Journal of Structural Geology最新文献

{"title":"Reconstructing the framework of the Paleo-Pacific Plate: A synthetic review","authors":"Sanzhong Li ,&nbsp;Yong-Fei Zheng ,&nbsp;Yanhui Suo","doi":"10.1016/j.jsg.2025.105505","DOIUrl":"10.1016/j.jsg.2025.105505","url":null,"abstract":"<div><div>The Paleo-Pacific Ocean Basin would evolve from the Panthalassa and develop ancient plates such as Paleo-Pacific, Farallon and Phoenix. Multilines of geological and geophysical evidence indicate that a new-born plate, named the Pacific Plate, would initially develop at 190 Ma among these three plates in the Paleo-Pacific Ocean Basin, but it did not take shape until 55 Ma when the Paleo-Pacific Plate would finally disappear on the East Asian continental margin. Therefore, the Paleo-Pacific Plate and the Pacific Plate would co-evolve or co-exist from 190 Ma to 55 Ma in the Paleo-Pacific Ocean Basin. The ocean basin after the complete disappearance of the Paleo-Pacific Plate at 55 Ma is the Pacific Ocean Basin as presently seen. Geologically, the Pacific Ocean Basin is marked by the initial formation of the plate configuration on the current Pacific seafloor in the Mesozoic. Therefore, when did the Paleo-Pacific Plate begin in the Paleo-Pacific Ocean Basin? When was the Paleo-Pacific Plate subducted beneath the East Asian continental margin? How would its appearance and disappearance are spatiotemporally recorded in geology? What are its geological effects during its subduction beneath the East Asian continental margin? Although there are numerous studies dealing with the formation and evolution of the Paleo-Pacific Plate, the results have brought many big debates on its composition and structure. Some scholars refer to the Paleo-Pacific Plate differently, leading to some great difficulties in academic exchanges. There are three mainstream viewpoints: the Paleo-Pacific Plate is either the Kula Plate, or the Izanagi Plate, or a collage of many plates. Although the Paleo-Pacific Plate existed as a mysterious on Earth in the Mesozoic, a large number of geological observations indicate that its evolution is closely related to the tectonic evolution of the East Asian continental margin in this period. Therefore, it is necessary to recognize and reconstruct the configuration of the Paleo-Pacific Plate and its tectonic effects on the East Asian continental margin. This paper attempts to systematically summarize the previous observations and interpretations of the Paleo-Pacific Plate, to distinguish between the concepts of the Kula Plate, the Izanagi Plate and the Paleo-Pacific Plate in different study stages, and to systematically explore various differences in plate reconstruction since the proposal of the Paleo-Pacific Plate. Based on the current progresses on plate tectonics, this paper also summarizes the relevant geological records of the Paleo-Pacific Plate, including the continental margin accretion of oceanic plateaus, island arc basalt-like magmatic rocks and terrane-collage accretion. The time of its subduction initiation, geometric evolution and spatial range changes are explored, and its tectonic evolutionary history is reconstructed. Finally, remaining problems are presented for the future research.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105505"},"PeriodicalIF":2.6,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144670571","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":"Kinematic interpretation of the Cañamares shear zone (central Iberian zone, Iberian Massif): from late Variscan strike-slip tectonics to Alpine deformation","authors":"Diana Moreno-Martín ,&nbsp;Carlos Fernández ,&nbsp;Rubén Díez Fernández ,&nbsp;Gerardo de Vicente","doi":"10.1016/j.jsg.2025.105504","DOIUrl":"10.1016/j.jsg.2025.105504","url":null,"abstract":"<div><div>The Cañamares shear zone is located at the eastern end of the Spanish-Portuguese Central System, in the Central Iberian Zone of the Iberian Massif. It is a dextral transpressive structure, generated during the third Variscan deformation stage (D₃: 318-300 Ma), which was later reworked during the Permian and by Alpine tectonics. Once the local effects of later phases have been eliminated, the kinematic analysis of the Cañamares shear zone shows that it is a structure due to a monoclinic to slightly triclinic flow, with a vorticity dominated by the simple-shearing component (<em>W</em>_k &gt; 0.81). The convergence direction of the blocks separated by the shear zone would have been N160°E to N-S. The convergence direction calculated for the Cañamares shear zone differs from that of other D₃ shear zones of the Iberian Massif. A comparison between these vectors would help to better understand the complexities of the final phases of the Variscan Orogeny in Iberia. However, the Cañamares shear zone lies at the core of an Alpine mega-fold and its current orientation does not probably reflect its primary geometry.