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Koyi, Hemin
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Publications (10 of 168) Show all publications
Buntin, S., Malehmir, A., Koyi, H., Högdahl, K., Malinowski, M., Larsson, S. A., . . . Gorszczyk, A. (2019). Emplacement and 3D geometry of crustal-scale saucer-shaped intrusions in the Fennoscandian Shield. Scientific Reports, 9, Article ID 10498.
Open this publication in new window or tab >>Emplacement and 3D geometry of crustal-scale saucer-shaped intrusions in the Fennoscandian Shield
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 10498Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-391379 (URN)10.1038/s41598-019-46837-x (DOI)000476468700026 ()31324841 (PubMedID)
Funder
Swedish Research Council, 2015-05177
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-03Bibliographically approved
Rojo, L. A., Cardozo, N., Escalona, A. & Koyi, H. (2019). Structural style and evolution of the Nordkapp Basin, Norwegian Barents Sea. American Association of Petroleum Geologists Bulletin
Open this publication in new window or tab >>Structural style and evolution of the Nordkapp Basin, Norwegian Barents Sea
2019 (English)In: American Association of Petroleum Geologists Bulletin, ISSN 0149-1423, E-ISSN 1558-9153Article in journal (Refereed) Epub ahead of print
Abstract [en]

After three decades of research and hydrocarbon exploration in the Nordkapp Basin (Norwegian Barents Sea), the dynamics of Mesozoic salt mobilization is still poorly understood. Both, progradational loading and basement-involved extension have been proposed as triggers of salt mobilization, where the latter is most accepted. This study combines 2D and 3D seismic reflection data, borehole data, isochore maps and structural restorations to: (1) provide a tectonostratigraphic evolution of the Nordkapp Basin, (2) indicate which triggering mechanisms fit the observed structural styles, and (3) determine the geological controls that influenced the along-strike distribution of salt structures in the basin. Our results indicate that a combination of Early–Middle Triassic thick-skinned extension and sediment loading induced the differential loading and mobilization of the underlying salt, generating a series of NW-shifting minibasins bounded by salt walls, ridges and stocks. Sediment loading and the distribution of salt structures were strongly conditioned by rheology variations within the salt layer and subsalt fault activity which: (1) created tectonically-induced depressions that became preferential areas of infill and differential loading; (2) caused faulting and extension of the overburden, allowing the preferential growth of reactive diapirs which later on evolved into passive diapirs; and (3) acted as effective barriers of salt expulsion, enhancing salt inflation and growth of salt above the subsalt faults. Early Triassic differential loading occurred diachronically along strike, causing early passive diapirism, salt welding, and salt depletion in the eastern and central subbasins due to the diachronous subsalt activity and the closer proximity of these basins respect to the sediment source, the Uralides. Although most of the salt was depleted by the end of the Middle Triassic, the ongoing extension created across-fault thickness variations and sagging of some of the WNW-ESE salt walls in the central subbasin. The rest of the structures in the Nordkapp Basin continued growing until the end of the Mesozoic by minor evacuation of the remaining salt and thin-skinned gliding and subsequent shortening triggered by subsalt fault activity. Finally, salt structures were rejuvenated and eroded during Cenozoic contraction and uplift. These results have implications for the 4D understanding of the Nordkapp Basin and its petroleum system, and they can be used as an analogue to decipher other confined salt bearing-basins alike.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-360464 (URN)10.1306/01301918028 (DOI)
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2019-03-21Bibliographically approved
Almqvist, B. & Koyi, H. (2018). Bulk strain in orogenic wedges based on insights from magnetic fabrics in sandbox models. Geology, 46(6), 483-486
Open this publication in new window or tab >>Bulk strain in orogenic wedges based on insights from magnetic fabrics in sandbox models
2018 (English)In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 46, no 6, p. 483-486Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Geology Geophysics
