Journal of Structural Geology最新文献

{"title":"Microstructural evolution of micaceous mylonites","authors":"Katherine Billings,&nbsp;Philip Skemer","doi":"10.1016/j.jsg.2025.105555","DOIUrl":"10.1016/j.jsg.2025.105555","url":null,"abstract":"<div><div>In crustal shear zones, the grain size and geometric arrangement of mica is observed to evolve significantly with strain. The transition from tabular, interconnected mica layers to a well-mixed fine-grained ultramylonitic microstructure is inferred to reduce rock viscosity. This evolution is predicted to play an important role in the strength of the crust, particularly at plate boundaries. However, the mechanisms of mica layer disaggregation and phase mixing at high strains have not been widely explored. In this study, we conducted deformation experiments (up to shear strains of <span><math><mrow><mi>γ</mi><mo>&gt;</mo><mn>100</mn></mrow></math></span>) on synthetic composites of mica (fluorphlogopite) and either calcite or fluorite in the Large Volume Torsion Apparatuses (LVTs) at Washington University in St. Louis. Experiments were performed at T = 765 °C, P = 1.5 GPa, and strain rates of ∼1x10⁻⁴ s⁻¹. Deformation microstructures were analyzed using optical and electron microscopy and electron backscatter diffraction (EBSD). Microstructural evolution is sensitive to shear strain (γ) but largely insensitive to the composited material. Mica grain size is reduced through brittle mechanisms and mixing may be enhanced by phase boundary sliding. Interconnected layers of mica disaggregate and are fully mixed with the composited material at <span><math><mrow><mi>γ</mi><mo>&gt;</mo><mn>50</mn></mrow></math></span>. This sequence of deformation processes is also inferred from the complementary analysis of specimens from the Kuckaus Mylonite Zone in the Namaqua Metamorphic Complex in southwestern Namibia. This process of mica grain size reduction and phase mixing may contribute to the transition from mylonite to ultramylonite in high temperature crustal shear zones.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105555"},"PeriodicalIF":2.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106204","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":"Influence of tectonic regime superposition on damage zone structures in a basin-boundary fault, Jatobá basin, NE Brazil","authors":"D.L. Vasconcelos ,&nbsp;F. Balsamo ,&nbsp;L.C. Palhano ,&nbsp;F.C.C. Nogueira ,&nbsp;F.H.R. Bezerra ,&nbsp;F.O. Marques ,&nbsp;R.G. Oliveira ,&nbsp;W.E. Medeiros ,&nbsp;R.A. Fuck ,&nbsp;A.C. Tavares ,&nbsp;R.R.S. Dantas","doi":"10.1016/j.jsg.2025.105552","DOIUrl":"10.1016/j.jsg.2025.105552","url":null,"abstract":"<div><div>We integrated magnetic, gravity, and structural data to investigate the Ibimirim Fault and the evolution of its damage zones within the Jatobá Basin, NE Brazil. Our findings indicate that the magnetic anomalies observed within the Pernambuco and Cruzeiro do Nordeste shear zones are consistent with the strike of the Ibimirim Fault in the study area. Integrated with structural analysis of the Precambrian fabric and rift fault, we suggest that the basement fabric influences the position and geometry of the Ibimirim Fault. Gravity inversion revealed that the Jatobá Basin contains three depocenters, with the main one situated in the central part of the Ibimirim Fault. A fault throw analysis indicates that the Ibimirim Fault comprises three main fault segments, with this study focusing on the area where the central and eastern segments connect. In this overstep area, extensional and compressional fault sets occur in the fault damage zone. The compressional structures crosscut and displace the extensional older structures. The superposition of these structures enhances structural fracturing connectivity without increasing the damage zone width. Paleostress characterization shows extensional structures with sub-vertical σ1 and sub-horizontal σ3 (05/061). In contrast, compressional structures have sub-vertical σ3 and sub-horizontal σ1 (03/349), indicating a non-colinear basin inversion likely driven by far-field stresses from the Andes and the Mid-Atlantic Ridge. This research highlights the intricate interplay between tectonic regime superposition and the evolution of extensional and compressional structures within the same fault damage zone, with significant implications for understanding the formation of sub seismic structures in these regions.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105552"},"PeriodicalIF":2.