Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland

Implications for Genesis and Classification

C. M. Rice, D. F. Mark, D. Selby, J. E. Neilson, B. Davidheiser-Kroll

Research output: Contribution to journalArticle

7 Citations (Scopus)
7 Downloads (Pure)

Abstract

The Caledonian orogenic belt of northern Britain hosts some significant quartz vein-hosted gold deposits. However, as in orogenic belts worldwide, the relationship between gold mineralization and regional tectonics, magmatism, and metamorphism is a matter of debate. This is primarily due to the absence of precise temporal constraints for the mineralization. Here we report high-precision 40Ar/39Ar and Re-Os ages for the largest known gold deposit at Curraghinalt (2.7 Moz) in Northern Ireland and use these ages to constrain the regional geologic setting of the gold mineralization and establish a genetic model.

The gold resource is contained in a suite of quartz sulfide veins hosted by Neoproterozoic (Dalradian) metasediments, which have been thrust over an Ordovician island arc (Tyrone Igneous Complex). Previous studies recognized two generations of gold sulfide mineralization and we have identified a third in microshears that cut the veins. In the absence of precise geochronological data, mineralization ages from Ordovician to Carboniferous have been proposed.

We have dated muscovite (40Ar/39Ar) in quartz vein-hosted clasts of Dalradian wall rock to 459.3 ± 3.4 Ma (all 40Ar/39Ar and Re-Os ages herein are reported at the 2σ confidence level including all sources of uncertainty), an age that we interpret as representing the regional cooling path and which provides a maximum age constraint for all gold mineralization. This is consistent with the quartz veins postdating the end of main-stage deformation in the Grampian event of the Caledonian orogeny (ca. 465 Ma).

Molybdenite (Re-Os) and sericite (40Ar/39Ar) from the newly identified gold-bearing microshears (third generation of gold mineralization) yield indistinguishable Re-Os models and 40Ar/39Ar ages, with a combined age of 455.8 ± 3.0 Ma. The radioisotope ages and field evidence temporally constrain gold mineralization at Curraghinalt to the lower Late Ordovician.

Data show that the gold mineralization was emplaced during the Grampian event of the Caledonian orogeny. The ca. 10 Ma maximum possible mineralization interval (462.7–452.8 Ma) for all three episodes of gold emplacement is postpeak metamorphism and main deformation, coinciding with a period of rapid uplift and extensional tectonics following orogenic collapse. While previous studies have suggested the involvement of magmatic fluids in the deposition of the primary gold resource, the absence of magmatism throughout most of the mineralization interval and the nature of the geologic setting suggest that crustal orogenic fluids should also be considered. Overall Curraghinalt displays most of the characteristics of orogenic gold deposits but also some important differences, which may be explained by the geologic setting.

The timing of mineralization at Curraghinalt broadly coincides with the shift from compressional to extensional tectonics. The extensional regime, rapid uplift, and a crustal profile comprising metasediments overlying a still hot island arc were ideal for creating large and long-lasting hydrothermal systems deriving heat, metals, and some of the fluids from the underlying arc.
Original languageEnglish
Pages (from-to)127-150
Number of pages24
JournalEconomic Geology
Volume111
Issue number1
Early online date8 Jan 2016
DOIs
Publication statusPublished - Jan 2016

Fingerprint

Northern Ireland
Quartz
quartz vein
veins
Gold
quartz
gold
mineralization
Gold deposits
Tectonics
Caledonian orogeny
Sulfides
Ordovician
tectonics
Dalradian
island arcs
Fluids
deposits
extensional tectonics
metasediment

Cite this

Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland : Implications for Genesis and Classification. / Rice, C. M.; Mark, D. F.; Selby, D.; Neilson, J. E.; Davidheiser-Kroll, B.

In: Economic Geology, Vol. 111, No. 1, 01.2016, p. 127-150.

