scholarly journals Early gold-bearing quartz veins within the Rivière-Héva fault zone, Abitibi subprovince, Quebec, Canada

2018 ◽  
Vol 55 (10) ◽  
pp. 1139-1157 ◽  
Author(s):  
Francis Guay ◽  
Pierre Pilote ◽  
Réal Daigneault ◽  
Vicki McNicoll
Keyword(s):  
Fault Zone ◽  
Thrust Fault ◽  
Fault Zones ◽  
Ductile Deformation ◽  
Vein System ◽  
Quartz Veins ◽  
Abitibi Subprovince ◽  
Major Fault ◽  
High Degree ◽  
Gold Bearing

The Malartic Lakeshore showing is a gold-bearing quartz vein system located within the major Rivière-Héva fault zone (RHFZ) of the southern Abitibi greenstone belt. This fault separates the 2702–2700 Ma felsic Héva Formation from the 2708 Ma mafic-ultramafic Dubuisson Formation. A swarm of thin diorite dykes with lamprophyric facies and gold-bearing quartz veins are present only on the Dubuisson side of the fault. The 30–70 cm thick gold quartz veins are boudinaged and folded. Veins are banded and associated with pyrite, chalcopyrite, galena, barite, and gold. The study area is characterized by a high degree of ductile deformation associated with the RHFZ and manifested by the southeast-trending “principal schistosity” (Sp). Stretching lineations plunge moderately to shallowly toward the southeast as a result of shortening followed by late directional shearing during a transpressive deformation. A sample from the Héva Formation yielded a zircon U–Pb age of 2698.2 ± 0.8 Ma, and a diorite dyke produced an age of 2694.3 ± 2.5 Ma. Quartz veins are crosscut by dykes, and both are affected by the Sp fabric, indicating an early emplacement with respect to the deformation. This situation contrasts with the orogenic gold veins found in association with major fault zones. A near-synvolcanic magmatic hydrothermal origin is proposed for this gold vein system. Because all subvertical units in the area are south facing, the presence of the older Dubuisson Formation over the younger Héva Formation is attributed to the RHFZ acting as a significant reverse or thrust fault.

DETAIL GRAVITY PROFILE ACROSS SAN ANDREAS FAULT ZONE

Geophysics ◽  
1967 ◽  
Vol 32 (2) ◽  
pp. 297-301 ◽  
Author(s):  
S. N. Domenico
Keyword(s):  
Fault Zone ◽  
Mojave Desert ◽  
San Andreas Fault ◽  
Surface Expression ◽  
Fault Zones ◽  
Rock Masses ◽  
San Andreas ◽  
Major Fault ◽  
Reduced Density ◽  
Gravity Profile

A gravity profile was obtained from closely spaced readings along a traverse approximately nine miles in length across the San Andreas fault zone immediately south of Palmdale, California in the western Mojave Desert. Corrected gravity values show a slight but distinctive minimum associated with the fault zone which may be attributed to the reduced density of the shattered rock masses in the fault zone. The existence of this minimum suggests that major fault zones may be traced across terrain, on which surface expression of the fault does not exist, by successive profiles across the suspected position of the fault zone.

Origin of the Piché Structural Complex and implications for the early evolution of the Archean crustal-scale Cadillac – Larder Lake Fault Zone, Canada

2018 ◽  
Vol 55 (8) ◽  
pp. 905-922 ◽  
Author(s):  
Pierre Bedeaux ◽  
Lucie Mathieu ◽  
Pierre Pilote ◽  
Silvain Rafini ◽  
Réal Daigneault
Keyword(s):  
Fault Zone ◽  
Cross Sections ◽  
Volcanic Rocks ◽  
Sedimentary Basins ◽  
Drill Hole ◽  
Gold Deposits ◽  
Ductile Deformation ◽  
Chemical Compositions ◽  
Abitibi Subprovince ◽  
Felsic Volcanic

