First Results and Prospects of a New Approach to the Study of Active Geologic Processes by Space and Ground Instrumental Measurements (by the Example of Kamchatka and the Central Asian Orogenic Belt)

2021 ◽  
Vol 62 (1) ◽  
pp. 44-67
Author(s):  
N.L. Dobretsov ◽  
M.M. Buslov ◽  
A.N. Vasilevskiy ◽  
S.M. Zhmodik ◽  
A.V. Kotlyarov
Keyword(s):  
Satellite Images ◽  
Gravity Anomalies ◽  
3D Models ◽  
Tien Shan ◽  
Magma Chambers ◽  
Tectonic Structures ◽  
Central Asian ◽  
Geological Information ◽  
First Results ◽  
Geologic Processes

Abstract ––The use of satellite-geological information permits generalization of studies of various active geologic processes in a new way. As reference examples, we consider geologic regions extensively covered by research with our contribution. The joint use of satellite images, maps of gravity anomalies, and seismic-tomography data for Kamchatka made it possible to construct 3D models of surficial and deep-seated (depths from 10–50 to 650 km) volcanic structures. For young volcanosedimentary structures of Kamchatka, it is possible to trace the interaction of various processes, from crystallization of magmas in magma chambers to ore and oil formation in calderas. Ancient tectonic structures and superposed Cenozoic deformations in the Tien Shan, Altai, and Baikal regions are clearly displayed in satellite images and on maps of gravity anomalies. The long-range impact of the Indo-Eurasian collision on the Tien Shan, Altai, and Baikal regions was expressed as shearing, which resulted in the most contrasting structures in the zones of junction of regional faults and along the framing of cratonal structures. The active structures of Gorny Altai contain numerous travertines, whose abundance is correlated with seismic activity. The mass formation of methane and gas hydrates in Lake Baikal might be related to mantle plume fluids.

FIRST RESULTS FROM TIEN-SHAN SURVEY TO SEARCH FOR VARIABLE STARS: LIGHTCURVE ANALYSIS AND VARIABLE STAR CLASSIFICATION

2020 ◽  
Vol 3 (331) ◽  
pp. 81-91
Author(s):  
Serebryanskiy A., ◽  
◽  
Aimanova G. K., ◽  
Kondratyeva L.N., ◽  
Omarov Ch., ◽  
...  
Keyword(s):  
Variable Star ◽  
Variable Stars ◽  
Tien Shan ◽  
First Results ◽  
Star Classification

BAYESIAN MAGNETOTELLURIC INVERSION USING METHYLENE BLUE STRUCTURAL PRIORS FOR IMAGING SHALLOW CONDUCTORS IN GEOTHERMAL FIELDS

Geophysics ◽  
2021 ◽  
pp. 1-66
Author(s):  
Alberto Ardid ◽  
David Dempsey ◽  
Edward Bertrand ◽  
Fabian Sepulveda ◽  
Flora Solon ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Clay Content ◽  
3D Models ◽  
Bayesian Inversion ◽  
Inversion Method ◽  
Geothermal Fields ◽  
Geological Information ◽  
Resistivity Model ◽  
Irreducible Uncertainty ◽  
Clay Cap

In geothermal exploration, magnetotelluric (MT) data and inversion models are commonly used to image shallow conductors typically associated with the presence of an electrically conductive clay cap that overlies the main reservoir. However, these inversion models suffer from non-uniqueness and uncertainty, and the inclusion of useful geological information is still limited. We develop a Bayesian inversion method that integrates the electrical resistivity distribution from MT surveys with borehole methylene blue data (MeB), an indicator of conductive clay content. MeB data is used to inform structural priors for the MT Bayesian inversion that focus on inferring with uncertainty the shallow conductor boundary in geothermal fields. By incorporating borehole information, our inversion reduces non-uniqueness and then explicitly represents the irreducible uncertainty as estimated depth intervals for the conductor boundary. We use Markov chain Monte Carlo (McMC) and a one-dimensional three-layer resistivity model to accelerate the Bayesian inversion of the MT signal beneath each station. Then, inferred conductor boundary distributions are interpolated to construct pseudo-2D/3D models of the uncertain conductor geometry. We compared our approach against a deterministic MT inversion software on synthetic and field examples and showed good performance in estimating the depth to the bottom of the conductor, a valuable target in geothermal reservoir exploration.

