Steven P. Hollis

Geochemistry, zircon U–Pb geochronology and Hf isotopes of Jurassic-Cretaceous granites in the Tengchong terrane, SW China: implications for the Mesozoic tectono-magmatic evolution of the Eastern Tethyan Tectonic Domain

ABSTRACT Recently identified Early Jurassic, Early Cretaceous, and Late Cretaceous granites of the Tengchong terrane, SW China, help to refine our understanding of the Mesozoic tectonic-magmatic evolutionary history of the region. We present new zircon U–Pb geochronological, Lu–Hf isotopic and geochemical data on these rocks. The zircon LA-ICP-MS U–Pb ages of the Mangzhangxiang, Laochangpo, and Guyong granites, and Guyong granodioritic microgranular enclaves are 185.6, 120.7, 72.9, and 72.7 Ma, respectively. Geochemical and Hf isotopic characteristics suggest the Mangzhangxiang and Laochangpo S-type granites were derived from partial melting of felsic crust and that the Guyong I-type granite and associated MMEs were generated through magma mixing/mingling. Mesozoic magmatism in the Tengchong terrane can be divided into three episodes: (1) the Triassic syn- and post-collisional magmatic event was related to the closure of the Palaeo-Tethyan Ocean, as represented by the Changning-Menglian suture zone; (2) the Jurassic to Early Cretaceous magmatism was related to the subduction of the Meso-Tethyan oceanic crust, as represented by the Myitkyina ophiolite belt; and (3) the Late Cretaceous magmatism was related to the subduction of the Neo-Tethyan oceanic crust, as represented by the Kalaymyo ophiolite belt. GRAPHICAL ABSTRACT

Geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes of the Early Paleogene gabbro and granite from Central Lhasa, southern Tibet: petrogenesis and tectonic implications

ABSTRACT The Tibetan Plateau is a composite orogenic belt that has experienced prolonged subduction, obduction, and collisional processes, during the opening and closure of successive Tethyan oceans. We present new zircon U-Pb ages and Hf isotopes, and whole-rock geochemical and Sr-Nd-Pb isotopic data from the Early Paleogene Longge’er gabbro and Qingduxiang granite of Central Lhasa, southern Tibet. Together these allow us to refine existing models for widespread magmatic activity associated with the subduction of the Neo-Tethyan Ocean. The Longge’er gabbro (53.5 ± 1.6 Ma) belongs to the low-K tholeiitic to medium-K and metaluminous series, while the Qingduxiang granite (54.5 ± 0.9 Ma) is characterized as high-K, calc-alkaline, metaluminous, and of I-type affinity. Both intrusions are enriched in the LREE and depleted in the HREE with negative Eu, Ba, Nb, Ta, Sr, and Ti anomalies. Trace elements characteristics and enriched whole-rock Sr-Nd-Pb and zircon Hf isotopic compositions demonstrate that the gabbro was derived from partial melting of enriched lithosphere mantle metasomatized by Central-Lhasa ancient crustal materials, while the I-type granite was generated by partial melting of Central-Lhasa ancient lower crust combined with magmas derived from Southern-Lhasa juvenile crust. Geochemical compositions of the gabbro and granite reveal the Early Paleogene magmatism was emplaced in a shallow extensional setting related to slab break off following the closure of the Neo-Tethyan Ocean. Combined with previous studies, we can infer slab rollback occurred from Late Cretaceous (~69 Ma) to Early Eocene (55 Ma), while slab break off was shortly lived at ca. 55–49 Ma. Consequently, the India-Asia collision must not have started later than ca. 55 Ma. Graphical Abstract