The Piché Structural Complex (PSC) extends over 150 km within the Cadillac – Larder Lake Fault Zone (CLLFZ), a gold-endowed, east-trending, and high-strain corridor located along the southern edge of the Archean Abitibi Subprovince. The PSC consists of discontinuous units of volcanic rocks (<1 km thick) that host multiple gold deposits. It is spatially associated with molasse-type Timiskaming sedimentary basins. This study describes and interprets the origin of structures and lithologies within the poorly understood PSC to unravel the tectonic evolution of the CLLFZ. Field mapping, chemical analyses, as well as interpretations of cross-sections from drill-hole data, were used to interpret the geometry and structure of the PSC. The PSC is subdivided into six homogeneous fault-bounded segments or slivers. These slivers consist mostly of ultramafic to intermediate volcanic rocks and include some felsic volcanic flows and intrusions. Volcanic facies, chemical compositions, and isotopic ages confirm that these slivers are derived from the early volcanic units of the southern Abitibi greenstone belt, which are located north of the CLLFZ. Cross-cutting relationships between volcanic rocks of the PSC and the Timiskaming-aged intrusions suggest that the slivers were inserted into the CLLFZ during the early stages of the accretion-related deformation (<2686 Ma) and prior to Timiskaming sedimentation and ductile deformation (>2676 Ma). The abundant ultramafic rocks located within the CLLFZ may have focused strain, thereby facilitating the nucleation of the fault as well as the displacements along this crustal-scale structure.

scholarly journals Inner structure and kinematics of the Sushchany-Perga fault zone of the Ukrainian Shield according to the tectonophysical study

2021 ◽  
Vol 43 (1) ◽  
pp. 142-159
Author(s):  
S.V. Mychak ◽  
L.V. Farfuliak
Keyword(s):  
Fault Zone ◽  
River Basin ◽  
Shear Zones ◽  
Thrust Fault ◽  
Fault Zones ◽  
Ukrainian Shield ◽  
Fault Type ◽  
Fracture Formation ◽  
Five Phases

The field tectonophysical works were carried out in the upper reaches of the Ubort River basin along the Zolnia-Maidan-Kopischany fault. The research aim was determination of the inner structure and kinematics of the Sushchany-Perga fault zone of the western pfrt of the Ukrainian Shield. For investigation of fracturing and structural-textural elements of rocks the structural-paragenetic method of tectonophysics was used. It was determined that formation of the Sushchany-Perga fault zone continued during at least five phases of deformation. They were accompanied by the formation of differently oriented shear zones: Khmelivka, Sushchany, Perga, Rudnia-Khochin, Lopatychi. The Khmelivka and Sushchany shear zones are similar to striking of the Nemyriv and Khmelnik fault zones of the Ukrainian shield, which belong to the Nemyriv stage of faulting (~1.99 Ga). The Rudnia-Khochin and Perga phases are related to the fact that the Sushchany-Perga fault zone was quite active during the junction of the Fennoscandia and Sarmatia microplates. We have established that the development of thrust fault and normal down throw fault type shears, which took place in an area of compression and extension, respectively, is associated with the formation period of the Perga granitoids complex (1.80—1.70 Ga).This alternation of the compression and extension conditions has led to formation of the ore occurrences and deposits within the Perga tectonic joint. This investigation found that the Sushchany-Perga fault zone arose in the Late Paleoproterozoic at the Nemirov stage of fracture formation, simultaneously with Goryn, Lutsk, Teteriv and Nemyriv fault zones as a result of the junction of two ancient microplates — Fennoscandia and Sarmatia.

scholarly journals Quantitative determination of the lowest density domain in major fault zones via medical X-ray computed tomography

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Akiyuki Iwamori ◽  
Hideo Takagi ◽  
Nobutaka Asahi ◽  
Tatsuji Sugimori ◽  
Eiji Nakata ◽  
...  
Keyword(s):  
Fault Zone ◽  
Atomic Number ◽  
Density Ratio ◽  
Effective Atomic Number ◽  
Fault Zones ◽  
Ct Number ◽  
Fault Rock ◽  
Major Fault ◽  
X Ray Computed

AbstractDetermination of the youngest active domains in fault zones that are not overlain by Quaternary sedimentary cover is critical for evaluating recent fault activity, determining the current local stress field, and mitigating the impacts of future earthquakes. Considering the exhumation of a fault zone, the youngest active domain in a fault zone is supposed to correspond to the activity at the minimum fault depth of a buried fault, such that the most vulnerable area, which possesses the lowest rock/protolith density ratio, is assumed to be indicative of this recent fault activity. However, it is difficult to measure the density of fault rocks and map the rock/protolith density ratio across a given fault zone. Here, we utilize medical X-ray computed tomography (CT), a non-destructive technique for observing and analyzing materials, to investigate the fault characteristics of several fault zones and their surrounding regions in Japan, and attempt to determine the lowest density domain of a given fault zone based on its CT numbers, which are a function of the density and effective atomic number of the fault rock and protolith. We first investigate the density, void ratio, and effective atomic number of active and inactive fault rocks, and their respective protoliths. We then calculate the CT numbers after reducing the beam-hardening effects on the rock samples and study the relationships among the CT number, density, and effective atomic number. We demonstrate that the density, effective atomic number, and CT number of the fault rock decrease as the youngest active zone, identified by outcrop observation, are approached, such that the region with the lowest CT number and rock/protolith density ratio defines the lowest density domain of a given fault zone. We also discuss the relationship between the lowest density domain and the youngest active domain in major fault zones and investigate the points to be considered when the youngest active domain is identified from the lowest density domain determined by the CT number.

