Paper No. 48-4
Presentation Time: 2:20 PM
MINERAL INCLUSION ASSEMBLAGE AND COMPOSITION FOR DETRITAL ZIRCON PROVENANCE (Invited Presentation)
Igneous zircon often contains abundant mineral inclusions, and these inclusions represent a parallel record of detrital zircon provenance complementary to the age and geochemistry of the host zircon. However, relatively few studies have surveyed granitoid zircon suites to determine the relationship between whole-rock chemistry and inclusion assemblage or composition. Previous have shown that apatite is disproportionately represented in many zircon inclusion suites and that while mafic inclusion phases tend to reflect the composition of the same phase in the whole rock, quartz and feldspar inclusions tend to be shifted toward artificially felsic compositions relative to the whole rock. We have surveyed zircons from 24 Phanerozoic granitoids of varying composition and find that although felsic inclusions do not reflect whole rock composition, apatite abundance is broadly correlated with whole rock SiO2. Fe-Ti oxide and sulfide inclusions provide clues to source rock redox. The composition of magmatic biotite allows for the distinction of magnetite- vs. ilmenite-series as well as peraluminous, metaluminous, and peralkaline sources. Using these coupled approaches, Hadean detrital zircons from the Jack Hills (Western Australia) appear to derive from an overall felsic source with a mixture of metaluminous and reduced peraluminous magmas. Eoarchean detrital zircons from the Nuvvuagittuq supracrustal belt (northern Quebec) may derive from either a felsic or intermediate source with most likely an oxidized peraluminous character. Further development of minor inclusion phases (e.g., oxides, sulfides) as petrologic indicators will allow for greater understanding of the diversity of magmas on the early Earth.