Abundance and distribution of Hg and As in the polymetamorphic Precambrian basement of western Canada

1979 ◽  
Vol 16 (12) ◽  
pp. 2196-2203 ◽  
Author(s):  
R. A. Burwash ◽  
R. R. Culbert
Keyword(s):  
Fault Zone ◽  
Shear Zones ◽  
Ore Deposits ◽  
Fault System ◽  
Western Canada ◽  
Precambrian Basement ◽  
Lake District ◽  
Surface Mapping ◽  
Mean Values ◽  
Abundance And Distribution

mean values of Hg and As in the subsurface Precambrian basement of western Canada are 66 ppb and 1.42 ppm respectively (183 samples). Both figures are close to accepted crustal averages. Plots of cumulative frequency vs. log ppm approach log-normality, but with evidence of small populations enriched in Hg and As and 23% of samples depleted in Hg.Trend surface mapping shows that both Hg and As have regional highs and lows. Several types of multivariate analyses, when applied to petrologic and chemical variables, show that Hg was depleted during both cataclasis and K-metasomatism related to the Hudsonian orogeny. A model for Hg mobility is suggested, with the McDonald–Hay River fault system acting as a conduit for westward migration during the Hudsonian metasomatism. This northeast trending system bisects the Pinchi Lake district Hg ore deposits, which occur along the northwest trending Pinchi fault zone. Mesozoic reactivation of Hudsonian crystalline basement beneath the Omineca crystalline belt may have produced these economic deposits.Multivariate analysis of As values in relation to petrologic variables suggests that As is mobilized during the earlier stages of cataclasis, but finally concentrates locally along major shear zones. The As trend surface high coincides with the area of maximum mylonization along the McDonald fault zone. Concentration of As in major shear zones matches known distributions of niccolite, rammelsbergite, and arsenopyrite in several ore deposits of the western Canadian Shield.

Uranium and thorium in the Precambrian basement of western Canada. I. Abundance and distribution

1976 ◽  
Vol 13 (2) ◽  
pp. 284-293 ◽  
Author(s):  
R. A. Burwash ◽  
G. L. Cumming
Keyword(s):  
Western Canada ◽  
Distribution Analysis ◽  
Metamorphic Belt ◽  
Mean Values ◽  
Western Canada Sedimentary Basin ◽  
Peace River ◽  
Peace River Arch ◽  
Abundance And Distribution ◽  
Canada Sedimentary Basin ◽  
Northern Alberta

Delayed neutron activation analyses of 182 core samples from the basement of the western Canada sedimentary basin give mean values of 4.13 ppm U and 21.1 ppm Th. These values are almost twice the published values for the Shield as a whole. Replicate analyses of a composite sample of all cores indicates an analytical precision of ±1% for uranium and ±7% for thorium.Histograms of number of samples vs. U and Th values indicate a negatively skewed frequency distribution. Analysis of composite samples prepared from a large number of hand specimens may tend to conceal this skewed nature. Mean abundance values will also be influenced by the form of the U and Th frequency distributions.Trend surface analysis, with smoothing to reduce the effect of high or low single sample values, indicates two 'highs' common to both U and Th. The helium-producing area around Swift Current, Saskatchewan is associated with a high U–Th plutonic complex. A linear belt trending northeast from Edmonton appears to be a Hudsonian metamorphic belt in which U and Th have been concentrated. Several local concentrations of U or Th are found in the Peace River Arch of northern Alberta.

scholarly journals The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extension

2011 ◽  
Vol 62 (4) ◽  
pp. 345-359 ◽  
Author(s):  
Erman Özsayin ◽  
Kadir Dirik
Keyword(s):  
Fault Zone ◽  
Structural Evolution ◽  
Shear Zones ◽  
Fault Zones ◽  
Fault System ◽  
Western Boundary ◽  
Southeastern Part ◽  
Anatolian Plateau ◽  
Isparta Angle

The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extensionThe NW-SE striking extensional Inönü-Eskişehir Fault System is one of the most important active shear zones in Central Anatolia. This shear zone is comprised of semi-independent fault segments that constitute an integral array of crustal-scale faults that transverse the interior of the Anatolian plateau region. The WNW striking Eskişehir Fault Zone constitutes the western to central part of the system. Toward the southeast, this system splays into three fault zones. The NW striking Ilıca Fault Zone defines the northern branch of this splay. The middle and southern branches are the Yeniceoba and Cihanbeyli Fault Zones, which also constitute the western boundary of the tectonically active extensional Tuzgölü Basin. The Sultanhanı Fault Zone is the southeastern part of the system and also controls the southewestern margin of the Tuzgölü Basin. Structural observations and kinematic analysis of mesoscale faults in the Yeniceoba and Cihanbeyli Fault Zones clearly indicate a two-stage deformation history and kinematic changeover from contraction to extension. N-S compression was responsible for the development of the dextral Yeniceoba Fault Zone. Activity along this structure was superseded by normal faulting driven by NNE-SSW oriented tension that was accompanied by the reactivation of the Yeniceoba Fault Zone and the formation of the Cihanbeyli Fault Zone. The branching of the Inönü-Eskişehir Fault System into three fault zones (aligned with the apex of the Isparta Angle) and the formation of graben and halfgraben in the southeastern part of this system suggest ongoing asymmetric extension in the Anatolian Plateau. This extension is compatible with a clockwise rotation of the area, which may be associated with the eastern sector of the Isparta Angle, an oroclinal structure in the western central part of the plateau. As the initiation of extension in the central to southeastern part of the Inönü-Eskişehir Fault System has similarities with structures associated with the Isparta Angle, there may be a possible relationship between the active deformation and bending of the orocline and adjacent areas.

