Petrographic & geochronological investigation of S-type granites from a low-pressure high-temperature regional aureole: Mt Stafford, Central Australia : field location, Mt Stafford Anmatjira Range NT, date: 7-12 July 2010 : base camp: 028185N 7558920E (53 WGS84)
thesisposted on 2022-03-28, 21:50 authored by Katherine Farrow
Two S-type granite intrusions form part of a high-temperature low-pressure regional aureole at Mt Stafford, in the Central Australian outback of the Northern Territory. They are intimately related to a package of metasedimentary migmatites and associated mafic sills or lavas of the Mt Stafford Member, locally metamorphosed from greenschist to granulite facies. Petrographic, geochemical and Hf-isotopic analyses indicate the eastern and northern granites are mineralogically and chemically similar, resulting from the same larger thermal event responsible for the metamorphism at Mt Stafford. Hf-isotope compositions suggest a significant contribution of recycled crustal material in local granite production, also reflected by the abundance of inherited zircon, particularly in the northern granite samples. The application of zircon geochronology suggests the granites were emplaced ca. 1786 ±15 Ma,based on magmatic rims of grains with cores interpreted as inherited. Older cores in the eastern granite indicate they are sourced from material ca. 1824 ±14Ma. This indicates that the inherited source from the eastern granite is younger than the surrounding metasedimentary rocks, which are dated at 1866 ±3Ma. A tectonic model is presented involving thrusting of ca. 1866 ±3M metasedimentary crust over 1824 ±14Ma metasedimentary crust. Granite is produced from the partial melting of the deeper, younger crust and emplaced into the older crust.