Solid Earth最新文献

{"title":"Rapid hydration and weakening of anhydrite under stress: implications for natural hydration in the Earth's crust and mantle","authors":"Johanna Heeb, D. Healy, N. Timms, E. Gomez‐Rivas","doi":"10.5194/se-14-985-2023","DOIUrl":"https://doi.org/10.5194/se-14-985-2023","url":null,"abstract":"Abstract. Mineral hydration is an important geological process that\u0000influences the rheology and geochemistry of rocks and the fluid budget of\u0000the Earth's crust and mantle. Constant-stress differential compaction\u0000(CSDC) tests, dry and “wet” tests under confining pressure, and axial-stress tests were\u0000conducted for the first time to investigate the influence of triaxial\u0000stress on hydration in anhydrite–gypsum aggregates. Characterization of the\u0000samples before and after triaxial experiments was performed with optical\u0000and scanning electron microscopy, including energy-dispersive spectroscopy\u0000and electron backscatter diffraction mapping. Stress–strain data reveal that\u0000samples that underwent constant-stress differential compaction in the\u0000presence of fluids are ∼ 14 % to ∼ 41 % weaker\u0000than samples deformed under wet conditions. The microstructural analysis\u0000shows that there is a strong temporal and spatial connection between the\u0000geometry, distribution, and evolution of fractures and hydration products.\u0000The increasing reaction surface area in combination with pre-existing gypsum\u0000in a gypsum-bearing anhydrite rock led to rapid gypsification. The\u0000crystallographic orientations of newly formed vein gypsum have a systematic\u0000preferred orientation for long distances along veins, beyond the grain\u0000boundaries of wall-rock anhydrite. Gypsum crystallographic orientations in\u0000{100} and {010} are\u0000systematically and preferentially aligned parallel to the direction of\u0000maximum shear stress (45∘ to σ1). Gypsum is also not\u0000always topotactically linked to the wall-rock anhydrite in the immediate\u0000vicinity. This study proposes that the selective inheritance of crystal\u0000orientations from favourably oriented wall-rock anhydrite grains for the\u0000minimization of free energy for nucleation under stress leads to the\u0000systematic preferred orientation of large, new gypsum grains. A sequence is\u0000suggested for hydration under stress that requires the development of\u0000fractures accompanied by localized hydration. Hydration along fractures with\u0000a range of apertures up to 120 µm occurred in under 6 h. Once\u0000formed, gypsum-filled veins represent weak surfaces and are the locations of\u0000further shear fracturing, brecciation, and eventual brittle failure. These\u0000findings imply that non-hydrostatic stress has a significant influence on\u0000hydration rates and subsequent mechanical strength of rocks. This phenomenon\u0000is applicable across a wide range of geological environments in the Earth's\u0000crust and upper mantle.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"593 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74717512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analogue experiments on releasing and restraining bends and their application to the study of the Barents Shear Margin","authors":"R. Gabrielsen, Panagiotis Athanasios Giannenas, D. Sokoutis, E. Willingshofer, M. Hassaan, J. Faleide","doi":"10.5194/se-14-961-2023","DOIUrl":"https://doi.org/10.5194/se-14-961-2023","url":null,"abstract":"Abstract. The Barents Shear Margin separates the Svalbard and Barents Sea from the\u0000North Atlantic. During the break-up of the North Atlantic the plate tectonic\u0000configuration was characterized by sequential dextral shear, extension, and\u0000eventually contraction and inversion. This generated a complex zone of\u0000deformation that contains several structural families of overlapping and\u0000reactivated structures. A series of crustal-scale analogue experiments, utilizing a scaled and\u0000stratified sand–silicon polymer sequence, was used in the study of the\u0000structural evolution of the shear margin. The most significant observations for interpreting the structural\u0000configuration of the Barents Shear Margin are the following.\u0000 Prominent early-stage positive structural elements (e.g. folds, push-ups)\u0000interacted with younger (e.g. inversion) structures and contributed to a\u0000hybrid final structural pattern. Several structural features that were initiated during the early (dextral\u0000shear) stage became overprinted and obliterated in the subsequent stages. All master faults, pull-apart basins, and extensional shear duplexes\u0000initiated during the shear stage quickly became linked in the extension\u0000stage, generating a connected basin system along the entire shear margin at\u0000the stage of maximum extension. The fold pattern was generated during the terminal stage\u0000(contraction–inversion became dominant in the basin areas) and was\u0000characterized by fold axes striking parallel to the basin margins. These\u0000folds, however, strongly affected the shallow intra-basin layers.