Research output: Contribution to journalArticle

@article{5bc970da875e41759e4db6eb76b9e6d9,
title = "Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland: Implications for Genesis and Classification",
abstract = "The Caledonian orogenic belt of northern Britain hosts some significant quartz vein-hosted gold deposits. However, as in orogenic belts worldwide, the relationship between gold mineralization and regional tectonics, magmatism, and metamorphism is a matter of debate. This is primarily due to the absence of precise temporal constraints for the mineralization. Here we report high-precision 40Ar/39Ar and Re-Os ages for the largest known gold deposit at Curraghinalt (2.7 Moz) in Northern Ireland and use these ages to constrain the regional geologic setting of the gold mineralization and establish a genetic model.The gold resource is contained in a suite of quartz sulfide veins hosted by Neoproterozoic (Dalradian) metasediments, which have been thrust over an Ordovician island arc (Tyrone Igneous Complex). Previous studies recognized two generations of gold sulfide mineralization and we have identified a third in microshears that cut the veins. In the absence of precise geochronological data, mineralization ages from Ordovician to Carboniferous have been proposed.We have dated muscovite (40Ar/39Ar) in quartz vein-hosted clasts of Dalradian wall rock to 459.3 ± 3.4 Ma (all 40Ar/39Ar and Re-Os ages herein are reported at the 2σ confidence level including all sources of uncertainty), an age that we interpret as representing the regional cooling path and which provides a maximum age constraint for all gold mineralization. This is consistent with the quartz veins postdating the end of main-stage deformation in the Grampian event of the Caledonian orogeny (ca. 465 Ma).Molybdenite (Re-Os) and sericite (40Ar/39Ar) from the newly identified gold-bearing microshears (third generation of gold mineralization) yield indistinguishable Re-Os models and 40Ar/39Ar ages, with a combined age of 455.8 ± 3.0 Ma. The radioisotope ages and field evidence temporally constrain gold mineralization at Curraghinalt to the lower Late Ordovician.Data show that the gold mineralization was emplaced during the Grampian event of the Caledonian orogeny. The ca. 10 Ma maximum possible mineralization interval (462.7–452.8 Ma) for all three episodes of gold emplacement is postpeak metamorphism and main deformation, coinciding with a period of rapid uplift and extensional tectonics following orogenic collapse. While previous studies have suggested the involvement of magmatic fluids in the deposition of the primary gold resource, the absence of magmatism throughout most of the mineralization interval and the nature of the geologic setting suggest that crustal orogenic fluids should also be considered. Overall Curraghinalt displays most of the characteristics of orogenic gold deposits but also some important differences, which may be explained by the geologic setting.The timing of mineralization at Curraghinalt broadly coincides with the shift from compressional to extensional tectonics. The extensional regime, rapid uplift, and a crustal profile comprising metasediments overlying a still hot island arc were ideal for creating large and long-lasting hydrothermal systems deriving heat, metals, and some of the fluids from the underlying arc.",
author = "Rice, {C. M.} and Mark, {D. F.} and D. Selby and Neilson, {J. E.} and B. Davidheiser-Kroll",
note = "Acknowledgments We are grateful to Dalradian Gold Ltd. for providing the sections for petrographic analysis, geochemical data, and general support. We would also like to thank the following: John Still, Alison Sandison, and Jenny Johnston of the School of Geosciences, University of Aberdeen, for assistance with the SEM studies (JS) and with preparing figures (AS and JJ); NERC for ongoing funding of the Argon Isotope facility at SUERC; Jim Imlach and Ross Dymock at SUERC for technical assistance; and Martin Lee at the School of Geographical and Earth Sciences at the University of Glasgow for use of the SEM/CL equipment. The paper has benefitted significantly from comments by the official reviewers and unofficial reviews by Garth Earls, Jamie Wilkinson, Mark Cooper, and Adrian Boyce, and detailed conversations with Ian Alsop (structural geology of the Sperrins) and Nyree Hill and Gawen Jenkin (gold mineralization in the Caledonides). The authors are entirely responsible for the conclusions expressed.",
year = "2016",
month = "1",
doi = "10.2113/econgeo.111.1.127",
language = "English",
volume = "111",
pages = "127--150",
journal = "Economic Geology",
issn = "0361-0128",
publisher = "Society of Economic Geologists, Inc",
number = "1",

}

TY - JOUR

T1 - Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland

T2 - Implications for Genesis and Classification

AU - Rice, C. M.

AU - Mark, D. F.

AU - Selby, D.

AU - Neilson, J. E.

AU - Davidheiser-Kroll, B.

N1 - Acknowledgments We are grateful to Dalradian Gold Ltd. for providing the sections for petrographic analysis, geochemical data, and general support. We would also like to thank the following: John Still, Alison Sandison, and Jenny Johnston of the School of Geosciences, University of Aberdeen, for assistance with the SEM studies (JS) and with preparing figures (AS and JJ); NERC for ongoing funding of the Argon Isotope facility at SUERC; Jim Imlach and Ross Dymock at SUERC for technical assistance; and Martin Lee at the School of Geographical and Earth Sciences at the University of Glasgow for use of the SEM/CL equipment. The paper has benefitted significantly from comments by the official reviewers and unofficial reviews by Garth Earls, Jamie Wilkinson, Mark Cooper, and Adrian Boyce, and detailed conversations with Ian Alsop (structural geology of the Sperrins) and Nyree Hill and Gawen Jenkin (gold mineralization in the Caledonides). The authors are entirely responsible for the conclusions expressed.

