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[Display omitted] • Crustal thickness data reveals a new Davis Strait Proto-Microcontinent. • Plate modelling and crustal thickness data indicate a Pre-Ungava transform margin. • Seismic and plate kinematic analyses links transpression with continental cleaving. A prolonged period of rifting and seafloor spreading between Greenland and North America formed the Labrador Sea and Baffin Bay oceanic basins, connected by the Davis Strait. However, disagreement exists regarding the exact plate motions between Greenland and Canada, as well as the tectonic evolution of the Davis Strait, with previous models unable to explain the origin of anomalously thick continental crust within the seaway. Here, we present a new plate tectonic reconstruction of Greenland's separation from Canada, constrained by a new comprehensive set of mid-ocean ridge (MOR) and transform fault lineaments identified using free-air, vertical gradient, and filtered directional gradient maps from the Sandwell and Smith gravity data. Furthermore, the reinterpretation of seismic reflection data offshore West Greenland, along with a newly compiled crustal thickness model, identifies an isolated terrane of relatively thick (19–24 km) continental crust that was separated from Greenland during a newly recognised phase of E-W extension along West Greenland's margin. We interpret this continental block as an incompletely rifted microcontinent, which we term the Davis Strait proto-microcontinent. Our reconstruction suggests release of the proto-microcontinent coincided with a change in the spreading orientation from ∼ 58 to 49 Myr during the alignment of Canada and Greenland's rifted margins, indicating a fundamental control of lithospheric structure on plate motions. Proto-microcontinent separation was induced by transpression along a newly recognised NE-SW trending transform margin that joined the Labrador Sea and Baffin Bay, prior to development of the Ungava Fracture Zone (UFZ). The location of this transform margin is constrained using our crustal thickness model, which demonstrates a sharp NE-SW trending continent-ocean transition across the northern Saglek basin. We term this newly identified first-order tectonic feature the Pre-Ungava Transform Margin (Pre-UTM), which accommodated early NE-SW motion between Greenland and Canada. Our identified mechanism of microcontinent formation may be widely applicable to other microcontinents around the globe, and further study is merited to understand the role of plate motion changes and transpression in microcontinent calving. [ABSTRACT FROM AUTHOR]

The ∼173–164 Ma Papudo‐Quintero plutonic complex near 32.5°S in central Chile records three deformation events that provide insight into the tectonic development of the early Andean margin. The first event (D1) includes: (a) high‐temperature (>600°C), coaxial‐dominated strain along NE‐ to N‐striking subvertical shear zones; (b) widespread emplacement of granitic dikes that dip gently to steeply NE; and (c) development of narrow (<10 cm thick) strike‐slip and oblique‐reverse shear zones. These D1 structures record NW‐SE to WNW‐ESE transpressional shortening with a component of sinistral shear parallel to the N‐S trending magmatic arc. Zircon and apatite U‐Pb dates and cross‐cutting relations constrain most D1 deformation to ∼166–164 Ma. The second event (D2) occurred during postmagmatic cooling in the Late Jurassic and was characterized by development of pervasive E‐W‐striking veins with alteration halos and minor strike‐slip and normal faults that record N‐S extension in a transtensional regime. Structures associated with the last deformation event (D3) include Late Jurassic to Early Cretaceous mafic dikes, veins, and conjugate strike‐slip faults that record NW‐SE to N‐S shortening in a strike‐slip regime. D1 deformation is consistent with studies from other areas that document NW‐SE shortening ± sinistral transpression along the arc throughout the Jurassic, suggesting this deformation was regional in scale and driven by oblique subduction convergence. Deformation associated with oblique convergence was localized within the active magmatic arc, which was an important process in the early Andean orogeny. As the arc migrated eastward, D2 and D3 structures formed in a low‐stress regime in an arc margin or forearc setting. Key Points: Three deformation events (D1, D2, and D3) are recorded in the ∼173–164 Ma Papudo‐Quintero plutonic complex in central ChileD1 records ductile NW‐SE transpressional shortening in the Middle Jurassic; D2 and D3 record brittle transtension or strike‐slip deformationD1 is consistent with regional oblique subduction convergence and localization of plate‐driven strain in the active magmatic arc [ABSTRACT FROM AUTHOR]

The Clarke River Shear Zone marks the boundary between the Thomson and Mossman orogens in the northeastern Tasmanides. To better understand the kinematic history of this east-northeast-trending shear zone, and its role during the tectonic history of eastern Gondwana, we investigated rock deformation along a segment of the Clarke River Shear Zone. Based on field observations, interpretation of aeromagnetic data and microstructural analysis, we show that the Clarke River Shear Zone experienced at least three phases of reactivation. Gently plunging stretching lineation and kinematic indicators, such as steeply plunging asymmetric folds and asymmetric porphyroclasts, correspond to an early phase of sinistral strike-slip ductile shearing. Subsequent general dextral shear deformation is suggested based on the presence of S-tectonites, symmetric porphyroclasts and kinematic indicators with dominant dextral and subordinate sinistral shear senses. This phase, which occurred under amphibolite-facies metamorphic conditions, was contemporaneous with the emplacement of the Craigie Tonalite, for which we obtained a new zircon U–Pb crystallisation age of 410.3 ± 1 Ma. A later reactivation phase along the Clarke River Shear Zone, under brittle conditions, is indicated by the presence of cataclasite zones and chlorite–epidote alteration. Based on our findings, and regional information on the tectono-magmatic evolution of northeastern Queensland, we suggest that the Clarke River Shear Zone was possibly a sinistral transform fault during the Silurian. During the Devonian, it is possible that deformation along the Clarke River Shear Zone was related to the transition between the non-retreating subduction zone in the north, and the highly mobile (retreating) plate boundary farther south. However, the dextral kinematic component associated with this deformation is not fully explained. Brittle deformation, likely associated with dextral transpression during the Carboniferous, marked the last stage of activity along the Clarke River Shear Zone. The Clarke River Shear Zone records three phases of reactivation during the Silurian–Carboniferous. Ductile dextral general shear deformation along the Clarke River Shear Zone occurred at ca 410 Ma, based on zircon U–Pb dating of a syn-tectonic intrusion. The Clarke River Shear Zone likely accommodated subduction segmentation during the Silurian–Devonian. [ABSTRACT FROM AUTHOR]

Underpinning almost every Paleozoic paleogeographic reconstruction and tectonic model of the Lachlan Orogen is the interpretation of the structural geology related to crustal collision and amalgamation. Bounding the eastern margin of the Lachlan Orogen is a north-trending corridor of Cambrian–Ordovician turbidites that in northeast Victoria are recognised as the Pinnak Sandstone or previously known as the Mallacoota Beds. This sequence contains an accretionary prism related early S* foliation, syn-sedimentary dykes, slump structures, early faults or décollements and early quartz veins. These indicate anisotropic compaction by fluid extraction in a shallow marine turbidite sequence that underwent localised deformation (D1), which can be attributed to the Benambran Orogeny (ca 450 Ma). There was a change in the rheological properties during the ensuing late Silurian D2 Bindian Orogeny (ca 420 Ma). This event produced north–south-trending upright, east-verging folds (F2) with a marked partitioning of strain between the different sedimentary units. Folds plunge south at ∼30°, are tight to isoclinal, with local collapsed hinges and limb thrusts. This D2 deformation along the paleo-Pacific margin involved dextral transpression and a southerly propagation of the deformation front. Superimposed on these structures is an east–west paleostress pattern and two episodes of faulting (D3 and D4). In the first, brittle strike-slip faults were accompanied by ductile folding related to east–west shortening during the Middle–Late Devonian Tabberabberan Orogeny (ca 385–370 Ma). These were accompanied by the emplacement of the Sandpatch Point Granite. The second episode (D4) of strike-slip faulting reactivated many of the earlier faults during further east–west shortening and was related to the Carboniferous Kanimblan Orogeny (ca 354–343 Ma). This is best seen close to the granite contact where the strong crystallised granite reinforced the contact metamorphosed greywacke sequence, inhibiting ductile deformation so that faults deformed in a brittle fashion. Eastern Australia was at a convergent plate boundary where a Middle–Late Ordovician turbiditic sequence was accreted to an accretionary prism. The Pinnak Sandstone contains a weak phyllosilicate alignment (S*), D1 faults and folds from localised deformation in the accretionary prism. The Silurian Bindian Orogeny produced upright east-verging, south-plunging F2 folds. Brittle faults overprint the Bindian tectonic features and are accompanied by minor folding, marking the transition into Middle Devonian and Carboniferous deformation and intrusive events. The kinematics and geometries associated with these deformation events reflect the changing tectonic regime along the paleo-Pacific margin of eastern Australia during east–west compression. [ABSTRACT FROM AUTHOR]

Restraining bends influence topography, strike‐slip evolution, and earthquake rupture dynamics, however the specific factors governing their geometry and development in the crust are not well established. These relationships are challenging to investigate in field examples due to cannibalization and erosion of earlier structures with cumulative strain. To address this knowledge gap, we investigated the structure, morphology, and kinematics of 22 basement‐cored restraining bends on low net‐slip faults (<10 km) within the southern Eastern California shear zone (SECSZ) via mapping, topographic analyses, and 3D numerical modeling. The bends are self‐similar in form with most exhibiting focused relief between high‐angle bounding faults with an arrowhead shape in map view and a "whaleback" longitudinal profile. Slight changes in that form occur with increasing size indicating predictable growth that appears to be primarily controlled by local fault geometries (i.e., bifurcation angle), rather than the influence of fault obliquity relative to far‐field plate motion, due to inefficient slip‐transfer across interconnected irregularly trending closely spaced faults. Modeling results indicate that the self‐similar fault‐bound geometry of SECSZ restraining bends may arise from elevated shear strain at the outer corners of single transpressional fault bends with increasing cumulative slip. This, in turn, promotes growth of a new fault leading to efficient accommodation of local convergent strain via uplift between bounding faults. Finally, our results indicate that the kilometer‐scale restraining bends contribute minimally to regional contraction as they only penetrate the upper third of the seismogenic crust and are therefore also unlikely to impede large earthquake surface ruptures. Key Points: Southern Eastern California shear zone restraining bends exhibit self‐similar forms that change predictably with growthUplift patterns within these bends are influenced more by local fault geometries than by obliquity of fault trend to plate motionPositive flower structures may initially develop due to increased shear strain at bend corners [ABSTRACT FROM AUTHOR]

