Middle Gobi Research Articles

Mechanism controlling groundwater chemistry in the hyper-arid basin with intermittent river flow: insights from long-term observations (2001–2023) in the lower Heihe River, Northwest China

The geochemical processes of groundwater in arid regions are generally influenced by both natural hydrological processes and human activities. However, impacts of water-rock interactions on groundwater recharge via hydrological processes, controlled by both intermittent river water flow and groundwater withdrawals, is still poorly understood. In this study, 327 groundwater chemistry datasets collected from the upper, middle (including Gobi and riparian zones), and lower regions of the Ejina Delta in Northwest China from 2001 to 2023 were analyzed. Our results revealed that the total dissolved solids (TDS) concentration of groundwater in Ejina Delta ranged from approximately 881.5 ± 331.6 mg/L in the upper regions to 1,953.6 ± 1,208.5 mg/L in the lower regions, with an increasing trend observed. Ecological water conveyance (EWC), recharging aquifer through intermittent river water flow, resulted in a decrease in TDS concentrations from 2001 to 2023 mainly in the upper region. While irrigation notably affected groundwater chemistry in the lower region, resulting in a substantial increase in groundwater salinity. Groundwater chemistry in the Middle Gobi region remained relatively stable over the study period. Generally, the hydrochemical composition shifted from the Na-Mg-SO4-HCO3 and Na-Mg-Ca-SO4-HCO3 types in the upper region to Na-Mg-SO4-HCO3 and Na-Mg-SO4-Cl types in the lower region, with Na-SO4-Cl predominant in the Middle Gobi. These shifts were likely be attributed to the interplay of water-rock interactions, coupled with evaporation-crystallization processes. Inverse modeling using PHREEQC revealed that in the upper-middle region, primary water-rock interactions involved calcite dissolution and the precipitation of dolomite, gypsum, halite, and sylvite salts, as well as cation exchange reactions (2NaX+Ca2+→CaX2+2Na+). In contrast, the hydrogeological system in the middle-lower region exhibited an opposite pattern of water-rock interactions. Overall, ecological water conveyance partially facilitated water-rock interactions during lateral groundwater flow, while irrigation disrupted the natural hydrogeochemical equilibrium, involving halite dissolution and opposite cation exchange reactions compared to other regions.

Мел-палеогеновые базальты и щелочные базальтоиды Юго-Восточной Монголии: 1. Распределение в пространственно-временном геолого-геохронологическом контексте позднего мезозоя и кайнозоя

Volcanic fields are described in southeastern Mongolia along the Mandalgobi – Dariganga profile as a key area for understanding the late Mesozoic and Cenozoic geological evolution of Asia: the late Cenozoic Dariganga volcanic field at the eastern end of the profile, the Cretaceous-Paleogene Middle Gobi fields at the western end, and the Jurassic-Cretaceous ones along its entire length.

Medicinal plant resources in Inner Mongolia autonomous region of China and Mongolia: a comparative study

Inner Mongolia autonomous region of China and Mongolia are the primary regions where Chinese and Mongolian medicine and its medicinal plant resources are distributed. In this study, 133 families, 586 genera, and 1 497 species of medicinal plants in Inner Mongolia as well as 62 families, 261 genera, and 467 species of medicinal plants in Mongolia were collected through field investigation, specimen collection and identification, and literature research. And the species, geographic distribution, and influencing factors of the above medicinal plants were analyzed. The results revealed that there were more plant species utilized for medicinal reasons in Inner Mongolia than in Mongolia. Hotspots emerged in Hulunbuir, Chifeng, and Tongliao of Inner Mongolia, while there were several hotspots in Eastern province, Sukhbaatar province, Gobi Altai province, Bayankhongor province, Middle Gobi province, Kobdo province, South Gobi province, and Central province of Mongolia. The interplay of elevation and climate made a non-significant overall contribution to the diversity of plant types in Inner Mongolia and Mongolia. The contribution of each factor increased significantly when the vegetation types of Inner Mongolia and Mongolia were broadly divided into forest, grassland and desert. Thus, the distribution of medicinal plant resources and vegetation cover were jointly influenced by a variety of natural factors such as topography, climate and interactions between species, and these factors contributed to and constrained each other. This study provided reference for sustainable development and rational exploitation of medicinal plant resources in future.

