Sinistral Strike-slip Movement Research Articles

Prolonged exhumation and preservation of the Yuku molybdenum ore field, East Qinling, China: Constraints from medium- to low-temperature thermochronology

Molybdenum (Mo) is an important globally strategic metal and mostly occurs as molybdenite (MoS2) in diverse Mo deposits. The Yuku ore field includes multiple porphyry-skarn Mo deposits and forms a significant world-class Mo cluster in the Qinling molybdenum belt, central China. Previous studies on the ore field were largely related to its genesis, and did not highlight the post-mineralization modifications that are important to formulate prospecting strategies. The exhumation and preservation processes of the ore field through multiple tectonic events also remain poorly understood. Here, we conducted multi-method apatite U-Pb, fission-track and (U-Th)/He and zircon (U-Th)/He medium- to low-temperature thermochronology and related thermal history modelling on granitoids from the ore-hosting Shibaogou and Yuku plutons in the Yuku ore field, and integrated published studies to unravel the post-mineralization exhumation and preservation of Mo deposits. The newly determined apatite U-Pb (158.3–104.9 Ma), zircon (U-Th)/He (158.2–115.0 Ma), apatite fission-track (90.8–63.1 Ma), and apatite (U-Th)/He (67.8–35.3 Ma) ages in this study document multiple cooling pulses during post-magma emplacement. The low-temperature thermochronological ages of 158.2–35.3 Ma also record the post-mineralization cooling and exhumation history. The thermal history modelling indicates an Early Cretaceous (132–125 Ma) rapid cooling pulse, two enhanced (or accelerated) cooling pulses at ca. 125–59 Ma and post-10 Ma, together with a slow cooling or reheating pulse at ca. 59–10 Ma in the Yuku ore field. The Early Cretaceous rapid cooling is related to the coeval collisional tectonics of the East Qinling Orogen. The enhanced cooling at ca. 125–59 Ma is triggered by the post-collisional assembly of the North China and Yangtze Blocks, the subduction of Paleo-Pacific Plate, and the sinistral strike-slip motion of the nearby Tan-Lu Fault Zone. The slow cooling during ca. 59–10 Ma and the post-10 Ma enhanced cooling are correlated with the extensional tectonics derived by the subduction of Pacific Plate and the far-field effects from India-Eurasia collision. The Yuku area underwent lower exhumation in comparison to the nearby Shibaoguo and Huangbeiling areas in the Yuku ore field, which thus is helpful to the preservation of Mo deposits. The un-exhumated areas within 1.0 km at the inner and outer contact zones between the Yuku pluton and its wall rocks are postulated to be favorable sites for Mo prospecting. In addition, the un-exhumated areas surrounding other Late Mesozoic plutons in the Luanchuan region are also suggested to have high potential for Mo exploration.

New data on the Ben Levy anticline, with reverse reactivation on the Coolin Fault giving up-side-down Silurian rocks in Joyces Country, Connemara

Abstract: In Joyces Country in western Ireland, the ∼ E-W striking axial plane of the D7 Ben Levy anticline folded Dalradian and unconformable Silurian rocks. The north side of the fold is mostly coincident with the contemporaneous ESE-WNW striking steeply dipping Coolin Fault close to the Dalradian-basal Silurian contact. This fault was first initiated by sinistral strike-slip motion, probably of Ordovician age, and then secondly used by post-Wenlock down throw on the north side to form the D7 anticline. Later a newly recognised third motion of reverse reactivation on the fault uplifted the north limb of the fold and locally overturned the Silurian succession against irregularities in the SSW dip of the fault. Still later, but pre-374Ma (Devonian), NE-SW faulting exposed different previous levels of the Coolin Fault zone. The superb Dalradian rock exposure provides details not generally apparent on other reactivated faults in Connemara.

