Geological region by multi-signal method of gravity anomaly data in central Vietnam area

This paper presents the research results of applying the combined method of probabilistic statistical approaches, energy density spectral correlation, two-dimensional filtering in dynamic sliding windows, full horizontal gradient and heterogeneous axis tracking method to process and interpret the Bughe gravitational anomaly field in central area Vietnam. The calculation results have shown the superiority of the twodimensional filter in dynamic sliding windows compared to the filters in fixed windows in GEOSOFT software, GMT software. According to the physical characteristics of the field, the study area was divided into 13 homogeneous classes, this result is consistent with the geological-tectonic data in the area. In the north and northeast, the stabilized rock layers are characterized by homogeneous layers that extend in the northwestsoutheast direction. In the south and southwest, there is complex tectonic activity characterized by high density rock layers overlain by low density rock layers in each fault band with different directions of development. This suggests that there may be deeply buried mineral deposits of magmatic origin in central area Vietnam.

Developing a method to assess risks and unsafety in drilling - blasting activities at limestone quarries in Lao PDR

Currently, the demand for stone construction materials in Lao PDR to serve industrial and traffic works is very large. Currently, the management of mining activities at limestone quarries in Lao PDR is facing many difficulties due to the existence of many types of mines, mining technologies, and equipment. The occupational safety and environmental protection used at the limestone quarries have not been paid due attention. The loss and waste of natural resources are increasing. In particular, labor accidents caused by unsafe drilling and blasting activities often occur at the limestone quarries of construction materials in all provinces of this country. The article analysed the current situation of drilling and blasting activities at the limestone quarries of construction materials of Lao PDR, thereby proposed a method to assess risks and unsafety in drilling and blasting activities at the limestone quarries for mining the construction materials to improve the efficiency of the mining management and safety in Lao PDR.

Research on the influence of bubble curtains on shock wave fields of the underwater explosion

Shock waves, which derive from explosions, generate reflected and refracted waves when propagating in the layered medium with various acoustic stiffness. Depending on the acoustic characteristic of each layer of the medium, properties of reflected and refracted waves will increase or decrease pressures/stresses at the investigated point of medium, compared to influences of explosive shock waves (incident waves) propagated in a homogeneous and isotropic medium. Based on this mechanical physical property, scientists have studied a diversity of solutions decreasing effects of explosive shock waves in various medium such as rock and soil, water, air. However, currently there have not been any comprehensive theoretical studies on the reduction in intensity of the underwater explosion shock wave when interacting with bubble curtain. By using the analytical method and the virtual explosive method, the paper presents the propagation rule of new waves formed when the underwater explosion shock wave interacts with the bubble curtain. The results showed that the more the thickness of the bubble curtain or the higher the bubble content or the longer the distance from the explosive to the curtain, the weaker the intensity of the shock wave when passing through the curtain.

Relationship between urban heat island and population density of districts in Ho Chi Minh City derived from Sentinel - 3 SLSTR data

The urban heat island occurs due to the causes of the urbanization process, of which the main reason is an increase in population density leading to the changes in artificial objects on the ground surface. Recently, using the Split - Window algorithm for two thermal infrared spectral channels with wavelengths of 11 µm and 12 µm to calculate the daily surface temperature with two times of day and night serves to determine the change of land surface temperature. This method is intended to improve the reliability of the results and high technical efficiency. This study uses Sentinel - 3 SLSTR data to determine urban heat island in the districts of Ho Chi Minh City compared to areas bordering the city on May 15th 2020. In addition, population density is calculated according to the results of the census in 2020. The linear relationship between the urban heat island and population density was built with the coefficient of determination R2=0.64.

Cr - spinel and clinopyroxene compositions from metagabbro of Nui Ngoc complex in Tam Ky area: evidence of island - arc magma

The hornblende and biotite - bearing metagabbro of the Nui Ngoc complex were exposed into a few small blocks in the southwest Tam Ky city and were viewed as parts of the Tam Ky - Phuoc Son ophiolitic complex (TPO). These rocks were undergone mylonitic deformation and metamorphism. The rocks consist mainly of orthopyroxene, clinopyroxene, plagioclase, olivine, hornblende, biotite and very few microscopic Cr - spinel. The clinopyroxene and Cr - spinel minerals were analyzed for their composition by EPMA, the results showed that: (1) The clinopyroxenes have low Al2O3 (3,2÷3,5 wt %), TiO2 (0,70÷0,82 wt %) contents and (2) the Cr - spinels have low TiO2 (0,23÷0,58 wt %) content and Mg#100* (Mg/ (Mg+Fe2+)) (32÷42) but has medium Cr# (Cr/ (Cr+Al)) (45÷52).These features are similar to those of rocks formed in anoceanic - oceanicsubduction zone that was reported for the plagiogranite of Dieng Bong complex nearby. This study results combined with previous research results in the Tam Ky - Phuoc Son suture zone show the existence of island arc, continental arc, and MOR - magmatic types.

