Vollbrecht, Axel

[["dc.bibliographiccitation.firstpage","300"],["dc.bibliographiccitation.journal","Marine and Petroleum Geology"],["dc.bibliographiccitation.lastpage","322"],["dc.bibliographiccitation.volume","77"],["dc.contributor.author","Duschl, Florian"],["dc.contributor.author","van den Kerkhof, Alfons M."],["dc.contributor.author","Sosa, Graciela"],["dc.contributor.author","Leiss, Bernd"],["dc.contributor.author","Wiegand, Bettina A."],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Sauter, Martin"],["dc.date.accessioned","2018-11-07T10:06:47Z"],["dc.date.available","2018-11-07T10:06:47Z"],["dc.date.issued","2016"],["dc.description.abstract","New petrographic and fluid inclusion data from core samples of Upper Permian dolomitic limestone (Hauptdolomit, Zechstein group, Stassfurt carbonate sequence) from a gas field located at the northern border of the Lower Saxony Basin (LSB) essentially improve the understanding of the basin development. The gas production at the locality is characterized by very high CO2 concentrations of 75-100% (with CH4 and N-2). Samples consist of fine grained, mostly laminated and sometimes brecciated dolomitic limestone (mudstone/wackestone) from the transition zone between the shallow water zone (platform) and the upper slope. The study focuses on migration fluids, entrapped as fluid inclusions in diagenetic anhydrite, calcite, and fluorite, and in syn-diagenetic microfractures, as well as on the geochemistry of fluorite fracture mineralizations, obtained by LA-ICP-MS analysis. Fluid inclusion studies show that the diagenetic fluid was rich in H2O-NaCl-CaCl2. Recrystallized anhydrite contains aqueous inclusions with homogenization temperatures (T-h) of ca. 123 degrees C, but somewhat higher Th of ca. 142 degrees C was found for calcite cement followed by early Fluorite A with Th of 147 degrees C. A later Fluorite B preserves gas inclusions and brines with maximum Th of 156 degrees C. Fluorite B crystallized in fractures during the mobilization of CO2-bearing brines. Crossing isochores for co-genetic aqueous-carbonic and carbonic inclusions indicate fluid trapping conditions of 180-200 degrees C and 900-1000 bars. delta C-13-isotopic ratios of gas trapped in fluid inclusions suggest an organic origin for CH4, while the CO2 is likely of inorganic origin. Basin modelling (1D) shows that the fault block structure of the respective reservoir has experienced an uplift of >1000 m since Late Cretaceous times. The fluid inclusion study allows us to, 1) model the evolution of the LSB and fluid evolution by distinguishing different fluid systems, 2) determine the appearance of CO2 in the geological record and, 3) more accurately estimate burial and uplift events in individual parts of the LSB. (C) 2016 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","EU [282900]"],["dc.identifier.doi","10.1016/j.marpetgeo.2016.06.020"],["dc.identifier.isi","000384861400020"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39159"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1873-4073"],["dc.relation.issn","0264-8172"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Fluid inclusion and microfabric studies on Zechstein carbonates (Ca2) and related fracture mineralizations - New insights on gas migration in the Lower Saxony Basin (Germany)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","401"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Solid Earth"],["dc.bibliographiccitation.lastpage","414"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Krumbholz, Michael"],["dc.contributor.author","Bock, M."],["dc.contributor.author","Burchardt, S."],["dc.contributor.author","Kelka, U."],["dc.contributor.author","Vollbrecht, Axel"],["dc.date.accessioned","2018-11-07T09:14:31Z"],["dc.date.available","2018-11-07T09:14:31Z"],["dc.date.issued","2012"],["dc.description.abstract","In recent years, the electromagnetic radiation (EMR) method has been used to detect faults and to determine main horizontal stress directions from variations in intensities and directional properties of electromagnetic emissions, which are assumed to be generated during micro-cracking. Based on a large data set taken from an area of about 250 000 km(2) in Northern Germany, Denmark, and southern Sweden with repeated measurements at one location during a time span of about 1.5 yr, the method was systematically tested. Reproducible observations of temporary changes in the signal patterns, as well as a strongly concentric spatial pattern of the main directions of the magnetic component of the EMR point to very low frequency (VLF) transmitters as the main source and hence raise serious concerns about the applicability of the method to determine recent crustal stresses. We conclude that the EMR method, at its current stage of development, does not allow determination of the main horizontal stress directions."],["dc.description.sponsorship","University of Gottingen"],["dc.identifier.doi","10.5194/se-3-401-2012"],["dc.identifier.isi","000321443000005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/27435"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Copernicus Gesellschaft Mbh"],["dc.relation.issn","1869-9510"],["dc.title","A critical discussion of the electromagnetic radiation (EMR) method to determine stress orientations within the