Regional fluid flow and gold mineralization in the Dalradian of the Sperrin Mountains, Northern Ireland

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doi: 10.2113/gsecongeo.95.7.1389
Authors:Parnell, J.; Earls, G.; Wilkinson, J. J.; Hutton, D. H.; Boyce, A. J.; Fallick, A. E.; Ellam, R. M.; Gleeson, S. A.; Moles, N. R.; Carey, P. F.; Legg, I.
Author Affiliations:Primary:
University of Aberdeen, Department of Geology and Petroleum Geology, Aberdeen, United Kingdom
CSA Group, Dublin, Ireland
Imperial College, United Kingdom
University of Birmingham, United Kingdom
Scottish Universities Research and Reactor Centre, United Kingdom
Queen's University of Belfast, United Kingdom
Geological Survey of Northern Ireland, United Kingdom
Volume Title:Economic Geology and the Bulletin of the Society of Economic Geologists
Source:Economic Geology and the Bulletin of the Society of Economic Geologists, 95(7), p.1389-1416. Publisher: Economic Geology Publishing Company, Lancaster, PA, United States. ISSN: 0361-0128
Publication Date:2000
Note:In English. 74 refs.; illus., incl. sect., 5 tables, geol. sketch map
Summary:Gold vein mineralization occurs in the metamorphosed and deformed Dalradian (Neoproterozoic) rocks of the Sperrin Mts, N Ireland. Two structures exerted a control on the location of the mineralization; the N-S Omagh lineament and the NNW-ESE Curraghinalt lateral ramp in the footwall of the NE-SW Omagh thrust. These are Caledonian structures resulting from the thrusting of Dalradian rocks over a possibly still active Ordovician arc. CL microscopy distinguishes four phases of vein quartz in the Curraghinalt gold prospect. Fluid inclusion studies and stable isotope geochemistry have defined the probable fluids responsible for the precipitation of each quartz phase and associated sulphide and precious metal mineralization. The initial phase (Q1) appears to have been associated with the main Caledonian metamorphic event (∼ 470 m.y.) and is non-auriferous. The second phase (Q2) forms an extensive cement to brecciated early quartz and is believed to have involved a fluid (∼ 15 wt.% CO2, 10 wt.% NaCl + KCl equiv.), with a significant magmatic component of 470-400 m.y., which underwent phase separation and dilution with a cooler formation water. This process resulted in precipitation of the main phase of Au mineralization characterized by an assemblage of electrum, pyrite, arsenopyrite, chalcopyrite, tennantite-tetrahedrite and various tellurides. Brine flow is localized by the Omagh thrust, indicating the long-lived role of this structure in controlling regional fluid migration. [G.L.B.]
Sections:Economic minerals and ore deposits
Subsections:Metallic deposits: regional
Subjects:Dalradian; Faults; Gold ores; Hydrothermal alteration; Metal ores; Metasomatism; Mineral deposits, genesis; Mineralization; Neoproterozoic; Precambrian; Proterozoic; Structural controls; Thrust faults; Upper Precambrian; Veins; Caledonides; Europe; Northern Ireland; United Kingdom; Western Europe; Cavanacaw Northern Ireland; Curraghinalt Northern Ireland; Golan Burn Northern Ireland; Omagh Northern Ireland; Sperrin Mountains
Coordinates:N543000 N550000 W0070000 W0074500
Abstract Numbers:03M/3698
Record ID:2001007883
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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