scholarly journals U-Pb dates measured in fracture-filling calcites from the SE Pyrenees: syn- or post-kinematic mineral growth?

2021 ◽  
Author(s):  
David Cruset ◽  
Jaume Vergés ◽  
Anna Tarvé
Keyword(s):  
Fluid Flow ◽  
Foreland Basin ◽  
Strike Slip ◽  
Normal Faults ◽  
Thrust Sheet ◽  
Tectonic Transport ◽  
Thrust Sheets ◽  
Interparticle Porosity ◽  
Clumped Isotope ◽  
Geochemical Analyses

<p>Recently, U-Pb dating of fracture-filling carbonates has revealed as a powerful tool to constrain the absolute timing of deformation in fold and thrust belts. However, geochronological studies of these minerals have to be combined with petrological observations and geochemical analyses to decipher if measured dates document fluid flow synchronously to deformation or post-kinematic events.</p><p>The Pyrenean compressional belt formed from Late Cretaceous to Oligocene due to the stacking of three thrust sheets and a deformed foreland basin. From top-and-older to bottom-and-younger, these consist of the Bóixols-Upper Pedraforca, Lower Pedraforca and Cadí thrust sheets and the Ebro foreland basin. Here, we quantify the duration of thrust sheet emplacement and shortening rates in the SE Pyrenees using U-Pb dating of 43 calcites filling fractures and interparticle porosity.</p><p>Four fracture sets related to compressional tectonics and one set related to extension are identified. The compressive sets include: 1) N-S, NNW-SSE and NNE-SSW trending veins; 2) E-W trending folding-related veins; 3) E-W trending reverse faults; and 4) NW-SE and NE-SW trending strike-slip faults. Fractures related to extension are NNW-SSE and NW-SE trending normal faults.</p><p>Elongated blocky, blocky and bladed calcite textures of the dated cements are observed. Elongated textures are observed in reverse, strike-slip and normal faults and occasionally in N-S, NNW-SSE and NNE-SSW and E-W veins. In these fractures, calcite crystals are arranged parallel, oblique, or perpendicular to fracture walls and provide evidence for syn-kinematic growth. Blocky and bladed textures have been identified in N-S, NNW-SSE and NNE-SSW veins, E-W folding-related veins, reverse and strike-slip faults and in calcite precipitated between sedimentary breccia clasts. Although these textures indicate precipitation after vein opening or at lower rates than vein opening, their presence in crack-seal veins and in stepped slickensides also indicates syn-kinematic growth. Moreover, clumped isotope temperatures measured in several blocky and bladed calcites precipitated in veins and faults indicate that most of them precipitated from fluids in thermal disequilibrium with host rocks, revealing rapid fluid flow and precipitation just after fracturing. Contrarily, low temperatures measured in blocky and bladed calcite precipitated in the interparticle porosity of sedimentary breccias indicate late fluid migration.</p><p>U-Pb dating applied to fracture-filling calcites in the SE Pyrenean fold and thrust belt yielded 46 ages from 70.6 ± 0.9 Ma to 2.8 ± 1.8 Ma (Cruset et al., 2020). The results reveal minimum durations for the emplacement of each thrust sheet (18.7 Myr for the Bóixols-Upper Pedraforca, 11.6 Myr for the Lower Pedraforca and 14.3 Myr for the Cadí), and that piggy-back thrusting was accompanied by post-emplacement deformation of upper thrust units above the lower ones during tectonic transport. These estimated durations, combined with the minimum shortening established for the Bóixols-Upper Pedraforca, Lower Pedraforca and Cadí thrust sheets by other methods, allows calculating shortening rates of 0.6 mm/yr, 3.1 mm/yr and 1.1 mm/yr, respectively. Finally, the results also reveal the development of local normal faults at late Oligocene times during the final stages of compression and exhumation.</p><p><strong>References:</strong></p><p><strong>Cruset et al. (2020)</strong>. Geological Society of London. 177, 1186-1196.</p>

