SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Koyi Hemin) "

Sökning: WFRF:(Koyi Hemin)

  • Resultat 1-50 av 202
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Abdelmaksoud, Ahmed, et al. (författare)
  • Petroleum system of the fold-and-thrust belt of the United Arab Emirates : New insights based on 1D and 2D basin modeling
  • 2023
  • Ingår i: Marine and Petroleum Geology. - : Elsevier. - 0264-8172 .- 1873-4073. ; 158
  • Tidskriftsartikel (refereegranskat)abstract
    • The hydrocarbon potential of the fold-and-thrust belt (FTB) in the United Arab Emirates (UAE)-Oman mountains has received limited attention to date, leading to a poor understanding of the petroleum systems in this region. Despite the existence of hydrocarbon fields within the FTB, the source rock potential has not been adequately studied. This study aims to address this knowledge gap using 1D and 2D basin modeling approaches to evaluate the petroleum system of the FTB. In addition, gas chromatographs are also used to correlate hydrocarbon occurrences with their source rock. This study's findings identify the Silurian, Upper Cretaceous, Paleocene-Eocene, and Oligocene formations as the primary source rocks in the study area. Silurian shales, encountered in a well in the northern UAE, are currently considered overmature. The Cenozoic source rocks exhibit a spectrum of Total Organic Carbon (TOC) content, ranging from less than 1 to as high as 2 wt%, leading to variable degrees of expulsion efficiency. The maturity of these rocks varies based on their position in relation to the FTB and foredeep, with increasing maturity towards the north. The Upper Cretaceous sequences display low TOC and Hydrogen Index, indicating very low expulsion efficiency. The present-day distribution of maturity is largely influenced by Late Cretaceous and Oligocene-Miocene compressional events that affected the northern and northeastern Arabian Plate. This analysis shows that hydrocarbon expulsion from the Silurian source rocks was initiated during the Middle-Late Jurassic. These hydrocarbons are presumed to have migrated through Upper Permian, Jurassic, and Lower and middle Cretaceous reservoirs. Westward hydrocarbon migration, towards a regional bulge, may have also occurred following compressional events that resulted in lithospheric flexure and formation of the foreland basin. Notably, certain exceptions to migration towards the bulge include structural entrapment of hydrocarbons beneath the main frontal thrust zone of FTB and some structural traps beneath the Lower Fiqa Formation.
  •  
2.
  • Ahmadi, Omid, et al. (författare)
  • Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia
  • 2016
  • Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951. ; 689, s. 56-66
  • Tidskriftsartikel (refereegranskat)abstract
    • The Murchison domain forms the northwest part of the Youanmi Terrane, a tectonic unit within the Neoarchean Yilgarn Craton in Western Australia. In the Cue-Weld Range area the Murchison domain has experienced a complex magmatic and deformation history that resulted in a transposed array of greenstone belts that host significant iron, gold, and base metal deposits. In this study, we interpret the upper 2 s (about 6 km) of a deep crustal seismic profile TOGA-YU1, near the town of Cue, and correlate rock units and structures in outcrop with corresponding reflections. We performed 3D constant velocity ray-tracing and calculate the corresponding travel times for the reflectionsfor time domain pre-stack and post-stack seismic data. This allows us to link shallow reflections with mafic volcanic rocks of the Glen Group and basaltic rocks of the Polelle Group in outcrop. Based on our interpretation and published geological maps and data, we propose a model in which the local stratigraphy represents a refolded thrust system. To test our hypothesis, we applied 2D acoustic finite difference forward modeling. The corresponding synthetic data were processed in the same way as the acquired data. Comparisons between the acquired and the synthetic data show that the model is consistent with observations. We propose a new model for the subsurface of the Cue-Weld Range area and argue that some of the lithologies in the area are repeated structurally at different levels. Our approach highlights the benefit of imaging and modeling of deep seismic transects to resolve local structural complexity in Archean granite-greenstone terrains.
  •  
3.
  • Al-Qayim, Basim, et al. (författare)
  • Tectonostratigraphic overview of the Zagros Suture Zone, Kurdistan Region, Northeast Iraq
  • 2012
  • Ingår i: GeoArabia. - 1025-6059. ; 17:4, s. 109-156
  • Tidskriftsartikel (refereegranskat)abstract
    • The northwestern segment of the Zagros Orogenic Belt of the Kurdistan Region of Iraq includes the Zagros Suture Zone which is consisting of allochthonous Tethyan Triassic-Eocene thrust sheets. The zone is bounded by the Zagros Main Reverse Fault in the northeast, and the Zagros Thrust Front in the southwest. Parts of this zone's rocks are represented by stacks of thrust mega-sheets obducted over the autochthonous Cretaceous-Cenozoic sequence of the Arabian Plate margin. Each sheet represents a specific Tethyan tectonostratigraphic facies, and includes (from older to younger): isolated Triassic carbonate platforms (Avroman Limestone), Jurassic carbonate imbricates (Chia Gara, Sargelu and other formations), radiolarites (Qulqula Group), sedimentary melange (sedimentary-volcanic units of the Qulqula Group), ophiolites (Mawat and Penjwin ultramafics complexes), and Cenozoic fore-arc volcano-sedimentary sequences (Walash Group). Petrography, facies interpretation and lithostratigraphic correlation of these allochthons along four traverses across the Zagros Suture Zone of the examined area indicate that they evolved during the closure of the Neo-Tethys Ocean. Their stacking pattern and tectonic association resulted from two important events: the Late Cretaceous obduction processes, and the Late Miocene Pliocene collision, uplift, folding and suturing between the Arabian Plate and the Sanandaj-Sirjan Block of Iran. Based on these field observations and by using the model of the Iranian Zagros evolution, a tectonic scenario is proposed to explain the history and evolution of the Zagros Suture Zone in this area.
  •  
4.
  • Ali, Moamen, et al. (författare)
  • Geometry and kinematics of the Middle to Late Miocene salt tectonics, central Egyptian Red Sea margin
  • 2023
  • Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 176
  • Tidskriftsartikel (refereegranskat)abstract
    • The Red Sea basin includes a thick Middle to Late Miocene evaporitic succession that underwent halokinesis and caused intensive reshaping of the seafloor and the development of salt-tectonic structures. However, the ge-ometry and kinematics of these structures are still poorly understood. This study uses 2D and 3D seismic surveys and well data of the northern Egyptian Red Sea to systematically describe the distribution and morphology of salt structures, discuss their initiation, and construct a kinematic model for their origin. Our results indicate that the massive salt layer developed into five major NW-SE to NNE-SSW trending salt walls, characterized by relatively irregular crests and moderately dipping flanks. In addition, several symmetrical and asymmetrical folds and two categories of normal faults (subsalt and suprasalt) have been recognized. Based on our observations, salt mobilization in the study area started in the Late Miocene, during the precipitation of layered evaporites, and continued until the present day. In the northern Egyptian Red Sea, seismic interpretation indicates that hal-okinesis was triggered by a combination of thin-and thick-skinned systems, where the latter played a major role. The salt layer was welded during the Quaternary as several sags and grabens developed above the salt diapirs. Thick-skinned physical models are compatible with our observations, supporting the impact of basement faulting on Red Sea diapirism.
  •  
5.
  • Almqvist, Bjarne, et al. (författare)
  • Bulk strain in orogenic wedges based on insights from magnetic fabrics in sandbox models
  • 2018
  • Ingår i: Geology. - 0091-7613 .- 1943-2682. ; 46:6, s. 483-486
  • Tidskriftsartikel (refereegranskat)abstract
    • Anisotropy of magnetic susceptibility (AMS) analysis is used as a petrofabric indicator for a set of four identical-setup sandbox models that were shortened by different amounts and simulate contraction in a fold-and-thrust belt. During model shortening, a progressive reorientation of the initial magnetic fabric occurs due to horizontal compaction of the sand layers. At the early stages of shortening, magnetic lineation (k(1) axis) rotates parallel to the model backstop with subhorizontal orientation, whereas the minimum susceptibility (k(3) axis) is subvertical, which indicates a partial tectonic overprint of the initial fabric. With further shortening, the k(3) axis rotates to subhorizontal orientation, parallel to shortening direction, marking the development of a dominant tectonic magnetic fabric. A near-linear transition in magnetic fabric is observed from the initial bedding to tectonic fabric in all four models, which reflects a progressive transition in deformation from foreland toward hinterland. Model results confirm a long-held hypothesis where the AMS pattern and degree of anisotropy have been suggested to reflect the amount of layer-parallel shortening, based on field observations in many mountain belts. Results furthermore indicate that grain rotation may play a significant role in low-grade compressive tectonic regimes. The combination of analogue models with AMS enables the possibility to predict magnetic fabrics in different tectonic settings and to develop quantitative links between AMS and strain.
