Theory of Spacing of Extension Fracture

2015 ◽  
pp. 27-53 ◽  
Author(s):  
George M. Sowers
Keyword(s):  
Extension Fracture

Mesoscopic and magnetic fabrics in arcuate igneous bodies: an example from the Mandi-Karsog pluton, Himachal Lesser Himalaya

2010 ◽  
Vol 147 (5) ◽  
pp. 652-664 ◽  
Author(s):  
R. JAYANGONDAPERUMAL ◽  
A. K. DUBEY ◽  
K. SEN
Keyword(s):  
Host Rock ◽  
Magnetic Fabric ◽  
Lesser Himalaya ◽  
Himalayan Orogeny ◽  
Magnetic Fabrics ◽  
Himachal Lesser Himalaya ◽  
Shear Sense ◽  
Magmatic Fabric ◽  
Extension Fracture ◽  
Shear Sense Indicators

AbstractField, microstructural and anisotropy of magnetic susceptibility (AMS) data from the Palaeozoic Mandi-Karsog pluton in the Lesser Himalayan region reveal a concordant relationship between fabric of the Proterozoic host rock and the granite. The pluton displays a prominent arcuate shape on the geological map. The margin-parallel mesoscopic and magnetic fabrics of the granite and warping of the host rock fabric around the pluton indicate that this regional curvature is either synchronous or pre-dates the emplacement of the granite body. Mesoscopic fabric, magnetic fabric and microstructures indicate that the northern part of the pluton preserves its pre-Himalayan magmatic fabric while the central and southern part shows tectonic fabric related to the Tertiary Himalayan orogeny. The presence of NW–SE-trending aplitic veins within the granite indicates a post-emplacement stretching in the NE–SW direction. Shear-sense indicators in the mylonites along the margin of the pluton suggest top-to-the-SW shearing related to the Himalayan orogeny. Based on these observations, it is envisaged that the extension that gave rise to this rift-related magmatism had a NE–SW trend, that is, normal to the trend of the aplite veins. Subsequently, during the Himalayan orogeny, compression occurred along this same NE–SW orientation. These findings imply that the regional curvature present in the Himachal Lesser Himalaya is in fact a pre-Himalayan feature and the pluton has formed by filling a major pre-Himalayan arcuate extension fracture.

Extension fracture due to collinear cracks

1996 ◽  
Vol 54 (1) ◽  
pp. 25-33 ◽  
Author(s):  
J.J. Golecki ◽  
D. Ornai
Keyword(s):  
Collinear Cracks ◽  
Extension Fracture

Structural analysis of the Theistareykir Fissure Swarm (NE Iceland) using field survey integrated with UAV-based - Structure from Motion techniques

2020 ◽  
Author(s):  
Noemi Corti ◽  
Alessandro Tibaldi
Keyword(s):  
Structure From Motion ◽  
Field Survey ◽  
Late Quaternary ◽  
3D Models ◽  
Normal Faults ◽  
Large Area ◽  
Southern Sector ◽  
Fissure Swarm ◽  
Aerial Vehicle ◽  
Extension Fracture

<p>Due to its position at the boundary between American and European plates, Iceland represents an ideal natural laboratory to study active rifting processes, where rifting mechanisms are complicated by the superimposition of tectonic and magmatic stresses. In order to contribute to the study of such processes, we focused our attention on the southern sector of the Theistareykir Fissure Swarm (ThFS), an active volcanic rift belonging to the Northern Volcanic Zone of Iceland, affected by both volcanic and seismic hazard.</p><p>We studied an area which is about 22 km<sup>2</sup>-large, situated 12 km south of the intersection of the ThFS with the Husavik Flatey Fault (HFF), a dextral strike-slip lineament belonging to the Tjornes Fracture Zone (TFZ). The area is characterized by the presence of normal faults and a dense swarm of extension fractures, affecting prevalently post-glacial, Holocene lavas, dated 8-10 and 11-12 ka. Only in the western sector of the area a Late Quaternary interglacial lava crops out, while the northeastern sector is covered by a Weichselian subglacial hyaloclastite. The southern sector of the area has been investigated with classical field survey, whereas in the northern part a 3.87 km<sup>2</sup>-large area has been reconstructed using the Structure from Motion (SfM) techniques, combined with an Unmanned Aerial Vehicle (UAV), obtaining orthomosaics, DSMs and 3D models with a centimetric resolution through 4189 UAV photos, collected in 7 different missions during summer 2018.</p><p>In the whole area, we recognized and mapped a total of 624 structures (comprising 583 extension fractures and 41 normal faults), and we took various measurements at 626 structural stations along extension fractures, and 132 along normal faults. Regarding extension fractures, we collected the strike and, in 441 cases where it was possible, the opening direction and the amount of opening; along normal faults we measured the strike, dip and vertical offset.</p><p>Our approach allowed to calculate stretch values across the rift comprised between 1.002 and 1.013, and an average opening direction value of 104.4°N, normal to the average extension fracture strike measured at the structural stations (14°N), suggesting a pure extensional opening in the studied area. Actually, in 281 cases out of our 441 stations along extension fractures we noticed a lateral component > 5°. Furthermore, 49% of data is not consistent with tectonics, neither with regard to the extensional fracture strike, nor with regard to opening directions. This suggests that stresses linked to regional tectonics are not the only cause of deformation, which could have been affected by different processes like dyke intrusion, deglaciation, and inflation/deflation of the Theistareykir volcano magma chamber.</p>

A stress-transfer model for the development of extension fracture boudinage

1982 ◽  
Vol 4 (3) ◽  
pp. 355-372 ◽  
Author(s):  
G.E Lloyd ◽  
C.C Ferguson ◽  
K Reading
Keyword(s):  
Stress Transfer ◽  
Transfer Model ◽  
Extension Fracture

scholarly journals Biomechanics of upper cervical spine and peculiarities of treatment of patients with odontoid process fractures

1996 ◽  
Vol 3 (1) ◽  
pp. 18-21
Author(s):  
V. A. Moiseenko
Keyword(s):  
Cervical Spine ◽  
Conservative Treatment ◽  
Odontoid Process ◽  
Upper Cervical Spine ◽  
Traction Method ◽  
Cervical Muscles ◽  
Halo Traction ◽  
Upper Cervical ◽  
Extension Fracture

In transdental injuries of atlantoaxial region the indications for conservative treatment and authors bipolar Halo-traction method were worked out on the base of spine biomechanical peculiarities (anterior shifting moment and extensor conditionality of the posterior cervical muscles) as well as depending on the mechanism of the development of plane fracture of C2 odontoid process. In flexion fracture of the odontoid process without dislocation as well as in extension fracture with dislocation within the limits of 1/3 of its diameter the successful conservative treatment with plaster thoracocranial bandage was possible. In the rest of cases the authors method of bipolar Halo-traction was indicated. The experience of treatment of 32 patients was used in the work.

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