Chapter 4 Large-scale structure of the study area

10.1144/m54.4 ◽  
2021 ◽  
Vol 54 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Andreas Scharf ◽  
Frank Mattern ◽  
Mohammed Al-Wardi ◽  
Gianluca Frijia ◽  
Daniel Moraetis ◽  
...  
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Deep Structure ◽  
Sedimentary Rocks ◽  
Moho Depth ◽  
Metasedimentary Rocks ◽  
Eastern Margin ◽  
Oman Mountains ◽  
Basement Faults ◽  
Geological Map

AbstractThe Southeastern Oman Mountains are dominated by two major culminations: the Jabal Akhdar and Saih Hatat domes, surrounded by allochthonous and/or neo-autochthonous rocks. In the cores of both domes, folded autochthonous and par-autochthonous pre-Permian metasedimentary rocks are exposed, subjacent to the ‘Hercynian’ Unconformity. Above the unconformity are Permo--Mesozoic shelfal sedimentary rocks, characterized by carbonates. These sedimentary rocks were openly folded. The open folds are large-scale elongate structures that define the shapes of both domes. The main elongation direction is NW--SE. Doming is syn- to post-obductional. Most margins of the domes are marked by major post-obductional, extensional faults. Reactivated basement faults along the eastern margin of the Jabal Akhdar Dome may be responsible for the straight NNE-striking eastern margin which is perpendicular to the main elongation direction of the domes. The deep structure of both domes is poorly known. However, the Moho depth below the centre of the Jabal Akhdar Dome is at 50 km. We present a geological map of both domes, depicting the main faults and folds, and schematic cross-sections, parallel and perpendicular to the Oman Mountains.

Descriptive text to Geological map of Greenland, 1:500 000, Dove Bugt, Sheet 10

2009 ◽  
pp. 1-32 ◽  
Author(s):  
Niels Henriksen ◽  
A.K. Higgins
Keyword(s):  
Sedimentary Rocks ◽  
Significant Proportion ◽  
Structural Domain ◽  
The South ◽  
Regional Survey ◽  
Medium Temperature ◽  
Thrust Sheet ◽  
Metasedimentary Rocks ◽  
Thrust Zone ◽  
Geological Map

NOTE: This Map Description was published in a former series of GEUS Bulletin. Please use the original series name when citing this series, for example: Henriksen, N., & Higgins, A. (2009). Descriptive text to Geological map of Greenland, 1:500 000, Dove Bugt, Sheet 10. Geological Survey of Denmark and Greenland Map Series 4, 1-32. https://doi.org/10.34194/geusm.v4.4581 _______________ The Dove Bugt 1:500 000 scale geological map sheet covers a segment of the East Greenland Caledonian orogen extending between latitudes 75°–78°N and longitudes 16°–29°W. The region was mapped in the summers of 1988–1990 as part of a regional Survey mapping programme, and the map sheet was printed in 1997. The region covered by the Dove Bugt map sheet is dominated by Palaeoproterozoic gneiss complexes, with smaller amounts of Mesoproterozoic and Neoproterozoic metasedimentary rocks, and isolated strips of Palaeoproterozoic and Lower Palaeozoic sedimentary rocks. All these rock units have been reworked to a varying degree during the Caledonian orogeny. Post-Caledonian sedimentary rocks occur in the south-east corner of the map sheet area and as narrow, fault-bounded enclaves elsewhere, while Palaeogene basaltic lavas and sills crop out on the island of Shannon. The rocks of the Caledonian orogen form a number of major thrust domains. The most extensive and structurally lowest is the Nørreland thrust sheet which is characterised by lenses and layers of medium-temperature, high-pressure eclogites. The Western thrust belt occupies a broad zone of eastern Dronning Louise Land that comprises Palaeoproterozoic gneiss complexes interleaved with Palaeoproterozoic and Palaeozoic metasedimentary rocks. This thrust domain is separated from the foreland rocks of western Dronning Louise Land by the Imbricate thrust zone. In the south-west part of the map sheet the highest structural domain, the Hagar Bjerg thrust sheet comprises three rock sequences: crystalline gneisses, the Mesoproterozoic Smallefjord sequence and the Neoproterozoic Eleonore Bay Supergroup. The crystalline gneiss complexes that dominate the map sheet area and make up a significant proportion of the different Caledonian thrust domains have all yielded protolith ages of c. 2 Ga. They are attributed to a major period of crust formation in the Palaeoproterozoic. The gneisses have been variably affected by Caledonian deformation and metamorphism.