Structural analysis of Bic fault, a thrust-related strike-slip fault of the external domain of the Taconic Orogen, Appalachians, Quebec, and metallogenic implications

1991 ◽  
Vol 28 (5) ◽  
pp. 788-799 ◽  
Author(s):  
P. Rhéaume ◽  
K. Schrijver
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Thrust Sheet ◽  
Kink Bands ◽  
Strain Ellipsoid ◽  
Adjacent Part ◽  
External Domain ◽  
Dextral Strike Slip Fault ◽  
Thrust Sheets ◽  
Stage 1

The Bic fault is exposed along the shoreline of the St. Lawrence River, 21 km southwest of Rimouski, for 210 m at Cap à l'Orignal and for 100 m at Cap Enragé. The fault brings in contact two major thrust sheets, the Des Seigneuries and the Des Iles, Cambrian lithologies of the former overlying Ordovician rocks of the latter. In the Taconic Orogen, such contacts are normally thrust faults, but the Bic fault is a dextral strike-slip fault, striking east–west and dipping southward. A study of a narrow zone straddling the fault and an adjacent part of the Des Seigneuries thrust sheet has led to the recognition of four successive stages of deformation, all compatible with a northeast–southwest-trending strain ellipsoid. The two first stages are most important: stage 1 brought about regional folding and faulting, whereas stage 2 was characterized by the development of various structural elements (C–S fabrics, stretching lineation, Riedel shears, and kink bands) exclusive to the fault zone. We infer that (i) in the study area, the Bic fault constituted a lateral ramp along which the Des Seigneuries thrust sheet slid horizontally westward; and (ii) emplacement of Ba–Pb–Zn deposits took place slightly after this movement, probably during regional uplift of the orogen in Late Ordovician to Early Silurian time. The latter hypothesis tends to be corroborated by model lead ages of galena in two deposits.

Dating faults, fractures and fluids with U-Pb calcite geochronology: Application to contrasting fracture and fluid-flow modes of the Cleveland Basin

2020 ◽  
Author(s):  
Jack Lee ◽  
Nick Roberts ◽  
Robert Holdworth ◽  
Andrew Aplin ◽  
Richard Haslam ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fault Zone ◽  
Failure Modes ◽  
Damage Zone ◽  
Source Rocks ◽  
Normal Faults ◽  
Fluid Composition ◽  
Natural Fractures ◽  
Seal Integrity ◽  
Clumped Isotope

<p>Fractures and faults act as important permeable pathways in the subsurface and are of great significance to the petroleum industry and for future Carbon Capture and Storage. Fractures allow fluid-flow through impermeable units such as mudrocks and can affect how these lithologies act as top seals, source rocks and/or unconventional reservoirs. Natural fractures within mudrocks can strongly influence top seal integrity, primary migration and the performance of unconventional (e.g. shale gas) reservoirs. This project studies the exhumed, early-mature, Jurassic mudrock succession of the Cleveland Basin, NE England, combining structural geology with isotope geochemistry and geochronology. The primary objective is to provide an absolute chronology of faulting and fracturing through novel U-Pb geochronology of fracture-fill calcite. The abundance of well-exposed, natural fractures with different orientations and failure modes provides an opportunity to investigate the properties of these fractures, and provide a basin-wide temporal and spatial framework of evolving deformation. The second objective is to use trace element, stable isotope, and clumped isotope analyses, to constrain fluid composition and temperature. In combination, these objectives will provide an integrated understanding of fracturing, faulting and fluid migration during burial and exhumation of a sedimentary basin.</p><p>Current fracture-fill dates from U-Pb geochronology provide intriguing insights into the history of the Cleveland Basin. We have identified and dated three phases of deformation and associated fluid-flow that have contrasting kinematics and fluid-flow regimes. The E-W trending Flamborough Head Fault Zone (FHFZ) bounds the basin to the south, and calcite preserved in one of the major extensional faults provides ages of 64-56 Ma. Calcite from N-S to NNW-SSE trending normal faults and associated fractures in the north of the Cleveland Basin provide ages of 44-25 Ma, revealing a previously unknown phase of Cenozoic faulting, which we speculatively relate to salt-related deformation. Structural and petrographic information suggest that the E-W and N-S trending faults have contrasting fracture-fluid-flow systems. Large (up to 30 cm), chalk hosted, vuggy calcite cements with geopetal sediment-fills in the E-W fault zone suggest it acted as an open fluid conduit with voluminous fluid-flow, linking the shallow sub-surface with deeper levels of the stratigraphy. In contrast, typically thin (<5 mm) vein fills with varying crack-seal-slip type textures in the N-S mudstone-hosted fractures of the Cleveland Basin provide evidence of episodic slip of variable displacement (44-40 Ma); these fracture openings may partly be controlled by pore fluid pressures and pre-date fault movement along the regional Peak Fault and smaller scales N-S faults (40-25 Ma) which are characterised by damage zone calcite mineralisation and extensional jog structures. Initial stable isotopic results are giving indications of fluid temperatures and sourcing which will be built on further by clumped isotope and fluid inclusions work.</p>