  •  
6.
  • Amini, Samar, et al. (författare)
  • Tomographic upper-mantle velocity structure beneath the Iranian Plateau
  • 2012
  • Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 554-557, s. 42-49
  • Tidskriftsartikel (refereegranskat)abstract
    • The Iranian plateau is one of the most structurally complex and tectonically inhomogeneous regions in the world. In this study, we analyze Pn arrival-times from regional seismicity in order to resolve lateral velocity variations within the uppermost-mantle under the Iranian Plateau. More than 48,000 Pn first arrival times selected from the EHB catalog were used with epicentral distances of 200 to 1600 km. We used regularized isotropic and anisotropic damped least-squares inversion to image lateral velocity variations in the upper mantle. Our velocity model, with high lateral resolution, shows positive anomalies in the Zagros mountain belt with a distinct transition approximately along the Main Zagros Thrust to the lower mantle velocity zone of Central Iran. Anomalously low velocities are observed predominantly beneath NW Iran and eastern Turkey, suggesting a zone of relatively weak mantle. Low velocity region under the Damavand volcano reveals the hot upper mantle beneath the central Alborz mountains.
  •  
7.
  • Amri, Zayneb, et al. (författare)
  • Mechanical relationship between strike-slip faulting and salt tectonics in the Northern Tunisian Atlas : The Bir-El-Afou salt structure
  • 2022
  • Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 154
  • Tidskriftsartikel (refereegranskat)abstract
    • Wide variety of salt structures -from typical diapirs to large allochthonous salt sheets- are recognized in the Northern Tunisian Atlas. In this study, we present for the first time the presence of a diapiric structure, Bir-ElAfou Salt Structure (BEASS), which has formed in response to strike-slip tectonics. Structural mapping, mesoscale field observations, fault kinematic analysis, and interpretation of gravity data are used to interpret BEASS, which is currently associated with a restraining bend. The present-day NNE- trending restraining stepover is formed as a result of E-W dextral fault system. We assume that the restraining stepover is a product of the inversion of a pre-existing pull-apart basin that formed during the Cretaceous South Tethyan extension. Tectono-sedimentary relationship is used to argue for an early Cretaceous NW-SE regional extension and local transtension. During the opening of the pull-apart basin, salt movement took place in the southwestern corner of the basin which must have thinned due to its extension facilitating diapiric emplacement. Diapir growth during Aptian was followed by brief salt flow from the diapir crest towards the basin forming a salt sheet. A period of Tertiary contraction resulted in the inversion of the pull-apart basin and consequently, squeezing of BEASS.
  •  
8.
  •  
9.
  •  
10.
  • Aswad, Khalid J. A., et al. (författare)
  • Cr-spinel compositions in serpentinites, and their implications for the petrotectonic history of the Zagros Suture Zone, Kurdistan Region, Iraq
  • 2011
  • Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 148:5-6, s. 802-818
  • Tidskriftsartikel (refereegranskat)abstract
    • Accessory chrome spinels are scattered throughout the serpentinite masses in two allochthonous thrust sheets belonging to the Penjween–Walash sub-zone of the northwestern Zagros Suture Zone in Kurdistan. Based on field evidence, the serpentinites are divided into two groups: (1) highly sheared serpentinites (110–80 Ma), which occupy the lower contact of the ophiolitic massifs of the Upper Allochthonous sheet (Albian–Cenomanian age), and (2) ophiolitic mélange serpentinites of mixed ages (150 and 200 Ma) occurring along thrust faults on the base of the volcano-sedimentary segment (42–32 Ma) of the Lower Allochthonous sheet. The Cr-spinels of both groups show a wide range of YCr (Cr/(Cr + Al) atomic ratio) from 0.37 to 1.0, while the XMg (Mg/(Mg + Fe2+) atomic ratio) ranges from 0.0 to 0.75. Based on the Cr-spinel compositions of the entire dataset and in conjunction with back-scattered electron imaging, from core to rim, three spinel stages have been recognized: the residual mantle stage, a Cr-rich stage and a third stage showing a very narrow magnetite rim. These three stages are represented by primary Cr-spinel, pre-serpentinization metamorphosed spinel and syn- or post-serpentinization spinel, respectively. The chemical characteristics of primary (first-stage) Cr-spinels of both serpentinite groups indicate a tectonic affinity within a fore-arc setting of peridotite protoliths. The second stage indicates that Cr-spinels have undergone subsolidus re-equilibration as a result of solid–solid reaction during pre-serpentinization cooling of the host rock. Here the primary Cr-spinel compositions have been partly or completely obscured by metamorphism. During the third stage, the Cr-spinels have undergone solid–fluid re-equilibration during syn- or post-serpentinization processes. Both the second and third stages point to diachronous metamorphic paths resulting from continuous tectonic evolution influenced by either slow or fast uplift of mantle protoliths. In the fast metamorphic paths, the primary chrome spinels are flanked by a very narrow magnetite rim. The presence of two groups of distally separated serpentinites with different emplacement ages and fore-arc tectonic affinity could indicate that the closure of the Tethys Ocean culminated in two fortuitous subduction processes.
  •  
11.
  • Aziz, Nabaz R. H., et al. (författare)
  • Contrasting Settings of Serpentinite Bodies in Northwestern Zagros Suture Zone, Kurdistan Region, Iraq
  • 2011
  • Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 148:5-6, s. 819-837
  • Tidskriftsartikel (refereegranskat)abstract
    • Protrusions and lenses of serpentinite–matrix mélanges occur at several places along the thrust faults of the Zagros Suture Zone. They separate the lower allochthonous thrust sheet, the ‘Lower Allochthon’ (i.e. Walash–Naopurdan nappe), of Paleocene–Eocene age from sediments of the Arabian platform and the upper thrust sheet of Mesozoic, ophiolite-bearing terranes termed the ‘Upper Allochthon’ (i.e. Gemo–Qandil nappe). The serpentinite–matrix mélanges occur mostly as stretched bodies (slices) on both sides of the Lower Allochthon (Hero, Halsho and Pushtashan (HHP) and Galalah, Qalander and Rayat (GQR)). Their overall chondrite-normalized rare earth element (REE) patterns form two main groups. Group One exhibits enrichment in the total REEs (> 1 × chondrite) whereas the Group Two pattern shows depletion (i.e. < 1 × chondrite). Bulk-rock MORB-normalized profiles of Group Two are almost flat in the MREE–HREE region with flattening profiles in the Gd–Lu range (> 3 times the MORB composition). In comparison with Group One, Group Two has extremely high REE content and displays variable depletions in the moderately incompatible high-field-strength elements (HFSEs) (Zr, Hf, Y) relative to their adjacent REEs. The REEs in the GQR serpentinite–matrix mélanges have a noticeably high LREE content, and a positive Eu anomaly, and their HREE content never reaches more than 1 × chondrite (i.e. < 0.01 to 1 × chondrite). The latter indicates that the hemipelagic sedimentary, melt-like components (i.e. high LREE, U/La, La/Sm and low Ba/Th) control the geochemical peculiarities of this type of serpentinite. The HHP serpentinite–matrix mélanges, however, are either equally divided between the two REE pattern groups (e.g. Hero, Halsho) or inclined towards Group One (e.g. Pushtashan). Contrary to GQR serpentinites, the variation in HHP serpentinite–matrix mélanges spans a compositional spectrum from U/La-rich to more Ba/Th-rich. Such ratio variations reflect the large variation in these two subducted sedimentary components (i.e. carbonate and hemipelagic sediment mix). The obvious differences in the trace element signatures of the GQR and HHP serpentinite–matrix mélanges might be related to plate tectonic parameters such as convergence rate, subduction age and thickness and type of subducted slab. It is more likely that the influx of subducted components to the mantle wedge relied heavily on the composition of the sedimentary inputs. These vary considerably with time from the relatively deepwater hemipelagic sediments (Qulqula Radiolarite Formation) to platform carbonate sediments (Balambo limestone). The trace element signatures of the GQR and HHP serpentinite–matrix mélanges might suggest multi-staging of the allochthonous sheet emplacement on the Arabian platform sediments.