Alpine ultramafic rocks of southwestern British Columbia

1982 ◽  
Vol 19 (6) ◽  
pp. 1156-1173 ◽  
Author(s):  
R. L. Wright ◽  
Joe Nagel ◽  
K. C. McTaggart
Keyword(s):  
British Columbia ◽  
Fault Zone ◽  
Fault Zones ◽  
Ultramafic Rocks ◽  
Fraser River ◽  
Major Fault ◽  
Mechanical Injection

Ultramafic rocks of the Hozameen, Bridge River, and Cache Creek ophiolite assemblages show much variety. The Coquihalla belt of the Hozameen ophiolite assemblage, almost completely serpentinized, is elongate, narrow, and lies along a major fault. Three ultramafic bodies from the Bridge River ophiolite differ markedly from each other. (1) The Pioneer peridotite is a relatively small lens (4 km by 2 km), unaltered, well layered, and fault bounded. (2) The Shulaps body, one of the largest in British Columbia, is bounded on the northeast by a major fault and shows a wide mélange zone on the southwest. (3) A serpentinite body at Lillooet appears to be a steeply dipping slab in the Fraser River fault zone. At Cache Creek, serpentinite bodies are small and appear to be fragments in a mélange. Layers, transgressive sheets, and pods in the Pioneer and Shulaps bodies originated in the mantle, probably by one or several processes: metamorphic differentiation, metasomatism, and mechanical injection. Some ultramafic bodies were emplaced onto the crust by obduction but others, strongly serpentinized, that lie in fault zones may have been squeezed into their present positions.

Fluids and hydrothermal alteration assemblages in a Devonian gold-bearing hot-spring system, Rhynie, Scotland

2003 ◽  
Vol 94 (4) ◽  
pp. 309-324 ◽  
Author(s):  
M. Baron ◽  
S. Hillier ◽  
C. M. Rice ◽  
K. Czapnik ◽  
J. Parnell
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Hot Spring ◽  
Medium Temperature ◽  
Low Salinity ◽  
Major Fault ◽  
Spring System ◽  
Gold Bearing

ABSTRACTHydrothermal alteration at Rhynie, Aberdeenshire, Scotland, is concentrated along a fault zone, which juxtaposes surface deposits and the mineralised feeder zone to the Rhynie hotspring system. Mineralisation consists of breccias and veins filled with quartz, chert, calcite, K-feldspar and pyrite. Associated pervasive alteration comprises a high-temperature K-feldsparquartz-illite facies (formed at 250–350°C), a medium-temperature mixed layered illite/smectitequartz-K-feldspar-chlorite-calcite facies (formed at 150–200°C) and a low-temperature mixed layered illite/smectite-chlorite-calcite facies (formed at 100 to +150°C). The fluids responsible for mineralisation were mainly moderate- to high-temperature (Th =91–360°C), low-salinity (<0·2 to 2·9 wt.% NaCl eq.) H2O-NaCl-heated meteoric fluids comparable to modern and ancient hot-spring systems. The migration of these fluids was mainly restricted to a major fault zone bounding the Devonian basin. Fluids responsible for mineralisation, alteration and cementation elsewhere in the basin were low-temperature (Th 57 to 161°C), low- to high-salinity (<0·2 to 18 wt.% NaCl eq.) H2O-NaCl fluids, which resemble basinal brines.

scholarly journals Active Faulting in Lake Constance (Austria, Germany, Switzerland) Unraveled by Multi-Vintage Reflection Seismic Data

