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Petrochemistry and hydrothermal alteration within the Tyrone Igneous Complex, Northern Ireland: implications for VMS mineralization in the British and Irish Caledonides

Petrochemistry and hydrothermal alteration within the Tyrone Igneous Complex, Northern Ireland: implications for VMS mineralization in the British and Irish Caledonides
Petrochemistry and hydrothermal alteration within the Tyrone Igneous Complex, Northern Ireland: implications for VMS mineralization in the British and Irish Caledonides


Although volcanogenic massive sulfide (VMS) deposits can form within a wide variety of rift-related tectonic environments, most are preserved within suprasubduction affinity crust related to ocean closure. In stark contrast to the VMS-rich Appalachian sector of the Grampian-Taconic orogeny, VMS mineralization is rare in the peri-Laurentian British and Irish Caledonides. Economic peri-Gondwanan affinity deposits are limited to Avoca and Parys Mountain. The Tyrone Igneous Complex of Northern Ireland represents a ca. 484–464 Ma peri-Laurentian affinity arc–ophiolite complex and a possible broad correlative of the Buchans-Robert’s Arm belt of Newfoundland, host to some of the most metal-rich VMS deposits globally. Stratigraphic horizons prospective for VMS mineralization in the Tyrone Igneous Complex are associated with rift-related magmatism, hydrothermal alteration, synvolcanic faults, and high-level subvolcanic intrusions (gabbro, diorite, and/or tonalite). Locally intense hydrothermal alteration is characterized by Na-depletion, elevated SiO2, MgO, Ba/Sr, Bi, Sb, chlorite–carbonate–pyrite alteration index (CCPI) and Hashimoto alteration index (AI) values. Rift-related mafic lavas typically occur in the hanging wall sequences to base and precious metal mineralization, closely associated with ironstones and/or argillaceous sedimentary rocks representing low temperature hydrothermal venting and volcanic quiescence. In the ca. 475 Ma pre-collisional, calc-alkaline lower Tyrone Volcanic Group rift-related magmatism is characterized by abundant non-arc type Fe-Ti-rich eMORB, island-arc tholeiite, and low-Zr tholeiitic rhyolite breccias. These petrochemical characteristics are typical of units associated with VMS mineralization in bimodal mafic, primitive post-Archean arc terranes. Following arc-accretion at ca. 470 Ma, late rifting in the ensialic upper Tyrone Volcanic Group is dominated by OIB-like, subalkaline to alkali basalt and A-type, high-Zr rhyolites. These units are petrochemically favorable for Kuroko-type VMS mineralization in bimodal-felsic evolved arc terranes. The scarcity of discovered peri-Laurentian VMS mineralization in the British and Irish Caledonides is due to a combination of minimal exploration, poor-preservation of upper ophiolite sequences, and limited rifting in the Lough Nafooey arc of western Ireland. The geological and geochemical characteristics of the Tyrone Volcanic Group of Northern Ireland and peri-Gondwanan affinity arc/backarc sequences of Ireland and northwest Wales represent the most prospective sequences in the British and Irish Caledonides for VMS mineralization.
Volcanogenic massive sulfide, Volcanic-hosted massive sulfide, VHMS, Element mobility, Lithogeochemistry
0026-4598
575-593
Hollis, Steven P.
3dd0519f-bc6c-49c0-9cc2-9a8c5cac9aa1
Roberts, Stephen
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Earls, Garth
2cbfc172-8668-4180-8950-e2fbd27df51e
Herrington, Richard
6466a9c1-3e23-40a4-a1e5-a5ce15f5a43d
Cooper, Mark R.
68d782fa-c882-41e0-a21e-b1a88bf34f99
Piercey, Stephen J.
f7f07830-ee80-4158-8438-799e38795f78
Archibald, Sandy M.
f8079c8d-15a4-44ad-b951-48300d4c24e1
Moloney, Martin
de45ad59-6e0e-43a1-9cf2-5fb9104b59b7
Hollis, Steven P.
3dd0519f-bc6c-49c0-9cc2-9a8c5cac9aa1
Roberts, Stephen
f095c7ab-a37b-4064-8a41-ae4820832856
Earls, Garth
2cbfc172-8668-4180-8950-e2fbd27df51e
Herrington, Richard
6466a9c1-3e23-40a4-a1e5-a5ce15f5a43d
Cooper, Mark R.
68d782fa-c882-41e0-a21e-b1a88bf34f99
Piercey, Stephen J.
f7f07830-ee80-4158-8438-799e38795f78
Archibald, Sandy M.
f8079c8d-15a4-44ad-b951-48300d4c24e1
Moloney, Martin
de45ad59-6e0e-43a1-9cf2-5fb9104b59b7

