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Abstract\nKEY POINTSThe Browns Creek Au–Cu skarn is restricted to a 50 m-wide fault zone developed in an interbedded sequence of Upper Ordovician mafic Blayney Volcanics and Cowriga Limestone Member adjacent to the mid-Silurian (434–425 Ma) Carcoar Granodiorite. The mineralised skarns are hosted within and controlled by the Mount David/4000E Fault zone, a dextral transtensional strike-slip fault that in cross-section has the form of a negative flower structure. This is consistent with components of dextral strike-slip motion recorded on regional faults likely guiding magma emplacement during the Benambran Orogeny. The skarns comprise a barren Stage 1 prograde pyroxene–garnet–wollastonite–anorthite assemblage followed by Stage 2 hornblende–biotite–epidote–magnetite–Fe–Cu–As sulfide skarn. These are overprinted by the strongly mineralised Stage 3 retrograde epidote–andradite garnet–chlorite Cu–Au skarn containing the bornite–chalcopyrite–chalcocite–gold ore, when probable magmatic-dominated hydrothermal fluids were channelled through the previously skarned strike-slip fault system that had become a permeable fault zone. Stage 4 sheeted vein-hosted prehnite–epidote–chlorite Au–Cu skarn formed when the strike-slip fault subsequently failed in tension to form gold-rich vertical extensional veins. Conditions for extensional fault reactivation and vein formation are discussed in terms of reshear criteria and fluid overpressure. The age of the mineralisation is constrained by late-stage monzonitic dykes that both crosscut and are themselves skarned by stages 3 and 4 assemblages. These co-magmatic dykes were dated at ca 435–425 Ma, which closely corresponds with the age of the Carcoar Granodiorite itself. Stable and radiogenic isotopes indicate that hydrothermal fluids associated with prograde and retrograde skarns are within the range for magmatic fluids with some mixing with fluids of meteoric origin during later stages of mineralisation. The Browns Creek Au–Cu skarn is typical of Au-skarns worldwide and is linked to mid-Silurian magmatism at a late stage in the Benambran Orogeny.The Browns Creek Au–Cu skarn formed in Upper Ordovician mafic volcanics and interbedded limestone adjacent to a mid-Silurian granodiorite intrusion.The mineralised skarns are contained within a fault zone that developed at the granodiorite margin during magma emplacement at a late stage in the Benambran Orogeny.Retrograde skarns contain Au–Cu mineralisation characterised by bornite; chalcopyrite; chalcocite and gold with grades typically in the range 1–10 g/t Au and 0.3–0.4 wt% Cu.Geological relationships, age dating, stable and radiogenic isotopes all indicate that hydrothermal fluids derived from the granodiorite intrusion were the cause of skarning and Au–Cu mineralisation when channelled through the fault zone. [ABSTRACT FROM AUTHOR]

Pull-apart basins are depressions formed at releasing bends or steps in strike-slip fault systems, between two parallel vertical strike-slip fault sections. In the present study, the geometry of Udaeta Lake, located in the central section of the Magellan-Fagnano Fault System (MFFS) and previously defined by some authors as a pull-apart basin, is analysed. The application of multiple geophysical methods, constrained by surface geological information, enabled us to reveal the subsurface geometry of a section of the MFFS, Udaeta Lake area. Magnetic, gravimetric and detailed topographic profiles, together with vertical electrical soundings were surveyed. The obtained results were compared with fieldwork data. This combined methodology allowed the identification of a transtensional zone with two E-W main sinistral strike-slip faults with a normal component that control the North and South coasts of the lake. This central depression occupied by the lake, with a depth of ∼30 m, is also affected by inferred NE subparallel faults. The geophysical characterization of the MFFS also supports the influence of this fault system on the formation of some water bodies located along the fault zone. Finally, in spite of the lack of detailed geological and structural data, Udaeta Lake we suggest a genesis consistent with a pull-apart basin model. This work constitutes an important contribution to understand earthquake rupture parameters and pattern of surface and in-depth deformation and so, improve knowledge of the seismological behaviour of the MFFS. [ABSTRACT FROM AUTHOR]

By mechanical analysis to analyze the mechanism of wheel hub stud rotating and transtensional when taking strenuous test to forklift transmission,if pre-tightening force between rim and wheel hub is not enough because of the unqualified nut,Ground braking force is more than friction force when truck brakes,rim rotates to the brake drum and nut,wheel hub stud bears extra twisting force between rim and nut,causing wheel hub stud rotating and transtesional. Learning the mechanism of wheel hub stud rotating and transtensional is helpful to know further the wheel hub stud working force condition,and it can give theoretical basis to the failure analysis of wheel hub stud and nut