Plate motion obliquity along the dominantly transform Queen Charlotte plate boundary (QCPB) peaks offshore Haida Gwaii. To investigate the effects of obliquity on plate boundary deformation, we analyze continuous seismic waveforms from temporary and permanent stations from 1998 to 2020 to generate a catalog of ∼50,000 earthquakes across Haida Gwaii. We use an automated technique based on auto‐regressive phase detection and onset estimation to obtain the initial seismic catalog, integrate existing catalogs, invert for 3D velocity structure using data from the best constrained period, and relocate the entire catalog using the new 3D velocity model. We investigate the seismically active sections of the transcurrent Queen Charlotte fault (QCF), noting that little seismicity locates directly along its bathymetrically defined trace. Instead, seismicity illuminates a complex system of segmented structures with variable geometries along strike. Other clusters highlight active shallow faults within the highly deformed Queen Charlotte terrace. Few aftershocks appear on the thrust plane of the 2012 Mw 7.8 Haida Gwaii earthquake except near its inferred intersection with the QCF at 15–20 km depths, suggesting elevated residual stress at the juncture of slip‐partitioning. Deep crustal seismicity (up to ∼20 km depths) beneath central Haida Gwaii aligned parallel to the strike of the thrust plane may represent landward underthrusting of the Pacific plate. Our results suggest possible coseismic strike‐slip rupture on the QCF during the 2012 earthquake and add support to the thesis that highly oblique transform boundaries are viable settings for subduction initiation. Plain Language Summary: We investigated the complex tectonics offshore Haida Gwaii, western Canada, where the Pacific and North American plates slide past one another obliquely. By compiling and analyzing the most comprehensive earthquake catalog in the area, spanning 1998–2020, we present the most detailed report to date of the earthquake‐producing structures in the region, including previously unidentified and highly segmented faults. Clusters of seismicity illuminate (a) a highly deformed terrace of elevated seafloor west of Haida Gwaii, (b) a complex and segmented fault system adjacent to the previously‐mapped surface trace of the main Queen Charlotte strike‐slip fault, and (c) the inferred fault intersection at depth between the subvertical Queen Charlotte fault (which hosted the 1949 magnitude 8.1 earthquake) and the shallowly dipping Haida Gwaii thrust (which hosted the 2012 magnitude 7.8 earthquake). We also speculate that the 2012 earthquake may also have involved some motion on the Queen Charlotte fault. These results contribute to better constraints on regional tectonics and hazards, and provide insights into the mechanisms of subduction initiation. Key Points: Seismicity off Moresby Island is distributed along multiple segments slightly off of the Queen Charlotte fault traceAftershocks at intersection of Queen Charlotte Fault with the 2012 Mw 7.8 thrust plane reflect residual stress at slip partitioning juncturePreviously undocumented deep seismicity beneath Haida Gwaii is consistent with an underthrusting Pacific Plate [ABSTRACT FROM AUTHOR]

The relation of plate kinematics to the structural record of arc plutons and their host rocks is complex and still not fully understood. We address this issue through a combination of field mapping, structural analysis, anisotropy of magnetic susceptibility analysis, and fabric modeling in the Late Cretaceous Tuolumne Intrusive Complex, Sierra Nevada, California. A pattern of anti‐clockwise rotation from ∼NNW–SSE to WNW–ESE steep foliations and change in fabric ellipsoid shape from oblate to prolate was revealed in successively emplaced Kuna Crest (∼95–92 Ma), Half Dome (∼92–89 Ma), and Cathedral Peak (∼89–84 Ma) granodiorites. The numerical model indicates that the Kuna Crest was emplaced in a transpressional setting with an angle of convergence α = 60–40°, whereas the Half Dome and Cathedral Peak required simultaneous vertical constriction overprinted by transpression with α = 35–15°. This transition, which occurred at ∼92 Ma, is accompanied by a shallowing of the lineation plunge observed also in other ∼88–84 Ma central Sierra Nevada plutons. Provided that the Cretaceous Sierra Nevada arc was constructed during overall dextral transpression, these transitions reflect significant changes in kinematics, where ∼107–92 Ma plutons were emplaced during pure shear‐dominated transpression, which was followed by a transition to wrench‐dominated transpression recorded in ∼92–84 Ma plutons. Such a transition in kinematics is explained as a result of progressively increasing obliquity of the relative convergence of the Farallon plate subducting beneath the North American continental margin, in agreement with most paleogeographic reconstructions. Key Points: Field mapping, structural analysis, magnetic anisotropy, and fabric modeling were carried out in the Tuolumne Intrusive ComplexChanges in foliation strike, fabric symmetry, and lineation plunge imply a change in the angle of convergenceThe transition from pure shear to wrench‐dominated transpression reflects increasing convergence obliquity of the Farallon plate [ABSTRACT FROM AUTHOR]

Mississippi Valley-type (MVT) Zn–Pb deposits generally form in both orogenic forelands and thrust belts, but the tectonic and structural controls on ore formation in the latter tectonic setting remain poorly understood. This study examines MVT deposits in the late Mesozoic–Cenozoic Tethyan and Cordilleran orogenic thrust belts that have ages determined mainly by paleomagnetic methods or that are well constrained by other geological relationships. Some deposits predated regional thrusting but most deposits formed during regional transpression or extension after early stages of thrusting during convergence. Extensional faults rather than compressional (reverse or thrust) faults control the distribution of ore zones at the deposit or district scale. Post-thrusting MVT mineralization within thrust belts occurs as a result of synorogenic stress transition from compression to transpression/extension. This stress change appears to favor the generation of local extensional faults due to reactivation of pre-existing structures, simple shearing-related tension or dilation, or other mechanisms such as gravitational spreading of weak crust, lower crustal flow, and removal of lithosphere. In comparison, ore-controlling extensional faults in forelands are generated by means of the flexure of the foreland plate during orogenic convergence. Exploration for MVT ores in orogenic thrust belts should focus on extensional zones and extensional faults at district and deposit scales. [ABSTRACT FROM AUTHOR]

Transpressional margins are widespread, and their dynamics are relevant for plate boundary evolution globally. Though transpressional orogen evolution involves a topographic response to deformation, many studies focus only on the structural development of the system ignoring surface processes. Here, we present a new set of analog models constructed to investigate how tectonic and surface processes interact at transpressive plate boundaries and shape topography. Experiments are conducted by deforming a previously benchmarked crustal analog material in a meter‐scale plexiglass box while controlling erosion through misting nozzles mounted along the transpressional wedge. To analyze the experiments, we generate digital elevation models from laser scans and conduct image correlation analysis on photos taken during experiments. We focus on three experiments that cover a range of erosional conditions and shortening stages (two end‐member erosion models and a dry reference). In all experiments, a bivergent wedge forms, and strain partitioning broadly evolves according to previously established models. Regarding drainage networks, we find that the streams in our models develop differently through feedback between fault development and drainage rearrangement processes. Differences between end‐member erosional models can be explained by the varying response of streams to structure modulated by rainfall. Additionally, erosion may influence the structural evolution of transpressional topography, leading to accelerated strike‐slip partitioning. From these results, we create a model for developing structures, streams, and topography where incision and valley formation along main structures localize exhumation. We apply insights from the models to natural transpressional systems, including the Transverse Ranges, CA, and the Venezuelan Andes. Key Points: Feedback between fault and drainage network development regulates the deformation, exhumation, and morphology of transpressional systemsIncreased erosion accelerates the progression from distributed deformation to complete strike‐slip strain partitioningDue to heightened rock uplift and incision, the maximum exhumation in a transpressional wedge is along the master fault and axial valley [ABSTRACT FROM AUTHOR]

Contractional deformation structures at the front of transpressional orogens display complex three‐dimensional geometries deviating from the interpretative templates commonly applied in thrust belts. Accordingly, detailed constraints on deformation patterns and associated paleofluid circulation are desirable, especially for fracture geometry and permeability predictive purposes. The Pag anticline, which is located in the Dinaric fold and thrust belt, provides an appropriate field site for studying fold‐ and fault‐related deformation structures in a transpressive setting. We performed a multiscale structural analysis together with petrographic and stable isotope characterization of the deformation‐related calcite cements. Structural mapping suggests that the Pag anticline is a detachment fold developed mainly by buckling, since large‐scale thrust faults are absent. Fold tightening in a transpressive setting produced a complex deformational structure including two sets of N‐S right‐lateral and E‐W left‐lateral late‐stage strike‐slip fault sets trending oblique to the NW‐SE fold axis. The pre‐folding deformation pattern includes incipient normal faults likely related to the forebulge stage, veins and stylolites coherent with NE‐SW layer parallel shortening contraction in a strike‐slip regime, and metric to decametric scale conjugate thrusts coherent with layer parallel shortening in a compressive regime. Buckle folding preceded propagation of a series of accommodation structures during fold tightening. Petrographic and isotopic data indicate meteoric alteration of the Cretaceous platform carbonates in the prefolding stage, likely due to forebulge subaerial exposure. Layer parallel shortening and early syn‐folding veins involved formational fluids resulting from mixed marine and meteoric fluids during folding at shallow burial conditions. Eventually, meteoric fluid infiltrated again along strike‐slip faults, acting as cross‐formational conduits in the postfolding stage. Key Points: Buckle fold with high geometrical complexity induced by overstepping forethrusts and backthrustsTransition from compressional to transpressional stress regime during buckle foldingPaleofluid circulation switches from closed to open during fold tightening and strike‐slip faulting [ABSTRACT FROM AUTHOR]

