Conceptual model of a lens in the upper crust (Northern Tien Shan case study)

2020 ◽  
pp. 277-310
Author(s):  
Viacheslav V. Spichak
Keyword(s):  
Conceptual Model ◽  
Tien Shan ◽  
Upper Crust ◽  
Northern Tien Shan

Conceptual model of a lens in the upper crust determined from joint analysis of petrophysical models (Northern Tien Shan case study)

2020 ◽  
Author(s):  
Viacheslav Spichak ◽  
Alexandra Goidina
Keyword(s):  
Electrical Conductivity ◽  
Conceptual Model ◽  
Supercritical Fluids ◽  
Tien Shan ◽  
Joint Analysis ◽  
Integrated Analysis ◽  
High Porosity ◽  
High Electrical Conductivity ◽  
Fluid Saturation ◽  
Northern Tien Shan

<p>A lens having a diameter of about 40 km and a thickness of 10 km was determined at depths 14-22 km in the junction of the Kyrgyz Range and the Chu Basin Depression Trough of the Northern Tien Shan area by 3D seismic tomography carried out earlier. The following questions are still unanswered: </p><p>- what are its petrophysical characteristics?</p><p>- what is the nature of the geophysical anomalies?</p><p>- what is the mechanism of its formation?</p><p>- how long does it exist within their present boundaries?</p><p>In order to address these key issues, it is insufficient to analyze the depth behavior of the P-waves velocities as it was done before. To this end we have built additionally the electrical resistivity, density, lithotypes, temperature, porosity, and fluid saturation models along the N-S collocated seismic and magnetotelluric profile intersecting the study area.</p><p>Their integrated analysis enabled to propose a conceptual model of a lens in the Earth’s crust which answers the questions enumerated above.  In particular, it was determined that the lens is characterized by low V<sub>P</sub> and V<sub>S</sub> velocities and their ratio V<sub>P </sub>/ V<sub>S</sub>;  low resistivity (3–30 Ω.m); low density (at most 2.45 g/cm<sup>3</sup>); high porosity (above 1.2%) and fluid saturation (above 0.1%); pressure range of 4–6 Kbar; temperature range from T<sub>SCF</sub>  = 350-400°C at the lens’ top to T<sub>BDT</sub>  = 600–650°C at the bottom, characteristic for the emergence of supercritical fluids and for the solidus of granite, respectively; presence of a cap (a relatively dense, poorly permeable zone) that shields the forming fluid reservoir from above.</p><p>Joint analysis of these models made it possible to rule out the molten rocks as a responsible factor for high electrical conductivity and, with a high degree of confidence, assume supercritical fluid nature of the observed petrophysical anomalies. It was supposed that the lens is most likely to be a giant reservoir of supercritical fluids located at the depths between isotherms  T<sub>SCF </sub> and  T<sub>BDT</sub> corresponding to the PT-conditions of existence of supercritical fluids, on the one hand, and granite solidus (brittle / ductile transition), on the other hand.</p><p>The mechanism of its formation could be explained by dehydration of amphibolites accompanied by dissolution of chlorides which, in turn, leads to the emergence of films with sufficiently high electrical conductivity typical of supercritical highly mineralized solutions. Although this formation scenario fairly well explains the observed anomalies, it does not exclude another mechanism associated with the partially melted material risen from the large depths.</p><p>The lens lifetime was determined from properties of the cap. Assuming that for the Cenozoic folding regions, the rock permeability is around 10<sup>-21</sup> m<sup>2</sup> we could roughly estimate the rate of fluid migration through it. Accordingly the lens lifetime is around 33 million years which is consistent with the age of the Cenozoic activation zones.</p>

scholarly journals High Mountain Asian glacier response to climate revealed by multi-temporal satellite observations since the 1960s

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Atanu Bhattacharya ◽  
Tobias Bolch ◽  
Kriti Mukherjee ◽  
Owen King ◽  
Brian Menounos ◽  
...  
Keyword(s):  
Mass Loss ◽  
River Flow ◽  
Tien Shan ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Temperature And Precipitation ◽  
Multi Temporal ◽  
The 1960S ◽  
Northern Tien Shan

AbstractKnowledge about the long-term response of High Mountain Asian glaciers to climatic variations is paramount because of their important role in sustaining Asian river flow. Here, a satellite-based time series of glacier mass balance for seven climatically different regions across High Mountain Asia since the 1960s shows that glacier mass loss rates have persistently increased at most sites. Regional glacier mass budgets ranged from −0.40 ± 0.07 m w.e.a−1 in Central and Northern Tien Shan to −0.06 ± 0.07 m w.e.a−1 in Eastern Pamir, with considerable temporal and spatial variability. Highest rates of mass loss occurred in Central Himalaya and Northern Tien Shan after 2015 and even in regions where glaciers were previously in balance with climate, such as Eastern Pamir, mass losses prevailed in recent years. An increase in summer temperature explains the long-term trend in mass loss and now appears to drive mass loss even in regions formerly sensitive to both temperature and precipitation.

scholarly journals Facies Heterogeneity and Lobe Facies Multiscale Analysis of Deep-Marine Sand-Shale Complexity in the West Crocker Formation of Sabah Basin, NW Borneo

