HR: 16:45h
AN: U24A-04    [Abstracts]
TI: Tectonic Implications of a Crustal Scale 3D Model of the Eastern Mount Isa Inlier
AU: * Blenkinsop, T G
EM: Thomas.Blenkinsop@jcu.edu.au
AF: School of Earth and Environmental Sciences and pmdCRC, James Cook University, Douglas Campus, Townsville, QLD 4811, Australia
AU: Lepong, P
EM: Piter.Lepong@jcu.edu.au
AF: School of Earth and Environmental Sciences and pmdCRC, James Cook University, Douglas Campus, Townsville, QLD 4811, Australia
AU: Huddlestone-Holmes, C
EM: cameron.hholmes@jcu.edu.au
AF: School of Earth and Environmental Sciences and pmdCRC, James Cook University, Douglas Campus, Townsville, QLD 4811, Australia
AB: A 3D model of the eastern part of the Proterozoic Mount Isa inlier has been constructed from surface geology, aeromagnetic and gravity data (including worms - multiscale wavelet edges of potential field data) and reinterpretation of seismic reflection data. The model was built from serial cross sections in GoCad, and has a volume of 200 km x 150 km x 50 km, to the base of the unusually thick crust. It shows major faults, lithostratigraphic units, and intrusions. The major feature of the model is a deepening of the cover sequence metasedimentary rocks in the center of the area, which coincides with an increase in stratigraphic thickness and is contained between two crust-penetrating faults that have reverse separations at surface. These features are interpreted as the result of positive inversion, in which major basin-bounding faults were reactivated as reverse faults, but preserve their original extensional geometry at the base of the cover sequences. The localization of contractional structures over the original extensional faults limits the amount of displacement that can have occurred on the reverse faults. Significant changes in model geometry occur from south to north along the strike of the inlier, and may be original variations in basin geometry. The model shows that dioritic - granitic composite batholiths, which postdate the major contractional Isan orogeny, are tabular features no more than a few km thick, and are spatially associated with the major faults. Batholith intrusion may have occurred by dike-like ascent along the major faults and sill-like emplacement. Estimates of the minimum volume of the intrusions can be made from the model, which need to be reconciled with isotopic constraints that suggest crustal sources for the batholiths. These observations and tectonic implications follow directly from constructing the geospatial model, and illustrate its major benefit: spatial relationships are revealed in 3D on a crustal scale. Quantitative data from these sorts of models are remarkably useful in tectonics.
UR: http://www.pmdcrc.com.au/final_reports_projectI2.html
DE: 0905 Continental structures (8109, 8110)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8035 Pluton emplacement
DE: 8038 Regional crustal structure
DE: 8102 Continental contractional orogenic belts and inversion tectonics
SC: Union [U]
MN: 2007 Fall Meeting