Geochemistry and geochronology of granitoid rocks of the Taatsiin Gol pluton of the Khangai Complex, Central Mongolia

The Taatsiin Gol pluton is one of the major constitute the intrusive body of the Khangai Complex, and is composed the first phase of diorite, the second phase of porphyritic granite, biotite-hornblende granite, and granodiorite, and the third phase of biotite granite and alkali granite. This paper presents new geochemical and U-Pb zircon age data from intrusive rocks of the Taatsiin Gol pluton. Geochemical analyses show that the granitoid rocks of the pluton are high-K calc-alkaline, and metaluminous to weakly peraluminous I-type granites, depleted in HFSE such as Nb, Ta, Ti and Y and enriched in LILE such as Rb, Cs, Th, K and LREE, where some variations from early to later phases rock. Zircon U-Pb dating on the biotite granite of the third phase yielded weighted mean ages of 241.4±1.2 Ma and 236.7±1.4 Ma. Based on the new and previous researchers’ age results, the age of the Taatsiin Gol pluton of the Khangai Complex is 256-230 Ma consistent with the late Permian to mid-Triassic time. Although showing variated geochemical features, the rocks of the three phases are all suggested to form at an active continental margin setting, probably related to the southwestward subduction of the Mongol-Okhotsk Ocean plate during the late Permian to mid-Triassic period.

Remains of the Baikal yak (Poehpagus mutus baikalensis N. Verestchagin, 1954) from Late Pleistocene localities of Southern Siberia

136 bones of the postcranial skeleton and a part of the skull of a female Baikal yak (Poephagus mutus baikalensis N. Verestcthagin, 1954), originating from 18 cave locations and open-type Paleolithic sites in Altai-Sayan, Transbaikalia and Central Mongolia were examined. The material includes 38 metacarpals and 9 metatarsals of the yak. Morphometric differences in the structure of the postcranial skeleton of the yak and the bison (Bison priscus Bojanus, 1827) were revealed. The body size of the Baikal yak significantly exceeded that of the wild Tibetan yak (Poephagus mutus Przewalski, 1883). The largest representatives of P. m. baikalensis inhabited the Altai Mountains. In most of the sites, located in the mid-mountain landscapes of Southern Siberia (with absolute heights of 500–700 m), only a few remains of the Baikal yak were found, accounting for 0.01% to 1–2% of the number of megafauna remains. Most likely, herds of yaks did not live here permanently, but appeared only sporadically, during seasonal migrations. In higher mountainous areas (from 1000–1500 m) of Gorny Altai and Khangai Mountains in Central Mongolia, the proportion of the remains of the Baikal yak increases significantly – up to 16–22%. Like the contemporary P. mutus, the Pleistocene yak found its ecological optimum in the high-mountainous parts of ridges and mountain plateaus, dominated by cold, dry mountain-steppe landscapes with herb-grass vegetation and a small amount of snow. During the periods of cryochrones, the area of P. m. baikalensis apparently expanded significantly, incorporating the adjacent foothill territories. During the periods of thermochrones, it was most likely limited to the high-mountainous areas of the mountain uplifts of Southern Siberia.

First structural observation around the hinge of the Mongolian Orocline (Central Asia): Implications for the geodynamics of oroclinal bending and the evolution of the Mongol-Okhotsk Ocean

To understand the origin of curved subduction zones has been one of the major challenges in plate tectonics. The Mongol-Okhotsk Orogen in Central Asia is characterized by the development of a U-shaped oroclinal structure that was accompanied by the continuous subduction of the Mongol-Okhotsk oceanic plate. Therefore, it provides a natural laboratory to understand why and how a subduction system became tightly curved. In this study, we provide the first structural observation around the hinge of the Mongolian Orocline (the Zag zone in Central Mongolia), with an aim to constrain the oroclinal geometry and to link hinge zone structures with the origin of the orocline. Our results show that rocks in the Zag zone are characterized by the occurrence of a penetrative foliation that is commonly subparallel to bedding. Both bedding and dominant fabric in the Zag zone are steeply dipping, and their strike orientations in a map view follow a simple curve around the hinge of the Mongolian Orocline, thus providing the first structural constraint for 3D geometry of the orocline. A secondary penetrative fabric parallel to the axial plane of the orocline was not observed, indicating a low degree of orogen-parallel shortening during oroclinal bending. Combining with available geological and geophysical data, we conclude that the Mongolian Orocline was developed in a period of Permian to Jurassic, and its origin was linked to the subduction of the Mongol-Okhotsk oceanic slab. We consider that the low-strain oroclinal bending likely resulted from the along-strike variation in trench retreat, which was either triggered by the negative buoyancy of the Mongol-Okhotsk oceanic slab, or driven by the relative rotation of the Siberian and North China cratons. Our results shed a light on 3D geometry and geodynamic mechanisms of large-scale oroclinal bending in an accretionary orogen.

