Journal articles: 'Emplacement kinematics'

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Abu, Clara, Christopher A. L. Jackson, and Malcolm Francis. "Strike-slip overprinting of initial co-axial shortening within the toe region of a submarine landslide and a model for basal shear surface growth: a case study from the Angoche Basin, offshore Mozambique." Journal of the Geological Society 179, no. 2 (October 18, 2021): jgs2021–032. http://dx.doi.org/10.1144/jgs2021-032.

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Submarine landslides (slides) are some of the most voluminous sediment gravity-flows on Earth and they dominate the stratigraphic record of many sedimentary basins. Their general kinematics and internal structure are relatively well-understood. However, how slides increase in volume and internally deform as they evolve, and how these processes relate, in time and space, to the growth of their basal (shear) zone, are poorly understood. We here use three high-resolution 3D seismic surveys from the Angoche Basin, offshore Mozambique to map strain within a shallowly buried, large, and thus seismically well-imaged slide (c. 530 km3). We document several key kinematic indicators, including broadly NW-trending lateral margins and longitudinal shears bounding and within the slide body, respectively, and broadly NE-trending symmetric pop-up blocks in the slide toe. Approximately 7 km downdip of the slide toe wall, thrusts and related folds also occur within otherwise undeformed slope material, with thrusts detaching downwards onto the downslope continuation of the basal shear zone underlying the slide body. Based on the style, trend and distribution of these features, and their cross-cutting relationships, we propose an emplacement model involving two distinct phases of deformation: (i) bulk shortening, parallel to the overall SE-directed emplacement direction, with contractional shear strains reaching c. 8%; and (ii) the development of broadly emplacement direction-parallel shear zones that offset the earlier-formed shortening structures. We infer that the contractional strains basinward of the slide body formed due to cryptic basinward propagation of the basal shear zone ahead of, and to accommodate updip sliding and shortening associated with, the entire slide mass. Our study demonstrates the value of using 3D seismic reflection data to reveal slide emplacement kinematics, especially the multiphase, non-coaxial nature of deformation, and the dynamics of basal shear zone growth.

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Ramsay, John G. "Emplacement kinematics of a granite diapir: the Chindamora batholith, Zimbabwe." Journal of Structural Geology 11, no. 1-2 (January 1989): 191–209. http://dx.doi.org/10.1016/0191-8141(89)90043-6.

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Benn, Keith. "Anisotropy of magnetic susceptibility fabrics in syntectonic plutons as tectonic strain markers: the example of the Canso pluton, Meguma Terrane, Nova Scotia." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 147–58. http://dx.doi.org/10.1017/s1755691009016028.

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ABSTRACTThe anisotropy of magnetic susceptibility (AMS) is widely and routinely used to measure the preferred orientations of Fe-rich minerals in undeformed and weakly deformed granite plutons. The interpretation of the mapped AMS fabrics depends on rock-textural observations, on the map patterns of the fabrics in plutons, and on comparisons of the pluton fabrics to tectonic structures in the country rocks. The AMS may document emplacement-flow related fabrics, but the emplacement fabrics may be reworked or completely overprinted by rather weak tectonic strains of the magma mush or the cooling pluton, especially in syntectonic intrusions. The Late Devonian Canso granite pluton is an excellent example of overprinting of emplacement fabrics by weak tectonic strains. The Canso pluton was emplaced ca. 370 Ma along the boundary between the Meguma and Avalon tectonic terranes, in the northern Appalachian orogen. The AMS was mapped along two traverses that cross the pluton and that are perpendicular to the terrane boundary. Textural evidence suggests the rocks underwent very modest post-full crystallisation strains. The AMS records the dextral transcurrent shearing that occurred on the terrane boundary during emplacement and cooling of the Canso pluton, supporting interpretations that weakly deformed syntectonic granites can be used as indicators of regional bulk kinematics. AMS fabrics in Late Devonian granites of the Meguma Terrane suggest partitioning of the non-coaxial shearing into the terrane bounding fault, with pure-shear dominated deformation further from the fault. Numerical simulations suggest that the kinematics recorded by the fabrics in the Canso pluton was simple-shear, or transpression or transpression with small components of pure shear oriented perpendicular to the bounding shear zone.

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Mugnier, J. L., and L. Endignoux. "Kinematics and velovity of thrust sheets emplacement: a numerical simulation (In French)." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 29, no. 2 (March 1992): A73. http://dx.doi.org/10.1016/0148-9062(92)92134-x.

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Beslier, M. O., J. Girardeau, and G. Boillot. "Kinematics of peridotite emplacement during North Atlantic continental rifting, Galicia, northwestern Spain." Tectonophysics 184, no. 3-4 (December 1990): 321–43. http://dx.doi.org/10.1016/0040-1951(90)90446-f.

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Paguican, E. M. R., B. van Wyk de Vries, and A. M. F. Lagmay. "Volcano-tectonic controls and emplacement kinematics of the Iriga debris avalanches (Philippines)." Bulletin of Volcanology 74, no. 9 (October 4, 2012): 2067–81. http://dx.doi.org/10.1007/s00445-012-0652-7.

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Pubellier, Manuel, Christophe Monnier, René Maury, and R. Tamayo. "Plate kinematics, origin and tectonic emplacement of supra-subduction ophiolites in SE Asia." Tectonophysics 392, no. 1-4 (November 2004): 9–36. http://dx.doi.org/10.1016/j.tecto.2004.04.028.

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Benn, Keith, Francis Odonne, Sharon K. Y. Lee, and Ken Darcovich. "Analogue scale models of pluton emplacement during transpression in brittle and ductile crust." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 1-2 (2000): 111–21. http://dx.doi.org/10.1017/s0084255900006021.

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Analogue experiments were used to investigate pluton emplacement during transpression in a layered crust. Models consisted of (1) a silicone gum-PbO suspension as analogue magma, (2) a silicone gum-Pb suspension as a basal ductile layer, and (3) an overlying sand pack representing brittle crust. The models were transpressed at 3 mm/hr causing the extrusion of the analogue magma from a progressively closing slot, and its emplacement into the ductile layer. The thicknesses of the layers were critical in controlling the shapes of intrusions and the structures that developed in the brittle overburden. Thicker sand packs led to flattened, symmetrical laccolith-shaped intrusions and the nucleation of one oblique thrust in the sand pack above the extremity of the intrusion. Thinner sand packs led to thicker, asymmetrical laccolith-like intrusions with uplift of the overburden on an oblique thrust, and the formation of a shallow graben in the extrados of a bending fold. Reducing the thickness of the basal ductile layer resulted in a larger number of shear zones in the sand pack, and structural geometries approaching those produced in experiments involving only a brittle analogue crust and no ductile layer. Shear zones in the sand pack were localised by intrusions, and also played a key role in displacing analogue brittle crust to make space for intrusions. The results suggest that tectonic forces may play an important role in displacing blocks of crust during pluton emplacement in transpressional belts. They also suggest that pluton shapes, and the geometries and kinematics of emplacement-related shear zones and faults, may depend on the depth of emplacement. In nature, depending on the structural level exposed in the map plane, faults and shear zones that helped make space for emplacement may not appear to be spatially associated with the pluton.

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Fawcett, Tammy C., Russell F. Burmester, Bernard A. Housen, and Alexander Iriondo. "Tectonic implications of magnetic fabrics and remanence in the Cooper Mountain pluton, North Cascade Mountains, Washington." Canadian Journal of Earth Sciences 40, no. 10 (October 1, 2003): 1335–56. http://dx.doi.org/10.1139/e03-055.