The Åkerlandet, Järvsand, and Laisvall deposits in Sweden are calcite-fluorite-sulfide vein deposits and occurrences located close to the current erosional front of the Caledonian orogen and hosted by crystalline basement rocks in the Fennoscandian Shield. At Laisvall, basement-hosted veinlets occur beneath Ediacaran to Cambrian sandstones that host a strata-bound Pb-Zn deposit. The mineralized fractures at Åkerlandet and Järvsand occur along fault systems oriented N-S to NNW-SSE. Veins or veinlets strike NNW-SSE and NW-SE at Åkerlandet, NNE-SSW at Järvsand, and NNW-SSE and NNE-SSW to NE-SW at Laisvall. At Åkerlandet and Järvsand, fractures acted as conduits for hydrothermal fluids of variable composition and formed during separate tectonic events. At Åkerlandet, the fault zone with NNW-SSE strike shows kinematic indicators consistent with ~NE-SW bulk horizontal extension. At Järvsand, the calcite-fluorite-galena veins formed along R-Riedel shears related to the host N-S to NNW-SSE fault system. The kinematic indicators are consistent with ~NW-SE bulk horizontal extension, similar to the extensional deformation during the later part of the Caledonian orogeny (Silurian to Devonian). At Åkerlandet, adularia-quartz deposition was followed by sphalerite ± galena and finally by precipitation of fluorite and calcite. Ar-Ar thermochronology of a single adularia sample did not yield a well-defined plateau age but the gas released at higher temperatures suggests an early Tonian (980 to 950 Ma) crystallization age, i.e., during the later part of the Sveconorwegian orogeny, although the data do not exclude other less likely interpretations. Previous fluid inclusion microthermometry and geochronological studies and new petrographic and geochemical results suggest that sphalerite ± galena mineralization formed from saline, relatively oxidizing, moderate-temperature, and slightly acidic hydrothermal fluids, either during the Ediacaran or the Middle Ordovician. Metals and HS were derived from local basement rocks. Based on petrographic evidence, rare earth element composition, and S, C, and O isotope data, fluorite and calcite precipitated under near neutral and relatively reducing conditions. Occurrence of solid bitumen in veins at Åkerlandet and C and O isotope data of calcite at Åkerlandet and in the Laisvall basement veinlets suggest that the precipitation of calcite and fluorite was triggered by interaction of hot and evolved hydrothermal fluids (Sr/Sr = 0.718-0.732) with organic matter. Structural, petrographic, and geochemical data at Laisvall suggest that the basement structures hosting calcite-fluorite ± pyrite veinlets were utilized in the Middle Ordovician as the plumbing system for the oxidizing, slightly acidic, metal-bearing brines that caused the economic Pb-Zn mineralization in the overlying sandstones. [ABSTRACT FROM AUTHOR]

Sedimentary basins within fold-and-thrust belts preserve the structural record of complex deformations and are essential to many orogenic systems worldwide. One of the component of such deformations is strike-slip tectonics. This research uses high-quality, three-dimensional seismic reflection data to investigate the geometry and kinematics of strike-slip faults developed within a geologically complex region in the Upper Assam foreland basin, NE India. Faults in the basin have a dominant NE-SW trend, with most faults in the SE and SW parts exhibiting sinistral strike-slip. These lateral movements are evidenced by extensional horsetail splay faults, negative flower structures, and minor transfer faults. The displacement profiles of the strike-slip faults also reveal complex segmentation, linkage, and mechanical interactions at different structural levels, indicating their prolonged histories and development. Tectonic tilts of the basin, along with sediment loading from the bordering fold-and-thrust belts over the geologic time, structurally changed the basin configuration giving rise to strike-slip deformations in the study region. These findings contribute to our knowledge of sedimentary basins within fold-and-thrust belts and their structural records of complex deformations. [Display omitted] • Unravels strike-slip tectonics within the Upper Assam foreland basin. • Elucidates structural indicators associated with strike-slip fault movement. • Deciphers the kinematics of strike-slip faults in the Dibrugarh filed. [ABSTRACT FROM AUTHOR]

This outcrop-based study reports diffuse joints and veins, normal to strike-slip fault zones and minor folds that developed, from Miocene to Quaternary, within the clastic to siliceous sedimentary record of the forearc Pisco Basin of southern Peru. Patterns, orientations, dimensional parameters and other outcrop-scale characteristics of the various deformation features are illustrated and their genetic mechanisms and timing of development are inferred. These new structural data and interpretations allow a better constraint of the structural style and evolution of the Pisco Basin, and can represent useful guidelines for characterizing the outcrop-scale deformation affecting similar forearc basins along the Peruvian coast. Major results of this study are that the development of the documented deformation features, their patterns, dimensional parameters and kinematics seem influenced by local perturbations of the paleostress field by mechanic processes partly independent of plate tectonics forces. These processes include strain localization on both pre-existing and progressively forming new structural discontinuities, and cyclic switches of the horizontal, principal stress axes σ2 and σ3. In particular, we discuss how different normal fault patterns, from sub-parallel to multidirectional/polygonal, could form in a same deformation phase in response of the local σ2/σ3 magnitude ratio, as an evolution of stratabound, mutually orthogonal vein sets. [ABSTRACT FROM AUTHOR]