A structural analysis of a metamorphic fold–thrust belt, northeast Gagnon terrane, Grenville Province

1992 ◽  
Vol 29 (9) ◽  
pp. 1915-1927 ◽  
Author(s):  
Dennis Brown ◽  
Taoby Rivers ◽  
Tom Calon
Keyword(s):  
Deep Level ◽  
Greenschist Facies ◽  
Thrust Belt ◽  
Structural Elements ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Lake Formation ◽  
Transport Direction ◽  
Tectonic Transport ◽  
Thrust Sheets

Northeast Gagnon terrane is located within the Parautochthonous Belt of the Grenville Orogen, near the projected intersection of the front zones of the Grenville and New Quebec orogens. The area consists principally of supracrustal units of the Early Proterozoic Knob Lake Group, and a newly recognized unit, the Equus Lake formation. Both are intruded by the Middle Proterozoic Shabogamo gabbro. Structural elements in the rocks record evidence of a polyorogenic history that is attributed to both the ca. 1800 Ma Hudsonian and the ca. 1000 Ma Grenvillian orogenies. This paper is concerned with the latter.Grenvillian deformation resulted in the formation of a relatively deep-level fold–thrust belt. Three thrust sheets can be defined on the basis of basal thrusts, variations in morphology and orientation of structural elements, and internal thrust sheet geometry. The polydeformational style of the area, rotation of fold axes into subparallelism with the tectonic transport direction, and internal imbrication lead to a complex internal thrust sheet geometry. Thrusting has produced and inverted the metamorphic gradient, with lower greenschist facies in the basal thrust sheet and upper greenschist facies in the upper thrust sheet.Documentation of the northeastern margin of Gagnon terrane as a north- to northwest-directed metamorphic fold–thrust belt corroborates similar interpretations for Gagnon terrane from elsewhere along the Grenville Front and is in accord with the models of the Grenville Province as a collisional orogen. Furthermore, it is suggested that northeast Gagnon terrane is an exhumed, internal, ductile part of a fold–thrust belt.

scholarly journals The North Pyrenean Frontal Thrust: structure, timing and late fluid circulation inferred from seismic and thermal-geochemical analyses of well data

2021 ◽  
Vol 192 ◽  
pp. 52
Author(s):  
Guillaume Barré ◽  
Charlotte Fillon ◽  
Maxime Ducoux ◽  
Frédéric Mouthereau ◽  
Eric C. Gaucher ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Large Scale ◽  
Foreland Basin ◽  
Fluid Circulation ◽  
Compression Phase ◽  
The North ◽  
Calcite Veins ◽  
Quiescence Period ◽  
Late Generation ◽  
Geochemical Analyses