Clumped C–O isotope temperature constraints for carbonate precipitation associated with the Irish-type Lisheen and Navan Zn–Pb orebodies

margins during episodes of ocean closure has important implications for understanding the formation, preservation and location of mineral deposits in ancient orogens. The Charlestown Group of Co. Mayo, Ireland, forms an important but understudied link in the Caledonian-Appalachian orogenic belt between the well-documented sectors of western Ireland and Northern Ireland. We have reassessed its role in the c. 474–465 Ma Grampian-Taconic orogeny, based on new fieldwork, high-resolution airborne geophysics, graptolite biostratigraphy, U-Pb zircon dating, whole rock and an examination of historic drillcore from across the volcanic inlier. The Charlestown Group is divisible into three formations: Horan, Carracastle, Tawnyinah. The Horan Formation comprises a mixed sequence of tholeiitic to calc-alkaline basalt, crystal tuff and sedimentary rocks (e.g. black shale, chert), forming within an evolving peri-Laurentian affinity island arc. The presence of graptolites Pseudisograptus of the manubriatus group and the discovery of Exigraptus uniformis and Skiagraptus gnomonicus favour a Yapeenian (= late Arenig; Ya2 stage) age for the Horan Formation [equivalent to c. 471.2– 470.5 Ma according to the timescale of Sadler et al. (2009)]. Together with four new U-Pb zircon ages (471–469 Ma) this fauna provides an important new constraint for calibrating the middle Ordovician timescale. Overlying deposits of the Carracastle and Tawnyinah formations are dominated by LILEand LREE-enriched calc-alkaline andesitic tuffs and flows, coarse volcanic breccias and quartz-feldspar porphyritic intrusive rocks, overlain by more silicic tuffs and volcanic breccias with rare occurrences of sedimentary rocks. The relatively young age for the Charlestown Group in the Grampian orogeny, coupled with high Th/Yb and zircon inheritance (c. 2 Ga) indicate the arc was founded upon continental crust (either composite Laurentian margin or microcontinental block). A regional correlation is favoured to the post-subduction flip volcanic/intrusive rocks of the Irish Caledonides, specifically the late-stage development of the Tyrone Igneous Complex, Murrisk Group ignimbrites and late intrusive rocks of Connemara (western Ireland) and the Slishwood Division (Co. Sligo). Examination of breccia textures and mineralisation across the volcanic inlier questions the previous porphyry hypothesis for the genesis of the Charlestown Cu deposit, features more consistent with a volcanogenic massive sulphide (VMS) deposit.

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

a LODE (London Centre for Ore Deposits and Exploration) Department of Earth Sciences, Natural History Museum, London SW7 5BD, UK b iCRAG (Irish Centre for Research in Applied Geosciences) and School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland c Geological Survey Ireland, Beggars Bush, Haddington Road, Dublin 4, Ireland d Geological Survey of Northern Ireland, Dundonald House, Upper Newtownards Road, Belfast BT4 3SB, UK e Imperial College, Exhibition Road, London SW7 2AZ, UK f School of Ocean and Earth Science, National Oceanography Centre, European Way, Southampton University, Southampton SO14 3ZH, UK g NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK h Department of Earth Sciences, Natural History Museum, London SW7 5BD, UK i Core Research Laboratories, The Natural History Museum, London SW7 5BD, UK

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

Actively forming Kuroko-type VMS mineralisation at Iheya North, Okinawa Trough, Japan: New geochemical, petrographic and δS isotope results Christopher Yeats, Steve Hollis, Crystal LaFlamme, Angela Halfpenny, Marco Fiorentini, JuanCarlos Corona, Gordon Southam, Richard Herrington and John Spratt Mineral Resources Flagship, CSIRO, Perth, Australia Geological Survey of New South Wales, Maitland, Australia iCRAG and School of Earth Sciences, University College Dublin, Dublin, Ireland (steve.hollis@icrag-centre.org) Centre for Exploration Targeting, University of Western Australia, Perth, Australia Microscopy & Microanalysis Facility, John de Laeter Centre, Curtin University, Perth, Australia Department of Geological Sciences & Environmental Studies, Binghamton University, USA School of Earth Sciences, University of Queensland, Australia Department of Earth Sciences, Natural History Museum, London, UK