Journal of Structural Geology最新文献

{"title":"Simultaneous determination of deviatoric stress tensors from polyphase calcite twin data: improvement and application","authors":"Yehua Shan ,&nbsp;Jian Zheng","doi":"10.1016/j.jsg.2025.105534","DOIUrl":"10.1016/j.jsg.2025.105534","url":null,"abstract":"<div><div>It is a challenge to obtain the meaningful solution of deviatoric stress tensors from polyphase calcite twin data measured in multi-deformed rocks. Our paper advances current approaches that simultaneously determine stresses from polyphase twin data. Key refinements include the selection of the dimensionless stress space, the estimation of the dimensionless critical resolved shear stress (<span><math><mrow><msub><mover><mi>τ</mi><mo>‾</mo></mover><mi>c</mi></msub></mrow></math></span>), the definition of the stress criterion including <span><math><mrow><msub><mover><mi>τ</mi><mo>‾</mo></mover><mi>c</mi></msub></mrow></math></span>, and the exclusion or inclusion of incompatible untwinned planes (IU). The improved simultaneous-determination method (ISDM) is applied to three series of two–three-phase IU-free synthetic datasets generated under imposed stresses. Stress results demonstrate that the ISDM is accurate in principal stress direction, stress ratio, and <span><math><mrow><msub><mover><mi>τ</mi><mo>‾</mo></mover><mi>c</mi></msub></mrow></math></span>, although the ISDM including IU is a little more accurate than the ISDM excluding IU. For two-phase equally-sized synthetic datasets, the ISDM excluding IU is generally more accurate than existing similar methods. Applying both the ISDM and an existing similar method to a natural dataset reveals that the ISDM excluding IU yields the most reasonable stress solution.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105534"},"PeriodicalIF":2.9,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852671","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":"Intracontinental deformation and paleo-stress fields of the lower yangtze region during the late Mesozoic: implications for the tectonic evolution of South China","authors":"Beihang Zhang ,&nbsp;Jin Zhang ,&nbsp;Heng Zhao ,&nbsp;Jie Hui ,&nbsp;Yaqi Yang ,&nbsp;Yiping Zhang ,&nbsp;Alimu Adina ,&nbsp;Hai Jiang","doi":"10.1016/j.jsg.2025.105532","DOIUrl":"10.1016/j.jsg.2025.105532","url":null,"abstract":"<div><div>The late Mesozoic intracontinental deformation in South China preserves rich insights into continental evolution, with close link to subduction and collision processes along the eastern margin of the Eurasian Plate. The Lower Yangtze Region, located in the northeastern part of South China, underwent complex intracontinental deformation during the late Mesozoic, making it a key area for understanding the tectonic evolution of East Asia. Through detailed field investigation of representative outcrops and structural analysis of fault-slip data from the regional faults, this study reconstructs the late Mesozoic deformation sequence and paleo-stress fields in the Lower Yangtze Region. Our new data, combined with published results, suggest that the Lower Yangtze Region experienced a three-stage tectonic evolution from the Late Jurassic to early Late Cretaceous, characterized by alternating contractional and extensional tectonic events. The first stage, contractional deformation from the Late Jurassic to early Early Cretaceous, was controlled by NW-SE contractional stress, generating sinistral strike-slip motion along the Tan-Lu Fault, the dextral strike-slip motion along the Chuhe Fault and Yangtze River Fault, and top-to-west thrusting of the Maoshan Fault. This contractional deformation is interpreted as being related to the westward low-angle subduction of the Paleo-Pacific Plate beneath the Eurasian Plate. The second stage is NW-SE extension during the Early Cretaceous, associated with a series of high-angle normal faults, which is correlated with the rollback of the Paleo-Pacific Plate. The third stage is another episode of contractional deformation that resulted in a tectonic inversion controlled by nearly N-S contraction during late Early Cretaceous to early Late Cretaceous. This contraction led to the sinistral strike-slip motion of the regional faults and was associated with a set of conjugate strike-slip faults. The oblique collision between the Okhotomorsk Block and the Eurasian Plate serves as the geodynamic driver for this contraction event. Comparative structural analysis reveals