Three-dimensional strain accumulation and partitioning in an arcuate orogenic wedge: An example from the Himalaya

2020 ◽  
Vol 133 (1-2) ◽  
pp. 3-18 ◽  
Author(s):  
Suoya Fan ◽  
Michael A. Murphy
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Western Himalaya ◽  
Shear Zones ◽  
High Elevation ◽  
Central Himalaya ◽  
Structural Style ◽  
Orogenic Wedge ◽  
Oblique Convergence ◽  
Thickness Variations

Abstract In this study, we use published geologic maps and cross-sections to construct a three-dimensional geologic model of major shear zones that make up the Himalayan orogenic wedge. The model incorporates microseismicity, megathrust coupling, and various derivatives of the topography to address several questions regarding observed crustal strain patterns and how they are expressed in the landscape. These questions include: (1) How does vertical thickening vary along strike of the orogen? (2) What is the role of oblique convergence in contributing to along-strike thickness variations and the style of deformation? (3) How do variations in the coupling along the megathrust affect the overlying structural style? (4) Do lateral ramps exist along the megathrust? (5) What structural styles underlie and are possibly responsible for the generation of high-elevation, low-relief landscapes? Our model shows that the orogenic core of the western and central Himalaya displays significant along-strike variation in its thickness, from ∼25–26 km in the western Himalaya to ∼34–42 km in the central Himalaya. The thickness of the orogenic core changes abruptly across the western bounding shear zone of the Gurla Mandhata metamorphic core complex, demonstrating a change in the style of strain there. Pressure-temperature-time results indicate that the thickness of the orogenic core at 37 Ma is 17 km. Assuming this is constant along strike from 81°E to 85°E indicates that, the western and central Nepal Himalaya have been thickened by 0.5 and 1–1.5 times, respectively. West of Gurla Mandhata the orogenic core is significantly thinner and underlies a large 11,000 km2 Neogene basin (Zhada). A broad, thick orogenic core associated with thrust duplexing is collocated with an 8500 km2 high-elevation, low-relief surface in the Mugu-Dolpa region of west Nepal. We propose that these results can be explained by oblique convergence along a megathrust with an along-strike and down-dip heterogeneous coupling pattern influenced by frontal and oblique ramps along the megathrust.

Topographic features of the sub-Athabasca Group unconformity surface in the southeastern Athabasca Basin and their relationship to uranium ore deposits

2015 ◽  
Vol 52 (10) ◽  
pp. 903-920 ◽  
Author(s):  
Zenghua Li ◽  
Kathryn M. Bethune ◽  
Guoxiang Chi ◽  
Sean A. Bosman ◽  
Colin D. Card
Keyword(s):  
Cross Sections ◽  
Regional Scale ◽  
Three Dimensional ◽  
Shear Zones ◽  
Ore Deposits ◽  
Athabasca Basin ◽  
Topographic Features ◽  
Dominant Sets ◽  
Lake Deposits ◽  
Unconformity Surface

Topographic features of the sub-Athabasca unconformity surface, such as paleovalleys, topographic highs, and fault scarps, have been documented locally in the eastern Athabasca Basin, and available data indicate that they are spatially associated with mineralization. However, the mechanisms by which such topographic features were generated, their size and distribution at the regional scale, as well as their relationship to mineralization, are still not completely understood. A 100 by 60 square kilometre area of the southeastern Athabasca Basin, encompassing the McArthur River, Phoenix, and Key Lake deposits, was selected to study the relationship between these topographic features and U mineralization. In this region three dominant sets of sub-vertical faults were identified on the basis of aeromagnetic data: northeast-trending, north–northwest-trending, and northwest-trending. A detailed three-dimensional (3-D) model of this part of the basin was constructed using data from more than 1200 drill holes. This model reveals numerous dominantly northeast-trending ridges and valleys in the unconformity surface. Among these, a prominent northeast-trending ridge is situated close to the McArthur River – Key Lake deposits trend. Structural interpretation and cross-sections illustrate that the topographic features that have been documented in previous studies are a function of three principal factors: (i) pre-Athabasca group ductile-brittle faulting and alteration; (ii) differential weathering and erosion; and (iii) syn- to post-Athabasca ductile-brittle reactivation of pre-existing graphite-rich ductile shear zones. The topographic features and associated faults may have acted as conduits and barriers to fluid flow and thus controlled alteration patterns and uranium mineralization.