Hollis, Steven P., Roberts, Stephen, Earls, Garth, Herrington, Richard, Cooper, Mark R., Piercey, Stephen J., Archibald, Sandy M. and Moloney, Martin (2014) Petrochemistry and hydrothermal alteration within the Tyrone Igneous Complex, Northern Ireland: implications for VMS mineralization in the British and Irish Caledonides. Mineralium Deposita, 49 (5), 575-593. (doi:10.1007/s00126-013-0508-x).

Record type: Article

Abstract



Although volcanogenic massive sulfide (VMS) deposits can form within a wide variety of rift-related tectonic environments, most are preserved within suprasubduction affinity crust related to ocean closure. In stark contrast to the VMS-rich Appalachian sector of the Grampian-Taconic orogeny, VMS mineralization is rare in the peri-Laurentian British and Irish Caledonides. Economic peri-Gondwanan affinity deposits are limited to Avoca and Parys Mountain. The Tyrone Igneous Complex of Northern Ireland represents a ca. 484–464 Ma peri-Laurentian affinity arc–ophiolite complex and a possible broad correlative of the Buchans-Robert’s Arm belt of Newfoundland, host to some of the most metal-rich VMS deposits globally. Stratigraphic horizons prospective for VMS mineralization in the Tyrone Igneous Complex are associated with rift-related magmatism, hydrothermal alteration, synvolcanic faults, and high-level subvolcanic intrusions (gabbro, diorite, and/or tonalite). Locally intense hydrothermal alteration is characterized by Na-depletion, elevated SiO2, MgO, Ba/Sr, Bi, Sb, chlorite–carbonate–pyrite alteration index (CCPI) and Hashimoto alteration index (AI) values. Rift-related mafic lavas typically occur in the hanging wall sequences to base and precious metal mineralization, closely associated with ironstones and/or argillaceous sedimentary rocks representing low temperature hydrothermal venting and volcanic quiescence. In the ca. 475 Ma pre-collisional, calc-alkaline lower Tyrone Volcanic Group rift-related magmatism is characterized by abundant non-arc type Fe-Ti-rich eMORB, island-arc tholeiite, and low-Zr tholeiitic rhyolite breccias. These petrochemical characteristics are typical of units associated with VMS mineralization in bimodal mafic, primitive post-Archean arc terranes. Following arc-accretion at ca. 470 Ma, late rifting in the ensialic upper Tyrone Volcanic Group is dominated by OIB-like, subalkaline to alkali basalt and A-type, high-Zr rhyolites. These units are petrochemically favorable for Kuroko-type VMS mineralization in bimodal-felsic evolved arc terranes. The scarcity of discovered peri-Laurentian VMS mineralization in the British and Irish Caledonides is due to a combination of minimal exploration, poor-preservation of upper ophiolite sequences, and limited rifting in the Lough Nafooey arc of western Ireland. The geological and geochemical characteristics of the Tyrone Volcanic Group of Northern Ireland and peri-Gondwanan affinity arc/backarc sequences of Ireland and northwest Wales represent the most prospective sequences in the British and Irish Caledonides for VMS mineralization.

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Published date: June 2014
Keywords: Volcanogenic massive sulfide, Volcanic-hosted massive sulfide, VHMS, Element mobility, Lithogeochemistry
Organisations: Geochemistry

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Local EPrints ID: 366082
URI: http://eprints.soton.ac.uk/id/eprint/366082
ISSN: 0026-4598
PURE UUID: 903533fd-da07-4f0f-a54b-a72565481525
ORCID for Stephen Roberts: ORCID iD orcid.org/0000-0003-4755-6703

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Date deposited: 20 Jun 2014 12:17
Last modified: 15 Mar 2024 02:39

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Author: Steven P. Hollis
Author: Stephen Roberts ORCID iD
Author: Garth Earls
Author: Richard Herrington
Author: Mark R. Cooper
Author: Stephen J. Piercey
Author: Sandy M. Archibald
Author: Martin Moloney

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