Hollis, Steven P.
Hollis, Steven P.
Hollis, Steven P.
Now showing 1 - 10 of 16
- PublicationGeochemical 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)
; ; ;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. 84
- PublicationAge and geochemistry of the Charlestown Group, Ireland: implications for the Grampian orogeny, its mineral potential and the Ordovician timescale(Mineral Deposits Studies Group, 2016-12-24)
; ; ;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. 300
- PublicationConstraining fluid mixing processes at the Irish-type Lisheen and Navan Zn-Pb orebodies: preliminary evidence from clumped C-O isotopes(2016-09-04)
; ; ; ;Our research has applied the clumped O-C isotope technique to the Irish Zn-Pb ore field. Preliminary clumped C-O data will be presented from the Lisheen Zn-Pb orebody (22.3 Mt mined at 11.7% Zn and 2.0% Pb)  along with fluid inclusion data . Samples were analysed from all main carbonate generations across the deposit , including: regional dolomite (D 1), dark grey to black pre-ore hydrother mal dolomite (D 2 ; also known as black-matrix breccia), medium-to-coarse-grained ore-stage white ferroan dolomite (D 3 ; white-matrix breccia) , late veins of ferroan dolomite (D4) and white calcite (C4), post-ore crosscutting pink saddle dolomite (D 5), and post-ore white blocky calcite (C 6). We will discuss existing metallogenetic models for the Lisheen deposit and the potential for clumped C-O analysis to constrain fluid flow pathways and mixing processes, and as a tool for mineral exploration . 150
- PublicationEnhancing current understanding of Irish Zn-Pb mineralization: a closer look at the Island Pod orebody, Lisheen deposit(Society for Geology Applied to Mineral Deposits, 2017-08-23)
; ; ; ;Irish-type deposits are a series of Zn-Pb orebodies, formed from the carbonate replacement of Lower Carboniferous limestone, triggered primarily by fluid mixing. Current understanding of the complex fluid flow and mixing dynamics associated with mineralization is limited. By applying clumped O-C isotope analysis to these deposits, these processes can be constrained. Preliminary paragenetic studies of the Island Pod orebody (0.4 Mt @ 20% Zn & 1.6% Pb) have yielded textural evidence for early fluid mixing of sulphide-rich fluids, in a quiescent, far-from equilibrium environment, resulting in the rapid precipitation of dendritic galena and intergrowths of dolomite and sphalerite. Initial clumped O-C analysis has revealed temperatures of 100-170°C for hanging-wall white matrix breccias that accompanied ore formation. This technique will be used to constrain temperature variations across the orebody, thus yielding information on how the fluid evolved as precipitation continued. A more detailed paragenetic study is underway and will form the foundation of future clumped O-C isotope and Zn-Cu-S isotope analysis. 254
- PublicationActively forming Kuroko-type VMS mineralization at Iheya North, Okinawa Trough, Japan: new geochemical, petrographic and δ34S isotope results(Taylor & Francis, 2016-02-21)
; ; ;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. 138
- PublicationA comparison between clumped C-O and fluid inclusion temperatures for carbonates associated with Irish-type Zn-Pb orebodies(Institut de Physique du Globe de Paris, 2017-08-12)
; ; ; ;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. 314
- PublicationControls on the formation of a large Zn-Pb Irish-type deposit: evidence from the Navan halos(Irish Association for Economic Geology, 2017-05-14)
; ; ;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. 92
- PublicationPreliminary structural constraints from the Tyrone Igneous Complex and its metamorphic basement(2018-02-25)
; ;The Grampian orogeny of the British and Irish Caledonides records the progressive accretion of a series of arcs, ophiolites and microcontinental blocks to the Laurentian margin between the Late Cambrian and Middle Ordovician. Accreted oceanic tracts contain elevated, but sub-economic concentrations of the Platinum Group Elements in the Shetland and Ballantrae ophiolites, Scotland, and potentially economic Cu-Zn-Pb-Ag-Au deposits in volcanic arc sequences of counties Tyrone and Mayo. Orogenic collapse was associated with significant Au mineralization in the deformed passive margin sequences (=Dalradian Supergroup) of Northern Ireland, with the UKs largest gold deposit at Curraghinalt and only active gold mine at Cavanacaw. The Curraghinalt deposit contains at least 3.5 Moz of Au, with precious metals likely to have been sourced from the underlying Tyrone Igneous Complex (TIC) – a structurally dismembered Ordovician arc-ophiolite sequence that also locally contains high-grade Au mineralization. Despite its importance and extensive research on the TIC in the last ten years, no detailed study has been undertaken on its structural history. We present preliminary results of structural measurements made across the TIC and its underlying metamorphic basement (=Tyrone Central Inlier). These were made by mapping of the Corvanaghan and Fir Mountain quarries in the Tyrone Central Inlier, as well as mapping of outcrops in the Tyrone Volcanic Group (e.g. Carnanransy Burn, Tullybrick, Cashel Rock, Beaghbeg). The Tyrone Central Inlier exposed in the quarries is composed of amphibolite facies rocks – predominantly metabasite and psammite, and minor metapelites. Leucosome-rich zones occur in the metabasites. Dips of these leucosome fabrics, bedding dips and first foliations are either similarly dipping, or show rotations around an identical SW-NE-oriented axis. Two generations of faulting are apparent in the Tyrone Central Inlier, with high angle oblique-slip to strike-slip faults with dextral indicators, crosscut by a family of dip-slip planar fault zones, with a normal sense where measurable. Zones of gold-bearing pyrite and chalcopyrite (with malachite staining) were observed near veins and faults that are N-S oriented in Corvanaghan quarry. Pegmatite and muscovite granite intrusions crosscut deformation fabrics. 58
- PublicationAge and Geochemistry of the Charlestown Group, Ireland: Implications for the Grampian-Taconic Orogeny and Regional Mineral Potential(The Geological Society of America, 2015-11-04)
; ; ;Here we extend the analysis of the Irish Caledonides to the Charlestown Group, located geographically between the well - studied Grampian terranes of South Mayo and Tyrone. 62
- PublicationPreliminary paragenetic studies of the high grade Island Pod Zn-Pb orebody, Lisheen(The Institute of Geologists of Ireland, 2017-03-05)
; ; ;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. 72