A Bayesian Source Model for the 2022 Mw6.6 Luding Earthquake, Sichuan Province, China, Constrained by GPS and InSAR Observations

Until the Mw 6.6 Luding earthquake ruptured the Moxi section of the Xianshuihe fault (XSHF) on 5 September 2022, the region had not experienced an Mw >6 earthquake since instrumental records began. We used Global Positioning System (GPS) and Sentinel-1 interferometric synthetic aperture radar (InSAR) observations to image the coseismic deformation and constrain the location and geometry of the seismogenic fault using a Bayesian method We then present a distributed slip model of the 2022 Mw6.6 Luding earthquake, a left-lateral strike-slip earthquake that occurred on the Moxi section of the Xianshuihe fault in the southwest Sichuan basin, China. Two tracks (T26 and T135) of the InSAR data captured a part of the coseismic surface deformation with the line-of-sight displacements range from ∼−0.16 m to ~0.14 m in the ascending track and from ~−0.12 m to ~0.10 m in the descending track. The inverted best-fitting fault model shows a pure sinistral strike-slip motion on a west-dipping fault plane with a strike of 164.3°. We adopt a variational Bayesian approach and account for the uncertainties in the fault geometry to retrieve the distributed slip model. The inverted result shows that the maximum slip of ~1.82 m occurred at a depth of 5.3 km, with the major slip concentrated within depths ranging from 0.9–11 km. The InSAR-determined moment is 1.3 × 1019 Nm, with a shear modulus of 30 GPa, equivalent to Mw 6.7. The published coseismic slip models of the 2022 Luding earthquake show apparent differences despite the use of similar geodetic or seismic observations. These variations underscore the uncertainty associated with routinely performed source inversions and their interpretations for the underlying fault model.

New Data on the Ben Levy Anticline, With Reverse Reactivation on the Coolin Fault Giving Up-Side-Down Silurian Rocks in Joyces Country, Connemara

In Joyces Country in western Ireland, the ~ E-W striking axial plane of the D7 Ben Levy anticline folded Dalradian and unconformable Silurian rocks. The north side of the fold is mostly coincident with the contemporaneous ESE-WNW striking steeply dipping Coolin Fault close to the Dalradian-basal Silurian contact. This fault was first initiated by sinistral strike-slip motion, probably of Ordovician age, and then secondly used by post-Wenlock down throw on the north side to form the D7 anticline. Later a newly recognised third motion of reverse reactivation on the fault uplifted the north limb of the fold and locally overturned the Silurian succession against irregularities in the SSW dip of the fault. Still later, but pre-374Ma (Devonian), NE-SW faulting exposed different previous levels of the Coolin Fault zone. The superb Dalradian rock exposure provides details not generally apparent on other reactivated faults in Connemara.

Ransiki earthquakes, northeastern Bird’s Head Peninsula, northwestern New Guinea, Indonesia: Deformation partitioning in oblique plate convergence

The plate boundary between the Pacific-Caroline and Australian plates in northwestern New Guinea is associated with a geographic concentration of earthquakes developed in the Ransiki region of the northeastern Bird’s Head Peninsula (West Papua, northwestern New Guinea) at the intersection of the Ransiki and Yapen faults. We examine these earthquakes based on regional geomorphological and lithostratigraphical frameworks, field observations of surface ruptures and liquefaction phenomena, and focal mechanisms of historical earthquakes. The Ransiki earthquakes are a set of 29 earthquakes from the Global Centroid Moment Tensor catalogue in the period 1977–2019 (magnitudes of Mw4.9 to Mw7.5). In the east, focal mechanisms show sinistral movement along the east-west trending Yapen Fault including the Mw6.7 earthquake on 21 April 2012. The largest earthquake was on 10 October 2002 (Mw7.5) and along with other earthquakes mainly in the southwest were associated with dextral movement indicated by focal mechanism solutions on the northwest trending Ransiki Fault south of its intersection with the Yapen Fault. The southern part of the Ransiki Fault therefore indicates local north-northeast compression that is also evident in the newly recognised Wainoei Fault south of Yapen Island. The two largest earthquakes (10 October 2002, 21 April 2012) show ground effects associated with liquefaction, indicated by surface offsets, open fissures, and sand blows, that all occurred in saturated sediments of the Ransiki delta. Earthquakes in the Ransiki region show that west-southwest oblique plate convergence between the Australian and Pacific-Caroline plates is partitioned into east-west sinistral strike-slip motion along the Yapen Fault and north-northeast compression associated with the Ransiki Fault.

