Summary of results. NTGS in situ (U Th)-Pb monazite geochronology project: Constraining the chronologic history of the Aileron Province in the Delny Shear Zone, Dneiper 1:100 000 mapsheet

Abstract

This Record presents chemical and chronologic data collected on monazite at the Central Science Laboratory at the University of Tasmania in March and October of 2018 in support of the Northern Territory Geological Survey (NTGS) regional geoscientific investigations and mapping programs. Chemical data and interpretations for monazite from two samples taken from the Aileron Province in Dneiper1 (HUCKITTA) in the Northern Territory are presented herein.

Two samples of an unnamed orthogneiss (HU17AWE1585 and HU17AWE1613) were collected from outcrop in the Delny Shear Zone. Both orthogneiss outcrops are overprinted by a schistose, mica-rich mylonite fabric that is interpreted to have formed during the youngest mylonitic deformation event in the Aileron Province portion of the Delny Shear Zone. Monazite deformed by the mylonite fabric in the samples were analysed in order to constrain the timing of mylonite fabric development. Sample HU17AWE1585 records an ambiguous result that suggests Statherian (Palaeoproterozoic) or Calymmian (Mesoproterozoic) monazite growth occurred during formation of micro-shear zones in the sample. This sample also records evidence for isotopic resetting during the Palaeozoic.

Sample HU17AWE1613 records two monazite ages at 1678 ±6 Ma and 1569 ±12 Ma. Both ages are interpreted to pre-date a phase of deformation related to extensive fabric-parallel fracture development in all monazite observed in the sample. It is unclear when the main fabric formed; however, it is unlikely to have developed after the Mesoproterozoic due to the lack of any monazite younger than the Mesoproterozoic.