U–Pb age constraints for deposition of clastic metasedimentary rocks and late-tectonic plutonism, Michipicoten Belt, Superior Province

1992 ◽  
Vol 29 (8) ◽  
pp. 1640-1651 ◽  
Author(s):  
F. Corfu ◽  
R. P. Sage
Keyword(s):  
Isotopic Composition ◽  
Greenstone Belt ◽  
Nepheline Syenite ◽  
Large Scale ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Metasedimentary Rocks ◽  
Enriched Mantle ◽  
The Matrix ◽  
Age Constraints

The study investigates the ages of clastic metasedimentary rocks and of late-tectonic alkalic to calc-alkalic intrusions and puts constraints on the timing of major deformation in the Michipicoten greenstone belt of the Wawa Subprovince. A trondhjemitic boulder in the Doré conglomerate of the southern metasedimentary belt is dated at 2698 ± 2 Ma. This is a maximum age of sedimentation that is also supported by ages of detrital zircons in the matrix and may directly reflect the time of synvolcanic deposition. Detrital zircons in metapsammites of the central and northern sedimentary belts yield younger ages of 2682 ± 3 and 2680 ± 3 Ma, respectively, suggesting that sedimentation occurred significantly later in the northern than in the southern parts of the greenstone belt. The ≤2682 Ma sedimentary rocks were affected by multiphase deformation that is related to the development of a large-scale recumbent fold and superimposed folds and faults. This tectonism was followed by the emplacement of the granodioritic Troupe Lake and Maskinonge Lake stocks that yield identical zircon and titanite ages of 2671 ± 2 Ma. The structurally older and deformed Herman Lake nepheline syenite has an imprecise titanite age of [Formula: see text]. The isotopic composition of Pb in feldspar of these intrusions is relatively evolved and, in light of geochemical considerations, may reflect provenance of the melts from enriched mantle reservoirs.

scholarly journals Descriptive text to Geological map of Greenland, 1:500 000, Dove Bugt, Sheet 10

2009 ◽  
pp. 1-32 ◽  
Author(s):  
Niels Henriksen ◽  
A.K. Higgins
Keyword(s):  
Sedimentary Rocks ◽  
Significant Proportion ◽  
Structural Domain ◽  
The South ◽  
Regional Survey ◽  
Medium Temperature ◽  
Thrust Sheet ◽  
Metasedimentary Rocks ◽  
Thrust Zone ◽  
Geological Map

The Dove Bugt 1:500 000 scale geological map sheet covers a segment of the East Greenland Caledonian orogen extending between latitudes 75°–78°N and longitudes 16°–29°W. The region was mapped in the summers of 1988–1990 as part of a regional Survey mapping programme, and the map sheet was printed in 1997. The region covered by the Dove Bugt map sheet is dominated by Palaeoproterozoic gneiss complexes, with smaller amounts of Mesoproterozoic and Neoproterozoic metasedimentary rocks, and isolated strips of Palaeoproterozoic and Lower Palaeozoic sedimentary rocks. All these rock units have been reworked to a varying degree during the Caledonian orogeny. Post-Caledonian sedimentary rocks occur in the south-east corner of the map sheet area and as narrow, fault-bounded enclaves elsewhere, while Palaeogene basaltic lavas and sills crop out on the island of Shannon. The rocks of the Caledonian orogen form a number of major thrust domains. The most extensive and structurally lowest is the Nørreland thrust sheet which is characterised by lenses and layers of medium-temperature, high-pressure eclogites. The Western thrust belt occupies a broad zone of eastern Dronning Louise Land that comprises Palaeoproterozoic gneiss complexes interleaved with Palaeoproterozoic and Palaeozoic metasedimentary rocks. This thrust domain is separated from the foreland rocks of western Dronning Louise Land by the Imbricate thrust zone. In the south-west part of the map sheet the highest structural domain, the Hagar Bjerg thrust sheet comprises three rock sequences: crystalline gneisses, the Mesoproterozoic Smallefjord sequence and the Neoproterozoic Eleonore Bay Supergroup. The crystalline gneiss complexes that dominate the map sheet area and make up a significant proportion of the different Caledonian thrust domains have all yielded protolith ages of c . 2 Ga. They are attributed to a major period of crust formation in the Palaeoproterozoic. The gneisses have been variably affected by Caledonian deformation and metamorphism.

