In situ apatite and carbonate Lu-Hf and molybdenite Re-Os geochronology for ore deposit research:Method validation and example application to Cu-Au mineralisation  

作　　者：Alexander Simpson Stijn Glorie Martin Hand Sarah E.Gilbert Carl Spandler Marija Dmitrijeva Greg Swain Angus Nixon Jacob Mulder Carsten Münker 

机构地区：[1]Department of Earth Sciences,University of Adelaide,SA 5005,Australia [2]Mineral Exploration Cooperative Research Centre,University of Adelaide,SA 5005,Australia [3]Adelaide Microscopy,University of Adelaide,SA 5005,Australia [4]Fortescue,Level 287,Adelaide Terrace,East Perth,WA 6005,Australia [5]Institute of Geology und Mineralogy,University of Köln,50674 Köln,Germany [6]British Geological Survey,Nottingham,UK

出　　处：《Geoscience Frontiers》2024年第5期339-354,共16页地学前缘（英文版）

基　　金：supported by an Accelerated Discovery Initiative Grant(ADI RD02/260),entitled‘Integrated Exploration Under Deep Cover‘with joint funding from Fortescue and the Government of South Australia;SG was further supported by an Australian Research Council Future Fellowship(FT210100906);The acquisition of isotope-dilution Lu-Hf dates was financially supported by the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Program。

摘　　要：The development of laser ablation inductively coupled plasma quadrupole tandem mass spectrometry(LA-ICP-Q-MS/MS)opens new opportunities to rapidly date a variety of hydrothermal minerals.Here we present in situ Lu-Hf and Re-Os dates for hydrothermal apatite and molybdenite,respectively.We further report the first in situ Lu-Hf dates for bastnäsite,dolomite,and siderite,and assess their potential for constraining ore deposit geochronology.For method validation,we report isotope-dilution Lu-Hf dates for apatite reference material Bamble-1(1102±5 Ma)and calcite reference material ME-1(1531±7 Ma),enabling improved accuracy on matrix-matched calibration for LA-ICP-MS/MS Lu-Hf dating.The new methods are applied to the Vulcan Iron-Oxide Copper-Gold(IOCG)prospect in the Olympic Cu-Au Province of South Australia.Such deposits have been difficult to accurately date,given the general lack of reliable mineral geochronometers that are cogenetic with IOCG mineralisation.Hydrothermal apatite Lu-Hf dates and molybdenite Re-Os dates demonstrate that mineralisation at Vulcan largely occurred at ca.1.6 Ga,contemporaneous with the world class Olympic Dam deposit.Our data also indicates that the Lu-Hf system in apatite is more robust than the U-Pb system for determining the timing of primary apatite formation in an IOCG system.We further demonstrate that dolomite can retain Lu-Hf growth ages over an extended time period(>1.5 billion years),providing constraints on the timing of primary ore mineral crystallisation during brecciation and IOCG mineralisation.Finally,late Neoproterozoic(ca.589–544 Ma)and Carboniferous(ca.334±7 Ma)Lu-Hf dates were obtained for texturally late Cubearing carbonate veins,illustrating that the carbonate Lu-Hf method allows direct dating of Cu remobilisation events.This has important implications for mineral exploration as the remobilised Cu may have been transferred to younger deposits hosted in Neoproterozoic sedimentary basins overlaying the Olympic IOCG province.

关 键 词：Reaction-cell ICP-MS In-situ geochronology LU-HF RE-OS Iron Oxide Copper Gold Metal fluids 

分 类 号：P624[天文地球—地质矿产勘探]