Variation of sediment provenance at the 09 - 1 Block, Cuu Long Basin: their significance in assessing the Oligocene - Miocene reservoir quality

The Cuu Long Basin is one of the Tertiary sedimentary basins situated on the continental shelf of Vietnam, which demonstrates the high potential of oil and gas. Apart from fractured granite reservoirs, the Oligocene - Miocene sand bodies are thought to have significant potential for forming non - structural traps. The results of the study on the composition and physical properties of the sediments derived from wells "X" and "Y", block 09 - 1, Cuu Long Basin show that there is a clear difference between the Late Oligocene and Early Miocene sandstone in the well "X", namely the Miocene sandstone shows larger particle size, higher roundness and sortness (TB: 434.2; Ro: 0.69; So: 2.22) than those of the Late Oligocene sandstone (TB: 104.28; Ro: 0.64; So: 1.46). This difference is likely attributed to the fact that the Miocene sandstone was influenced by the marine environment, which intensified the roundness and sortness. Meanwhile, the well "Y" did not show much difference in the physical parameters of the sediments between the Late Oligocene and Early Miocene age ranges. However, the grain size was slightly increased and the roundness was less during the Early Miocene. It is possible that the “Y” well is located closer to the local source. The variation in the physical parameters of the sediments, proportion of sand grains and clay minerals shows that the quality of late Oligocene reservoir is better than that of Early Miocene reservoir, and the Late Oligocene reservoir quality in the "X" well is better than that in the borehole "Y".

Assessment of natural irradiation doses in rare earth mines of Muong Hum, Bat Xat district, Lao Cai province

The rare earth mine containing high concentrations of natural radionuclides (238U, 232Th, and 40K) in Muong Hum commune, Nam Pung, Bat Xat district, Lao Cai province, a mine with large reserves of rare earth resources in Vietnam, will be exploited and processed in the near future. The activity of natural radionuclides in the environment of air, soil, water, and effective annual dose are important parameters in assessing the impact of radiation on the environment when the mine goes into operating and processing rare earth ore. Investigating and determining radioactivity in soil, water, and plants at Muong Hum rare earth mine by means of radioactive gas measurement (RAD-7), gamma radiation dose rate (DKS-96), sample analysis using an ICP-MS mass spectrometer, will be performed in this study. The results showed that some soil samples had radionuclides activity 238U, 232Th higher than the allowed standard. The annual effective dose value in the region is 6.1 times higher than the world average (2.4 mSv/year). The obtained results are the basis for monitoring the impact of the radioactive environment and providing solutions to minimize the effects of radioactive substances on the ecological environment when the mine goes into mining and processing of rare earth ores.

Geochemical - geology characteristics implicating original sources and copper - deposit type in Kon Ra ore - field

Based on the research results on petrographic - mineralogical characteristics, tectonic structural features, geochemistry of major and trace elements of the bedrock, alternative rock, ore, soil, mineralogical geochemistry, mineral facies, inclusions, the origin of ore formation related to oxidized granite and skarnoid - typed metasomatic process in Kon Ra copper ore field have been identified. Petrological and mineral characteristics indicate the process of transitional metasomatism between the skarn and hornfels, also known as bimetasomatic stage (skarnoid deposit type). Diopxite represents the Progade skarnoid stage. Tremolite, actinolite, quartz, chlorite, magnetite, molybdenite, less of chalcopyrite, pyrrhotite, and pyrite indicate the retrogade skarnoid stage. The following is sulfide - quartz stage (major minerals include: quartz, chalcopyrite, pyrite, pyrrhotite, molybdenite). This result is also consistent with the formation temperature 210÷270 0C and the geochemical zoning of elements from intrusive blocks through the outer contact zone that contains the ore and surrounding rocks are as follows: Cu, Zn, Ca (the zone has lime-rich formations), Fe3+, Mo increases in the outer contact zone containing ore closed to acid intrusive rocks. Inversely, the ratios of Pb/Cu, Zn/Cu, and As content increased in the alteration from this zone to the outer one. In addition, uranium mineralization is associated with a later magma stage (pegmatite granite in endo-contact is high uranium radiation: U = 0.17÷0.2%, 3,420,000÷8,020,000 µR/h and contains uraninite).

Applied seismic attribte to study the distribution of sandstone reservoirs of D sequence, upper Oligocene sediments, CT field, Cuu Long basin

In this paper, the seismic attribute analysis methods in combination with well data were used to predict the distribution of the D sequence. A seismic attribute is any measurement of seismic data that enhances the visibility or quantification of geological elements or rock properties to determine the structure or depositional environment of sediment. The authors have selected the basic attributes, which are related to amplitude and frequency such as RAI, RMS, ARC length, Specdecom, Sweetness attribute. The attributes reflect quite accurately the changes in lithology, sedimentary facies, etc. from which will be possible to predict the distribution of the sand bodies. There are 02 large reservoirs discovered in the D sequence: the main reservoirs (D0 -D3) sands and minor reservoirs (D4 - D10). The study results show that the main reservoirs from D0 to D3 are widely distributed in the study area, especially in the western block and near the Con Son swell (except A well due to erosion process). Meanwhile, the reservoirs from D4 to D10 are of discontinuous distributions. Zones of high amplitude anomalies that are likely related to volcanic sediments in the study area are also delineated. The seismic attribute analysis reveals the possible distribution of high potential sand bodies (D2-D3) in the south-western and north-eastern parts that need further study.

Research on determining the safe mining depth in special geological conditions of Mong Duong coal mine

The displacement and deformation of strata due to underground mining is one of the factors that negatively affect the safety of production activities. The strata displacement and deformation depend on many factors such as mining geological conditions, safe mining depths, and mining technologies. The determination of the safe depths is important for calculating the size of safety pillars to minimize mineral loss. To date, there have been many studies to determine safe mining depths under normal geological conditions. However, not much research has been conducted to determine safe mining depths with special geological conditions such as many folds, breaks, faults, and under water-bearing objects. This research introduces a method to determine the safe mining depths for the reservoir set in special geological conditions with folds and excavating several seams under water bodies. The proposed method employs the principle of the similar geological zone theory to calculate the safe mining depths. The method is applied to the Mong Duong coal mine, with three coal seams numbered 5, 6, and 7 with the depth of 210, 180, and 136 m, respectively. The results of mining depths safe obtained H5= 240m, H6 =192m, H7= 136m, respectively.