Sinistral and dextral en echelon hybrid calcite veins are exposed on the southern margin of the Bristol Channel Basin, North Somerset on a Liassic carbonate platform. These hybrid veins are transitional between pure extensional (mode I) and shear fractures (mode II, mode III) and experienced both extensional and shear displacements during their formation. In the study area they occur in conjugate sets with the conjugate angle ranging between 10° and 50°. Based on the kinematic analysis of these veins a new model for the opening of the Bristol Channel is proposed. [Copyright &y& Elsevier]

Abstract: This study defines the Late Cenozoic stress regimes acting around the Bolu Basin along the North Anatolian Fault in northwestern Turkey. The inferred regional stress regime, obtained from the inversion of measured fault-slip vectors as well as focal mechanism solutions, is significant and induces the right-lateral displacement of the North Anatolian Fault. The field observations have also revealed extensional structures in and around the Bolu Basin. These extensional structures can be interpreted as either a local effect of the regional transtensional stress regime or as the result of the interaction of the fault geometries of the dextral Duzce Fault and the southern escarpment of the North Anatolian Fault, bordering the Bolu Basin in the north and in the south, respectively. The inversion of slip vectors measured on fault planes indicates that a strike-slip stress regime with consistent NW- and NE-trending axes is dominant. Stress ratio (R) values provided by inversion of slip vectors measured on both major and minor faults and field observations show significant variations of principal stress magnitudes within the strike-slip stress regime resulting in older transpression to younger transtension. These two stress states, producing dextral displacement along NAF, are coaxial with a consistent NE-trending σ 3 axis. The earthquake focal mechanism inversions confirm that the transtensional stress regime has continued into recent times, having identical horizontal stress axis directions, characterized by NW and NE-trending σ 1 and σ 3 axes, respectively. A locally consistent NE-trending extensional, normal faulting regime is also seen in the Bolu Basin. The stress-tensor change within the strike-slip stress regime can be explained by variations in horizontal stress magnitudes that probably occurred in Quaternary times as a result of the westward extrusion of the Anatolian block. [Copyright &y& Elsevier]

• There are both extensional and dextral strike-slip systems in the Bohai Bay Basin. • Dextral deformation occurred in the Jizhong Depression at the Mid-Eocene. • The Bohai Bay Basin has become a complex pull-apart basin since Mid-Eocene. • Oblique subduction of the Pacific Plate may cause the back-arc dextral stress field. The Cenozoic back-arc rift basins along the continental margin of East Asia are featured by both extensional and dextral deformation systems. Here we investigate the timing and interaction of these two types of systems, based on seismic data, stratigraphic isopach maps and drilling data in the Jizhong Depression in the northwestern Bohai Bay Basin (BBB), East China. The results show the rifting was initiated as early as the Eocene while the dextral deformation did not occur until ca. 42 Ma. The Jizhong Depression changed from a simple rift basin with boundary faults to the west to a geometrically more complex dextral transtensional basin at ca. 42 Ma. This event was roughly concordant with the initial dextral slip on the Tan-Lu Fault lying at the eastern BBB, and together they transformed the BBB into a complex pull-apart rift basin. The tectonic reorganization of the BBB was probably the response to the change from an orthogonal to an oblique subduction of the Pacific Plate beneath East Asia at that time. [ABSTRACT FROM AUTHOR]

This work provides a comprehensive GIS mapping integrated with geological and geophysical data (magnetic and gravimetric) to reveal the interplay between (i) magmatism and volcanic activity, (ii) intra-mountain basin development and (iii) large-scale faulting/tectonic features in the post-collisional setting of the East Carpathians. The geological, geophysical and tectonic data of the Călimani-Gurghiu-Harghita range (CGH) confirm the contemporaneous formation of basins and volcanic activity. The two phenomena propagated southwards in time, parallel to the collisional front, in close relation to the development of the fault systems. The geometry of the faults and alignment of volcanic edifices indicate both strike-slip and normal faulting, with no rotation. The main volcanic range and main tectonic basins evolved along a regional NNW-SSE striking sinistral transtensional fault zone with left stepping stepovers and pull-apart basins in the transfer areas. The fault zones probably acted as least resistance areas that fostered the development of magma ascent paths and plumbing systems. These connected the volcanic centers with numerous magma chambers emplaced at the upper mantle – lower crust boundary and throughout the lower and upper crust. The magma generation is most likely a result of the interplay between large-scale transtensional systems that induced decompression in the previously metasomatised mantle, and asthenosphere upwelling in the post-collisional East Carpathian orogen. • The article discusses the tectonic and structural control of post-collisional volcanism vs. typical arc volcanism. • The Călimani-Gurghiu-Harghita range is an example of post-collisional volcanism, showing ~ 160 km length. • The N-S development of tectonic structures at 10-0.03 Ma is following the mountain building processes in the East Carpathians. • The history of deformation and evolution of the stress field is combined with volume of erupted magma along the CGH. [ABSTRACT FROM AUTHOR]