Journal of Geodynamics最新文献

{"title":"Understanding the crustal architecture beneath the Bangui magnetic anomaly and its interactions with central African tectonic megastructures based gravity and magnetic analysis","authors":"Cyrille Donald Njiteu Tchoukeu ,&nbsp;Yvette Poudjom Djomani ,&nbsp;Kevin Mickus ,&nbsp;Sonia Rousse ,&nbsp;Mohamed Sobh ,&nbsp;Charles Basseka ,&nbsp;Jacques Etame","doi":"10.1016/j.jog.2024.102022","DOIUrl":"https://doi.org/10.1016/j.jog.2024.102022","url":null,"abstract":"<div><p>The Bangui magnetic anomaly (BMA) in Central Africa is one of the largest continental magnetic anomalies on Earth in terms of amplitude and lateral size. Determining the sources of the BMA can lead to an increased understanding of the crustal dynamic in the Central African sub-region and the African continent as a whole. Magnetic and gravity analysis-based derivative, two-dimensional forward modelling and a Curie isothermal depth, showed that (a) the bottoms of the magnetic sources were between 15 and 35 km; (b) the BMA is a coalescence of several anomalies that trend E-W and roughly NE-SW. These directions coincide with regional Pan African-aged shear zones along the Central African orogenic belt and to thrust sheets at the northern edge of the Congo Craton. The depth of magnetization does not exceed 35 km with the amplitude of magnetization becoming smaller in the Central African Republic. The potential magnetic susceptibility sources have an average density of 2850 kg/m3 and magnetic susceptibilities between 0.06 and 0.25 SI. The BMA is interpreted to be a combination of middle and lower crustal bodies that are not continuous and consist of magnetic mineral rich granulites and banded iron formations. The gravity and magnetic modelling indicate that the entire crust was involved in the Pan African collisional event similar to what is seen in the Mozambique belt in East Africa. Combined with geological and geochemical studies, the models add evidence that one or two subduction zones were involved in accreting terranes on the northern edge of the Congo Craton. The tectonic accretions caused a crustal remobilization along major shear zones that has locally contributed to a probable circulation of fluids enriched in ferromagnesian minerals during late Neoproterozoic magmatism that created the BMA sources.</p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102022"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140015349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strong earthquakes and tsunami potential in the Hellenic Subduction Zone","authors":"Ioanna Triantafyllou ,&nbsp;Apostolos Agalos ,&nbsp;Achilleas G. Samaras ,&nbsp;Theophanis V. Karambas ,&nbsp;Gerassimos A. Papadopoulos","doi":"10.1016/j.jog.2024.102021","DOIUrl":"https://doi.org/10.1016/j.jog.2024.102021","url":null,"abstract":"<div><p>The tsunamigenic potential of an earthquake depends on its size, source depth and focal mechanism. The Hellenic Subduction Zone (HSZ) has been selected in the paper to study this important issue. The HSZ was ruptured by 11 strong (M_w6.0) earthquakes in the time period 2009–2023. One earthquake ruptured onshore but only three out of ten offshore earthquakes produced tsunamis: 1 July 2009 (M_w6.4), 25 October 2018 (M_w6.8), 5 May 2020 (M_w6.6). For each one of the two more recent earthquakes of 5 May 2020 (tsunamigenic, thrust faulting) and 12 October 2021 (non-tsunamigenic, strike-slip faulting) we developed heterogeneous fault models from the inversion of teleseismic P-waveforms, and homogeneous fault models from published moment-tensor solutions. For each fault model tsunami generation and propagation was numerically simulated based on an advanced phase-resolving wave model with the use of higher-order Boussinesq-type equations. The modelled tsunami mareograms are consistent with tide records of the small tsunami (height ∼30 cm) produced by the 2020 earthquake. For the 2021 earthquake the modelled mareograms showed tsunami-like disturbance with amplitude not exceeding the noise level. The tsunamigenic earthquakes of 2009, 2018 and 2020 shared magnitude M_w≥ 6.4, shallow depth (h&lt;20 km), moderate-to-high dip-angle and thrust faulting or oblique slip with significant thrust component. In the remaining seven non-tsunamigenic earthquakes, including the 2021 one, at least one of these features is missing. The results obtained help to better understand the seismic mechanisms of tsunami generation in the HSZ. Further investigation is needed for the central HSZ segment to the south of Crete Island, which historically has not been ruptured by large (M_w&gt;7.0) tsunamigenic earthquakes. In contrast, the western and eastern HSZ segments ruptured by the large 365 AD and 1303 AD tsunamigenic earthquakes.