Tectonothermal events in the Olympic IOCG province constrained by apatite and REE-phosphate geochronology

摘要: The Olympic iron oxide–copper–gold province in South Australia contains numerous deposits and prospects, including the Dam Cu–U–Au–Ag deposit Acropolis prospect. prospect comprises massive, coarse-grained magnetite–apatite veins partly replaced by a hematite-stable assemblage. apatite grains contain zones with abundant inclusions of other minerals (including monazite xenotime) low trace-element concentrations relative to inclusion-free zones. inclusion-rich are interpreted be formed from recrystallisation remobilisation U, Th rare earth element (REE) into xenotime. Apatite, xenotime all established U–Th–Pb geochronometers offer potential constrain alteration history LA-ICPMS U–Pb age is within error host volcanic units (ca 1.59 Ga). Inclusion-rich yields both near-concordant analyses that as well highly disturbed (discordant) analyses. most concordant (Th–Pb) (U–Pb) rim indicate an event occurred at ca 1.37 Ga possibly also 500 Ma. disparity REE-phosphate (and grains) suggested owing being initially recrystallised modified again later (or coarsened) inclusions. Partial resetting majority presence significant amounts common Pb has complicated interpretation results. In contrast, more robust geochronometer this setting. ages two post-1.59 events appear have affected do not correspond any known Gawler Craton. earlier Ga) instead corresponds best metamorphic–magmatic–hydrothermal activity Laurentia, consistent proximity Laurentia Craton inferred palaeogeographic reconstructions. Ma) Delamerian Orogeny been shown prior studies deposit.