Northwestern Segment Research Articles

The deep electrical structure characteristics and regional seismicity of the southeastern Jiali Fault Zone

Located in the southeastern Tibetan Plateau, the Jiali fault zone (JLF) is an important strike-slip fault system, which delineates the southern boundary of the south-eastward extrusion of the Tibetan Plateau. The JLF features long-recurrent seismicity and plays an important role in balancing the local stress field. However, previous geophysical studies have mostly focused on regional studies in the northwestern segment and the southeastern end of the JLF. Few geophysical studies have been conducted on the JLF segment in the Eastern Himalayan Syntaxis region. To better understand the deep structures of the JLF and to provide geophysical constraints for the regional seismicity, we propose a crustal-scale resistivity model derived from magnetotelluric profile data across the three branches (Xixingla, Puqu, and Parlung faults) of the southeastern segment of JLF. The three-dimensional electrical structure shows that the JLF is generally characterized by a series of northeast dipping features. Unlike Parlung and Puqu branches, which are currently relatively inactive, the Xixingla fault is imaged to dip steeply in the shallow part of the crust and gradually turninto a gentle dip angle in the deeper section, before ultimately converging with a low-resistivity layer in the mid-to-lower crust. As the recent seismicity shows a combination of thrusting and strike-slip mechanisms, the primary strike-slip tectonic background for the regional seismicity may be modified by the northeastward compression from the subducting Indian Plate. Combined with other geological and geophysical evidence, we suggest that the reverse thrust and strike-slip displacement of faults may jointly contribute to the combined dynamic mechanism for seismicity in this area, due to the intrusion of the Namcha Barwa metamorphic complex beneath the Lhasa terrane.

Flat-Slab Mechanics Transforming Double-Arc Expressions Along the Middle America Trench

AbstractThe southeast–northwest variation in the trench–volcano distance along the Middle America subduction zone is widely recognised to be due to the horizontal (flat) geometry of the descending Cocos plate (slab) in its northwestern part. In the topographic and gravitational expressions, the southeastern segment forms doubled low–high (i.e. trench–continental shelf edge–oceanic basin–volcanic arc) belts, whereas the northwestern segment forms wide doubled low–high belts. To define their attribution, the surface uplift rates were computed from a two-dimensional dislocation-based subduction model with hypocentre-based plate interface geometries. The trench-perpendicular plate-interface profiles exhibited similar curvature compositions, which were reflected in three (shallow, moderate depth and deep) convexities (downward bends) and one concavity (upward bend) between the moderate-depth and deep convex sections. The steady subduction along the first and second positive curvatures (shallow and moderate-depth convexities) in the southeastern and northwestern segments could serve as mechanical sources of short-wavelength double-arc formation. The latter two (negative and third positive) curvatures (concavity and deep convexity) in the northwestern segment produced distinct features including the narrow continental shelf, large trench–volcanic-arc distance and relevant long-wavelength double arcs. This was attributed to the direct contact of the flat elastic slab with the overriding plate.

Rapid India–Asia Initial Collision Between 50 and 48 Ma Along the Western Margin of the Indian Plate: Detrital Zircon Provenance Evidence