Identifiers
urn:nbn:se:uu:diva-347792 (URN)10.1130/G39998.1 (DOI)000433513800004 ()
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2018-08-16Bibliographically approved
Koyi, H. (2018). Compressional Salt‐Related Structures in the Western Quele Area, Kuqa Depression, Tarim Basin, China: Wu, Zh., Yin, H., and Koyi, H.A.. In: Achyuta Ayan Misra; Soumyajit Mukherjee (Ed.), Atlas of Structural Geological Interpretation from Seismic Images: (pp. 163-166). Wiley-Blackwell Publishing Inc.
Open this publication in new window or tab >>Compressional Salt‐Related Structures in the Western Quele Area, Kuqa Depression, Tarim Basin, China: Wu, Zh., Yin, H., and Koyi, H.A.
2018 (English)In: Atlas of Structural Geological Interpretation from Seismic Images / [ed] Achyuta Ayan Misra; Soumyajit Mukherjee, Wiley-Blackwell Publishing Inc., 2018, p. 163-166Chapter in book (Refereed)
Place, publisher, year, edition, pages
Wiley-Blackwell Publishing Inc., 2018
National Category
Geology Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-360463 (URN)978-1-119-15832-5 (ISBN)9781119158332 (ISBN)
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-12-19Bibliographically approved
Koyi, H. (2018). De-risking plays in the highly folded zone foreland basin of the Zagros fold-thrust belt, Kurdistan Region, Iraq.: Mansurbeg, H., Koyi, H.A., Othman, R., Kolo, K., Harchegani, F.. In: Farzipour-Saein; Mukherjee (Ed.), Tectonic and Structural Framework of the Zagros Fold-and-Thrust Belt: . Elsevier
Open this publication in new window or tab >>De-risking plays in the highly folded zone foreland basin of the Zagros fold-thrust belt, Kurdistan Region, Iraq.: Mansurbeg, H., Koyi, H.A., Othman, R., Kolo, K., Harchegani, F.
2018 (English)In: Tectonic and Structural Framework of the Zagros Fold-and-Thrust Belt / [ed] Farzipour-Saein; Mukherjee, Elsevier, 2018Chapter in book (Refereed)
Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Geosciences, Multidisciplinary Geology
Identifiers
urn:nbn:se:uu:diva-360456 (URN)9780128150481 (ISBN)9780128150498 (ISBN)
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-12-19Bibliographically approved
Koyi, H. (2018). Local thrust formed within a decollement zone during extension, Upper Rhine Graben, France.: Place J., Diraison M., Géraud Y. and Koyi H.A.. In: Achyuta Ayan Misra (Ed.), Atlas of Structural Geological Interpretation from Seismic Images: (pp. 47-49). Wiley-Blackwell Publishing Inc.
Open this publication in new window or tab >>Local thrust formed within a decollement zone during extension, Upper Rhine Graben, France.: Place J., Diraison M., Géraud Y. and Koyi H.A.
2018 (English)In: Atlas of Structural Geological Interpretation from Seismic Images / [ed] Achyuta Ayan Misra, Wiley-Blackwell Publishing Inc., 2018, p. 47-49Chapter in book (Refereed)
Place, publisher, year, edition, pages
Wiley-Blackwell Publishing Inc., 2018
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-360462 (URN)978-1-119-15832-5 (ISBN)
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-09-13
Cruciani, F., Barchi, M. R., Koyi, H. & Porreca, M. (2017). Kinematic evolution of a regional-scale gravity-driven deepwater fold-and-thrust belt: The Lamu Basin case-history (East Africa). Tectonophysics, 712-713, 30-44
Open this publication in new window or tab >>Kinematic evolution of a regional-scale gravity-driven deepwater fold-and-thrust belt: The Lamu Basin case-history (East Africa)
2017 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 712-713, p. 30-44Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Deepwater fold-and-thrust belt, Restoration, Rate of shortening, Lamu Basin, East Africa
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-335711 (URN)10.1016/j.tecto.2017.05.002 (DOI)000409284500003 ()
Funder
Swedish Research Council
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2017-12-11Bibliographically approved
Sattar, N., Juhlin, C., Koyi, H. & Ahmad, N. (2017). Seismic stratigraphy and hydrocarbon prospectivity of the Lower, Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High, Hammerfest Basin, Barents Sea. Marine and Petroleum Geology, 85, 54-69
Open this publication in new window or tab >>Seismic stratigraphy and hydrocarbon prospectivity of the Lower, Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High, Hammerfest Basin, Barents Sea
2017 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 85, p. 54-69Article, review/survey (Refereed) Published
Abstract [en]