Geological Field Sketches and Illustrations

2019 ◽  
Author(s):  
Matthew J. Genge
Keyword(s):  
Cross Sections ◽  
Earth Science ◽  
Three Dimensional ◽  
Worked Examples ◽  
Scientific Publications ◽  
Thin Sections ◽  
Geological Features ◽  
Different Types ◽  
The Subject

Drawings, illustrations, and field sketches play an important role in Earth Science since they are used to record field observations, develop interpretations, and communicate results in reports and scientific publications. Drawing geology in the field furthermore facilitates observation and maximizes the value of fieldwork. Every geologist, whether a student, academic, professional, or amateur enthusiast, will benefit from the ability to draw geological features accurately. This book describes how and what to draw in geology. Essential drawing techniques, together with practical advice in creating high quality diagrams, are described the opening chapters. How to draw different types of geology, including faults, folds, metamorphic rocks, sedimentary rocks, igneous rocks, and fossils, are the subjects of separate chapters, and include descriptions of what are the important features to draw and describe. Different types of sketch, such as drawings of three-dimensional outcrops, landscapes, thin-sections, and hand-specimens of rocks, crystals, and minerals, are discussed. The methods used to create technical diagrams such as geological maps and cross-sections are also covered. Finally, modern techniques in the acquisition and recording of field data, including photogrammetry and aerial surveys, and digital methods of illustration, are the subject of the final chapter of the book. Throughout, worked examples of field sketches and illustrations are provided as well as descriptions of the common mistakes to be avoided.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

scholarly journals Computer-aided design of multi-purpose steel headframes for mines with a new technical level

2020 ◽  
Vol 174 ◽  
pp. 01048
Author(s):  
Elena Kassikhina ◽  
Vladimir Pershin ◽  
Nina Rusakova
Keyword(s):  
Cross Sections ◽  
Computer Aided Design ◽  
Information Technologies ◽  
Three Dimensional ◽  
Numerical Control ◽  
Technical Level ◽  
Resource Saving ◽  
Existing Structures ◽  
Set Up ◽  
Aided Design

The existing structures of the steel sinking headgear and permanent headframe do not meet the requirements of resource saving (metal consumption and manpower input at installation), and the present methods of the headframe designing do not fully reflect recent possibilities of applying of the advanced information technologies. Technical level of the modern software makes it possible for designers to set up multiple numerical experiments to create a computer simulation that allows solving the problem without field and laboratory experiments, and therefore without special costs. In this regard, a mathematical simulation has been developed and based on it, software to select cross-sections of multi- purpose steel headframe elements and to calculate proper weight of its metal structures depending on the characteristics and hoisting equipment. A headframe drawing is displayed, as the results of the software work, including list of elements, obtained optimal hoisting equipment in accordance with the initial data. The software allows speeding up graphic work and reducing manpower input on calculations and paper work. The software allows developing a three-dimensional image of the structure and its functional blocks, based on the obtained initial parameters, as well as developing control software for units with numerical control (NC) in order to manufacture multi-purpose headframes.

Analysing the Natural Resting Aspects of a Component for Automated Assembly

1995 ◽  
Vol 209 (2) ◽  
pp. 125-131 ◽  
Author(s):  
B K A Ngoi ◽  
L E N Lim ◽  
S S G Lee ◽  
S W Lye
Keyword(s):  
Cross Sections ◽  
Computer Aided Design ◽  
Energy Barrier ◽  
Three Dimensional ◽  
Rectangular Prism ◽  
Automatic Assembly ◽  
Automated Assembly ◽  
Barrier Method ◽  
Aided Design ◽  
Natural Resting Aspect

This paper proposes the construction of an energy envelope that can be used to advantage with the energy barrier method to analyse the natural resting aspect of engineering parts destined for automatic assembly. Unlike the energy barrier method, the energy envelope does not require any visualization of the projection of the energy barrier on the aspect of interest. The energy envelope is the three-dimensional topology of the changes in height of the centroid, as the part attempts changes of aspect. The paper describes how it may be computed in a CAD (computer aided design) solid modeller. The results of applying the energy envelope to prisms of square and cylindrical cross-sections are the same as those predicted by the energy barrier method. When extended to the analysis of a rectangular prism, the results were consistent with Boothroyd's dynamic solution and Boothroyd's experimental data. This conclusion is encouraging as there is no irrefutable evidence that the energy barrier method may be applied to the analysis of the rectangular prism.

scholarly journals Three-dimensional quantification of twisting in the Arabidopsis petiole

2021 ◽  
Author(s):  
Yuta Otsuka ◽  
Hirokazu Tsukaya
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Light Sheet ◽  
Underlying Mechanism ◽  
Two Dimensions ◽  
Observation Angle ◽  
Differential Growth ◽  
Light Sheet Microscopy ◽  
Definition Of ◽  
Twisting Angle

AbstractOrganisms have a variety of three-dimensional (3D) structures that change over time. These changes include twisting, which is 3D deformation that cannot happen in two dimensions. Twisting is linked to important adaptive functions of organs, such as adjusting the orientation of leaves and flowers in plants to align with environmental stimuli (e.g. light, gravity). Despite its importance, the underlying mechanism for twisting remains to be determined, partly because there is no rigorous method for quantifying the twisting of plant organs. Conventional studies have relied on approximate measurements of the twisting angle in 2D, with arbitrary choices of observation angle. Here, we present the first rigorous quantification of the 3D twisting angles of Arabidopsis petioles based on light sheet microscopy. Mathematical separation of bending and twisting with strict definition of petiole cross-sections were implemented; differences in the spatial distribution of bending and twisting were detected via the quantification of angles along the petiole. Based on the measured values, we discuss that minute degrees of differential growth can result in pronounced twisting in petioles.

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