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106203","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":"Interaction between diagenesis and faulting in sandstone reservoirs: Inferences from the Groningen gas field","authors":"Job P.B. Arts ,&nbsp;Dallyn Rodrigues ,&nbsp;Fadi H. Nader ,&nbsp;Martyn R. Drury ,&nbsp;Liviu C. Matenco ,&nbsp;Ernst Willingshofer ,&nbsp;André R. Niemeijer","doi":"10.1016/j.jsg.2025.105554","DOIUrl":"10.1016/j.jsg.2025.105554","url":null,"abstract":"<div><div>We investigated the progressive diagenetic evolution of fault zones in the Rotliegend reservoir of the Groningen gas field (NE Netherlands) through microstructural and petrological analysis of cataclastic bands and the only retrieved fault gouge from the reservoir. Our observations show that authigenic quartz, ferroan dolomite, siderite and anhydrite are spatially associated with the presence of faults in the reservoir.</div><div>The uneven distribution of syntaxial quartz overgrowths in the host rock suggests that silica was readily available in the reservoir, but that quartz precipitation was inhibited by coatings and slow-growing euhedral faces. Quartz cementation was preferentially concentrated in cataclastic bands, where fresh fracture surfaces provided favourable nucleation sites.</div><div>Anhydrite and siderite cements are concentrated in dilatant fractures in cataclastic bands or in the host rock adjacent to it. Based on their association with dilatant fractures and the required sources for sulphates and reducing fluids, respectively, we interpret that they were introduced by extrinsic, fault associated fluids, during a late stage of the diagenetic history.</div><div>The preferential quartz cementation in cataclastic zones suggests that many Groningen faults experienced cementation-related strengthening, while this process was inhibited in the clay-rich fault cores as observed in the BIR-01 well, implying that fault reactivation is most likely to occur within the weak fault core.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105554"},"PeriodicalIF":2.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145060301","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":"Richard Lisle in Oviedo (Spain): Contributions to the analysis of folding – a review","authors":"Fernando Bastida ,&nbsp;Jesús Aller ,&nbsp;Nilo C. Bobillo-Ares ,&nbsp;Francisco J. Fernández ,&nbsp;Omar Menéndez","doi":"10.1016/j.jsg.2025.105553","DOIUrl":"10.1016/j.jsg.2025.105553","url":null,"abstract":"<div><div>The work carried out by Richard Lisle, stemming from his stay in Oviedo and his integration into the fold analysis group at the local university, addressed a wide range of topics concerning fold geometry and kinematics. Regarding 2D fold geometry, Richard led the development of a method to relate the various classification schemes based on fold fitting functions, using a parameter defined as the normalized area bounded by the folded surface profile. Non-cylindrical folds were analysed based on the properties of developable surfaces and curvature analysis. In the field of kinematics, special attention was given to the neutral surface folding, which led to the distinction between two modes: “parallel tangential longitudinal strain” and “equiareal tangential longitudinal strain”. A method was also developed to estimate the total bulk shortening associated with the formation of flattened parallel folds. The 2D kinematics of various fold types was explored through numerical simulations, based on the displacement laws governing different folding mechanisms. This methodology was applied to the study of chevron folds, folded oblique surfaces, asymmetric folds, recumbent folds, and similar folds. The investigation led to the resolution of certain problems related to rock deformation and resulted in the description of a new deformation mode: “rotation shear”. The study of these topics also involved the development of computational tools to automate and facilitate the strain calculations. The formation mechanisms of several structures associated with folding were likewise examined, including crenulation cleavage, so-called “saw-tooth structures”, curved veins related to folds, and cleavage in pre-existing folds. Finally, we evaluate the impact of this body of work, its limitations, and future prospects for extending the research, particularly by using the results obtained as a foundation for dynamic modelling.