scholarly journals Structural evolution of the Hawasina Window, Oman Mountains

GeoArabia ◽  
2010 ◽  
Vol 15 (3) ◽  
pp. 85-124 ◽  
Author(s):  
László Csontos ◽  
Tamás Pocsai ◽  
Ágoston Sasvári ◽  
Márton Palotai ◽  
Gizella Árgyelán-Bagoly ◽  
...  
Keyword(s):  
Cross Sections ◽  
Structural Evolution ◽  
Structural Features ◽  
Strike Slip ◽  
Arabian Plate ◽  
Oman Mountains ◽  
Tectonic Events ◽  
Northern Edge ◽  
Geological Map ◽  
Tectonic Boundaries

ABSTRACT This paper presents field observations and measurements from the Hawasina Window, Oman Mountains. An updated geological map is based partly on previous publications and four NEtrending cross-sections. Along each cross-section key structural features are described, illustrated and interpreted. Based on these (and other) observations several differences between our interpretation and the former published geological maps and cross sections were noted as follows.(1) Late Cretaceous original (Hamrat Duru; Haybi) nappes that formed during intra-oceanic obduction underwent out-of-sequence thrusting beneath the Semail thrust. The repetitions of the nappe complexes are out-of-sequence because: (a) repetition of original nappe packages; (b) the presence of Haybi-derived lenses along boundaries between two Hamrat Duru nappes; (c) the presence of sheared serpentinite in the same nappe boundaries. The Hamrat Duru and Haybi nappes are repeated three times.(2) The tectonic boundaries of the Hawasina Window are steep, normal- or strike-slip faults, unconformable to, and cutting the original nappe boundaries. A main strike-slip corridor at the southern edge of the Hawasina structure was mapped. The northern edge is a top-north thrust.(3) Ductile-brittle extension created mega-boudins of preserved nappe units and areas where complete nappe units are missing. Extension is present in Sumeini and Hamrat Duru units; therefore it is post-out-of-sequence thrusting.(4) Two main antiforms were recognised inside the Hawasina Window (Jabal Rais and its northward and southward continuations in Hamrat Duru units, and Jabals Mawq - Matid). Several folding phases were recognised and the two antiforms are the result of interference. A main, sub-horizontal axial plane, syn-regional cleavage folding is present in the whole Window. This folding gives top NE or N regional shear.(5) Structural dips of regional cleavage suggest a major NW-striking dome beneath the Hawasina Window. This dome would correspond to the upwarp of the Autochthon, similar to Al Jabal al-Akhdar. In the southern zone of this dome we observed several occurrences of small gypsum diapirs. The best outcrops of these features are in the Wadi ad Dil-Wadi Hawasina area, where the evaporite bodies rise from beneath the Hawasina nappes. We suggest that they originate from the underlying Arabian Platform, or they form the basal detachment of the Sumeini units. Our observations are fit into a proposed deformation scenario resulting from plate-tectonic events occurring at the Arabian Plate margin during Cretaceous – Tertiary time.

Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996

1997 ◽  
pp. 60-65
Author(s):  
Adam A. Garde ◽  
Brian Chadwick ◽  
John Grocott ◽  
Cees Swager
Keyword(s):  
Field Work ◽  
Deformation History ◽  
The South ◽  
Present Contribution ◽  
East Part ◽  
Metasedimentary Rocks ◽  
Deformational History ◽  
Base Camp ◽  
History Of ◽  
Geological Map

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Garde, A. A., Chadwick, B., Grocott, J., & Swager, C. (1997). Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 60-65. https://doi.org/10.34194/ggub.v176.5063 _______________ The south-east part of the c. 1800 Ma Ketilidian orogen in South Greenland (Allaart, 1976) is dominated by strongly deformed and variably migmatised metasedimentary rocks known as the ‘Psammite and Pelite Zones’ (Chadwick & Garde, 1996); the sediments were mainly derived from the evolving Julianehåb batholith which dominates the central part of the orogen. The main purpose of the present contribution is to outline the deformational history of the Psammite Zone in the region between Lindenow Fjord and Kangerluluk (Fig. 2), investigated in 1994 and 1996 as part of the SUPRASYD project (Garde & Schønwandt, 1995 and references therein; Chadwick et al., in press). The Lindenow Fjord region has high alpine relief and extensive ice and glacier cover, and the fjords are regularly blocked by sea ice. Early studies of this part of the orogen were by boat reconnaissance (Andrews et al., 1971, 1973); extensive helicopter support in the summers of 1992 and 1994 made access to the inner fjord regions and nunataks possible for the first time.A preliminary geological map covering part of the area between Lindenow Fjord and Kangerluluk was published by Swager et al. (1995). Hamilton et al. (1996) have addressed the timing of sedimentation and deformation in the Psammite Zone by means of precise zircon U-Pb geochronology. However, major problems regarding the correlation of individual deformational events and their relationship with the evolution of the Julianehåb batholith were not resolved until the field work in 1996. The SUPRASYD field party in 1996 (Fig. 1) was based at the telestation of Prins Christian Sund some 50 km south of the working area (Fig. 2). In addition to base camp personnel, helicopter crew and the four authors, the party consisted of five geologists and M.Sc. students studying mafic igneous rocks and their mineralisation in selected areas (Stendal et al., 1997), and a geologist investigating rust zones and areas with known gold anomalies.

scholarly journals Experimental Study on Backflow Patterns Induced by a Bilateral Groin Pair with Different Spacing

2021 ◽  
Vol 11 (4) ◽  
pp. 1486
Author(s):  
Cuiping Kuang ◽  
Yuhua Zheng ◽  
Jie Gu ◽  
Qingping Zou ◽  
Xuejian Han
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Recirculation Zone ◽  
Flow Direction ◽  
Wake Flow ◽  
Zone Length ◽  
Array Configuration ◽  
Contraction Ratio ◽  
River Training ◽  
Spanwise Velocity

Groins are one of the popular manmade structures to modify the hydraulic flow and sediment response in river training. The spacing between groins is a critical consideration to balance the channel-depth and the cost of construction, which is generally determined by the backflow formed downstream from groins. A series of experiments were conducted using Particle Image Velocimetry (PIV) to observe the influence of groin spacing on the backflow pattern of two bilateral groins. The spacing between groins has significant effect on the behavior of the large-scale recirculation cell behind groins. The magnitude of the wake flow induced by a groin was similar to that induced by another groin on the other side, but the flow direction is opposite. The spanwise velocity near the groin tip dictates the recirculation zone width behind the groins due to the strong links between the spanwise velocity and the contraction ratio of channel cross-sections between groins. Based on previous studies and present experimental results, quantitative empirical relationships are proposed to calculate the recirculation zone length behind groins alternately placed at different spacing along riverbanks. This study provides better understanding and a robust formula to assess the backflow extent of alternate groins and identify the optimum groins array configuration.

Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma

1990 ◽  
Vol 80 (6A) ◽  
pp. 1677-1695 ◽  
Author(s):  
Ik Bum Kang ◽  
George A. McMechan
Keyword(s):  
Large Scale ◽  
Deep Structure ◽  
Sedimentary Basins ◽  
P Wave ◽  
Two Dimensional ◽  
Anadarko Basin ◽  
Near Surface ◽  
University Of Texas ◽  
Wide Aperture ◽  
The University

Abstract Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies. The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms. The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at ≈40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from ≈2.7 km/sec at the surface to ≈5.9 km/sec at ≈16 km depth, with discontinuous reflections at depths of ≈8, 10, 12, and 16 km.