Three-dimensional gravity modelling applied to the exploration of uranium unconformity-related basement-hosted deposits: the Contact prospect case study, Kiggavik, northeast Thelon region (Nunavut, Canada)

2017 ◽  
Vol 54 (8) ◽  
pp. 869-882 ◽  
Author(s):  
Régis Roy ◽  
Antonio Benedicto ◽  
Alexis Grare ◽  
Mickaël Béhaegel ◽  
Yoann Richard ◽  
...  
Keyword(s):  
Gravity Data ◽  
Three Dimensional ◽  
Gravity Anomalies ◽  
3D Models ◽  
Low Density ◽  
Uranium Deposits ◽  
Geological Interpretation ◽  
Thelon Basin ◽  
Dimensional Gravity ◽  
Density Values

In unconformity-related uranium deposits, mineralization is associated with hydrothermal clay-rich alteration haloes that decrease the density of the host rock. In the Kiggavik uranium project, located in the eastern Thelon Basin, Nunavut (Canada), basement-hosted shallow deposits were discovered by drilling geophysical anomalies in the 1970s. In 2014, gravity data were inverted for the first time using the Geosoft VOXI Earth ModellingTM system to generate three-dimensional (3D) models to assist exploration in the Contact prospect, the most recent discovery at Kiggavik. A 3D unconstrained inversion model was calculated before drilling, and a model constrained by petrophysical data was computed after drilling. The unconstrained inversion provided a first approximation of the geometry and depth of a low-density body and helped to collar the discovery holes of the Contact mineralization. The constrained inversion was computed using density values measured on 315 core samples collected from 21 drill holes completed between 2014 and 2015. The constrained modelling highlights three shallower and smaller low-density bodies that match the geological interpretation and refines the footprint of the gravity anomalies in relation to the current understanding of the deposit. The 3D inversion of gravity data is a valuable tool to guide geologists in exploration of shallow basement-hosted uranium deposits associated with alteration haloes and to assess the deposit gravity geometry.

Different causes of the delamination on the example of Caucasus and Kyrgyz Tien Shan collision zones.

2020 ◽  
Author(s):  
Irina Medved ◽  
Ivan Koulakov ◽  
Mikhail Buslov
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
3D Models ◽  
Tien Shan ◽  
Gradual Transition ◽  
Mantle Lithosphere ◽  
Continental Lithosphere ◽  
Low Velocity ◽  
Mountain Areas ◽  
Velocity Anomalies

<p>The causes of delamination of the mantle lithosphere in collision zones is actively debated in the scientific community. The main discussions are focused on the initiation of sinking of the continental lithosphere into the asthenosphere to a depth. Most scientists believe that such kind of immersion is impossible. However, there are several articles showing that this process is nonetheless taking place. For example Kay and Kay, (1993), Faccenda, Minelli, Gerya, (2009), Ueda et. al., (2012) and others propose various mechanisms of delamination, for example: eclogitization of the mafic layer of the lower crust, the effect of convection in the upper mantle, or gradual transition of the oceanic subduction into continental collision. Does the mantle part of the lithosphere sink into the mantle or spread laterally, as described in [for example, Deep Geodynamics, 2001; Bird, 1991; Schmeling and Marquart, 1991]?</p><p>To answer these questions, we study deep structures beneath the Caucasus and Kyrgyz Tien Shan collision zones. The studies were carried out on the basis of multiscale seismic tomography methods: regional and global. This approach made it possible to study heterogeneities both in the crust and in the upper mantle. The obtained 3D models of seismic heteroheneities reveal similar features for the both collision regions. Beneath the mountain areas, in the uppermost mantle and lower crust, we observe prominent low-velocity anomalies that possibly indicate thickening of the crust and missing (or strongly thinned) mantle part of the lithosphere. At the edges of the collision zones, we reveal inclined high-velocity anomalies appearing as continuations of the continental plates sinking underneath the collision zones, which can be interpreted as delaminating mantle parts of the continental lithosphere.  Based on joint consideration of the tomography models with the existing models of tectonic evolution, we conclude that the mechanisms of delamination in the considered two regions are different. In Caucasus, the delamination could be gradually transformed from oceanic subduction that ended here approximately ~10-15 Ma. In the case of Tien Shan, the detachment of the mantle lithosphere could be triggered by the plume that existed beneath Central Tien Shan or by the eclogitization of the mafic layer of the lower crust.</p>

scholarly journals Geological evolution of Central Asian Basins and the western Tien Shan Range