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105553"},"PeriodicalIF":2.9,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050129","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":"Shear zone folds: Structural analysis and interpretation","authors":"G.I. Alsop,&nbsp;D.J. Condon","doi":"10.1016/j.jsg.2025.105544","DOIUrl":"10.1016/j.jsg.2025.105544","url":null,"abstract":"<div><div>Shear zones and associated folds form an important category of structures that are widely developed in the internal portions of orogenic belts. The analysis of such folds is crucial as they can be used to help determine kinematics, bulk strain and deformation histories of crustal-scale shear zones as well as influencing fluid flow and potential mineralisation. Our case study focuses on a Caledonian shear zone in NW Ireland that is marked by NW-directed crustal thickening (D1) that is followed by a later phase (D2) of SE-directed gravity-driven extensional collapse. We provide a detailed analysis of mesoscopic folds and fabrics formed during this greenschist-facies extension in order to answer some general questions including how to distinguish folds with hinges that initiate parallel to transport versus those folds that have rotated towards shear, the control that larger folds may have upon the geometry and orientation of smaller folds, and the influence that lithology plays in the evolution of shear zone folds. Our study comprises a mixed fold and fabric data set derived from a complex combination of i) <em>flow perturbation folds</em> with hinges that have initiated sub-parallel to transport, ii) <em>sheath folds</em> with hinges that have rotated towards transport during intense progressive shear, and iii) <em>spiral folds</em> with hinges that initiate normal to transport but fail to rotate as they roll and tighten. These mesoscopic folds form across a range of scales with smaller folds forming at a variety of angles, and in some cases transecting larger fold hinges indicating a non-Pumpellyan or incongruous relationship. Competent psammites host more open folds with hinges at higher angles to transport when compared to weaker pelites that contain tighter folds at variable angles to shear. Lithology and scale are therefore critical factors in controlling shear zone folds, with natural data sets commonly dominated by smaller-scale (&lt;10 cm) folds that are more prevalent and easier to measure at outcrop. A consequence of this bias in recording data is that the amount of fold rotation (and hence bulk strain) may be over-estimated. A further complication is that fold pairs preserve more open upper hinges compared to tighter lower hinges that are closer to underlying detachments, meaning that the exact position of the hinge within fold pairs should be routinely recorded. The flattening of buckle fold hinges within competent psammites reflects the influence of gravity-driven deformation with an absolute sense of top-down-to the SE shear, which we interpret as being focussed into the shear zone during orogenic collapse.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105544"},"PeriodicalIF":2.9,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050119","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":"Going with the flow — Changes of vorticity control gold enrichment in Archean shear zones (Shebandowan Greenstone Belt, Superior Province, Canada)","authors":"Tobias Stephan ,&nbsp;Noah J. Phillips ,&nbsp;Hanna Tiitto ,&nbsp;Adrian Perez ,&nbsp;Michael Nwakanma ,&nbsp;Robert Creaser ,&nbsp;Pete Hollings","doi":"10.1016/j.jsg.2025.105542","DOIUrl":"10.1016/j.jsg.2025.105542","url":null,"abstract":"<div><div>Archean orogenic gold deposits are commonly hosted in brittle-ductile shear zones, where gold is locally remobilized and reprecipitated due to changes in physio-chemical conditions. However, in Archean rocks of the Superior Craton, these shear zones are often sparsely exposed and inferred primarily through spatial correlation, hence these shear zone architectures remain poorly understood. Here, we apply geochronology, kinematic analysis, and vorticity analysis techniques to study the Shebandowan Greenstone Belt in Northern Ontario, Canada. Geochronological results from zircon U-Pb CA-ID-TIMS and molybdenite Re-Os NTIMS dating yielded an age of 2717.35 ± 0.48 Ma for a proximal felsic intrusion and 2708 ± 12 Ma for auriferous and molybdenite-bearing vein mineralization, respectively. Field observations and regional age data indicate that both mineralization and intrusive activity predate deformation. Spatial interpolation of ductile foliation orientations reveals that gold mineralization is spatially associated with abrupt changes in shear zone orientation. Vorticity analysis — including rigid porphyroclast and crystallographic vorticity analysis — shows that these changes induce strain partitioning in releasing and restraining bends. These observed localized deflections in shear zone strike are attributed to the competency contrast between the old, feldspar-rich, isotropic, and syenitic plutonic bodies (rheologically stronger) and gold-bearing, intermediate metavolcanic and diorite units (rheologically weaker). Transitions from non-coaxial to coaxial flow dominated areas appear to have localized fluid pathways, allowing for fluid migration and gold precipitation during deformation. Quantifying deflections of shear zones adjacent to rigid geological bodies, combined with analyzing the deformation flow types, represents a powerful and cost-effective tool for gold exploration in granite-greenstone belts.