Mongolian Geoscientist

The Paleozoic Granitic Rocks from the Telmen Complex in the Tarvagatai Block, Central Mongolia: Petrogenesis, U-Pb geochronology, and its tectonic implications

Mon, 03 Apr 2023 00:00:00 +0000

The Tarvagatai Block is located in the northern part of Central Mongolia, which is a widespread occurrence and occupies roughly 60% of the whole exposure along the Khangai fault and the Tarvagatai uplift. Granitic magmatism was emplacement during the Middle Paleozoic, which is predominantly composed of granite-granodiorite and gabbro-diorite and rarely gabbro. This article represents petrographical, geochemical, and U-Pb zircon age data from the Telmen Complex of the Tarvagatai Block, Central Mongolia. The U-Pb dating of zircon yields a Late Silurian emplacement age (419±3 Ma) for the Telmen Complex. Geochemically, the Telmen Complex is an I-type intrusion of metaluminous nature with a SiO₂ content ranging from 53.06 to 72.25 wt.% and mainly of medium to high K calc-alkaline series. Telmen Complex granites show enrichments in light rare earth elements, depletion in heavy rare earth elements, with a ratio of 4.053, (La/Yb)_N =9.15, and weak positive or normal Eu anomalies. A spider diagram indicates that these rocks are enriched in Ba, K, Pb, and Sr and depleted in Nb, Ta, and Ti. The Early Paleozoic Telmen Complex granitics have trace element features, for example, Nb-Ta depletions, which indicate that these rock units were emplaced in a convergent-margin setting and typical of the lower continental crust. In addition, the geochemical data show that the volcanic arc tectonic setting and, moreover, the continental arc array setting display on the Nb/Yb versus TiO₂/Yb diagrams. Therefore, we suggest that they were probably positioned in an active continental setting and in a Silurian ~419 Ma.

Velocity analysis of a lateral wave

Tsogtbaatar Amarsaikhan, Motoyuki Sato — Fri, 09 Jun 2023 00:00:00 +0000

In practice, the reflected EM signal cannot be clearly observed in GPR data due to the high water content and other reasons. However, the antenna coupling signal through the ground interface is dominated in all the GPR measurements. This direct coupling signal that travels through the ground interface is called a lateral wave. The properties of the lateral wave directly depend on the subsurface properties, especially electrical parameters. We have numerically analyzed a lateral wave and its velocity. Subsequently, the relationship between lateral wave and dielectric permittivity was determined by polynomial regression. Analytically, it is challenging to analyze a lateral wave due to the parameters that can influence wave propagation. Antenna characteristics, surface roughness, etc need to be considered. Numerically, we designed a GPR system with a subsurface layer and observed a lateral wave. This numerical analysis can give a chance to use a lateral wave for near-surface soil water content. This analysis gives a more precise estimation of surface water content. Moreover, we analyze the antenna height effect that influences radar signals. We numerically observed that the GPR signal is highly affected by antenna height. The antenna height effect depended on the wavelength of the applied electromagnetic wave. By adjusting the antenna height, the unobservable GPR signal can be clearly detected.

Residual strain investigation of a polycrystalline quartzite rock sample using time-of-flight neutron diffraction

Altangerel Badmaarag, Deleg Sangaa, Vadim V. Sikolenko, Lkhamsuren Enkhtur — Mon, 28 Aug 2023 00:00:00 +0000

In this work, we studied the residual micro lattice strain of an onyx sample, which is a micro- to the cryptocrystalline variety of the mineral quartz SiO₂. That the investigation has been carried out using in-situ stress experiments with the time-of-flight neutron diffraction method. The aim of the study is to investigate residual lattice strains and pressure directions in the sample using time-of-flight neutron diffraction, which is a powerful tool for the study of the residual strain behavior in bulk materials, like geological rock samples containing large grains. The residual strain was detected in different sample directions turning the sample in steps of 30° by 180° around the cylindrical z-axis. These experiments have been performed at the time-of-flight neutron strain diffractometer EPSILON, situated on the pulsed neutron source IBR-2M of the Joint Institute for Nuclear Research in Dubna, Russia. The results of this study will provide insights into the compressional and tensional residual strain of the crystallographic lattice planes, and will have implications for our understanding of the tectonic history of this region. These different strains are arranged in the sample by a sinusoidal distribution in radial directions.

The heat flow losing via earth's surface around of Khulj hot spring

Shoovdor Tserendug, Bayanjargal Genden, Tumen Nasan-Ochir, Tsoodol Zolbadral — Wed, 20 Sep 2023 00:00:00 +0000

In this paper, we extracted values of geomagnetic anomaly sourced in the lithosphere from the total intensity of geomagnetic that is measured on the 750 points on an area (100x100 km²) around the Khulj hot springs. The two-dimensional map of the distribution of the anomaly geomagnetic corresponding to this area was made via these extracted values of anomaly geomagnetic. The method of spectral analysis was used to estimate the Curie Point Depth, which is lost magnetic characteristics of the lithosphere with a temperature of 580^o C and the depth of layer sourcing anomaly geomagnetic with high content of iron, nickel, and tungsten by these values of geomagnetic anomaly. On the Fig. 5, the isothermal Curie surface with the temperature of 580^o C was visualized in three dimensions by these values of Curie Point Depth. The heat flows lost on Earth’s surface was also detected by the method of the gradient of temperature from the Curie Point Depth. And the two-dimensional map of heat flow around the Khulj hot spring was illustrated by the values of heat flows. Moreover, the average value of the heat flow for whole the area (100x100 km²) was about 60[mW/м²], and it was estimated at about 70[mW/м²], at the Khulj hot springs. When we carried out a same study near Ulaanbaatar in 2018, the average heat flows lost on Earth’s surface was determined about 40-50[mW/м²].