Structural analysis of the foreland basin of the southern Longmenshan tectonic belt: New insights from magnetic fabrics

2021 ◽  
Author(s):  
Yingtao Chen ◽  
Wenxin Yu ◽  
Yang Li ◽  
Guowei Zhang ◽  
Rukui Lu ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Foreland Basin ◽  
Magnetic Fabrics ◽  
Tectonic Belt

Palaeomagnetic study of the Cairnsmoor of Fleet Granite and Criffel-Dalbeattie granodiorite contact aureoles: Caledonian tectonics of the Southern Uplands of Scotland and Devonian palaeogeography

2007 ◽  
Vol 144 (5) ◽  
pp. 811-835
Author(s):  
J. D. A. PIPER ◽  
N. J. McARDLE ◽  
Y. ALMASKERI
Keyword(s):  
Middle Devonian ◽  
Foreland Basin ◽  
Plate Motion ◽  
Irish Sea ◽  
Significant Feature ◽  
Slow Cooling ◽  
Polar Wander ◽  
Northern Margin ◽  
Magnetic Fabrics ◽  
Dual Polarity

The plutons of Cairnsmoor of Fleet (392±2 Ma) and Criffel-Dalbeattie (397±2 Ma, both mineral isochron ages) comprise two of four major post-tectonic granitic complexes emplaced into the Southern Uplands, an Ordovician–Silurian back-arc and foreland basin complex formed at the northern margin of the Iapetus Suture. To expand the palaeomagnetic record of the Southern Uplands we have studied palaeomagnetism and magnetic fabrics in traverses spanning contacts of these intrusions with host mudrocks. A uniform anisotropy of magnetic susceptibility (AMS) fabric across the Cairnsmoor of Fleet contact has been enhanced by recrystallization into hornfels near the contact and records a late Acadian regional stress operative during, or soon after, emplacement of the pluton in Middle Devonian times. Magnetization during slow cooling recorded a dual polarity (‘A’) remanence in granite and hornfels with mean direction D/I = 92/−2° (α95 = 6.5°) yielding a palaeopole (Q = 6) at 2°N, 265°E linked to cooling at c. 392 Ma. Subsidiary magnetizations are overprints imparted during Variscan tectonism (‘B’, D/I = 194/6°) and Jurassic rifting within the adjoining Irish Sea Basin (‘C’, c. 160–140 Ma, D/I = 172/−52°). The Criffel-Dalbeattie pluton has more complex AMS fabrics recording both deformation and emplacement effects. Hematite of secondary hydrothermal origin is a significant feature of the rock magnetic record in the aureole, which is otherwise dominated by paramagnetism. The granodiorite is more strongly magnetized than the country rocks, accounting for a positive aeromagnetic anomaly. A fairly dispersed dual polarity remanence (mean D/I = 115/55°, α95 = 18°) in granodiorite and late tectonic porphyrite dykes is probably the oldest magnetization preserved in this pluton because it correlates with an excursion of Britain into southerly palaeolatitudes at c. 410 Ma and indicates an Early Devonian emplacement age. The palaeofield at c. 397 Ma, the currently accepted isotopic age, is recorded by a minority overprinted remanence (mean D/I = 272/2°, α95 = 12°) similar to the record in the Cairnsmoor of Fleet pluton and granites from the adjoining Lake District terrane. Granite complexes of the Southern Uplands Block collectively record regional rotation and excursion of Britain into southerly latitudes between c. 410 and 390 Ma. Comparable Silurian–Devonian palaeomagnetic poles identify common apparent polar wander (APW) in paratectonic and orthotectonic terranes from the Variscan Front in the south to the Laurentian foreland in the north following climactic Acadian deformation. APW between 430 and 390 Ma embracing the (post-closure) history of the Caledonian orogen is a loop executed at rates much higher than typical rates of plate motion and appears to record a component of true polar wander. The ∼110° arc length is identical to polar shift identified between mid-Silurian and Lower–Middle Devonian poles from Gondwana. The two paths superimpose to show that the western margin of Gondwana was in proximity to the SE margin of Laurentia during Acadian deformation in Early–Middle Devonian times and remote from the Caledonides; the residual Rheic Ocean subsequently closed by a combination of pivotal and left lateral strike-slip motions.

scholarly journals Early–Middle Miocene subtle compressional deformation in the Ebro foreland basin (northern Spain); insights from magnetic fabrics

2016 ◽  
Vol 348 (3-4) ◽  
pp. 213-223 ◽  
Author(s):  
Ruth Soto ◽  
Juan C. Larrasoaña ◽  
Elisabet Beamud ◽  
Miguel Garcés
Keyword(s):  
Middle Miocene ◽  
Foreland Basin ◽  
Northern Spain ◽  
Magnetic Fabrics ◽  
Compressional Deformation

scholarly journals Well records on the Phanerozoic stratigraphy in the Fennoscandian Border Zone, Denmark. Hans-1, Sæby-1, and Terne 1 wells

1991 ◽  
Vol 29 ◽  
pp. 1-37
Author(s):  
Olaf Michelsen ◽  
Lars Henrik Jensen
Keyword(s):  
Volcanic Rocks ◽  
Foreland Basin ◽  
Border Zone ◽  
Lower Carboniferous ◽  
Marine Deposits ◽  
Lower Silurian ◽  
Deep Well ◽  
Lower Palaeozoic ◽  
Well Data ◽  
Tectonic Belt