\u0000The experiments reproduced the geometry and positions of the major basins\u0000and relations between structural elements (fault-and-fold systems) as\u0000observed along and adjacent to the Barents Shear Margin. This supports the\u0000present structural model for the shear margin.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"49 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82740049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical modeling of stresses and deformation in the Zagros–Iranian Plateau region","authors":"Srishti Singh, Radheshyam Yadav","doi":"10.5194/se-14-937-2023","DOIUrl":"https://doi.org/10.5194/se-14-937-2023","url":null,"abstract":"Abstract. The Zagros orogenic system resulted due to collision of the Arabian plate with the Eurasian plate. The region is characterized by ocean–continent subduction and continent–continent collision, and the convergence velocity shows variations from east to west. Therefore, this region shows the complex tectonic stress and a wide range of diffuse or localized deformation between both plates. The in situ stress and GPS data are very limited and sparsely distributed in this region; therefore, we performed a numerical simulation of the stresses causing deformation in the Zagros–Iran region. The deviatoric stresses resulting from the variations in lithospheric density and thickness and those from shear tractions at the base of the lithosphere due to mantle convection were computed using thin-sheet approximation. Stresses associated with both sources can explain various surface observations of strain rates, SHmax, and plate velocities, thus suggesting a good coupling between lithosphere and mantle in most parts of Zagros and Iran. As the magnitude of stresses due to shear tractions from density-driven mantle convection is higher than those from lithospheric density and topography variations in the Zagros–Iranian Plateau region, mantle convection appears to be the dominant driver of deformation in this area. However, the deformation in the east of Iran is caused primarily by lithospheric stresses. The plate velocity of the Arabian plate is found to vary along the Zagros belt from the north–northeast in the southeast of Zagros to the northwest in northwestern Zagros, similarly to observed GPS velocity vectors. The output of this study can be used in seismic hazards estimations.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"12 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79612493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Selective inversion of rift basins in lithospheric-scale analogue experiments","authors":"A. Samsu, W. Gorczyk, T. Schmid, P. Betts, A. Cruden, E. Morton, Fatemeh Amirpoorsaeed","doi":"10.5194/se-14-909-2023","DOIUrl":"https://doi.org/10.5194/se-14-909-2023","url":null,"abstract":"Abstract. Basin inversion is commonly attributed to the reverse\u0000reactivation of basin-bounding normal faults. This association implies that\u0000basin uplift and inversion-related structures are mainly controlled by the\u0000frictional behaviour of pre-existing faults and associated damage zones. In\u0000this study, we use lithospheric-scale analogue experiments of orthogonal\u0000extension followed by shortening to explore how the flow behaviour of\u0000ductile layers underneath rift basins promote or suppress basin inversion.\u0000Our experiments show that the rheology of the ductile lower crust and\u0000lithospheric mantle, modulated by the imposed bulk strain rate, determine\u0000(1) basin distribution in a wide rift setting and (2) strain accommodation\u0000by fault reactivation and basin uplift during subsequent shortening. When\u0000the ductile layers deform uniformly during extension (i.e. stretching) and\u0000shortening (i.e. thickening), all of the basins are inverted. When\u0000deformation in the ductile layers is localised during extension (i.e.\u0000necking) and shortening (i.e. folding), only some basins – which are\u0000evenly spaced apart – are inverted. We interpret the latter as selective\u0000basin inversion, which may be related to the superposition of crustal-scale\u0000and lithospheric-scale boudinage during the previous basin-forming\u0000extensional phase and/or folding of the ductile layers during shortening.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75767197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The impact of seismic noise produced by wind turbines on seismic borehole measurements","authors":"F. Limberger, G. Rümpker, M. Lindenfeld, H. Deckert","doi":"10.5194/se-14-859-2023","DOIUrl":"https://doi.org/10.5194/se-14-859-2023","url":null,"abstract":"Abstract. Seismic signals produced by wind turbines can have an\u0000adverse effect on seismological measurements up to distances of several\u0000kilometres. Based on numerical simulations of the emitted seismic wave field,\u0000we study the effectivity of seismic borehole installations as a way to\u0000reduce the incoming noise. We analyse the signal amplitude as a function of\u0000sensor depth and investigate effects of seismic velocities, damping\u0000parameters and geological layering in the subsurface. Our numerical\u0000approach is validated by real data from borehole installations affected by\u0000wind turbines. We demonstrate that a seismic borehole installation with an\u0000adequate depth can effectively reduce the impact of seismic noise from wind\u0000turbines in comparison to surface installations. Therefore, placing the\u0000seismometer at greater depth represents a potentially effective measure to\u0000improve or retain the quality of the recordings at a seismic station.