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"201 ","pages":"Article 105542"},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145010724","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":"Revisiting surface ruptures of the 1955 Zheduotang earthquake (Mw 7.1) in eastern tibet: kinematic implications on the southern Xianshuihe fault zone","authors":"Guangchun Xu ,&nbsp;Junjie Ren ,&nbsp;Yufa Liu ,&nbsp;Chao Ma ,&nbsp;Yaning Yi ,&nbsp;Yanwu Lv ,&nbsp;Xiwei Xu","doi":"10.1016/j.jsg.2025.105540","DOIUrl":"10.1016/j.jsg.2025.105540","url":null,"abstract":"<div><div>Surface ruptures associated with large historical earthquakes provide essential insights into earthquake magnitudes and the kinematics of their seismogenic faults. In 1955, a major earthquake struck Zheduotang Village, Kangding City, producing surface ruptures along the Zheduotang fault, a segment of the southern Xianshuihe fault zone. The magnitude of this event remains a topic of debate, with estimates ranging from M6.6 to M7.5, primarily due to discrepancies in the interpretation of its associated surface ruptures. This study synthesizes previous research on the surface ruptures of the 1955 Zheduotang earthquake and presents new field data, including high-resolution unmanned aerial vehicle (UAV)-based topographic surveys, trenching, and lichenometry in the epicentral region. Analysis of surface rupture freshness, faulting event chronology from trenching, and lichen size measurements collectively support a ∼55 km-long surface rupture zone, corresponding to a moment magnitude (M_w) of ∼7.1 for the 1955 earthquake. Offset glacial landform analysis reveals a late Quaternary left-lateral slip rate of ∼2.5–3.0 mm/yr in the southern segment of the Zheduotang fault, which is lower than the previously documented ∼4 mm/yr in the northern segment. Deformed landforms and surface ruptures indicate that the fault trends NNW and exhibits predominantly left-lateral strike-slip motion in its northern segment, while the southern segment trends NW and includes a notable normal faulting component. Our findings suggest that the Zheduotang fault defines the southwestern boundary of the Bamei-Kangding releasing stepover zone within the southern Xianshuihe left-lateral strike-slip fault zone. These results enhance the understanding of seismic hazards and the tectonic kinematics along the eastern boundary of the Tibetan Plateau.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105540"},"PeriodicalIF":2.9,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144906887","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 architecture, tectonic stacking and extensional reactivation of nappe contacts in the southern Middle Tuscan Ridge, Inner Northern Apennines orogenic belt (Italy)","authors":"Andrea Brogi ,&nbsp;Enrico Capezzuoli ,&nbsp;Amalia Spina ,&nbsp;Martina Zucchi ,&nbsp;Chiara Montemagni ,&nbsp;Federico Lucci","doi":"10.1016/j.jsg.2025.105541","DOIUrl":"10.1016/j.jsg.2025.105541","url":null,"abstract":"<div><div>Interpreting tectonic stacking patterns and the nature of contacts between tectonic units is a major challenge in orogenic belts, particularly when mafic rock slices are embedded within the tectonic stack. These occurrences raise fundamental questions about their origin and the tectonic processes responsible for their emplacement. Such complexities, which characterize several orogenic belts worldwide, are especially prominent in the inner Northern Apennines orogenic belt (Italy). This belt is characterized by abrupt metamorphic discontinuities, local omissions of portions of the tectonic stack, significant stratigraphic gaps within individual tectonic units and contains discontinuous mafic bodies within the nappe pile. These features point to a polyphase tectonic evolution, which over the last decades has led to a range of hypotheses concerning the Neogene evolution of the inner Northern Apennines. Testing these models requires integrated structural, petrological, and stratigraphic investigations. This study presents structural, kinematic and stratigraphic data on detailed field mapping in the southern Middle Tuscan Ridge (southern Tuscany), a