Fluid flow history from damage zone cements near the Dent and Rawthey faults, NW England

Abstract. The permeability of magma in shallow volcanic conduits controls the fluid flow and pore pressure development that regulates gas emissions and the style of volcanic eruptions. The architecture of the permeable porous structure is subject to changes as magma deforms and outgasses during ascent. Here, we present a high-resolution study of the permeability distribution across two conduit shear zones (marginal and central) developed in the dacitic spine that extruded towards the closing stages of the 1991–1995 eruption at Unzen volcano, Japan. The marginal shear zone is approximately 3.2 m wide and exhibits a 2-m wide, moderate shear zone with porosity and permeability similar to the conduit core, transitioning into a ~1-m wide, highly-sheared region with relatively low porosity and permeability, and an outer 20-cm wide cataclastic fault zone. The low porosity, highly-sheared rock further exhibits an anisotropic permeability network with slightly higher permeability along the shear plane (parallel to the conduit margin) and is locally overprinted by oblique dilational Riedel fractures. The central shear zone is defined by a 3-m long by ~9-cm wide fracture ending bluntly and bordered by a 15–40 cm wide damage zone with an increased permeability of ~3 orders of magnitude; directional permeability and resultant anisotropy could not be measured from this exposure. We interpret the permeability and porosity of the marginal shear zone to reflect the evolution of compactional (i.e., ductile) shear during ascent up to the point of rupture, estimated by Umakoshi et al. (2008), at ~500 m depth. At this point the compactional shear zone would have been locally overprinted by brittle rupture, promoting the development of a shear fault and dilational Riedel fractures during repeating phases of increased magma ascent rate, enhancing anisotropic permeability that channels fluid flow into, and along, the conduit margin. In contrast, we interpret the central shear zone as a shallow, late-stage dilational structure, which partially tore the spine core with slight displacement. We explore constraints from monitored seismicity and stick-slip behaviour to evaluate the rheological controls, which accompanied the upward shift from compactional toward dilational shear as magma approached the surface, and discuss their importance in controlling the permeability development of magma evolving from overall ductile to increasingly brittle behaviour during ascent and eruption.

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Clay minerals from the Arkitsa fault gouge zone, in Central Greece, and implications for fluid flow

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11095 ◽

2017 ◽

Vol 47 (2) ◽

pp. 616 ◽

Cited By ~ 1

Author(s):

D. Papoulis ◽

D. Romiou ◽

S. Kokkalas ◽

P. Lampropoulou

Keyword(s):

Fluid Flow ◽

Clay Minerals ◽

Fault Zone ◽

Damage Zone ◽

Fault Gouge ◽

Hydrothermal Conditions ◽

Core Zone ◽

Damage Area ◽

Central Greece ◽

Alkaline Conditions

Clay minerals in shallow fault rocks are increasingly recognized as key to the mechanical and seismogenic behavior of faults and fluid flow circulation within the fault core and the surrounding damage zone. We therefore studied faultgouge mineralogy from samples derived from the ENE-trending Arkitsa fault zone, in east-central Greece, in order to testify if the fault is acting as a channel for fluid flow and whether the conditions that characterize the flow can be identified. Clay-gouge samples were collected within the fault core zone, as well as in the broader fault damage area. Consequently, the samples were analyzed by X-Ray Diffraction, SEM and Electron microprobe analyses. The minerals that were identified within the centre of the fault zone are: Montmorillonite, corrensite, illite, micro-calcite, dolomite, quartz, plagioclase and K-feldspars. The absence of corrensite, a clay mineral usually formed in hydrothermal conditions, in the samples from the broader fault damage area indicates that the circulation of hydrothermal fluids is mostly confined within and around the fault core zone. The assemblages within the fault gouge zone and especially the presence of corrensite, combined with the absence of laumontite, indicate hydrothermal alteration at neutral to alkaline conditions and a temperature range at about 100-150 oC.

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

10.5194/egusphere-egu2020-5387 ◽

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>

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Sensitivity of fluid flow to deformation-band damage zone heterogeneities: A study using fault facies and truncated Gaussian simulation

Journal of Structural Geology ◽

10.1016/j.jsg.2013.04.005 ◽

2013 ◽

Vol 52 ◽

pp. 60-79 ◽

Cited By ~ 12

Author(s):

Muhammad Fachri ◽

Jan Tveranger ◽

Alvar Braathen ◽

Sylvie Schueller

Keyword(s):

Fluid Flow ◽

Deformation Band ◽

Damage Zone ◽

Gaussian Simulation ◽

Truncated Gaussian Simulation ◽

Truncated Gaussian

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Monitoring the response of volcanic CO2 emissions to changes in the Los Humeros hydrothermal system

Scientific Reports ◽

10.1038/s41598-021-97023-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Anna Jentsch ◽

Walter Duesing ◽

Egbert Jolie ◽

Martin Zimmer

Keyword(s):