Active strike‐slip fault systems commonly display along‐strike Quaternary slip rate gradients associated with fault bends and splay faults, which generate surface uplift by dip‐slip faulting or distributed "off fault" deformation. By analogy, the documentation of long‐term (107 yr) slip gradients on some continental strike‐slip fault systems implies long‐term coevolution of strike‐slip and dip‐slip fault systems. Here we leverage the observed ≥33 Myr right‐lateral slip gradient on the Denali fault, Alaska, USA to investigate the role of splay thrust systems in accommodating the slip gradient. We focus on the Broxson Gulch thrust system, which splays southwestward from the Denali fault in the eastern Alaska Range. Apatite and zircon (U‐Th)/He and fission‐track cooling ages from metasedimentary and metaplutonic rocks intersected by the thrust system record an along‐strike decrease in cooling ages commensurate with an increase in late Oligocene‐Neogene bedrock exhumation and shortening with proximity to the Denali fault. The dominant structure in the Broxson Gulch thrust system is the Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone–the main Late Cretaceous suture between western North America and outboard accreted arc terranes. After reactivation of the Valdez Creek shear zone at ca. 30 Ma, the thrust system grew by south‐vergent imbrication of the upper crust along thrust and reverse faults until at least 6 Ma. Incorporating results from the Broxson Gulch thrust system into the regional structural evolution of the Denali fault system reveals significant spatiotemporal heterogeneity in shortening adjacent to the Denali fault. Moreover, nearly all of the late Oligocene‐Neogene shortening south of the Denali fault was focused along reactivated terrane boundaries inherited from Mesozoic assembly of the North American Cordillera, and the spatial distribution of the inherited structures appears to control slip partitioning behavior of the Denali fault system across time scales ranging from 101 (historic seismicity) to 107 yr. The slip partitioning behavior of the Denali fault system highlights the mechanical importance of inherited structures leading to protracted shortening on splay thrust systems, which siphon slip from the master strike‐slip fault. We contend that the weakness of nearby reactivated terrane boundaries should be considered among other mechanisms commonly evoked to explain the partitioning behavior of continental strike‐slip fault systems (e.g., stress field rotation, obliquity angle, and strength of master strike‐slip fault). Plain Language Summary: Lateral motion across vertical faults, such as the San Andreas strike‐slip fault in California or the Denali fault in Alaska, becomes complicated when that fault bends. The complex motion in fault bends is often taken up by several faults that each play a different role: some faults move the crust horizontally and some faults uplift the crust and create mountains. For decades, geologists have been interested in fault bends in vertical faults because the earthquakes and resulting mountains associated with bent faults are different from those that form along straight faults. To help understand fault bends, we studied the Denali fault in southern Alaska because it has been curved for at least 45 million years and has had several large earthquakes that built the large mountains of the Alaska Range during that time. In our study area, we found that the mountains started forming at about 30 million years ago because an older fault related to formation of the North American continent formed a weakness that reactivated. When we compared our findings with previously published data from other faults through the curved part of the Denali fault, we found that most of the faults that uplifted the crust and made mountains in the last 30 million years are also old faults related to assembly of North America. The results from our study suggest that the location of the older faults strongly influences which faults accommodate vertical motion, seen as uplift of the mountain ranges, and which faults accommodate lateral motion in fault bends. Key Points: Oligocene‐Neogene increase in convergence across the dextral Denali fault system reactivated a suture, which developed a splay thrust systemProtracted shortening on splay thrust systems stabilized the ca. 107 yr slip gradient observed on the Denali faultThe spatial distribution of reactivated terrane boundary faults near the master Denali fault controls the slip partitioning behavior [ABSTRACT FROM AUTHOR]

[Display omitted] • Atypical subduction is favored by a strike-slip-dominated transpression stress regime. • Subduction polarity reversal may play an critical role in forming atypical subduction. • The Gagua Ridge may not be of atypical subduction. Subduction zones act as interfaces for exchanging materials between the Earth's crust and mantle. The western Pacific plate region is evolving within a convergent tectonic environment. Old oceanic plates generally subduct beneath young oceanic plates, as exemplified by the Izu-Bonin-Mariana and Tonga-Kermadec subduction zones. However, in some subduction zones, such as the Mussau Trench, the Hjort Trench, and the Gagua Ridge, young and more buoyant oceanic plates have been recognized to subduct underneath older and denser plates. What conditions promote atypical subduction, however, remain elusive. In this study we take the Mussau Trench, the Hjort Trench, and the Gagua Ridge as examples to explore the possible underlying factors that control the formation of atypical subduction. By anatomizing the tectonic features of both the Mussau Trench and the Hjort Trench, we find that atypical subduction may be feasible mainly when the plate boundary is characterized by strike-slip-dominated transpression; that is, the strike-slip component overwhelms the compression component, which may argue against the atypical subduction occurring at the Gagua Ridge, at least at present. Moreover, in light of the evolution of both the Mussau Trench and the Hjort Trench, it is further suggested that subduction polarity reversal and a strike-slip border are the keys to atypical subduction. [ABSTRACT FROM AUTHOR]

Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries. The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and has been deformed under the ENE–WSW maximum horizontal compression since the late Pliocene. In this study, we analyzed short-term instrumental seismic (focal mechanism) and long-term paleoseismic (Quaternary fault outcrop) data to decipher the neotectonic crustal deformation pattern in the southeastern Korean Peninsula. Available (paleo-)seismic data acquired from an NNE–SSW trending deformation zone between the Yangsan and Ulleung fault zones indicate spatial partitioning of crustal deformation by NNW–SSE to NNE–SSW striking reverse faults and NNE–SSW striking strike-slip faults, supporting a strike-slip partitioned transpression model. The instantaneous and finite neotectonic strains, estimated from the focal mechanism and Quaternary outcrop data, respectively, show discrepancies in their axes, which can be attributed to the switching between extensional and intermediate axes of finite strain during the accumulation of wrench-dominated transpression. Notably, some major faults, including the Yangsan and Ulsan fault zones, are relatively misoriented to slip under the current stress condition but, paradoxically, have more (paleo-)seismic records indicating their role in accommodating the neotectonic transpressional strain. We propose that fluids, heat flow, and lithospheric structure are potential factors affecting the reactivation of the relatively misoriented major faults. Our findings provide insights into the accommodation pattern of strain associated with the neotectonic crustal extrusion in an intraplate region of the eastern Eurasian Plate in response to the collision of the Indian Plate and the subduction of the Pacific/Philippine Sea Plates.

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The central portion of the Kalinjala Shear Zone, in the Port Neill region, South Australia, is recognised as a northeast-trending anomalously magnetic corridor coinciding with a sub-vertical transpressional dextral shear zone. This shear zone is a primary lithospheric structure, separating the nucleus of the Archean Gawler Craton from a suite of Paleoproterozoic granites (ca 1850 Ma) and earlier paragneiss. At Port Neill, there is an apparent 17 km dextral offset of a pre-existing Bouguer gravity anomaly by the Kalinjala Shear Zone. This is attributed to Kimban-aged (ca 1740–1690 Ma) deformation that is accompanied by peak granulite facies metamorphic conditions reaching pressures of ∼1.0 GPa and temperatures of ∼800 °C. This is consistent with the presence of leucosomes, within the sheared fabric, in the axial surface of mylonitic folds and in mafic gneisses. Strain has been localised within and adjacent to mafic dykes, predominantly hosted in the granitic rocks, with the highest strained areas having the greatest evidence of leucosome extraction. The local orientation of stretching lineations in this shear zone do not necessarily correlate with the transport direction but may reflect along- and across-strike variations in finite shear strain into alternating zones dominated by either constrictional or a superimposed flattening strain. Overprinting the dominant dextral movement are sinistral shears, with horizontal strike-slip movements, which post-date the peak metamorphic assemblages and are generally confined to sites containing late K-feldspar-rich pegmatites. The major movement recorded in the Kalinjala Shear Zone was both horizontal and vertical, occurring in response to regional exhumation of the Cornian-aged (ca 1850 Ma) sequences in the east, during the Kimban Orogeny, and was basically controlled by the nature of lithospheric plate convergence during accretion of a continental backarc onto the Gawler Craton. Dextral transpression with late-sinistral along-strike extension and east-up exhumation is associated with 17 km of horizontal offset along the central section of the Kalinjala Shear Zone. Deformation is dominated by three major Kimban-aged (ca 1730–1690 Ma) events, which overprint older ensialic backarc metasedimentary rocks, orthogneiss and granites of the Donington Suite. Granulite facies metamorphic conditions control the nature of deformation and strain distribution within the shear zone. The Kimban events record the collision of the Gawler Craton nucleus with the southern margin of the North Australian Craton. [ABSTRACT FROM AUTHOR]

The present study offers a novel opportunity to characterize the structural style and tectonic evolution of the Mesozoic Shabrawet inverted structure zone and its interaction with the northward propagation of the Gulf of Suez rift, Egypt. Based on the integration of fieldwork, detailed surface mapping and subsurface imaging by borehole data and seismic interpretation, the geology of Shabrawet area is characterized into the northern, central, and southern structural subareas. The central subarea has exposures of Cretaceous rocks whereas the northern subarea has the Jurassic/Cretaceous subcrop capped by the Oligo/Miocene rocks with remarkable stratigraphic hiatus probably due to differential erosion or non-deposition of the Lower Tertiary-Cretaceous sediments. The southern subarea represents a SW-dipped gulf-parallel block of Middle/Late Eocene and Oligo/Miocene sediments. The structural elements of the Shabrawet area are represented by a group of plunging and double plunging folds of NE-ENE-, E-W, WNW- trends that are dissected by NE-reverse faults, ENE-trending transpressional faults, N-S sinistral faults, E-W to WNW – trending dextral faults and NW-trending normal faults. Structural analysis, fault slip data, and the constructed subsurface seismic profiles and thickness maps reveal the tectonic history of the area through a Late Cretaceous-Eocene transpressional inversion of E to ENE-extensional Jurassic border faults. This ENE-inverted Syrian arc structure zone played as structural high with non-deposition of Eocene sediments and differential erosion of Cretaceous sediments. During the Oligo-Miocene NE-extension, this high-oblique inverted zone terminates the northward propagation of gulf parallel faults and SW- block rotation of the northern structural province of the Gulf of Suez rift at the southern subarea and the central Bitter Lake. Further westward, this ENE-inverted Shabrawet-Abu Sultan intrabasinal Jurrassic half-graben of N- dipping might be structucturally correlatable with the NE- inverted structural belt of Gebel Maghara in Northern Sinai. [ABSTRACT FROM AUTHOR]