key area within the inner Northern Apennines. Our results document a polyphase extensional evolution characterised by the sequential development of normal faults during post-orogenic deformation (∼19–20 Ma). Based on this evidence, we propose an updated tectonic model that integrates the geometry, timing, and evolution of extensional structures in this part of the chain. The model refines the regional tectonic framework and provides a basis for further investigation into the metamorphic evolution, the chronology of tectonic events, and the origin of mafic bodies within continental units. On a broader scale, it offers a reference for interpreting post-collisional extensional settings in other orogenic belts worldwide.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105541"},"PeriodicalIF":2.9,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144917418","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":"Naturally deformed polymineralic rocks provide quantitative rheological information","authors":"Kyrsten L. Johnston ,&nbsp;Laurel Goodwin ,&nbsp;Basil Tikoff ,&nbsp;Evan Earnest ,&nbsp;Christine Gopon ,&nbsp;Thomas G. Blenkinsop","doi":"10.1016/j.jsg.2025.105539","DOIUrl":"10.1016/j.jsg.2025.105539","url":null,"abstract":"<div><div>Polyphase rocks are more common than monomineralic rocks, but their rheologies are less well constrained. We utilize a combination of strain markers, natural variations in mineral content, and microstructural observations to quantify the rheology of deformed and metamorphosed turbidite sequences from the Eastern Fold Belt in the Mount Isa Inlier, Queensland, Australia. At the outcrop scale, continuous deflection of quartz-rich veins records changes in shear strain magnitude that correspond to variations in mineralogy. Larger deflections (higher strains) are recorded in biotite- and muscovite-rich (phyllosilicate) domains relative to stratigraphically lower quartz- and feldspar-rich (quartzofeldspathic) domains. X-ray diffraction analyses of cores from a representative turbidite sequence show an increase in mica content (12–52 %) and a decrease in quartz and feldspar content (86–38 %) with increasing stratigraphic height. Electron backscatter diffraction analyses show a measurable crystallographic preferred orientation in quartz, indicating intracrystalline deformation in a quartzofeldspathic domain, which is absent in the adjacent phyllosilicate domain. Back-scattered electron images document evidence of solution-precipitation creep and grain-boundary sliding in a phyllosilicate domain, indicating deformation was accommodated by intercrystalline processes. Despite similar differential stress recorded by both domains, relative strain rates, calculated from ratios of shear strain, increase with mica content. A conceptual model that characterizes strain partitioning in layered systems quantitatively demonstrates the dependence of bulk deformation on the relative thicknesses and viscosity ratios of mineralogical domains.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105539"},"PeriodicalIF":2.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144907786","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":"An optimization approach to algebraic Rf/ϕ strain analysis","authors":"Yehua Shan","doi":"10.1016/j.jsg.2025.105535","DOIUrl":"10.1016/j.jsg.2025.105535","url":null,"abstract":"<div><div>In algebraic <em>R</em>_<em>f</em>/<em>ϕ</em> strain analysis, there is a lack of the uncertainty of strain caused by, as common in measured post-strain objects, the violation of the assumption of the independence between the major-axis directions and axial ratios of pre-strain objects. A new <em>R</em>_<em>f</em>/<em>ϕ</em> strain method is developed to reduce this uncertainty. The method minimizes the sum of the <em>K</em>-th power of the negative determinant of the tensor difference between each post-strain object and the unknown strain. The method for <span><math><mrow><mi>K</mi><mo>=</mo><mn>1</mn></mrow></math></span> yields an analytical solution of strain, equivalent to existing algebraic estimators of strain. Both synthetic datasets and real examples are used to validate the method for varying <em>K</em> values of 1–10. The strain results illustrate that the method decreases in standard error and tends to increase in accuracy with an increasing <em>K</em>. The variation of the estimated strain with <em>K</em> is helpful to appraise the violation of the independence assumption.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105535"},"PeriodicalIF":2.9,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895001","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}