Permian–Triassic magmatic rocks in the Middle Gobi volcanic-plutonic belt, Mongolia: revisiting the scissor-like closure model of the Mongol-Okhotsk Ocean

Permian–Triassic magmatic rocks in the Middle Gobi volcanic-plutonic belt, Mongolia: revisiting the scissor-like closure model of the Mongol-Okhotsk Ocean

Hydrous Melting Driven Upwelling From the Mantle Transition Zone in the Mongolia Plateau Revealed by Receiver Function Analysis

AbstractThe detailed images of the mantle transition zone (MTZ) give insights into the nature of mantle upwelling from the deep Earth. We use receiver function to investigate the MTZ structure beneath the Mongolia Plateau using earthquakes recorded by 223 stations deployed in the Central Asian Orogenic Belt. The topographies of the 410 km (D410) and 660 km (D660) discontinuities are both characterized by slight depressions in most parts of the Mongolia Plateau. An obvious low‐velocity layer (LVL) atop the MTZ with an average thickness of ∼40 km is observed beneath this study area, indicating the hydrous partial molten layer atop the D410 and a hydrous MTZ. The D410 depth of ∼410 km and the LVL up to ∼60 km thick beneath the Dariganga volcano imply that there is a chemically distinct hydrous upwelling related to the subducted Pacific slab rather than a classic thermal‐dominated upwelling. The ∼10 km thinned MTZs are found beneath the western Hangay Dome and the Middle Gobi volcano. A narrow NS‐trending MTZ thickening zone extending from the Hovsgol rift to the central Hangay Dome is mainly caused by a ∼10 km depression of D660. We speculate that the mantle upwelling beneath the Hangay Dome may be related to the stagnant slab descending through the MTZ, rather than being rooted from the deep lower mantle. Hydrous melting‐driven upwellings from the MTZ beneath the Mongolia Plateau play a key role in intraplate volcanism.

Quantifying the contribution of dust sources in the arid area of northwest China using multivariate statistical techniques and Bayesian mixing models

In this study, topsoil samples and dust samples during dust storms were collected from the main dust source in northwest China, the geochemical elements were measured, and the contribution of dust sources was quantified using a discriminant function analysis (DFA) model and a MixSIAR model. Finally, the accuracy of the model was evaluated using an artificial mixture sample. The results showed that the dust sources and their contributions were significantly heterogeneous due to the natural and anthropogenic influences on the source-transport-sink process. DFA and MixSIAR models showed that the main dust sources in Dunhuang and Jiuquan were the Western Gobi and Western oasis, and Zhangye was mainly influenced by the Western Gobi, Western oasis, Middle Gobi, and Central oasis, with the influence of the Middle oasis being more pronounced. The Eastern Gobi, Eastern oasis, Badain Jaran desert, and Tengger desert have a greater influence on Jinchang, Wuwei, Baiyin, and Lanzhou. The contribution of each dust source in the Hexi region was found to show a significant distance effect. The accuracy of the models varied depending on the number of dust sources. The study provides new ideas for quantifying the contribution of dust source and for global dust storm control.

Carboniferous magmatic records of central Mongolia and its implications for the southward subduction of the Mongol–Okhotsk Ocean