The paleostress analysis of the southeast part of the Ukrainian Outer Carpathians (UOC) was carried out with the separation and stress inversion TR method (TRM). The analysis includes site and bulk stress tensors through which the late-orogenic processes of the frontal part of UOC can be better described. In particular, three bulk compressive stress regimes dated to Miocene describe a compressional deformation that changes progressively from real to hybrid. The first stress regime is a pure compression and changes progressively to transpression, while the trend of the greatest principal stress axis ( σ 1 ) constantly remains ENE-WSW (065°), perpendicular to the main trend of the UOC. This progressive deformation spans the Late Burdigalian to Sarmatian period and reflects the driving stresses during the Alcapa and Tisza-Dacia mega-units drifting and docking with the Eastern European Platform. During the transpressional stress regime, the thrust displacements waned, and transfer (strike-slip) faults accommodated the deformation. The third stress regime is also a hybrid compression, i.e. transpression, but the greatest principal stress axis ( σ 1 ) trends NNE-SSW (029°). It reflects the post-docking deformation giving rise to mesoscale NW-WNW thrusts and transfer (strike-slip) faults. However, these thrusts and strike-slip faults have not modified the NNW-SSE rectilinear trend of the UOC. This hybrid compression outlasted the Late Miocene (Latest Sarmatian–Early Maeotian), and it is related to the separation and left-lateral movement of the Tisza-Dacia plate from the Alcapa plate. In addition, two extensional stress regimes with the least principal stresses ( σ 3 ) trending NE-SW and NW-SE have been defined. We interpret them to represent subsidiary stresses in the Carpathians' uppermost part due to orogen collapse both normal and parallel to the orogen after the Late Miocene. [ABSTRACT FROM AUTHOR]

The Ciclón-Exploradora Project is located in the Exploradora Porphyry Copper District, which corresponds to an old artisanal mining and exploration area 65 km northeast from El Salvador Copper Mine, between 3200 and 4000 m.a.s.l. and inserted within the Eocene-Oligocene metallogenic porphyry belt and Domeyko Cordillera. Exploitation has been discontinuous since the late mid-19th century. It first started with production at the Copper Exploradora Mine, and later for Au–Ag at the Ciclón and San Carlos mines. Nevertheless, after decades of work and exploration the district has great potential for new discoveries. Epithermal polymetallic (Cu–Ag–Zn–Pb–Au) mineralization took place related to the evolution of the Exploradora Plutonic and Porphyry Complex. This Eocene Complex is a composite of dioritic to monzodioritic magmatic intrusions including several intermediate composition Cu–Au and Cu–Mo porphyry centers, mostly emplaced in NNE to NE-oriented corridors. The hosted rocks consists of folded Triassic and Jurassic calcareous sedimentary units partially altered by a kilometric metasomatic envelope that contains skarn mineralization. The complex was mainly emplaced syntectonically along the Sierra Castillo Fault System, which is part of the margin-parallel Domeyko Fault System. These faults together with NE and NW striking transversal faults were active during the Eocene, playing a key role in the emplacement of magmatism and mineralization at the district. The main magmatic phases of the Exploradora Complex record different levels of alteration exposure, mineralization and geochronological ages suggest at least three discrete and continuous episodes of magmatism during ∼4 m.y. (1) An early composite of dioritic to monzodioritic intrusions (38-36 Ma), generally associated with coarse Ca (K) alteration and spatially close to Zn or Fe exoskarn mineralization. (2) An early to inter mineral hypabyssal rocks (36-35 Ma) composed of dacitic to rhyolitic porphyries and aplitic rocks, mostly affected by k-feldspar, propylitic, quartz and argillic alteration, locally with secondary biotite and Cu anomalies. Include quartz monzodiorite porphyries exposing Cu–Au mineralization associated with potassic alteration (biotite-magnetite plus albite) and related quartz-veinlets. (3) CODELCO's Exploradora Cu–Mo mineralization (35-34 Ma) associated with late dacitic and dioritic porphyries, HS-Au mineralization veinlets and a post-mineral diatreme. Polymetallic mineralization occurs at the western part of the district, hosted mainly in sedimentary and intrusive rocks and partially at major intrusion contacts. The Ciclón-Exploradora polymetallic deposit is a 5 km-long NS- and NNW-striking vein-breccia-fault, with mainly sinistral movements, it includes carbonate replacement deposits and dissolution breccia bodies nearby. The tectonic stress field orientation related to the vein-breccia-fault mineralization records subhorizontal NW-trending σ 1 , SW-trending σ 3 , and subvertical σ 2. Polymetallic hypogene mineralization shows a consistent evolution from low sulfidation conditions to intermediate sulfidation assemblages, spatially related to an early skarn stage characterized by the presence of magnetite, pyrrhotite, Fe-rich sphalerite, developed in calcareous sedimentary rocks. Skarn zonation includes garnet-pyroxene-wollastonite-scapolite minerals. Epithermal polymetallic mineralization shows four main stages. The first and second stages consist of pervasive chlorite followed by chlorite-pyrite veinlets that may or may not contain quartz, and massive pyrite mineralization bodies generally forming euhedral crystals. The second phase ends with a Cu-dominant stage given by chalcopyrite-quartz (±chlorite - sericite – pyrite) and lower contents of Ag-bearing sulfosalts. The third stage is recognized as a polymetallic event characterized by multiple veinlets emplaced both in intrusive and sedimentary rocks where it also forms replacement ore bodies along lithological contacts. It consists of Cd-rich sphalerite, galena, Fe–Mn–Zn carbonates, and minor amounts of chalcopyrite, tennantite-tetrahedrite, and other Ag sulfosalt minerals. Gold is present as native and spectrum minerals with quartz. Main alteration minerals are quartz-kaolinite and minor amounts of sericite. The last stage consists of calcite ± arsenopyrite veinlets crosscutting the previous mineralization. This paragenetic evolution is similar to the one observed in several epithermal porphyry-related polymetallic "Cordilleran" deposits (e.g., Cerro de Pasco, Perú). Crosscutting relationship and exposure of epithermal mineralization, porphyry alteration and magmatism suggests that, in a short period (38–34 Ma), the whole district was exhumed probably several kilometers (3–6 km), related to a compressional to transpressional deformation regime. • The Epithermal Ciclón-Exploradora Project is located in the Exploradora Porphyry Copper District, inserted within the Eocene-Oligocene metallogenic porphyry belt and Domeyko Cordillera, Chile. • Epithermal polymetallic (Cu–Ag–Zn–Pb–Au) mineralization took place related to the magmatic and hydrothermal evolution of the Exploradora Plutonic Complex at 38 to 34 Ma. • The Ciclón-Exploradora polymetallic deposit is a 5 km-long NS- and NNW-striking vein-breccia-fault, with mainly sinistral movements. The tectonic stress field orientation related to the vein-breccia-fault mineralization records subhorizontal NW-trending σ 1 , SW-trending σ 3 , and subvertical σ 2. • Epithermal polymetallic mineralization shows four main stages: The first and second stages consist of pervasive chlorite followed by chlorite-pyrite and quartz veinlets, and massive pyrite mineralization bodies. The second phase ends with a Cu-dominant stage given by chalcopyrite-quartz (±chlorite-sericite–pyrite) and lower contents of Ag-bearing sulfosalts. The third stage is recognized as a polymetallic event characterized by multiple veinlets and replacement ore bodies along lithological contacts. It consists of Cd-rich sphalerite, galena, Fe–Mn–Zn carbonates, tennantite-tetrahedrite, and other Ag sulfosalt minerals. Main alteration minerals are quartz-kaolinite and minor amounts of sericite. The last stage consists of calcite ± arsenopyrite veinlets. • This paragenetic evolution from low sulfidation conditions to intermediate sulfidation assemblages is similar to the one observed in several epithermal porphyry-related polymetallic "Cordilleran" deposits (e.g., Cerro de Pasco, Perú). [ABSTRACT FROM AUTHOR]

Measuring penetrative strain is critical for understanding the 3D strain field of structural systems. Here, we investigate ductile strain and kinematics in two Cordilleran structural systems in north-central Idaho: the Salmon River suture zone (SRSZ), which is a west-vergent ductile fold-thrust system that accommodated shortening associated with terrane collision between ∼144 and 105 Ma, and the north-striking, subvertical western Idaho shear zone (WISZ), which accommodated dextral-transpressional shearing between ∼105 and 86 Ma. We collected finite strain data from stretched clasts in three SRSZ thrust sheets, which define 56–87% average thrust-parallel stretching and 35–48% average thrust-normal thinning. Thrust-parallel stretching contributed >27 km of cumulative displacement to the up-dip portion of the fold-thrust system, comparable to the 34 km of total thrust displacement estimated at down-dip levels. In the WISZ, we documented dextral kinematics in lineation-normal planes, and we measured boudinaged and folded granitic dikes to estimate late-stage (∼91-86 Ma) strain, which yielded 65% minimum lineation-parallel stretching and 50% minimum east-west shortening. Subvertical stretching in the WISZ accommodated >9–10 km of exhumation relative to the Idaho batholith to the east. The SRSZ and WISZ both demonstrate the 1st-order importance of ductile stretching for accommodating the large-scale transfer of mass and exhumation in fold-thrust and transpressional systems. • Penetrative strain is a critical component of the 3D strain field in thrust systems. • Thrust-parallel stretching can greatly increase displacement in thrust systems. • Thrust-parallel stretching and thrust-normal thinning enhance exhumation. • Lineation-parallel stretching drives exhumation in transpressional shear zones. [ABSTRACT FROM AUTHOR]

The Western High Atlas is one of the most important sectors of the Variscan foldbelt in Morocco and also of its Alpine intracontinental orogen. Its tectonic evolution is thus essential for the understanding, not only of the Moroccan geology, but also of the interaction between successive orogenic cycles which is one of the focus of this article. Furthermore, as the Moroccan Variscides must be seen in the context of the complex dextral collision between Laurasia and Gondwana, this is also a contribution to the comprehension of the complexity of transpressive regimes and strain partitioning processes. New data show that WNW-ESE sinistral Variscan shear zones (mainly the Addouz-Adassil-Anamrou one - AAAsz), although secondary to the main orogenic scale ENE-WSW dextral shear zones, must be considered in order to understand the Late Paleozoic deformation and its Alpine reactivation. In fact, the concentration of the last stages of the Variscan ductile deformation in the steep and irregular AAAsz played an important role in the initiation and localisation of the minor magmatic events and influenced the geometry and kinematics of the Late Variscan WNW-ESE sinistral shear zones. Furthermore, during the Alpine inversion, the orientation of the AAAsz and related major anisotropies tend to be reactivated, with a major reverse component, giving rise to the irregular Adassil-Medinet fault zone, one of the most important structures of the Western High Atlas. • The steep Variscan shear zones control the Atlasic inversion in Western High Atlas • An heterogeneous strike-slip component in pervasive in the Moroccan Variscides • The Variscan shear zones induced strong strain partitioning processes • The overstepping segments of the Variscan shear zones controls the coeval magmatism [ABSTRACT FROM AUTHOR]

