Structure of Lower Carboniferous basins of NW Ireland, and its implications for structural inheritance and Cenozoic faulting

Worthington, Robert P.; Walsh, John J.

doi:10.1016/j.jsg.2011.05.001

Cited by 32 publications

(27 citation statements)

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“…11 for a visual explanation). The Carboniferous normal faults have been interpreted to continue down into the basement rocks, often reactivating or being localized along preexisting structures (e.g., Johnston et al, 1996;Johnston, 1999;Worthington and Walsh, 2011;Bonson et al, 2012). At Lisheen minor mineralization occurs in the Lisduff Oolite Member wherever it was juxtaposed with the Waulsortian at the time of mineralization (Shearley et al, 1996;Redmond, 1997;Hitzman et al, 2002;Fusciardi et al, 2004;Kyne et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Controls on Metal Distributions at the Lisheen and Silvermines Deposits: Insights into Fluid Flow Pathways in Irish-Type Zn-Pb Deposits

et al. 2018

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The world-class Irish Zn-Pb(-Ag) deposits occur within one of the world's major metallogenic provinces. While it has been well documented that these orebodies are structurally controlled, exactly how fluids migrated from source to trap is still poorly understood. Using 3-D modeling techniques, the current study investigates metal distribution patterns at the Silvermines and Lisheen deposits to gain insights into fluid pathways and structural controls on mineralization. Distinct points along segmented normal faults are identified as the feeders to individual orebodies, allowing hot, hydrothermal, metal-bearing fluids to enter host rocks and form orebodies. These points are characterized by highly localized and elevated Ag, Cu, Co, Ni, and As concentrations as well as low Zn/Pb ratios, which increase away from the feeders. Metal distributions are initially controlled by major and minor normal faults and subsequently affected by later oblique-slip dextral and strike-slip faults. High-tonnage areas without typical feeder signals are interpreted to be structural trap sites, which are distal to fault-controlled feeder points. This study highlights both the importance of a well-connected plumbing system for metal-bearing fluids to reach their basinal traps and the control that an evolving structural framework has on spatial distribution of metals.Koen Torremans is a structural geologist who specializes in mineral deposits in sedimentary basins. He is currently a Marie Skłodowska-Curie postdoctoral fellow based at iCRAG, the Irish Centre for Research in Applied Geosciences in University College Dublin, Ireland. Koen received his B.Sc., M.Sc., and Ph.D. (2016) degrees from KU Leuven University in Belgium. He has worked extensively on base metal deposits in the Central African Copperbelt and the Irish ore field, applying a wide variety of techniques to elucidate ore deposit formation, fluid flow, and structural controls. This includes structural analysis, basin analysis, geochemistry, and geologic and numerical modeling techniques.

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Section: Discussionmentioning

confidence: 99%

Controls on Metal Distributions at the Lisheen and Silvermines Deposits: Insights into Fluid Flow Pathways in Irish-Type Zn-Pb Deposits

et al. 2018

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“…Associated with this extension was the development of E-W-to NE-SW-trending normal faults, including those at Lisheen and Silvermines (Figs. 3,4), the localization and evolution of which is believed to have been controlled by the geometries of reactivated Caledonian basement structures (Coller, 1984;Brown and Williams, 1985;Phillips and Sevastopulo, 1986;Johnston et al, 1996;Johnston, 1999;O'Reilly et al, 1999;Worthington and Walsh, 2011;Davies et al, 2012).…”

Section: Structural Evolution Of the Irish Ore Fieldmentioning

confidence: 99%

“…Within the Irish context the most widely accepted explanation for this type of fault complexity is that underlying pre-Carboniferous basement structures, which are generally ENE-oriented, control the formation of the main faults. Later oblique extension (closer to N-S) on the controlling basement faults caused vertical fault propagation and/or nucleation, which then led to segmentation within the Carboniferous, often forming left-stepping fault arrays (Johnston et al, 1996;Worthington and Walsh, 2011;Bonson et al, 2012). In this study we establish the 3-D geometry and kinematics of fault systems associated with Irish mineral deposits and reconcile their structural evolution with existing models for segmented normal fault arrays.…”

Section: Introductionmentioning

confidence: 99%

3-D Modeling of the Lisheen and Silvermines Deposits, County Tipperary, Ireland:Insights into Structural Controls on the Formation of Irish Zn-Pb Deposits

