Now showing 1 - 10 of 16
No Thumbnail Available
Publication

Age and geochemistry of the Charlestown Group, Ireland: implications for the Grampian orogeny, its mineral potential and the Ordovician timescale

2016-12-24, Herrington, Richard J., Hollis, Steven P., Cooper, Mark, et al.

Accurately reconstructing the growth of continental margins during episodes of ocean closure has important implications for understanding the formation, preservation and location of mineral deposits in ancient orogens.

No Thumbnail Available
Publication

Controls on the formation of a large Zn-Pb Irish-type deposit: evidence from the Navan halos

2017-05-14, Marks, Freya R., Menuge, Julian, Boyce, Adrian, Hollis, Steven P.

The mainly epigenetic Navan orebody is hosted by the Lower Carboniferous shallow water carbonate Pale Beds. Subordinate mineralization, hosted by submarine debris flows and the lowermost overlying basinal rocks, formed during seafloor exhalation and reaches ore grade in the Conglomerate Group Ore.

No Thumbnail Available
Publication

Preliminary paragenetic studies of the high grade Island Pod Zn-Pb orebody, Lisheen

2017-03-05, Doran, Aileen, Menuge, Julian, Hollis, Steven P., Güven, John

Irish-type deposits are a series of Zn-Pb orebodies which formed from the carbonate replacement of Lower Carboniferous limestone, triggered primarily by fluid mixing. This project aims to use isotopic (Zn-Cu-S and clumped O-C) techniques to identify geochemical halos and increase our understanding of hydrothermal fluid processes in these deposits.

No Thumbnail Available
Publication

A comparison between clumped C-O and fluid inclusion temperatures for carbonates associated with Irish-type Zn-Pb orebodies

2017-08-12, Hollis, Steven P., Doran, Aileen, Menuge, Julian, Güven, John, et al.

Ireland hosts the greatest concentration of discovered zinc per square kilometre on Earth, with past and current production from five Irish-type carbonate-hosted deposits, including the giant Navan deposit. Clumped C-O isotope analysis of carbonate phases offers a powerful new technique to deliver accurate fluid temperatures and fluid O isotope compositions, refining evolving genetic models and developing new tools for exploration.

No Thumbnail Available
Publication

Geochemical and hyperspectral halos associated with VHMS deposits of the Eastern Goldfields Superterrane, Western Australia: insights from the Nimbus, Teutonic Bore and King deposits

2016-02-21, Hollis, Steven P., Gillespie, Paul, Podmore, Darryl, et al.

Despite having been a target for volcanic-hosted massive sulfide (VHMS) mineralization since the 1960s, few resources have been defined in the Archean Yilgarn Craton of Western Australia.

No Thumbnail Available
Publication

Actively forming Kuroko-type VMS mineralization at Iheya North, Okinawa Trough, Japan: new geochemical, petrographic and δ34S isotope results

2016-02-21, Yeats, Christopher, Hollis, Steven P., LaFlamme, Crystal, et al.

In 2010, Integrated Ocean Drilling Program (IODP) Expedition 331 drilled five sites in the Iheya North hydrothermal field in the central Okinawa Trough back - arc basin, Japan. Hydrothermal alteratio n and sulfide mineralization is hosted in a geologically complex, mixed sequence of coarse pumiceous volcaniclastic and fine hemipelagic sediments, overlying a dacitic to rhyolitic volcanic substrate.

No Thumbnail Available
Publication

2.7 Ga plume associated VMS mineralization in the Eastern Goldfields Superterrane: insights from the Ag-Zn-(Au) Nimbus deposit

2016-09-04, Hollis, Steven P., Mole, D., Gillespie, Paul, et al.