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105504"},"PeriodicalIF":2.6,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633287","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":"Deformation mechanisms of compressional overlapping area in strike-slip fault zone: Insights from experimental simulation","authors":"Jingjing Zhang ,&nbsp;Lingli Guo ,&nbsp;Sanzhong Li ,&nbsp;Wei Tao ,&nbsp;Yuntao Ji ,&nbsp;Yanshuang Guo ,&nbsp;Shujuan Zhao ,&nbsp;Jiaxuan Zhang ,&nbsp;Guangzeng Wang","doi":"10.1016/j.jsg.2025.105503","DOIUrl":"10.1016/j.jsg.2025.105503","url":null,"abstract":"<div><div>As an intense deformation region, the compressional overlapping areas of strike-slip faults play a crucial and significant role in influencing fault propagation, seismic activity, and the formation and distribution of hydrocarbon reservoirs. Hence, enhancing the comprehension of detailed microscopic deformation mechanisms lays the foundation for a better understanding of the macroscopic deformation, constituting the core issue of this study. Compressional en échelon fault model experiments were conducted, combining with acoustical and optical measurements to simulate fault interactions and mechanical coupling within fault systems. The experimental results manifest that three distinct episodes of derived faults were observed during the interaction of pre-existing faults. Firstly, a group of derived faults extends from the ends of the overlapping area, conjugating with the pre-existing en échelon faults. Secondly, the fault consisting of a series of secondary fractures propagates from the ends of the overlapping area towards the interior, leading to a complete destruction of the overlapping area. Thirdly, another group of faults extends from the ends of the overlapping area, forming a rhombic region in conjunction with the two pre-existing faults. Furthermore, the analysis of the strike-slip rate distribution along two en échelon faults showed significant heterogeneity. Specifically, the segments with relatively low strike-slip rate were inferred to be locked zones, which are likely to act as nucleation points for future emergent deformation events. These simulation results contributed to understanding the issues such as the mechanical coupling between Garlock and San Andreas fault systems, the linkage fault development in the branching zones of the North Anatolian Fault Zone, and the kinematic intersection geometry between the Danghenan Shan and Altyn Tagh faults.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105503"},"PeriodicalIF":2.6,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144655258","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 and stratigraphic control on fluid flow in the Mt. Conero anticline, Italy: An analog for offshore resource reservoirs in fold-and-thrust belts","authors":"Luca Smeraglia ,&nbsp;Luca Aldega ,&nbsp;Stefano M. Bernasconi ,&nbsp;Andrea Billi ,&nbsp;Sabina Bigi ,&nbsp;Eduardo di Marcantonio ,&nbsp;Andrea Fiorini ,&nbsp;Andrew Kylander-Clark ,&nbsp;Eugenio Carminati","doi":"10.1016/j.jsg.2025.105502","DOIUrl":"10.1016/j.jsg.2025.105502","url":null,"abstract":"<div><div>We investigate the structural control on paleofluid flow in the Mt. Conero anticline, Italy, located in the frontal part of the Apennines fold-and-thrust belt. This anticline can be considered as an exhumed analog for buried anticlines in the Adriatic offshore, currently exploited for hydrocarbons and potential geothermal reservoirs or CO₂ storage sites in the future. By integrating field structural analyses, stable and clumped isotope geochemistry of carbonates, and U-Pb geochronology, we demonstrate that the structural evolution of the Mt. Conero anticline in a carbonate-siliciclastic succession is marked by: (1) pre-orogenic normal faulting and veining during foreland flexure, (2) layer-parallel shortening during early contraction, with the development of <em>en-echelon</em> bed-perpendicular conjugate veins and stylolites, (3) syn-folding thrusting and strike-slip faulting, and (4) transtensional faulting during fold exhumation and extensional collapse. Fluid circulation took place in a closed system, predominantly involving formation water, such as marine pore water trapped during diagenesis. Effective sealing by clay-rich formations overlying the fractured, permeable carbonates, coupled with low displacement strike-slip faults and thrusts, prevented the ingress of meteoric fluids and/or the upward migration of deep (hydrothermal) fluids. Limited mixing between formation and meteoric waters in a semi-closed system was observed during fold exhumation and extensional collapse. Our results show that folds in the frontal part of offshore fold-and-thrust belts are likely to retain fluids trapped during diagenesis due to the preservation of sealing layers. This suggests that such anticlines can preserve hydrocarbon reservoirs and are excellent candidates for CO₂ storage due to their low leakage potential, offering also good storage capacity for geothermal fluids. These results may represent a benchmark for offshore anticlines in the frontal part of other offshore fold-and-thrust belts, particularly those with carbonate anticlines overlain by clay-rich sealing layers.