et al. 2019

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Faults are important structures in the formation of many mineral deposits, often acting as conduits for oreforming fluids and sometimes providing, or generating, the bounding structures to associated mineralizing sites. Using 3-D analysis and modeling of the Lisheen and Silvermines deposits within the Irish ore field, we investigate the geometry of normal fault systems and their implications on the origin and nature of associated deposits. These Irish-type deposits are carbonate hosted and developed within the hanging walls of normal faults arising from an Early Carboniferous episode of north-south rifting, with relatively limited amounts of later deformation. Structural analysis of high-quality mine datasets indicates that fault segmentation is ubiquitous with left-stepping segments arising from north-south stretching developed above generally ENE-NE-trending fault arrays, which are subparallel to older Caledonian penetrative fabrics and structure within underlying Silurian and Ordovician rocks. Fault segments occur on different scales and have a profound impact on structural evolution, with larger scale segments and intervening relay ramps defining distinct orebodies within deposits and smaller scale segments and relays potentially providing paths for upfault fluid flow. The difference in behavior is attributed to the integrity of associated relay ramps where intact ramps represent orebody-bounding structures, and smaller breached ramps provide enhanced associated hydraulic properties and act as vertical conduits. Hanging-wall deformation along the rheological boundary between host-rock limestones and underlying shales has an important control on the localization of earlier dolomitization and/or brecciation and later mineralization adjacent to this contact, and on the migration pathways for basinal brines and mineralizing fluids.Roisin Kyne is a structural geologist specializing in the formation of sedimentary rock-hosted base metal deposits. After receiving her HB.Sc. degree from Lakehead University (2009), Roisin completed a Ph.D. at CODES, University of Tasmania (2014), followed by a post-doc at iCRAG, University College Dublin (2018). Her work focused on structural controls of Zn-Pb-Cu deposits in Cobar, NSW, and the Irish ore field and implications for formation, fluid flow, and mineralization. In her current role as project geologist at Teck Resources, Roisin is applying her knowledge of 3-D modeling, basin analysis, and deposit formation to explore for Zn-Pb deposits in North America.

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“…Most of this poorly-productive bedrock is 76 composed of various grades of metamorphic (basement) rocks; from low-grade metasediments to 77 high-grade gneiss-migmatites and granitoids. Groundwater in these rocks, despite their overall low 78 productivity, is nonetheless crucial for maintaining river base flow during dry periods and supporting 79 aquatic ecosystems and small-scale rural water supply (DCCAE 2017 Alpine, strike-slip tectonic regime, is reflected by reactivation of NE-SW fracture orientations and 116 further creation of a general NW-SE trend (Worthington & Walsh 2011;Cooper et al 2012). 117…”

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confidence: 99%

“…The dominant fracture set may be attributed to the strike-slip 305 regional fracturing associated with Alpine compression during the Palaeocene, whereas the second 306 set may be attributed to the compressive fabric of the Neo-Proterozoic to late Carboniferous 307 orogenies (Grampian, Caledonian and Variscan), which also characterise the regional-scale 308 lineaments ( Fig. 1) and Lower Carboniferous normal faults (Worthington & Walsh 2011), reactivated 309…”

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Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys: implications for groundwater flow paths and the distribution of residence times

Comte

Ofterdinger

Legchenko

et al. 2018

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General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights.Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk. Among them, the Griffith Poorly-productive Aquifers Project (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), on which this work is 84 based, aimed to improve the understanding of groundwater flow regimes in fractured rock aquifers 85 and the contribution of groundwater to catchment water balance (Comte et al. 2012; Cassidy et al. 86 2014; et al. (2014). Samples were heated from 200-880°C to 179 determine sequential dehydroxylation water loss from the clay mineral fraction. Mineral proportions 180 (volume %) were converted to weight %. Using the method of Revil et al. (1998), the total cation 181 exchange capacity (CEC) of the different geological units (transition, shallow, deep bedrock) at each 182 of the three sites (GO1-3) were calculated from (i) the relative mass proportion of clay minerals, (ii) 183 their individual CEC, obtained from literature (Swineford 1955;Wiklander 1964; 184 Thomas 1976;Ridge 1983;Revil et al. 1998; Crain 2000;Gillespie et al. 2001;Ellis & Singer 2007; 185 Henn et al. 2007) and (iii) the total clay content derived from natural gamma ray logs from each 186 borehole. 187Aquifer pumping and recovery tests were implemented in every borehole to provide local values 188 of equivalent hydraulic conductivity and storativity for each borehole. The hydraulic testing 189 methodology is described in details in Comte et al. (2012). Pumping test were conducted at a 190 constant rate (2 to 30 L/min depending on the borehole) and both pumping and recovery curves 191 were jointly interpreted using AQTESOLV Pro v4. results) and produced a stronger anisotropy, the ratio was set to 0.1, whereas at shallow depths, 211where other fracture sets and pronounced weathering contribute to flow, particularly in the broken 212 bedrock, anisotropy was expected to weaken and was therefore set to 0.5. The anisotropy angle was 213 derived as an average of the individual angles of the dominant fracture sets for each bedrock 214 conceptual unit (broken, figured, massive). 215 216 Geophysical investigations 218Electrical resistivity tomography and petrophysical models for porosity estimation 219 220A geophysical survey using electrical resistivity tomography ERT was carried out to provide a 221 catchment-scale conceptual understanding of the bedrock heterogeneity and its hydrogeological 222 significance. ERT was a...

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Structure of Lower Carboniferous basins of NW Ireland, and its implications for structural inheritance and Cenozoic faulting

Cited by 32 publications

References 32 publications

Controls on Metal Distributions at the Lisheen and Silvermines Deposits: Insights into Fluid Flow Pathways in Irish-Type Zn-Pb Deposits

Controls on Metal Distributions at the Lisheen and Silvermines Deposits: Insights into Fluid Flow Pathways in Irish-Type Zn-Pb Deposits

3-D Modeling of the Lisheen and Silvermines Deposits, County Tipperary, Ireland:Insights into Structural Controls on the Formation of Irish Zn-Pb Deposits

Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys: implications for groundwater flow paths and the distribution of residence times

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