the largest basins along the DST. The DSB is a morphotectonic depression along the DST, divided into a northern and a southern sub-basin, separated by the Lisan salt diapir. We report on a receiver function study of the crust within the multidisciplinary geophysical project, DEad Sea Integrated REsearch (DESIRE), to study the crustal structure of the DSB. A temporary seismic network was operated on both sides of the DSB between 2006 October and 2008 April. The aperture of the network is approximately 60 km in the E-W direction crossing the DSB on the Lisan peninsula and about 100 km in the N-S direction. Analysis of receiver functions from the DESIRE temporary network indicates that Moho depths vary between 30 and 38 km beneath the area. These Moho depth estimates are consistent with results of near-vertical incidence and wide-angle controlled-source techniques. Receiver functions reveal an additional discontinuity in the lower crust, but only in the DSB and west of it. This leads to the conclusion that the internal crustal structure east and west of the DSB is different at the present-day. However, if the 107 km left-lateral movement along the DST is taken into account, then the region beneath the DESIRE array where no lower crustal discontinuity is observed would have lain about 18 Ma ago immediately adjacent to the region under the previous DESERT array west of the DST where no lower crustal discontinuity is recognized.
Previous thermomechanical modeling studies indicated that variations in the temperature and strength of the crystalline crust might be responsible for the juxtaposition of domains with thin-skinned and thick-skinned crustal deformation along strike the foreland of the central Andes. However, there is no evidence supporting this hypothesis from data-integrative models. We aim to derive the density structure of the lithosphere by means of integrated 3-D density modeling, in order to provide a new basis for discussions of compositional variations within the crust and for future thermal and rheological modeling studies. Therefore, we utilize available geological and geophysical data to obtain a structural and density model of the uppermost 200km of the Earth. The derived model is consistent with the observed Bouguer gravity field. Our results indicate that the crystalline crust in northern Argentina can be represented by a lighter upper crust (2,800kg/m(3)) and a denser lower crust (3,100kg/m(3)). We find new evidence for high bulk crustal densities >3,000kg/m(3) in the northern Pampia terrane. These could originate from subducted Puncoviscana wackes or pelites that ponded to the base of the crystalline crust in the late Proterozoic or indicate increasing bulk content of mafic material. The precise composition of the northern foreland crust, whether mafic or felsic, has significant implications for further thermomechanical models and the rheological behavior of the lithosphere. A detailed sensitivity analysis of the input parameters indicates that the model results are robust with respect to the given uncertainties of the input data.
The causes for the formation of large igneous provinces and hotspot trails are still a matter of considerable dispute. Seismic tomography and other studies suggest that hot mantle material rising from the core-mantle boundary (CMB) might play a significant role in the formation of such hotspot trails. An important area to verify this concept is the South Atlantic region, with hotspot trails that spatially coincide with one of the largest low-velocity regions at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to form during the separation of the South American and African continents at ca. 130 Ma as a consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to constrain processes of plume-lithosphere interaction and the formation of continental flood basalts (Parana and Etendeka continental flood basalts) and associated intrusive rocks. Our study identified a narrow region (<100 km) of high-seismic-velocity anomalies in the middle and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors connecting the high-velocity body with shallow crustal structures that we speculate to mark potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed massive but localized mafic intrusion into the lower crust results from similar-sized variations in the lithosphere (i.e., lithosphere thickness or preexisting structures).
Linking deep seismic profiles with regional-scale gravity inversion is a powerful tool to deduce the architecture of rifted margins and their structural evolution. Here we map upper and lower crustal thicknesses of the northern South China Sea (SCS) margin in order to investigate the occurrence of depth-dependent crustal extension from the proximal to the distal margin. By comparing upper and lower crustal stretching factors, we find that the northern margin of the SCS is segmented in three parts: (1) sedimentary basins where upper crust is stretched more than lower crust, (2) distal margin where lower crust is stretched more than upper crust, (3) mostly proximal margin regions where the two layers have similar stretching factors. Our results suggest that sedimentary basins and distal margin prominently feature depth-dependent extension, however accommodated by different processes. While differential thinning within sedimentary basins appears to be governed by lateral pressure variations inducing lower crustal flow, we suggest the distal margin to be affected by a combination of mantle flow-induced lower crustal shearing and sequential fault activity during crustal hyper-extension.