Prospects for the development of geothermal energy supply

The paper addresses methodological and technological issues of building environmentally friendly and efficient energy supply based on geothermal energy sources. Geothermal potential in the world, accentuating that in Russia (areas of the Baikal natural territory) and Mongolia, is analyzed considering the possibility of its implementation in the thermal power industry. Geothermal areas of Central Mongolia are characterized by increased heat flows and occurrences of thermal waters. The most promising thermal spring occurrences are the Shivert, Shargalzhuut, Tsenkher, Otgontenger, and Khuzhirt, to name some of them. Currently, the thermal energy potential of the Khangai arched uplift in Central Mongolia is employed to heat industrial, agricultural, and civil facilities. There are also plans to consider the possibility of large-scale employment of thermal waters of the region for electricity generation. An example of using geothermal waters for electricity generation is given, and the possibility of establishing a heating system in the city of Tsetserleg based on a geothermal heat pump unit with a wind power plant is assessed.

Updated Checklist of Vascular Plants Endemic to Mongolia

The aim of the present study is to update the checklist of vascular plants endemic to Mongolia using previous checklists, publications, herbarium collections, and field observations. The revised checklist includes 102 endemic taxa (95 species, five subspecies, and two nothospecies) from 43 genera and 19 families. The majority of endemic taxa were distributed in western and central Mongolia, and high endemic species richness was identified in four phytogeographical regions, namely Mongolian Altai, Khangai, Dzungarian Gobi, and Gobi Altai, which harbor 49, 27, 20, and 16 endemic taxa, respectively. For each endemic taxon, we compiled information about growth form, conservation status (if already assessed), phytogeographical distribution, and voucher specimens. Data on each taxon’s type specimen were also collected, and the majority of the type specimens were accessioned at the LE (58 taxa), MW (20 taxa), and UBA (7 taxa) herbaria.

Fault Activation in Central Mongolia during the Holocene: Results of Study of the Mogod Earthquake Ruptures

—In order to determine the seismotectonic activity of faults in the Holocene, we performed trench studies of the ruptures produced by the catastrophic Mogod earthquake (5 January 1967, M = 7.5–7.8, I0 = 9–10) in the junction zone of the N–S striking Hulzhin Gol fault and the NW striking Tullet fault. Paleoseismic interpretation of seismic-deformation sections and radiocarbon dating of the samples allowed determining the kinematics and obtaining, for the first time, the absolute ages of paleoevents preceding the Mogod earthquake. Analysis of the tectonic conditions for realization of earthquake sources has shed light on the complex structure of ruptures in the area of the Mogod earthquake epicenter, within which three segments differing in the displacement amplitudes and kinematics have been identified. The research data indicate the repeated activation of the Tulet and Hulzhin Gol faults in the Late Pleistocene–Holocene. The absolute age of the latest activation is 596–994 AD for the Tulet fault and 11,379–6235 BC for the Hulzhin Gol fault. The cumulative deformation from paleoearthquakes in the trench sections in the Tulet fault zone points to at least two displacements of thrust kinematics, with the latest of them having an amplitude of 2.8 m. The paleoearthquake in the Hulzhin Gol fault zone is characterized by the presence of lateral slip. The amplitudes of deformations attest to earlier earthquakes similar in energy to the 1967 Mogod event or even stronger in the fault node. The obtained data on the timing of these earthquakes and the amplitudes of the accompanying displacements made it possible to estimate slip rates along the faults: 0.2–0.3 m/kyr horizontal-slip rates on the Hulzhin Gol fault and 0.5–0.7 m/kyr vertical-slip rates on the Tulet fault.