Fluid Flow ◽

Hydrothermal System ◽

Damage Zone ◽

Inverse Correlation ◽

Normal Fault ◽

Atmospheric Effects ◽

Volcanic Complex ◽

Geothermal Resources ◽

Gas Emissions ◽

Soil Degassing

AbstractCarbon dioxide is the most abundant, non-condensable gas in volcanic systems, released into the atmosphere through either diffuse or advective fluid flow. The emission of substantial amounts of CO2 at Earth’s surface is not only controlled by volcanic plumes during periods of eruptive activity or fumaroles, but also by soil degassing along permeable structures in the subsurface. Monitoring of these processes is of utmost importance for volcanic hazard analyses, and is also relevant for managing geothermal resources. Fluid-bearing faults are key elements of economic value for geothermal power generation. Here, we describe for the first time how sensitively and quickly natural gas emissions react to changes within a deep hydrothermal system due to geothermal fluid reinjection. For this purpose, we deployed an automated, multi-chamber CO2 flux monitoring system within the damage zone of a deep-rooted major normal fault in the Los Humeros Volcanic Complex (LHVC) in Mexico and recorded data over a period of five months. After removing the atmospheric effects on variations in CO2 flux, we calculated correlation coefficients between residual CO2 emissions and reinjection rates, identifying an inverse correlation of ρ = − 0.51 to − 0.66. Our results indicate that gas emissions respond to changes in reinjection rates within 24 h, proving an active hydraulic communication between the hydrothermal system and Earth’s surface. This finding is a promising indication not only for geothermal reservoir monitoring but also for advanced long-term volcanic risk analysis. Response times allow for estimation of fluid migration velocities, which is a key constraint for conceptual and numerical modelling of fluid flow in fracture-dominated systems.

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The role of stress history on the flow of fluids through fractures

Mineralogical Magazine ◽

10.1180/minmag.2012.076.8.30 ◽

2012 ◽

Vol 76 (8) ◽

pp. 3165-3177 ◽

Cited By ~ 19

Author(s):

S. Sathar ◽

H. J. Reeves ◽

R. J. Cuss ◽

J. F. Harrington

Keyword(s):

Shear Stress ◽

Fluid Flow ◽

Gas Flow ◽

Shear Failure ◽

Normal Load ◽

Damage Zone ◽

Water Injection ◽

Fracture Flow ◽

Stress History ◽

Stress Regime

AbstractUnderstanding flow along fractures and faults is of importance to the performance assessment (PA) of a geological disposal facility (GDF) for radioactive waste. Flow can occur along pre-existing fractures in the host-rock or along fractures created during the construction of the GDF within the excavation damage zone (EDZ). The complex fracture network will have a range of orientations and will exist within a complex stress regime. Critical stress theory suggests that fractures close to localized shear failure are critically stressed and therefore most conductive to fluid flow. Analysis of fault geometry and stress conditions at Sellafield has revealed that no features were found to be, or even close to being, classified as critically stressed, despite some being conductive. In order to understand the underlying reasons why non-critically stressed fractures were conductive a series of laboratory experiments were performed. A bespoke angled shear rig (ASR) was built in order to study the relationship between fluid flow (water and gas) through a fracture surface as a function of normal load. Fluid flow reduced with an increase in normal load, as expected. During unloading considerable hysteresis was seen in flow and shear stress. Fracture flow was only partially recovered for water injection, whereas gas flow increased remarkably during unloading. The ratio of shear stress to normal stress seems to control the fluid flow properties during the unloading stage of the experiment demonstrating its significance in fracture flow. The exhumation of the Sellafield area during the Palaeogene–Neogene resulted in considerable stress relaxation and in fractures becoming non-critically stressed. The hysteresis in shear stress during uplift has resulted in faults remaining, or becoming, conductive. The field and laboratory observations illustrate that understanding the stress-history of a fractured rock mass is essential, and a mere understanding of the current stress regime is insufficient to estimate the flow characteristics of present-day fractures.

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Deformation band populations in fault damage zone—impact on fluid flow

Computational Geosciences ◽

10.1007/s10596-009-9148-8 ◽

2009 ◽

Vol 14 (2) ◽

pp. 231-248 ◽

Cited By ~ 11

Author(s):

Dmitry Kolyukhin ◽

Sylvie Schueller ◽

Magne S. Espedal ◽

Haakon Fossen

Keyword(s):

Fluid Flow ◽

Deformation Band ◽

Damage Zone ◽

Fault Damage Zone

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Permeability of carbonate fault rocks: a case study from Malta

Petroleum Geoscience ◽

10.1144/petgeo2019-055 ◽

2019 ◽

Vol 26 (3) ◽

pp. 418-433 ◽

Cited By ~ 2

Author(s):

Andy P. Cooke ◽

Quentin J. Fisher ◽

Emma A. H. Michie ◽

Graham Yielding

Keyword(s):

Fluid Flow ◽

Host Rock ◽

Damage Zone ◽

Fault Zones ◽

High Porosity ◽

Rock Permeability ◽

Fault Rock ◽

Fault Rocks ◽

Diagenetic Alteration ◽

Hydraulic Behaviour

The inherent heterogeneity of carbonate rocks suggests that carbonate-hosted fault zones are also likely to be heterogeneous. Coupled with a lack of host–fault petrophysical relationships, this makes the hydraulic behaviour of carbonate-hosted fault zones difficult to predict. Here we investigate the link between host rock and fault rock porosity, permeability and texture, by presenting data from series of host rock, damage zone and fault rock samples from normally faulted, shallowly buried limestones from Malta. Core plug X-ray tomography indicates that texturally heterogeneous host rocks lead to greater variability in the porosity and permeability of fault rocks. Fault rocks derived from moderate- to high-porosity (>20%) formations experience permeability reductions of up to six orders of magnitude relative to the host; >30% of these fault rocks could act as baffles or barriers to fluid flow over production timescales. Fault rocks derived from lower-porosity (<20%) algal packstones have permeabilities that are lower than their hosts by up to three orders of magnitude, which is unlikely to impact fluid flow on production timescales. The variability of fault rock permeability is controlled by a number of factors, including the initial host rock texture and porosity, the magnitude of strain localization, and the extent of post-deformation diagenetic alteration. Fault displacement has no obvious control over fault rock permeability. The results enable better predictions of fault rock permeability in similar lithotypes and tectonic regimes. This may enable predictions of across-fault fluid flow potential when combined with data on fault zone architecture.

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