Basement-controlled structural fronts forming an apparent major refold pattern in the Yellowknife domain, Slave Province

1984 ◽  
Vol 21 (7) ◽  
pp. 822-828 ◽  
Author(s):  
W. K. Fyson
Keyword(s):  

Trend lines of tight folds (F0 and F1) in Archean metasediments curve across the Yellowknife supracrustal domain to form an apparent major refold pattern. "Hinge traces," marking pronounced changes in trend, extend up to 50 km. More locally, F1 folds are discontinuous and markedly discordant in trend, suggesting that the major hinge traces, rather than simply following axial surfaces, denote structural fronts where fold sets with distinctive initial trends have interacted.Cleavages grouped as S2 and S3, each with subsets, postdate the F1, folds. A regional S3 cleavage strikes parallel to major hinge traces, whereas discontinuous S3 subsets are oblique, some terminating along well defined cleavage fronts. For example, one subset replaces another along a front generally parallel to a hinge trace, or fold front, but offset 1–2 km.The development of the apparent refold pattern and the parallelism of various generations of structural fronts and cleavages can be explained by the response of cover rocks to recurrent strike-slip movements and stress reorientations by faults in the basement.


1991 ◽  
Vol 28 (1) ◽  
pp. 126-135 ◽  
Author(s):  
W. K. Fyson ◽  
V. A. Jackson

A complex array of folds and cleavages in metasedimentary and metavolcanic rocks in the Russell Lake domain could reflect regional compression recurrently reoriented across crustal lineaments. Several generations of steeply inclined folds trending northward across the domain curve into or interfere with folds parallel to margins of bordering granite batholiths aligned orthogonally northwest (LNW) and northeast (LNE). Sets of later subvertical cleavages strike northward, northwest parallel and oblique to LNW, and northeastward subparallel to LNE. The cleavages extend beyond the aligned margins, indicating that the association with the granites is indirect.The arrangements of folds and cleavages are consistent with intermittent redirection of subhorizontal compression of cover rocks perpendicular to orthogonal, steep crustal fractures that were intruded by syndeformational granitic plutons. Additionally, overturning of folds near plutons suggests local reorientation of compression near shallow-dipping margins. Following folding, further reorientations resulted in reversals in strike-slip bedding shear and cleavage sets locally symmetric about fold limbs.



2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 



2020 ◽  
Vol 57 (1) ◽  
pp. 21-40
Author(s):  
Alexandra Wallenberg ◽  
Michelle Dafov ◽  
David Malone ◽  
John Craddock

A harzburgite intrusion, which is part of the trailside mafic complex) intrudes ~2900-2950 Ma gneisses in the hanging wall of the Laramide Bighorn uplift west of Buffalo, Wyoming. The harzburgite is composed of pristine orthopyroxene (bronzite), clinopyroxene, serpentine after olivine and accessory magnetite-serpentinite seams, and strike-slip striated shear zones. The harzburgite is crosscut by a hydrothermally altered wehrlite dike (N20°E, 90°, 1 meter wide) with no zircons recovered. Zircons from the harzburgite reveal two ages: 1) a younger set that has a concordia upper intercept age of 2908±6 Ma and a weighted mean age of 2909.5±6.1 Ma; and 2) an older set that has a concordia upper intercept age of 2934.1±8.9 Ma and a weighted mean age 2940.5±5.8 Ma. Anisotropy of magnetic susceptibility (AMS) was used as a proxy for magmatic intrusion and the harzburgite preserves a sub-horizontal Kmax fabric (n=18) suggesting lateral intrusion. Alternating Field (AF) demagnetization for the harzburgite yielded a paleopole of 177.7 longitude, -14.4 latitude. The AF paleopole for the wehrlite dike has a vertical (90°) inclination suggesting intrusion at high latitude. The wehrlite dike preserves a Kmax fabric (n=19) that plots along the great circle of the dike and is difficult to interpret. The harzburgite has a two-component magnetization preserved that indicates a younger Cretaceous chemical overprint that may indicate a 90° clockwise vertical axis rotation of the Clear Creek thrust hanging wall, a range-bounding east-directed thrust fault that accommodated uplift of Bighorn Mountains during the Eocene Laramide Orogeny.



2016 ◽  
Vol 72 (12) ◽  
Author(s):  
Dinesh Kumar Madan ◽  
Poonam Arya ◽  
N. R. Garg




Geology ◽  
2000 ◽  
Vol 28 (12) ◽  
pp. 1075-1078
Author(s):  
S.J. Pehrsson ◽  
T. Chacko ◽  
M. Pilkington ◽  
M.E. Villeneuve ◽  
K. Bethune


2016 ◽  
Author(s):  
Eben Blake Hodgin ◽  
◽  
James Crowley ◽  
Victor Carlotto ◽  
Francis A. Macdonald




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