The Caçapava do Sul Granitic Complex is a ca. 30 km-long syntectonic batholith emplaced at 580-560 Ma along the N–S to NNE-SSW striking Caçapava do Sul Shear Zone, configuring the core of a double-plunging regional asymmetric antiformal fold, with the Passo Feio Metamorphic Complex metavolcanosedimentary wallrocks occurring at the fold limbs. Structural mapping and kinematic analysis along its whole margins allowed to subdivide the granite complex into seven structural domains, each with its own geometric characteristics and kinematics. The observed microstructures included abundant K-feldspar and plagioclase porphyroclasts with asymmetric recrystallization tails, S–C and S–C–C' fabrics, and more rarely synmagmatic fractures and asymmetrically developed myrmekites. In general, high temperature microstructures are abundant in the southern half of the granitic complex, while these features are overprinted by low temperature brittle-ductile to brittle microstructures in its northern half. The Southern Domain presents foliations with medium angle dip towards the south, high rake lineation towards the SSW and normal shear sense indicators. The Northwestern and Southwestern domains present mainly subvertical N–S striking foliations with sub-horizontal lineations mostly plunging towards SSW and abundant sinistral shear sense indicators. On the other hand, Southeastern and Santos Ferreira domains presents predominantly NE-SW striking foliations with variably dip and sub-horizontal lineations with abundant dextral shear sense indicators. The Northeastern Domain presents low angle foliation dipping towards the NE, which is also locally described in the Southeastern Domain. Dominantly normal movement with top to NE is described in the Northeastern Domain, also locally reported in the Southeastern Domain. The Northern Domain presents low-angle foliation dipping towards the N, with high rake lineation. No shear sense indicator was observed in the Northern Domain due to brittle deformation overprint, but normal kinematics is inferred. The opposite kinematics of the distinct Caçapava do Sul Shear Zone margins are corroborated by punctual data from the Passo Feio Metamorphic Complex rocks. This is compatibilized by the resultant syntectonic granite flow towards N/NE, which is interpreted in a model of oblique transpression with inclined ductile extrusion. The model suggests that transpression of the middle crust had an important pure shear component which was effectively partitioned into structural domains along the Caçapava do Sul Shear Zone in consequence of post-collisional syntectonic magmatism, and coexisted with extensional tectonics in the upper crust (Camaquã Basin) through a detachment along the brittle-ductile transition. • Caçapava do Sul Granitic Complex presents both dextral and sinistral kinematics. • Strain partitioning was effective due to syntectonic magmatism. • Dextral and sinistral shear sense in opposed zone margins due to ductile extrusion. • Post-collisional syntectonic magmatism led to ductile extrusion during transpression. • Oblique transpression with inclined ductile extrusion along a synmagmatic shear zone. [ABSTRACT FROM AUTHOR]

The article deals with the fundamental concepts of a new method of interpretation of regional gravimetry (scale 1:1000000) based on the idea of the deformational nature of low-frequency gravity anomalies. The method provided an opportunity to identify the direction of tectonic compression in the Yakut diamond-bearing province, to localize segments and axes of inter-shear compression and extension of different kinematics and on that basis to distinguish the shear interaction zones spatially correlating with the location of kimberlite pipes. Particularly, the whole area is characterized by four transpressive compression directions: a pair of orthogonal (dextral with azimuth 8° and sinistral with azimuth 98°) and a pair of diagonal (dextral with azimuth 38° and sinistral with azimuth 128°). These data correlate to those from the regional tectonophysical studies not only within the compression direction azimuths but also within kinematics of transpressive motions for two main phases in geodynamical evolution of the Yakutsk diamond-bearing province (YDP) - predominantly dextral for the first phase of the northeastern compression and sinistral for second phase of the northwestern compression. The article also shows that the Alakit-Olenek mineragenic zone is an extensive (~500 km) area of plastic deformation of rocks ~90 km in width with the right-lateral kinematics of apparent motions of the rocks along its northern and southern boundaries. The southern boundary of the mineragenic zone exhibits the northeaststriking continuity whereas its northern boundary is discontinuous. The boundaries of the Alakit-Olenek mineragenic zone are controlled by the zones of shear interaction of different dynamics and kinematics, which are spatially related to kimberlite pipes and diamond placer deposits. The results of this study imply that the method proposed for interpretation of gravity field can predict the occurrence of structures of geodynamic control of kimberlite magmatism of the Yakut diamond-bearing province.

The opposite-sense fault block rotation across the continental strike-slip faulting plays an important role in accommodating crustal deformation in the north of the East Iran orogen. This research constrains the post-Neogene kinematics of the NW-SE to E-W left-lateral transpressional zones at the northern termination of the N-S striking right-lateral Neh fault system in the East Iran orogen. Using two case studies, we analyzed the NW-SE Birjand splay and the E-W Shekarab transpression zone by analysis of satellite images, structural features, fault geometry and kinematics, GPS (Global Positioning System) velocities, fault- and earthquake-slip stress inversion, and paleomagnetic data. Our results show two distinctive regions of opposite-sense fault block rotations and with different rotation rates. As an asymmetric arc, the Birjand splay displays a transition from the prevailing N-S right lateral shear in the east to NW-SE left lateral transpression in the middle and E-W left lateral shear in the west. In the east, with clockwise fault block rotation, the N-S right lateral faults and the NW-SE oblique left-lateral reverse faults constitute push-ups through the restraining fault bends. In the west, with counterclockwise fault block rotation, the Shekarab transpression zone is associated with the duplex, pop-up, and shear folds. Our suggested kinematic model reveals that the N-S right-lateral shear is consumed on the left-lateral transpressional zones through the vertical axis fault block rotation. This led to an E-W shortening and N-S along-strike lengthening in the East Iran orogen. This research improves our understanding of how opposite fault block rotations accommodate India- and Eurasia-Arabia convergence in the north of the East Iran orogen. The suggested model has implications in the kinematic evolution of intra-plate strike-slip faulting through continental collision tectonics. [ABSTRACT FROM AUTHOR]

Sefidabe and Hyderabad antimony ore deposits are located in the southwest of Sefidabe and in the Sistan Suture Zone. In order to structural analysis of these areas, at first, using satellite images, tectonic lineaments were extracted and the areas with the highest density of length and direction were determined. Then, in the field surveys, veins, faults and mineralization occurred along them were taken. By using stress analysis software, the direction of the principal stresses in the area and the relationships between these structures, tectonic faults and mineralization were analyzed. Compressive shear zones with a northwest-southeast trend are caused by a constraining bend formed between the two of Neh and West-Asagi main faults, is the main factor of mineralization in the study area. This positive flower structure has strongly affected the Paleogene sedimentary and igneous rocks of the region. The Moore's circle indicate a compressional to wrench tectonic regime with the maximum stress direction (03/215) in the northwest-southeast. In this stress regime, in addition to thrust faults, a group of conjugate faults with an acute angle and tensile fractures aligned with the direction of maximum principal stress have formed, which have provided a suitable environment for fluid injection by creating weak zones. [ABSTRACT FROM AUTHOR]

Deformation in the Zagros suture zone is a result of the oblique collision of the Afro-Arabian continent with the Central Iranian microcontinents. Various types of folding and faulting are characteristic features of the study area and indicate the performance of a high strain tectonic regime in this region. To distinguish deformation geometry during the collisional events, strain measurements have been carried out, using the Rf/φ method on deformed radiolarian microfossils, in the Zagros suture zone. Based on the results, the strain ellipsoid shape is in the range of general flattening to plane strain (K=0.16–1.12). Measured mean kinematic vorticity number (Wm) in the deformed radiolarian rocks ranges between 0.50 and 0.87, which implies that exhumation of the Abade-Tashk area was facilitated by a general shear flow (35%

The Tatra Mts form the highest part of the Carpathian mountain chain; however, their tectonic and thermal evolution is still debatable. Previous magnetic fabric studies have primarily focused on the crystalline basement and its autochthonous cover. We investigate the magnetic fabrics of Cretaceous marly limestones from a Mesozoic nappe unit and post-thrusting Oligocene shales and mudstones to unravel the most recent tectonic evolution of the Tatra massif. In addition to standard petromagnetic measurements such as the acquisition of the Isothermal Remanent Magnetization or temperature-dependent susceptibility analyses, we investigated the paleotemperature of the Tatra region because high temperatures are known to significantly affect the magnetic mineralogy. The most common minerals in the studied units are paramagnetic phyllosilicates which govern the in-phase Anisotropy of Magnetic Susceptibility. The ferromagnetic fraction is represented by fine-grained magnetite with a minor contribution of hematite. Measured and counted vitrinite reflectances document an eastward increase in maturity, which is also reflected in the magnetite–hematite grain size ratios. Because the paleotemperatures recorded in the Cretaceous rocks follow the same increasing trend as the post-thrusting shales, it appears that both units were affected by a single major thermal event linked presumably to the Late Oligocene/Early Miocene burial. We propose that magnetic fabrics carried by phyllosilicates document the impact of crucial tectonic phases such as Miocene uplift and Cretaceous thrusting, whereas the out-of-phase Anisotropy of Magnetic Susceptibility and Anisotropy of Anhysteretic Remanent Magnetization fabrics most likely record the stress orientation during major burial episodes. Finally, the conspicuous vertical ferromagnetic lineation present in some Cretaceous sites documents the transpression-controlled tectonic regime in the Oligocene–Early Miocene. • Phyllosilicate fabrics record major tectonic events affecting the Tatra Mts. • Ferromagnetic fabrics formed during burial episodes. • Vertical magnetic lineation is linked with Oligocene–Miocene transpression. • An eastward rise in paleotemperatures in Oligocene and Cretaceous units has occurred. • Higher temperatures affected the Tatras in the Oligocene than in the Cretaceous. [ABSTRACT FROM AUTHOR]