  •  
12.
  • Bahroudi, A, et al. (författare)
  • Effect of ductile and frictional decollements on style of extension
  • 2003
  • Ingår i: Journal of Structural Geology. - 0191-8141 .- 1873-1201. ; 25:9, s. 1401-1423
  • Tidskriftsartikel (refereegranskat)abstract
    • Scaled analogue models were used to study the effect of frictional and ductile detachments on thin-skinned extension. Models consisted of two halves; one half is the ductile and the other has a frictional detachment. Extension occurred above two different basal configurations: a stretchable rubber sheet and a folded, banded sheet intended to produce homogeneous and heterogeneous extension, respectively. Model parameters varied systematically and included the brittle/ductile thickness ratio, rheologies, and bulk strain. Structures in the two halves are compared in profiles and plan views. A series of graben developed above both halves of models extended above a banded sheet, although there were differences in style, propagation rate and width of the deformation zone between the two halves. Different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction. Most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves.In contrast, in models extended above a stretchable rubber sheet, extensional structures such as horst and graben developed only above the ductile detachment. Model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet. However, above 20% bulk extension, deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction.
  •  
13.
  •  
14.
  • Buntin, Sebastian, et al. (författare)
  • Emplacement and 3D geometry of crustal-scale saucer-shaped intrusions in the Fennoscandian Shield
  • 2019
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Saucer-shaped intrusions of tens of meters to tens of kilometres across have been observed both from surface geological mapping and geophysical observations. However, there is only one location where they have been reported to extend c. 100 km laterally, and emplaced both in a sedimentary basin and the crystalline basement down to 12 km depth. The legacy BABEL offshore seismic data, acquired over the central Fennoscandian Shield in 1989, have been recovered and reprocessed with the main goal of focusing on this series of globally unique crustal-scale saucer-shaped intrusions present onshore and offshore below the Bothnian Sea. The intrusions (c. 1.25 Ga), emplaced in an extensional setting, are observed within both sedimentary rocks (<1.5 Ga) and in the crystalline basement (>1.5 Ga). They have oval shapes with diameters ranging 30-100 km. The reprocessed seismic data provide evidence of up-doming of the lower crust (representing the melt reservoir) below the intrusions that, in turn, are observed at different depths in addition to a steep seismically transparent zone interpreted to be a discordant feeder dyke system. Relative age constraints and correlation with onshore saucer-shaped intrusions of different size suggest that they are internally connected and fed by each other from deeper to shallower levels. We argue for a nested emplacement mechanism and against a controlling role by the overlying sedimentary basin as the saucer-shaped intrusions are emplaced in both the sedimentary rocks as well as in the underlying crystalline basement. The interplay between magma pressure and overburden pressure, as well as the, at the time, ambient stress regime, are responsible for their extensive extent and rather constant thicknesses (c. 100-300 m). Saucer-shaped intrusions may therefore be present elsewhere in the crystalline basement to the same extent as observed in this study some of which are a significant source of raw materials.
  •  
15.
  • Burchardt, Steffi, et al. (författare)
  • Erupted frothy xenoliths may explain lack of country-rock fragments in plutons
  • 2016
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Magmatic stoping is discussed to be a main mechanism of magma emplacement. As a consequence of stoping, abundant country-rock fragments should occur within, and at the bottom of, magma reservoirs as "xenolith graveyards", or become assimilated. However, the common absence of sufficient amounts of both xenoliths and crustal contamination have led to intense controversy about the efficiency of stoping. Here, we present new evidence that may explain the absence of abundant country-rock fragments in plutons. We report on vesiculated crustal xenoliths in volcanic rocks that experienced devolatilisation during heating and partial melting when entrained in magma. We hypothesise that the consequential inflation and density decrease of the xenoliths allowed them to rise and become erupted instead of being preserved in the plutonic record. Our thermomechanical simulations of this process demonstrate that early-stage xenolith sinking can be followed by the rise of a heated, partially-molten xenolith towards the top of the reservoir. There, remnants may disintegrate and mix with resident magma or erupt. Shallow-crustal plutons emplaced into hydrous country rocks may therefore not necessarily contain evidence of the true amount of magmatic stoping during their emplacement. Further studies are needed to quantify the importance of frothy xenolith in removing stoped material.
  •  
16.
  •  
17.
  • Burchardt, Steffi, et al. (författare)
  • Sinking of anhydrite blocks within a Newtonian salt diapir : modelling the influence of block aspect ratio and salt stratification
  • 2012
  • Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 188:3, s. 763-778
  • Tidskriftsartikel (refereegranskat)abstract
    • 2-D Finite Differences models are used to analyse the strain produced by gravity-driven sinking of dense rectangular inclusions through homogeneous and vertically stratified Newtonian salt. We systematically modelled the descent of dense blocks of different sizes and initial orientations (aspect ratios) representing the Main Anhydrite fragments documented within, for example, the Gorleben salt diapir. Model results demonstrate that size of the blocks is a governing parameter which dictates the amount of strain produced within the block and in the surrounding host salt. Initial block orientation (aspect ratio), on the other hand, causes fundamental differences in block deformation, while the resulting structures produced in the salt are principally the same in all models with homogeneous salt, covering shear zones and folding of passive markers. In models with vertically stratified salt with different viscosities, block descent takes place along complex paths. This results from greater strain accommodation by the salt formation with the lowest viscosity and an asymmetrical distribution of initial vertical shear stresses around the block. Consequently, in these models, block strain is lower compared with the models with homogeneous salt (for the same viscosity as the high-viscosity salt), and sinking is accompanied by block rotation. The latter causes diapir-scale disturbance of the pre-sinking salt stratigraphy and complex sinking paths of the blocks. In particular, vertically oriented blocks sink into high-viscosity salt and drag with them some low-viscosity salt, while horizontal blocks sink in the low-viscosity salt. The resultant sinking velocities vary strongly depending on the sinking path of the block. Based on model results and observed structural configuration within the Gorleben salt diapir, we conclude that the internal complexity of a salt diapir governs its post-ascent deformation. Salt structure and its interaction with dense blocks should hence be considered in the assessment of the long-term stability of storage sites for hazardous waste.
  •  
18.
  • Burchardt, Steffi, et al. (författare)
  • Strain pattern within and around denser blocks sinking within Newtonian salt structures
  • 2011
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 33:2, s. 145-153
  • Tidskriftsartikel (refereegranskat)abstract
    • Blocks of dense material, such as anhydrite, entrained in salt structures have been proposed to sink through their host material. Here, we present the results of numerical models that analyse strain patterns within and around initially horizontal anhydrite blocks (viscosity 10(21) Pa s) sinking through Newtonian salt with a viscosity of 10(17) Pa s. In addition, the influence of the block aspect ratio (thickness to width ratio; AR) is analysed. The model results show that the blocks are folded and marginally sheared to approach streamlined shapes. The effectiveness of this process is a function of the block AR and influences the sinking velocity of the blocks significantly. Final sinking velocities are in the range of ca. 1.7 -3.1 mm/a. Around the block in the salt, an array of folds and shear zones develops during block descent, the structure of which is principally the same independent of the block AR. However, the size and development of the structures is a function of the block size. Monitoring of strain magnitudes demonstrates that the salt is subject to extremely high strains with successively changing stress regimes, resulting in closely-spaced zones of high adjacent to low strain. In comparison to the anhydrite blocks, strain magnitudes in the salt are up to one order of magnitude higher.
  •  
19.