distinct deformation patterns between the Lower Yangtze Region and other areas of South China during the Late Jurassic to early Early Cretaceous. Under the same NW-SE contraction, the Lower Yangtze Region exhibited predominant strike-slip motion along the major faults, whereas other areas of South China developed NNE-SSW-striking thrust-and-fold deformation. This disparity is possibly caused by the unique tectonic position and pre-existing basement faults of the Lower Yangtze Region. Due to the obstruction of the rigid craton (i.e., the North China Craton), the crustal materials underwent lateral extrusion towards the northeast along the pre-existing faults, accommodating the continuous contraction that occurred during the Late Jurassic to early Early Cretaceous.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105532"},"PeriodicalIF":2.9,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144840643","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":"Mapping fault architecture from depth to surface: integrating microseismicity and structural geology in low-strain Apennine regions","authors":"Giusy Lavecchia ,&nbsp;Francesco Brozzetti ,&nbsp;Simone Bello ,&nbsp;Rita de Nardis","doi":"10.1016/j.jsg.2025.105518","DOIUrl":"10.1016/j.jsg.2025.105518","url":null,"abstract":"<div><div>High-resolution microearthquake data provide a powerful window into active fault architecture from depth to surface in slowly deforming regions with sparse instrumental seismicity. We integrate microseismic clusters from enhanced catalogs with detailed structural mapping to reconstruct the 3D geometry of seismogenic extensional faults in the Latium-Abruzzi sector of central Italy. Investigated earthquake clusters align geometrically and kinematically with known and newly mapped normal faults showing evidence of Late Quaternary activity. The 3D model depicts a set of SW-to-SSW-dipping, non-planar faults with an average dip of ∼55° (Sora, San Donato Val di Comino, Villavallelonga, and Pescasseroli). Their cut-off depths deepen NNE-ward, from ∼7 to ∼14 km, suggesting an underlying basal discontinuity dipping∼30–35°. Microseismic patches at the roots of these faults are mostly elongated along dip rather than along strike. This unusual geometry suggests a stress release pattern governed by iso-oriented anisotropic roughness and corrugations on the basal discontinuity, which may focus upward fluid migration and trigger earthquakes along hangingwall splays. Stress inversion reveals a persistent NE–SW tensional stress field consistent across geological and instrumental timescales. An empirical magnitude-area relationship, accounting for both epistemic uncertainty in scaling laws and areal variability of fault surfaces, yields maximum magnitudes between 6.0 and 6.5, consistent with the regional seismotectonic framework. These findings provide new constraints on fault connectivity, stress distribution, and fluid-fault interactions, and help identifying potentially seismogenic sources that may remain unrecognized when geological and seismic data are considered separately.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105518"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828062","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":"Pore space properties and permeability of solution surfaces in Mesozoic shallow-water carbonates, southern Apennines, Italy","authors":"C. Manniello ,&nbsp;V. La Bruna ,&nbsp;E. Michie ,&nbsp;R.E.B. Araùjo ,&nbsp;F.H.R. Bezerra ,&nbsp;D. Faulkner ,&nbsp;M. Allen ,&nbsp;X.M. Morais ,&nbsp;G. Prosser ,&nbsp;F. Agosta","doi":"10.1016/j.jsg.2025.105520","DOIUrl":"10.1016/j.jsg.2025.105520","url":null,"abstract":"<div><div>Focusing on the Mesozoic and Eocene carbonate samples from the Viggiano Mt. and Raparo Mt., Southern Apennines of Italy, we examine the role of solution surfaces on the present-day porosity and permeability. Carbonate lithofacies include mudstones, packstones, grainstones, and rudstones and gas-porosimetry measurements show effective porosity up to 5 %. The value is mainly due to the secondary porosity localized along microfractures and within the rough bed-parallel and rough bed-oblique solution surfaces, contrary to what was found in the smooth bed-parallel ones, showing that roughness can control pore localization. NMR (Nuclear Magnetic Resonance) results indicate that the former group of solution surfaces include vugs characterized by subspherical to tubular shapes (pore throat r &lt; 3 μm), and low aspect ratios (r &lt; 2), forming pores with low sensitivity to compression. The microfractures form capillary porosity (r ≈ 1 μm) and are characterized by high aspect ratios (r &gt; 2), typical of pores with high sensitivity to compression. Permeability measurements at room pressure reveal that samples with visible microfractures are characterized by values up 2 order magnitude greater than of those with only visible solution surfaces, showing that the pore connectivity is controlled by opening-mode, sub-mm scale microfractures. At confining pressures greater than 25 MPa, both fracture- and stylolite dominated samples show similar values of permeability, indicating that at depths larger than ca. 1 km, the rough stylolite localize effective porosity that may enhance the along-solution surface fluid flow in carbonates.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105520"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810158","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":"Residual stress in diopside: insight into localized transient high stress in seismogenic faults in the lower crust, Lofoten, Norway","authors":"Hugo W. van Schrojenstein Lantman ,&nbsp;Patricia A. Carvalho ,&nbsp;David Wallis ,&nbsp;Luca Menegon","doi":"10.1016/j.jsg.2025.105517","DOIUrl":"10.1016/j.jsg.2025.105517","url":null,"abstract":"<div><div>Pseudotachylytes in the metamorphosed anorthosites of the Lofoten archipelago, Norway, preserve a record of seismic rupture in dry lower crust at temperatures and pressures of 650–750 °C and 0.8 GPa. Transient gigapascal-level stresses are suggested from microstructural evidence, however such high stresses have not been quantified. In this contribution, we combine microstructural analysis with the mapping of heterogeneity in residual stress in diopside from a lower-crustal pseudotachylyte from Nusfjord (Lofoten) using high-angular resolution electron backscatter diffraction (HR-EBSD). We aim to elucidate the deformation processes that led to this residual stress and to its spatial heterogeneity in the diopside grains.</div><div>The diopside contains micro-to nanoscale deformation twins within 3 mm of the fault and in clasts in the pseudotachylyte. Within clasts, the diopside lattice strongly undulates, indicating crystal plasticity at high driving stress. Residual stress heterogeneity ranges between ∼200 MPa and ∼800 MPa for in-plane normal stress, with greater values occurring closer to and in the pseudotachylyte. This trend is not apparent for the in-plane shear stress, which has residual stress heterogeneity between ∼150 and ∼250 MPa, not correlating with distance to the fault. The greatest residual stresses are present in a clast that exhibits lattice distortion resulting from dislocation glide. Mechanical twins, lattice undulations, and the distribution patterns of residual stress are truncated by coseismic fractures, suggesting that the microstructures and residual stress are the result of stress build-up prior to slip.</div><div>Given the extreme spatial localization of the residual stress heterogeneity, we conclude that it results from deformation occurring during earthquake rupture propagation. Despite high temperatures during frictional heating, thermal pressure did not contribute significantly to the residual stress. The behaviour of diopside as a stress recorder is influenced by mechanical twins: stress build-up in diopside may have partially dissipated by the formation of twins, and twins also appear to affect the residual stress, in particular shear stress.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105517"},"PeriodicalIF":2.9,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810157","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":"Multi-phase deformation in the Qixingtai region of Western Shandong Province: insights into the Neoarchean tectonic evolution of the eastern North China Craton","authors":"Shuhui Zhang ,&nbsp;Jian Zhang ,&nbsp;Guochun Zhao ,&nbsp;Qihang Wu ,&nbsp;Chen Zhao ,&nbsp;Xiaoguang Liu ,&nbsp;Changqing Yin ,&nbsp;Jiahui Qian ,&nbsp;Mingtao He","doi":"10.1016/j.jsg.2025.105516","DOIUrl":"10.1016/j.jsg.2025.105516","url":null,"abstract":"<div><div>The Neoarchean era marks a pivotal period in Earth's tectonic evolution and continental crust formation. In this context, crustal architecture and structural patterns serve as key indicators for reconstructing Neoarchean geodynamic processes. The