PY - 2016/1

Y1 - 2016/1

N2 - The Caledonian orogenic belt of northern Britain hosts some significant quartz vein-hosted gold deposits. However, as in orogenic belts worldwide, the relationship between gold mineralization and regional tectonics, magmatism, and metamorphism is a matter of debate. This is primarily due to the absence of precise temporal constraints for the mineralization. Here we report high-precision 40Ar/39Ar and Re-Os ages for the largest known gold deposit at Curraghinalt (2.7 Moz) in Northern Ireland and use these ages to constrain the regional geologic setting of the gold mineralization and establish a genetic model.The gold resource is contained in a suite of quartz sulfide veins hosted by Neoproterozoic (Dalradian) metasediments, which have been thrust over an Ordovician island arc (Tyrone Igneous Complex). Previous studies recognized two generations of gold sulfide mineralization and we have identified a third in microshears that cut the veins. In the absence of precise geochronological data, mineralization ages from Ordovician to Carboniferous have been proposed.We have dated muscovite (40Ar/39Ar) in quartz vein-hosted clasts of Dalradian wall rock to 459.3 ± 3.4 Ma (all 40Ar/39Ar and Re-Os ages herein are reported at the 2σ confidence level including all sources of uncertainty), an age that we interpret as representing the regional cooling path and which provides a maximum age constraint for all gold mineralization. This is consistent with the quartz veins postdating the end of main-stage deformation in the Grampian event of the Caledonian orogeny (ca. 465 Ma).Molybdenite (Re-Os) and sericite (40Ar/39Ar) from the newly identified gold-bearing microshears (third generation of gold mineralization) yield indistinguishable Re-Os models and 40Ar/39Ar ages, with a combined age of 455.8 ± 3.0 Ma. The radioisotope ages and field evidence temporally constrain gold mineralization at Curraghinalt to the lower Late Ordovician.Data show that the gold mineralization was emplaced during the Grampian event of the Caledonian orogeny. The ca. 10 Ma maximum possible mineralization interval (462.7–452.8 Ma) for all three episodes of gold emplacement is postpeak metamorphism and main deformation, coinciding with a period of rapid uplift and extensional tectonics following orogenic collapse. While previous studies have suggested the involvement of magmatic fluids in the deposition of the primary gold resource, the absence of magmatism throughout most of the mineralization interval and the nature of the geologic setting suggest that crustal orogenic fluids should also be considered. Overall Curraghinalt displays most of the characteristics of orogenic gold deposits but also some important differences, which may be explained by the geologic setting.The timing of mineralization at Curraghinalt broadly coincides with the shift from compressional to extensional tectonics. The extensional regime, rapid uplift, and a crustal profile comprising metasediments overlying a still hot island arc were ideal for creating large and long-lasting hydrothermal systems deriving heat, metals, and some of the fluids from the underlying arc.

AB - The Caledonian orogenic belt of northern Britain hosts some significant quartz vein-hosted gold deposits. However, as in orogenic belts worldwide, the relationship between gold mineralization and regional tectonics, magmatism, and metamorphism is a matter of debate. This is primarily due to the absence of precise temporal constraints for the mineralization. Here we report high-precision 40Ar/39Ar and Re-Os ages for the largest known gold deposit at Curraghinalt (2.7 Moz) in Northern Ireland and use these ages to constrain the regional geologic setting of the gold mineralization and establish a genetic model.The gold resource is contained in a suite of quartz sulfide veins hosted by Neoproterozoic (Dalradian) metasediments, which have been thrust over an Ordovician island arc (Tyrone Igneous Complex). Previous studies recognized two generations of gold sulfide mineralization and we have identified a third in microshears that cut the veins. In the absence of precise geochronological data, mineralization ages from Ordovician to Carboniferous have been proposed.We have dated muscovite (40Ar/39Ar) in quartz vein-hosted clasts of Dalradian wall rock to 459.3 ± 3.4 Ma (all 40Ar/39Ar and Re-Os ages herein are reported at the 2σ confidence level including all sources of uncertainty), an age that we interpret as representing the regional cooling path and which provides a maximum age constraint for all gold mineralization. This is consistent with the quartz veins postdating the end of main-stage deformation in the Grampian event of the Caledonian orogeny (ca. 465 Ma).Molybdenite (Re-Os) and sericite (40Ar/39Ar) from the newly identified gold-bearing microshears (third generation of gold mineralization) yield indistinguishable Re-Os models and 40Ar/39Ar ages, with a combined age of 455.8 ± 3.0 Ma. The radioisotope ages and field evidence temporally constrain gold mineralization at Curraghinalt to the lower Late Ordovician.Data show that the gold mineralization was emplaced during the Grampian event of the Caledonian orogeny. The ca. 10 Ma maximum possible mineralization interval (462.7–452.8 Ma) for all three episodes of gold emplacement is postpeak metamorphism and main deformation, coinciding with a period of rapid uplift and extensional tectonics following orogenic collapse. While previous studies have suggested the involvement of magmatic fluids in the deposition of the primary gold resource, the absence of magmatism throughout most of the mineralization interval and the nature of the geologic setting suggest that crustal orogenic fluids should also be considered. Overall Curraghinalt displays most of the characteristics of orogenic gold deposits but also some important differences, which may be explained by the geologic setting.The timing of mineralization at Curraghinalt broadly coincides with the shift from compressional to extensional tectonics. The extensional regime, rapid uplift, and a crustal profile comprising metasediments overlying a still hot island arc were ideal for creating large and long-lasting hydrothermal systems deriving heat, metals, and some of the fluids from the underlying arc.

U2 - 10.2113/econgeo.111.1.127

DO - 10.2113/econgeo.111.1.127

M3 - Article

VL - 111

SP - 127

EP - 150

JO - Economic Geology

JF - Economic Geology

SN - 0361-0128

IS - 1

ER -