ABSTRACT The now-extinct Palaeozoic to Mesozoic Mongol–Okhotsk Ocean is evidenced by the Mongol–Okhotsk suture, which stretches from central Mongolia to the Sea of Okhotsk. The geodynamics of southward subduction of the Mongol–Okhotsk Ocean remain enigmatic, especially whether the subduction began during the Carboniferous is highly debated. In this paper we present new zircon U–Pb ages and whole-rock geochemical data for the Carboniferous magmatic rocks in Northeast Mongolia. Zircon U–Pb dating indicates that the Adaatsag dacite, Northern Bayanjargalan gabbro-diorite and Bagannur pluton were emplaced at ca. 325 Ma, ca. 316 Ma, and ca. 305 Ma, respectively. Occurrences of these rocks together constitute a Carboniferous magmatic belt to the northwest of the Middle Gobi volcanic-plutonic belt. The ages of trapped zircon xenocrysts within the Bagannur pluton indicate that the basement of this magmatic belt is the Ereendavaa terrane. Geochemical analysis indicates that these magmatic rocks were formed in an Andean-type active margin, which provides robust evidence for southward subduction of the Mongol-Okhotsk Ocean during the Late Carboniferous. By combining all the available data, we argue that the onset of the Central Mongolia–Tsagaan Uul continental collision during the Late Carboniferous – Early Permian may have triggered the beginning of an active margin of the Mongol-Okhotsk Ocean along the northern coast of the Central Mongolia microcontinent.

Variable Depths of Magma Genesis in the North China Craton and Central Asian Orogenic Belt Inferred From Teleseismic P Wave Attenuation

AbstractEastern Asia is a prime location for the study of intracontinental tectono‐magmatic activity. For instance, the origin of widespread intraplate volcanism has been one of the most debated aspects of East Asian geological activity. Measurements of attenuation of teleseismic phases may provide additional constraints on the source regions of volcanism by sampling the upper mantle. This study uses data from three seismic arrays to constrain lateral variations in teleseismic P wave attenuation beneath the Central Asian Orogenic Belt and the North China Craton. We invert relative observations of attenuation for a 2‐D map of variations in attenuation along with data and model uncertainties by applying a Hierarchical Bayesian method. As expected, low attenuation is observed beneath the Ordos block. High attenuation is observed beneath most of the volcanoes (e.g., the Middle Gobi volcano, the Bus Obo volcano, and the Datong volcano) in the study area, and estimated asthenospheric Qp values span from 95 to 200. These values are within the range of globally average asthenosphere. We infer that these volcanoes may tap melt from ambient asthenosphere and occur where the lithosphere is thin, which is consistent with previous petrologic studies. More complex mantle drivers of volcanism are not rejected but are not needed to explain eruptions in this area. In contrast, at the Xilinhot‐Abaga volcanic site, the observed low attenuation (as low as beneath the Ordos block) excludes a typical shallow melting column. Fluids from the subducted Pacific plate may initiate the deep melting and would be consistent with petrological constraints.

Age, petrogenesis, and tectonic implications of the late Permian magmatic rocks in the Middle Gobi volcanoplutonic Belt, Mongolia

AbstractThe Mongol–Okhotsk Belt, the youngest segment of Central Asian Orogenic Belt, was formed by the evolution and closure of the Mongol–Okhotsk Ocean. The oceanic closure formed two volcanoplutonic belts: Selenge Belt in the north and the Middle Gobi Belt in the south (in present day coordinates). However, the origin and tectonic evolution of the Mongol–Okhotsk Belt in general, and the origin and formation age of the Middle Gobi Belt in particular, remain enigmatic. To better understand the history of the magmatic activity in the Middle Gobi Belt, we conducted geochemical, U–Pb geochronological, zircon Hf, and whole‐rock Nd isotopic analyses of samples from the Mandalgovi volcanoplutonic suite, the major component of the Middle Gobi Belt. Our results show that the plutonic rock consists of ~285 Ma gabbro, ~265 Ma biotite‐granite and ~250 Ma hornblende‐granodiorite. The volcanic counterpart is represented by a Permian Sahalyn gol rhyolite and ~247 Ma Ikh khad andesite. The geochemical compositions of biotite‐granite and hornblende‐granodiorite indicate that their precursors were metagraywacke and amphibolite, respectively. They are characterized by positive whole‐rock εNd(t) and zircon εHf(t) values, indicating juvenile protoliths. The gabbro was derived by partial melting of a metasomatized lithospheric mantle source in a supra‐subduction setting. The biotite‐granite and Sahalyn gol rhyolite are formed by remelting of sediments in an inter‐arc extension setting. Later the hornblende‐granite and Ikh khad volcanic were emplaced at a volcanic arc formed by the subduction of the Mongol–Okhotsk Ocean. We conclude that the magmatic rocks of the Middle Gobi Belt formed in an active continental margin setting. Considering the consistent distribution of coeval arc‐derived magmatic formations along the southern margin of the Mongol–Okhotsk Belt, the oceanic basin was closed in a relatively simultaneous manner.