2017 ◽  
Vol 427 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Marie-Françoise Brunet ◽  
Edward R. Sobel ◽  
Tom McCann
Keyword(s):  
Tien Shan ◽  
Central Asian ◽  
Geological Evolution

scholarly journals Runoff modelling in glacierized Central Asian catchments for present-day and future climate

2006 ◽  
Vol 37 (2) ◽  
pp. 93-105 ◽  
Author(s):  
W. Hagg ◽  
L.N. Braun ◽  
M. Weber ◽  
M. Becht
Keyword(s):  
Tien Shan ◽  
Water Shortages ◽  
Time Step ◽  
Climate Conditions ◽  
Central Asian ◽  
Complex Picture ◽  
Daily Time Step ◽  
The Alps ◽  
High Degree ◽  
Tien Shan Mountains

A conceptual precipitation–runoff model was applied in five glacierized catchments in Central Asia. The model, which was first developed and applied in the Alps, works on a daily time step and yields good results in the more continental climate of the Tien Shan mountains for present-day climate conditions. Runoff scenarios for different climates (doubling of CO2) and glacierization conditions predict an increased flood risk as a first stage and a more complex picture after a complete glacier loss: a higher discharge during spring due to an earlier and more intense snowmelt is followed by a water deficiency in hot and dry summer periods. This unfavourable seasonal redistribution of the water supply has dramatic consequences for the Central Asian lowlands, which depend to a high degree on the glacier melt water for irrigation and already nowadays suffer from water shortages.

scholarly journals Geometry of the inverted Cretaceous Chañarcillo Basin based on 2-D gravity and field data. An approach to the structure of the western Central Andes of northern Chile

2015 ◽  
Vol 7 (3) ◽  
pp. 2311-2346
Author(s):  
F. Martínez ◽  
A. Maksymowicz ◽  
H. Ochoa ◽  
D. Díaz
Keyword(s):  
Normal Fault ◽  
Gravity Anomalies ◽  
Integrated Approach ◽  
Central Andes ◽  
Fault System ◽  
Northern Chile ◽  
Gravity Gradients ◽  
Structural Geometry ◽  
Geological Information ◽  
New Ideas

Abstract. This paper discusses an integrated approach that provides new ideas about the structural geometry of the NNE-striking, Cretaceous Chañarcillo Basin located along the eastern Coastal Cordillera in the western Central Andes of northern Chile (27–28° S). The results obtained from the integration of two transverse (E–W) gravity profiles with previous geological information, show that the architecture of this basin is defined by a large NNE–SSE-trending and east-vergent anticline ("Tierra Amarilla Anticlinorium"), which is related to the positive reactivation of a former Cretaceous normal fault (Elisa de Bordos Master Fault). Moreover, intercalations of high and low gravity anomalies and steep gravity gradients reveal a set of buried, west-tilted half-grabens associated with a synthetic normal fault pattern. These results, together with the uplift and folding style of the Cretaceous syn-rift recognized within the basin, suggest that their complete structural geometry could be explained by an inverted fault system linked to the shortening of pre-existing Cretaceous normal fault systems. Ages of the synorogenic deposits exposed unconformably over the frontal limb of the Tierra Amarilla Anticlinorium confirm a Late Cretaceous age for the Andean deformation and tectonic inversion of the basin.

scholarly journals Three new species of Scythrididae from the northern Tien-Shan Mountains (Lepidoptera: Scythrididae)

2019 ◽  
Vol 22 (2) ◽  
pp. 121-128
Author(s):  
Kari Nupponen ◽  
Sergey Yu. Sinev
Keyword(s):  
New Species ◽  
Tien Shan ◽  
Single Female ◽  
Central Asian ◽  
Unknown Species ◽  
The Family ◽  
Three New Species ◽  
Tien Shan Mountains ◽  
Northern Tien Shan

Three new species of the family Scythrididae are described from Central Asian mountains: Scythris cultelloides Nupponen & Sinev, sp. n., S. danilevskyi Nupponen & Sinev, sp. n. and S. ganesha Nupponen & Sinev, sp. n. One unknown species is reported but not formally described because only a single female is available.

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