Aftershocks of the February 21, 1973 Point Mugu, California earthquake

1976 ◽  
Vol 66 (6) ◽  
pp. 1931-1952
Author(s):  
Donald J. Stierman ◽  
William L. Ellsworth
Keyword(s):  
Fault Zone ◽  
Main Shock ◽  
Fault Plane ◽  
Body Wave ◽  
P Wave ◽  
Fault System ◽  
Wave Radiation ◽  
Fault Plane Solutions ◽  
Complex Deformation ◽  
Transverse Ranges

abstract The ML 6.0 Point Mugu, California earthquake of February 21, 1973 and its aftershocks occurred within the complex fault system that bounds the southern front of the Transverse Ranges province of southern California. P-wave fault plane solutions for 51 events include reverse, strike slip and normal faulting mechanisms, indicating complex deformation within the 10-km broad fault zone. Hypocenters of 141 aftershocks fail to delineate any single fault plane clearly associated with the main shock rupture. Most aftershocks cluster in a region 5 km in diameter centered 5 km from the main shock hypocenter and well beyond the extent of fault rupture estimated from analysis of body-wave radiation. Strain release within the imbricate fault zone was controlled by slip on preexisting planes of weakness under the influence of a NE-SW compressive stress.

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

<p>The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10° since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.</p><p>Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V “Téthys II”, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.</p><p>The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.</p>

scholarly journals Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 83 ◽  
Author(s):  
Rolly E. Rimando ◽  
Jeremy M. Rimando
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Active Faults ◽  
Vertical Component ◽  
The Philippines ◽  
Google Earth ◽  
Fault System ◽  
Philippine Sea Plate ◽  
Oblique Convergence ◽  
Philippine Fault Zone

The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately.

scholarly journals The Moroccan Massive Sulphide Deposits: Evidence for a Polyphase Mineralization

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 156 ◽  
Author(s):  
Abderrahim Essaifi ◽  
Kathryn Goodenough ◽  
Fernando Tornos ◽  
Abdelhak Outigua ◽  
Abdelmalek Ouadjou ◽  
...  
Keyword(s):  
Lead Isotopes ◽  
Shear Zones ◽  
Structural Features ◽  
Isotopic Signature ◽  
Ore Deposits ◽  
Massive Sulphide ◽  
Isotopic Signatures ◽  
Crustal Block ◽  
Massive Sulphide Deposits ◽  
Sulphide Deposits

This work provides an overview of the geological, geochemical, and metallogenic data available up to date on the Moroccan massive sulphide deposits, including some new results, and then discusses the evidences for the epigenetic and syngenetic hypotheses. All of the ore deposits are located within a crustal block located at the intersection between two major shear zones and are characterized by a sustained and long-lived magmatic activity. The ore deposits are located within second-order shear zones, which played an important role in controlling the geometry of the mineralization. The mineralization lacks the unequivocal textural and structural features that are indicative of a sedimentary or diagenetic origin, and a syntectonic to late-tectonic pyrite-rich assemblage is superimposed on an earlier, pretectonic to syntectonic pyrrhotite-rich mineralization. Each deposit has a distinctive pyrrhotite sulfur isotopic signature, while the sulfur isotopic signature of pyrite is similar in all deposits. Lead isotopes suggest a shift from a magmatic source during the pyrrhotite-rich mineralization to a source that is inherited from the host shales during the pyrite-rich mineralization. The O/H isotopic signatures record a predominance of fluids of metamorphic derivation. These results are consistent with a model in which an earlier pyrrhotite-rich mineralization, which formed during transtension, was deformed and then remobilized to pyrite-rich mineralization during transpression.

The geology and evolution of the Pinchi Fault Zone at Pinchi Lake, central British Columbia

1977 ◽  
Vol 14 (6) ◽  
pp. 1324-1342 ◽  
Author(s):  
I. A. Paterson
Keyword(s):  
Fault Zone ◽  
Subduction Zones ◽  
High Pressures ◽  
Metamorphic Grade ◽  
Fault System ◽  
Late Triassic ◽  
Transform Fault ◽  
The West ◽  
Early Mesozoic ◽  
Complex Fault

At Pinchi Lake, the Pinchi Fault Zone separates the early Mesozoic Takla Group to the east from the late Paleozoic Cache Creek Group to the west. Between these regions a complex fault system involves a series of elongate fault-bounded blocks of contrasting lithology and metamorphic grade. These blocks consist of: (a) highly deformed aragonite–dolomite limestone and blueschist, (b) pumpellyite–aragonite greenstone, (c) a harzburgite–gabbro–diabase–basalt ophiolite sequence, (d) serpentinized alpine ultramafite, and (e) Cretaceous (?) conglomerate. The blueschist probably formed at 8–12 kbar (8 × 105–12 × 105 kPa) and 225–325 °C during a penetrative early deformation which was closely followed by a later deformation associated with a Late Triassic uplift and cooling event. The ophiolite sequence is overlain by Late Triassic sediments which locally contain aragonite suggesting that at least part of the Takla Group may have also undergone high pressure – low temperature metamorphism.The evolution of the 450 km fault zone is discussed and a model is proposed which involves right lateral transform faulting on the Pinchi Fault and underthrusting along northerly dipping subduction zones during the Late Triassic. The blueschist formed at high pressures in such a subduction zone and leaked to the surface in zones of low pressure along an active transform fault.

The Dent Fault System, northern England—reinterpreted as a major oblique-slip fault zone

1988 ◽  
Vol 145 (2) ◽  
pp. 303-316 ◽  
Author(s):  
J. R. UNDERHILL ◽  
R. A. GAYER ◽  
N. H. WOODCOCK ◽  
R. DONNELLY ◽  
E. J. JOLLEY ◽  
...  
Keyword(s):  
Fault Zone ◽  
Fault System
Sign in / Sign up

Export Citation Format

Share Document