Pastoralist strategies and human mobility: oxygen (δ18Op) and strontium (87Sr/86Sr) isotopic analysis of early human remains from Egiin Gol and Baga Gazaryn Chuluu, Mongolia

The steppes of Central Asia have long been inhabited by communities practicing various forms of mobile pastoralism as their primary means of subsistence. This study explores the relationship between human mobility and organizational strategies at two distinct micro-regions situated within the modern-day borders of Mongolia. Our investigation was based on an analysis of oxygen (δ18Op) and strontium (87Sr/86Sr) isotopes in archeological human skeletal remains (n = 30) from Baga Gazaryn Chuluu, situated within the middle Gobi Desert and the Egiin Gol Valley in north-central Mongolia. The results indicate a marked degree of separation in local baseline values between the two regions, and corresponding variation was observed in the human skeletal samples. Intra-regional comparisons found that most individuals appear to have spent their childhood years within a “local” range for each particular region, with several notable exceptions that likely indicate a greater degree of lifetime mobility for certain individuals. Overall, the results support the probability that mobility patterns in the past were related to subsistence strategies developed within the discrete environmental zones that characterize the central regions of Mongolia.

Mantle transition zone structure beneath the Central Asian Orogenic Belt

Over the past decades, there have been hot debates in the geodynamic community regarding to the deep evolution mechanisms of Cenozoic volcanism in the Central Asian Orogenic Belt (CAOB). Of all the constraints available, high resolution structure of upper mantle discontinuities, especially the discontinuities at depths of 410 km (D410) and 660 km (D660), is of the most important, which may provide reliable clues on the magma channel as well as its evolution. In this work, we adopt the common conversion point stacking technique with teleseismic radial P-wave receiver functions to examine the D410 and D660 discontinuities. The primary results exhibit that the major characteristics of the mantle transition zone (MTZ) obtained by different velocity models are largely consistent. Obviously elevated D410 and slightly depressed D660 are observed beneath the Hannuoba Volcano, suggesting possible delamination of the local lithosphere deposited at the D410. This process may induce upwelling of the asthenospheric materials filling the space left by the delaminated lithosphere, and subsequently trigger volcanic eruptions. Strong depressions are observed at both D410 and D660 depths beneath west of the Dariganga Volcano, and the depression of D660 is more pronounced. It leads to the apparently thickened MTZ, indicating the presence of cold material at the D660. This cold material is speculated as a stagnant slab from the subducted Pacific Plate or the remains of a detached island arc system from the collision and formation of the CAOB. Slightly thinner MTZ is found beneath the Hentey Mountains and the Middle Gobi Volcano. Apparently, this thinner MTZ is not significant enough to support the existence of high thermal anomalies, which may rule out the possibility of large-scale hot material upwelling from either the local MTZ or even the lower mantle.

Playing at etiquette, learning respect in contemporary Middle Gobi (Mongolia)

Jouer à l’étiquette, apprendre le respect dans le Gobi Moyen contemporain (Mongolie).L’étiquette mongole (yos), héritée du mode de vie pastorale, est une « technologie morale » omniprésente qui ordonne les relations selon les valeurs de respect et de calme. À la fin des années 2000, les enfants du Gobi Moyen grandissent dans un contexte de changements économiques et sociaux qui remettent en question les régimes de valeur traditionnels. Ce texte examine dans quelle mesure, et comment, les enfants s’approprient l’étiquette en soulignant la façon particulière dont la yourte, en tant qu’« espace moral ordonné », joue un rôle important dans l’apprentissage de celle-ci. L’article vise à montrer que l’étiquette est renouvelée, mais qu’elle se reproduit, à chaque nouvelle génération, tout en restant le vecteur de valeurs intergénérationnelles partagées, notamment celles du respect et du calme.