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Documenting the timing and kinematics of deformation in orogens is critical to unraveling their history. Anisotropy of magnetic susceptibility defines the orientation of magnetic fabrics in the Eocene Cooper Mountain pluton in the North Cascade Mountains of Washington. The magnetic foliation typically has a steep dip and a northwest strike; the magnetic lineation plunges moderately to shallowly northwest or southeast. The remanent magnetization was measured to determine if the Cooper Mountain pluton has been tilted following emplacement. The remanence has two components. The characteristic remanence typically unblocks at 370 °C in most specimens, but at 580 °C in others. The two components are carried by pyrrhotite and magnetite. Mean directions of these components are indistinguishable from each other and from the North American expected Eocene direction. The paleomagnetic results and ~ 47 Ma 40Ar39Ar total fusion ages from biotite suggest that there has been no remagnetization or significant reorientation of the pluton since emplacement. Therefore, the in situ magnetic fabrics from the pluton can be used to understand the kinematics. Discordance of the fabrics with the pluton margin and near concordance with regional structures suggests that they have a tectonic origin. Thus the Cooper Mountain pluton is syntectonic rather than posttectonic. The magmatic fabric is slightly oblique to the length of the Cascade orogen, which can be explained if it formed as a consequence of regional dextral shear during transpression.

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Cheng, Nannan, Quanlin Hou, Mengyan Shi, Miao He, Qing Liu, Fangchao Yan, and Hongwei Liu. "New Insight into the Genetic Mechanism of Shear Zone Type Gold Deposits from Muping-Rushan Metallogenic Belt (Jiaodong Peninsula of Eastern China)." Minerals 9, no. 12 (December 12, 2019): 775. http://dx.doi.org/10.3390/min9120775.

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Most gold deposits are genetically controlled by shear zones, which are called shear zone type gold deposits (SZTGD). A better understanding of kinematics of shear zones and its constraint on the ore-forming process is critical to reveal the genetic mechanism of the SZTGD and favorable to mineral exploration. By conducting detailed structural analysis including field and microscopic observations and electron backscatter diffraction (EBSD) and fractal dimension analysis in the Muping-Rushan shear zone (MR) as well as several gold deposits, the kinematic characteristics of the MR are well recognized and the metallogenic process of the SZTGD are discussed. The main conclusions are as follows: (1) petrology, geometry, kinematics, macro- and micro-structures imply that the MR has experienced a progressive shearing history exhumed via middle crust to subsurface level under the NW-SE extensional regime from late Jurassic to early Cretaceous; (2) in the MR, gold may precipitate both in the brittle fractures at middle crust level and brittle deformation part at shallow crust level during the stress-chemical process and (3) comparison of gold deposits between the MR and other areas show that the SZTGD has a uniform metallogenic mechanism, which is from (multi-stage) pluton emplacement, hydrothermal fluid action, shearing action, brittle fracturing, sudden reduction of fluid pressure, flash vaporization to (gold) mineralization.

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Rassios, Anne Ewing, Constantina Ghikas, Yildirim Dilek, and Dimitrios Kostopoulos. "“Rootless” Ophiolites above the Exhuming Pelagonian Core Complex, Northern Greece." Bulletin of the Geological Society of Greece 54, no. 1 (October 2, 2019): 60. http://dx.doi.org/10.12681/bgsg.19353.

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The Mesohellenic ophiolites (MHO) in the Western Hellenides are part of an oceanic slab emplaced onto Pelagonian (Pangaean) continental rocks in the mid-Jurassic with a documented NE ophiolite emplacement. Ophiolitic outliers to the east of the MHO are oceanic lithospheric fragments, not complete ophiolite bodies, preserved above exhumed Pelagonia continental rocks. As these fragments lack connection to original root zone provenance, we refer to these as the “rootless” ophiolites.Pelagonian exhumation, possibly triggered by transcurent shear along its continental margin with the Pindos basin, began by the Late Jurassic and continued into the mid-Cretaceous. Exhumation affected the emplaced oceanic slab in the following ways: i) The metamorphic facies of the basal mélange separating the ophiolite from the Pelagonian basement grades from phyllitic to schist and amphibolite-schist over the exhumed Pelagonia. ii) Ophiolitic remnants are metasomatized where in contact with the exhumed Pelagonian rocks. iii) Remnant ophiolitic fragments are rotated and largely disassociated from their original relative pseudostratigraphic positions in their parent slab. iv) No amphibolite emplacement soles are preserved beneath ophiolitic remnants found directly above Pelagonia.East of Vourinos, remnants of the slab were tectonically entrapped between the exhuming Pelagonian core and its sedimentary overburden, and demonstrate extensional, largely gravitational displacements as well as rotation from original emplacement vectors. Primary constrictive slab emplacement features are obscured, but a general westerly sense of kinematics via listric and extensional faults have been imprinted. In the exhumation model, this "SW topping" direction cannot be interpreted as indicative of an eastern origin of the Pindos Basin ophiolites from the Vardar Zone, but rather as a local response to the uplift of Pelagonia and active deformation of the sedimentary overburden.

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Bouchez, Jean Luc, and Herve Diot. "Nested granites in question: Contrasted emplacement kinematics of independent magmas in the Zaër pluton, Morocco." Geology 18, no. 10 (1990): 966. http://dx.doi.org/10.1130/0091-7613(1990)018<0966:ngiqce>2.3.co;2.

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ARAUJO, M. "Pegmatite Emplacement in the Serido Belt, Northeastern Brazil: Late Stage Kinematics of the Brasiliano Orogen." Gondwana Research 4, no. 1 (January 2001): 75–85. http://dx.doi.org/10.1016/s1342-937x(05)70656-0.

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Schmid, S. M., A. Zingg, and M. Handy. "The kinematics of movements along the Insubric Line and the emplacement of the Ivrea Zone." Tectonophysics 135, no. 1-3 (April 1987): 47–66. http://dx.doi.org/10.1016/0040-1951(87)90151-x.

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Eppler, Dean B., Jonathan Fink, and Raymond Fletcher. "Rheologic properties and kinematics of emplacement of the chaos jumbles rockfall avalanche, Lassen Volcanic National Park, California." Journal of Geophysical Research 92, B5 (1987): 3623. http://dx.doi.org/10.1029/jb092ib05p03623.

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Patel, R. C., Paramjeet Singh, and Nand Lal. "Thrusting and back-thrusting as post-emplacement kinematics of the Almora klippe: Insights from Low-temperature thermochronology." Tectonophysics 653 (June 2015): 41–51. http://dx.doi.org/10.1016/j.tecto.2015.03.025.

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Sekkat, Hiba, Smail Tigani, Rachid Saadane, and Abdellah Chehri. "Vision-Based Robotic Arm Control Algorithm Using Deep Reinforcement Learning for Autonomous Objects Grasping." Applied Sciences 11, no. 17 (August 27, 2021): 7917. http://dx.doi.org/10.3390/app11177917.

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While working side-by-side, humans and robots complete each other nowadays, and we may say that they work hand in hand. This study aims to evolve the grasping task by reaching the intended object based on deep reinforcement learning. Thereby, in this paper, we propose a deep deterministic policy gradient approach that can be applied to a numerous-degrees-of-freedom robotic arm towards autonomous objects grasping according to their classification and a given task. In this study, this approach is realized by a five-degrees-of-freedom robotic arm that reaches the targeted object using the inverse kinematics method. You Only Look Once v5 is employed for object detection, and backward projection is used to detect the three-dimensional position of the target. After computing the angles of the joints at the detected position by inverse kinematics, the robot’s arm is moved towards the target object’s emplacement thanks to the algorithm. Our approach provides a neural inverse kinematics solution that increases overall performance, and its simulation results reveal its advantages compared to the traditional one. The robot’s end grip joint can reach the targeted location by calculating the angle of every joint with an acceptable range of error. However, the accuracy of the angle and the posture are satisfied. Experiments reveal the performance of our proposal compared to the state-of-the-art approaches in vision-based grasp tasks. This is a new approach to grasp an object by referring to inverse kinematics. This method is not only easier than the standard one but is also more meaningful for multi-degrees of freedom robots.