Eocene–Miocene tectonic reworking of the southeastern Tibetan Plateau: Geochronological and geochemical records from granitoids along the Ailao Shan–Red River Shear Zone

The convergence of the Indian Plate and Eurasia shaped the Earth’s broadest and highest-elevation collisional system and topographic growth, which is not simply illustrated by ongoing contractional deformation. The Cenozoic magmatism along the Ailao Shan-Red River Shear Zone (ARSZ), linking surface geology with deep lithospheric processes, provides additional information regarding the age and progressive deformation of the India-Asia collision. In this study, we present new zircon U–Pb geochronological, elemental geochemical and zircon Hf isotopic data for the Eocene–Miocene granitoid to resolve the southeastern Tibetan Plateau deformation history. The Jinping granitoids in the southern ARSZ were dated at 37.5–33.6 Ma. They show similar geochemical characteristics (whole-rock major oxides, trace element, Sr–Nd–Pb isotopic and zircon in-situ Hf isotopic data) with respect to coeval potassic granitoids in NW Yunnan, suggesting their origination from partial melting of thickened lower crust with additional contribution from enriched mantle-derived magmas. Leucogranite samples within the ARSZ yielded distinctive zircon U–Pb ages of 28.3 Ma and 18.5 Ma. Geochemical features suggest that they were derived from a heterogeneous crustal source consisting of metasediments and metabasites. Our results, along with those previous studies, suggest that the widespread potassic magmatism in the central and southeastern Tibetan Plateau is related to lithospheric mantle upwelling, which resulted in the partial melting of the thickened lower crust and a short-lived crustal extension during a period of decreased convergence rate. Subsequently, the orogenic-scale sinistral strike-slip movement provided shearing heat for generating leucogranites within the shear zones during the late Oligocene–Miocene. The plateau-wide shift in stress reorganization and tectonic reworking led to the lateral extrusion of the SE Tibetan Plateau and its attainment of modern high elevation.

Synthetic aperture radar interferometry–based coseismic deformation and slip distribution of the 2022 Menyuan MS6.9 earthquake in Qinghai, China

On January 8, 2022, a 6.9 magnitude earthquake occurred in Menyuan County, Qinghai Province, with the epicenter located at the intersection of the Tuolaishan Fault and the Lenglongling Fault, which are part of the Qilian–Haiyuan fault zone. This study investigated the sliding characteristics and seismic mechanism of the earthquake to understand the activity and seismic risk of the fault on the northeastern margin of the Qinghai–Tibet Plateau. This paper analyzed Sentinel-1 synthetic aperture radar images to obtain the coseismic deformation field of the earthquake, which was then used to invert the slip distribution of the seismogenic fault and the coseismic Coulomb stress on the surrounding faults caused by the earthquake. It was found that the earthquake was primarily characterized by sinistral strike-slip movement. Along the satellite line of sight, the south wall of the fault had a maximum deformation of 0.62 m, and the north wall had a maximum deformation of 0.48 m. The coseismic slip distribution results indicated that the maximum slip of the earthquake was 4.51 m, and the moment magnitude was MW6.7. The Coulomb stress analysis showed that the 2016 Menyuan earthquake promoted the occurrence of the 2022 Menyuan earthquake.

Multiscale Structural Analysis of Ediacaran–Cambrian Rocks on the Northeastern Edge of the Saghro Inlier (Eastern Anti-Atlas): Relevance of Post-Cambrian Deformation

The Ediacaran–Cambrian rocks on the northeastern edge of the Saghro inlier experienced polycyclic tectono-thermal events, which are reported here based on a multiscale structural analysis, from field measurements to fluid inclusion planes. Three striking populations were identified, cutting across both the Ediacaran and Cambrian formations. These tectonic structures were generated during four tectonic events. (i) E-W-striking structures that host ore mineralized bodies (sulfide, oxide, quartz, and barite). They display a polyphase tectonic history, caused by a dextral movement in response to a NW–SE-oriented shortening, leading to the formation of quartz gashes and veins. This tectonic event took place during the Neovariscan. These E–W-striking structures were subsequently reactivated during the Mesozoic time under a sinistral strike-slip regime as a result of NE–SW shortening syn-kinematic with barite mineralization. (ii) NE–SW-striking strike-slip structures (dextral or sinistral) crosscut the E–W-striking veins. These faults are related to the NW–SE-oriented shortening that occurred during the Neogene. (iii) The last tectonic episode, related to the N–S shortening, took place during the late Neogene to the Quaternary period. It resulted in NW–SE to N–S-striking structures that were related to dextral and sinistral strike-slip movements, which crosscut the preexisting E–W structures.