A metasedimentary source of gold in Archean orogenic gold deposits

Geology ◽  
2021 ◽  
Author(s):  
Iain K. Pitcairn ◽  
Nikolaos Leventis ◽  
Georges Beaudoin ◽  
Stephane Faure ◽  
Carl Guilmette ◽  
...  
Keyword(s):  
Sedimentary Rock ◽  
Sedimentary Rocks ◽  
Gold Deposits ◽  
Metamorphic Grade ◽  
Orogenic Gold ◽  
Metal Source ◽  
Main Metal ◽  
Metasedimentary Rocks ◽  
Orogenic Gold Deposits ◽  
Archean Orogenic Gold Deposits

The sources of metals enriched in Archean orogenic gold deposits have long been debated. Metasedimentary rocks, which are generally accepted as the main metal source in Phanerozoic deposits, are less abundant in Archean greenstone belts and commonly discounted as a viable metal source for Archean deposits. We report ultralow-detection-limit gold and trace-element concentrations from a suite of metamorphosed sedimentary rocks from the Abitibi belt and Pontiac subprovince, Superior Province, Canada. Systematic decreases in the Au content with increasing metamorphic grade indicate that Au was mobilized during prograde metamorphism. Mass balance calculations show that over 10 t of Au, 30,000 t of As, and 600 t of Sb were mobilized from 1 km3 of Pontiac subprovince sedimentary rock metamorphosed to the sillimanite metamorphic zone. The total gold resource in orogenic gold deposits in the southern Abitibi belt (7500 t Au) is only 3% of the Au mobilized from the estimated total volume of high-metamorphic-grade Pontiac sedimentary rock in the region (25,000 km3), indicating that sedimentary rocks are a major contributor of metals to the orogenic gold deposits in the southern Abitibi belt.

Simulation of Flow Field on a Large Scale Wind Turbine

2008 ◽  
Author(s):  
I. Janajreh ◽  
C. Ghenai
Keyword(s):  
Flow Field ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cross Sections ◽  
Large Scale ◽  
Wind Farms ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Capital Costs

Large scale wind turbines and wind farms continue to evolve mounting 94.1GW of the electrical grid capacity in 2007 and expected to reach 160.0GW in 2010 according to World Wind Energy Association. They commence to play a vital role in the quest for renewable and sustainable energy. They are impressive structures of human responsiveness to, and awareness of, the depleting fossil fuel resources. Early generation wind turbines (windmills) were used as kinetic energy transformers and today generate 1/5 of the Denmark’s electricity and planned to double the current German grid capacity by reaching 12.5% by year 2010. Wind energy is plentiful (72 TW is estimated to be commercially viable) and clean while their intensive capital costs and maintenance fees still bar their widespread deployment in the developing world. Additionally, there are technological challenges in the rotor operating characteristics, fatigue load, and noise in meeting reliability and safety standards. Newer inventions, e.g., downstream wind turbines and flapping rotor blades, are sought to absorb a larger portion of the cost attributable to unrestrained lower cost yaw mechanisms, reduction in the moving parts, and noise reduction thereby reducing maintenance. In this work, numerical analysis of the downstream wind turbine blade is conducted. In particular, the interaction between the tower and the rotor passage is investigated. Circular cross sectional tower and aerofoil shapes are considered in a staggered configuration and under cross-stream motion. The resulting blade static pressure and aerodynamic forces are investigated at different incident wind angles and wind speeds. Comparison of the flow field results against the conventional upstream wind turbine is also conducted. The wind flow is considered to be transient, incompressible, viscous Navier-Stokes and turbulent. The k-ε model is utilized as the turbulence closure. The passage of the rotor blade is governed by ALE and is represented numerically as a sliding mesh against the upstream fixed tower domain. Both the blade and tower cross sections are padded with a boundary layer mesh to accurately capture the viscous forces while several levels of refinement were implemented throughout the domain to assess and avoid the mesh dependence.

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