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Bouchez, Jean Luc, Gérard Gleizes, Toufik Djouadi, and Pierre Rochette. "Microstructure and magnetic susceptibility applied to emplacement kinematics of granites: the example of the foix pluton (French pyrenees)." Tectonophysics 184, no. 2 (November 1990): 157–71. http://dx.doi.org/10.1016/0040-1951(90)90051-9.

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Wilkinson, Lori, Alexander R. Cruden, and Thomas E. Krogh. "Timing and kinematics of post-Timiskaming deformation within the Larder Lake - Cadillac deformation zone, southwest Abitibi greenstone belt, Ontario, Canada." Canadian Journal of Earth Sciences 36, no. 4 (April 7, 1999): 627–47. http://dx.doi.org/10.1139/e99-015.

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The Larder Lake - Cadillac deformation zone is one of several anastomosing zones of high strain within the Abitibi greenstone belt. In the Kirkland Lake area, Ontario, the Larder Lake - Cadillac deformation zone is characterized by extensive carbonate and chlorite alteration, strong south-dipping foliations, and steep lineations. These features formed during two ductile deformation increments, D2 and D3, that occurred after deposition of Timiskaming assemblage sediments. D2 strain accumulation and greenschist facies metamorphism and alteration were localized within the deformation zone, facilitated by channelling of hydrothermal fluids within a preexisting structure, possibly formed during early D1 terrane accretion. During D2 north-south shortening, east-west-trending sectors of the deformation zone accumulated bulk coaxial strains, while southeast- and northeast-trending sectors experienced, respectively, dextral and sinistral transpressive deformations. Preservation of Timiskaming assemblage sediments in the footwall of the deformation zone indicates a component of south-over-north (reverse) displacement that is not recorded by D2 fabrics. Northwest-southeast D3 compression resulted in the formation of a regional, northeast-striking cleavage formed under regional greenschist facies conditions, and local dextral reactivation of suitably oriented sections of the Larder Lake - Cadillac deformation zone. The Murdoch Creek and Lebel stocks abut the Larder Lake - Cadillac deformation zone. Their internal structure and emplacement are interpreted to be a consequence of D2 north-south shortening. Magmatic zircon and titanite in the Murdoch Creek and Lebel stocks yield U-Pb geochronology ages of 2672 ± 2 and 2673 ± 2 Ma, providing a maximum age for D2 deformation. Hydrothermal titantite associated with S3 foliation in the Murdoch Creek stock gives an U-Pb age of 2665 ± 4 Ma, the maximum age of D3 deformation. Pluton emplacement, deformation, and coincident metamorphism occurred over a span of 1 Ma (from 2670 to 2669 Ma) to over 14 Ma (from 2675 to 2661 Ma), during a regime of north-south, followed by northwest-southeast, regional shortening.

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Jacques, Dominique, Philippe Muchez, and Manuel Sintubin. "Late- to post-Variscan tectonics and the kinematic relationship with W–Sn vein-type mineralization: evidence from Late Carboniferous intramontane basins (Porto–Sátão syncline, Variscan Iberian belt)." Journal of the Geological Society 178, no. 5 (March 26, 2021): jgs2020–223. http://dx.doi.org/10.1144/jgs2020-223.

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Many studies have constrained that late-Variscan buckling produced the arcuate geometry of the Ibero-Armorican belt. Nonetheless, debate remains on the associated geodynamic framework. Poorly studied Late Carboniferous intramontane basins offer an excellent framework to decipher the timing and kinematics of the late- to post-Variscan tectonics. Understanding the latter also helps constrain the structural emplacement mode of contemporaneous W–Sn–Nb–Ta–Li mineralization. In Iberia, the Porto–Sátão syncline is an example of such a Late Carboniferous intramontane basin. We present a structural analysis of the syncline, its basement and the associated W–Sn deposits. The regional structure is dictated by the Alcudian angular unconformity, caused by Cadomian tectonics (575–555 Ma) and separating tilted Ediacaran and subhorizontal Lower Paleozoic formations. Superimposed Variscan deformation led to F1–F3 folds with steep and gentle plunges, respectively. The late-orogenic D3 fabric is locally affected by post-orogenic F4 kink folds and an S4 crenulation cleavage. W–Sn-bearing vein systems occur along granite-hosted cone sheets, or exploit cross-fold joints associated with the F3 and F4 fold generations, revealing a close kinematic relationship between granite-related mineralization and the late- to post-Variscan deformation style. This structural history is interpreted as a plate-scale geodynamic change from Late Carboniferous north–south (D3) to Early Permian WNW–ESE (D4) convergence.

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Pedrera, Antonio, Ana Ruiz-Constán, Nemesio Heredia, Jesús Galindo-Zaldívar, Fernando Bohoyo, Carlos Marín-Lechado, Patricia Ruano, and Luis Somoza. "The fracture system and the melt emplacement beneath the Deception Island active volcano, South Shetland Islands, Antarctica." Antarctic Science 24, no. 2 (October 28, 2011): 173–82. http://dx.doi.org/10.1017/s0954102011000794.

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AbstractA new magnetotelluric (MT) survey, along with new topographic parametric sonar (TOPAS) profiles and geological field observations, were carried out on the Deception Island active volcano. 3-D resistivity models reveal an ENE–WSW elongated conductor located at a depth between two and ten kilometres beneath the south-eastern part of the island, which we interpret as a combination of partial melt and hot fluids. The emplacement of the melt in the upper crust occurs along the ENE–WSW oriented, SSE dipping regional normal fault zone, which facilitates melt intrusion at shallower levels with volcanic eruptions and associated seismicity. Most of the onshore and offshore volcanic rocks are deformed by high-angle normal and sub-vertical faults with dominant dip-slip kinematics, distributed in sets roughly parallel and orthogonal to the major ENE–WSW regional tectonic trends. Faults development is related to perturbations of the regional stress field associated with magma chamber overpressure and deflation in a regional setting dominated by NW–SE to NNW–SSE extension.

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Sant’Ovaia, Helena, Philippe Olivier, Narciso Ferreira, Fernando Noronha, and Denis Leblanc. "Magmatic structures and kinematics emplacement of the Variscan granites from Central Portugal (Serra da Estrela and Castro Daire areas)." Journal of Structural Geology 32, no. 10 (October 2010): 1450–65. http://dx.doi.org/10.1016/j.jsg.2010.09.003.

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KOKKALAS, S., and A. AYDIN. "Is there a link between faulting and magmatism in the south-central Aegean Sea?" Geological Magazine 150, no. 2 (August 29, 2012): 193–224. http://dx.doi.org/10.1017/s0016756812000453.

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AbstractA distinct spatial relationship between surface faulting, magmatic intrusions and volcanic activity exists in the Aegean continental crust. In this paper, we provide detailed structural observations from key onshore areas, as well as compilations of lineament maps and earthquake locations with focal plane solutions from offshore areas to support such a relationship. Although pluton emplacement was associated with low-angle extensional detachments, the NNE- to NE-trending strike-slip faults also played an important role in localizing the Middle Miocene plutonism, providing ready pathways to deeper magma batches, and controlling the late-stage emplacement and deformation of granites in the upper crust. Additionally, the linear arrangements of volcanic centres, from the Quaternary volcanoes along the active South Aegean Volcanic Arc, are controlled primarily by NE-trending faults and secondarily by NW-trending faults. These volcanic features are located at several extensional settings, which are associated with the main NE-trending faults, such as (i) in the extensional steps or relay zones between strike-slip and oblique-normal fault segments, (ii) at the overlap zones between oblique-normal faults associated with an extensional strike-slip duplex and (iii) at the tip zone of a NE-trending divergent dextral strike-slip zone. The NE trend of volcano-tectonic features, such as volcanic cone alignments, concentration of eruptive centres, hydrothermal activity and fractures, indicates the significant role of tectonics in controlling fluid and magma pathways in the Aegean upper crust. Furthermore, microseismicity and focal mechanisms of earthquakes in the area confirm the activity and present kinematics of these NE- trending faults.