  • Burchardt, Steffi, et al. (författare)
  • The influence of viscosity contrasts on the strain pattern and magnitude within and around dense blocks sinking through Newtonian salt
  • 2012
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 35, s. 102-116
  • Tidskriftsartikel (refereegranskat)abstract
    • Dense inclusions in salt cover a wide range of materials and therefore material properties, depending on their origin. We have modelled the deformation associated with gravity-driven sinking of horizontal, initially rectangular blocks of dense material through Newtonian salt. Our two-dimensional Finite Differences models analyse the influence and interaction of two parameters: (1) the size, i.e. the aspect ratio (AR), of the block and (2) the viscosity contrast between the salt and the more viscous block over four orders of magnitude. The results demonstrate that during gravity-driven sinking the blocks are folded and sheared. The strain magnitude within the block increases with increasing block AR and decreases with increasing viscosity contrast. Sinking velocities of the blocks are in the range of <2 and >6 mm a−1 and are a function of block and salt deformation that depend on the block mass and AR, as well as on the viscosity contrast. Salt deformation is characterised by the development of an array of characteristic structures that include folds and shear zones, as well as a zone characterised by extreme vertical stretching above the block, termed entrainment channel. Strain in the salt is locally more than two orders of magnitude higher than in the block and increases with increasing block AR and viscosity contrast. Salt deformation is distributed in closely-spaced high- and low-strain zones concentrated in the block vicinity and the entrainment channel.
  •  
20.
  • Burliga, Stanislaw, et al. (författare)
  • Modelling cover deformation and decoupling during inversion, using the Mid-Polish Trough as a case study
  • 2012
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 42, s. 62-73
  • Tidskriftsartikel (refereegranskat)abstract
    • Seismic sections across the NW part of the Polish Basin show that thrust faults developed in the sedimentary units above the Zechstein evaporite layer during basin inversion. These cover thrust faults have formed above the basement footwall. Based on the evolution of the basin, a series of scaled analogue models was carried out to study interaction between a basement fault and cover sediments during basin extension and inversion. During model extension, a set of normal faults originated in the sand cover above the basement fault area. The distribution and geometry of these faults were dependent on the thickness of a ductile layer and pre-extension sand layer, synkinematic deposition, the amount of model extension, as well as on the presence of a ductile layer between the cover and basement. Footwall cover was faulted away from the basement only in cases where a large amount of model extension and hanging-wall subsidence were not balanced by synkinematic deposition. Model inversion reactivated major cover faults located above the basement fault tip as reverse faults, whereas other extensional faults were either rotated or activated only in their upper segments, evolving into sub-horizontal thrusts. New normal or reverse faults originated in the footwall cover in models which contained a very thin pre-extension sand layer above the ductile layer. This was also the case in the highly extended and shortened model in which synkinematic hanging-wall subsidence was not balanced by sand deposition during model extension. Model results show that inversion along the basement fault results in shortening of the cover units and formation of thrust faults. This scenario happens only when the cover units are decoupled from the basement by a ductile layer. Given this, we argue that the thrusts in the sedimentary infill of the Polish Basin, which are decoupled from the basement tectonics by Zechstein evaporites, developed due to the inversion of the basement faults during the Late Cretaceous-Early Tertiary. (C) 2012 Elsevier Ltd. All rights reserved.
  •  
21.
  • Carboni, F., et al. (författare)
  • Modelling the 4D kinematics of extensional structures developed above discontinuous inclined ductile basal detachments
  • 2022
  • Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 157
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of scaled analogue models were used to a preliminary study on the influence of the basal detachment configuration on the evolution of extensional systems, developed above an inclined basal ductile detachment. Three different basal configurations were aimed to test extension above: i) a homogeneously distributed ductile detachment; ii) two sectors with a different distribution of the ductile detachment, separated by an abrupt, transversal boundary; ii) a laterally variable width of the ductile detachment, driven by an abrupt oblique boundary. Fault activity was monitored through a series of digital elevation models obtained from the laser scanning of the models' surface. Results of the models analysis show how the geometry, the distribution, the kinematic, and the timing of faulting is strongly controlled by the geometry and orientation of the ductile-brittle interface in respect to the extension direction. Faults close to the brittle-ductile interface develop following the interface geometry, whose effect is reduced moving away from it. In addition, we observe a major number of faults which accommodates lower amount of extension and are less closely spaced above longer ductile detachments. Our results can be compared with natural case-histories along continental passive margins, where extension occurs above a dipping salt detachment, with inhomogeneous distribution (e.g., the northern Gulf of Mexico, central Brazilian margin, Angola margin).
  •  
22.
  • Carrillo, Emilio, et al. (författare)
  • Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)
  • 2017
  • Ingår i: Marine and Petroleum Geology. - : Elsevier. - 0264-8172 .- 1873-4073. ; 86, s. 1310-1326
  • Tidskriftsartikel (refereegranskat)abstract
    • We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as decollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main decollement levels of the so-called Cadi thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as decollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins. (C) 2017 Elsevier Ltd. All rights reserved.
  •  
23.
  • Chemia, Zurab, 1979- (författare)
  • Modeling internal deformation of salt structures targeted for radioactive waste disposal
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis uses results of systematic numerical models to argue that externally inactive salt structures, which are potential targets for radioactive waste disposal, might be internally active due to the presence of dense layers or blocks within a salt layer.The three papers that support this thesis use the Gorleben salt diapir (NW Germany), which was targeted as a future final repository for high-grade radioactive waste, as a general guideline.The first two papers present systematic studies of the parameters that control the development of a salt diapir and how it entrains a dense anhydrite layer. Results from these numerical models show that the entrainment of a dense anhydrite layer within a salt diapir depends on four parameters: sedimentation rate, viscosity of salt, perturbation width and the stratigraphic location of the dense layer. The combined effect of these four parameters, which has a direct impact on the rate of salt supply (volume/area of the salt that is supplied to the diapir with time), shape a diapir and the mode of entrainment. Salt diapirs down-built with sedimentary units of high viscosity can potentially grow with an embedded anhydrite layer and deplete their source layer (salt supply ceases). However, when salt supply decreases dramatically or ceases entirely, the entrained anhydrite layer/segments start to sink within the diapir. In inactive diapirs, sinking of the entrained anhydrite layer is inevitable and strongly depends on the rheology of the salt, which is in direct contact with the anhydrite layer. During the post-depositional stage, if the effective viscosity of salt falls below the threshold value of around 1018-1019 Pa s, the mobility of anhydrite blocks might influence any repository within the diapir. However, the internal deformation of the salt diapir by the descending blocks decreases with increase in effective viscosity of salt.The results presented in this thesis suggest that it is highly likely that salt structures where dense and viscous layer/blocks are present undergo an internal deformation processes when these dense blocks start sinking within the diapir. Depending on size and orientation of these blocks, deformation pattern is significantly different within the diapir. Furthermore, model results applied to the Gorleben diapir show that the rate of descent of the entrained anhydrite blocks differs on different sides of the diapir. This suggests that if the anhydrite blocks descent within the Gorleben diapir, they initiate an asymmetric internal flow within it.
  •  
24.
  • Chemia, Zurab, et al. (författare)
  • The control of salt supply on entrainment of an anhydrite layer within a salt diapir
  • 2008
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 30:9, s. 1192-1200
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of four parameters (sedimentation rate, viscosity of salt, stratigraphic location of the anhydrite layer within the salt layer, and the perturbation width) on salt supply to down-built diapirs and its entrainment capacity are studied systematically in numerical models. Model results show that these four parameters affect salt supply, and the evolution history of a salt diapir. As such, these parameters strongly influence the style and the amount of entrainment of dense inclusions into a diapir. In active diapirs (i.e. unburied diapirs), salt supply increases with increasing sedimentation rate whereas it decreases with an increase in salt viscosity. Diapirs initiating from wide perturbation provide more salt supply to feed the diapir. Presence and initial stratigraphic location of any denser layer (e.g. an anhydrite layer) within a salt layer also affects salt supply. When lateral forces are negligible, salt supply into a diapir depends on these four parameters, which directly control the entrainment of any embedded anhydrite layer into the diapir.
  •  
25.
  •  
26.