The Late Devonian contraction along the Precaspian Basin north margin: Transpressional range building in the intracratonic domain

The evolution of intraplate sedimentary basins located in the vicinity of an active convergent plate boundary is often controlled by the collisional dynamics of the adjacent orogen. The transfer of compression from the orogen to the platform's interior results in the formation of complex structural geometry and kinematics that often reactivate older crustal faults, focus far-field stresses and control the evolution of associated sedimentary basins. One place where this localisation can be optimally understood is the Precaspian Basin, situated at the SE periphery of the East European Craton and bordered to the east by the Uralian orogen. The Precaspian Basin and its northern margin experienced long-term extension and subsidence interrupted by several short-lived shortening episodes. To understand the impact and role of pre-existing basement structures on the geometry and kinematics of the subsequent deformation, we analysed subsurface data from the northern margin of the Precaspian Basin by the means of 3D seismic interpretation correlated with wells and structural modelling. The analysis results provide new insights into the kinematic effects of the Late Devonian contraction event. The superposition of stratigraphic units above and below the angular unconformity suggests an intra-Famennian age of the deformation event. Steeply dipping bi-verging reverse fault zones associated with variable amounts of sinistral strike-slip movement component display an arcuate geometry, trending from WSW-ENE to NW-SE. The distribution of deformation indicates that this complex kinematic pattern was driven by a NE-SW oriented contraction and transpression, where faults show the characteristics of a restraining bend area. This area is interpreted as part of a regional transcurrent fault system developed on the northern periphery of the Precaspian Basin. Furthermore, the study results suggest that intralithospheric stress localisation transmitted by the Paleouralian subduction zone resulted in the reactivation of pre-existing basement structures, propagation of faults, and localized short-term exhumation of the Precaspian Basin north margin. Generated by the collision of Magnitogorsk volcanic arc with East European Craton, far-field stress transfer produced a zone of oblique deformation. These data and interpretation demonstrate that the northern margin of the Precaspian Basin is an excellent natural setting to investigate and better understand mechanisms of far-field strain localisation and reactivation of deformational structures in stable platform areas resulting in the intracratonic mountain building process.

Zircon U–Pb age constraints on the provenance and response to tectonics: Lower Oligocene of the western Qiongdongnan Basin, South China Sea

Provenance changes and tectonic activity during the Early Oligocene in the Qiongdongnan Basin are responses to the evolution of the northwestern South China Sea. However, the provenance of the Lower Oligocene (Yacheng Formation) in the Qiongdongnan Basin is poorly understood owing to a lack of available borehole samples and poorly constrained stratigraphy. Here, combined with published data from wells of different part of the basin, we apply U–Pb dating of detrital zircons on samples nearby the western boundary fault of the basin to analyse the provenance of the Yacheng Formation and its regional tectonic implications. The zircon U–Pb age spectra of the sediments in three different members of Yacheng Formation show different features. A single U–Pb age peak at ca. 235 Ma occurs in the Third Member of the Yacheng Formation, whereas the U–Pb age spectra in the stratigraphically younger Second Yacheng Formation show different zircon U–Pb age spectra features: an age pattern has two major peaks at ca. 248 Ma and 441 Ma and lacks zircons younger than 200 Ma, and another pattern has two major peaks at ca. 95 Ma and 252 Ma. The Early Oligocene provenance evolution of the western Qiongdongnan Basin is reconstructed by comparing the zircon U–Pb age spectra of the sediments in the different samples to potential sources nearby. Abrupt changes in the U–Pb ages throughout the Lower Oligocene in the western Qiongdongnan Basin suggest that sediment supply in the Second Member of Yacheng Formation was dominated by rivers from western Hainan Island and Central Vietnam. By contrast, Hainan Island and local structural highs within the Qiongdongnan Basin were the main sources in the Third and First Members of the Yacheng Formation, respectively. The difference in the U–Pb age spectra between sediments in the Qiongdongnan Basin and the Red River implies that the time at which the Red River system entered the Qiongdongnan Basin was later than the Early Oligocene. Paleorivers sourced from Central Vietnam entered into the western Qiongdongnan Basin and did not reach the central or eastern part of the basin until ca. 31.5–29.9 Ma. An examination of the activity of the Red River Fault showed that the transition of provenance in the study area during the Early Oligocene could be a response to sinistral strike-slip motion along the Red River Fault.