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Gorinova, Tsvetelina, Neven Georgiev, Zlatka Cherneva, Kalin Naydenov, Valentin Grozdev, and Anna Lazarova. "Kinematics and time of emplacement of the Upper Allochthon of the Rhodope Metamorphic Complex: evidence from the Rila Mountains, Bulgaria." International Journal of Earth Sciences 108, no. 7 (August 2, 2019): 2129–52. http://dx.doi.org/10.1007/s00531-019-01754-2.

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Rolin, Patrick, Didier Marquer, Charles Cartannaz, and Philippe Rossi. "Carboniferous magmatism related to progressive pull-apart opening in the western French Massif Central." Bulletin de la Société Géologique de France 185, no. 3 (March 1, 2014): 171–89. http://dx.doi.org/10.2113/gssgfbull.185.3.171.

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AbstractThe Variscan continental collision induced the development of large crustal melting in the western French Massif Central, accompanied by emplacement and deformation of syn- to post-tectonic granites spatially related to normal and strike slip faulting. Our study focuses on the regional deformation and shear zone patterns in the Millevaches massif, one of the largest magmatic area of the French Massif Central. In this massif, the syn-tectonic intrusions are related i) to the dextral wrenching along the Treignac-Pradines shear zones and the Creuse faults system, and ii) to the coeval extension along the N000°–N020° normal faults on the western edge of the Millevaches massif (Bourganeuf and Argentat faults). The analysis of deformation and kinematics correlated to new datations of granites allow us to propose a pull-apart model to explain the tectono-magmatic evolution of this part of the Variscan belt from 350 Ma to 325 Ma. At that time, these granites intruded a “pull-apart” system bounded by two major N140°–160° dextral strike-slip zones operating in the middle continental crust during a bulk N020° regional shortening.From 325 Ma to 320 Ma, a clockwise rotation of the regional shortening axis was responsible for the late reactivation of the N020° eastern Millevaches tectonic border as a dextral fault system (Felletin-Ambrugeat fault system). This NE-SW shortening displaced the N140°–160° Creuse fault system and induced a reverse motion along the northern border of the Millevaches massif (St-Michel-de-Veisse fault). This Visean tectono-magmatic event induced the late exhumation of the Millevaches massif with respect to surrounding units and favoured the widespread granite emplacement in this part of the Variscan belt.

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Singh, Paramjeet, and R. C. Patel. "Post-emplacement kinematics and exhumation history of the Almora klippe of the Kumaun–Garhwal Himalaya, NW India: revealed by fission track thermochronology." International Journal of Earth Sciences 106, no. 6 (November 19, 2016): 2189–202. http://dx.doi.org/10.1007/s00531-016-1422-0.

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Vanardois, Jonas, Pierre Trap, Philippe Goncalves, Didier Marquer, Josselin Gremmel, Guillaume Siron, and Thierry Baudin. "Kinematics, deformation partitioning and late Variscan magmatism in the Agly massif, Eastern Pyrenees, France." BSGF - Earth Sciences Bulletin 191 (2020): 15. http://dx.doi.org/10.1051/bsgf/2020009.

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In order to constrain the finite deformation pattern of the Variscan basement of the Agly massif, a detailed structural analysis over the whole Agly massif was performed. Our investigation combined geological mapping, reappraisal of published and unpublished data completed with our own structural work. Results are provided in the form of new tectonic maps and series of regional cross-sections through the Agly massif. At variance from previous studies, we identified three deformation fabrics named D1, D2 and D3. The D1 deformation is only relictual and characterized by a broadly northwest-southeast striking and eastward dipping foliation without any clear mineral and stretching lineation direction. D1 might be attributed to thickening of the Variscan crust in a possible orogenic plateau edge position. The D2 deformation is a heterogeneous non-coaxial deformation, affecting the whole massif, that produced a shallowly dipping S2 foliation, and an anastomosed network of C2 shear zones that accommodated vertical thinning and N20 directed extension. D2 is coeval with LP-HT metamorphism and plutonism at ca. 315–295 Ma. D2 corresponds to the extensional collapse of the partially molten orogenic crust in a global dextral strike-slip at the scale of the whole Variscan belt. The D2 fabrics are folded and steepened along a D3 east-west trending corridor, called Tournefort Deformation Zone (TDZ), where the Saint-Arnac and Tournefort intrusives and surrounding rocks share the same NE-SW to E-W subvertical S3 foliation. Along the D3 corridor, the asymmetrical schistosity pattern and kinematic criteria suggest a D3 dextral kinematics. The D3 deformation is a record of E-W striking dextral shearing that facilitated and localized the ascent and emplacement of the diorite and granitic sheet-shaped plutons. D3 outlasted D2 and turned compressional-dominated in response to the closure of the Ibero-Armorican arc in a transpressional regime. The progressive switch from D2 thinning to D3 transpression is attributed to the lessening of gravitational forces at an advanced stage of extensional collapse that became overcome by ongoing compressional tectonic forces at the southern edge of the Variscan orogenic plateau.

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Longridge, Luke, Roger L. Gibson, and Paul A. M. Nex. "Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 61–76. http://dx.doi.org/10.1017/s1755691009016119.

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ABSTRACTPartial melting of metapelitic rocks beneath the mafic–ultramafic Rustenburg Layered Suite of the Bushveld Complex in the vicinity of the periclinal Schwerin Fold resulted in a structurally controlled distribution of granitic leucosomes in the upper metamorphic aureole. In the core of the pericline, subvertical structures facilitated the rise of buoyant leucosome through the aureole towards the contact with the Bushveld Complex, with leucosomes accumulating in en-echelon tension gashes. In a subhorizontal syn-metamorphic shear zone to the southeast of the pericline, leucosomes accumulated in subhorizontal dilational structural sites. The kinematics of this shear zone are consistent with slumping of material off the southeastern limb of the rising Schwerin pericline. The syndeformational timing of leucosome emplacement supports a syn-intrusive, density-driven origin for the Schwerin Fold. Modelling of the cooling of the Rustenburg Layered Suite and heating of the floor rocks using a multiple intrusion model indicates that temperatures above the solidus were maintained for >600,000 years up to 300 m from the contact, in agreement with rheological modelling of floor-rock diapirs that indicate growth rates on the order of 8 mm/year for the Schwerin Fold.

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Bhowmick, Sreyashi, and Tridib Kumar Mondal. "Control of pre-existing fabric in fracture formation, reactivation and vein emplacement under variable fluid pressure conditions: an example from Archean greenstone belt, India." Solid Earth 11, no. 4 (July 8, 2020): 1227–46. http://dx.doi.org/10.5194/se-11-1227-2020.