Trends in Livestock Numbers and Spectral Properties of the Pasture Surface: Case Study of the Middle Gobi Aimag of Mongolia

The paper analyzes linear correlations between MODIS parameters, i.e., the albedo, surface temperature, NDVI, and evapotranspiration, and with annual livestock numbers on Mongolian pastures for June–August throughout 2000–2015. The degree of association between the annual livestock density and average spectral properties of pastures were determined at the level of the whole country, region (aimag), and district (sum). Linear trends were assessed in the annual livestock density and spectral properties of the pasture surface within the boundaries of the specified administrative units of Mongolia. The total density and density with consideration for a structure of the livestock population within the stated territories are weakly related to the average spectral parameters of the pasture surfaces for the territories. The exception is Gurvansaikhan district, in which the relationships are significant; an increase in livestock density increases the albedo, decreases NDVI, and eventually reduces the forage reserve. The R2 coefficients of determination reveal insignificant linear trends in albedo, NDVI, and evapotranspiration as opposed to a significant positive trend in livestock density. A cooling trend and decreased precipitation was evident in 2000–2015. In the years of a sharp drop in livestock density (2000 and 2010), the spectral characteristics of pastures exhibit insignificant departures from the trend line, i.e. their sensitivity to a sharp drop in livestock numbers is minimal in the present situation.

Seismic velocity variations beneath central Mongolia: Evidence for upper mantle plumes?

Central Mongolia is marked by wide spread recent volcanism as well as significant topographic relief even though it is far from any plate tectonic boundaries. The cause of the recent magmatism and topography remains uncertain partially because little is known of the underlying mantle seismic structure due to the lack of seismic instrumentation in the region. From August 2011 through August 2013, 69 broadband seismic stations were deployed in central Mongolia. Teleseismic traveltime residuals were measured using waveform correlation and were inverted to image upper mantle P and S velocity variations. Significant lateral variations in seismic velocity are imaged in the deep upper mantle (100 to 800 km depth). Most significant are two continuous slow anomalies from the deep upper mantle to near the surface. One slow feature has been imaged previously and may be a zone of deep upwelling bringing warm mantle to beneath the Hangay Dome resulting in uplift and magmatism including the active Khanuy Gol and Middle Gobi volcanoes. The second, deep low velocity anomaly is seen in the east from 800 to 150 km depth. The anomaly ends beneath the Gobi Desert that is found to have fast shallow mantle indicating a relatively thick lithosphere. We interpret the second deep slow anomaly as a mantle upwelling that is deflected by the thick Gobi Desert lithosphere to surrounding regions such as the Hentay Mountains to the north. The upwellings are a means of feeding warmer than normal asthenospheric mantle over a widely distributed region beneath Mongolia resulting in distributed volcanic activity and uplift. There is no indication that the upwellings are rooted in the deep lower mantle i.e. classic plumes. We speculate the upwellings may be related to deep subduction of the Pacific and Indian plates and are thus plumes anchored in the upper mantle.

Early Paleozoic oceanic inliers and reconstruction of accretionary tectonics in the Middle Gobi region, Mongolia: Evidence from SHRIMP zircon U-Pb dating and geochemistry