RESEARCH ON THE CHARACTERISTICS OF PRESENT CRUSTAL DEFORMATION IN BEIJING AREA BASED ON GNSS

Abstract. We use the GAMIT/GLOBK software to process more than 100 GNSS sites observation covering the Beijing area from 1999–2021 to obtain the three-dimensional velocity field of present-day crustal movement, and the deformation and strain characteristics of Beijing were calculated and comprehensively analyzed by combining with historical earthquakes. The results show that: 1) The present-day horizontal crustal motion of Beijing is dominated by the SEE direction with a rate of 5-10 mm/a with relative to the stable Eurasian reference frame, and the northern and southern areas show uplift as a whole with a rate of 1–3 mm/a, while the central plain area shows overall subsidence, with a maximum subsidence rate of about 130 mm/a. 2) The horizontal deformation is mainly N-E/N-W extension, accompanied by weak shear activity. 3) The N-W trending faults show sinistral strike slip movement as a whole, with about 1.1–2.0 mm/a, and N-E trending faults show dextral strike slip with a rate of less than 1 mm/a. 4) The historical large earthquakes are distributed within the positive and negative gradient zones of the first shear strain rate, transition zones of the rotation rate, and are mostly distributed at the edges of the high and low value zones of the second shear strain rate, and the edges of the high value zones of the east-west strain rate also have a background of large earthquakes.

The boundary between the North China Craton and the Central Asian Orogenic Belt in NE China: Seismic evidence from receiver function imaging

• 38 broadband seismic stations (profile NCISP-10, 400-km-long) were deployed across the North China Craton (NCC) and the Central Asian Orogenic Belt (CAOB) in Northeast China. • Receiver function CCP images reveal a southward thrust nappe structure at the boundary of the NCC and the CAOB. • Yilan-Yitong fault (YYF) cuts through the Moho and has a vertical offset of 2–3 km indicating that it represents an ultra-crust normal fault. This study imaged the crustal structure and tectonic state of the interacting North China Craton (NCC) and Central Asian Orogenic Belt (CAOB) using receiver function imaging. The seismic profile derived from the NCISP-10 broadband seismic array spanning a northeasterly area of the NCC and a southeasterly area of the CAOB. The profile shows a flat Moho with localized anomalies but generally resting at an average depth of 32 km. The average Vp/Vs ratio was about 1.75 but the crust around the Songliao Basin exhibits a relatively high Vp/Vs ratio and a shallow Moho. An obvious velocity discontinuity appears within the crust beneath the Songliao Basin as evidenced by theoretical model tests which managed effects from multiple waves generated by sedimentary layers in the basin. This discontinuity inclines gently and is interpreted to represent the deep extension of the Chifeng-Kaiyuan fault (CKF), which itself serves as the surface boundary between the NCC and CAOB. The NCC feature appears to the south of this boundary, while a nappe structure formed during subduction-collision and composed primarily of a subduction-accretionary complex lies to the north. The Tanlu Fault consists of two branches in the study area, the Yilan-Yitong fault (YYF) and the Dunhua-Mishan fault (DMF). The YYF cuts through the Moho and has a vertical offset of 2–3 km indicating that it represents a crustal-scale normal fault. The DMF gives no obvious indication of vertical offset in the images but may be mainly characterized by sinistral strike slip movement.