  • Cruciani, F., et al. (författare)
  • Kinematic evolution of a regional-scale gravity-driven deepwater fold-and-thrust belt : The Lamu Basin case-history (East Africa)
  • 2017
  • Ingår i: Tectonophysics. - : ELSEVIER SCIENCE BV. - 0040-1951 .- 1879-3266. ; 712-713, s. 30-44
  • Tidskriftsartikel (refereegranskat)abstract
    • The deepwater fold-and-thrust belts (DWFTBs) are geological structures recently explored thanks to advances in offshore seismic imaging by oil industry. In this study we present a kinematic analysis based on three balanced cross-sections of depth-converted, 2-D seismic profiles along the offshore Lamu Basin (East African passive margin). This margin is characterized by a regional-scale DWFTB (>450 km long), which is the product of gravity-driven contraction on the shelf that exhibits complex structural styles and differing amount of shortening along strike. Net shortening is up to 48 km in the northern wider part of the fold-and-thrust belt (approximate to 180 km), diminishing to <15 km toward the south, where the belt is markedly narrower (approximate to 50 km). The three balanced profiles show a shortening percentage around 20% (comparable with the maximum values documented in other gravity-driven DWFTBs), with a significant variability along dip: higher values are achieved in the outer (i.e. down-dip) portion of the system, dominated by basinward-verging, imbricate thrust sheets. Fold wavelength increases landward, where doubly-verging structures and symmetric detachment folds accommodate a lower amount of shortening. Similar to other cases, a linear and systematic relationship between sedimentary thickness and fold wavelength is observed. Reconstruction of the rate of shortening through time within a fold-and-thrust belt shows that after an early phase of slow activation (Late Cretaceous), >95% of net shortening was produced in <10 Myr (during Paleocene). During this acme phase, which followed a period of high sedimentation rate, thrusts were largely synchronous and the shortening rate reached a maximum value of 5 mm/yr. The kinematic evolution reconstructed in this study suggests that the structural evolution of gravity-driven fold-and-thrust belts differs from the accretionary wedges and the collisional fold-and-thrust belts, where thrusts propagate in-sequence and shortening is uniformly accommodated along dip.
  •  
27.
  • Cruden, A.R., et al. (författare)
  • Diapiric basal entrainment of mafic into felsic magma.
  • 1995
  • Ingår i: Earth and Planetary Science Letters. - 0012-821X. ; 131:3-4, s. 321-340
  • Tidskriftsartikel (refereegranskat)abstract
    • One consequence of partial melting of the lower crust by heat transfer from a mantle-derived underplate is that the resultant buoyant, felsic magma layer (density ϱ2, viscosity μ2, thickness h2) will overllie a denser mafic layer (density ϱ3, viscosity μ3, thickness h3, which can be fully liquid to completely solid, depending on its thermal history. Laboratory experiments and finite-difference numerical models have been used to determine the conditions that favour the entrainment of the mafic layer into the overlying felsic magma as it ascends diapirically. Large amounts of entrainment occur when (where ϱ1 is the density of the crust), , and . When these conditions occur, the buoyancy and viscous effects acting to maintain the stability of the felsic-mafic layer interface are minimized. The role of m is much more important in the diapiric entrainment phenomenon than in the comparable problem of axial withdrawal from a density- and viscosity-stratified magma chamber with rigid walls.Favourable conditions for entrainment are likely to occur during the evolution of many lower crustal felsic magma source regions with a mafic underplate. Low amounts of entrainment result in minimal interaction (i.e., mixing) between the felsic host and entrained mafic material. If a large amount of entrainment occurs, our models combined with other studies show that mafic magma can remain in the centre of the conduit (low to high Reynolds number (Re), m ≈ 1), become fully mixed with the felsic host (high Re, low m), or become encapsulated by the felsic magma (low Re, m < 0.6). Such mechanical processes may account for the textural and compositional complexity shown by some plutons.
  •  
28.
  • Deng, Bin, et al. (författare)
  • Modelling asymmetric deformation along a curved strike-slip basement-fault system
  • 2021
  • Ingår i: International journal of earth sciences. - : Springer. - 1437-3254 .- 1437-3262. ; 110, s. 165-182
  • Tidskriftsartikel (refereegranskat)abstract
    • Large-scale curved strike-slip fault systems along which significant amounts of displacement have taken place are common in nature. Scaled analogue experiments were used in this study to investigate strike-slip deformation in cover units above a curved basement-fault system simulated by a rigid plate with an in-built curvature depicting a half-circular fault. The model results show that en-echelon, right-stepping Riedel shears and low-angle synthetic shears (Y-shears) always form at the beginning of deformation, and grow outwards with splay faults, most of which evolve into thrusts at later stages of deformation. Digital image correlation (DIC) analyses of the surface displacement vectors show that a diffuse zone of deformation progressively changes into en-echelon shears, which gradually develop into throughgoing shear zones with further deformation. The geometries of Riedel shears along two sides of the basement fault (i.e. concave and convex sides) show significant differences in fault shape and intersection angles between the faults and the curved basement fault, indicating an asymmetry in deformation with a much wider deformation zone occurring on the concave side. As a result, en-echelon and/or overlapping flower structures develop along the curved basement strike-slip fault system. In particular, Riedel shears with a upward-convex geometry are localised in both sides of the curved basement fault and a continuous reverse oblique-slip fault forms at the concave side. When compared with the geometry of curved strike-slip faults in nature (e.g. the Daliangshan shear zone in Xichang basin and the Red River shear zone in the Yinggehai basin, China) the model results depict the asymmetric evolution pattern of the faults on either side of curved basement faults.
  •  
29.
  • Deng, Hongling, et al. (författare)
  • Identifying the characteristic signatures of fold-accommodation faults
  • 2013
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 56, s. 1-19
  • Tidskriftsartikel (refereegranskat)abstract
    • Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation-distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation-distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation-distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults.
  •  
30.
  • Deng, Hongling, 1983-, et al. (författare)
  • Mega arrowhead interference pattern in the Central part of the Yanshan Orogenic Belt, North China
  • 2015
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 80, s. 25-37
  • Tidskriftsartikel (refereegranskat)abstract
    • The Chengde-Pingquan region is located in the central part of the Yanshan Orogenic Belt (YOB). At Daheishan and Pingquan in the central YOB, thrusts and folds of variable trends are displayed in 2 km-scale fold interference patterns. Detailed field mapping was conducted to decipher the geometry of these two superimposed structures. Map-view geometry and stereonet plots for outcrop-scale folds indicate that the superimposed structures form arrowhead interference pattern where NW-SE-trending F1 folds are refolded by later ENE-WSW F2 folding. After remove the effects of later faulting, restored map-views of the superimposed structures show that when the F1 folds have inclined axial surfaces but with no an overturned limb, an arrowhead interference pattern (here called modified type-2 pattern) can form. Our field data and reinterpretation of the findings of previous studies suggest that five major shortening phases have occurred in the Chengde-Pingquan region. The first two phases, which formed the superimposed folds, occurred earlier than the Late Triassic (D1) and during the Late Triassic to Early Jurassic (D2). These two phases were followed by three deformation phases that are mainly characterized by thrusting and strike-slip faulting, which strongly modified the large-scale fold interference patterns.
  •  
31.
  • Deng, Hongling, et al. (författare)
  • Modeling two sequential coaxial phases of shortening in a foreland thrust belt
  • 2014
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 66, s. 400-415
  • Tidskriftsartikel (refereegranskat)abstract
    • Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate decollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.
  •  
32.
  • Deng, Hongling, 1983-, et al. (författare)
  • Superimposed folding and thrusting by two phases of mutually orthogonal or oblique shortening in analogue models
  • 2016
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 83, s. 28-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Orogens may suffer more than one phase shortening resulting in superposition of structures of different generations. Superimposition of orthogonal or oblique shortening is studied using sandbox and centrifuge modelling. Results of sand models show that in orthogonal superimposition, the two resulting structural trends are approximately orthogonal to each other. In oblique superimposition, structures trend obliquely to each other in the relatively thin areas of the model (foreland), and mutually orthogonal in areas where the model is thickened during the first phase of shortening (i.e. the hinterland). Thrusts formed during the first shortening phase may be reactivated during the later shortening phase. Spacing of the later phase structures is not as wide as expected, considering they across the pre-existing thickened wedge. Superposition of structures results in formation of type 1 fold interference pattern. Bedding is curved outwards both in the dome and basin structures. Folded layers are dipping and plunging outwards in a dome, while they are dipping and plunging inwards in a basin. In the areas between two adjacent domes or basins (i.e. where an anticline is superimposed by a syncline or a syncline is superimposed by an anticline), bedding is curved inwards, and the anticlines plunge inwards and the synclines outwards. The latter feature could be helpful to determine the age relationship for type 2 fold interference pattern. In tectonic regions where multiple phases of shortening have occurred, the orogenic-scale dome-and-basin and arrowhead-shaped interference patterns are commonly formed, as in the models. However, in some areas, the fold interference pattern might be modified by a later phase of thrusting. Similar to models results, superimposition of two and/or even more deformation phases may not be recorded by structures all over the tectonic area.