2021 ◽  
Vol 9 ◽  
Author(s):  
S.C. Fabbri ◽  
C. Affentranger ◽  
S. Krastel ◽  
K. Lindhorst ◽  
M. Wessels ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Data ◽  
Single Channel ◽  
Fault Zones ◽  
Lake Constance ◽  
Earthquake Catalog ◽  
Tectonic Structures ◽  
Reflection Seismic ◽  
The North ◽  
Major Fault

Probabilistic seismic hazard assessments are primarily based on instrumentally recorded and historically documented earthquakes. For the northern part of the European Alpine Arc, slow crustal deformation results in low earthquake recurrence rates and brings up the necessity to extend our perspective beyond the existing earthquake catalog. The overdeepened basin of Lake Constance (Austria, Germany, and Switzerland), located within the North-Alpine Molasse Basin, is investigated as an ideal (neo-) tectonic archive. The lake is surrounded by major tectonic structures and constrained via the North Alpine Front in the South, the Jura fold-and-thrust belt in the West, and the Hegau-Lake Constance Graben System in the North. Several fault zones reach Lake Constance such as the St. Gallen Fault Zone, a reactivated basement-rooted normal fault, active during several phases from the Permo-Carboniferous to the Mesozoic. To extend the catalog of potentially active fault zones, we compiled an extensive 445 km of multi-channel reflection seismic data in 2017, complementing a moderate-size GI-airgun survey from 2016. The two datasets reveal the complete overdeepened Quaternary trough and its sedimentary infill and the upper part of the Miocene Molasse bedrock. They additionally complement existing seismic vintages that investigated the mass-transport deposit chronology and Mesozoic fault structures. The compilation of 2D seismic data allowed investigating the seismic stratigraphy of the Quaternary infill and its underlying bedrock of Lake Constance, shaped by multiple glaciations. The 2D seismic sections revealed 154 fault indications in the Obersee Basin and 39 fault indications in the Untersee Basin. Their interpretative linkage results in 23 and five major fault planes, respectively. One of the major fault planes, traceable to Cenozoic bedrock, is associated with a prominent offset of the lake bottom on the multibeam bathymetric map. Across this area, high-resolution single channel data was acquired and a transect of five short cores was retrieved displaying significant sediment thickness changes across the seismically mapped fault trace with a surface-rupture related turbidite, all indicating repeated activity of a likely seismogenic strike-slip fault with a normal faulting component. We interpret this fault as northward continuation of the St. Gallen Fault Zone, previously described onshore on 3D seismic data.

Occurrence and possible tectonic significance of high-pressure granulite fragments in the Tulemalu fault zone, District of Keewatin, N.W.T., Canada

1986 ◽  
Vol 23 (12) ◽  
pp. 1950-1962 ◽  
Author(s):  
S. Tella ◽  
K. E. Eade
Keyword(s):  
Fault Zone ◽  
Fault Zones ◽  
Ductile Deformation ◽  
Lower Grade ◽  
Mineral Association ◽  
The West ◽  
High Pressure Granulite ◽  
Tectonic Significance ◽  
Isothermal Decompression ◽  
Textural Evidence

Fragments of garnet–clinopyroxene granulite with corona textures in ductilely deformed lower-amphibolite-grade quartzofeldspathic granitoid gneiss are exposed within the northeast-trending Tulemalu fault zone. The mineral association of the fragments is garnet–clinopyroxene–plagioclase(An20–An22)–quartz–opaques–hornblende–biotite. Textural evidence suggests that hornblende and biotite are late overgrowth minerals. Garnet and clinopyroxene and (or) hornblende are separated by a narrow rim of plagioclase. Pressure–temperature estimates based on currently used geothermobarometers are of the order of 715–789 °C and 10.2–11.4 kbar (1 kbar = 100 MPa) for the garnet–clinopyroxene–plagioclase–quartz assemblage. The fragments are interpreted as relicts of deep-crustal materials, uplifted to higher levels probably as xenolithic rafts in a granitic melt along the fault zone during late Archean or Early Proterozoic ductile displacements. The growth of hornblende and the development of plagioclase reaction rims around garnet are believed to be due to isothermal decompression reactions during uplift.On the basis of limited geological data, paired gravity anomaly patterns, and aeromagnetic interpolation, the Tulemalu fault zone is postulated as representing the northeasterly extension of the Virgin River – Black Lake fault zones of Saskatchewan and represents an approximately 5 km wide ductile deformation zone that separates an Archean granulite terrane to the west from a relatively lower grade terrane composed of Archean supracrustal rocks to the east.

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