The quantitative descriptions of the state of stress in the Earth’s crust, and spatial-temporal stress changes are of great importance in terms of scientific questions as well as applied geotechnical issues. Human activities in the underground (boreholes, tunnels, caverns, reservoir management, etc.) have a large impact on the stress state. It is important to assess, whether these activities may lead to (unpredictable) hazards, such as induced seismicity. Equally important is the understanding of the in situ stress state in the Earth’s crust, as it allows the determination of safe well paths, already during well planning. The same goes for the optimal configuration of the injection- and production wells, where stimulation for artificial fluid path ways is necessary.
The here presented cumulative dissertation consists of four separate manuscripts, which are already published, submitted or will be submitted for peer review within the next weeks. The main focus is on the investigation of the possible usage of geothermal energy in the province Alberta (Canada). A 3-D geomechanical–numerical model was designed to quantify the contemporary 3-D stress tensor in the upper crust. For the calibration of the regional model, 321 stress orientation data and 2714 stress magnitude data were collected, whereby the size and diversity of the database is unique. A calibration scheme was developed, where the model is calibrated versus the in situ stress data stepwise for each data type and gradually optimized using statistically test methods. The optimum displacement on the model boundaries can be determined by bivariate linear regression, based on only three model runs with varying deformation ratio. The best-fit model is able to predict most of the in situ stress data quite well. Thus, the model can provide the full stress tensor along any chosen virtual well paths. This can be used to optimize the orientation of horizontal wells, which e.g. can be used for reservoir stimulation. The model confirms regional deviations from the average stress orientation trend, such as in the region of the Peace River Arch and the Bow Island Arch.
In the context of data compilation for the Alberta stress model, the Canadian database of the World Stress Map (WSM) could be expanded by including 514 new data records. This publication of an update of the Canadian stress map after ~20 years with a specific focus on Alberta shows, that the maximum horizontal stress (SHmax) is oriented southwest to northeast over large areas in Northern America. The SHmax orientation in Alberta is very homogeneous, with an average of about 47°. In order to calculate the average SHmax orientation on a regular grid as well as to estimate the wave-length of stress orientation, an existing algorithm has been improved and is applied to the Canadian data. The newly introduced quasi interquartile range on the circle (QIROC) improves the variance estimation of periodic data, as it is less susceptible to its outliers.
Another geomechanical–numerical model was built to estimate the 3D stress tensor in the target area ”Nördlich Lägern” in Northern Switzerland. This location, with Opalinus clay as a host rock, is a potential repository site for high-level radioactive waste. The performed modelling aims to investigate the sensitivity of the stress tensor on tectonic shortening, topography, faults and variable rock properties within the Mesozoic sedimentary stack, according to the required stability needed for a suitable radioactive waste disposal site. The majority of the tectonic stresses caused by the far-field shortening from the South are admitted by the competent rock units in the footwall and hanging wall of the argillaceous target horizon, the Upper Malm and Upper Muschelkalk. Thus, the differential stress within the host rock remains relatively low. East-west striking faults release stresses driven by tectonic shortening. The purely gravitational influence by the topography is low; higher SHmax magnitudes below topographical depression and lower values below hills are mainly observed near the surface. A complete calibration of the model is not possible, as no stress magnitude data are available for calibration, yet. The collection of this data will begin in 2015; subsequently they will be used to adjust the geomechanical–numerical model again.
The third geomechanical–numerical model investigates the stress variation in an ultra-deep gold mine in South Africa. This reservoir model is spatially one order of magnitude smaller than the previous local model from Northern Switzerland. Here, the primary focus is to investigate the hypothesis that the Mw 1.9 earthquake on 27 December 2007 was induced by stress changes due to the mining process. The Coulomb failure stress change (DeltaCFS) was used to analyse the stress change. It confirmed that the seismic event was induced by static stress transfer due to the mining progress. The rock was brought closer to failure on the derived rupture plane by stress changes of up to 1.5–15MPa, in dependence of the DeltaCFS analysis type. A forward modelling of a generic excavation scheme reveals that with decreasing distance to the dyke the DeltaCFS values increase significantly. Hence, even small changes in the mining progress can have a significant impact on the seismic hazard risk, i.e. the change of the occurrence probability to induce a seismic event of economic concern.