  •  
33.
  • Deng, Hongling, 1983- (författare)
  • Superimposition of Contractional Structures in Models and Nature
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Superimposition of contractional structures is widely observed in different scales in the world. Superimposed structures form due to different processes: change in strain accommodation from one type of structure to another during a single progressive shortening; successive coaxial shortening phases separated by an unconformity; superimposition of different non-coaxial shortening phases. Using results of a series of systematic analogue models and detailed field structural mapping, this thesis focuses on the geometry and kinematics of such superimposed structures that are formed by these three processes. During a single progressive folding, thrusts develop within a fold to accommodate stain variations in different regime of the fold. Limited displacement along these thrusts does not significantly modify the geometry of the fold. However, during multiple shortening phases (coaxial or non-coaxial), early formed structures are modified by the later phase ones. The later thrusts can cut and displace the pre-existing structures. The early folds are tightened or interfered by the later folding phase. Pre-existing thrusts may be reactivated either in dip direction and/or along strike during the later shortening. The pre-existing structures in turn influence development of the later structures, which results in change in structure spacing. An angular unconformity between two shortening phases clearly truncates the early phase structures and separates structures of different levels. Unlike in the post-erosional layers, in the layers below the unconformity, complicated superimposed structures are visible. This thesis shows that geometry and sequence of structures formed during one progressive shortening or multiple shortening phases strongly depend on the mode of the superimposition (coaxial, orthogonal or oblique) and the orientation of pre-existing structures.
  •  
34.
  • Dietl, Carlo, et al. (författare)
  • Centrifuge modelling of plutons intruding shear zones : application to the Fürstenstein Intrusive Complex (Bavarian Forest, Germany)
  • 2006
  • Ingår i: Geodinamica Acta. - : Informa UK Limited. - 0985-3111 .- 1778-3593. ; 19:3-4, s. 165-184
  • Tidskriftsartikel (refereegranskat)abstract
    • Models consisting of a thick overburden resting on a buoyant layer were sheared and centrifruged in order to study the relationship between strike-slip shear zones and intrusions of buoyant material. Three experiments were carried out: In model 1, where the overburden consisted of a viscous material, no diapirs formed even after shearing for 40 mm (gamma = - 1.07) and 27 min centrifuging. In models 2 and 3, where the overburden was semi-brittle, prescribed cuts at two different orientations (model 2: parallel to sigma 1; model 3: perpendicular to sigma 1) were initiated in the overburden in order to see whether such cuts acted as pathways for intrusion. In model 2 the prescribed cuts were used by the buoyant material as pathways when the cuts opened during shearing. Continued shearing widened the cuts and allowed the buoyant material to extrude on the surface of the model forming a coalesced elliptical sheet. In model 3. the cuts were closed during shearing and prevented the intrusion of the buoyant material. During further shearing, the Cuts rotated and activated as strike-slip faults bounding pull-apart basins. Such pull-apart basins were not deep enough to tap the buoyant material. Nevertheless, the results of the experiments suggest that magma ascends in shear zones not as diapirs, but rises along preexisting pathways as dykes. Model results were used to evaluate emplacement of the Furstenstein Intrusive Complex (FIC) in the Bavarian Forest, whose magnetic and structural inventory have been investigated in detail. The pluton consists of 5 magma batches, each with distinct magnetic fabrics. which are interpreted as the result of magma intrusion along opening and rotating tension gashes within the BPSZ stress field. Shear failure of the crust in the FIC area due to thermomechanical weakening provided the space for the emplacement of the last and biggest granite magma batch. Overall, the emplacement history of the FIC fits perfectly with the observations made during experiment 2 and indicates that magma ascent in shear zones is bound to tension gashes.
  •  
35.
  •  
36.
  • Dietl, Carlo, et al. (författare)
  • Emplacement of nested diapirs : Results of centrifuge modelling.
  • 2002
  • Ingår i: Journal of the Virtual Explorer. - : Virtual Explorer Pty Ltd.. - 1441-8142. ; 7, s. 79-86
  • Tidskriftsartikel (refereegranskat)abstract
    • Concentrically expanded plutons (CEPs) are a common igneous feature. They are characterized by compositional zoning, mainly concentric magmatic fabric inside the pluton and ductile fabric in the contact aureole which are concordant with the pluton / host rock contact. Two intrusion mechanisms have been proposed for CEPs: dyking + ballooning and diapirism. Here, we present results of a centrifuge model to study the kinematics and dynamics of CEPs. The model consisted of three layers from bottom to the top; a 5 mm thick buoyant lower layer of Rhodorsil Gomme simulating a partially molten magma, a 50 mm thick non-Newtonian Rhodorsil Gomme + Plastilina overburden simulating a natural silicic overburden and a 10 mm thick layer of PDMS simulating a less dense overburden. The model was centrifuged twice with two differently stained buoyant layers attached. After the first stage of the experiment two mushroom-shaped diapirs had intruded and deformed the overburden to spread below the less-dense PDMS layer. The second-stage intrusion occurred along the stem of the preexisting diapirs using them as a mechanically weak pathway. This intrusion was not diapiric, but the buoyant material rose passively similar to a dike. Once reaching the level of neutral buoyancy, the intrusive material spread laterally resulting in extensive spreading and expansion of the overhang of the preexisting diapirs. Model results show that CEPs can be the result of combined initial diapirism and subsequent dyking. Multiple diapirs can form only when the overburden units deform ductiley during the different stages of diapirism.
  •  
37.
  • Dietl, Carlo, et al. (författare)
  • Formation of tabular plutons : results and implications of centrifuge modelling
  • 2008
  • Ingår i: Journal of geosciences. - : Czech Geological Society. - 1802-6222 .- 1803-1943. ; 53:3-4, s. 253-261
  • Tidskriftsartikel (refereegranskat)abstract
    • Geophysical investigations reveal that many granitoid plutons possess a tabular shape: either laccolithic, lopolithic or phacolithic. In this study, the results of a centrifuge experiment are used to understand the formation mechanisms of these features. The model was build of a sequence of 14 differently coloured plasticine layers. Two buoyant layers - with a volume of c. 40 cm(3) each - were incorporated into the model stratigraphy at different depths to investigate, whether the rise and emplacement of buoyant material at different levels results in different intrusion structures. After centrifuging for 30 min at 700 G, both the buoyant layers had formed two lenticular sills (phacoliths) with aspect ratios (length/thickness) of 6 and 3.4 for the upper and lower phacoliths, respectively, directly above both pre-existing perturbations in the buoyant layers. During their movement, the buoyant phacoliths had pushed their roof plasticine upward. Simultaneously, their floor plasticine had subsided (bottom sinking). Subsidence of the floor material had choked the inflow of further buoyant material into the feeder channel of the developing sills and inhibited their further lateral growth. The observed forced downward movement of the plasticine floor of the forming PDMS (polydimethylsiloxane) phacoliths resembles the so-called "floor depression" of host rock material around an emplacing tabular pluton. Floor depression is supposed to be a very important vertical material transfer process, which provides space for the construction of lopo- and phacoliths. The subsidence of host material made space for the developing buoyant phacoliths, but also restricted their growth to a certain time slot before the influx of new buoyant material into the feeder dyke of the tabular intrusive body was shut off. Similarly, in nature, the growth of a tabular pluton might be limited not only by the rate of magma ascent and its physical properties, but also by the emplacement processes of the evolving pluton.
  •  
38.