\u0000However, the advantages of the borehole decrease significantly with\u0000increasing signal wavelength.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86454487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced seismic characterization of a geothermal carbonate reservoir – insight into the structure and diagenesis of a reservoir in the German Molasse Basin","authors":"S. Wadas, Johanna F. Krumbholz, V. Shipilin, M. Krumbholz, D. Tanner, H. Buness","doi":"10.5194/se-14-871-2023","DOIUrl":"https://doi.org/10.5194/se-14-871-2023","url":null,"abstract":"Abstract. The quality of geothermal carbonate reservoirs is controlled by, for instance, depositional environment, lithology, diagenesis, karstification, fracture networks, and tectonic deformation. Carbonatic rock formations are thus often extremely heterogeneous, and reservoir parameters and their spatial distribution difficult to predict. Using a 3D seismic dataset combined with well data from Munich, Germany, we demonstrate how a comprehensive seismic attribute analysis can significantly improve the understanding of a complex carbonate reservoir. We deliver an improved reservoir model concept and identify possible exploitation targets within the Upper Jurassic carbonates. We use seismic attributes and different carbonate lithologies from well logs to identify parameter correlations. From this, we obtain a supervised neural-network-based 3D lithology model of the geothermal reservoir. Furthermore, we compare fracture orientations measured in seismic (ant-tracking analysis) and well scale (image log analysis) to address scalability. Our results show that, for example, acoustic impedance is suitable to identify reefs and karst-related dolines, and sweetness proves useful to analyse the internal reef architecture, whereas frequency- and phase-related attributes allow the detection of karst. In addition, reef edges, dolines, and fractures, associated with high permeabilities, are characterized by strong phase changes. Fractures are also identified using variance and ant tracking. Morphological characteristics, like dolines, are captured using the shape index. Regarding the diagenetic evolution of the reservoir and the corresponding lithology distribution, we show that the Upper Jurassic carbonate reservoir experienced a complex evolution, consisting of at least three dolomitization phases, two karstification phases, and a phase of tectonic deformation. We observe spatial trends in the degree of dolomitization and show that it is mainly facies-controlled and that karstification is facies- and fault-controlled. Karstification improves porosity and permeability, whereas dolomitization can either increase or decrease porosity. Therefore, reservoir zones should be exploited that experienced only weak diagenetic alteration, i.e. the dolomitic limestone in the upper part of the Upper Jurassic carbonates. Regarding the fracture scalability across seismic and well scales, we note that a general scalability is, due to a combination of methodological limitations and geological reasons, not possible. Nevertheless, both methods provide an improved understanding of the fracture system and possible fluid pathways. By integrating all the results, we are able to improve and adapt recent reservoir concepts, to outline the different phases of the reservoir's structural and diagenetic evolution, and to identify high-quality reservoir zones in the Munich area. These are located southeast at the Ottobrunn Fault and north of the Munich Fault close to the Nymphenburg Fau","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"26 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83079289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electrical conductivity of anhydrous and hydrous gabbroic melt under high temperature and high pressure: implications for the high-conductivity anomalies in the mid-ocean ridge region","authors":"Mengqi Wang, Lidong Dai, Haiying Hu, Ziming Hu, Chenxin Jing, Chuanyu Yin, Song-Shan Luo, Jinhua Lai","doi":"10.5194/se-14-847-2023","DOIUrl":"https://doi.org/10.5194/se-14-847-2023","url":null,"abstract":"Abstract. The electrical conductivity of gabbroic melt with four different water\u0000contents (i.e., 0 %, 2.59 wt %, 5.92 wt %, and 8.32 wt %) was measured at\u0000temperatures of 873–1373 K and pressures of 1.0–3.0 GPa using a YJ-3000t\u0000multi-anvil high-pressure apparatus and Solartron-1260 impedance\u0000spectroscopy analyzer. At a fixed water content of 2.59 wt %, the\u0000electrical conductivity of the sample slightly decreased with increasing\u0000pressure in the temperature range of 873–1373 K, and its corresponding\u0000activation energy and activation volume were determined as 0.87 ± 0.04 eV and −1.98 ± 0.02 cm3 molec.