Economic volcanic - hosted massive sulfide (VHMS) deposits of the Archean Yilgarn Craton, Western Australia, are restricted to zones of juvenile crust as revealed through regional Nd, Pb and Hf isotopic variations and the geochemistry of felsic volcanic rocks. Interpreted as Archean paleo - rift zones, one of these runs N - S through the Eastern Goldfields Superterrane (broadly coincident with the Kurnalpi Terrane) and is associated with the high grade ca. 2690 Ma Teutonic Bore, Jaguar and Bentley deposits, plus sub - economic VHMS mineralization further south. To date, only small, historic Cu deposits (e.g. Anaconda) and barren pyritic lenses have been recognised in the older 2.7 Ga plume - dominated lower stratigraphy of the Eastern Goldfields.

No Thumbnail Available
Publication

The bimodal fluid evolution of the Nimbus Zn-Ag deposit: an Archean VHMS with epithermal characteristics

2017-08-23, Caruso, Stefano, Fiorentini, Marco L., LaFlamme, Crystal, Hollis, Steven P., et al.

The Nimbus Zn-Ag VHMS deposit represents an exceptional mineralised occurrence in the Yilgarn Craton. While other VHMS systems in the craton are restricted to paleo-rift zones, Nimbus is associated to a plume-related stratigraphy (Hollis et al., 2017). Furthermore, the epithermal characteristics resulting from low temperature and shallow water conditions allowed the development of an unusual mineralisation dominated by Ag-rich sulfosalts. In this study we take advantage of state-of-the-art in-situ techniques to investigate the fluid evolution of this peculiar VHMS system. From the trace element compositions and S-isotope signatures we suggest that Nimbus experienced a bimodal fluid evolution consisting of (i) an initial intense interaction between deep-magmatic fluids and seawater that developed barren pyritic lenses, and (ii) a subsequent closure of the hydrothermal system during which the Agrich ore formed sourcing sulfur almost entirely from a deepmagmatic source.

No Thumbnail Available
Publication

The origin and nature of hydraulic fractures and veins within the Burren, County Clare, Ireland

2019-01-01, Walsh, John J., Moore, John Paul, Bunce, Colin, Hollis, Steven P., Kelly, J. (John), Menuge, JF

Carboniferous (Mississippian) limestones of the Burren are cross-cut by sub-vertical veins, from 1µm up to 50cm thick, defining a strongly clustered and scale-indepen-dent system in which predominantly N-S veins are transected by longer NNE-trending veins. Vein infills mainly comprise of calcite, but with subordinate amounts of quartz, sulphide (mainly galena and sphalerite) and fluorite also occurring, particularly in the south-central part of the area. Thinner and shorter veins are planar and discontinuous in plan view, sometimes forming en-echelon arrays, with thicker veins forming better connected and more complex structures which extend for several kilometres across the Burren region. Veins with ‘exotic’ infills are generally both longer and thicker, and they appear to be spatially associated with, or up to 5km to the north of, a 5km wide zone of ENE-trending Variscan monoclinal folding. Individual veins are vertically persistent, and the same structures are seen throughout the exposed ca 1200m thick Carboniferous sequence, from Tournaisian limestones through to Serpukhovian-Bashkirian siliciclastics. The veins are mainly extensional, sometimes with a component of sinistral displacement particularly on NNE-trending veins, displaying fibrous growth through to hydraulic fracturing and brecciation. Their formation is attributed to the valving of overpressured fluids within Mississippian basins during N-S Variscan compression. Pb isotope analysis supports a model in which sulphide infills are scavenged from underlying basement rocks or hydrothermal Zn-Pb mineralisation during the tectonic inversion of post-rift sequences overlying Lower Carboniferous normal faults.

No Thumbnail Available
Publication

Targeting VHMS mineralization at Erayinia in the Archaean Yilgarn Craton, Western Australia: geochemical and hyperspectral halos

2017-04-03, Hollis, Steven P., Podmore, Darryl, James, M.

Despite having been a target for volcanic-hosted massive sulfide (VHMS) mineralization since the 1960s, few resources have been defined in the Archean Yilgarn Craton of Western Australia. Exploration challenges associated with regolith and deep cover exacerbate the already difficult task of exploring for small, deformed deposits in stratigraphically complex volcanic terranes.