</p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102021"},"PeriodicalIF":2.3,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139914813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extensional tectonics of the Indian passive continental margin in the Middle and Late Jurassic: Constraints from detrital zircon ages in the eastern Tethyan Himalaya","authors":"Shuchen Jin ,&nbsp;Yabo Tong ,&nbsp;Xinxin Sun ,&nbsp;Zijian Zhang ,&nbsp;Junling Pei ,&nbsp;Lifu Hou ,&nbsp;Zhenyu Yang","doi":"10.1016/j.jog.2024.102019","DOIUrl":"10.1016/j.jog.2024.102019","url":null,"abstract":"<div><p><span><span>Knowledge the initial extension in the Indian continent during the Jurassic is important for understanding the dynamics of its breakup from Eastern Gondwana. The absence of Jurassic magmatic activity in the eastern Tethyan </span>Himalaya<span><span> hinders the understanding of this process. We report a provenance and tectonic setting study on the </span>Middle Jurassic<span> Zhela and Late Jurassic<span> Weimei Formations sandstone in Gyangze, eastern Tethyan Himalaya. Detrital zircons<span> of Jurassic sediments indicate four major age peaks: ∼500 Ma, ∼820 Ma, ∼950 Ma, and ∼2450 Ma, which reflect the affinity between the Tethyan Himalaya and India. The differences between the crystallization age and depositional age of isolated detrital zircons from the Middle Jurassic Zhela and Late Jurassic Weimei Formations, indicate that they were formed in an extensional continental margin and deposited on the passive continental margin of India. Combined with regional geological information, our results show that </span></span></span></span></span>extensional tectonics<span><span> was dominant on the northern margin of the Indian continent during the Jurassic. The source-sink sedimentary system and the topography remained stable at this time. After the extension event in the Middle and Late Jurassic, the Kerguelen mantle plume commenced activity, indicating the transition from the lithospheric thinning process to active rifting. The mantle plume activity in the </span>Early Cretaceous led to large-scale uplift in the southeast part of the Tethyan Himalaya, that ultimately led to the breakup of India from Eastern Gondwana.</span></p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102019"},"PeriodicalIF":2.3,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139647565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Location and polarity of Variscan sutures based on petrological and seismological data from the Bohemian Massif and the implications for the European Variscides","authors":"S.W. Faryad ,&nbsp;S. Mazur ,&nbsp;J. Plomerová","doi":"10.1016/j.jog.2024.102020","DOIUrl":"10.1016/j.jog.2024.102020","url":null,"abstract":"<div><p>The high- to ultrahigh-pressure ((U)HP) metamorphic rocks are present within the European Variscan belt between the Bohemian and Iberian massifs (the Galicia-Moldanubian zone) and they are partly incorporated into the Alpine orogenic system. Due to their involvement in various allochthonous units, the affiliation of the (U)HP rocks to the suture zones that were the sites of their initial exhumation, is not always clear. The Bohemian Massif preserves the best evidence of Variscan sutures with clear relationships to the exposed (U)HP rocks. They are the Moldanubian and the Saxo-Thuringian sutures bounding the Teplá-Barrandian block from the SSE and NNE, respectively. The distribution of (U)HP rocks coincides with the boundaries of mantle lithosphere domains, delimited from large-scale seismic anisotropy, and reveals the NW-ward inclination of the Moldanubian mantle lithosphere domain beneath the Teplá-Barrandian block and thus a subduction polarity to the NW. The eastern margin of the Teplá-Barrandian block contains a magmatic arc, which is in direct contact with the Moldanubian orogenic wedge, and both are penetrated by lamprophyre dykes (∼340 Ma), which dates the cessation of the collision-related shortening and crustal consolidation. The overall crustal geometry of the Saxo-Thuringian suture implies the SE-ward polarity of subduction during its formation. However, based on seismic tomography and anisotropy model, the suture at mantle depths appears as a sub-vertical boundary between the Saxo-Thuringian and the Teplá-Barrandian lithosphere domains. The Saxo-Thuringian zone bears evidence