Reorientation of structures near granitic plutons and orthogonal lineaments, Russell Lake supracrustal domain, southwestern Slave Province

1991 ◽  
Vol 28 (1) ◽  
pp. 126-135 ◽  
Author(s):  
W. K. Fyson ◽  
V. A. Jackson
Keyword(s):  
Strike Slip ◽  
Slave Province ◽  
Metavolcanic Rocks ◽  
Regional Compression

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.

Granitoid complexes and the Archean tectonic record in the southern part of northwestern Ontario

1979 ◽  
Vol 16 (10) ◽  
pp. 1965-1977 ◽  
Author(s):  
W. M. Schwerdtner ◽  
D. Stone ◽  
K. Osadetz ◽  
J. Morgan ◽  
G. M. Stott
Keyword(s):  
Large Scale ◽  
Vertical Motion ◽  
Strike Slip ◽  
Horizontal Motion ◽  
Tectonic Deformation ◽  
Northwestern Ontario ◽  
Greenstone Belts ◽  
Second Period ◽  
Transcurrent Faults ◽  
Regional Compression

Two principal, possibly overlapping, periods of tectonic deformation can be distinguished in the Archean of northwestern Ontario, a period of dominantly vertical-motion tectonics and a period of dominantly horizontal-motion tectonics. Gigantic diapirs of foliated to gneissic tonalite–granodiorite developed during the first period and appear to be responsible for the gross structure of, and the major folds within, the metavolcanic–metasedimentary masses ("greenstone belts"). These diapirs are most likely due to mechanical remobilization of early tabular batholiths which originally intruded the oldest supracrustal rocks presently exposed. Later massive to foliated, dioritic to granitic plutons that vary from concordant, crescentic plutons to partly discordant plutons of various shapes and sizes were emplaced into the diapirs.The second period of tectonic deformation is characterized by large-scale dextral shearing and the development of major transcurrent faults under northwesterly regional compression. The strike-slip motions of this period outlasted the late plutonism, and led to the development of mylonitic zones which cut all Archean granitoid plutons.

Structural development of angular volcanic belts in the Archean Slave Province

1990 ◽  
Vol 27 (3) ◽  
pp. 403-413 ◽  
Author(s):  
W. K. Fyson
Keyword(s):  
Late Phase ◽  
Length Change ◽  
Structural Development ◽  
Southwestern Part ◽  
Phase Layer ◽  
Slave Province ◽  
Granitoid Rocks ◽  
Transfer Faults ◽  
Volcanic Belts ◽  
Regional Compression

Narrow belts of metavolcanics lying between metasediments and granitoid rocks in the southwestern part of the Archean Slave Province display a distinctive angular map pattern. Steep homoclinal segments, from 10 to over 50 km in length, change strike abruptly at "corners" as if defining large, open, angular folds. Structures near two corners in a belt are not, however, compatible with such folds. Examples include early-phase, layer-parallel foliations in directional sets that are interspersed with one set overprinting the other; mafic dykes of similar contrasting orientations interspersed within basal gneiss; and isoclines in metasediments that deflect rather than wrap around a corner. Additionally, late-phase foliations striking across corners indicate compression that tended to straighten rather than fold the belt.It is suggested that the angular volcanic belts and imposed structures reflect movements on long-lived, crustal-scale faults. A model of development is proposed in which synvolcanic, listric extensional faults and high-angle transfer faults were reactivated as upthrusts during regional compression. Consequent tilting of the volcanics in different directions formed the angular pattern of steep homoclines and guided the development of a succession of folds and foliations.

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):  
Strike Slip ◽  
Slave Province

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.

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

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. 

Zircon geochronology and paleomagnetism of an Archean harzburgite intrusion, eastern Bighorn Mountains, Wyoming

2020 ◽  
Vol 57 (1) ◽  
pp. 21-40
Author(s):  
Alexandra Wallenberg ◽  
Michelle Dafov ◽  
David Malone ◽  
John Craddock
Keyword(s):  
Hanging Wall ◽  
Vertical Axis ◽  
Shear Zones ◽  
Strike Slip ◽  
Zircon Geochronology ◽  
Weighted Mean ◽  
Mafic Complex ◽  
Laramide Orogeny ◽  
Axis Rotation ◽  
Bighorn Mountains

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.

Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland

1999 ◽  
pp. 65-78
Author(s):  
Henrik Rasmussen ◽  
Lars Frimodt Pedersen
Keyword(s):  
Tectonic Setting ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
West Greenland ◽  
North West ◽  
North East ◽  
Metavolcanic Rocks ◽  
Arc Setting ◽  
Area North ◽  
Back Arc

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Rasmussen, H., & Frimodt Pedersen, L. (1999). Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 65-78. https://doi.org/10.34194/ggub.v181.5114 _______________ Two Archaean supracrustal sequences in the area north-east of Disko Bugt, c. 1950 and c. 800 m in thickness, are dominated by pelitic and semipelitic mica schists, interlayered with basic metavolcanic rocks. A polymict conglomerate occurs locally at the base of one of the sequences. One of the supracrustal sequences has undergone four phases of deformation; the other three phases. In both sequences an early phase, now represented by isoclinal folds, was followed by north-west-directed thrusting. A penetrative deformation represented by upright to steeply inclined folds is only recognised in one of the sequences. Steep, brittle N–S and NW–SE striking faults transect all rock units including late stage dolerites and lamprophyres. Investigation of major- and trace-element geochemistry based on discrimination diagrams for tectonic setting suggests that both metasediments and metavolcanic rocks were deposited in an environment similar to a modern back-arc setting.

EXPONENTIAL STRIKE-SLIP DISLOCATION MODEL IN DISSIMILAR ANISOTROPIC MEDIA

2016 ◽  
Vol 72 (12) ◽  
Author(s):  
Dinesh Kumar Madan ◽  
Poonam Arya ◽  
N. R. Garg
Keyword(s):  
Anisotropic Media ◽  
Strike Slip ◽  
Dislocation Model ◽  
Slip Dislocation

A STUDY ON NEAR SOURCE STRONG MOTIONS OF STRIKE SLIP FAULTS CONSIDERING VARIOUS RUPTURE SCENARIOS

2018 ◽  
Vol 74 (4) ◽  
pp. I_1017-I_1022 ◽  
Author(s):  
Takao KAGAWA ◽  
Shohei YOSHIDA ◽  
Tatsuya NOGUCHI
Keyword(s):  
Strike Slip

Anton terrane revisited: Late Archean exhumation of a moderate-pressure granulite terrane in the western Slave Province

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