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Abstract. Most of the upper crustal fluid flows are strongly influenced by the pre-existing fractures/foliations in the rocks under a certain state of tectonic stress and fluid pressure condition. In the present study, we analyzed a wide range of crosscutting fractures that are filled with quartz veins of variable orientations and thicknesses, from the gold-bearing massive metabasalts (supracrustals) of the Chitradurga Schist Belt adjacent to the Chitradurga Shear Zone (CSZ), Western Dharwar Craton, southern India. The study involves the following steps: (1) analyzing the internal magnetic fabric, using anisotropy of magnetic susceptibility (AMS) studies, and determining strength of the host metabasalts, (2) quantifying the fluid pressure condition through lower hemisphere equal area projection of pole to veins by determining the driving pressure ratio (R′), stress ratio (ϕ), and susceptibility to fracturing, and (3) deciphering the paleostress condition using fault-slip analysis. We interpret the NNW–SSE to NW–SE (mean 337/69∘ NE) oriented magnetic fabric in the rocks of the region as having developed during regional D1/D2 deformation on account of NE–SW shortening. However, D3 deformation manifested by NW–SE to E–W shortening led to the sinistral movement along CSZ. As a consequence of this sinistral shearing, fractures with prominent orientations formed riedel shear components, with CSZ as the shear boundary. Subsequently, all the pre-existing fabrics along with the riedel shear components were reactivated and vein emplacement took place through episodic fluid pressure fluctuation from high to low Pf at shallow depth (∼ 2.4 km). However, NNW–SSE orientations were prone to reactivate under both high- and low-Pf conditions, thereby attaining maximum vein thickness along these orientations. The deduced paleostress from fault-slip analysis along with the kinematics of the fractures and veins are in good agreement with previously estimated regional tectonics. Thus, integrating multiple domains of studies helps in the logical interpretation of fluid flow conditions and vein emplacement mechanisms in the study area that has not been ventured before.

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Sánchez, Matías G., Murray M. Allan, Craig J. R. Hart, and James K. Mortensen. "Extracting ore-deposit-controlling structures from aeromagnetic, gravimetric, topographic, and regional geologic data in western Yukon and eastern Alaska." Interpretation 2, no. 4 (November 1, 2014): SJ75—SJ102. http://dx.doi.org/10.1190/int-2014-0104.1.

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Aeromagnetic lineaments interpreted from reduced-to-pole (RTP) magnetic grids were compared with gravity, topography, and field-based geologic maps to infer regional structural controls on hydrothermal mineral occurrences in a poorly exposed portion of the North American Cordillera in western Yukon and eastern Alaska. High-frequency and variable-intensity aeromagnetic lineaments corresponding to discontinuities with an aeromagnetic domain change were interpreted as steep-dipping and either magnetite-destructive or magnetite-additive faults. These structures were interpreted to be predominantly Cretaceous in age and to have formed after the collision of the Intermontane terranes with the ancient Pacific margin of North America. To demonstrate the reliability of the aeromagnetic interpretation, we developed a multidata set stacking methodology that assigns numeric values to individual lineaments depending on whether they can be traced in residuals and first vertical derivative of RTP aeromagnetic grids, isostatic residual gravity grids, digital topography, and regional geologic maps. The sum of all numeric values was used to estimate the likelihood of the aeromagnetic lineament as a true geologic fault. Fault systems were interpreted from zones of lineaments with high spatial density. Using this procedure, 10 major northwest-trending fault systems were recognized. These were oriented subparallel to the regional Cordilleran deformation fabric, the mid-Cretaceous Dawson Range magmatic arc, and well-established crustal-scale dextral strike-slip fault systems in the area. These orogen-parallel fault systems were interpreted to play a structural role in the emplacement of known porphyry Cu-Au and epithermal Au systems of mid-Cretaceous (115–98 Ma) and Late Cretaceous (79–72 Ma) age. The procedure also identified seven northeast-trending, orogen-perpendicular fault-fracture systems that are prominent in eastern Alaska and exhibit sinistral-to-oblique extensional kinematics. These structures were interpreted to govern the emplacement of Late Cretaceous (72–67 Ma) porphyry Mo- and Ag-rich polymetallic vein and carbonate replacement systems in the region.

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Hovakimyan, Samvel, Robert Moritz, Rodrik Tayan, Rafael Melkonyan, and Marianna Harutyunyan. "Cenozoic Strike-Slip Tectonics and Structural Controls of Porphyry Cu-Mo and Epithermal Deposits During Geodynamic Evolution of the Southernmost Lesser Caucasus, Tethyan Metallogenic Belt." Economic Geology 114, no. 7 (November 1, 2019): 1301–37. http://dx.doi.org/10.5382/econgeo.4662.

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Abstract The Zangezur-Ordubad mining district of the southernmost Lesser Caucasus is located in the central segment of the Tethyan metallogenic belt and consists of porphyry Cu-Mo and epithermal Au and base metal systems hosted by the composite Cenozoic Meghri-Ordubad pluton. Ore-hosting structures and magmatic intrusions are predominantly confined to a central N-S–oriented corridor 40 km long and 10 to 12 km wide, located between two regional NNW-oriented right-lateral faults, the Khustup-Giratagh and Salvard-Ordubad faults. The anatomy and kinematics of the main fault network are consistent with dextral strike-slip tectonics controlled by the NNW-oriented Khustup-Giratagh and Salvard-Ordubad faults. Dextral strike-slip tectonics was initiated during the Eocene, concomitantly with final subduction of the Neotethys, and controlled the emplacement of the Agarak, Hanqasar, Aygedzor, and Dastakert porphyry Cu-Mo and Tey-Lichkvaz and Terterasar epithermal Au and base metal deposits. The Eocene structures were repeatedly reactivated during subsequent Neogene evolution in transition to a postsubduction geodynamic setting. Ore-bearing structures at the Oligocene world-class Kadjaran porphyry Cu-Mo deposit were also controlled by dextral strike-slip tectonics, as well as porphyry mineralization and its epithermal overprint hosted by an early Miocene intrusion at Lichk. Eocene to early Miocene dextral strike-slip tectonics took place during NE- to NNE-oriented compression related to Paleogene Eurasia-Arabia convergence and subsequent Neogene postcollision evolution. Paleostress reconstruction indicates major reorganization of tectonic plate kinematics since the early Miocene, resulting in N-S– to NW-oriented compression. Early Miocene epithermal overprint at the Kadjaran porphyry deposit and left-lateral reactivation of faults and mineralized structures are linked to this late Neogene tectonic plate reorganization.

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Romagny, Adrien, Laurent Jolivet, Armel Menant, Eloïse Bessière, Agnès Maillard, Albane Canva, Christian Gorini, and Romain Augier. "Detailed tectonic reconstructions of the Western Mediterranean region for the last 35 Ma, insights on driving mechanisms." BSGF - Earth Sciences Bulletin 191 (2020): 37. http://dx.doi.org/10.1051/bsgf/2020040.

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Slab retreat, slab tearing and interactions of slabs are first-order drivers of the deformation of the overriding lithosphere. An independent description of the tectonic evolution of the back-arc and peripheral regions is a pre-requisite to test the proposed conceptual, analogue and numerical models of these complex dynamics in 3-D. We propose here a new series of detailed kinematics and tectonic reconstructions from 35 Ma to the Present shedding light on the driving mechanisms of back-arc rifting in the Mediterranean where several back-arc basins all started to form in the Oligocene. The step-by-step backward reconstructions lead to an initial situation 35 Ma ago with two subduction zones with opposite direction, below the AlKaPeCa block (i.e. belonging to the Alboran, Kabylies, Peloritani, Calabrian internal zones). Extension directions are quite variable and extension rates in these basins are high compared to the Africa-Eurasia convergence velocity. The highest rates are found in the Western Mediterranean, the Liguro-Provençal, Alboran and Tyrrhenian basins. These reconstructions are based on shortening rates in the peripheral mountain belts, extension rates in the basins, paleomagnetic rotations, pressure-temperature-time paths of metamorphic complexes within the internal zones of orogens, and kinematics of the large bounding plates. Results allow visualizing the interactions between the Alps, Apennines, Pyrenean-Cantabrian belt, Betic Cordillera and Rif, as well as back-arc basins. These back-arc basins formed at the emplacement of mountain belts with superimposed volcanic arcs, thus with thick, hot and weak crusts explaining the formation of metamorphic core complexes and the exhumation of large portions of lower crustal domains during rifting. They emphasize the role of transfer faults zones accommodating differential rates of retreat above slab tears and their relations with magmatism. Several transfer zones are identified, separating four different kinematic domains, the largest one being the Catalan-Balearic-Sicily Transfer Zone. Their integration in the wider Mediterranean realm and a comparison of motion paths calculated in several kinematic frameworks with mantle fabric shows that fast slab retreat was the main driver of back-arc extension in this region and that large-scale convection was a subsidiary driver for the pre-8 Ma period, though it became dominant afterward. Slab retreat and back-arc extension was mostly NW-SE until ∼ 20 Ma and the docking of the AlKaPeCa continental blocks along the northern margin of Africa induced a slab detachment that propagated eastward and westward, thus inducing a change in the direction of extension from NW-SE to E-W. Fast slab retreat between 32 and 8 Ma and induced asthenospheric flow have prevented the transmission of the horizontal compression due to Africa-Eurasia convergence from Africa to Eurasia and favored instead upper-plate extension driven by slab retreat. Once slab retreat had slowed down in the Late Miocene, this N-S compression was felt and recorded again from the High Atlas to the Paris Basin.