of blueschist facies metamorphism in the (para)autochthonous units, which are strongly retrogressed. Compared to the Moldanubian zone, (U)HP rocks are less common in the Saxo-Thuringian zone and occur as nappes and klippes, some of which are exposed near the Moldanubian suture. The similarities of the Saxo-Thuringian (U)HP rocks to those in the Moldanubian zone and their allochthonous positions favour formation of some of the (U)HP rocks along the Moldanubian suture and their subsequent emplacement into the Saxothuringian zone. The Moldanubian suture appears to control the distribution of most of the (U)HP rocks exposed along the European Variscan Belt. They all show similarities regarding lithology, mainly fragments of mantle rocks included in felsic materials, and their granulite-amphibolite facies thermal overprint.</p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102020"},"PeriodicalIF":2.3,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139561532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SItomo – A toolbox for splitting intensity tomography and application in the Eastern Alps","authors":"Frederik Link,&nbsp;Maureen D. Long","doi":"10.1016/j.jog.2024.102018","DOIUrl":"10.1016/j.jog.2024.102018","url":null,"abstract":"<div><p>The tomographic inversion of shear wave splitting data for upper mantle anisotropy has been a longstanding challenge. This is due to the ray-based approximation of classical approaches and the near-vertical incidence of the core-mantle converted phases such as SKS that are often used. Recent developments include the calculation of finite-frequency sensitivity kernels for SKS splitting intensity observations, which allows us to accurately take into account the sensitivity to anisotropic structure with depth. A requirement of this tomographic technique is a dense station spacing, which results in overlapping sensitivity kernels at depth and allows for the localization of anisotropic structure. This is satisfied by a growing number of temporary seismic deployments, which motivates the desire to image anisotropic complexities with depth. Here, we introduce and make available a toolbox for the MATLAB environment that facilitates the application of finite-frequency splitting intensity tomography to dense seismic arrays. Our implementation includes several key features, including: 1) A forward calculation of splitting intensities and sensitivity kernels for a complex anisotropic model space. 2) Consideration of the dominant period of the wave, allowing for multiple-frequency analysis, as well as the incoming wave’s non-vertical incidence. 3) The inversion can be based on a classical gradient descent, on a form of the conjugate gradient method known as the BFGS algorithm, or on a gradient-informed stochastic reversible jump algorithm, allowing for a data-driven parametrization of the model space. 4) Importing splitting intensity measurements from waveforms processed in SplitRacer allows for fast pre-processing of large data sets due to its fully automatic design. To illustrate our method, we present both synthetic tests and an application to real data. We apply our inversion procedure to data from the Swath-D network, which densely covers the transition of the Central to the Eastern Alps. Previous studies showed evidence for an abrupt lateral change of layered seismic anisotropy that had been attributed to an opening for channeled asthenospheric flow. Using an SKS splitting intensity tomography approach, we can confirm previous inferences while providing additional constraints on the distribution of anisotropy laterally and with depth.</p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102018"},"PeriodicalIF":2.3,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139499920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Learning verbs in English and Korean: The roles of word order and argument drop.","authors":"Huanhuan Shi, Angela Xiaoxue He, Hyun-Joo Song, Kyong-Sun Jin, Sudha Arunachalam","doi":"10.1080/15475441.2023.2165926","DOIUrl":"10.1080/15475441.2023.2165926","url":null,"abstract":"<p><p>To learn new words, particularly verbs, child learners have been shown to benefit from the linguistic contexts in which the words appear. However, cross-linguistic differences affect how this process unfolds. One previous study found that children's abilities to learn a new verb differed across Korean and English as a function of the sentence in which the verb occurred (Arunachalam et al., 2013). The authors hypothesized that the properties of word order and argument