−1, respectively. Under the\u0000certain conditions of 873–1373 K and 1.0 GPa, the electrical conductivity of\u0000the gabbroic melts tends to gradually increase with a rise in water content\u0000from 0 wt % to 8.32 wt %, and the activation enthalpy decreases from 0.93 to\u00000.63 eV accordingly. Furthermore, functional relation models for the\u0000electrical conductivity of gabbroic melts with variations of\u0000temperature, pressure, and water content were constructed at high-temperature\u0000and high-pressure conditions. In addition, the dependence\u0000relation of the electrical conductivity of melts with the degree of\u0000depolymerization was explored under conditions of four different water\u0000contents at 1373 K and 1.0 GPa, and three previously available reported\u0000results on those of representative calc-alkaline igneous rock melts (i.e.,\u0000dacitic melt, basaltic melt, and andesitic melt) were compared in detail. In\u0000combination with our presently acquired electrical\u0000conductivity data on gabbroic melt with four different water contents and\u0000the available data on polycrystalline olivine, the electrical conductivity\u0000of a gabbroic melt–olivine system with variation of the volume percentage of\u0000anhydrous and hydrous melts was successfully constructed by using the\u0000typical Hashin–Shtrikman upper-bound model. In light of the electrical\u0000conductivity of the gabbroic melt–olivine system with previous magnetotelluric (MT) results,\u0000we find that anhydrous and hydrous gabbroic melts can be employed to\u0000reasonably interpret the high-conductivity anomalies in the Mohns Ridge of\u0000the Arctic Ocean.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"150 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79504133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The link between Somalian Plate rotation and the East African Rift System: an analogue modelling study","authors":"F. Zwaan, G. Schreurs","doi":"10.5194/se-14-823-2023","DOIUrl":"https://doi.org/10.5194/se-14-823-2023","url":null,"abstract":"Abstract. The East African Rift System (EARS) represents a major\u0000tectonic feature that splits the African continent between the Nubian Plate\u0000situated to the west and the Somalian Plate to the east. The EARS comprises\u0000various rift segments and microplates and represents a key location for\u0000studying rift evolution. Researchers have proposed various scenarios for the\u0000evolution of the EARS, but the impact of continent-scale rotational rifting,\u0000linked to the rotation of the Somalian Plate, has received only limited\u0000attention. In this study we apply analogue models to explore the dynamic\u0000evolution of the EARS within its broader rotational-rifting framework. Our\u0000models show that rotational rifting leads to the lateral propagation of\u0000deformation towards the rotation axis, which reflects the general southward\u0000propagation of the EARS. However, we must distinguish between the\u0000propagation of distributed deformation, which can move very rapidly, and\u0000localized deformation, which can significantly lag behind the former. The\u0000various structural-weakness arrangements in our models (simulating the\u0000pre-existing lithospheric heterogeneities that localize rifting along the\u0000EARS) lead to a variety of structures. Laterally overlapping weaknesses are\u0000required for localizing parallel rift basins to create rift pass structures,\u0000leading to the rotation and segregation of microplates such as the Victoria\u0000Plate in the EARS, as well as to the simultaneous north- and southward\u0000propagation of the adjacent Western Rift. Additional model observations\u0000concern the development of early pairs of rift-bounding faults flanking the\u0000rift basins, followed by the localization of deformation along the axes of\u0000the most developed rift basins. Furthermore, the orientation of rift\u0000segments with respect to the regional (rotational) plate divergence affects\u0000deformation along these segments: oblique rift segments are less wide due to\u0000a strike-slip deformation component. Overall, our model results generally\u0000fit the large-scale present-day features of the EARS, with implications for\u0000general rift development and for the segregation and rotation of the\u0000Victoria Plate.