Western Shandong Province (WSP) granite-greenstone belt, located in the North China Craton (NCC), preserves well-exposed Neoarchean rock assemblages and provides valuable insights into the Neoarchean tectonics. In this study, we conducted systematic geological mapping and detailed structural analysis, integrated with LA-ICP-MS zircon U-Pb geochronology, in the Qixingtai region of the WSP. Three stages of compressional deformation (D1 to D3) were identified. The earliest deformation D1, predating ∼2663 Ma, is characterized by NW-SE-trending, sub-vertically penetrative S1 foliation in early Neoarchean supracrustal rocks and TTG rocks, indicating an initial NE-SW compressional regime. This was followed by a regional extension during 2.60-2.55 Ga and deposition of the Shancaoyu Formation during 2.55-2.52 Ga. The subsequent deformation D2 (∼2520-2514 Ma) progressively overprinted earlier structures and generated NW-SE-trending upright isoclinal folds in late Neoarchean supracrustal and TTG rocks, indicating a consistent and prolonged compressive stress field. The last deformation D3, occurring around ∼2500 Ma, resulted in the development of ductile shear zones of variable scales along the major lithological boundaries and generated regional L-S tectonites with near-vertical foliation and horizontal lineation. Our results suggest that the WSP experienced a long-lasting NE–SW compressive stress field throughout the Neoarchean but lacks diagnostic features of typical subduction or collisional belts. Combined with previous studies, we propose a tectonic model for the tectonic evolution of the Qixingtai area. This area initially developed from an oceanic plateau in the early Neoarchean, experienced regional extension in the middle Neoarchean, and ultimately underwent extensive magmatism and horizontal shortening during the late Neoarchean.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105516"},"PeriodicalIF":2.9,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144750594","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":"Thermo-mechanical intrusion-wall rock interaction and granite emplacement mechanisms of the Peninsula granite at the Sea Point contact, Cape Town, South Africa","authors":"Musa Mhlanga,&nbsp;Russell Bailie,&nbsp;Jürgen Reinhardt","doi":"10.1016/j.jsg.2025.105513","DOIUrl":"10.1016/j.jsg.2025.105513","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Sea Point contact, Cape Town, South Africa exposes the intrusive contact between the ∼540 Ma S-type Peninsula Granite and the ∼560–555 Ma metasedimentary rocks of the Malmesbury Group of the Pan-African Saldania Belt. The western Saldania Belt was subjected to low-grade greenschist facies metamorphism and deformation during the ∼560–540 Ma Saldanian orogeny. The Peninsula Granite intruded as a series of numerous granite sheets which made use of the pre-existing country rock anisotropy in order to propagate. These are the steeply dipping S&lt;sub&gt;0&lt;/sub&gt; bedding due to folding during the Saldanian orogeny, and a steeply dipping axial planar S&lt;sub&gt;2&lt;/sub&gt; foliation to the F&lt;sub&gt;2&lt;/sub&gt; folds developed during the dominant D&lt;sub&gt;2&lt;/sub&gt; deformation. Magma overpressure relative to tensile stresses in the country rock and regional NE-SW-orientated compressional stresses allowed intrusion of variably crystal-laden magma along the anisotropies. The granitic sheets are commonly concentrated in the hinge zones of F&lt;sub&gt;2&lt;/sub&gt; folds, where structural traps facilitated magma “trapping.” Filter pressing at the tail of the magma-filled hydrofracture caused closing during magma through-flow resulting in the entrapping of magmatic crystals, most notably K-feldspar megacrysts, in the wall rock as well as xenoliths dislodged during magma infiltration and stoping, and possibly magma flow. Magma stresses have brought about the alignment of K-feldspar megacrysts as well as the long axes of xenoliths parallel to the orientation of granite sheets and wall rock septa in the complex lit-par-lit zone and adjacent to the contact. A degree of assimilation (and possibly partial melting) is evident in the rounded shapes of xenoliths, but, more notably in mixed zones where there are gradational contacts not only between different granite types, reflecting multiple granite pulse intrusion, but also between the granites and wall rock, giving rise to hybrid granites. Xenoliths with remnant S&lt;sub&gt;0&lt;/sub&gt; and