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Escuder Viruete, J., F. Contreras, G. Stein, P. Urien, M. Joubert, T. Ullrich, J. Mortensen, and A. Pérez-Estaún. "Transpression and strain partitioning in the Caribbean Island-arc: Fabric development, kinematics and Ar–Ar ages of syntectonic emplacement of the Loma de Cabrera batholith, Dominican Republic." Journal of Structural Geology 28, no. 8 (August 2006): 1496–519. http://dx.doi.org/10.1016/j.jsg.2006.04.003.

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Biswal, T. K., Harish Ahuja, and Himansu Sekhar Sahu. "Emplacement kinematics of nepheline syenites from the Terrane Boundary Shear Zone of the Eastern Ghats Mobile Belt, west of Khariar, NW Orissa: Evidence from meso- and microstructures." Journal of Earth System Science 113, no. 4 (December 2004): 785–93. http://dx.doi.org/10.1007/bf02704037.

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Thiery, Vincent, Patrick Rolin, Didier Marquer, Alain Cocherie, C. Mark Fanning, and Philippe Rossi. "Visean sinistral wrench faulting along the Sillon Houiller in the French Massif Central: Late Variscan tectonic implications." Bulletin de la Société Géologique de France 180, no. 6 (October 1, 2009): 513–28. http://dx.doi.org/10.2113/gssgfbull.180.6.513.

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AbstractThe Sillon Houiller is one of the main crustal discontinuities of the Variscan domain of the French Massif Central. Paradoxically, its kinematics and its tectonic significance are still a matter of debate.Since Grolier and Letourneur [1968]’s works, a Stephanian sinistral offset, inferred from the emplacement of numerous coal basins along the fault, is widely accepted.The earlier history of this accident is still debated and subject to controversies. The finite offset of the Sillon Houiller results from the superposition of 3 distinct events. The first one is a brittle/ductile accident that is probably at the origin of the main left-lateral motion. Dated granitoid intrusions and Visean tuff basins seal this accident. The later Stephanian motion is revealed by brittle faulting related to coal basin opening. Finally, a vertical offset of the fault is suggested by a few strong-dipping striations.The Visean offset of the Sillon Houiller has first order implications for the understanding of the western Europe Variscan orogeny. We suggest that the Sillon Houiller and the Paris Basin Magnetic anomaly belong to a single crustal discontinuity interpreted as the eastern boundary of the Armorican/Massif Central block. The 15° clockwise rotation affecting this crustal block and inferred from the structural study of this domain occurred along this accident. The magnetic and gravimetric anomaly may be the result of Visean mafic intrusions, such as quartz diorites that are exposed in the northern part of the Massif Central close to the southern end of the anomaly.

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Plissart, Gaëlle, Hervé Diot, Christophe Monnier, Marcel Mărunţiu, and Julien Berger. "Relationship between a syntectonic granitic intrusion and a shear zone in the Southern Carpathian-Balkan area (Almăj Mountains, Romania): Implications for late Variscan kinematics and Cherbelezu granitoid emplacement." Journal of Structural Geology 39 (June 2012): 83–102. http://dx.doi.org/10.1016/j.jsg.2012.03.004.

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37

Faria, Cristiana, and Carlos Leal Gomes. "Structure of the Granitic Pegmatite Field of the Northern Coast of Portugal—Inner Pegmatite Structures and Mineralogical Fabrics." Heritage 2, no. 1 (January 24, 2019): 315–30. http://dx.doi.org/10.3390/heritage2010021.

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On the coastline of Northern Portugal, metamorphic formations and pegmatites were the subject of structural analysis with the main goal of understanding Variscan kinematics and related pegmatite intrusion. This study also aims to discriminate, select and characterize relevant aspects of the structure and the paragenesis of pegmatites, well exposed as a result of coastal erosion, justifying its inclusion in the geological heritage of the Northern coast of Portugal. The pegmatite bodies show distinctive internal and external structures that are attributable to different modes of emplacement and subsequent deformation. The pegmatitic implantation in the areas of Moledo and Afife occurs in an intragneissic and perigranitic environment, for the first area, and perigneissic and perigranitic environment, for the second. In Pedras Ruivas predominates the implantation into an exo-gneissic to exo-granitic domain. The Moledo veins show evidence of multiphase open/filling, revealing positions, shapes, attitudes, sizes and internal structures that change as a function of the host lithology and host structure, but mainly due to the dilation and the cycles number of local telescoping. The structural analysis of the pegmatite bodies allows the deduction of a local fulcrum of expansion that hypothetically overlaps a hidden stock of parental granite. In Afife and Pedras Ruivas, some pegmatitic lenses are specialized and mineralized in Li, Cs and Ta, with spodumene and tantalite ± cassiterite. Spodumene occurs as giant crystals, centimetric to pluri-decimetric in length, which mark very clearly the structures of in situ or in flow crystallization inside the pegmatites (primary structures) and also the secondary structures resulting from deformation. The geometric analysis of fabrics helps the individualization of well-defined stages of progressive evolution of the deformation of the pegmatites, allowing its correlation with major D2–D3 episodes of regional Variscan deformation.

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Shaller, Philip J., Macan Doroudian, and Michael W. Hart. "The Eureka Valley Landslide: Evidence of a Dual Failure Mechanism for a Long-Runout Landslide." Lithosphere 2020, no. 1 (December 2, 2020): 1–26. http://dx.doi.org/10.2113/2020/8860819.

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Abstract Long-runout landslides are well-known and notorious geologic hazards in many mountainous parts of the world. Commonly encompassing enormous volumes of debris, these rapid mass movements place populations at risk through both direct impacts and indirect hazards, such as downstream flooding. Despite their evident risks, the mechanics of these large-scale landslides remain both enigmatic and controversial. In this work, we illuminate the inner workings of one exceptionally well-exposed and well-preserved long-runout landslide of late Pleistocene age located in Eureka Valley, east-central California, Death Valley National Park. The landslide originated in the detachment of more than 5 million m3 of Cambrian bedrock from a rugged northwest-facing outcrop in the northern Last Chance Range. Its relatively compact scale, well-preserved morphology, varied lithologic composition, and strategic dissection by erosional processes render it an exceptional laboratory for the study of the long-runout phenomenon in a dry environment. The landslide in Eureka Valley resembles, in miniature, morphologically similar “Blackhawk-like” landslides on Earth, Mars, and minor planet Ceres, including the well-known but much larger Blackhawk landslide of southern California. Like these other landslides, the landslide in Eureka Valley consists of a lobate, distally raised main lobe bounded by raised lateral levees. Like other terrestrial examples, it is principally composed of pervasively fractured, clast-supported breccia. Based on the geologic characteristics of the landslide and its inferred kinematics, a two-part emplacement mechanism is advanced: (1) a clast-breakage mechanism (cataclasis) active in the bedrock canyon areas and (2) sliding on a substrate of saturated sediments encountered and liquefied by the main lobe of the landslide as it exited the main source canyon. Mechanisms previously hypothesized to explain the high-speed runout and morphology of the landslide and its Blackhawk-like analogs are demonstrably inconsistent with the geology, geomorphology, and mineralogy of the subject deposit and its depositional environment.