drop, which vary systematically in these two languages, were driving the differences. In the current study, we pursued this finding to ask if the difference persists later in development, or if children acquiring different languages come to appear more similar as their linguistic knowledge and learning capacities increase. Preschool-aged monolingual English learners (N = 80) and monolingual Korean learners (N = 64) were presented with novel verbs in contexts that varied in word order and argument drop and accompanying visual stimuli. We assessed their learning by measuring accuracy in a forced-choice pointing task, and we measured eye gaze during the learning phase as an indicator of the processes by which they mapped the novel verbs to meaning. Unlike previous studies which identified differences between English and Korean learning 2-year-olds in a similar task, our results revealed similarities between the two language groups with these older preschoolers. We interpret our results as evidence that over the course of early childhood, children become adept at learning from a larger variety of contexts, such that differences between learners of different languages are attenuated.</p>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"51 1","pages":"19-39"},"PeriodicalIF":2.1,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11029125/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76639931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal stress pattern at Mt. Etna volcano","authors":"Salvatore Scudero","doi":"10.1016/j.jog.2023.102017","DOIUrl":"10.1016/j.jog.2023.102017","url":null,"abstract":"<div><p>Stress fields may exhibit variegated patterns, especially in volcanic areas where several processes superimpose their effects in space and time. The comprehension of such patterns may not be straightforward to investigate. This work investigates the pattern of the crustal stress<span> in the area of Mt. Etna Volcano (Sicily, Italy). This has been possible through a collection of more than 800 stress indicators derived from seismological and volcanological/geological information. In particular, the type of collected data allows to consider, for the first time in this area, two different temporal steps in the evolution of Etna volcano: the present-day and the previous volcanic phase at 15 ka. Results indicate a transition between a background shallow NW-SE tensional regime and a deep SW-NE compressional one that occurs between 6 and 16 km depth and which well fits with the present-day geodynamic framework of the area. The occurrence of small-scale lateral variations is interpreted as the second-order effect of the structures of the active front buried beneath the volcano, to the volcano loading, and to the feeding system. The temporal variations in the area surrounding the volcano suggest a major rearrangement of the background stress field evidenced by the swap between minimum and maximum horizontal stress directions. Conversely, during the same period, the stress pattern in the exact correspondence of the volcanic edifice showed to be stable and with a radial arrangement. Such coherence would support the literature which suggests a long-term inflation process started at least 15 kyr ago.</span></p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102017"},"PeriodicalIF":2.3,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139068816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation mechanism of carbonaceous materials in fault gouge of Wenchuan earthquake","authors":"Deyang Shi ,&nbsp;Yaowei Liu ,&nbsp;Jin Shi","doi":"10.1016/j.jog.2023.102016","DOIUrl":"10.1016/j.jog.2023.102016","url":null,"abstract":"<div><p>Carbonaceous materials<span> are widely present in the seismic fault zone. They play a crucial role in lubricating the fault slipping. To date, the formation mechanism of carbonaceous materials is still unclear. In this work, we have conducted a carbon dioxide hydrogenation reaction experiment in a homemade high temperature reactor for the purpose to insight the formation mechanism of carbonaceous materials, with fault gouge used as the catalyst. During the reaction process, carbonaceous materials are formed on the fault gouge, suggesting that the carbonaceous materials in the fault zone are possibly generated from carbon dioxide hydrogenation reaction. These results are important for understanding fault behavior and earthquake physics.