crust"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","153"],["dc.bibliographiccitation.issue","1-4"],["dc.bibliographiccitation.journal","Tectonophysics"],["dc.bibliographiccitation.lastpage","170"],["dc.bibliographiccitation.volume","427"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Pawlowski, Jan"],["dc.contributor.author","Leiss, Bernd"],["dc.contributor.author","Heinrichs, Till"],["dc.contributor.author","Seidel, Madlen"],["dc.contributor.author","Kronz, Andreas"],["dc.date.accessioned","2018-11-07T08:56:20Z"],["dc.date.available","2018-11-07T08:56:20Z"],["dc.date.issued","2006"],["dc.description.abstract","Mylonitic gneisses from the Munchberg Massif contain single grains (type I) and polycrystalline aggregates (type 11) of garnet displaying a distinct elongation parallel to a macroscopic lineation which is interpreted as the result of ductile deformation. Lattice-preferred orientations of quartz (textures) symmetrical to the macroscopic foliation and lineation and the lack of rotational microfabrics indicate that the bulk deformation was pure shear at least during the latest strain increments. Garnet textures measured by EBSD together with microprobe analyses demonstrate that these two structural types of garnet can be related to two different processes of ductile deformation: (1) For the single grains stretching can be attributed to diffusion creep along grain boundary zones (Coble creep). The related mass transfer is indicated by the fact that primary growth zones are cut off at the long faces of the grains while the related strain shadow domains do not show comparable chemical zoning. Pressure solution and precipitation suitable to produce similar structures can be largely ruled out because retrogressive reactions pointing to the presence of free hydrous fluids are missing. (2) For the polycrystalline garnet aggregates consisting of cores grading into fine-grained mantles, dislocation creep and associated rotation recrystallization can be assumed. Continuous lattice rotation from the core to the outer polycrystalline rim allow a determination of the related dominant slip systems which are {100} < 010 > and equivalent systems according to the cubic lattice symmetry. The same holds for garnets which appear to be completely recrystallized. For this type of fine-grained aggregates an alternative nucleation model is discussed. Due to penetrative dislocation glide in connection with short range diffusion and the resulting lattice rotation, primary growth zones are strongly disturbed. Since for the considered rock unit of the Munchberg Massif peak metamorphic temperatures between 630 and 670 degrees C can be assumed, this study clearly demonstrates that the inferred processes of ductile garnet deformation can occur not only in FIT regimes as often suggested in the literature even if embedded within a matrix of \"low-strength\" minerals like quartz, feldspars and micas. (c) 2006 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.tecto.2006.05.024"],["dc.identifier.isi","000242871300010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23124"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.publisher.place","Amsterdam"],["dc.relation.conference","International Conference on Deformation Mechanisms, Rheology and Tectonics (DRT 2005)"],["dc.relation.eventlocation","ETH Zurich, Zurich, SWITZERLAND"],["dc.relation.issn","0040-1951"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Ductile deformation of garnet in mylonitic gneisses from the Munchberg Massif (Germany)"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","413"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Geophysical Journal International"],["dc.bibliographiccitation.lastpage","424"],["dc.bibliographiccitation.volume","141"],["dc.contributor.author","Rasolofosaon, P. N. J."],["dc.contributor.author","Rabbel, W."],["dc.contributor.author","Siegesmund, Siegfried"],["dc.contributor.author","Vollbrecht, A."],["dc.date.accessioned","2021-12-08T12:27:32Z"],["dc.date.available","2021-12-08T12:27:32Z"],["dc.date.issued","2000"],["dc.identifier.doi","10.1046/j.1365-246x.2000.00093.x"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/95381"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-476"],["dc.relation.eissn","1365-246X"],["dc.relation.issn","0956-540X"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Characterization of crack distribution: fabric analysis versus ultrasonic inversion"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","369"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Zeitschrift der Deutschen Gesellschaft für Geowissenschaften"],["dc.bibliographiccitation.lastpage","377"],["dc.bibliographiccitation.volume","161"],["dc.contributor.author","Tanner, David Colin"],["dc.contributor.author","Leiss, Bernd"],["dc.contributor.author","Vollbrecht, Axel"],["dc.date.accessioned","2018-11-07T08:36:35Z"],["dc.date.available","2018-11-07T08:36:35Z"],["dc.date.issued","2010"],["dc.description.abstract","A detailed examination and interpretation of outcrop data in the northern part of the Leinetal Graben in Lower Saxony, Germany, suggests the graben is dissected and partly-bound by faults with a strong strike-slip history. We envisage a two-part tectonic evolution, which began in the Late Cretaceous to Early Cenozoic, with approximately N-S compression, which caused east-west extension (the bounding normal faults of the Leinetal Graben) and dextral strike-slip movement on the Ahlsburg Lineament. We postulate that the Ahlsburg Lineament was originally a relay ramp that developed in the early stages of the graben history. Later the major stress axes rotated anticlockwise, so that the maximum horizontal stress was oriented NW-SE. Because of this, the graben-bounding faults and the Ahlsburg Lineament were then subject to inversion under sinistral transpression, while new E-W striking dextral strike-slip faults