Geochronology is the vital fourth dimension for geological knowledge. It provides the temporal framework for understanding and modelling geological processes and rates of change. Incorporating geochronological 'observations and measurements' into interoperable geological data systems is thus a critical pursuit. - Although there are several resources for storing and accessing geochronological data, there is no standard format for exchanging such data among users. Current systems are a mixture of comma-delimited text files, Excel spreadsheets and PDFs that assume prior specialist knowledge and frequently force the user to laboriously - and potentially erroneously - extract the required data manually. - Geoscience Australia and partners are developing a standard data exchange format for geochronological data ('geochronML') within the broader framework of Observations and Measurements and GeoSciML that are an important facet of emerging international geoscience data format standards. - Geochronology analytical processes and resulting data present some challenging issues as a rock "age" is typically not a direct measurement, but rather the interpretation of a statistical amalgam of several measurements chosen with the aid of prior geological knowledge and analytical metadata. The level at which these data need to be exposed to a user varies greatly, even to the same user over the course of a project. GeochronML is also attempting to provide a generic pattern that will support as wide as range of radioisotopic systems as possible. This presentation will discuss developments at Geoscience Australia and the opportunities for collaboration.

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Abstract for 34th IGC

A compilation of abstracts of talks and posters presented at the Broken Hill Exploration Initiative (BHEI) 2003 conference at Broken Hill, 7-9 July 2003.

This GSQ-GA geochronology record presents a compilation of 16 new zircon U-Pb SHRIMP geochronological results from the Mount Isa and south Nicholson region, Queensland. This data was collected through the collaborative GSQ-GA geochronology project in August 2008 as part of the National Geoscience Accord (NGA) and in support of ongoing geoscientific investigations and regional geological mapping by the GSQ in the Mount Isa and south Nicholson regions. In addition, an appendix contains Sm-Nd whole rock analyses of selected samples. The acquisition of the Sm-Nd data in Appendix A was funded wholly by Geoscience Australia. A separate report for each sample is presented, which contain a brief geochronological interpretation as well as information on sample location and geological context. Three samples were analysed from the south Nicholson Basin from the WESTMORELAND and LAWN HILL 250K mapsheets, with an additional sample (Westmoreland Conglomerate) taken from the base of the Macarthur Basin. The twelve remaining samples were taken from various units in the greater Mount Isa region from the CLONCURRY, DOBYNN, DUCHESS, MOUNT ISA and URANDANGI 250K mapsheets. One sample was submitted for SHRIMP analysis but which failed to yield sufficient zircons for further investigation (rhyodacitic porphyry from within the Corella Formation).

This Record contains zircon U-Pb geochronological data obtained between September 2001 and June 2002 on rocks from the Yilgarn Craton, Western Australia. In addition, data are presented for rutile from sample 2001969019A. Zircon from this sample was analysed in the first year of the project (Fletcher et al., 2001). Additional zircon data for this sample are also reported here.

Poorly exposed Paleoproterozoic sandstones and siltstones of the Killi Killi Formation record developement of a large turbidite complex. Killi Killi Formation sediments were eroded from the uplifted ~1860 Ma Nimbuwah and Hooper Orogens as indicated by detrital zircons with sediment deposition at ~1840 Ma. Facies analysis, isopach maps and detrital zircon populations, combined with Sm-Nd data from the Tanami region and Halls Creek Orogen, confirm the previously suggested correlation of the Paleoproterozoic successions in the Eastern zone of the Halls Creek Orogen and the Tanami region. Detrital zircons from the Aileron Province suggest the turbidite complex extends into the Arunta region, however, high metamorphic grade precludes direct facies comparisons in the Arunta region. Portions of the turbidite complex in the Tanami region are dominated by mudstones, consisting of low-density turbidites and associated hemipelagites, that potentially acted as a redox boundary to gold-bearing fluid. Gold prospectivity in turbiditic systems is increased within these mudstone sequences with the potential for further gold discoveries.

Legacy product - no abstract available

New SHRIMP U/Pb zircon ages of 472.2 ± 5.8 Ma and 470.4 ± 6.1 Ma are presented for the age of peak metamorphism of Barrovian migmatite units. Magmatic advection is thought to have provided significant heat for the Barrovian metamorphism. Published U/Pb emplacement ages for Grampian-age igneous units of Scotland and Ireland define a minimum age range of c. 473.5 to c. 470 Ma for Barrovian metamorphic heating. The new U/Pb ages are consistent with attainment of peak Barrovian metamorphic temperatures during Grampian magmatism. U/Pb-calibrated 40Ar/39Ar ages for white mica from the Barrovian metamorphic series vary systematically with increasing metamorphic grade, between c. 465 Ma for the biotite zone and c. 461 Ma for the sillimanite zone. Microstructural work on the timing of metamorphism in the Barrovian metamorphic series has shown that peak metamorphism occurred progressively later with increasing peak-metamorphic grade. Younging metamorphic age with increasing metamorphic grade across the Barrovian metamorphic series requires that the sequence was cooled in the lower-grade regions while thermal activity continued in the high-grade regions. This thermal scenario is well explained by the presence of a large-scale extensional detachment that actively cooled units from above while the Barrovian metamorphic heating continued at greater depth in the footwall. The spatio-temporal thermal pattern recorded by the Barrovian metamorphic series is consistent with regional metamorphism during crustal extension.

No abstract available