Revisiting the Late Paleozoic–Mesozoic tectonic evolution of epicontinental eastern Central Asian Orogenic Belt on the basis of detrital zircon

The eastern Central Asian Orogenic Belt (CAOB) is a natural laboratory for studying and interpreting the evolution of accretionary collages. The CAOB contains several micro-landmasses whose tectonic evolution during the Late Paleozoic–Mesozoic is a matter of debate. Here, we revisited detrital zircon data in relevant areas and present new detrital zircon U–Pb age data from the Hulin Complex and Wandashan Accretionary Complex (consisting of the Raohe and Yuejinshan complexes) in the eastern CAOB. The youngest zircon peak age of mica-quartz schist from the Hulin Complex constrains the timing of deposition to after ∼153.5 Ma. Sandy slate and fine sandstone from the Wandashan Accretionary Complex have youngest ages of ∼135.7 and ∼254.7 Ma, respectively. These data, together with detrital zircon data in the epicontinental eastern CAOB, suggest that there was a transformation from an extensional to convergent tectonic setting in the eastern CAOB around the Late Permian–Early Triassic. The Khanka Massif may have been adjacent to the Songnen and Jiamusi massifs to the west and north respectively, during the Late Paleozoic–Mesozoic. Between the Songnen and Jiamusi massifs, the Mudanjiang Ocean initially opened in the Late Paleozoic and closed after the Late Jurassic (∼153.5 Ma) and produced the Heilongjiang Complex. The Paleo-Yuejinshan back-arc basin underwent extension in the Permian and finally closed after ∼216 Ma, forming the Yuejinshan Complex at ∼210–180 Ma. The Raohe Complex was accreted at ∼169–133 Ma and emplaced at ∼133–131 Ma. The large-scale sinistral strike-slip movement of the Dunmi Fault started later than ∼153.5 Ma and partially displaced the Heilongjiang Complex from the Mudanjiang area to the present-day Hulin Complex. The eastern CAOB was under a superimposed tectonic regime of the Paleo-Pacific Ocean and Paleo-Asian Ocean in the Late Paleozoic.

Fault geometry and kinematics of the 2021 Mw 7.3 Maduo earthquake from aftershocks and InSAR observations

The 2021 Mw 7.3 Maduo earthquake revealed the significant seismic hazard of faults developed within the Bayan Har Block of eastern Tibet, China (e.g., the Kunlun Pass–Jiangcuo Fault). Relocated aftershock data are in good agreement with the Interferometric Synthetic Aperture Radar (InSAR) coseismic displacement field and field investigations. In this study, we used aftershock point cloud fitting to model the relocated aftershocks of the Maduo earthquake, and obtained the detailed geometry and characteristics of the seismogenic fault. Based on InSAR coseismic deformation, the geometric model of the seismogenic fault and its slip distribution were retrieved. The results show that this event was shallow (0–10 km) and characterized by sinistral strike-slip motion. We identified four asperities along the fault strike; the maximum slip of 4.84 m occurred on the eastern segment of the fault, in an area where the strike changed. The results suggest that the central segment of the main seismogenic fault is mature and smooth, while western and eastern segments are complex and immature.

Late Quaternary neotectonics in the Bird’s Head Peninsula (West Papua), Indonesia: Implications for plate motions in northwestern New Guinea, western Pacific

New Guinea is a mountainous island in a tectonically active setting with regions experiencing rapid uplift rates as shown by the celebrated emergent coral reef terraces of the Huon Peninsula. In the northern Bird’s Head Peninsula of northwestern New Guinea, rapid uplift has been a feature of the tectonic history over the past 2.7 Ma with the development of the mountainous and highly dissected Kemum High (up to 2200 m) associated with the formation of the Central Bird’s Head Monocline, implying a long-term uplift rate approaching 0.8 m/ka. In this work, Late Quaternary uplift rates of up to 1.28 m/ka were determined for emergent coral reefs in the Manokwari region (northeast of the much larger Kemum High). The rapid uplift rates are based on 230Th-U ages (2.7 ± 0.3 to 246.3 ± 8.0 ka with most ages in the range 69–128 ka) on corals and coralline algae, sampled from calcarenites at elevations of 2.45–77.5 m above present sea level. The rapid uplift indicates neotectonic activity reflecting crustal thickening in the Quaternary and neptunian dykes probably related to gravitational instability. The present-day tectonic setting of the Bird’s Head Peninsula is cryptic, but the combination of uplift and tectonic activity shown by the earthquakes are consistent with ongoing oblique convergence between the Bird’s Head and the adjacent Pacific-Caroline plate. Over the past 2 Ma, plate motion between the Bird’s Head Peninsula and the Pacific-Caroline Plate has been accommodated by incipient south-dipping subduction along the Manokwari Trough to the north (with longer-lived subduction along the New Guinea Trench) and sinistral strike-slip movement along the Yapen fault whereas the Sorong Fault has been largely inactive.

