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Tectonophysics
Elsevier
Tectonophysics

Elsevier

0040-1951

Tectonophysics/Journal TectonophysicsSCIISTPAHCIEI
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    Shear zones in the southern Eyre Peninsula, South Australia: Quartz c-axis fabrics in granulite facies mylonitic orthogneisses and relationship to mafic dykes

    Wilson, Christopher J. L.Hunter, Nicholas J. R.
    20页
    查看更多>>摘要：The south eastern portion of the Eyre Peninsula, South Australia, is dominated by a suite of granites and orthogneisses deformed in steep-dipping shear zones during the Kimban Orogeny (1730-1690 Ma). The largest is the transpressional Kalinjala Shear Zone with shortening strains of >= 90% and shear strains of gamma = >= 20, with other near-parallel secondary shear zones displaying similar kinematics. These ductile shear zones are dominated by mylonitic orthogneisses, with shearing commonly nucleating on, or adjacent to, precursor mafic dykes. The mafic dykes are highly sheared, folded and boudinaged with a newly formed matrix assemblage (orthopyroxene + clinopyroxene + garnet + magnetite + quartz + K-feldspar) that indicates the peak P/T metamorphic conditions of 0.7-1.0 GPa and 750-850 degrees C. Partial melting, developed as leucosomes, is associated with this metamorphism. Microstructural relationships between quartz crystallographic preferred orientation (CPO) and shape preferred orientations (SPO) analyses of these polymineralic rocks are best interpreted in terms of a granulite facies isothermal temperature regime of similar to 750 degrees C. The quartz c-axis fabrics, obtained using an optical fabric analyser, reveal a range of CPOs from weak girdles normal to the shear plane, to maxima parallel to the Y-strain axis. There is an overall symmetric orthorhombic pattern, with c-axis fabrics oriented with respect to the XY plane of flattening. There is a minor component of non-coaxial deformation in some shear zones. These fabrics indicate the increased activation of predominantly the prism-< a > slip system in quartz within the shear zones, which is characteristic for these high-temperature and high-strain deformation conditions.
      原文链接:
    • NSTL
    • Elsevier

    Middle Pleistocene fluid infiltration with 10-15 ka recurrence within the seismic cycle of the active Monte Morrone Fault System (central Apennines, Italy)

    Vignaroli, GianlucaRossetti, FedericoPetracchini, LorenzoArgante, Valentina...
    18页
    查看更多>>摘要：This study integrates field, geochronological and geochemical data to constrain fluid circulation in the damage and core zone of the seismogenic Monte Morrone Fault System (MMFS), central Apennines (Italy). Faulting along the MMFS evolved from a diffuse deformation at the damage zone towards progressive localisation of a narrower fault core and, finally, to (re)activation of discrete slip surfaces at shallower crustal conditions. Multiple generations of carbonate mineralisations, including veins and slickfibers, occur along the main fault surfaces. Carbonate mineralisations are locally fractured and incorporated in the surrounding cataclasites, documenting repetitive structurally-controlled fluid infiltration during transient episodes of permeability creation and destruction. Stable carbon and oxygen isotopes of the carbonate mineralisations document a dominant meteoric water source probably mixed with deeper circulating waters having longer residence time. Clumped-isotope yield formation temperatures of vein and slickenfibers in the range between 23 and 40 degrees C. U-Th dating of carbonate mineralisations yield Middle Pleistocene ages (from 268 to 189 ka BP), with a 10-15-ka cyclicity that we link to the coseismic rejuvenation of the structural permeability in the fault zone. We propose that fault-related mineralisations recorded the interactions among tectonic deformation and climate during the Quaternary. Our study is the first documentation of fault-controlled recurrence intervals in fluid infiltration in a seismically active fault of central Apennines.
      原文链接:
    • NSTL
    • Elsevier

    Integrated interpretation: Defining risk corridors by combining 3-D seismic interpretation with induced seismicity hypocenters

    Weir, Ronald M.Eaton, David W.Eyre, Thomas S.Lawton, Donald C....
    13页
    查看更多>>摘要：Development of a resource play is subject to intrinsic risks. These may include the risk of incurring unexpected costs or shutdowns due to anomalous induced seismicity, or risks associated with reservoir stimulation that differs from prior empirical or numerical models. These two risks may be related causally, as completion effectiveness could be adversely affected by loss of fracture fluids into fault systems and/or damage zones, irrespective of the occurrence of induced seismicity. We outline a novel strategy for pre-operational risk assessment that is guided by the interpretation of 3-D seismic data, principles of structural geology and available induced seismicity data from surrounding operations. We integrate regional seismic structural mapping with results of previous experimental studies to develop a corridor-based risk-assessment approach. This approach is illustrated by a case study from the Duvernay play in Alberta, Canada, where subtle basement-rooted strike-slip faults and associated Riedel shears have been activated during previous hydraulic-fracturing completion programs. Unlike previous case studies in this area, we combine analysis of several adjoining 3-D seismic and induced seismicity datasets in order to map regional risk corridors. Given the general infeasibility of exhaustive detection and mapping of all potentially seismogenic faults, our approach relies on established structural principles, analog settings (flower structures) and analysis of fault-slip potential to quantify the probability of activation within a defined corridor that contains interpreted faults.
      原文链接:
    • NSTL
    • Elsevier