were also initiated."],["dc.identifier.doi","10.1127/1860-1804/2010/0161-0369"],["dc.identifier.isi","000285290500001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/18350"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1860-1804"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","The role of strike-slip tectonics in the Leinetal Graben, Lower Saxony"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","348"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","International Geology Review"],["dc.bibliographiccitation.lastpage","367"],["dc.bibliographiccitation.volume","54"],["dc.contributor.author","Cao, Shuyun"],["dc.contributor.author","Liu, Junlai"],["dc.contributor.author","Leiss, Bernd"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Genser, Johann"],["dc.contributor.author","Neubauer, Franz"],["dc.contributor.author","Zhao, Chunqiang"],["dc.date.accessioned","2018-11-07T09:15:46Z"],["dc.date.available","2018-11-07T09:15:46Z"],["dc.date.issued","2012"],["dc.description.abstract","The Diancang Shan metamorphic massif, the northwestern extension of the Ailao Shan Massif, is a typical metamorphic complex situated along the NW-SE-trending Ailao Shan-Red River shear zone. Diancang Shan granitic and amphibolitic mylonites collected from sheared high-grade metamorphic rocks were studied using petrographic and electron-backscatter diffraction techniques. Sensitive high-resolution ion microprobe U-Pb dating of zircon grains from the granitic mylonites constrains the timing of shearing. Macro-and microstructural and textural analysis reveals intense plastic deformation of feldspar, quartz, and amphibole under amphibolite-facies conditions, all consistently document left-lateral shearing. Porphyritic monzogranitic mylonite within the shear zone possesses evidence supporting a sequential, progressive process from crystallization during magma emplacement, through submagmatic flow to solid-state plastic deformation. We suggest that the early-kinematic pluton subsequently underwent strong left-lateral strike-slip shearing. The development of complex textures of quartz, feldspar, and amphibole from the granitic and amphibolitic mylonites apparently records successive variation of conditions attending coherent, solid-state high-temperature ductile deformation during regional left-lateral shearing. All magmatic zircons from the mylonitized porphyritic monzogranite give U-Pb ages of 30.95 +/- 0.61 million years for the crystallization of the granite. This age provides the timing of onset of left-lateral shearing along the Ailao Shan-Red River shear zone in the Diancang Shan high-grade metamorphic massif."],["dc.identifier.doi","10.1080/00206814.2010.543789"],["dc.identifier.isi","000300153300007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/27776"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1938-2839"],["dc.relation.issn","0020-6814"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Initiation of left-lateral deformation along the Ailao Shan-Red River shear zone: new microstructural, textural, and geochronological constraints from the Diancang Shan metamorphic massif, SW Yunnan, China"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","33"],["dc.bibliographiccitation.journal","Journal of Structural Geology"],["dc.bibliographiccitation.lastpage","43"],["dc.bibliographiccitation.volume","65"],["dc.contributor.author","Krumbholz, Michael"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Aschoff, Marius"],["dc.date.accessioned","2018-11-07T09:37:27Z"],["dc.date.available","2018-11-07T09:37:27Z"],["dc.date.issued","2014"],["dc.description.abstract","The strike direction of open intragranular microcracks in quartz and feldspar host grains was determined using optical transmission and reflection microscopy on eight oriented samples taken in two study areas in Precambrian basement rocks of southern and south-central Sweden. For an area of about 160 km(2) (SW of Vastervik) and two sample locations (W of Uppsala), the vast majority of open microcracks displays a strong preferred NW-SE strike direction. According to the common assumptions that natural cracks in crystalline rocks are predominantly extensional (mode I), and that open cracks belong to the latest microcrack generation, these strike directions should reflect the (sub-) recent main horizontal stress direction (sigma H) of the recent tectonic stress field. This conclusion is supported by corresponding directions known from in situ stress measurements and focal plane solutions in the vicinity of the study areas. It is remarkable that even in samples taken close (i.e. a few hundred metres) to recently active large scale faults the orientation of microcracks does not deviate from this common direction. This may point to slip on already softened faults, very local stress reorientations (e.g. m-scale) or that local stress relief was accomplished by other processes at microscale, e.g. mechanical twinning in favourably oriented feldspar crystals, or slip on grain boundaries. (C) 2014 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.jsg.2014.03.006"],["dc.identifier.isi","000337778800003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32844"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0191-8141"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Recent horizontal stress directions in basement rocks of southern Sweden deduced from open microcracks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","433"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Mineralium