S&lt;sub&gt;2&lt;/sub&gt; were picked up and rotated during magma flow, with some embedded in the wall rock during filter pressing. The timing of granite intrusion relative to deformation is evident from examining contact-metamorphic cordierite porphyroblasts and their inclusions. The variation of inclusion patterns relative to the external foliation indicate that thermal metamorphism and, by implication, magma intrusion, occurred from early D&lt;sub&gt;2&lt;/sub&gt;- to late-D&lt;sub&gt;3&lt;/sub&gt; deformation with continued flattening of the schist matrix leading to an enveloping of the porphyroblasts by the S&lt;sub&gt;2&lt;/sub&gt; foliation. The intrusion thus was accompanied by progressive deformation and tightening of the F&lt;sub&gt;2&lt;/sub&gt; folding. Some granites, notably the coarse-grained megacrystic granite, crosscut other granite types and intruded late-to post-tectonic. Magma loading led to the development of a shallowly dipping, widely spaced S&lt;sub&gt;3&lt;/sub&gt; crenulation. Subsequent magma injections led t","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105513"},"PeriodicalIF":2.9,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144750592","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":"Strain localization in quartzo-feldspathic mylonites from Patos shear zone revealed by EBSD data","authors":"Matheus Alves da Silva ,&nbsp;Leonardo Lagoeiro ,&nbsp;Carolina Cavalcante ,&nbsp;Paola Ferreira Barbosa","doi":"10.1016/j.jsg.2025.105514","DOIUrl":"10.1016/j.jsg.2025.105514","url":null,"abstract":"<div><div>Understanding how strain is localized and concentrated in the mid-crust is critical to geological research. Investigating the microstructure and texture of quartzo-feldspathic mylonites is essential in this context. The Patos shear zone (PSZ), stretching ∼600 km long and responsible for the deformation of the paleoproterozoic basement in the Borborema Province under varying temperature conditions, is a significant shear zone for exploration. Combining techniques, including optical and scanning electron microscopy and Electron Backscatter Diffraction (EBSD) our research focused on quartzo-feldspathic mylonites to comprehend the solid-state processes responsible for strain localization within the Patos shear zone. As materials undergo uplift and deformation transition from a submagmatic to a solid-state flow, strain is concentrated within increasingly narrow zones. Our results demonstrated that after melt solidification, biotite-rich layers at temperatures exceeding 650 °C become weaker domains that accommodate strain through dislocation creep in feldspar, biotite and to a lesser extent in quartz, with the activation of prism-[c] slip system. During late reactivation, under upper greenschist/lower amphibolite facies, dislocation creep, strain-induced myrmekitization, solution-precipitation mechanisms are the dominant mechanisms for grain-size reduction in feldspar, with the resulting fine-grained matrix deforming via dislocation-accommodated and fluid-assisted grain boundary sliding (GBS). Quartz undergoes recrystallization as it transitions from grain boundary migration to subgrain rotation, with the activation of prism-&lt;a&gt; slip system. At temperatures below 450 °C, in the southern Patos shear zone, quartz ribbons experience bulging recrystallization with the activation of prism-&lt;a&gt; and rhomb&lt;a&gt; slip systems. Feldspar porphyroclasts undergo fracturing, myrmekitization and dissolution-precipitation creep. Rock rheology is controlled by fine-grained polyphase aggregates deforming via Dislocation-accommodated GBS. Finally, our study highlights the role of discontinuities during low-temperature deformation, such as the contact between rheologically contrasting layers and transgranular fractures, which serve as a precursor that led to shear zones nucleation in the northern block of the Patos shear zone.