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Tourigny, Ghislain, and Francis Chartrand. "Kinematic evolution of metre-scale shear zones in foliated low-grade tectonites: an example from the Bousquet gold district, Quebec." Canadian Journal of Earth Sciences 31, no. 8 (August 1, 1994): 1301–8. http://dx.doi.org/10.1139/e94-112.

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Small-scale subvertical shear zones developed parallel to a regional preexisting S2 schistosity exhibit evidence of a complex shearing history recorded by conflicting kinematic indicators in both crosssection and plan view. The concordant schistosity internal to the shear zones contains a steeply plunging stretching lineation. Coexisting kinematic indicators of non-coaxial deformation parallel to this lineation are compatible with reverse dip-slip. This earliest shearing event was characterized by (1) the development of several shear discontinuities along selected preexisting S2 foliation surfaces, (2) subvertical transposition of both bedding and the oldest (S1) flat-lying foliation, and (3) by the emplacement of shear veins along the S2 foliation planes. The youngest shearing event reactivated the foliation-parallel shear discontinuities as dextral shear planes, thereby causing concomitant subhorizontal retransposition, east–west subhorizontal stretching, and emplacement of en echelon extension veins. A single set of shear bands occurring at a clockwise acute angle to the slipping foliation indicates that small-scale shear zones were transpressional during the late dextral shearing.

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COOK, C. A., R. E. HOLDSWORTH, and M. T. STYLES. "The emplacement of peridotites and associated oceanic rocks from the Lizard Complex, southwest England." Geological Magazine 139, no. 1 (January 2002): 27–45. http://dx.doi.org/10.1017/s0016756801005933.

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Upper mantle peridotites and associated oceanic rocks from the Lizard Complex, southwest England, preserve evidence for a multistage geological history. Steeply dipping pre-emplacement fabrics record high-temperature (900–1100°C) shearing and exhumation of the mantle peridotites apparently formed during localized NE–SW rifting in a pull-apart basin setting (c. 400–390 Ma). Associated oceanic rocks (Landewednack amphibolites) preserve a pre-emplacement prograde brown amphibole-bearing metamorphic assemblage and steeply dipping fabric thought to have formed as the newly formed oceanic crust was juxtaposed with newly exhumed hot mantle peridotite during NE–SW rifting. In both the peridotites and Landewednack amphibolites, steep pre-emplacement structures are cross-cut by low-angle mylonitic fabrics thought to have formed during the initial phases of emplacement of mantle over crustal rocks in a partially intra-oceanic setting (c. 390–375 Ma). The fabrics in peridotites and amphibolites exhibit retrograde mineral assemblages (c. 500–800°C), with the amphibolites preserving two superimposed assemblages, green amphibole + titanite and colourless magnesio-hornblende, respectively, that are thought to record progressive down-temperature deformation during thrusting. Emplacement-related structures in both the basal peridotites and amphibolites consistently dip at low to moderate angles NW, with down-dip lineations and kinematic indicators showing consistent top-to-the-NW senses of shear. Syn-emplacement magmatism is recorded by intrusions of foliated Kennack Gneiss. Anastomosing serpentine-filled faults mark many existing low-angle contacts between the peridotites and Landewednack amphibolites and appear to represent the final, lowest-temperature (< 250°C) stages of emplacement (c. 370 Ma). This study shows that ‘dynamothermal aureoles’ in ophiolites may preserve evidence for tectonothermal events that pre-date thrust emplacement.

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Rolin, Patrick, Didier Marquer, Michel Colchen, Charles Cartannaz, Alain Cocherie, Vincent Thiery, Jean-Michel Quenardel, and Philippe Rossi. "Famenno-Carboniferous (370-320 Ma) strike slip tectonics monitored by syn-kinematic plutons in the French Variscan belt (Massif Armoricain and French Massif Central)." Bulletin de la Société Géologique de France 180, no. 3 (May 1, 2009): 231–46. http://dx.doi.org/10.2113/gssgfbull.180.3.231.

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AbstractThe Variscan continental collision has led to the development of large strike-slip shear zones in western Europe. Our study focuses on the regional deformation and shear zone patterns in the Massif Armoricain and the French Massif Central. The synthesis of granite emplacement ages associated to granite deformation fields, allow us to propose a geodynamic model for the tectonic evolution of this part of the Variscan belt between 370 Ma – 320 Ma (Late Devonian – Namurian).After the first steps of the continental subduction-collision, leading to high temperature and anatexis associated with N-S shortening at 380-370 Ma (Frasnian to Famennian), the southern part of the Massif Armoricain and western part of French Massif Central underwent large dextral shearing along N100-N130 trending shear zones up to early Visean time. These large-scale displacements progressively decreased at around 350-340 Ma, during the first emplacements of biotite bearing granites (Moulins-les Aubiers-Gourgé massif and Guéret massif intrusions).During middle Visean times, the shortening axis direction rotated towards a NNE-SSW direction implying changes in the regional deformation field. The occurrence of N070-N100 sinistral and N110-N130 dextral conjugate shear zones within leucogranites are related to that time. Finally, new N150-N160 dextral shear zones appeared in middle to late Visean times: as for examples, the Parthenay and the Pradines shear zones in the SE Massif Armoricain and the Millevaches massif, respectively. These shear zones were conjugated to the sinistral N020 Sillon Houiller in the French Massif Central. They reflect large scale brittle continental indentation in the French Variscan belt during the middle to late Visean.

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Shumaker, Niven, Daniel Haymond, and Joe Martin. "Kinematic linkage between minibasin welds and extreme overpressure in the deepwater Gulf of Mexico." Interpretation 2, no. 1 (February 1, 2014): SB69—SB77. http://dx.doi.org/10.1190/int-2013-0104.1.

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A geopressure interpretation technique known as the seismic velocity method is a common workflow in which shale compaction functions are characterized at offset control wells, matched to interval seismic velocities, and then used to predictively calculate geopressure away from well control. The seismic velocity method is used to interpret the expected geopressure profile at the Deep Blue subsalt exploration well in Green Canyon 723 in the deep water Gulf of Mexico. The Deep Blue prospect is distinct from other prospects in the play fairway in that the prospective section is overlain by a salt withdrawal minibasin, whereas the offsetting fields are positioned either along the flanks of minibasins or under a thick allochthonous salt canopy. Predrill geopressure interpretations using numerous tomographic imaging velocity data sets shows a large degree of consistency with the magnitude of geopressure encountered in offsetting supra salt and subsalt fields. Results from the Deep Blue 1 exploration well indicate the predrill geopressure interpretation from interval seismic velocities failed to anticipate the extreme degree overpressure encountered in the subsalt section of the well due to poor deep velocity resolution and an “unloaded” compaction signature. The magnitude of overpressure in the primary section is attributed to the emplacement of an unconformable halokinetic sequence over the primary subsalt basin. An interpretive paradigm is described in which the Deep Blue pressure cell is created through two halokinetic episodes: (1) rapid progradation of a salt canopy followed by (2) subsequent salt withdrawal and emplacement of an overlying minibasin. The linkage between halokinetic sequences, burial history, and the development of overpressure can be used to predictively characterize subsalt geopressure environments.

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Rolland, Y., G. Mahéo, A. Pêcher, and I. M. Villa. "Syn-kinematic emplacement of the Pangong metamorphic and magmatic complex along the Karakorum Fault (N Ladakh)." Journal of Asian Earth Sciences 34, no. 1 (January 2009): 10–25. http://dx.doi.org/10.1016/j.jseaes.2008.03.009.