The Lower Cretaceous Knurr Sandstone deposited along the southern slope of Loppa High and overlain by the Kolje and Kolmule seals forms an attractive play in the Hammerfest Basin of the Barents Sea. Late Jurassic organic-rich Hekkingen shale directly underlies the Knurr Sandstone and acts as a source to provide effective charge. Three wells, 7120/2-2, 7122/2-1 and 7120/1-2, have proven the Knurr-Kolje play in structural traps, with an oil discovery in 7120/1-2. Prospectivity related to stratigraphic traps is, however, highly under-explored. In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Lower Cretaceous sedimentary package containing the Knurr Sandstone is divided into a number of depositional sequences and systems tracts using key regional seismic profiles calibrated with logs. Mapping of the key surfaces bounding the Knurr sandstone has been carried out using all the seismic vintages available from Norwegian Petroleum Directorate (NPD).The thick massive nature of the sandstone (123 m in well 7122/2-1), sedimentary features characteristic of gravity flow deposits, high-resolution internal seismic reflections and stratal geometries (truncations and lapout patterns), and sequence stratigraphic position of the Knurr Sandstone on seismic profiles confirm that the lobes identified on the seismic section are gravity driven base of the slope lobes. These Knurr lobes and slope aprons were formed as a result of uplift of the Loppa paleo-high in the Late Jurassic to Early Cretaceous times which caused subaerial exposure and incision. The characteristic mounded, lobate geometry evident on the seismic can be mapped along the toe-of-slope and records multiple stacked lobes fed by multiple feeder canyons. Lateral partitioning and separation of the lobes along the toe-of-slope could potentially create strati graphic traps. The existing 2D seismic coverage is, however, not sufficient to capture lateral stratigraphic heterogeneity to identify stratigraphic traps. 3D seismic coverage with optimum acquisition parameters (high spatial and vertical resolution, appropriate seismic frequency and fold, long offsets and original amplitudes preserved) can allow for the reconstruction of 3D geomorphologic elements to de-risk potential stratigraphic traps prior to exploratory drilling.

Keywords
Barents sea, Knurr sandstone, Seismic stratigraphy, Turbidite lobes, Hammerfest basin
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-333820 (URN)10.1016/j.marpetgeo.2017.04.008 (DOI)000403983300004 ()
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2017-11-29Bibliographically approved
Carrillo, E., Koyi, H. A. & Nilforoushan, F. (2017). Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain). Marine and Petroleum Geology, 86, 1310-1326
Open this publication in new window or tab >>Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)
2017 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 86, p. 1310-1326Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Evaporites, Stratigraphic heterogeneities, Structural deformation, Kinematic evolution, Pyrenees, Analogue modeling
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-336494 (URN)10.1016/j.marpetgeo.2017.07.024 (DOI)000411296600077 ()
Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2017-12-14Bibliographically approved
Shahpasandzadeh, M., Koyi, H. & Nilfouroushan, F. (2017). The significance of switch in convergence direction in the Alborz Mountains, northern Iran: Insights from scaled analogue modeling. Interpretation, 5(1), SD81-SD98
Open this publication in new window or tab >>The significance of switch in convergence direction in the Alborz Mountains, northern Iran: Insights from scaled analogue modeling
2017 (English)In: Interpretation, ISSN 2324-8858, E-ISSN 2324-8866, Vol. 5, no 1, p. SD81-SD98Article in journal (Refereed) Published
Abstract [en]

The switch in direction of convergence between Central Iran and the Eurasian Plate is believed to have a significant impact on the structural style in the Alborz Mountains, in the north of Iran. To understand the deformation pattern and investigate the influence of the South Caspian Basin kinematics since the middle Miocene on the structural styles and active tectonics of the Alborz Mountains, a series of scaled analogue models were prepared, in which passively layered loose sand simulating the sedimentary units were subjected to orthogonal and subsequently oblique shortening by a rigid indenter. Model results indicate that during the shortening, an arcuate-shaped foreland-vergent imbricate stack forms in front of the indenter. The orthogonal shortening is characterized by a prevailing right-lateral and left-lateral oblique-slip motion in the east and west of the model, respectively. This shift in kinematics contradicts the proposed preneotectonic (orthogonal) model of the Alborz. However, during oblique shortening, model results show that deformation is mainly accommodated by leftlateral transpression within the sand wedge and internal deformation. Oblique shortening is consistently accommodated by continued left-lateral motion on the west-northwest-trending oblique thrusts, whereas the east-westtrending thrusts and the preexisting east-northeast-trending right-lateral oblique thrusts reactivate as left-lateral oblique faults. Precise monitoring of the model surface also illustrates partitioning of shortening into the forelandvergent left-lateral thrusting in the south and hinterland-vergent back thrusting in the north. These model results are generally consistent with field observations and GPS data of structure and kinematics of the Alborz Mountains.

National Category
Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-361075 (URN)10.1190/INT-2016-0117.1 (DOI)000397196600030 ()
Funder
Swedish Research Council
Available from: 2018-09-20 Created: 2018-09-20 Last updated: 2018-09-20Bibliographically approved
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