    Late Mesozoic-Cenozoic multistage exhumation of the central Bangong-Nujiang Suture, Central Tibet

    Li, ChaoZhao, ZhongbaoLu, HaijianLi, Haibing...
    15页
    查看更多>>摘要：The Cenozoic rise of the Tibetan Plateau has significantly altered global climate change and the biological redistribution of Asia. However, there remain great controversies about its detailed topographical evolution, especially in the hinterland of the Plateau, such as around the Bangong-Nujiang Suture (BNS). Here, we choose the Gaize Basin, which is located in the central BNS, as our target research area. New low-temperature thermochronology data have been used to quantify the cooling history of the intrusive rocks and sedimentary strata from the N-S edges of the Gaize Basin. Our thermochronology results show that 1) zircon (U-Th)/He ages range from 54 +/- 3.7 to 113 +/- 8.4 Ma, 2) apatite fission track ages mostly cluster around similar to 55 Ma, and 3) apatite (IJ - Th)/He ages are between 34 +/- 3.3 and 63 +/- 4.4 Ma. Combined with the results from thermochronology modelling, we suggest that there were three cooling stages recorded around the Gaize Basin: 1) the late Mesozoic (120-100 Ma), which was probably due to the BNS closure and subsequent Qiangtang-Lhasa collision, 2) the Late Cretaceous-early Paleogene (85-55 Ma), which was perhaps related to the far-field effects of the Neo-Tethyan oceanic subduction, and 3) 47-30 Ma, in response to the continuous India-Asian collision. Similar to today, low relief topography has finalized in the central Tibetan Plateau after the last cooling stage and is mainly aided by river incision and erosion on both sides of the BNS.
      原文链接:
    • NSTL
    • Elsevier

    Reaction-induced phase mixing and the formation of ultramylonitic bands

    Tholen, SorenLinckens, JolienHeckel, CatharinaKemperle, Marina...
    22页
    查看更多>>摘要：As for most upper mantle shear zones, mylonitic and ultramylonitic peridotites exposed in the northern Lanzo shear zone display thoroughly mixed, fine-grained (< 25 mu m) bands. The weak crystallographic preferred orientations (CPO) of all their phases are indicative for deformation by diffusion creep. Although interpreted as significantly decreasing the strength of the upper mantle if interconnected, the formation process of fine-grained phase mixtures is still debated. Microstructural analysis of gradually higher strained peridotites of the northern Lanzo shear zone revealed the formation of fine-grained (< 25 mu m) polymineralic tails adjacent to clino- and orthopyroxene porphyroclasts in mylonitic samples. Phase mixtures (av. 65% phase boundaries) are dominated by neoblasts derived from the porphyroclast (Opx/Cpx) and olivine, with minor abundances (< 10 area-%) of plagioclase, spinel +/- amphibole. Neoblast microstructures and mixing of phases directly at the border of the pyroxenes, indicate a reaction of pymxene porphyroclasts to neoblast phase mixtures. Neoblast temperature estimations (similar to 860 degrees C), their systematic change in composition, and plagioclase/spinel abundances suggest that continuous net-transfer reactions, enhanced by the spinel lherzolite to plagioclase lherzolite transition are likely the main driving forces for the formation of ultramylonitic phase mixtures in the Lanzo shear zone. These reactions were potentially enhanced by the presence of fluid as evidenced by pargasitic amphibole crystallization. Comparing these results to other upper mantle shear zones and deformed xenoliths, the importance of reactions (melt-rock, fluid-rock and/or metamorphic) for the formation of polymineralic, ultramylonitic bands is confirmed.
      原文链接:
    • NSTL
    • Elsevier