</span></p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102016"},"PeriodicalIF":2.3,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139015050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variations of the effective elastic thickness evidence for a wide diffusive boundary between the North American and Eurasian plates in Siberia","authors":"M.K. Kaban ,&nbsp;B. Chen ,&nbsp;R.V. Sidorov ,&nbsp;A.G. Petrunin","doi":"10.1016/j.jog.2023.102015","DOIUrl":"10.1016/j.jog.2023.102015","url":null,"abstract":"<div><p>Northeastern Eurasia<span> is one of the least explored regions in the world. Very little geophysical data is available for this inaccessible area. Even the exact location of the plate boundary<span><span> between Eurasia and North America remains a subject of ongoing debate. The effective elastic thickness (EET) of the lithosphere is a proxy for lithospheric strength and can provide insight into the thermal regime<span> and tectonic processes. We have computed a high-resolution map of the EET for northeastern Eurasia using the fan wavelet coherence technique applied to the Bouguer gravity anomalies<span> and topography/bathymetry data, appropriately adjusted to account for the influence of density variations within sediments. The results obtained provide insights into different tectonic regimes within this predominantly understudied region. In particular, we identify the boundary between the Eurasian and North American plates in </span></span></span>Siberia as a rheologically weak diffusive zone extending from the Verkhoyansk and Sette-Daban Ranges to the eastern boundary of the Chersky Range. Unlike the Sette-Daban and Verkhoyansk Ranges, which were formed by plate collision and have an EET of 30–50 km, other mountainous regions have much lower EET values, usually less than 15 km. These areas have recently experienced tectonic activity that has weakened the lithosphere.</span></span></p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102015"},"PeriodicalIF":2.3,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138987235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropic structure in the mantle wedge beneath southeastern Mexico from shear-wave splitting tomography","authors":"Samuel Celis ,&nbsp;Raúl W. Valenzuela ,&nbsp;Marco Calò ,&nbsp;Xyoli Pérez-Campos ,&nbsp;Gerardo León Soto","doi":"10.1016/j.jog.2023.102007","DOIUrl":"10.1016/j.jog.2023.102007","url":null,"abstract":"<div><p><span><span>Cocos intraslab earthquakes were used to make a 3-D tomographic inversion to define a crystallographic orientation model for the mantle wedge beneath southeastern Mexico. This model provided insights regarding the pattern of the mantle </span>wedge flow<span><span> and its relationship to the geometry of the subducting slab. The mantle wedge was parametrized as a 3-D block model of crystallographic orientations assuming the elastic constants of olivine and </span>orthopyroxene<span> with orthorhombic symmetry (hexagonal symmetry was also tested). A linearized, damped, and iterative least-squares approach was used to account for the nonlinear behavior of the shear-wave splitting, numerically recalculating partial derivatives after each iteration. The best-fitting model is consistent with two main flow regimes: (1) 2-D corner flow in a mantle wedge core made up of A-type olivine fabric northwest of the Tehuantepec Ridge extension, and (2) 3-D trench-parallel mantle flow in a mantle wedge core made up of A-, C-, or E-type olivine fabric southeast of this geological feature. Around the Tehuantepec Ridge extension, a partially serpentinized mantle wedge tip is inferred since olivine </span></span></span><em>a-</em>axis orientations are trench-parallel regardless of whether a 2-D corner flow or a 3-D trench-parallel flow prevails. Right above the Tehuantepec Ridge extension (beyond the 100 km isodepth contour of the subducting slab), a change of well-resolved olivine <em>a-</em>axis orientations from trench-normal to trench-parallel while going from northwest to southeast is observed. It signals an abrupt change in the mantle flow pattern possibly through a vertical tear in the Cocos slab. 3-D toroidal flow could be driving subslab mantle material into the mantle wedge around the deepest slab segment. Lastly, approximately trench-normal olivine <em>a-</em>axis orientations are observed in the mantle wedge tip near the Mexico and Guatemala border region, and they could be explained by assuming the presence of B-type olivine fabric.</p></div>","PeriodicalId":54823,"journal":{"name":"Journal of Geodynamics","volume":"159 ","pages":"Article 102007"},"PeriodicalIF":2.3,"publicationDate":"2023-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}