During orogenesis, large-scale thrusts as orogenic fronts can act as conduits and/or barriers for fluid flow. Unravelling the timing and modes of tectonic activation of large-scale faults is crucial to understanding the relationship between fluid flow and deformation. The North Pyrenean Frontal Thrust (NPFT) corresponds to a major basement-involved thrust responsible for the northward overthrust of the pre-orogenic sediments on top of the Aquitaine Foreland Basin. This study questions the timing of activation of this thrust, its geometry, the nature of the last fluids, which circulated there, and its role on the circulation of fluids. The structural study confronted to published thermochronology data led to determine the timing of the two tectonic activations during the NPFT compression phase and to relate them to the fluid circulations. We constrain the first activation at Campanian times and link it to the leak of the deep gas reservoir present in depth, as the NPFT acted as a conduit. Then the NPFT acted as a barrier, probably due to the breccia consolidation during the Paleocene quiescence period. Finally, the Eocene-Oligocene reactivation led to fluid circulation of high salinity fluids from the Triassic evaporites leaching. This latter event is associated with a fracturing event and the late generation of calcite veins studied here. This is the first study in the Pyrenees directly applied to the NPFT which uses the association between fluid inclusions study, seismic and thermochronological data. It highlights that the NPFT may be an important structure responsible of the leakage of deep hydrocarbons reservoirs. It also shows the importance of the determination of the activation steps of large-scale faults to decipher the origin of fluid circulations in space and time.

scholarly journals Structural evidence of in-sequence and out-of-sequence thrusting in the Karwendel mountains and the tectonic subdivision of the western Northern Calcareous Alps

2019 ◽  
Vol 112 (1) ◽  
pp. 62-83
Author(s):  
Sinah Kilian ◽  
Hugo Ortner
Keyword(s):  
Hanging Wall ◽  
Strike Slip ◽  
Northern Calcareous Alps ◽  
Deformation History ◽  
Structural Geometry ◽  
Thrust Sheet ◽  
Northern Calcareous ◽  
Nappe Tectonics ◽  
Thrust Sheets ◽  
History Of

AbstractWe present the results of a field study in the Karwendel mountains in the western Northern Calcareous Alps, where we analysed the boundary between two major thrust sheets in detail in a key outcrop where nappe tectonics had been recognized already at the beginning of the 20th century. We use the macroscopic structural record of thrust sheet transport in the footwall and hanging wall of this boundary, such as folds, foliation and faults. In the footwall, competent stratigraphic units tend to preserve a full record of deformation while incompetent units get pervasively overprinted and only document the youngest deformation.Transport across the thrust persisted throughout the deformation history of the Northern Calcareous Alps from the late Early Cretaceous to the Miocene. As a consequence of transtensive, S-block down strike-slip tectonics, postdating folding of the major thrust, new out-of-sequence thrusts formed that climbed across the step, and ultimately placed units belonging to the footwall of the initial thrust onto its hanging wall.One of these out-of-sequence thrusts had been used to delimit the uppermost large thrust sheet (Inntal thrust sheet) of the western Northern Calcareous against the next, tectonically deeper, (Lechtal) thrust sheet. Based on the structural geometry of the folded thrust and the age of the youngest sediments below the thrust, we redefine the thrust sheets, and name the combined former Inntal- and part of the Lechtal thrust sheet as the new Karwendel thrust sheet and the former Allgäu- and part of the Lechtal thrust sheet as the new Tannheim thrust sheet.

scholarly journals The role of basement-involved normal faults in the recent tectonics of western Taiwan

2016 ◽  
Vol 153 (5-6) ◽  
pp. 1166-1191 ◽  
Author(s):  
KENN-MING YANG ◽  
RUEY-JUIN RAU ◽  
HAO-YUN CHANG ◽  
CHING-YUN HSIEH ◽  
HSIN-HSIU TING ◽  
...  
Keyword(s):  
Active Faults ◽  
Foreland Basin ◽  
Normal Fault ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Normal Faults ◽  
Thrust Belt ◽  
Structural Style ◽  
Fold And Thrust Belt ◽  
Recent Tectonics

AbstractIn the foreland area of western Taiwan, some of the pre-orogenic basement-involved normal faults were reactivated during the subsequent compressional tectonics. The main purpose of this paper is to investigate the role played by the pre-existing normal faults in the recent tectonics of western Taiwan. In NW Taiwan, reactivated normal faults with a strike-slip component have developed by linkage of reactivated single pre-existing normal faults in the foreland basin and acted as transverse structures for low-angle thrusts in the outer fold-and-thrust belt. In the later stage of their development, the transverse structures were thrusted and appear underneath the low-angle thrusts or became tear faults in the inner fold-and-thrust belt. In SW Taiwan, where the foreland basin is lacking normal fault reactivation, the pre-existing normal faults passively acted as ramp for the low-angle thrusts in the inner fold-and-thrust belt. Some of the active faults in western Taiwan may also be related to reactivated normal faults with right-lateral slip component. Some main earthquake shocks related to either strike-slip or thrust fault plane solution occurred on reactivated normal faults, implying a relationship between the pre-existing normal fault and the triggering of the recent major earthquakes. Along-strike contrast in structural style of normal fault reactivation gives rise to different characteristics of the deformation front for different parts of the foreland area in western Taiwan. Variations in the degree of normal fault reactivation also provide some insights into the way the crust embedding the pre-existing normal faults deformed in response to orogenic contraction.

scholarly journals Strike-slip reactivation of segmented normal faults: Implications for basin structure and fluid flow

2018 ◽  
Vol 30 (6) ◽  
pp. 1264-1279 ◽  
Author(s):  
Atle Rotevatn ◽  
David C. P. Peacock
Keyword(s):  
Fluid Flow ◽  
Strike Slip ◽  
Normal Faults ◽  
Basin Structure

scholarly journals Quantifying deformation processes in the SE Pyrenees using U–Pb dating of fracture-filling calcites

2020 ◽  
Vol 177 (6) ◽  
pp. 1186-1196 ◽  
Author(s):  
D. Cruset ◽  
J. Vergés ◽  
R. Albert ◽  
A. Gerdes ◽  
A. Benedicto ◽  
...  
Keyword(s):  
Normal Faults ◽  
Limiting Factor ◽  
Content Type ◽  
Growth Strata ◽  
Thrust Belts ◽  
Tectonic Transport ◽  
Thrust Sheets ◽  
Deformation Processes ◽  
Dating Method ◽  
Supplementary Material

It is difficult to quantify the timing of the deformation processes in brittle fold–thrust belts because minerals suitable for dating and well-preserved growth strata sediments are scarce or absent. Here, we quantify the duration of thrust sheet emplacement and shortening rates in the SE Pyrenean thrust sequence using U–Pb dating of fracture-filling calcites. The obtained U–Pb dates reveal a minimum duration for the emplacement of each thrust unit (18.7 Ma for the Bóixols–Upper Pedraforca, 11.6 Ma for the Lower Pedraforca and 14.3 Ma for the Cadí thrust sheets) and show that piggy-back thrusting was accompanied by post-emplacement deformation of the upper thrust sheets above the lower sheets during their south-directed tectonic transport. We calculated shortening rates of 0.6, 3.1 and 1.1 mm a−1 from the older to younger emplaced thrust sheets. Our results also reveal the formation of local normal faults during the late Oligocene as a result of the late stages of compression and exhumation in the SE Pyrenees. We observed that temperatures >110 °C could be a limiting factor when applying the U–Pb dating method.Supplementary material: U-Pb analytical results, concordia plots and fracture data are available at https://doi.org/10.6084/m9.figshare.c.5078862

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

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