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Virgo, Simon, Max Arndt, Zoé Sobisch, and Janos L. Urai. "Development of fault and vein networks in a carbonate sequence near Hayl al-Shaz, Oman Mountains." GeoArabia 18, no. 2 (April 1, 2013): 99–136. http://dx.doi.org/10.2113/geoarabia180299.

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ABSTRACT We present a high-resolution structural study on the dip slope of the southern flank of Jabal Shams in the central Oman Mountains. The objectives of the study were: (1) to test existing satellite-based interpretations of structural elements in the area; (2) prepare an accurate geological map; and (3) collect an extensive structural dataset of fault and bedding planes, fault throws, veins and joints. These data are compared with existing models of tectonic evolution in the Oman Mountains and the subsurface, and used to assess the applicability of these structures as analogs for fault and fracture systems in subsurface carbonate reservoirs in Oman. The complete exposure of clean rock incised by deep wadis allowed detailed mapping of the complex fault, vein and joint system hosted by Member 3 of the Cretaceous Kahmah Group. The member was divided into eight units for mapping purposes, in about 100 m of vertical stratigraphy. The map was almost exclusively based on direct field observations. It includes measurement of fault throw in many locations and the construction of profiles, which are accurate to within a few meters. Ground-truthing of existing satellite-based interpretations of structural elements showed that faults can be mapped with high confidence using remote-sensing data. The faults range into the subseismic scale with throws as little as a few decimeters. However, the existing interpretation of lineaments as cemented fractures was shown to be incorrect: the majority of these are open fractures formed along reactivated veins. The most prominent structure in the study area is a conjugate set of ESE-striking faults with throws resolvable from several centimeters to hundreds of meters. These faults contain bundles of coarse-grained calcite veins, which may be brecciated during reactivation. We interpret these faults to be a conjugate normal- to oblique fault set, which was rotated together with bedding during the folding of the Al Jabal al-Akhdar anticline. There are many generations of calcite veins with minor offset and at high-angle-to-bedding, sometimes in en-echelon sets. Analysis of clear overprinting relationships between veins at high-angle-to-bedding is consistent with the interpretations of Holland et al. (2009a); however we interpret the anticlockwise rotation of vein strike orientation to start before and end after the normal faulting. The normal faults post-date the bedding-parallel shear veins in the study area. Thus these faults formed after the emplacement of the Semail and Hawasina Nappes. They were previously interpreted to be of the same age as the regional normal- to oblique-slip faults in the subsurface of northern Oman and the United Arab Emirates, which evolved during the early deposition of the Campanian Fiqa Formation as proposed by Filbrandt et al. (2006). We interpret them also to be coeval with the Phase I extension of Fournier et al. (2006). The reactivation of these faults and the evolution of new veins was followed by folding of the Al Jabal al-Akhdar anticline and final uplift and jointing by reactivation of pre-existing microveins. Thus the faults in the study area are of comparable kinematics and age as those in the subsurface. However they formed at much greater depth and fluid pressures, so that direct use of these structures as analogs for fault and fracture systems in subsurface reservoirs in Oman should be undertaken with care.

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Dziggel, A., R. A. Armstrong, G. Stevens, and L. Nasdala. "Growth of zircon and titanite during metamorphism in the granitoid-gneiss terrane south of the Barberton greenstone belt, South Africa." Mineralogical Magazine 69, no. 6 (December 2005): 1019–36. http://dx.doi.org/10.1180/0026461056960305.

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AbstractSHRIMP U-Pb zircon and titanite dating have been used to constrain the timing of mid- to lower- crustal metamorphism (∼650—700°C and 8—11 kbar) and syn-kinematic melting in the granitoid gneiss- dominated terrane south of the Barberton greenstone belt, South Africa. This study is concentrated on a clastic metasedimentary unit exposed in one of several greenstone remnants and a late-kinematic trondhjemite intrusive into spatially associated mixed gneisses. Locally, the clastic metasediments show extensive replacement of garnet and plagioclase by epidote and titanite. The titanites yield an upper intercept date of 3229±9 Ma, and provide a minimum age for the peak of metamorphism. Zircons separated from the same unit record a range of concordant and near-concordant 207Pb/206Pb dates between ∼3560 and 3230 Ma, the youngest group yielding a weighted mean date of 3227±7 Ma. This range of dates is interpreted to be due to a combination of metamorphic recrystallization and high- temperature Pb-loss in originally detrital zircons during regional metamorphism. A minimum age for the timing of deformation is given by the emplacement age of 3229±5 Ma for the late-kinematic trondhjemite. Thus, geochronological data support the notion of a major metamorphic episode that coincided with the proposed short-lived terrane accretion event in the centre of the Barberton greenstone belt.

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Roday, Prakash P., P. Diwan, and S. Singh. "A kinematic model of emplacement of quartz reefs and subsequent deformation patterns in the central Indian Bundelkhand batholith." Journal of Earth System Science 104, no. 3 (September 1995): 465–88. http://dx.doi.org/10.1007/bf02843410.

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Tubía, J. M., J. Cuevas, and J. J. Esteban. "Localization of deformation and kinematic shift during the hot emplacement of the Ronda peridotites (Betic Cordilleras, southern Spain)." Journal of Structural Geology 50 (May 2013): 148–60. http://dx.doi.org/10.1016/j.jsg.2012.06.010.

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Collins, Alan S., and Alastair H. F. Robertson. "Kinematic evidence for Late Mesozoic-Miocene emplacement of the Lycian Allochthon over the Western Anatolide Belt, SW Turkey." Geological Journal 38, no. 3-4 (2003): 295–310. http://dx.doi.org/10.1002/gj.957.

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Drury, S. A., and S. M. Berhe. "Accretion tectonics in northern Eritrea revealed by remotely sensed imagery." Geological Magazine 130, no. 2 (March 1993): 177–90. http://dx.doi.org/10.1017/s0016756800009845.

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AbstractNew details from remotely sensed images of the structure and disposition of broad lithological variations in the Pan-African of northern Eritrea are discussed in the context of accretionary tectonics. The recognition of major north-south structural discontinuities allows the area to be divided into three discrete terranes with apparently different histories of deformation and metamorphism, magmagenesis and sedimentation. The central Hagar Terrane is dominated by large ultramafic masses with a volcano-sedimentary layered sequence, and shows the effects of major sinistral transpression and lateral expulsion. It is bounded to the west by a major fault, the Barka suture, and abuts the older Barka Terrane that comprises metasediments with evidence for polyphase ductile deformation and pre-kinematic dyke emplacement. The Hagar Terrane is thrust against the eastern Nacfa Terrane, which is dominated by low-grade calc-alkaline metavolcanics and immature volcanoclastic sediments intruded by syn-kinematic plutons. These units are pre-dated by an earlier high-grade basement and post-dated by high-level unmetamorphosed silicic volcanics and redbed sediments. The complex is suggested to have been assembled by oblique accretion from the southeast after arc volcanism in the Nacfa Terrane and back-arc extension in the Hagar Terrane ended with the cease of subduction.

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Tcheumenak Kouémo, Jules, Théophile Njanko, Maurice Kwékam, Séta Naba, Bertille E. Bella Nké, Angeline F. Yakeu Sandjo, Eric M. Fozing, and Emmanuel Njonfang. "Kinematic evolution of the Fodjomekwet-Fotouni Shear Zone (West-Cameroon): Implications for emplacement of the Fomopéa and Bandja plutons." Journal of African Earth Sciences 99 (November 2014): 261–75. http://dx.doi.org/10.1016/j.jafrearsci.2014.07.018.

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Journal articles on the topic 'Emplacement kinematics'

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