An analysis of the shear (S) waves recorded during the wide-angle reflection/refraction (WRR) experiment as part of the DESERT project crossing the Dead Sea Transform (DST) reveals average crustal S-wave velocities of 3.3-3.5 km s(-1) beneath the WRR profile. Together with average crustal P-wave velocities of 5.8-6.1 km s(-1) from an already published study this provides average crustal Poisson's ratios of 0.26-0.27 (V-p/V-s = 1.76-1.78) below the profile. The top two layers consisting predominantly of sedimentary rocks have S- wave velocities of 1.8-2.7kms(-1) and Poisson's ratios of 0.25-0.31 (V-p/V-s = 1.73-1.91). Beneath these two layers the seismic basement has average S- wave velocities of around 3.6 km s(-1) east of the DST and about 3.7 km s(-1) west of the DST and Poisson's ratios of 0.24-0.25 (V-p/V-s = 1.71-1.73). The lower crust has an average S-wave velocity of about 3.75 km s(-1) and an average Poisson's ratio of around 0.27 (V-p/V-s = 1.78). No Sn phase refracted through the uppermost mantle was observed. The results provide for the first time information from controlled source data on the crustal S-wave velocity structure for the region west of the DST in Israel and Palestine and agree with earlier results for the region east of the DST in the Jordanian highlands. A shear wave splitting study using SKS waves has found evidence for crustal anisotropy beneath the WRR profile while a receiver function study has found evidence for a lower crustal, high S-wave velocity layer east of the DST below the profile. Although no evidence was found in the S-wave data for either feature, the S-wave data are not incompatible with crustal anisotropy being present as the WRR profile only lies 30 degrees off the proposed symmetry axis of the anisotropy where the difference in the two S-wave velocities is still very small. In the case of the lower crustal, high S-wave velocity layer, if the velocity change at the top of this layer comprises a small first-order discontinuity underlain by a 2 km thick transition zone, instead of just a large first-order discontinuity, then both the receiver function data and the WRR data presented here can be satisfied. Finally, the S-wave velocities and Poisson's ratios which have been derived in this study are typical of continental crust and do not require extensional processes to explain them
Crustal seismic attenuation parameters in the western region of the North Anatolian Fault Zone
(2020)
Detailed knowledge of the crustal structure along the North Anatolian Fault Zone can help in understanding past and present tectonic processes in relation to the deformation history. To estimate the frequency-dependent crustal attenuation parameters beneath the western part of the North Anatolian Fault Zone we apply acoustic radiative transfer theory under the assumption of multiple isotropic scattering to generate synthetic seismogram envelopes. The inversion depends on finding an optimal fit between observed and synthetically computed coda wave envelopes in five frequency bands. 2-D lateral variation of intrinsic and scattering attenuation at various frequencies tends to three crustal blocks (i.e., Armutlu-Almacik, Istanbul-Zonguldak and Sakarya Zones) separated by the southern and northern branches of the western part of the North Anatolian Fault Zone. Overall, scattering attenuation appears to be dominant over intrinsic attenuation in the study area at lower frequencies. Relatively low attenuation properties are observed beneath the older Istanbul Zone whereas higher attenuation properties are found for the younger Sakarya Zone. The Armutlu Almacik Zone exhibits more complex lateral variations. Very high attenuation values towards the west characterize the area of the Kuzuluk Basin, a pull-apart basin formed under west-east extension. Our coda-derived moment magnitudes are similar to the local magnitude estimates that were previously calculated for the same earthquakes. For smaller earthquakes (M-L < 2.5), however, the relation between local and moment magnitudes appears to lose its coherency. This may stem from various reasons including the use of seismic data recorded in finite sampling interval, possible biases in local magnitude estimates of earthquake catalogues as well as biases due to wrong assumptions to consider anelastic attenuation terms.