The burial and thermal history of sedimentary basins within oblique-slip mobile zones are unique and multifaceted, with irregular periods of subsidence that are closely related to compressional and shear stress. Modern basin modeling techniques can constrain the timing of tectonic events and thermal history as well as determine rates and magnitudes of basin subsidence, which in turn, helps guide exploration for hydrocarbons. The work presented here is the first modern basin modeling effort in the Ardmore Basin in southern Oklahoma. The study uses 12 one-dimensional burial history models to evaluate the thermal maturity of the Late Devonian (Famennian)–Early Mississippian (Tournaisian) Woodford Shale and the Early–Late Mississippian (Tournaisian–Serpukhovian) Caney Shale hydrocarbon source rocks. All models display a similar tectonic evolution with subsidence during and following Cambrian Iapetan rifting, tectonic stability during a Silurian–Late Mississippian passive margin phase, Pennsylvanian synorogenic subsidence, Permian post-orogenic subsidence, Late Permian–Early Cretaceous regional uplift and unroofing, and Early Cretaceous–Paleogene subsidence of the Gulf of Mexico Basin. Episodic Pennsylvanian subsidence appears to have been synchronous with sequential uplift of the Wichita Uplift and the Arbuckle Uplift in response to major left-lateral transpression. Rapid and high magnitude Late Mississippian–Permian subsidence (>250 m/m.y.; 820 ft/m.y. in basin synclines) suggests the Ardmore Basin functioned episodically as an elevator basin, which is typical of sedimentary basins in oblique-slip mobile zones. The Devonian–Mississippian shale section has a broad range of thermal maturity (vitrinite reflectance, 0.40–2.00% R o), which is strongly dependent on structural position. Isoreflectance lines are subhorizontal and cross-cut structure, indicating post-kinematic thermal maturation in which strata are thermally immature in uplifts and thermally overmature in the deepest synclines. The post-kinematic pattern is a product of a rapid, early phase of synkinematic thermal maturation that has been obscured by a prolonged period of post-kinematic thermal maturation. Variations in basal heat flow, structural history, and general variability of hydrocarbon source rock organic composition, particularly at low thermal maturity levels, have resulted in a modest degree of scatter in the vitrinite reflectance-depth data. • Subsidence events within oblique-slip mobile zones occur quickly (hundreds of meters per million years). • Hydrocarbon source rock thermal maturity is related to structural position in convergent oblique-slip mobile zones. • Significant subsidence can occur far from collisional margins. • Rapid burial correlates with high rates of hydrocarbon generation driven by synorogenic subsidence. • Structural geometries within convergent oblique-slip mobile zones are mostly thick-skinned. • Modern basin modeling techniques can be used to predict hydrocarbon source rock maturity. [ABSTRACT FROM AUTHOR]

Continental margins vary in composition and configuration, resulting in complex structural geometries during deformation. One example is the Archean–Proterozoic boundary near Sudbury, Canada, where the Creighton-Victoria Deformation Zone (CVDZ) contains both reverse dip-slip and dextral strike-slip kinematic indicators. To resolve if these structures formed during a single transpression event or multiple overprinting events, the orientation, relative timing and style of the CVDZ are compared to those of adjacent regional structures. Regional fold axes and their axial planar foliation are subparallel to the steeply-plunging stretching lineation and steeply-dipping foliation, respectively, along the CVDZ. Phase equilibria modelling of syn-tectonic staurolite-chloritoid assemblages indicates that the regional folds and foliation formed at 480–565 °C, similar to temperatures estimated for the formation of dip-slip quartz crystallographic preferred orientations (CPO) along the CVDZ. This suggests that the CVDZ, regional folds and foliation formed during the same regional folding and reverse shearing event. Major lateral lithological changes and inflections in the orientation of the craton margin controlled the formation of structures, and evidence for regional transpression, such as strike-slip kinematic indicators, steeply-plunging stretching lineation, and obliquity of regional folds with respect to major shear zones, resulted from polyphase deformation and transcurrent reactivation of the Superior craton margin. • New structural analysis of the Superior craton margin near Sudbury, Canada. • Changes in lithology and orientation along the craton margin controlled deformation. • Quartz petrofabrics (EBSD) were analyzed to corroborate field mapping data. • Deformation temperatures from quartz petrofabrics constrained by phase equilibria. • Transcurrent reactivation of reverse shear zones resulted in apparent transpression. [ABSTRACT FROM AUTHOR]

The Pyrenees are the result of the structural inversion of a rift of general direction N110E, established at the articulation of the European and Iberian plates. This rift was created by left-lateral transtension with severe crustal thinning during the latest Early Cretaceous and Mid-Cretaceous. Its inversion, which led to the uplifting of the Pyrenean chain, took place gradually, by transpression from east to west, during the Late Cretaceous followed by an Eocene collision. From historical fieldwork, this note mainly focuses on the rifting period at the scale of the Pyrenean domain. It clearly shows the fundamental role of the stratigraphic approach in structural interpretation. Although synchronous at the scale of the Pyrenees, the Cretaceous extension is more important in the western part of the chain, near the Bay of Biscay. It is therefore at this location, within the Tardets-Mauléon Basin, that the various stages of creation and evolution of the rift could be clearly recognized with, successively: (1) an epirogenic pre-rifting stage, during which the facies lines, submeridian during the Jurassic, gradually change into N110E during the Neocomian before giving way, in the Early Cretaceous (Barremian-Gargasian), to a moderate acceleration of subsidence and, consequently, to the gentle uplift of a southern and western margin, future High Primary Belt (also often called Axial Zone) and Landes Plateau, initiating the next stage; (2) a major, brittle, newly identified rifting stage in the Latest Aptian (Clansayesian) and Early Albian. It is characterized by the installation of elongated lows on the downthrown side of transverse N20 normal faults, active diapirism of the Triassic evaporites and central detachment of the post-Triassic cover. During the Mid-Albian, a major surface of stratigraphic unconformity, often associated to uplift, erosion, and local centripetal gliding of the basin borders, marks a new structural organization, a rapid mantle ascent and the end of this episode. Although obscured by the later Pyrenean compression, the reconstructed basin geometry is interpreted as a “pull-apart” basin associated to a modest left-lateral motion; (3) a late rifting stage characterized by the collapse of the internal zones by rapid mantle cooling. The erosion of the coeval uplift of the southern High Primary Belt and the Landes Plateau feeds the accumulation of the thick, deep and transgressive unconformable formation of the Black Flysch of Mid-Albian to Early Cenomanian age in a larger coalescing basin. Faulting associated with a simple NS distension is only active on the last major border faults; (4) finally, a post-rift stage of Late Cretaceous age illustrated by the establishment of a passively subsiding basin, devoid of major deformations and whose heterogeneity of the previous depocenters is gradually erased. The Pyrenean transpression, later and less marked than in the eastern and central Pyrenees, allowed the conservation of most of these Cretaceous transtensive structures. Within the Tardets-Mauléon Basin, the Pernes and Col d’Urdach sector, the only Pyrenean location where the Mid-cretaceous transtension led to a proven underwater mantle exhumation, illustrates from outcrops the various stages that have marked the history of the Pyrenean Trough. Towards the east, along the Internal Metamorphic Zone, the Lourdes-Bagnères, Baronnies, Ballongue, Aulus and Saint-Paul de Fenouillet-Boucheville Basins, or those, further north like the Camarade and Quillan Basins, successively examined, testify to the same sedimentary and structural evolution. As in the case of the Tardets-Mauléon Basin, we deal here again with “pull-apart” type basins established on a thinned crust, arranged in transtensive or locally transpressive relays and separated by zones of thicker crust and shallower facies successions. The Mid-Albian unconformity is always present, heralding a general drowning of the North Pyrenean Trough and cessation of the extensional activity. The Pyrenean deformation, however, constitutes an obstacle for a precise geodynamic reconstruction, in particular in the eastern and central Pyrénées. Towards the west and north-west, in the South Aquitaine, Parentis and Basque-Cantabrian Basins, where Pyrenean deformation has far less obscured the rifting events, a very comparable Cretaceous geodynamic evolution is observed thus strengthening the present interpretation.

Geological mapping, structural data, and analytical modeling by Díez Fernández et al. (2021), https://doi.org/10.1029/2021tc006791 supported that the Central Unit belonged to a rootless Devonian suture zone contiguous to the SW of its exposure and under the upper section of the footwall to the Azuaga Fault. Late exhumation of the Central Unit was via extrusion from the upper‐middle crust under inclined triclinic sinistral transpression, which favored upright folding of the suture zone. Azor and coworkers argue that the upright folds that affect the Central Unit are local, despite geological maps and structural data demonstrate they are km‐scale and occur all across the Central Unit. Besides ignoring structural data regarding the kinematics of the Azuaga Fault, Azor et al. (2022), https://doi.org/10.1029/2021TC006982 fail to recognize the net upthrown movement of the NE side of the Azuaga Fault, as the Central Unit in that side is juxtaposed against syn‐orogenic strata that rest unconformably onto other metamorphic units in the SW side of the fault. Seismic data that image the Central Unit as a NE‐dipping rock package is used as an argument against the proposal by Díez Fernández et al. (2021), https://doi.org/10.1029/2021tc006791. However, the section of the Central Unit those data account for, are from a different part of the Central Unit, the real dip of some structures in the seismic image is not properly interpreted, and the model by Díez Fernández et al. (2021), https://doi.org/10.1029/2021tc006791 is compatible with a Central Unit that also dips to the NE. Overall, the model proposed by Díez Fernández et al. (2021), https://doi.org/10.1029/2021tc006791 remains valid. Key Points: The Central Unit belonged to a rootless Devonian suture zone contiguous to the SW of its exposureThe late exhumation of the Central Unit was via extrusion from the upper‐middle crust under inclined triclinic sinistral transpressionLate exhumation favored upright folding of the suture zone, exposing it in a tectonic window at the core of the Ossa‐Morena Complex [ABSTRACT FROM AUTHOR]

Directions of 683 faults located in the southeastern part of the Fennoscandian (Baltic) shield were statistically analyzed, and three orthogonal associations of fault systems were identified in the study area. According to the dynamic analysis of the fault systems and their associations, the main NW-striking faults belong to the fault network originating mainly from the early Paleoproterozoic. These faults functioned in the Paleoproterozoic during four main deformation stages: D1 – sinistral shear transtension and asymmetric rift genesis (2.1–1.9 Ga); D2 – sinistral shear transpression under oblique accretion and convergence (1.9 Ga); D3 – sinistral shear transpression under oblique collision (1.89–1.80 Ga); D4 – dextral strike-slip displacements at the background of complex escape tectonics of the late collision stage (1.80–1.78 Ga). The regional stress field changed as follows: D1 – northeast- or east-trending extension; D2 – northeast compression; D3 – sub-latitudinal compression; D4 – sub-meridian compression. Changes in dynamic loading conditions led to multiple kinematic inversions of the fault networks. Widespread transtension and transpression settings in the southeastern parts of the Baltic Shield give evidence of asymmetric rifting, oblique accretion and collision in the Paleoproterozoic, which must be taken in to account in geodynamic reconstructions.

The Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth's most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone. [ABSTRACT FROM AUTHOR]

[Display omitted] • Strain distribution across the Eyre Peninsula is heterogeneous. • Dextral transpression occurs in multiple shear zones including Kalinjala. • Granulite metamorphic conditions control the nature of deformation. • Metasediments were pinched-in between basement shear zones. • Post-Kimban brittle structures are related to Gondwana breakup. • Enhances structural correlations with Terre Adélie Land, Antarctica. The southern edge of the Eyre Peninsula, experienced a separation from proto-Antarctica in the Cretaceous and has been projected to extend into Terre Adélie Craton, Antarctica. The Archaean and Palaeoproterozoic rocks of the southern Eyre Peninsula, have been modified by the Kimban Orogeny (~1730 – 1690 Ma) with the development of the regionally extensive Kalinjala Shear Zone, which has been correlated with the Mertz Shear Zone in Antarctica. In this contribution, new structural observations associated with the granulite facies Kalinjala Shear Zone, together with other shear zones, all showing similar kinematics of dextral top-to-the-north transport will be described. The Kimban Orogeny overprints and reworks a major lithospheric boundary between the Gawler Craton and a sequence of preceding events related to the ~ 1850 Ma Cornian Orogeny. Shear zones were initiated during the early stage of the Kimban Orogeny (KD 1) in a dextral simple-shear regime, transitioning into a pure-shear (KD 2) dominated regime. With shortenings of > 90% in the Kalinjala Shear Zone localized into regions containing pre-existing Tourneford Metdolerite Dykes emplaced at ~ 1810 Ma into the granites of the Donington Suite (1850–1843 Ma) and a basement of 2000–1859 Ma paragneisses. Geometrical relationships reveal the operation of oblique extrusion during the Kimban Orogeny, where a coaxial component acted sub-horizontal and orthogonal to the trend of the Kalinjala Shear Zone. Regions of low-strain and a 'pinched-in' and inverted sequence of Mesoproterozoic metasedimentary cover, the Hutchison Supergroup, are bounded by major km-scale shear zones with steep west-dipping tectonic contacts. Post-Kimban subvertical east–west-trending joints and faults record a rifting event which can be related to a Gondwana breakup. With post-rift Neogene fault activity recording additional tectonic episodes where pre-existing basement structures exert significant control on their orientation and distribution. Palaeogeographical reconstructions between the Eyre Peninsula and the Terre Adélie Craton, based on matching basement geology and structural style, are compared and reconciled with this new information. [ABSTRACT FROM AUTHOR]

Understanding the processes and mechanisms responsible for exhumation are essential for determining the evolution of landscapes. Our knowledge of these issues in continental convergent margins is still incomplete despite decades of research. Here, we present a record of exhumation rates obtained from thermochronology across the collision zone of the Himalayan‐Tibetan orogen, which has been carved by the dextral Karakoram fault (KF) along its western margin. Our thermochronology results across the KF suggest that transpression controlled exhumation from ∼10 to 8 Ma. Exhumation rates at the margin of the Tibetan plateau, in the SE Karakoram range, to the north of the KF are twice as high as the Ladakh range, to the south of the KF, since at least middle Miocene. We hypothesize that rapid exhumation of the Tibetan margin was in response to topographic uplift and subsequent erosion due to the convective removal of the lower lithosphere, triggered by the rollback of the subducting Indian lower crust during the Oligocene‐Miocene in an early phase. Our thermochronology results document an additional two‐fold increase in the exhumation rates of the Tibetan margin since the late Mio‐Pliocene. We propose that the underthrusting of the Indian Plate below Tibet during the late Mio‐Pliocene was responsible for this additional increase of exhumation rates of the Tibetan margin in the late phase. These exhumation rates are in good agreement with the topographic slope, relief, and channel steepness data of these regions. Thus, the coupling of tectonics and topography dictated the exhumation patterns since late Mio‐Pliocene. Plain Language Summary: The increased uplift of the SE Karakoram range/SW Tibet in comparison to the Ladakh range was driven by two distinct tectonic processes over time, that is, delamination of Tibetan lithosphere and asthenospheric upwelling in the mid‐Miocene to late Miocene and underthrusting of the Indian lithosphere beneath Tibet since Pliocene. Key Points: The SW Tibetan Plateau north of the Karakoram fault has experienced faster exhumation than the Ladakh range since at least middle MioceneDelamination of Tibetan lithosphere and asthenosphere upwelling in the mid‐to‐Late Miocene controlled the exhumation of SW TibetUnderthrusting of the Indian Plate beneath SW Tibet caused a twofold increase in exhumation rates of Karakoram range since Mio‐Pliocene [ABSTRACT FROM AUTHOR]

Research subject. Large and super-large orogenic gold deposits are widely distributed across all continents. This work was aimed at characterizing 24 giant facilities with reserves and resources of more than 500 tons of metal.Materials and methods. The work was based on the authors’ long-term fieldwork research into large and super-large gold deposits in Central Asia and the North-East of the Russian Arctic. In addition, an extensive bibliographic analysis of publications devoted to the largest gold deposits in the world was carried out.Results. A structural analysis showed that the formation of these deposits underwent two main stages. The early – subduction stage – was characterized by the development of gentle disturbances, such as thrusts, thrust nappies, viscous discontinuities and crushing zones, while the structural paragenesis included isocline lying folds and cleavage of the axial surface. The second stage – collision-transpression – began with the deformation of the previously formed structure into open and compressed folds with steep axial surfaces; as a result of further compression, a series of longitudinal discontinuous disturbances developed. An oblique collision of interacting plates lead to the development of shear transpression structural paragenesis, in which oblique cracks predominate. It is established that, in orogenic gold deposits, different stages were characterized by ore-controlling and ore-bearing structures. The binding of ore-bearing disturbances to different stages enabled isolation of deposits of various types that differ in structural and morphological features. The main characteristics of the identified types of deposits are provided. The formation of these deposits occurred during convergent processes, with the ore-controlling structures being a surface manifestation of the movement of block terrains along the surface of the detachment.Results. It is concluded that the surface of the detachment is not only a tectonic zone, but also a channel that provides a link between various deep levels of the subduction zone, from where ore-bearing hydrothermal fluids emerge.

Previous paleomagnetic studies performed in the central North-Algeria (Chellif and Mitidja basins) on Neogene formations pointed out tectonic clockwise blocks rotations. This deformation pattern was interpreted as resulting from a bookshelf neotectonics, consequence of the Africa-Eurasia plates convergence. A new paleomagnetic study was conducted on the Neogene volcanic rocks outcropping in the northwestern Algeria (Marset Ben Mhidi, Aïn Temouchent, Tifaraouine area). The obtained stable remanent magnetization is mainly carried by Ti-poor titanomagnetite. The paleomagnetic data show that, since the lava emplacement, the northwestern Algeria underwent a mean moderate clockwise block rotation of 9.3° ± 4.5°. For the Algerian margin, this confirms a context of transpression and blocks rotations in a strike-slip tectonic setting. A decreasing deformation gradient from the E to the W affected the different basins of this margin, from strong rotations within the Mitidja, to the moderate ones in the Chellif and to Marset Ben Mhidi, Aïn Temouchent, Tifaraouine area, where rotation magnitudes are significantly lower. [ABSTRACT FROM AUTHOR]

This study investigates how strain is partitioned within hot orogenic belts in a context of plate reorganization. We document crustal‐scale strike‐slip shear zones, plate‐scale oroclinal bending, and widespread exhumation of deep crustal domains in the core of nascent Pangea plate during late‐Variscan times (ca. 310–290 Ma). The role of strain partitioning in the finite strain patterns is first highlighted at regional scale by a new detailed structural, kinematic, and petrologic analysis of the Chiroulet and Lesponne gneiss domes in the Pyrenees. Vertical strain partitioning in response to N‐S shortening‐dominated dextral transpression is secondly documented at the scale of the Variscan domains of the Pyrenees, based on a synthesis of recent geochronological, thermobarometrical, and structural data. We show that the mid‐lower crust is affected by eastward lateral flow and the upper crust by penetrative thickening and localized thrusting. Local transverse extension in the mid‐lower crust illustrates gravity‐driven instability favored by the accumulation of anatectic melts in gneiss domes. Finally, we highlight the respective position of extended and shortened area within the Variscan belt during late‐Carboniferous/early‐Permian that suggests large‐scale lateral strain partitioning and reorganization of the weak continental crust in the core of the Pangea. This distribution appears significantly different from other orogens in a similar context of oroclinal bending, resulting in localization of the shortened zones in the core of the belt. This highlights the influence of the initial and boundary conditions, such as the obliquity of the belt to the applied stress field and the location of free‐boundaries, on finite strain patterns. Key Points: The Variscan crust of Pyrenees documents vertical strain partitioning: lateral flow versus upper‐crust thickening in the core of PangeaWe document horizontal strain partitioning between extensional and compressional domains during plate‐scale oroclinal bendingLarge‐scale strain patterns of bending hot orogens reflect initial conditions (at the onset of bending) and evolving free‐boundaries [ABSTRACT FROM AUTHOR]

The opposite-sense fault block rotation across the continental strike-slip faulting plays an important role in accommodating crustal deformation in the north of the East Iran orogen. This research constrains the post-Neogene kinematics of the NW-SE to E-W left-lateral transpressional zones at the northern termination of the N-S striking right-lateral Neh fault system in the East Iran orogen. Using two case studies, we analyzed the NW-SE Birjand splay and the E-W Shekarab transpression zone by analysis of satellite images, structural features, fault geometry and kinematics, GPS (Global Positioning System) velocities, fault- and earthquake-slip stress inversion, and paleomagnetic data. Our results show two distinctive regions of opposite-sense fault block rotations and with different rotation rates. As an asymmetric arc, the Birjand splay displays a transition from the prevailing N-S right lateral shear in the east to NW-SE left lateral transpression in the middle and E-W left lateral shear in the west. In the east, with clockwise fault block rotation, the N-S right lateral faults and the NW-SE oblique left-lateral reverse faults constitute push-ups through the restraining fault bends. In the west, with counterclockwise fault block rotation, the Shekarab transpression zone is associated with the duplex, pop-up, and shear folds. Our suggested kinematic model reveals that the N-S right-lateral shear is consumed on the left-lateral transpressional zones through the vertical axis fault block rotation. This led to an E-W shortening and N-S along-strike lengthening in the East Iran orogen. This research improves our understanding of how opposite fault block rotations accommodate India- and Eurasia-Arabia convergence in the north of the East Iran orogen. The suggested model has implications in the kinematic evolution of intra-plate strike-slip faulting through continental collision tectonics.