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105502"},"PeriodicalIF":2.6,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144687535","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":"Microstructure and CPO evolution of dynamically recrystallized olivine during complex deformation conditions: a full-field numerical modeling approach","authors":"Yuanchao Yu ,&nbsp;Albert Griera ,&nbsp;Enrique Gomez-Rivas ,&nbsp;Paul D. Bons ,&nbsp;Daniel Garcia-Castellanos ,&nbsp;Baoqin Hao ,&nbsp;Ricardo A. Lebensohn ,&nbsp;Cassandra Seltzer ,&nbsp;Maria-Gema Llorens","doi":"10.1016/j.jsg.2025.105500","DOIUrl":"10.1016/j.jsg.2025.105500","url":null,"abstract":"<div><div>The rheological properties of mantle rocks are strongly dependent on their crystallographic preferred orientation (CPO). Olivine CPO, defined by the orientation of seismically fast [100] axes parallel to flow direction, is also thought to be a dominant contributor to seismic anisotropy in the Earth's upper mantle. However, the amount of deformation needed to overprint a new CPO on a pre-existing fabric and the impact of the inherited CPOs on the transient microstructure evolution, remain unknown. This study employs a full-field numerical approach (VPFFT-ELLE) to explore the dynamic recrystallization and microstructural evolution of olivine polycrystalline aggregates under complex deformation conditions. We test four combinations of successive pure shear and simple shear boundary conditions. Findings indicate that inherited CPOs influence subsequent deformation in a manner dependent on the kinematic relationship between successive stages. In all cases, a minor strain increment (ε ∼0.3–0.6) is sufficient to erase the previous microstructure and CPO. However, when deformation conditions change dramatically (<em>e.g.</em>, stretching direction changes orthogonally), the intensity of the new CPO developed is significantly lower and strain distribution are specially altered. During a transient strain stage, pre-existing microstructures undergo extensive reworking, especially when deformation conditions are changed dramatically, such as switching from simple shear to a pure shear condition with a parallel shortening direction relative to the stretching direction. We estimate the significance of these results in interpreting observations of seismic velocity anisotropy, concluding that P-wave seismic anisotropy is significantly and positively correlated with the evolution of olivine CPO with deformation history. This research underscores the transient nature of microstructural rearrangement in olivine aggregates and the necessity for caution in interpreting seismic anisotropy in regions with complex deformation histories, as inherited CPOs can influence current fabric development and induce deviation to the present deformation conditions.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105500"},"PeriodicalIF":2.6,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144579243","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":"Fine geometric structures and characteristics of present-day activity of the Tianshui–Baoji segment of the West Qinling Fault, northeastern margin of the Tibetan Plateau","authors":"Ruihuan Su ,&nbsp;Daoyang Yuan ,&nbsp;Zhao Wu ,&nbsp;Jinchao Yu ,&nbsp;Yunsheng Yao ,&nbsp;Hong Xie ,&nbsp;Lijun Zhang ,&nbsp;Yameng Wen ,&nbsp;Hao Sun ,&nbsp;Yanwen Chen ,&nbsp;Hongqiang Li","doi":"10.1016/j.jsg.2025.105499","DOIUrl":"10.1016/j.jsg.2025.105499","url":null,"abstract":"<div><div>Accurately delineating the fine geometric structures of active faults and assessing their present-day activity are of paramount importance for studying regional fault tectonics and evaluating seismic risk. The West Qinling Fault (WQLF) is situated in a critical zone where material from the Tibetan Plateau is extruded towards the northeast, and the fine geometric structures, kinematic characteristics, and present-day activity of its eastern segment (Tianshui–Baoji segment) can provide important insights into the mechanisms of structural transition at the termination of strike-slip faults and the mode of material expansion in the plateau. In this study, the spatial distribution of the Tianshui–Baoji segment and the characteristics of present-day activity are systematically investigated through detailed interpretations of high-resolution satellite images, digital elevation models (DEMs), unmanned aerial vehicle (UAV) images, geological and geomorphological