The Hans-1, Sæby-1, and Terne-1 wells are located within the Danish part of the Fennoscandian Border Zone and provide significant new data pertaining to the evolution of this important tectonic belt. All three wells encountered Palaeozoic rocks; the Terne-1 well extended into the lower Palaeozoic. Two of the wells are located in the Danish waters of the Kattegat, and thus yield the first deep well data from this part of the border zone. The wells encountered Cambrian to Silurian, Carboniferous to Zechstein and Triassic to Upper Cretaceous successions. The Cambrian to Lower Silurian section is interpreted to represent shelf and shallow marine deposits comparable to those known from Scania and Bornholm. The inferred Upper Silurian section is calculated to be up to 2600 m thick and may represent the fill of a foreland basin in front of the Caledonian 4 deformation front. A hiatus comprising the Devonian to Lower Carboniferous is inferred. A 550 m thick Rotliegende sequence was drilled in the eastern part of the Sorgenfrei-Tornquist Zone; changes in structural dip indicate a syn-depositional faulting. Palaeozoic tectonism is also indicated by Late Carboniferous intrusive and extrusive volcanic rocks. Reworked volcanic rocks characterize the Rotliegende elastic sequence. A thin siliciclastic Zechstein sequence is recognized. The lithology and stratigraphy of the Mesozoic sections are in accordance with well data from the Danish Subbasin. The presence of a Middle Jurassic depocenter within the Sorgenfrei-Tornquist Zone may indicate a tectonically controlled subsidence of the zone. The occurrence of a Late Cretaceous to Early Tertiary inversion tectonism is supported by these new data.

scholarly journals Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

2021 ◽  
Author(s):  
Zhenhua Xue ◽  
Wei Lin ◽  
Yang Chu ◽  
Wei Wei ◽  
Zhentian Feng ◽  
...  
Keyword(s):  
Structural Analysis ◽  
South China ◽  
North China ◽  
Late Triassic ◽  
Yangtze Block ◽  
The South ◽  
Structural Geometry ◽  
The North ◽  
Magnetic Fabrics ◽  
Multi Phase

The Bikou Terrane, located at the conjunction of the Longmenshan fold-thrust belt and the west Qinling orogenic belt in centeral China, was involved in the Late Triassic collision between the South China and North China blocks. The Bikou Terrane has preserved crucial information on structural geometry and kinematics of Triassic tectonics, and is therefore of great importance for reconstructing the Paleo-Tethyan evolutionary history. However, multi-phase tectonic events of the Bikou Terrane are unsettled. This work presents detailed structural analysis based on both the field and laboratory works, which reveals three phases of deformation events in Bikou and its adjacent areas, including top-to-the-SW shearing related to SW-ward thrusting (DI) mainly to the north of the Bikou Terrane, top-to-the-NNW shearing related to NNW-ward thrusting (DII) in the Bikou Terrane, and strike-slip faulting (DIII) locally developed in the northern Bikou Terrane. Anisotropy of magnetic susceptibility (AMS) study and related structural analysis not only support the multiphase deformation but also reveal a gradual transition from the DII-related magnetic fabrics to the DIII-related magnetic fabrics in the Bikou Terrane. Integrating published geochronological data, it is constrained that DI occurred at ca. 237−225 Ma, DII occurred at ca. 224−219 Ma, and DIII possibly occurred during the Early Cretaceous. Based on regional tectonics, the DI event corresponds to the collision between the South Qinling block and the Bikou Terrane, and the DII event reflects the intracontinental amalgamation between the Bikou Terrane and the Yangtze block, which indicates a Late Triassic successive amalgamation from the North China block to the South China block. Intracontinental adjustment represented by the strike-slip (DIII event) occurred after the final amalgamation between the North China and South China blocks. By applying AMS on deciphering structural geometry and multi-phase deformation, our study suggests that AMS is a useful tool for structural analysis.

Cenozoic deformation in the Tethyan Himalaya, SE Tibet: Insights from magnetic fabrics and structural analysis of Upper Triassic flysch

2021 ◽  
pp. 228967
Author(s):  
Xinwen Cao ◽  
Zhiming Sun ◽  
Haibing Li ◽  
Yong Cao ◽  
Baochun Huang ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Upper Triassic ◽  
Magnetic Fabrics ◽  
Se Tibet ◽  
Tethyan Himalaya

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

Interpreting HVEM of muscle-cell impulse networks

1992 ◽  
Vol 50 (1) ◽  
pp. 126-127
Author(s):  
Paul DeCosta ◽  
Kyugon Cho ◽  
Stephen Shemlon ◽  
Heesung Jun ◽  
Stanley M. Dunn
Keyword(s):  
Structural Analysis ◽  
Muscle Cell ◽  
Electron Micrographs ◽  
Relative Size ◽  
Automatic Classification ◽  
Nerve Fibers ◽  
Analysis Algorithm ◽  
Structural Networks

Introduction: The analysis and interpretation of electron micrographs of cells and tissues, often requires the accurate extraction of structural networks, which either provide immediate 2D or 3D information, or from which the desired information can be inferred. The images of these structures contain lines and/or curves whose orientation, lengths, and intersections characterize the overall network.Some examples exist of studies that have been done in the analysis of networks of natural structures. In, Sebok and Roemer determine the complexity of nerve structures in an EM formed slide. Here the number of nodes that exist in the image describes how dense nerve fibers are in a particular region of the skin. Hildith proposes a network structural analysis algorithm for the automatic classification of chromosome spreads (type, relative size and orientation).

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