Nd whole-rock data from the Windmill Islands area yield early Proterozoic to middle Archaean Nd model ages. These crustal residence times are consistent with regional correlations with other parts of Antarctica (Bunger Hills, Denman Glacier area) and the Albany-Fraser Orogen of south-western Australia during the Mid-Proterozoic and thus support reconstructions with a continuous Mid-Proterozoic orogen in these areas. The new Nd isotope data provide strong evidence that no age boundary exists between the higher- and lower-grade parts of the Windmill Islands area, and that the metamorphic complex represents a single terrane with a common crustal history. The data support the notion of a time- link between the occurrence of intrusive charnockites (C-type magmas) and high-grade metamorphism. The magmatic rocks and orthogneisses in the area are interpreted to have a mixed source consisting of older crustal components, i.e. older sediments (ca. 3.2-2.6 Ga) and a younger mafic component (ca. 1.9 Ga). Two garnet Sm-Nd isochrons yield ages of 1156±17 Ma and 1137±2.5 Ma and are identical to SHRIMP U-Pb results on monazite from these samples. A garnet Sm-Nd age of 1123±13 Ma for the Ford granite is significantly younger than the SHRIMP U-Pb zircon age for this sample. The difference relates to the different closure temperature of each isotopic system and is thus interpreted as initial cooling after granulite facies metamorphism. Keywords. East Antarctica - Granulites - Garnet-whole rock isochrons - Intrusive charnockite - Nd model ages
Crustal deformation can be the result of volcanic and tectonic activity such as fault dislocation and magma intrusion. The crustal deformation may precede and/or succeed the earthquake occurrence and eruption. Mitigating the associated hazard, continuous monitoring of the crustal deformation accordingly has become an important task for geo-observatories and fast response systems. Due to highly non-linear behavior of the crustal deformation fields in time and space, which are not always measurable using conventional geodetic methods (e.g., Leveling), innovative techniques of monitoring and analysis are required. In this thesis I describe novel methods to improve the ability for precise and accurate mapping the spatiotemporal surface deformation field using multi acquisitions of satellite radar data. Furthermore, to better understand the source of such spatiotemporal deformation fields, I present novel static and time dependent model inversion approaches. Almost any interferograms include areas where the signal decorrelates and is distorted by atmospheric delay. In this thesis I detail new analysis methods to reduce the limitations of conventional InSAR, by combining the benefits of advanced InSAR methods such as the permanent scatterer InSAR (PSI) and the small baseline subsets (SBAS) with a wavelet based data filtering scheme. This novel InSAR time series methodology is applied, for instance, to monitor the non-linear deformation processes at Hawaii Island. The radar phase change at Hawaii is found to be due to intrusions, eruptions, earthquakes and flank movement processes and superimposed by significant environmental artifacts (e.g., atmospheric). The deformation field, I obtained using the new InSAR analysis method, is in good agreement with continuous GPS data. This provides an accurate spatiotemporal deformation field at Hawaii, which allows time dependent source modeling. Conventional source modeling methods usually deal with static deformation field, while retrieving the dynamics of the source requires more sophisticated time dependent optimization approaches. This problem I address by combining Monte Carlo based optimization approaches with a Kalman Filter, which provides the model parameters of the deformation source consistent in time. I found there are numerous deformation sources at Hawaii Island which are spatiotemporally interacting, such as volcano inflation is associated to changes in the rifting behavior, and temporally linked to silent earthquakes. I applied these new methods to other tectonic and volcanic terrains, most of which revealing the importance of associated or coupled deformation sources. The findings are 1) the relation between deep and shallow hydrothermal and magmatic sources underneath the Campi Flegrei volcano, 2) gravity-driven deformation at Damavand volcano, 3) fault interaction associated with the 2010 Haiti earthquake, 4) independent block wise flank motion at the Hilina Fault system, Kilauea, and 5) interaction between salt diapir and the 2005 Qeshm earthquake in southern Iran. This thesis, written in cumulative form including 9 manuscripts published or under review in peer reviewed journals, improves the techniques for InSAR time series analysis and source modeling and shows the mutual dependence between adjacent deformation sources. These findings allow more realistic estimation of the hazard associated with complex volcanic and tectonic systems.
Melanoma represents a prime example demonstrating the success of targeted therapy in cancer. Nevertheless, it remained a deadly disease until now, and the identification of new, independent strategies as well as the understanding of their molecular mechanisms may help to finally overcome the high mortality. Both indirubins and TNF-related apoptosis-inducing ligand (TRAIL) represent promising candidates. Here, the indirubin derivative DKP-073 is shown to trigger apoptosis in melanoma cells, which is enhanced by the combination with TRAIL and is accompanied by complete loss of cell viability. Addressing the signaling cascade, characteristic molecular steps were identified as caspase-3 activation, downregulation of XIAP, upregulation of p53 and TRAIL receptor 2, loss of mitochondrial membrane potential, and STAT-3 dephosphorylation. The decisive step, however, turned out to be the early production of ROS already at 1 h. This was proven by antioxidant pretreatment, which completely abolished apoptosis induction and loss of cell viability as well as abrogated all signaling effects listed above. Thus, ROS appeared as upstream of all proapoptotic signaling. The data indicate a dominant role of ROS in apoptosis regulation, and the new pathway may expose a possible Achilles heel of melanoma.