field surveys, and isotopic dating techniques. The results indicate that the Tianshui–Baoji segment, which begins as a single fault, gradually splays into multiple branching faults towards the east. Both the main fault and these branches have remained active since the Late Pleistocene and even during the Holocene, thus warranting attention to the seismic risk potential in the eastern segment of the WQLF, particularly at its termination. Moreover, the splay of the Tianshui–Baoji segment has led to the gradual divergence of the fault activity of the component to the east, reducing the maximum magnitude of seismic events at the fault terminus and resulting in significant differences in the seismic recurrence intervals between the eastern segment and the central segments of the WQLF (Zhangxian segment, Gangu–Wushan segment).</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105499"},"PeriodicalIF":2.6,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596818","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 simulation of fault damage zones and their impact on the structural evolution of Pre-salt carbonate reservoirs","authors":"Pedro A.L.P. Firme ,&nbsp;Francisco C. Dias ,&nbsp;Roberto Quevedo ,&nbsp;Deane Roehl ,&nbsp;Bruno R.B.M. Carvalho ,&nbsp;Jorge A.B. Souza","doi":"10.1016/j.jsg.2025.105498","DOIUrl":"10.1016/j.jsg.2025.105498","url":null,"abstract":"<div><div>Our work employs numerical models to investigate the impacts of the early and late faulting stages on the development of fault damage zones (DZs) in conditions analogous to Pre-salt. DZs exhibit contrasts in geomechanical and petrophysical properties compared to the surrounding host rock. Numerous studies have explored the characterization of DZs by modeling fault formation processes. Most Brazilian Pre-salt reservoirs have early faults associated with depositional tectonic development overprinted by late faults that formed at greater depths. Both faulting events can markedly affect the present-day DZ widths. Previous studies have investigated the development of DZ during the early faulting stage. However, the late faulting stage and its impact on DZs have not been explored. Thus, our goal is to investigate the impact of both the early and late faulting stages in the structural evolution of DZs in carbonate rocks through geomechanical analyses. The results indicate that burial during the late faulting stage increases confinement and enhances the integrity of the rock far from the DZ, while the DZs triggered during the early fault formation remains unchanged. In addition, for the late faulting stage, we assess the role of fault roughness on the DZ by adopting friction coefficients to represent smooth or rough surfaces. The results show that rough fault surfaces contribute to lower fault displacements.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105498"},"PeriodicalIF":2.6,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633298","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":"Reading the marbles: Calcite decodes strain distribution during exhumation of high-pressure metamorphic rocks (Ios Island, Cyclades)","authors":"K.A. Tsourtis,&nbsp;N. Gerogiannis,&nbsp;E. Aravadinou,&nbsp;P. Xypolias","doi":"10.1016/j.jsg.2025.105497","DOIUrl":"10.1016/j.jsg.2025.105497","url":null,"abstract":"<div><div>We present new calcite microstructural, petrofabric, and grain size data from high-pressure marbles to investigate spatio-temporal variations of deformation within the exhumed Cycladic Blueschist Unit (CBU) on Ios Island. Early exhumation of the CBU, from eclogite-to blueschist-facies conditions, was accompanied by the development of the mesoscopic foliation and isoclinal folds. Our results indicate static recrystallization during blueschist-facies conditions, evidenced by coarse columnar calcite grains oriented at high angles to the pre-existing foliation. Continued exhumation involved top-to-the-SSE shearing, localized at the base of the unit, as indicated by the dynamic recrystallization of columnar calcite via subgrain rotation. A subsequent reversal to top-to-the-NNW shearing caused intense deformation across the CBU from blueschist-to greenschist-facies conditions, producing a wide range of recrystallized grain sizes (∼500–∼20 μm). During the final stages of NNW-directed shearing, deformation localized at the top of the CBU within foliation-parallel bands, with differential stresses from 26 to &gt;64 MPa, forming fine-grained (∼30 μm), nearly uniform recrystallized calcite through subgrain rotation and bulging recrystallization. These findings underscore the previously underestimated significance of foliation-parallel, NNW-directed shearing during ductile exhumation of the CBU on Ios Island and highlight the critical role of high-pressure calcite marbles in unraveling these tectonic processes.