    Tectonics in a very slowly deforming region in an orogenic belt

    Ozbey, VolkanSengor, Ali Mehmet CelalOzeren, Mehmet Sinan
    13页
    查看更多>>摘要：We use GPS and InSAR data to examine the present-day kinematics of the Tuz Golu Fault Zone with a view to documenting an `infra-plate-like' behaviour within a highly active plate boundary zone. In order to generate the strain rate field of the region, we utilize two different approaches. Both of the approaches reveal that the area has a shear-dominated deformation. Furthermore, we design a simple block model to understand better especially the slip on the Tuz Golu Fault. The results indicate that the fault behaviour can be explained by right-lateral strike-slip motion. This is in contradiction with the previous interpretations of it displaying normal fault behaviour based on geomorphological observations of limited spatial extent. On the other hand, the present-day kinematics of the fault is not an agreement with the thrust features that are observed around it. We think that the propagation of the rupture of the North Anatolian Fault Zone may have put an end to the thrust regime along the Tuz Golii Fault at the end of Pliocene. We think that this study may provide guidelines for understanding the origin and behaviour of slowly deforming 'germanotype' structures within zones of rapidly deforming 'alpino-type' regions.
      原文链接:
    • NSTL
    • Elsevier

    Tectonic uplift along the northeastern margin of the Qinghai-Tibetan Plateau: Constraints from the lithofacies sequence and deposition rate of the Qaidam Basin

    Li, DeyongJiang, XiaodianGong, WeiLi, Chaoyang...
    25页
    查看更多>>摘要：The uplift processes of the Qinghai-Tibetan Plateau is of great significance for understanding the tectonic dynamics and monsoons in East Asia. In this study, the spatiotemporal characteristics of the tectonic uplift along the northeastern margin of the Qinghai-Tibetan Plateau are discussed from a basin-orogen coupling perspective on the basis of detailed analyses of stratigraphy and sedimentology of the Qaidam Basin and comparisons with those of the Xining, Lanzhou, Linxia, Guide-Xunhua, and Jiuquan basins. The asynchronous tectonosedimentary events characterized by alluvial conglomerates at the Early Jurassic-Cretaceous, similar to 53 Ma, similar to 40 Ma, similar to 22 Ma, similar to 15 Ma, and <2.5 Ma have been preserved in wells at different locations. Consistently, the deposition rates indicate three episodes of accelerated deposition at similar to 40 Ma, similar to 20 Ma, and <= 5 Ma in the Cenozoic. Therefore, we believe that the orogenic uplift along the northeastern margin of the Qinghai-Tibetan Plateau can be divided into four stages: Jurassic-Cretaceous, similar to 40-20 Ma, similar to 20-5 Ma, and <5 Ma. During the Jurassic-Cretaceous, tectonic activation and uplift occurred in the ancient Qilian orogenic belt, which formed in the Early Paleozoic. By similar to 40 Ma, the deformation due to the growth of the "proto-Tibetan Plateau" had propagated to the Qiman Tagh Shan-East Kunlun Shan-Ela Shan-West Qinling Mountain chain. Controlled by the tectonic thrusting of the eastern Kunlun Mountains, the Qaidam Basin entered a stage of comprehensive development. At similar to 20 Ma, the deformation front of the Qinghai-Tibetan Plateau reached the Qilian Shan. The unified Paleogene compressional basin in the northern West Qinling Mountains split into secondary basins, such as the Xining, Lanzhou, Linxia, Guide-Xunhua, and Gonghe basins, which evolved independently. At similar to 5 Ma, the entire Qinghai-Tibetan Plateau entered a rapid uplift stage, and the large lacustrine basins in and around the plateau shrank and disappeared.
      原文链接:
    • NSTL
    • Elsevier

    Joint inversion of InSAR, local seismic and teleseismic data sets for the rupture process of the 2020 Mw 6.3 Yutian earthquake and its implications

    Chen, ZhengsongYi, LeiLuo, JunZuo, Kezhen...
    12页
    查看更多>>摘要：On 25 June 2020, a Mw 6.3 earthquake struck Yutian county. The earthquake nucleated on a normal fault in the northwestern Tibetan Plateau. Through jointly inverting local seismic and teleseismic waveform data as well as Interfemmetric Synthetic Aperture Radar (InSAR) Line-of-Sight (LOS) displacement data, the spatiotemporal rupture properties of this earthquake were resolved to investigate and better understand regional crustal extension mechanisms. Inversion results show that this event ruptured along one main asperity concentrated within a depth range of 4.1-13.3 km with a maximum slip of similar to 0.9 m. The rupture front propagated initially around the hypocenter and then unilaterally toward the north. The whole process lasted approximately 8 s and released a total scalar seismic moment of 3.2 x 10(18) Nm (Mw 6.3). The energy-based average stress drop was estimated in the range of 1.9-3.0 MPa. The radiation efficiency was estimated to be 10.0-15.8%, which is relatively low, demonstrating that most of the accumulated strain energy dissipated during rupturing. We suggest that the earthquake was possibly related to the nearby Cenozoic volcano in consideration of the dissipated rupture of the source and the west-dipping causative fault located on the western edge of the volcano. Both the westward motion of the western Kunlun block and the eastward motion of the Kunlun-Qaidam block were responsible for the EW-trending crustal extension in the Yutian district. We supposed that the 2020 normal faulting earthquake was primarily attributed to the different velocities of the Kunlun-Qaidam block moving eastward. Additionally, according to an analysis of coseismic Coulomb stress interactions, the previous 2008 Mw 7.1, 2012 Mw 6.2, and 2014 Mw 6.9 Yutian earthquakes contribute small Coulomb stress disturbance on the hypocenter of the 2020 Mw 6.3 Yutian earthquake which suggest that previous Yutian earthquakes have a limited effect on triggering the 2020 event.
      原文链接:
    • NSTL
    • Elsevier

    Coseismic surface ruptures, slip distribution, and 3D seismogenic fault for the 2021 Mw 7.3 Maduo earthquake, central Tibetan Plateau, and its tectonic implications

    Ren, JunjieXu, XiweiZhang, GuangweiWang, Qixin...
    16页
    查看更多>>摘要：The 2021 Mw 7.3 Maduo earthquake, which hit the high mountain area of the internal Bayan Har Block in the central Tibetan Plateau, generated a similar to 154 km-long, nearly E-W-striking surface rupture zone. Field observations indicate prominent surface breaks characterized by discontinuous shear faults, en echelon tensional fissures, and mole track structures, revealing a dominantly left-lateral strike-slip motion with a maximum sinistral offset of similar to 2.7-2.8 m and general offset of similar to 1.0-1.5 m. The west part of the Maduo surface rupture zone occurred along the pre-existing Jiangcuo fault. Its east portion cut through some WNW-trending tectonics, indicating a previously unknown fault. The epicenter and slip distribution show a bilateral rupture for the Maduo quake. The complex 3D geometry of the Maduo seismogenic fault has controlled the occurrence of aftershocks and the multimodal distribution of coseismic displacements. The abnormally long Maduo surface rupture zone suggests that the rupture area-magnitude relationship might be more applicable than the rupture length-magnitude relationship for the magnitude estimation of a paleo-event. The occurrence of the Maduo earthquake challenges the active block model which used to predict little or no slip partitioning and large earthquakes in the block interior. A reappraisal of seismic hazard along intra-block faults with low strain rates is needed, especially across densely populated regions.
      原文链接:
    • NSTL
    • Elsevier

    Subducted fragments of the Liguro-Piemont ocean, Western Alps: Spatial correlations and offscraping mechanisms during subduction

    Herviou, ClementAgard, PhilippePlunder, AlexisMendes, Kevin...
    31页
    查看更多>>摘要：Fragments of subducted slow-spreading oceanic lithosphere are exposed continuously in the Liguro-Piemont domain of the Western Alps. By combining new and literature petrological data, interpolated maps of maximum temperatures, maximum Si contents of phengite as a proxy for peak pressure and thermodynamic modelling, we provide a detailed framework of the peak metamorphic conditions experienced by the distinct subduction slices. High-resolution mapping confirms the marked eastward increase in metamorphic grade throughout the domain, as well as within some slices. The compilation of lithostratigraphic, structural and radiochronological data and the estimation of sediment/mafic-ultramafic ratio for each slice allow refining the origin of these tectonometamorphic units within the former oceanic domain. The refined structural sketchmap allows to restore the geometries of the Alpine subduction at peak burial conditions. Results point to a trimodal distribution of the units with an increase in metamorphic conditions from the Upper (LPU; 320-400 degrees C- 1.2-1.9 GPa) to the Middle (LPM; 415-475 degrees C- 1.7-2.2 GPa) and to the Lower units (LPL; 500-580 degrees C- 2.2-2.8 GPa). The blueschist-facies LPU and LPM units are dominated by sediments (>90%), whereas the eclogitic LPL units are far richer in mafic-ultramafic rocks (>40%). These characteristics, along with lithostratigraphic differences, reflect major differences in their initial paleogeography and/or in the mechanisms responsible for material offscraping from the downgoing slab. The peak burial depths of the LPU, LPM and LPL units are similar to those inferred for slicing and underplating in both modern and fossil subduction zones. Petrological and lithostratigraphic data suggest that the offscraping of the LPU and LPM units was mostly controlled by lithological contrasts, within pelagic shales or along contacts within the uppermost serpentinized mantle. In contrast, major dehydration reactions (such as lawsonite breakdown in sediments) likely controlled the offscraping of the LPL units at eclogite-facies conditions, possibly through high fluid pressure conditions and rocks embrittlement.
      原文链接:
    • NSTL
    • Elsevier