Constraining the collision timing of India and Asia requires reliable information from the coeval geological record along the ~2400 km long collisional margin. This study provides insights into the India–Asia collision at the westernmost margin of the Indian Plate using combined U-Pb geochronological data and sandstone petrography. The study area is situated in the vicinity of Fort Munro, Pakistan, along the western margin of the Indian Plate, and consists of the Paleocene Dunghan Formation and Eocene Ghazij Formation. The U-Pb ages of detrital zircons from the Dunghan Formation are mainly clustered between ~453 and 1100 Ma with a second minor cluster between ~1600 and 2600 Ma. These ages suggest that the major source contributing to the Dunghan Formation was likely derived from basement rocks and the cover sequence exposed mainly in Tethyan Himalaya (TH), Lesser Himalaya (LH), and Higher Himalayan (HH). Petrographic results suggest that the quartz-rich samples from the Dunghan Formation are mineralogically mature and have likely experienced log-distance transportation, which is possible in the case of an already established and well-developed river system delivering the sediments from the Craton Interior provenance. Samples of the overlying Ghazij Formation show a major detrital zircon age clustered at ~272–600 Ma in the lower part of the formation, comparable to the TH. In the middle part, the major cluster is at ~400–1100 Ma, and a minor cluster at ~1600–2600 Ma similar to the age patterns of TH, LH, and HH. However, in the uppermost part of the Ghazij Formation, ages of <100 Ma are recorded along with 110–166 Ma, ~400–1100 Ma, and ~1600–2600 Ma clusters. The <100 Ma ages were mainly attributed to the northern source, which was the Kohistan-Ladakh arc (KLA). The ~110–166 Ma ages are possibly associated with the TH volcanic rocks, ophiolitic source, and Karakoram block (KB). The Paleozoic to Archean-aged zircons in the Ghazij Formation represent an Indian source. This contrasting provenance shift from India to Asia is also reflected in the sandstone petrography, where the sample KZ-09 is plotted in a dissected arc field. By combining the U-Pb ages of the detrital zircons with sandstone petrography, we attribute this provenance change to the Asia–India collision that caused the provenance shift from the southern (Indian Craton) provenance to the northern (KLA and KB) provenance. In view of the upper age limit of the Ghazij Formation, we suggest the onset of Asian–Indian collision along its western part occurred at ca. 50–48 Ma, which is younger than the collision ages reported from central and northwestern segments of the Indian plate margin with 70–59 Ma and 56 Ma, respectively.

Miocene Petit-Spot Basanitic Volcanoes on Cretaceous Alba Guyot (Magellan Seamount Trail, Pacific Ocean)

New data obtained from core samples of two boreholes and dredged samples from the Alba Guyot in the Magellan Seamount Trail (MST), Western Pacific, including the 40Ar/39Ar age determinations of basanite, and the mineralogy of basanite, tuff, tuffite, mantle-derived inclusions in basanite and tuff (lherzolite xenolith and Ol, Cpx, and Opx xenocrysts), and calcareous nannofossil biostratigraphy, have implications for the guyot′s development and history. Volcanic units in the upper part of the Alba Guyot main edifice and its Oma Vlinder satellite, at sea depths between 3600 and 2200 m, were deposited during the Cretaceous 112 to 86 Ma interval. In the following ~60 myr, the Alba Guyot became partly submerged and denuded with the formation of a flat summit platform while the respective fragment of the Pacific Plate was moving to the Northern Hemisphere. Volcanic activity in the northeastern part of the guyot summit platform was rejuvenated in the Miocene (24–15 Ma) and produced onshore basanitic volcanoes and layers of tuff in subaerial and tuffite in shallow-water near-shore conditions. In the Middle-Late Miocene (10–6 Ma), after the guyot had submerged, carbonates containing calcareous nannofossils were deposited on the porous surfaces of tuff and tuffite. Precipitation of the Fe-Mn crust (Unit III) recommenced during the Pliocene–Pleistocene (<1.8 Ma) when the guyot summit reached favorable sea depths. The location of the MST guyots in the northwestern segment of the Pacific Plate near the Mariana Trench, along with the Miocene age and alkali-basaltic signatures of basanite, provide first evidence for petit-spot volcanism on the Alba Guyot. This inference agrees with the geochemistry of Cenozoic petit-spot basaltic rocks from the Pacific and Miocene basanite on the Alba Guyot. Petit-spot volcanics presumably originated from alkali-basaltic melts produced by decompression partial melting of carbonatized peridotite in the metasomatized oceanic lithosphere at the Lithosphere–Asthenosphere Boundary level. The numerous volcanic cones with elevations of up to 750 m high and 5.1 km in basal diameter, discovered on the Alba summit platform, provide the first evidence of voluminous Miocene petit-spot basanitic volcanism upon the Cretaceous guyots and seamounts of the Pacific.