The ophiolites that occur as inliers among the Late Paleozoic formations in the Middle Gobi area are crucial for understanding the tectonic evolution of South Mongolia. In this paper, we conducted detailed studies on the Namdain hundy ophiolite to provide some constraints on the Early Paleozoic evolution of the Middle Gobi region in Mongolia. The ophiolite mainly consists of ultramafic rocks (carbonatation), plagiogranite, metagabbro, basalt and chert. The metagabbro and plagiogranite from Namdain hundy ophiolite yielded SHRIMP zircon U-Pb ages of 528±7Ma and 519±5Ma, respectively. Though most of the volcanic rocks of this ophiolite show supra-subduction zone (SSZ) affinity, samples with OIB and N-MORB geochemical features were also identified, indicating genesis in a forearc setting. The granodiorite intruding into the Namdain hundy ophiolite yielded a SHRIMP zircon U-Pb age of 491±3Ma, which constrained the upper age limit of ophiolite emplacement. This granodiorite shows adakitic geochemical affinity, attesting to the existence of Cambrian paleo - subduction in South Mongolia. Based on the available data so far, we suggest the Middle Gobi area comprises of the Manlay accretion complex, the island arc and the Biluutiin ovoo back-arc basin. The spatial configuration of these three tectonic belts suggests that the polarity of the paleo-ocean subduction was from south to north in the Early Paleozoic, forming a trench-arc-basin system south of the Central Mongolia microcontinent.

Kinematics of late Quaternary slip along the Yabrai fault: Implications for Cenozoic tectonics across the Gobi Alashan block, China

The Yabrai range-front fault accommodates deformation within the middle Gobi Alashan block between the Tibetan Plateau and the Ordos block. As such, it provides the opportunity to examine the transition between contractional deformation associated with the growth of the Tibetan Plateau and extensional deformation across North China. Geomorphic mapping of the active fault trace and trench investigations reveal that the Yabrai range-front fault is composed of three segments of varying fault strike, but for which the sense of motion, scarp height, and slip history appear to be kinematically compatible along the fault. Displaced Holocene and late Pleistocene alluvial deposits indicate that the southwestern segment is characterized by oblique-normal displacement with a minor sinistral component, whereas the middle segment appears to exhibit nearly dip-slip normal displacement. In contrast, slip along the northeastern segment appears to be primarily sinistral strike-slip with a minor reverse component. Geomorphically fresh fault scarps are developed within late Pleistocene–Holocene alluvial fans and terraces along the southwestern and northeastern segments, whereas the middle segment of the fault defines the bedrock-alluvial contact along the range front. The 10Be exposure ages of displaced alluvial fans along the southwestern segment yield a throw rate of ∼0.1 mm/yr over late Pleistocene time. Lateral slip rates along the northeastern fault segment range between 0.23 ± 0.02 and 0.78 ± 0.12 mm/yr. Regionally, the orientation and sense of motion along the Yabrai range-front fault are consistent with NE-SW shortening, and we suggest that recent activity along this fault system reflects incipient deformation of the foreland at the northeastern margin of the Tibetan Plateau.

Why are Mongolian Infants Treated Like ‘Kings’?

As infants and toddlers, Mongolian children grow up as the centre of attention in their home, promptly taken care of and tenderly indulged. In this paper, I seek to explain why young children in the middle Gobi enjoy a privileged status, in contrast with their status as older children. I show how the physical, emotional and moral peculiarities of infants’ and toddlers’ personhood converge in conferring upon them ‘kingly’ prerogatives. I then examine what leads to their loss of privileges, as they grow older. Unlike most studies examining the changes of status that children undergo, I do not focus onrites de passage, but analyse daily interactions. The loss of young children’s privileges occurs according to different timelines for each aspect of their personhood, while the prerogatives enjoyed by young children also reoccur at different periods in life, thus inviting us to reconsider what is meant by infancy as a discrete stage.

Late Paleozoic magmatic record of Middle Gobi area, South Mongolia and its implications for tectonic evolution: Evidences from zircon U–Pb dating and geochemistry