Meso-cenozoic tectonic evolution of the ziyun-luodian fault in SW China

Regional-scale fault systems are important in adjusting intracontinental deformation. Closure of the Paleo-Tethys, Paleo-Pacific subduction, and India-continent-continent collision have all interacted to shape the Meso-Cenozoic tectonics of South China. The Ziyun-Luodian fault (ZLF) straddles across the Guizhou region in southwestern China. New petrographic and structural studies were conducted to reveal the structural evolution of the ZLF and regional deformation. At least three distinct deformation events are identified within the fault zone: During the Indosinian orogeny, dextral thrusting occurred along the ZLF, accompanied by moderate regional uplift in Guizhou, as evidenced by the Upper Triassic-Lower Jurassic disconformity. The main tectonic framework across Guizhou was established during the Yanshanian orogeny. Driven by the west-dipping Paleo-Pacific subduction (Middle Jurassic-Early Cretaceous), sinistral transpression occurred along the ZLF and NE-to N-S-trending fold belts in central-eastern Guizhou, and the NW-striking folds west of the ZLF were developed in under nearly E-W-directed compression. In the late Cenozoic, the ZLF may have undergone sinistral strike-slip movement, similar to the sinistral Ailaoshan-Red River shear zone. The Ziyun-Luodian fault plays an important role in accommodating the Meso-Cenozoic regional deformation in SW South China.

Delineating structural features of North Cameroon using the EIGEN6C4 high‐resolution global gravitational model

The Cretaceous basins of the West and Central African Rift System (WCARS) are characterized by sinistral strike–slip movements observed between the Benue and Arabian–Nubian microplates. These basins share a similar basin‐filling structure, history, and tectonic processes. They have attracted a significant interest in the study of their geodynamics and subsurface structure through geophysical exploration methods. Nevertheless, North Cameroon located in this microplate confluence has not yet been investigated in terms of identifying geological structures, such as lineaments and faults. To contribute to a better understanding of the northern Cameroon structural framework and its tectonic context, we investigate the lineaments in northern Cameroon by using the EIGEN‐6C4 gravitational model and a variety of recent processing techniques (Tilt derivative [TDR], Theta Map [TM], Horizontal tilt angle [TDX], and Edge Detector [ED]). Our results show that the lineaments are trending in ENE–WSW, NW–SE, NE–SW, and WNW–ESE directions. These directions are consistent with the Cretaceous Garoua Rift and granitoids of the Cameroon‐Chad line. The presented result clearly delineates continuous architectonic features of the structural edges of the Saharan Metacraton, the Cretaceous Garoua Rift, the Bibemi‐Léré granitoids, and the Adamawa faults.

Deformation history of the Feidong Segment of the Tan–Lu Fault zone in the Early Cretaceous: Implications for the tectonic evolution in eastern China

The Tan–Lu Fault zone (TLFZ) is the largest fault zone in eastern China and a typical and representative structure of the Circum–Pacific tectonic domain. The Late Mesozoic tectonic evolution of the TLFZ is greatly significant, since it revealed the Jurassic–Cretaceous tectonic evolution of eastern China and the subduction history of the Palaeo–Pacific Plate. However, its tectonic evolution in the Early Cretaceous remains controversial. Based on geological mapping, microstructural analysis, and LA–ICP–MS zircon U–Pb dating, we constrained the deformation history of the Feidong Segment of the TLFZ in the Early Cretaceous. Results showed that the Feidong Segment of the TLFZ experienced a strong sinistral strike–slip movement at the beginning of the Early Cretaceous (~143 Ma); it was subsequently subjected to normal faulting during the Early Cretaceous (135–102 Ma), which controlled the strong magmatic activities within the Feidong area. At the end of the Early Cretaceous (~100 Ma), a weak sinistral strike–slip movement occurred again along the TLFZ. The deformation temperatures of the two sinistral strike–slip shearing stages were 500–550°C and 400–450°C, respectively. The regional comparison indicated that the Early Cretaceous tectonic evolution of the TLFZ was actually the epitome of the contemporaneous tectonic evolution of eastern China and was the result of strain localization in the Cretaceous tectonic framework of eastern China.

The 2021 Mw7.4 Maduo earthquake: Coseismic slip model, triggering effect of historical earthquakes and implications for adjacent fault rupture potential

On 22 May 2021 (CST), an Mw7.4 earthquake struck Maduo County, Qinghai Province, China, which was the largest seismic event in China since the 2008 Mw7.9 Wenchuan earthquake. Several scientific questions associated with the event could be addressed: (1) what fault slip model can explain the Maduo earthquake? (2) what effects do historical earthquakes impose on the Maduo earthquake? and (3) what implications does the Maduo earthquake have for future rupture potential of adjacent tectonic faults? So we conduct a comprehensive study to answer the three questions by collecting satellite SAR images, GPS data, seismic waveform data, historical earthquakes, and aftershocks associated with the Maduo earthquake. The estimated fault slip model shows that the Maduo earthquake ruptures two faults in a manner of dominant sinistral strike-slip motion, with slip peaks of ~4.8 m occurring near the surface. The minor fault to the east dips to the south accommodating an obvious reverse slip, well consistent with reverse fault scarps, reverse faulting aftershocks, and significant upward surface displacements immediately south of this branch. Such a reverse slip is probably controlled by the motion of nearby major sinistral strike-slip faults (the Eastern Kunlun fault and the Maduo–Gande fault). Among 32 historical Mw≥ 6.0 earthquakes used in this study, we find that the 1937 Mw7.8 Huashixia earthquake may affect the Maduo earthquake most, delaying its occurrence by decreasing the Coulomb failure stress (CFS) at the hypocenter by > 1 bar and on the entire causative fault by an average of 0.68 bar. Besides, the Mw6.1 Yangbi earthquake, which occurred ~4.5 h ahead of the Maduo earthquake, appears to make little influence on the Maduo earthquake because it hardly perturbates the CFS at the hypocenter of the Maduo earthquake. Furthermore, the cumulative CFS change due to both the 32 historical earthquakes and the 2021 Maduo event indicates that the Tuosuo Lake–Maqu segment of the Eastern Kunlun fault may be at high risk of future rupture.

Uplift and subsidence at the periphery of the Lebanese Restraining Bend, Northern Dead Sea Fault

Bends and stepovers in strike-slip fault systems along active plate boundaries are widespread and introduce stress heterogeneities, affecting the regional strain field. The strain field associated with these complex fault structures has been extensively studied. Asymmetric uplift of the Lebanon Mountains, located at the fringe of an active plate boundary, the Dead Sea Fault system (DSF), together with subsidence of the Lower Galilee in northern Israel provides an exceptional example of the complex deformational pattern associated with a restraining bend. The deformation field with respect to the restraining bend is expressed by the asymmetric uplift of the Lebanon Mountains, west of the DSF. This asymmetry along with the subsidence of the Lower Galilee, an extensional region in northern Israel, could not be explained only by the impact of the restraining bend, ignoring additional regional tectonic features. We present the results of 3-D numerical modeling of the distributed deformation, utilizing damage rheology for brittle rock deformation of the seismogenic crust overlaying viscoelastic mantle. We use available geological and regional seismicity data to implement the realistic lithosphere structure and to delineate the major faults in the model as localized weak zones. The modeling results highlight the impact of several factors on the spatial distribution of crustal deformation, demonstrated by running different model scenarios. These scenarios allow us to isolate the impact of each tectonic element and show the strain pattern resulting from their superposition, starting with a restraining bend acting in a homogeneous layered crust. Our modeling results suggest that the extension observed in the Lower Galilee region and the asymmetric uplifted pattern west of the Lebanese Restraining Bend is the outcome of three interacting factors, which are the sinistral strike-slip motion along the Lebanese Restraining Bend, the significant variations in the crustal structure (depth to Moho), and the slow extension of the Irbid-Azraq rift zone.