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"24 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79040211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A borehole trajectory inversion scheme to adjust the measurement geometry for 3D travel-time tomography on glaciers","authors":"S. Hellmann, M. Grab, C. Patzer, A. Bauder, H. Maurer","doi":"10.5194/se-14-805-2023","DOIUrl":"https://doi.org/10.5194/se-14-805-2023","url":null,"abstract":"Abstract. Cross-borehole seismic tomography is a powerful tool to investigate the subsurface with a very high spatial resolution. In a set of boreholes,\u0000comprehensive three-dimensional investigations at different depths can be conducted to analyse velocity anisotropy effects due to local changes\u0000within the medium. Especially in glaciological applications, the drilling of boreholes with hot water is cost-efficient and provides rapid access to\u0000the internal structure of the ice. In turn, movements of the subsurface such as the continuous flow of ice masses cause deformations of the\u0000boreholes and complicate a precise determination of the source and receiver positions along the borehole trajectories. Here, we present a three-dimensional inversion scheme that considers the deviations of the boreholes as additional model parameters next to the common velocity\u0000inversion parameters. Instead of introducing individual parameters for each source and receiver position, we describe the borehole trajectory with\u0000two orthogonal polynomials and only invert for the polynomial coefficients. This significantly reduces the number of additional model parameters and\u0000leads to much more stable inversion results. In addition, we also discuss whether the inversion of the borehole parameters can be separated from the\u0000velocity inversion, which would enhance the flexibility of our inversion scheme. In that case, updates of the borehole trajectories are only\u0000performed if this further reduces the overall error in the data sets. We apply this sequential inversion scheme to a synthetic data set and a field\u0000data set from a temperate Alpine glacier. With the sequential inversion, the number of artefacts in the velocity model decreases compared to a\u0000velocity inversion without borehole adjustments. In combination with a rough approximation of the borehole trajectories, for example, from\u0000additional a priori information, heterogeneities in the velocity model can be imaged similarly to an inversion with fully correct borehole coordinates. Furthermore, we discuss the advantages and limitations of our approach in the context of an inherent seismic anisotropy of the medium and extend our algorithm to consider an elliptic velocity anisotropy. With this extended version of the algorithm, we analyse the interference between a seismic anisotropy in the medium and the borehole coordinate adjustment. Our analysis indicates that the borehole inversion interferes with seismic velocity anisotropy. The inversion can compensate for such a velocity anisotropy. Based on the modelling results, we propose considering polynomials up to degree 3. For such a borehole trajectory inversion, third-order polynomials are a good compromise between a good\u0000representation of the true borehole trajectories and minimising compensation for velocity anisotropy.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"39 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76366751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural framework and timing of the Pahtohavare Cu ± Au deposits, Kiruna mining district, Sweden","authors":"L. Logan, Ervin Veress, J. Andersson, O. Martinsson, Tobias E. Bauer","doi":"10.5194/se-14-763-2023","DOIUrl":"https://doi.org/10.5194/se-14-763-2023","url":null,"abstract":"Abstract. As part of the larger mineral systems approach to\u0000Cu-bearing mineralization in northern Norrbotten, this study utilizes\u0000structural geology to set the classic Pahtohavare Cu ± Au deposits\u0000into an up-to-date tectonic framework. The Pahtohavare Cu ± Au\u0000deposits, situated only 5 km southwest of the Kiirunavaara world-class iron\u0000oxide–apatite (IOA) deposit, have a dubious timing, and their link to IOA\u0000formation is not constrained. The study area contains both epigenic Cu ± Au (Pahtohavare) and iron oxide–copper–gold (IOCG; Rakkurijärvi)\u0000mineral occurrences which are hosted in bedrock that has been folded and\u0000bound by two shear zones trending northeast to southwest and northwest to southeast to the east and southwest,\u0000respectively. Structural mapping and petrographic investigation of the area\u0000reveal a noncylindrical, SE-plunging anticline. The cleavage measurements\u0000mirror the fold geometry, which characterizes the fold as F2 associated\u0000with the late phase of the Svecokarelian orogeny. Porphyroclasts with pressure\u0000shadows, mylonitic fabrics, and foliation trails in porphyroblasts indicate\u0000S0/S1 is a tectonic fabric. The epigenetic Pahtohavare Cu ± Au mineralization sits in brittle–ductile structures that cross-cut an\u0000earlier foliation and the F2 fold, indicating that the timing of the\u0000deposits occurred syn- to post-F2 folding, at least ca. 80 Myr after\u0000the Kiirunavaara IOA formation. A 3D model and cross-sections of the\u0000Pahtohavare–Rakkurijärvi area and a new structural framework of the\u0000district are presented and used to suggest that the shear zones bounding the\u0000area are likely reactivated early structures that have played a critical\u0000role in ore formation in the Kiruna mining district.\u0000","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"1 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82983437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}