Late Paleozoic subduction–accretion complexes occur widely in Middle Gobi area and provide a good opportunity for unraveling the Paleozoic tectonic evolution of South Mongolia. The magmatic rocks in the Tsavchir hudug district mainly consist of rhyolites and volcaniclastic rocks. The rhyolites show enrichment in LREE and LILE and negative Nb, Ta and Ti anomalies, indicating genesis in the subduction zone. A rhyolite sample from the Tsavchir hudug region yielded a SHRIMP 206Pb/238U zircon age of 315±4Ma (MSWD=0.79, n=15). The andesite overlying the Namdain hundy Early Paleozoic ophiolite shows adakite geochemical features, and the two andesite samples yielded SHRIMP 206Pb/238U zircon ages of 325±3Ma (MSWD=1.6, n=14) and 319±4Ma (MSWD=0.56, n=13), respectively, suggesting that the Carboniferous island arc formed on the basis of Early Paleozoic accretionary complex. The granodiorite sample that intrudes the Early Paleozoic accretion complex with adakite geochemical features yielded a SHRIMP 206Pb/238U zircon age of 333±4Ma (MSWD=1.6, n=16), representing the Late Paleozoic island arc intrusive. The SHRIMP U–Pb analyses for the tuff sandstones that occur associated with Early Paleozic oceanic inliers in Middle Gobi area suggest detrital zircons mainly stem from the Devonian–Carboniferous arc. The age data obtained from the ophiolite (528–509Ma) and tuff sandstone indicate the accretion in Middle Gobi area lasted from Early Paleozoic to Late Paleozoic for at least ca. 200Ma, suggesting the ocean of the accretionary complex was the major Paleo-Asain ocean basin. The subduction related magmatic belt in Middle Gobi area includes both Early Paleozoic and Late Paleozoic island arc activities, which is consistent with the accretion duration time obtained from accretionary complex and also attests the argument of major Paleo-Asain ocean basin.

Ambient Noise Tomography in Central‐South Mongolia

AbstractRelying on cooperation projects in Mongolia, “Observation and modeling on the geomagnetic, gravitational field and deep structure in the Far East Areas”, we got dense seismic array data in the area for the first time. By using the vertical component of continuous data, recorded by 69 broadband seismic stations from Aug. 2011 to Jul. 2013 in south‐central Mongolia (103.5°E–111.5° E, 43°N–49°N), we calculated the inter‐station Empirical Green functions (EGFs) from cross‐correlation. In addition, a time‐frequency analysis based on a continuous wavelet transform was used to extract the Rayleigh wave phase velocity dispersion curves. Through quality control and manually screening, we finally obtained a total number of 1478 phase velocity dispersion curves at periods ranging from 6 s to 30 s. The Ditmar & Yanovskaya method was utilized to obtain phase velocity maps of the Rayleigh wave at periods of 6∼30 s in the study area. Checkerboard tests showed that the tomographic results had a high resolution of 0.5° ×0.5°. The results revealed that the phase velocity maps of Rayleigh waves have a small perturbation of about ±2%. A phase velocity map with a short period (e. g. 6 s) was imaged with high‐speed anomalies corresponding to the mountain ranges in the north and low‐speed anomalies coinciding with the sedimentary basin and Gobi Desert in the central‐south region. As the period (15 s, 20 s) increased, the imaging still showed a high‐velocity zone (HVZ) in the north and low‐velocity zone (LVZ) in the central‐south. However, the effect of the phase velocity distribution controlled by the surface geological structure was significantly weaker. The phase velocity maps with a long period (e.g. 30 s) showed an HVZ in the north that expanded further to the south than those with shorter periods (e.g., 15 s and 20 s), which is associated with the thinner crust in the south compared to that in the north. On those maps with long periods (e.g., 20 s, 30 s), there were significant differences between the northern and southern sides of Main Mongolian Lineament (MML), indicating that MML was not only a boundary for the topography and tectonics, but also for the crustal structure. The Middle Gobi area always showed an LVZ at periods from 6 s to 30 s, which could have been related to Cenozoic volcanism, while the Hangay‐Hentey basin was always imaged with an HVZ, which could have been associated with the old, stable layers in the north.

Modern use of pastures and watering security in the Middle Gobi aimak, Mongolia (by example of Rashaant brigade)

The paper presents detailed characteristics of the pastures and the structure of livestock over the last decades in Middle Gobi aimak of Mongolia as an example of Rashaant bug (brigade). The problems of watering places were investigated, and recommendations for optimizing the structure of populations and conservation of ecosystems for the study area were provided.