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105514"},"PeriodicalIF":2.9,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144723563","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":"Mineral heterogeneity dominates the tensile failure mode of Eastern Himalayan Gneiss","authors":"Shijie Liu ,&nbsp;Hengxing Lan ,&nbsp;C. Derek Martin ,&nbsp;Langping Li ,&nbsp;Han Bao","doi":"10.1016/j.jsg.2025.105515","DOIUrl":"10.1016/j.jsg.2025.105515","url":null,"abstract":"<div><div>As two fundamental fracture types in rock engineering, tension and shear fractures are commonly considered to operate under different stress conditions. However, abundant recent research shows that the microscale heterogeneity of rocks leads to the possibility of microscale tensile and shear fracturing under any stress state. In particular, localised stress concentrations and tensile fractures caused by mineral heterogeneity under compressive stress have been widely studied. However, the heterogeneity-induced processes involved in the shear fracture under direct tension conditions remain ambiguous. In this study, a micro-direct tensile test was used to comprehensively reveal the process and mechanism by which mineral heterogeneity leads to shear fracture in the gneiss of the eastern Himalayas under direct tension. Microscopic observation of the failure process under direct tension, normalised crack initiation and propagation stress, and transverse strain dilation caused by shear behaviour indicate that gneiss with an exceptional anisotropy angle may exhibit more pronounced shear sliding during progressive tensile failure processes. Micro shear sliding significantly increased the strength of the gneiss and changed its tensile strain, elastic modulus, and progressive failure process, which were determined using a direct tension test. Depending on the degree of frictional sliding, the tensile failure mode of gneiss can be divided into three modes: tensile, hybrid, and shear. Mineral heterogeneity influences the pattern of crack propagation through potential fracture planes, altering the crack propagation stress, significantly affecting the mobilisation of frictional strength, and resulting in a progressive transition between the three modes. The observation of shear sliding under direct tension caused by heterogeneity emphasises the importance of mineral-scale heterogeneity in evaluating the tensile strength of anisotropic rocks.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105515"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696806","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":"Pressure-temperature-time deformation of an Ediacaran-Cambrian foreland fold-and-thrust belt: the Southern Espinhaço Front, Araçuaí Orogen","authors":"Henrique C. Joncew ,&nbsp;Ginaldo A.C. Campanha ,&nbsp;Melina C.B. Esteves ,&nbsp;Frederico M. Faleiros ,&nbsp;Leonardo E. Lagoeiro ,&nbsp;Klaus Wemmer ,&nbsp;Ruy A.C. Vasconcelos ,&nbsp;Bruno V. Ribeiro ,&nbsp;Mathias Hueck","doi":"10.1016/j.jsg.2025.105512","DOIUrl":"10.1016/j.jsg.2025.105512","url":null,"abstract":"<div><div>To reconstruct the tectonic evolution of a foreland fold-and-thrust belt, a multi-method approach was carried out involving field-based structural observations, strain quantification, analyses of quartz crystallographic textures, fluid inclusions and illite crystallinity (IC), and in situ muscovite Rb-Sr dating and K-Ar dating of fine fractions of white mica. The studied area encompasses the Southern Espinhaço Front in Serra do Cipó, Brazil, marking the boundary between the Foreland Domain (FLD) of the São Francisco Craton (west) and the Fold-and-Thrust Domain (FTD) of the Araçuaí-West Congo Orogen (east). In this area, the Mesoproterozoic Espinhaço Supergroup was thrust over the Ediacaran-Cambrian Bambuí Group during the Brasiliano-Pan-African orogeny. All structural features indicate west-verging tectonics, with oblate strain ellipsoids, suggesting flattening strain and volume loss. Quartz crystallographic textures indicate primarily rhomb &lt;a&gt; dislocation glide for the larger granulometric fractions (&gt;100 μm), with finer grains experiencing dissolution-precipitation creep. Primary, aqueous fluid inclusions hosted in syn-tectonic veins indicate local intra-basinal fluid circulation. Deformation conditions ranges were 300–410 °C and 1.7–6.0 kbar in the FLD, and 385–450 °C and 2.8–8.0 kbar in the FTD. Rb-Sr muscovite dating suggests a metamorphic peak at 549 ± 17 Ma. K-Ar ages for &lt;2 μm mica were 510–496 Ma in the FLD and 476–456 Ma in the FTD, and &lt;0.2 μm mica dated at 432.6 ± 7.5 Ma. These results indicate progressive crustal wedge thickening under a critical taper model, driving deformation and basal detachment propagation into the foreland accompanied by exhumation.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105512"},"PeriodicalIF":2.9,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144750593","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}