2021 ◽  
Vol 11 (12) ◽  
pp. 5513
Author(s):  
Muhammad Jamil ◽  
Numair Ahmed Siddiqui ◽  
Abdul Hadi Bin Abd Rahman ◽  
Noor Azahar Ibrahim ◽  
Mohd Suhaili Bin Ismail ◽  
...  
Keyword(s):  
Conceptual Model ◽  
Marine Sediments ◽  
Multiscale Analysis ◽  
The West ◽  
Submarine Fans ◽  
Marine Sand ◽  
Facies Associations ◽  
Vertical Thickness ◽  
Mudstone Facies

Deepwater lobes constitute a significant volume of submarine fans and are primarily believed to exhibit a simple sheet geometry. However, recent studies interpret the geometries of these deep-marine lobes as distinct with respect to the complexity of the facies and their distribution. Hence, a conceptual model of deep-marine sediments is essential to discuss the deep-marine sediments associated with the fan and lobe architecture. The present study highlights the facies heterogeneity and distribution of various lobe elements at a multiscale level by considering a case study of the West Crocker Formation of Sabah in northwest Borneo. The formation was logged on a bed-to-bed scale from recently well-exposed sections, with a total vertical thickness of more than 300 m. The lithological characteristics, bed geometry, sedimentary textures and structures of individual beds were used to categorize the rock units into nine sedimentary lithofacies: five sandstone lithofacies (S1–S5), one hybrid bed facies (H), two siltstone facies (Si1 and Si2) and one shale or mudstone facies (M). These facies were grouped into four facies associations (FA1–FA4), which were interpreted as lobe axis (FA1), lobe off-axis (FA2), lobe fringe (FA3) and distal fringe to interlobe (FA4) facies associations. This study is applicable for the distribution of lobes and their subseismic, multiscale complexities to characterize the potential of hydrocarbon intervals in deep-marine sand-shale system around the globe.

scholarly journals Accountability through mutual attunement: How can parliamentary hearings connect the elected and the unelected?

2020 ◽  
pp. 095207672097760
Author(s):  
Andreas Eriksen ◽  
Alexander Katsaitis
Keyword(s):  
Conceptual Model ◽  
European Governance ◽  
Accountability Mechanism ◽  
Shared Understandings ◽  
Working Out

The increased authority delegated to independent agencies raises questions about the conditions of politically accountable governance, and specifically parliament’s role as a representative institution. Focusing on committee hearings as an accountability mechanism, we ask: How can a parliament employ hearings to ensure that the ends pursued by agencies have a democratic foundation? We propose a model of “mutual attunement” where accountability relations presuppose a process of working-out shared understandings of the ends, means and circumstances of policy needs. We test our argument through a case study assessing the interaction between the European Parliament’s Committee on Economic & Monetary Affairs and the European Securities and Markets Authority. Theoretically, we contribute to discussions on agency accountability and European governance, while providing a novel conceptual model and the first analysis of its kind.

Titanomagnetites and ilmenites from the Early Cenozoic basalts and limburgites of the Northern Tien Shan

2011 ◽  
Vol 47 (6) ◽  
pp. 475-487 ◽  
Author(s):  
A. F. Grachev ◽  
D. M. Pechersky ◽  
V. A. Tsel’movich
Keyword(s):  
Tien Shan ◽  
Early Cenozoic ◽  
Northern Tien Shan

Structure, age substantiation and tectonic setting of the Lower-Middle Ordovician volcanic-sedimentary and plutonic complexes of the western part of the Kyrgyz Range (Northern Tien Shan)

2012 ◽  
Vol 20 (4) ◽  
pp. 317-345 ◽  
Author(s):  
K. E. Degtyarev ◽  
T. Yu. Tolmacheva ◽  
A. V. Ryazantsev ◽  
A. A. Tret’yakov ◽  
A. S. Yakubchuk ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Tien Shan ◽  
Middle Ordovician ◽  
Northern Tien Shan

scholarly journals A simple model to estimate ice ablation under a thick debris layer

2006 ◽  
Vol 52 (179) ◽  
pp. 528-536 ◽  
Author(s):  
Han Haidong ◽  
Ding Yongjing ◽  
Liu Shiyin
Keyword(s):  
Heat Flux ◽  
Simple Model ◽  
Iterative Procedure ◽  
Indirect Comparison ◽  
Tien Shan ◽  
Balance Model ◽  
Complex Phase ◽  
Proposed Model ◽  
Koxkar Glacier

AbstractThis paper presents a simple model to estimate ice ablation under a thick supraglacial debris cover. The key method employed in the model is to establish a link between the debris heat flux and the debris temperature at a certain depth when the heat transfer in the debris is described by a diffusion process. Given surface temperature, debris thermal properties and relevant boundary conditions, the proposed model can estimate mean debris temperature at interfaces of different debris layers using an iterative procedure, and then the heat flux for ice ablation. The advantage of the proposed model is that it only requires a few parameters to conduct the modeling, which is simpler and more applicable than others. The case study on Koxkar glacier, west Tien Shan, China, shows, in general, that the proposed model gives good results for the prediction of debris temperatures, except for an apparent phase shift between modeled and observed values. We suggest that this error is mainly due to complex phase relations between debris temperature and debris heat flux. The modeled ablation rates at three experimental sites also show good results, using a direct comparison with observed data and an indirect comparison with a commonly used energy-balance model.

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