The north-vergent Balkan fold–thrust belt of the Balkanide orogen, extending from northeast Serbia to the Black Sea region, was formed during at least two Alpine compressional events. However, remnants of the Variscan orogen are still preserved in its western and central parts. In the central part (Central Stara Planina Mountains), two pre-Permian metamorphic complexes of contrasting metamorphic degrees, the low-grade Stara Planina and high-grade Sredna Gora complexes, are juxtaposed along a major Variscan tectonic zone and intruded by voluminous granitoids of previously unknown age. Here, we present an extensive structural and U–Pb (TIMS and LA-ICP-MS) geochronological analysis, constraining several magmatic and tectonic events in the pre-Alpine evolution of the area. For the first time, early Cambrian magmatism (531.7 ± 1.5 Ma/519.4 ± 2 Ma) is reported from a granite intruding the low-grade Stara Planina complex. The juxtaposition of the metamorphic complexes before 314 Ma was followed by a transpressional stage between 313 and 306 Ma. The last Variscan penetrative ductile deformation was associated with the final emplacement stages of the Ambaritsa sheet-like pluton at about 306 Ma under still ongoing compression. In addition, at least two post-Variscan magmatic pulses of granitoid magmatism (at ca. 306–304 Ma and 250 Ma) have been distinguished in the studied area. Later, Alpine ductile to brittle deformational events led to an additional reworking of the Variscan edifice. [ABSTRACT FROM AUTHOR]

Jhelum Fault is the north–south-oriented major structural lineament originating from the Hazara-Kashmir Syntaxis and extending southwards towards the Mangla Lake. Geographic extent, nature and significance of Jhelum Fault are the subjects which have been approached by different researchers in the past. The previous research provides enough evidence for the presence of Jhelum Fault as well as they discourse its surface extent. None of the previous research addresses the subsurface model of this fault; consequently, its surface extent has been ambiguous and variably reported. The current research takes into account both the surface lineament as well as the subsurface behaviour of the deformed strata to draft the most reasonable depiction of this fault. Field data were coupled with satellite image of 1.5 m ground resolution to produce the geological map of the study area at 1:25,000 scale. The subsurface model was created along four traverse lines by considering the lateral extent of the structures and their shifting trends on the geological map. The stratigraphic package was taken from the nearby hydrocarbon exploratory well data (Missakeswal-01 well of OGDCL) as no rocks older than middle to late Miocene were exposed in the area. The consistent through-going map extents of many faults in the study area prove that faults are playing the major role in the tectonic evolution of the Jhelum Fault Zone. In the subsurface model, the same faults show very little stratigraphic throw, which signify the major stress component to be associated more with wrenching than pure compression. Therefore, most faults in the area are of transpressional nature having dominant lateral component with relatively smaller push towards west on steeply east dipping faults. The model also shows the positive flower structure with dominantly west verging fault system with few east verging back thrusts. The subsurface proposed model shows that the Jhelum Fault is extendible southwards to the Mangla Lake in the subsurface; however, it acts like a continuous shear zone on the surface where there all the shearing is accommodated by tight refolded fold axes. The east–west shortening does not exceed 14.5% which shows smaller compression in the study area. The 3D model further clarifies the model by showing the consistency of the fault system along strike. [ABSTRACT FROM AUTHOR]

Detailed structural and kinematic analyses of deformed structures in the Sanandaj-Sirjan Metamorphic Belt in the Ghouri area revealed the occurrence of three gneissic sub-domes with semi-elliptical shapes with their major axes parallel to the Zagros Transpression Zone boundary (NW-SE direction). These sub-domes are cored by sheared quartzo-feldspathic gneisses which surrounded by sequences consisting of garnet amphibolites, phyllites, phyllonites, muscovite schists, and deformed conglomerates. The Kuh-e-Zard, Chah-Sabz, and Chah-Goni sub-domes resulted from the interaction of the lower to middle continental crust and hot subducting Tethyan oceanic crust during subduction/continental collision. These sub-domes were squeezed between thrusts in the Zagros dextral transpression zone. The variations in the kinematic vorticity and strain estimates revealed that sub-simple shear transpressional deformation is highly heterogeneous in each sub-domes. [ABSTRACT FROM AUTHOR]

A 3.6 km thick stack of mid-crustal deformed Precambrian rocks is associated with the North Roe Nappe (NRN) and Walls Boundary Fault in the northernmost Scottish Caledonides on NW Mainland Shetland. The greenschist- to amphibolite-facies rocks display unusually complex and heterogeneous combinations of coaxial and non-coaxial transpressional deformation. Previously published isotopic dating, together with new detailed field mapping and microstructural characterisation show that the NRN preserves a record of Neoarchaean, Neoproterozoic (Knoydartian) and Ordovician-Silurian (Caledonian) overprinting deformation and metamorphism. Neoarchaean events in the Uyea Gneiss Complex located in its footwall are reworked by younger events in the overlying nappe pile. The main ductile fabrics were formed during Caledonian top-to-the W/NW thrusting and top-to-the N sinistral shearing, with subordinate regions of top- to-the E extensional and NNE-SSW dextral shearing. In lower parts of the NRN, these different kinematic domains are texturally indistinguishable and overprinting relationships are absent. At higher levels, top-to-the-W/NW thrust-related fabrics are consistently overprinted by top-to-the-N/NE sinistral shearing. The highly partitioned transpressional deformation shows similarities with equivalent rocks of the Moine Nappe in NW Scotland. • Precambrian metamorphic rocks in NW Shetland preserve polyphase and heterogeneous transpressional deformation. • The main ductile fabrics formed during regional Caledonian (Scandian) thrusting and sinistral shearing. • Events of different Scandian age dominate in different parts of the transpressional thrust wedge. • The area vividly illustrates the kinematic complexity of natural transpression zones in mid-crustal settings. [ABSTRACT FROM AUTHOR]

This study explores the coupled processes of structural inversion and fluid migration around the northeastern part of the Mesozoic Chungnam Basin in the southwestern Korean Peninsula, focusing on quartz vein systems genetically linked to an orogenic gold deposit. Our results show that the inversion structures reflect the coexistence of strike-slip simple shear and pure shear components caused by NW–SE crustal shortening, leading to a transpressional deformation model. The quartz veins, filling the high-angle faults with a reverse slip component and adjacent hydrofractured wall rocks, represent transient fluid flow related to seismic faulting and fault valving during the inversion. New K–Ar ages of illite polytypes in fault gouges, determined using the Illite-age-analysis (IAA) method, indicate Late Jurassic–Early Cretaceous fault reactivations. Notably, ca. 160 Ma 2M 1 illite age from a fault zone filled with an orogenic gold–bearing quartz vein indicates that the inversion and auriferous hydrothermal fluid flow started with a magmatic quiescence in the southern Korean Peninsula likely owing to the flat subduction of the Paleo-Pacific Plate. Our findings suggest that the orogenic gold–bearing vein system was likely sourced from the subcrustal metamorphic fluid in the flat subduction zone of the Mesozoic East Asian Continental margin. [Display omitted] • Mesozoic basement-involved transpressional inversion in the SW Korean Peninsula. • Vein system showing syntectonic features within cyclic stress fluctuation. • Metamorphic fluid circulation during the flat subduction of the Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Shillong plateau in northeast India records Archean/Proterozoic to Cenozoic histories. • Shillong group of rocks present as a supracrustal unit within the plateau which preserves multiple deformation events. • Microstructural investigations on shear zone rocks suggest a deformation sequence for the study area. • Kinematic and vorticity analyses indicate the transpressive nature of the Barapani Shear Zone (BSZ). • The BSZ is represented here as an intraterrane shear zone that is restricted within the plateau only. The analysis of shear zone kinematics plays a crucial role in understanding the tectonics at micro-, meso-, and regional scales within a given terrane. This study focuses on investigating the kinematics of prominent asymmetric structural features preserved within the Barapani Shear Zone (BSZ). These features are utilized to establish vorticity numbers in relation to the reference frames of the BSZ. Typically, shear zones provide finite values for kinematics and vorticity numbers. The BSZ is identified as an intraterrane, multiply deformed shear zone within the Shillong Plateau, which exhibits varying kinematics and vorticity numbers measured across different deformation zones. The research reveals that the BSZ underwent successive D 1 , D 2 , D 3 , and D 4 events, resulting in preserved S 1 , S 2 , and S 3 planar fabrics, with D 4 evidenced by brittle deformation features. However, determining shear zone kinematics purely based on the orientation of these planar fabrics and mineral lineation with respect to the external reference frame is insufficient. Consequently, this study calculates vorticity numbers and kinematics by considering both the external and internal reference frames of the BSZ. The study suggests that superposed transpressional tectonics prevailed during D 2 and D 3 events. [ABSTRACT FROM AUTHOR]