  • Dietl, C., et al. (författare)
  • Sheets within diapirs - Results of a centrifuge experiment
  • 2011
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 33:1, s. 32-37
  • Tidskriftsartikel (refereegranskat)abstract
    • We carried out a centrifuge experiment to model the diapiric rise of a stratified PDMS layer from three perturbations through a non-Newtonian, ductile overburden. The experiment carried out at 700 g resulted in three composite diapirs fed by different PDMS layers. The three resulting diapirs represent two different stages of diapirism. One of the diapirs (diapir 1), which reached its level of neutral buoyancy and extruded at the surface of the model, was tabular in profile and copied by an internal intrusive body. The other two diapirs (diapirs 2 and 3) were still in the ascending stage when centrifuging was stopped and thus did not extrude at the surface. They displayed a typical balloon-on-string geometry, which develops at a high viscosity contrast between a highly viscous overburden and a less viscous buoyant material. The internal geometry of these last two diapirs, fed by the lower impure PDMS, however, did not copy the shape of their precursors. Instead, they had a finger-like shape. The finger geometry of the internal part of the diapirs might be the result of the higher viscosity of the impure lower PDMS intruding a less viscous clean PDMS. Compared to nature, diapir 1 represents a fully developed concentrically expanded pluton or nested diapir, while diapirs 2 and 3 resemble composite plutons which host magma batches of dyke-like geometry. Based on the results of our experiment we suggest that truly concentrically expanded plutons develop from the latter.
  •  
39.
  •  
40.
  •  
41.
  • Engström, Anna, 1975- (författare)
  • Deformation and fluid-flow in magma-poor margins : A study of the Tasna Ocean-Continent transition, SE Switzerland
  • 2006
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this study, interaction between fluids and deformation during the final stages of magma-poor rifting was investigated. The Tasna Ocean-Continent transition, located in the Swiss Alps, was studied and a large data set was obtained from profiles oriented perpendicular to two detachment faults. One of these juxtaposed serpentinized mantle against continental crust and the other exhumed both mantle and continental crust to the seafloor. Deformation associated with detachment faulting showed many common features but also some phenomena which were unique to each fault, confirming their sequential activity and differing roles in the exhumation process. Oxygen isotopes indicated the presence of both pervasive and channeled fluid phases, either accompanying or post-dating serpentinization. Deformation in the fault zone occurred in previously serpentinized mantle indicating that serpentinization pre-dated final exhumation. Most strain localization and displacement occurred in fault cores which are narrow zones beneath the detachments. These are underlain by wide zones characterized by more distributed strain. Transitional fabrics as well as reactivated and/or overprinted deformation structures indicated that the final phase of rifting is complex. Fault cores acted as fluid conduits or barriers. Thus, the most deformed zones may become the least permeable. Hence the coupling between deformation and fluid flow is complex in a study area subjected to several phases of deformation and fluid flow. Finally the importance of serpentinization in the evolution of magma-poor rifting was investigated. It was found that serpentinization is the consequence rather than the reason for strain localization at magma-poor margins. However, serpentinization may be an important process which can accelerate exhumation rates in the very latest stages of magma-poor rifting. The pre-existing deformation history of the crust may also be of importance for the development and location of margins.
  •  
42.
  • Farzipour-Saein, A., et al. (författare)
  • Basin evolution in the Lurestan region of the Zagros fold-and-thrust belt, Iran
  • 2009
  • Ingår i: Journal of Petroleum Geology. - : Wiley. - 0141-6421 .- 1747-5457. ; 32:1, s. 5-19
  • Tidskriftsartikel (refereegranskat)abstract
    • The evolution of the central part of the Lurestan region in the Zagros fold-and-thrust belt has been studied using newly generated isopach maps for different time intervals between the Late Cretaceous and the Miocene. The study was based on existing geological maps, gravity data, measured stratigraphic surface sections, original field work and well data. Understanding the processes which have influenced facies and thickness variations in the study area will have a significant impact on future hydrocarbon exploration. Cenomanian carbonates assigned to the Sarvak Formation, the main reservoir unit in the study area, are composed of both pelagic and neritic facies. These facies occur along the roughly north-south trending "Anaran lineament", interpreted to represent a palaeohigh, which influenced patterns of sedimentation in the Cretaceous-Tertiary. The palaeohigh formed as a result of the reactivation of a basement lineament in the Late Cretaceous. The continuing influence of this lineament on patterns of sedimentation during Oligocene - early Miocene time is indicated by a range of evidence including the presence of clinoform geometries. Analysis of sedimentary thicknesses in the Zagros foreland basin between the Late Cretaceous and the early Miocene indicates progressive SWward migration of the depocentre. Late Cretaceous ophiolite obduction and plate margin convergence exerted a major influence on stratigraphic architecture, and controlled depocentre migration and foreland basin evolution.
  •  
43.
  • Farzipour-Saein, Ali, et al. (författare)
  • Effect of lateral thickness variation of an intermediate decollement on the propagation of deformation front in the Lurestan and Izeh zones of the Zagros fold-thrust belt, insights from analogue modeling
  • 2014
  • Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 65, s. 17-32
  • Tidskriftsartikel (refereegranskat)abstract
    • Although the role of various basal decollement levels on structural style and deformation propagation is well documented in many folded belts, the effect of lateral variation in intermediate decollements is poorly constrained. This work uses results of three scaled sand-box models shortened from one end to study the variation in structural development between areas with a ductile intermediate decollement and areas without (or with a thinner) intermediate decollement. Combined results of scaled models with field observations are used to argue that the presence of mechanically different intermediate decollement horizons within the Zagros stratigraphy has resulted in deformation partitioning between the Lurestan and Izeh zones. A thick intermediate decollement facilitates a faster propagation of deformation front and a lower taper in comparison with a thinner (or non-existing) intermediate decollement during compression. However, the effect of lateral thickness variation in the intermediate decollement on propagation of deformation is less profound than the effect of mechanical differences in basal decollements. 
  •  
44.
  • Farzipour-Saein, Ali, et al. (författare)
  • Intermediate decollement activation in response to the basal friction variation and its effect on folding style in the Zagros fold-thrust belt, an analogue modeling approach
  • 2016
  • Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 687, s. 56-65
  • Tidskriftsartikel (refereegranskat)abstract
    • Although the role of various basal and intermediate decollement levels on structural style is well documented individually in many folded terrains, the interaction between basal and intermediate decollements is poorly constrained. This study uses results of two scaled sand-box models shortened from one end to study the variation in structural development in response to varying basal friction and its consequent interaction with intermediate decollement horizons. Two models with similar incompetent intermediate decollement, but with different basal friction (with and without a thick basal decollement), were prepared analogous for the eastern and the western parts of the Razak basement fault in the Fars Region of the eastern part of the Zagros fold thrust belt (ZFTB). Combined results of scaled models with geological observations are used to argue that the basal decollement friction characteristics govern propagation of deformation front. In addition, model results, analogues to north-south direction, show that deformation complexity and disharmonic folding exist in the section where the intermediate decollement has been activated in response to the shortening without the basal decollement (throughout the western part of the Razak basement fault where less thickness of the Hormuz series as the basal decollement has been documented compared to its eastern part). In other words, the complexity in deformation is less portrayed along sections where basal friction beneath the model decreases (e.g. the eastern part of the Razak basement fault). We argue here that, in addition to other parameters (not presented in this study) interaction of intermediate decollement levels with basal decollement friction characteristics could explain decoupling between structures within the sedimentary column of the Fars Region of the eastern part of the Zagros fold thrust belt.
  •  
45.
  • Farzipour-Saein, Ali, et al. (författare)
  • The effect of basement step/topography on the geometry of the Zagros fold and thrust belt (SW Iran) : an analogue modeling approach
  • 2013
  • Ingår i: International journal of earth sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 102:8, s. 2117-2135
  • Tidskriftsartikel (refereegranskat)abstract
    • Systematic analogue models are run to study the variation in deformation across basement steps in the Zagros Fold-Thrust Belt. Our model results demonstrate that basement configuration/topography influences the sedimentation thickness and, hence, the kinematics and geometric evolution of the fold and thrust belt. The greater the difference in thickness between the adjacent cover units across a basement step, the sharper and clearer will be the offset the deformation front. Based on model results, we conclude that in a fold-thrust belt, where basement step/topography is covered by a layer of ductile salt acting as a decollement, the effect of the salt decollement on the evolution of the belt is far greater than the effect of thickness variation of the cover units.
  •  
46.