Westward Migration of the Chenghai–Jinsha Drainage Divide and Its Implication for the Initiation of the Chenghai Fault

The Chenghai Fault in the Chuan–Dian block terminates at the northwestern segment of the Red River Fault, and is a significant seismogenic structure. The kinematic evolution of this fault should be closely related to the regional tectonic deformation. However, it is difficult to obtain information on structural deformation of the Chenghai Fault due to the large amount of precipitation and well-developed vegetation. The Chenghai normal faulting may drive drainage reorganization in this region, which provides a new perspective for reconstructing and evaluating the tectonic history. High-resolution digital elevation models (DEM) obtained by remote sensing greatly facilitate the study of drainage evolution and active tectonics. We use two methods (χ-plot and Gilbert metrics) to measure the drainage divide stability based on the ALOS DEM (12.5 m resolution) and further reproduce the drainage evolution process in response to the asymmetric uplift by numerical modeling. The results show that the Chenghai–Jinsha drainage divide, hosted by the footwall block of the Chenghai Fault, is migrating westward (away from the Chenghai Fault) and will continue moving ~2.2–3.5 km to reach a steady state. Its migration is controlled by the Chenghai normal faulting. The Chenghai–Jinsha drainage divide formed close to the Chenghai Fault’s surface trace and continues to migrate westward in response to the asymmetric uplift. It only took a few million years for the Chenghai–Jinsha drainage divide to migrate to its current location based on the numerical modeling. The restoration of the drainage reorganization implies that the Chenghai Fault initiated in the Pliocene, which probably results from kinematic reversal along the Red River Fault.

Coseismic deformation analysis of the 2017 Milin Ms 6.9 earthquake in the Namche Barwa Syntaxis: Implications for regional tectonics

The 2017 Milin earthquake occurred near Namche Barwa on the southeastern Tibetan Plateau. This research employed Sentinel-1 imagery to capture the corresponding coseismic deformation field and adopted a joint inversion approach using geodetic measurements and teleseismic waveform data to assess earthquake mechanics. The coseismic deformation indicated distinct differential movements, indicating a thrust movement of this fault with uplift in northeast side. The calculated seismic moment magnitude was Mw 6.5, with the fault striking of 305° and a dip angle of 72° The earthquake hypocenter was located at a depth of approximately 10 km, and the maximum fault slip was approximately 1.08 m. The event was attributed to the northwestern segment of the Xixingla fault. Numerical simulations indicated a peak ground velocity of approximately 0.3 m/s. The northwestern segment of the Xixingla fault was identified as the seismogenic fault of the event. Furthermore, the Coulomb stress analysis indicates that the earthquake induced stress loading on the Dongju–Milin and Jiali faults. The surface strain analysis reveals a region of high strain adjacent to the fault. The 2017 Milin earthquake occurred because the Xixingla fault underwent predominantly thrust-type sliding due to the continuous tectonic stress induced within the Tibetan Plateau. Notably, the middle segment of the Xixingla fault currently experiences relatively low seismic activity and is in a state of stress and strain accumulation. Thus, strong earthquakes may occur within the middle segment of the Xixingla fault.

Submarine canyon development controlled by slope failure and oceanographic process interactions

The southeastern Australian margin hosts a series of submarine canyons. Although the origin and evolution of canyons within the northwestern segment of the margin is relatively well studied, their quantitative morphology, interaction with longshore drift currents and slope failure remain poorly understood in the southeastern region. In this study, high-resolution bathymetry and 3D seismic reflection datasets revealed five main submarine canyons present in the central offshore Otway Basin. The canyons have V-shaped, evolving to U-shaped morphology downslope with sedimentary infill characterized by medium–high amplitudes, recognizable stratal pattern and localized chaotic seismic reflections. Analysis reveals these canyons were initiated by retrogressive slope failure on the continental slope, that once the shelf edge was reached and subsequently incised, development of the canyon heads was influenced by the shelf parallel Zeehan Current, active on the continental shelf of the region. The heads of the shelf-incised canyons preferentially migrate northwestward and were infilled by laterally accreting sedimentary packages characterized by southeast dipping seismic reflections. These indicate an early erosive phase followed by a period of deposition, a result of the prevalent eastward flowing Zeehan Current. These results have important implications for understanding of the mechanisms that control initiation and development of submarine canyons, and their morphology, both offshore southeastern Australia, and similar settings on continental margins worldwide.

Middle Triassic basaltic pyroclastic rocks from the Mt. Medvednica ophiolitic mélange (NW Croatia): petrology, geochemistry and tectono-magmatic setting

Hectometric blocks of Middle Triassic mafic pyroclastic rocks, represented by volcanic agglomerates/breccias and lapilli tuffs, form part of the ophiolitic mélange of Mt. Medvednica, situated in the southwestern segment of the Zagorje-Mid-Transdanubian Zone. These rocks share petrochemical characteristics with pyroclastic derivatives of alkali, within-plate basaltic lavas of Mts. Medvednica, Samoborska Gora, and Kalnik, indicating the occurrence of explosive events preceding the dominant effusive submarine volcanism during the Middle Triassic (Illyrian-Fassanian?) stages. The formation of these pre-ophiolitic pyroclastics is associated with an intracontinental rift setting and reflects melts derived from an OIB-type enriched mantle plume source. These pyroclastics represent uncontaminated melts that erupted through a highly thinned continental crust. In geodynamic terms, the formation of pyroclastites occurred during the Late Anisian-Early Ladinian along the continental margin of Palaeotethys through the proto back-arc rifting of continental lithosphere (Adria Plate), leading to the formation of the Maliak/Balkan Neotethys Rift, in the emerging northwestern segment of Neotethys. The investigated pyroclastic rocks of Mt. Medvednica document the extension in an evolved intracontinental rift basin, which immediately preceded the generation of the initial Neotethyan oceanic lithosphere during the Upper Triassic.

Spatial Dynamics of Land Use Land Cover of Minna City and Environs, Niger State, Nigeria

Aims: Spatial dynamics of land use land cover of Minna city and environs, Niger State, Nigeria.
 Study Design: Survey and longitudinal research were carried out.
 Place and Duration of Study: Minna town, Niger State, Nigeria between 1990 and 2022.
 Methodology: This study investigated the dynamics of land use land cover of Minna city and environs, Niger State, Nigeria using satellite remote sensing and Geographic Information System (GIS) technique. 
 Results: Findings of the study showed that in 1990, land use type was dominated by agricultural land (50%), followed by vegetation land (30%). However, built-up area was less than 10% indicating that urban heat stress was limited. It was observed that the built-up area concentrated on the center and north-western segments of the city. In 2010, bare ground dominated the land use type of Minna city and environs at the rate of 45%. This was followed by agricultural land at the rate of 35%. The built-up area occupied 15% of the entire land surface area of the city, indicating a tremendous rise from the previous decades. In 2022, the land use type showed a tremendous rise in agricultural land at the rate of 37%. This was followed by bare ground at an alarming increase of 36%. The built-up area ranked third at the rate of 20%, showing that the city had a severe urban heat effect due to heat generated by urban pavement materials.
 Conclusion: Thus, the practice of sustainable land use, good implementation of forest practice, appropriate water resources conservation and the promotion of alternative livelihood to agriculture should be implemented for the Minna inhabitants to reverse the situation of LULC changes without further delay.

A Physics-Based Seismic Risk Assessment of the Qujiang Fault: From Dynamic Rupture to Disaster Estimation

This study achieved the construction of earthquake disaster scenarios based on physics-based methods—from fault dynamic rupture to seismic wave propagation—and then population and economic loss estimations. The physics-based dynamic rupture and strong ground motion simulations can fully consider the three-dimensional complexity of physical parameters such as fault geometry, stress field, rock properties, and terrain. Quantitative analysis of multiple seismic disaster scenarios along the Qujiang Fault in western Yunnan Province in southwestern China based on different nucleation locations was achieved. The results indicate that the northwestern segment of the Qujiang Fault is expected to experience significantly higher levels of damage compared to the southeastern segment. Additionally, there are significant variations in human losses, even though the economic losses are similar across different scenarios. Dali Bai Autonomous Prefecture, Chuxiong Yi Autonomous Prefecture, Yuxi City, Honghe Hani and Yi Autonomous Prefecture, and Wenshan Zhuang and Miao Autonomous Prefecture were identified as at medium to high seismic risks, with Yuxi and Honghe being particularly vulnerable. Implementing targeted earthquake prevention measures in Yuxi and Honghe will significantly mitigate the potential risks posed by the Qujiang Fault. Notably, although the fault is within Yuxi, Honghe is likely to suffer the most severe damage. These findings emphasize the importance of considering rupture directivity and its influence on ground motion distribution when assessing seismic risk.

The evolution of the Mesozoic lithosphere of northwestern Neotethys: a petrogenetic and geodynamic perspective

A complex and chaotic assemblage of the north Croatian inselbergs, considered a geological conundrum, is marked by omnipresent ophiolite mélange. This is a vestige of the unbroken formation of the lithosphere in the northwestern segment of Neotethys during the Mesozoic, spanning from the late Anisian to the late Tithonian. In this contribution, we present detailed mineralogical, petrological, geochemical and isotopic data on the mélange collected from 1991 to 2023. These data include the entire normal ophiolite sequence, from mantle tectonites and cumulate ultramafic rocks through cumulate and isotropic gabbro and sheeted dyke complex to massive and pillow lavas with interbedded radiolarian cherts. We found that the continuous development of oceanic lithosphere during the Mesozoic is recorded by seven geochemical groups of ophiolitic rocks, each representing a distinct basalt–gabbro suite. Based on their geochemical and isotopic characteristics, a sequence of petrogenetic processes and tectonomagmatic events has been reconstructed. Proposed geodynamic models that shed light on the Mesozoic evolution of the northwestern segment of Neotethys are consistent with the current geodynamic understanding of the broader Mediterranean region. The similarities in the tectonomagmatic and geodynamic history of NW Neotethyan ophiolites and ophiolites from the Dinaridic–Albanide–Hellenide belts suggest that they evolved together, probably within a single branch of the Neotethys Ocean during Triassic to Jurassic time. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Present-day crustal deformation based on GPS measurements in southeastern Tibetan Plateau: implications for geodynamics and earthquake hazard

GPS-derived strain rates can provide a tight constraint in understanding tectonic evolution of the Tibetan Plateau and are helpful in seismic hazard assessment. For this purpose, we at first verify the method, proposed by Zhu et al. in 2005 and 2006, for the computation of the strain rates, and found that the approach is reasonable and accurate. Then, based on the updated GPS data, we compute strain rates in southeastern Tibetan Plateau (SETP). The computed results showed that the strain rates in the Sichuan Basin and South China Block are very small, and the high values are largely concentrated along the Sagaing Fault and Xianshuihe-Anninghe-Xiaojiang fault system. In addition, the highest principal strain rates are located around the eastern Himalayan syntaxis (EHS), with the compressive orientations perpendicular to the Main Thrust Belt. In particular, the calculated extensive deformation basically matches the normal faulting earthquakes. In general, the characteristic of the strain rate distribution is in good agreement with the tectonic structures from the geological and geophysical investigations. At last, according to the strain rates, seismicity, and tectonic structures, we estimate five most likely zones for future major earthquakes in SETP. These areas include the Zemuhe Fault, northwestern segment of the Red River Fault, and at the intersection between the Ganzi-Yushu Fault and the Xianshuihe Fault, and at the one between the Zhongdian Fault and Jinshajiang Fault. Consequently, this study is significant in deep understanding of the geodynamics in the Tibetan Plateau and earthquake hazard assessment.

Slip partitioning and seismogenic stress buildup adjacent to the junction of the Lenglongling fault and the Tuolaishan fault: Insights from kinematically constrained numerical simulations

Understanding fault kinematics plays a crucial role in estimating seismic hazards and linking the relationship between seismogenic stress buildup and tectonic deformation. The northwestern segment of the Qilian-Haiyuan fault zone (QHFZ) serves as a natural laboratory for investigating how the oblique block motion decomposes into a complex fault system. In this study, we constructed a 3D FEM model incorporating the active faults as contact discontinuities to obtain a continuous numerical image of fault slip rates. Our findings revealed that deformation partitioning within the context of oblique block convergence generates a spatially heterogeneous distribution of fault slip rates. The inferred strike-slip rates of the Tuolaishan fault and the Lenglongling fault (LLLF) range from approximately 2 to 4 mm/yr and 4 to 7 mm/yr, respectively. The Lenglongling fault's slip behavior exhibits a spatial transition, with a dominant strike-slip component dominating in the western part and gradually changing to a combination of reverse faulting and strike-slip in the eastern segment. The Northern Lenglongling fault (NLLLF), characterized by a listric shape, merges with the LLLF in the deep crust, resulting in the formation of a positive flower structure that enhances the accumulation of compressional seismogenic stress. The region with high shear strain rates within this area has experienced significant earthquakes, including the 2022 Menyuan MS 6.9 earthquake, the 2016 Menyuan MS 6.4 earthquake, and the 1986 Menyuan MS 6.4 earthquake. Our numerical study gained valuable insights into the relationship between slip partitioning, fault structures, and regional stress.

The First Detrital Zircon Data on the Northwestern Precambrian Yenisei Ridge: Identification of the Continental–Arc Kiselikha Terrane

Northwestern segment of the Precambrian Yenisei Ridge contains ophiolite and is known in the literature as the Isakovka terrane or Isakovka domain. We suggest dividing it into two belts: the Kiselikha one (western) and Torzhikha (eastern), which differed in geodynamic regime during the late Neoproterozoic (~750–600 Ma). It is believed that the Kiselikha belt is composed mostly of volcanic rocks erupted at island arc setting in the second half of the Neoproterozoic, and that collision of this arc with Siberian continent formed the Yenisei Ridge orogen. This idea has not been sufficiently confirmed by geological and geochronological data. Dating of four detrital zircon samples extracted from sedimentary and volcanic-sedimentary rocks in the southern part of the belt revealed that the sampled strata belong to three different Precambrian levels: the Mesoproterozoic, the mid Neoproterozoic (800–750 Ma), and the end of the Neoproterozoic (620–600 Ma). Thus the authorized stratigraphic layout of the belt as well as its proposed island-arc origin require revision. By this paper we announce the identification of the Kiselikha terrane, which was a part of active margin of the Siberia paleocontinent at the beginning of the Neoproterozoic. Approximately in the middle of the Neoproterozoic, this block was rifted off Siberia and further evolved as a microcontinent bounded by an active margin from the outer side.

Paleoproterozoic Crust–Mantle Interaction in the Khondalite Belt, North China Craton: Constraints from Geochronology, Elements, and Hf-O-Sr-Nd Isotopes of the Layered Complex in the Jining Terrane

The Paleoproterozoic Khondalite Belt, located in the northwestern segment of North China Craton (NCC), is characterized by widespread high-temperature/ultrahigh-temperature (UHT) granulite/gneiss and large-scale magmatic activity. The tectonic evolution is still controversial. Here, we report new geochronological, elemental, and Hf-O-Sr-Nd isotopic data for a Paleoproterozoic layered complex in the Jining terrane to constrain the tectonic evolution of the Khondalite Belt. In situ zircon U-Pb dating indicates that the Sanchakou gabbros were emplaced between ~1.94 Ga and ~1.82 Ga, which might be the heat source of UHT metamorphism. The elemental and Hf-O-Sr-Nd isotopic analysis shows that the formation of Sanchakou gabbros is consistent with the assimilation and fractional crystallization (AFC) process. The magma originates from the 10%~20% partial melting of the spinel + garnet lherzolite mantle. The Sanchakou gabbros are magmatic crystallization products mixed with crustal wallrocks in the magma chamber. We have established a tectonic evolution model involving asthenosphere upwelling after the amalgamation of the Ordos and Yinshan Blocks at ~1.95 Ga.

Diamond-bearing lithosphere of the Siberian platform (based on geophysical data). Precambrian heredity, Paleoproterozoic plume magmatism, diamond content of the Anabar tectonic province

In the first part of the article [15], we presented the results of the analysis of the structural relationship of prospective areas and tectonic zonation of the Siberian Platform (SP). Here we demonstrate the reflection of the heredity of structural-material complexes (SMC) of the Precambrian basement of the SP to the Paleoproterozoic mantle-plume events in the geophysical fields. The analysis of the attributes of the prospective areas, as images of the SMC of the deep Precambrian, made it possible to determine the area of maximum thermal-mantle impact on the SP Precambrian lithosphere of the Early Proterozoic superplume, as well as its presumed center in the northwestern segment of the SP. The spatial distribution of the attributes, revealing the correlation of the components with the prospecting areas, contributed to the refinement of the position of the system of orthogonal lineaments on the SP, in general, corresponding to the framework reported in Basharin’s work [3]. The published geological and geophysical materials and the results of processing geophysical data showed that the deep structure of the central part of the Anabar tectonic province (AN) has the attributes characteristic of the Archean diamondiferous cratons. This can indicate the presence of a diamondiferous lithospheric root within AN. The southwestern segment of AN corresponds with the position of the Angara-Vilyui ore belt (AVRP) [2], which, along with other data, can allow us to extend the ore belt in the northeast direction, as well as recognize it in the rank of the Siberian diamond province. The prospects for the discovery of new industrial-diamond-bearing kimberlite fields are associated with the territory of the AN, the positions of the diamond-bearing lithospheric root, zones of deep crustal-mantle faults within it and its boundaries.

Comparison of Some Physical Properties of Soil and River Sediment

In this research, a comparison of some physical properties of two natural media was made, namely, a selected soil sample from the northwestern segment of the Skopje valley and a sample of river sediment from the river Vardar. The primary parameters of the samples are determined, such as: granulometric composition, specific mass and volume mass in different compacted condition. The secondary physical characteristics are followed, which are a consequence of the previously listed, which are the porosity of the samples and the capillary characteristics. These, further define the following characteristics of the media: maximum water permeability, characteristics of the water transport process and heat transfer through the examined sample layer. Simultaneously, the changes of temperature and moisture at a defined point of the experimental layers are monitored (under appropriate experimental conditions, namely, an emphasized / amplified ΔT is set) and the phenomena are explained.

Evolution of Coulomb failure stress in Sulaiman Lobe, Pakistan, and its implications for seismic hazard assessment

In this research work, we present the evolution of Coulomb failure stress (CFS) in the Sulaiman Lobe and its implications for seismic hazard assessment. The Chaman transform fault, ~1,000 km long, is the major active fault that marks the western boundary between Pakistan and Afghanistan on the Indian Plate. To date, few studies have been conducted to unveil the interactions among earthquakes and the implications of these interactions for seismic hazard assessment in the region. We thoroughly investigated the published and online catalog to construct a sequence of major earthquakes that occurred in this region during the past. The final earthquake sequence was composed of 15 earthquakes of <italic>M</italic>_w ≥ 6.0, beginning with the 1888 earthquake. We used the stress-triggering theory to numerically simulate the evolution of CFS caused by these earthquakes. The numerical results revealed that 8 out of 15 earthquakes were triggered by the preceding earthquakes. The earthquakes in 1908, 1910, 1935, 1966, and 1997 were rather independent earthquakes in this sequence. Although the epicenters of the 1975a and 1975b earthquakes were in the stress shadow zone, the partial rupture segments of both these earthquakes were in high-CFS regions. The CFS induced by the 1935 earthquake was notable, as it later triggered the 2008 doublet. Moreover, our results revealed that the northern segment of the Chaman Fault, the southern segment of the Ghazaband Fault, and the northwestern segment of the Urghargai Fault demonstrated a high change in CFS that could trigger seismicity in these regions. The necessary arrangements must therefore be made to mitigate any possible seismic hazards in the region.

Geochronology and Petrogenesis of the Gol Mod Massif: Implications for the Geodynamic Evolution of the Orkhon-Selenge Belt, Northwestern Mongolia

The Orkhon-Selenge Belt is a Late Permian to Early Triassic volcanic plutonic belt located in northern Mongolia and is part of the Central Asian Orogenic Belt. The Selenge Complex, which is a part of the Orkhon-Selenge Belt, is a key area for studying the tectonic and magmatic evolution of the Central Asian Orogenic Belt. This study aims to contribute to understanding of the geodynamic evolution of the Orkhon-Selenge Belt by investigating the petrology, geochemistry and geochronology of the rocks in the region. Our results indicate that intrusive rocks were characterized as high-K, Calc-alkaline series and metaluminous to weakly peraluminous I-type granite affinities and their geochemical characteristics are indicating as arc-like geochemical signatures with depleted in elements such as Nb, Ta, Ti and Y and enriched in elements such as Rb, Cs, Th, K and light rare earth elements. Using zircon U-Pb dating, we determined an age of 257.3±0.73 Ma for the alkali granite, suggesting that south-western part of the Orkhon-Selenge Belt formed during the Late Permian time. The Selenge pluton, which is closely related to Erdenet-Ovoo porphyry type mineralization, is a composite intrusion. However, the zircon grains display magmatic and low oxygen fugacity conditions, which characteristics are likely the effect of weak mineralization of magma ascent with Late Permian tectonothermal event in the south-west part of the Orkhon-Selenge Belt. The results of this study will provide insights into the formation and evolution of the north-western segment of the Mongol-Okhotsk Belt, and will have implications for our understanding of the tectonic history of this region.

Petrogenesis of Late Devonian I- and A-type granitoids, and associated mafic microgranular enclaves in the northwestern North Qaidam Orogenic Belt, China: Implications for continental crust growth during the post-collisional stage

Post-collisional magmatic intrusions and their mafic microgranular enclaves (MMEs) can provide significant insights into granite petrogenesis, crust-mantle interaction, and the reworking and growth of the continental crust. A combined petrological and geochemical study was carried out on MMEs and their host Niubiziliang I-type felsic composite pluton (granite and granodiorite) and aluminous A 2 -type Datonggou biotite granite from the Niubiziliang batholith in the northwestern segment of the North Qaidam Orogenic Belt (NQOB), China. This study presents whole-rock major- and trace elements and Sr Nd isotopic compositions, electron probe microanalyses of plagioclase, hornblende, and biotite, and zircon U Pb dating and Hf isotopes. Zircon U Pb dating demonstrates that the studied rocks formed during the Late Devonian (ca. 382 Ma). The Niubiziliang composite felsic pluton samples yield a metaluminous calc-alkaline to high-K calc-alkaline I-type granitic composition. The MMEs from Niubiziliang composite felsic pluton have low SiO 2 (52–64 wt%) and high MgO (2.8–4.9 wt%) concentrations. Both MMEs and host granites are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and are depleted in P and high field strength elements (HFSEs). All MMEs and host granitoids samples from Niubiziliang have indistinguishable Sr-Nd-Hf isotopic compositions characterized by initial Sr isotope ratios of 0.70545–0.70633 (MMEs), 0.70555–0.70742 (host rock), whole-rock ε Nd ( 382 Ma ) values of −2.95 to +1.6, −0.25 to +3.5, and zircon ε Hf( 382Ma ) values of +2.2 to +10.2, +1.3 to +10.4, respectively. The Niubiziliang composite felsic pluton is a product of mixing juvenile crust-derived and depleted mantle-derived melts in a 40:60 proportion. MMEs crystallized from the same source as the host granite, and they were formed by self-mixing with the earlier crystallized cumulates when they were affected by the emplacement of subsequent hot magmas. The Datonggou biotite granite has high TFe 2 O 3 /(TFe 2 O 3 + MgO), TiO 2 /MgO, Ga/Al, and Y/Nb ratios, high zircon saturation temperatures (802–846 °C), high HFSE concentrations (e.g., Zr, Nb, and Y), moderate (Na 2 O + K 2 O) concentrations, and low Eu and Sr concentrations. Interstitial biotite has high Fe 2 O 3 but low MgO concentrations, similar to those of aluminous A-type granite. The above-mentioned characteristics imply that the Datonggou biotite granite is an aluminous A 2 -type granite. Considering their high initial Sr isotopic composition (0.72218–0.72652), low ε Nd ( 382 Ma ) (−6.73 to −6.31), and comparatively old two-stage Nd model ages (1640–1674 Ma), we suggest the biotite granite was generated by partial melting of Ordovician-Silurian granitoids with tonalitic compositions at H T -L P conditions. The formation of coeval I- and aluminous A 2 -type granitoids in this region was probably related to the lithospheric mantle delamination and associated asthenospheric upwelling at ca. 390 Ma. The I-type granitoids and MMEs from the Niubiziliang area represent a net addition of juvenile mantle to the crust and, given the wide distribution of contemporaneous I-type granitoids, the post-collisional magmatism has significantly contributed to the growth of the continental crust in the NQOB. • The Niubiziliang granitoids, MMEs, and biotite granite were emplaced at 382 Ma. • Lithospheric delamination occurred at ca. 390 Ma in the North Qaidam belt. • The post-collisional granitoids contribute to the growth of the continental crust.