Deposita"],["dc.bibliographiccitation.lastpage","451"],["dc.bibliographiccitation.volume","37"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Oberthur, T."],["dc.contributor.author","Ruedrich, Joerg"],["dc.contributor.author","Weber, K."],["dc.date.accessioned","2018-11-07T10:29:21Z"],["dc.date.available","2018-11-07T10:29:21Z"],["dc.date.issued","2002"],["dc.description.abstract","Microfabrics of detrital quartz grains and quartz cement of four gold- and uranium-bearing conglomerates of various goldfields of the Witwatersrand Basin, South Africa, were investigated by optical and cathodoluminescence microscopy. The study revealed that the vast majority of quartz grains (< 5 mm) originate from felsic magmatic source rocks. Cherts and polymineralic mineral grains, pointing to greenschist to amphibolite facies metasedimentary rocks, follow in abundance, whereas diagenetic to weakly metamorphosed quartzites are subordinate. Material from hydrothermal vein quartz is almost completely lacking, both in the sand and in the pebble fraction. No obvious relationships are discernible between the varying proportions of detrital siliciclastic components of the different reefs and their ore grades. Assuming a sedimentological control of gold distribution, this finding supports multiple sources for the detrital components, which were thoroughly mixed during transport. The post-depositional history of the sediments is characterized by a complex polyphase succession of deformation, cementation and hydrothermal alteration events. Both fragmentation and pressure solution features within detrital quartz, quartz cement and round grains of pyrite, zircon, chromite and uraninite demonstrate that these materials were present in the conglomerates during diagenesis, and, thus, are true detrital grains with abraded, rounded grain morphologies. By analogy, it is assumed that gold is also a detrital component, although most of the gold grains display characteristics of hydrothermal overprinting. During subsequent metamorphism, micro-shear zones are developed, and brittle-ductile crystal-plastic deformation and limited quartz recrystallization occur. Maximum temperatures of about 350 degreesC were reached on the prograde metamorphic path. Recrystallization and redistribution of detrital siliciclastic and ore minerals took place, and various hydrothermal/metamorphic minerals including chlorite, sericite, pyrophyllite and chloritoid were formed. These redistribution processes involved existing detrital minerals only and were generally isochemical because little evidence exists for the development of a secondary porosity and permeability that would allow major external inputs into the Witwatersrand conglomerates. Most of the gold grains have hydrothermal characteristics, as evidenced by their authigenic, crystalline shapes and their chemical compositions. However, these features are regarded to result from overprinting. Most likely, the gold grains experienced more drastic modifications relative to other ore components because of the ductile and mobile nature of gold. The retrograde metamorphic path is characterized by percolating radioactive fluids at T < 300 degreesC, recorded by radiation damage indicated by cathodoluminescence alteration rims along quartz grain boundaries and microcracks. The degrees of radiation damage observed are proportional to the uranium contents of the conglomerate ores. The collective evidence of our study supports the modified placer model for the genesis of the Witwatersrand ores. This model explains most of the observations on the detrital mineral assemblage and its post-depositional modification elegantly and in a satisfactory manner."],["dc.identifier.doi","10.1007/s00126-001-0236-5"],["dc.identifier.isi","000176852200002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43627"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0026-4598"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Microfabric analyses applied to the Witwatersrand gold- and uranium-bearing conglomerates: constraints on the provenance and post-depositional modification of rock and ore components"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","41"],["dc.bibliographiccitation.journal","GFF"],["dc.bibliographiccitation.lastpage","45"],["dc.bibliographiccitation.volume","130"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Leiss, Bernd"],["dc.date.accessioned","2018-11-07T11:17:40Z"],["dc.date.available","2018-11-07T11:17:40Z"],["dc.date.issued","2008"],["dc.description.abstract","The metamorphic siliciclastics of the Palaeoproterozoic Vastervik Basin locally display a complex fabric development caused by Si-metasomatism and ductile deformation. This is in contrast to large areas where primary sedimentary fabrics are remarkably well preserved. Fabric and texture analyses indicate that significant volumes of almost pure quartzites originated from arkosic sandstones due to metasomatic replacement of K-feldspar and plagioclase by quartz. These rheologically \"soft\" quartzites were preferentially affected by subsequent ductile deformation indicated by dynamic recrystallization fabrics and strongly developed quartz textures. It is suggested that both Si-metasomatism and ductile deformation are related to structural aureoles around minor granitic intrusions."],["dc.identifier.isi","000256225300005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/54863"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1103-5897"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Complex fabric development in Paleoproterozoic meta-quartzites of the Vastervik Basin, SE Sweden"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]