  • Feng, Qianqian, et al. (författare)
  • Thermo-Kinematic Constraints on Restoration of the Eastern Sichuan Fold-And-Thrust Belt, South China
  • 2023
  • Ingår i: Tectonics. - : American Geophysical Union (AGU). - 0278-7407 .- 1944-9194. ; 42:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Kinematic restoration of the eastern Sichuan fold-and-thrust belt (ESFTB) in South China is calibrated with a new thermo-kinematic model combining analog models, discrete element method, and thermochronology data. Thermo-kinematic analysis provides constraints on the onset, rate, and lateral variation of deformation and exhumation. Results show that the ESFTB experienced a northwestward thrusting and periodic exhumation. Its evolution was characterized by five major stages based on the deformation characteristics; (a) Shortening above a basal decollement and formation of large imbricates separated by narrow synclines during 170-130 Ma; (b) Transition stage during 130-100 Ma; (c) Stepping up of deformation to shallow decollement levels and shaping of the thick-skinned domain during 100-70 Ma; (d) Shaping of the thin-skinned domain during 70-20 Ma; and (e) Continuous exhumation and structural modification from 20 Ma to present. The changes in the exhumation rate have been tectonic responses to the subduction retreat of the Paleo-Pacific Plate and the eastward growth of the Tibetan Plateau. The westward subduction of the Paleo-Pacific Plate resulted in northwestward shortening across South China, progressive deformation of the ESFTB, and rapid exhumation from the Late Jurassic to the Late Cretaceous. The crustal extension associated with the rollback of the Paleo-Pacific slab accounted for the Mesozoic exhumation rate decrease until the Miocene. The accelerated cooling of the thin-skinned domain of the ESFTB since the Miocene was a response to the eastward growth of the Tibetan Plateau, while the continuous slow exhumation in the thick-skinned domain was related to the continuous crustal extension in South China. New thermo-kinematic method combining analog modeling, discrete element method, balanced reconstruction, and thermochronology dataEastern Sichuan fold-and-thrust belt (ESFTB) experienced northwestward thrusting and periodic exhumation and its evolution can be subdivided into five stagesExhumation rate changes are responses of ESFTB to subduction retreat of the Paleo-Pacific Plate and eastward growth of the Tibetan Plateau
  •  
47.
  • Fuchs, Lukas, et al. (författare)
  • Numerical modeling of the effect of composite rheology on internal deformation in down-built diapirs.
  • 2015
  • Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 646, s. 79-95
  • Tidskriftsartikel (refereegranskat)abstract
    • A two-dimensional finite difference code (FDCON) is used to estimate the progressive deformation and the effect of a composite rheology, i.e., Newtonian combined with non-Newtonian, on finite deformation patterns within a down-built diapir. The geometry of the diapir is fixed using two rigid rectangular overburden units which sink into a source layer of a certain viscosity. We have analyzed the progressive deformation within the entire salt layer for a composite rheology and compared them to a standard model with Newtonian rheology (ηs = 1018 Pa s). The composite rheology models show a more complex deformation patterns in comparison to the standard model. Deformation is more localized within the source layer, leaving a broader less deformed zone within the middle of the source layer. In comparison to the standard model, ellipticity (R) of the strain ellipse is amplified by a factor of up to three in high deformation regions with a finite deformation f larger than two (f = log10(R)). Initially vertical and horizontal passive marker-lines within the salt layer, are folded during salt movement. Initially horizontally-oriented marker-lines in the source layer show upright folds within the middle of the stem. Within the source layer, initially vertical marker-lines form recumbent folds, which are refolded during their flow from the source layer into the stem. During their refolding, the hinge of the fold migrates outward towards the flank of the diapir. A temporal and spatial hinge migration is observed for sub-horizontal folds that originated in the source layer as they are refolded. We have also studied both the effect of curved versus sharp corners between the source layer and the stem on strain evolution within both the feeding source layer and the down-built diapir. Strain evolution and hinge migration are strongly influenced by the geometry of the corner between the source layer and the stem.
  •  
48.
  • Fuchs, Lukas, et al. (författare)
  • Numerical modeling on progressive internal deformation indown-built diapirs
  • 2014
  • Ingår i: Tectonophysics. - : Elsevier. - 0040-1951 .- 1879-3266. ; 632, s. 111-122
  • Tidskriftsartikel (refereegranskat)abstract
    • A two-dimensional finite difference code (FDCON) is used to estimate the finite deformationwithin a down-builtdiapir. The geometry of the down-built diapir is fixed by using two rigid rectangular overburden unitswhich sinkinto a source layer of a constant viscosity. Thus, the model refers to diapirs consisting of a source layerfeeding a vertical stem, and not to other salt structures (e.g. salt sheets or pillows). With this setup westudy the progressive strain in three different deformation regimes within the “salt” material: (I) a squeezedchannel-flow deformation regime and (II) a corner-flow deformation regime within the source layer, and(III) a pure channel-flow deformation regime within the stem. We analyze the evolution of finite deformationin each regime individually, progressive strain for particles passing all three regimes, and total 2Dfinite deformationwithin the salt layer. Model results show that the material which enters the stem bears inherited strainaccumulated from the other two domains. Therefore, finite deformation in the stem differs from the expectedchannel-flow deformation, due to the deformation accumulated within the source layer. The stem displays ahigh deformation zone within its center and areas of decreasing progressive strain between its center and itsboundaries.High deformation zoneswithin the stemcould also be observedwithin natural diapirs (e.g. Klodowa,Polen). The location and structure of the high deformation zone (e.g. symmetric or asymmetric) could revealinformation about different rates of salt supplies from the source layer. Thus, deformation pattern could directlybe correlated to the evolution of the diapir.
  •  
49.
  •  
50.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 202
Typ av publikation
tidskriftsartikel (150)
konferensbidrag (22)
bokkapitel (11)
doktorsavhandling (8)
proceedings (redaktörskap) (3)
annan publikation (3)
visa fler...
licentiatavhandling (2)
samlingsverk (redaktörskap) (1)
bok (1)
forskningsöversikt (1)
visa färre...
Typ av innehåll
refereegranskat (168)
övrigt vetenskapligt/konstnärligt (31)
populärvet., debatt m.m. (3)
Författare/redaktör
Koyi, Hemin (169)
Koyi, Hemin A. (29)
Talbot, Christopher ... (15)
Schmeling, Harro (15)
Nilfouroushan, Faram ... (12)
Fuchs, Lukas (9)
visa fler...
Almqvist, Bjarne (8)
Burchardt, Steffi (6)
Sans, Maura (6)
Schmeling, H. (5)
Maillot, Bertrand (5)
Mukherjee, S. (4)
Juhlin, Christopher, ... (4)
Dietl, Carlo (4)
Teixell, Antonio (4)
Nilfouroushan, Faram ... (4)
Hessami, Khaled (4)
Sjöström, Håkan (3)
Masrouhi, Amara (3)
Bellier, Olivier (3)
Skelton, Alasdair (3)
Pease, Victoria (3)
Muñoz, J. A. (3)
Dietl, C (3)
Deng, Hongling, 1983 ... (3)
Koyi, Hemin, Profess ... (3)
Farzipour-Saein, Ali (3)
Harris, Lyal (3)
Zeyen, Hermann (2)
Mulugeta, G. (2)
Mulugeta, Genene (2)
Högdahl, Karin (2)
Korja, A (2)
Mansurbeg, Howri (2)
Nilfouroushan, Faram ... (2)
Troll, Valentin R. (2)
Lorenz, Henning, Dr. ... (2)
Aswad, Khalid J. A. (2)
Aziz, Nabaz R. H. (2)
Barchi, M. R. (2)
Mancktelow, Neil (2)
Nilforoushan, Farama ... (2)
Chemia, Zurab (2)
Cotton, James (2)
Deng, Hongling (2)
Petersen, K (2)
Sirat, Manhal (2)
Swantesson, Jan (2)
Hessami, K (2)
Morad, Daniel (2)
visa färre...
Lärosäte
Uppsala universitet (192)
Högskolan i Gävle (16)
Stockholms universitet (4)
Göteborgs universitet (2)
Karlstads universitet (2)
Lunds universitet (1)
visa fler...
Karolinska Institutet (1)
visa färre...
Språk
Engelska (199)
Svenska (3)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (176)
Teknik (1)
Samhällsvetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy