scholarly journals Syncing fault rock clocks: Direct comparison of U-Pb carbonate and K-Ar illite fault dating methods

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1179-1183
Author(s):  
C.M. Mottram ◽  
D.A. Kellett ◽  
T. Barresi ◽  
H. Zwingmann ◽  
M. Friend ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fault Slip ◽  
Yukon Territory ◽  
Fault Reactivation ◽  
Radiometric Dating ◽  
Fault System ◽  
Fault Rock ◽  
Fault Strength ◽  
Dextral Strike Slip Fault ◽  
Fault Valve

Abstract The timing of slip on brittle faults in Earth’s upper crust is difficult to constrain, and direct radiometric dating of fault-generated materials is the most explicit approach. Here we make a direct comparison between K-Ar dating of fault gouge clay (authigenic illite) and U-Pb dating of carbonate slickenfibers and veins from the same fault. We have dated fault generated materials from the Big Creek fault, a northwest-striking, dextral strike-slip fault system in Yukon Territory, Canadian Cordillera. Both methods yielded dates at ca. 73 Ma and ca. 60–57 Ma, representing at least two periods of fault slip that form part of a complex fault and fluid-flow history. The Cretaceous result lies within previous indirect estimates for major slip on the fault. The Paleocene–Eocene result coincides with the estimated timing of slip of the nearby Tintina and Denali faults, which are crustal-scale, northwest-striking dextral faults, indicating Big Creek fault reactivation during regional faulting. The coincidence of periods of carbonate-crystallizing fracturing and fluid flow with intervals of seismic, gouge-generating slip supports the fault valve model, where fault strength is mediated by fluid pressures, and fluid emplacement requires seismic pumping in otherwise impermeable aseismic fault zones. The reproducibility of slip periods for distinct fault-generated materials using different decay systems indicates that these methods provide complimentary results and can be reliably applied to date brittle fault slip, opening new opportunities for investigating fault conditions with associated mineralizing fluid events.

Tectonic evolution of the seismically active western continental margin of the Indian plate: Implications for kinematic history and fluid flow

2020 ◽  
Author(s):  
Mohamedharoon Shaikh ◽  
Deepak Maurya ◽  
Mukherjee Soumyajit ◽  
Naimisha Vanik ◽  
Abhishek Kumar ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Continental Margin ◽  
Deformation Band ◽  
Fault Slip ◽  
Indian Plate ◽  
Fault System ◽  
Tectonic Activity ◽  
Deformation Bands ◽  
Deformation History ◽  
Kachchh Basin

<p>The deformation history along the E-W trending Kachchh rift basin at the western continental margin of the Indian plate located in the state of Gujarat, India, has been controlled by activation of NW-SE, NE-SW and E-W trending, 0.25–50 km long oblique-slip and dip-slip faults.</p><p>The study is an attempt to establish the kinematic framework along sub-parallel, NW-SE striking group of intra-uplift, striated, high-angle reverse faults, consisting of, Vigodi Fault (VF) and its bifurcation – West Vigodi Fault (WVF), Gugriana Fault (GUF) and its bifurcation – Khirasra fault (KHIF) from the western part of the Kachchh basin in the northern part of Gujarat state in western India. They meet the E-W trending master faults – the Kachchh Mainland Fault (KMF) to the north and the Katrol Hill Fault (KHF) to the south at an acute angle.</p><p>Fault-slip data consisting of fault plane and slickenside attitudes along with other kinematic indicators were recorded along the faults at 69 structural stations. A total of 1258 fault-slip data were used to carry out paleostress analysis using Win-Tensor (v.5.8.8) and T-Tecto Studio X5 by executing the Right Dihedral Method.</p><p>The NW-SE trending fault system exposes highly porous and permeable deformed sandstones belonging to the Jhuran and Bhuj Formation. The pure compaction bands, cataclastic deformation band clusters, slipped deformation bands and deformation band faults are documented. These tabular structures are densely populated in the fault damage zones of VF, WVF, GUF and KHIF. The field observations related to fluid flow conduits are discussed. We also present the field characteristics and petrographic evidences of chemical bleaching caused by fluid-rock interaction found in the Bhuj and the Jhuran sandstones. The change in the coloration pattern of deformation bands in comparison with the host rock color, presence of iron concretions, iron rinds and liesegang rings are important records of the diagenetic control over the fluid flow. The study is an attempt to the link the tectonic activity and simultaneous chemical reactions that affect the fluid flow transport.</p><p>We attribute the deformation history in the western continental margin of the Indian plate has been dominantly controlled by intraplate compressional stresses induced by anticlockwise rotation and collision of the Indian plate with the Eurasian plate at ~55 Ma. This correlates well with the Kachchh basin where rifting aborted during the Late Cretaceous, accommodated syn-rifting extensional component in the intra-uplift VF, GUF and KHIF. It has then undergone inversion phase due to onset of compressive stresses during the Post-Deccan Trap time up to the present. The NW-SE trending intra-uplift faults reactivated multiple times and generated deformation bands having high porosity contrast with the host Bhuj sandstone.</p>

Fault interaction and strain partitioning in southeastern Tibetan Plateau: from kinematics to geodynamics

2020 ◽  
Author(s):  
Li Yin
Keyword(s):  
Tibetan Plateau ◽  
Fault Slip ◽  
Fault System ◽  
Strain Partitioning ◽  
Fault Interaction ◽  
Slip Rates ◽  
Southeastern Tibetan Plateau ◽  
Fault Systems ◽  
Fault Strength ◽  
Fault Slip Rates

<p>In southeastern Tibetan Plateau, the Xianshuihe-Xiaojiang fault system (XXFS) and its neighboring fault systems collectively accommodates the material extrusion of the Tibetan Plateau. However we do not mechanically understand how these faults interact with each other and how the fault interaction impacts strain partitioning, fault slip rates, and seismicity in this region. We develop and use a three-dimensional viscoelastoplastic finite element model to simulate regional deformation, fault slip rates, and fault interaction in the fault system of southeastern Tibetan Plateau. We investigate the effects of inception and activity of faults, fault strength, lithospheric rheology, and topography on partitioning of strain and fault slip rates. Model results show that fault strength, lithospheric rheology, and topography all significantly influence the strain partitioning and slip rates on faults. The initiation of the Daliangshan fault results mainly from the non-smooth fault geometry of the main trace of the XXFS. Our model results support the hypothesis of codependent slip rate between fault systems. For the present fault configuration, our model predicts localized strain in the Daliangshan faults, Yingjing-Mabian faults, and Lianfeng-Zhaotong faults, where numerous earthquakes occurred in recent years.</p>

scholarly journals Coseismic fault-slip distribution of the 2019 Ridgecrest Mw6.4 and Mw7.1 earthquakes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yang Gao ◽  
HuRong Duan ◽  
YongZhi Zhang ◽  
JiaYing Chen ◽  
HeTing Jian ◽  
...  
Keyword(s):  
Strike Slip ◽  
Fault Slip ◽  
Slip Distribution ◽  
Synthetic Aperture ◽  
Seismic Events ◽  
Interferometric Synthetic Aperture Radar ◽  
The Past ◽  
Dextral Strike Slip Fault ◽  
Fault Slip Distribution ◽  
Dextral Strike Slip

AbstractThe 2019 Ridgecrest, California seismic sequence, including an Mw6.4 foreshock and Mw7.1 mainshock, represent the largest regional seismic events within the past 20 years. To obtain accurate coseismic fault-slip distribution, we used precise positioning data of small earthquakes from January 2019 to October 2020 to determine the dip parameters of the eight fault geometry, and used the Interferometric Synthetic Aperture Radar (InSAR) data processed by Xu et al. (Seismol Res Lett 91(4):1979–1985, 2020) at UCSD to constrain inversion of the fault-slip distribution of both earthquakes. The results showed that all faults were sinistral strike-slips with minor dip-slip components, exception for dextral strike-slip fault F2. Fault-slip mainly occurred at depths of 0–12 km, with a maximum slip of 3.0 m. The F1 fault contained two slip peaks located at 2 km of fault S4 and 6 km of fault S5 depth, the latter being located directly above the Mw7.1hypocenter. Two slip peaks with maximum slip of 1.5 m located 8 and 20 km from the SW endpoint of the F2 fault were also identified, and the latter corresponds to the Mw6.4 earthquake. We also analyzed the influence of different inversion parameters on the fault slip distribution, and found that the slip momentum smoothing condition was more suitable for the inversion of the earthquakes slip distribution than the stress-drop smoothing condition.

scholarly journals Fault reactivation and strain partitioning across the brittle-ductile transition

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1127-1130 ◽  
Author(s):  
Gabriel G. Meyer ◽  
Nicolas Brantut ◽  
Thomas M. Mitchell ◽  
Philip G. Meredith
Keyword(s):  
Fault Slip ◽  
Fault Reactivation ◽  
Ductile Deformation ◽  
Tectonic Deformation ◽  
Gradual Change ◽  
Bulk Rock ◽  
Total Deformation ◽  
Bulk Strain ◽  
Brittle Ductile Transition ◽  
Ductile Flow

Abstract The so-called “brittle-ductile transition” is thought to be the strongest part of the lithosphere, and defines the lower limit of the seismogenic zone. It is characterized not only by a transition from localized to distributed (ductile) deformation, but also by a gradual change in microscale deformation mechanism, from microcracking to crystal plasticity. These two transitions can occur separately under different conditions. The threshold conditions bounding the transitions are expected to control how deformation is partitioned between localized fault slip and bulk ductile deformation. Here, we report results from triaxial deformation experiments on pre-faulted cores of Carrara marble over a range of confining pressures, and determine the relative partitioning of the total deformation between bulk strain and on-fault slip. We find that the transition initiates when fault strength (σf) exceeds the yield stress (σy) of the bulk rock, and terminates when it exceeds its ductile flow stress (σflow). In this domain, yield in the bulk rock occurs first, and fault slip is reactivated as a result of bulk strain hardening. The contribution of fault slip to the total deformation is proportional to the ratio (σf − σy)/(σflow − σy). We propose an updated crustal strength profile extending the localized-ductile transition toward shallower regions where the strength of the crust would be limited by fault friction, but significant proportions of tectonic deformation could be accommodated simultaneously by distributed ductile flow.

Insights on fault reactivation during the 2019, Mw4.9 Le Teil earthquake in southeastern France, from a joint 3D geology and InSAR study

2021 ◽  
Author(s):  
Léo Marconato ◽  
Philippe-Hervé Leloup ◽  
Cécile Lasserre ◽  
Séverine Caritg ◽  
Romain Jolivet ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Displacement ◽  
Fault Reactivation ◽  
Least Square ◽  
Shallow Depth ◽  
Slip Distribution ◽  
Fault System ◽  
Geological Model ◽  
Coseismic Slip ◽  
3D Geological Model

<div> <div> <div> <p>The 2019, M<sub>w</sub>4.9 Le Teil earthquake occurred in southeastern France, causing important damage in a slow deforming region. Field based, remote sensing and seismological studies following the event revealed its very shallow depth, a rupture length of ~5 km with surface rupture evidences and a thrusting mechanism. We further investigate this earthquake by combining geological field mapping and 3D geology, InSAR time series analysis and coseismic slip inversion.</p> <p>From structural, stratigraphic and geological data collected around the epicenter, we first produce a 3D geological model over a 70 km<sup>2</sup> and 3 km deep zone surrounding the 2019 rupture, using the GeoModeller software. This model includes the geometry of the main faults and geological layers, and especially a geometry for La Rouvière Fault, an Oligocene normal fault likely reactivated during the earthquake.</p> <p>We also generate a time series of the surface displacement by InSAR, based on Sentinel-1 data ranging from early January 2019 to late January 2020, using the NSBAS processing chain. The spatio-temporal patterns of the surface displacement for this limited time span show neither clear pre-seismic signal nor significant postseismic slip. We extract from the InSAR time series the coseismic displacement pattern, and in particular the along-strike slip distribution that shows spatial variations. The maximum relative displacement along the Line-Of-Sight is up to ~16 cm and is located in the southwestern part of the rupture.</p> <p>We then invert for the slip distribution on the fault from the InSAR coseismic surface displacement field. We use a non-negative least square approach based on the CSI software and the fault surface trace defined in the 3D geological model, exploring the range of plausible fault dip values. Best-fitting dips range between 55° and 60°. Such values are slightly lower than those measured on La Rouvière Fault planes in the field. Our model confirms the reactivation of La Rouvière fault, with reverse slip at very shallow depth and two main slip patches reaching 30 cm and 24 cm of slip at 400-500m depth. We finally discuss how the 3D fault geometry and geological configuration could have impacted the slip distribution and propagation during the earthquake.</p> <p>This study is a step to better quantify strain accumulation and assess the seismic hazard associated with other similar faults along the Cévennes fault system, in a densely populated area hosting several nuclear plants.</p> </div> </div> </div>

Hydrofractures and crustal-scale fluid flow

2021 ◽  
Author(s):  
Paul D. Bons ◽  
Tamara de Riese ◽  
Enrique Gomez-Rivas ◽  
Isaac Naaman ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Large Scale ◽  
Low Flow ◽  
Fault System ◽  
Tectonic Activity ◽  
Field Evidence ◽  
Dehydration Reactions ◽  
Matrix Flow ◽  
Matrix Porosity ◽  
Fluid Sources

<p>Fluids can circulate in all levels of the crust, as veins, ore deposits and chemical alterations and isotopic shifts indicate. It is furthermore generally accepted that faults and fractures play a central role as preferred fluid conduits. Fluid flow is, however, not only passively reacting to the presence of faults and fractures, but actively play a role in their creation, (re-) activation and sealing by mineral precipitates. This means that the interaction between fluid flow and fracturing is a two-way process, which is further controlled by tectonic activity (stress field), fluid sources and fluxes, as well as the availability of alternative fluid conduits, such as matrix porosity. Here we explore the interaction between matrix permeability and dynamic fracturing on the spatial and temporal distribution of fluid flow for upward fluid fluxes. Envisaged fluid sources can be dehydration reactions, release of igneous fluids, or release of fluids due to decompression or heating.</p><p> </p><p>Our 2D numerical cellular automaton-type simulations span the whole range from steady matrix-flow to highly dynamical flow through hydrofractures. Hydrofractures are initiated when matrix flow is insufficient to maintain fluid pressures below the failure threshold. When required fluid fluxes are high and/or matrix porosity low, flow is dominated by hydrofractures and the system exhibits self-organised critical phenomena. The size of fractures achieves a power-law distribution, as failure events may sometimes trigger avalanche-like amalgamation of hydrofractures. By far most hydrofracture events only lead to local fluid flow pulses within the source area. Conductive fracture networks do not develop if hydrofractures seal relatively quickly, which can be expected in deeper crustal levels. Only the larger events span the whole system and actually drain fluid from the system. We present the 10 square km hydrothermal Hidden Valley Mega-Breccia on the Paralana Fault System in South Australia as a possible example of large-scale fluid expulsion events. Although field evidence suggests that the breccia formed over a period of at least 150 Myrs, actual cumulative fluid duration may rather have been in the order of days only. This example illustrates the extreme dynamics that crustal-scale fluid flow in hydrofractures can achieve.</p>

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