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105497"},"PeriodicalIF":2.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517019","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":"Microstructure of garnet in calc-silicate rocks from Cheongsong, South Korea: Effects of fluid and deformation","authors":"Seokyoung Han ,&nbsp;Sejin Jung ,&nbsp;Ji-Hoon Kang ,&nbsp;Haemyeong Jung","doi":"10.1016/j.jsg.2025.105496","DOIUrl":"10.1016/j.jsg.2025.105496","url":null,"abstract":"<div><div>Garnet is a common mineral found in metamorphic rocks of various lithologies in the continental basement, subducting slab, and upper mantle. In such environments, fluid–rock interactions, metamorphism, and deformation occur dynamically, disrupting garnet chemical distribution and its microstructure. Investigating the garnet microstructure in fluid-rich environments provides key insights into the role of fluids in the deep crust. In this study, the garnet microstructure in calc-silicate rocks from Cheongsong, South Korea, was analyzed to elucidate its petrofabric evolution during contact metamorphism and concurrent plastic deformation. Three garnet types were categorized based on their microstructures using scanning electron microscopy, electron backscattered diffraction, and electron microprobe analysis. Type I garnet is characterized by garnet clusters formed by multiple nucleation and coalescence at the preferred nucleation site. Type II garnet shows intense deformation due to dislocation creep. Type III garnet exhibits chemically zoned structures with light-colored garnet surrounding dark fragmented garnet, interpreted as fractured relict garnet partly dissolved and replaced by Fe-richer garnet. Transmission electron microscopy images of types II and III garnet showed evidence of dislocation creep. Deformation temperatures were estimated using the quartz c-axis fabric opening angle thermometer, ranging from 708 to 741 ± 50 °C. Considering the water-rich environment and metamorphic mineral assemblage, the actual deformation temperature of calc-silicate rock is suggested to be approximately 650–700 °C, consistent with garnet plastic deformation conditions. The nucleation and deformation processes of garnet suggested in this study provide insights into the petrogenesis and tectonometamorphic processes in contact-metamorphosed rocks within fluid-rich environments.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105496"},"PeriodicalIF":2.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549773","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":"Deformation and magnetic fabrics in isoclinal folds of the Variscan Pyrenees","authors":"B. Oliva-Urcia ,&nbsp;T. Román-Berdiel ,&nbsp;P. Clariana ,&nbsp;R. Soto ,&nbsp;E. Izquierdo-Llavall ,&nbsp;A. Casas-Sainz","doi":"10.1016/j.jsg.2025.105495","DOIUrl":"10.1016/j.jsg.2025.105495","url":null,"abstract":"<div><div>Magnetic fabrics are used as strain markers since they reflect the orientation-distribution of grains in a rock. In this work we analyzed, from the point of view of anisotropy of magnetic susceptibility (at low-temperature and room temperature), Devonian (29 sites) and Ordovician-Silurian (3 sites) sedimentary rocks in the Pyrenean Axial Zone, totalling 611 samples. The main target is to determine the strain in relation to the Variscan (polyphased) and Alpine orogenies in limestones and shales. The magnetic information also derives from thermomagnetic curves, acquisition of the isothermal remanent magnetization (IRM) and coercivity of the remanence analyses, together with hysteresis loops and stepwise thermal demagnetization of induced IRM in 3 axes techniques. The analyses of magnetic properties were complemented with optical microscopy observations and calcimetries. In two of the sample areas (Sen and Llisat valleys), the minimum axes of the magnetic susceptibility ellipsoid (k_min axes) are mostly perpendicular to bedding whereas in the other two (Zinqueta valley and near Posets peak area), a more developed tectonic fabric is found: the k_min axes are not completely perpendicular to bedding, and the magnetic susceptibility ellipsoid relates to the foliation plane. Different minerals carry a concordant magnetic fabric with pyrrhotite, magnetite (ferromagnetic <em>s.l.)</em> and phyllosilicates (paramagnetic), and little influence of calcite grains (diamagnetic). The magnetic fabric is interpreted to form at the early stages of the Variscan deformation, prior to the dextral transpression synchronous with granite emplacement that characterizes the late stages of the Variscan Orogeny. However, contact metamorphism and associated fluid circulation can enhance or obliterate the primary magnetic fabric.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105495"},"PeriodicalIF":2.6,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517531","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}