Professor Tim Bell
Adjunct Professor, Structural Geology
BSc (Adelaide Uni)
BSc Hons (Adelaide Uni)
PhD (Adelaide Uni)
Visit: Room DB034-029D, Townsville campus
Call: (+61) 7 4781 4766
Fax (+61) 7 4781 4020
The inter-relationship between deformation, metamorphism and tectonics:
The Appalachians of the USA contain a wide distribution of porphyroblastic rocks (of variable composition) that commonly contain complex inclusion trails. These porphyroblasts have grown during one or more of the Taconic, Acadian and Alleghanian orogenies and are ideal for using foliation intersection axes in porphyroblasts (FIA) to determine:-(a) deformation processes and mechanisms of folding,(b) metamorphic processes and mechanisms of reaction,(c) whether porphyroblast nucleation/growth and/or overgrowth can be distinguished microscopically for different periods of metamorphism within and between orogenies,(d) whether the metamorphic P-T-t paths of these rocks can be related to the structural paths (using inclusion trail asymmetry) and the direction of compression indicated by the orientation of the FIA,(e) whether the ages of successive FIA generations can be determined from microprobe dating of monazite inclusions,(f) whether successive FIA remaining consistently oriented for large distances along orogens enables one to interpret successive directions of Paleaozoic Plate Motions for Appalachian orogenesis.
Structural control of ore-deposits. Research is being conducted on ore-deposits from around the world, particularly in porphyroblast bearing host rocks, but concentrating in the Mount Isa Province, which contains a large number of newly discovered world class Ag-Pb-Zn, Cu and Cu-Au deposits. The future of exploration within this latter terrain depends on the development of a complete understanding of the structural history of the host rocks, which appear superficially simple but actually have undergone a very complex history of deformation, as well as the structural timing and controls of mineralization.
Brief description of research impact:
Sites of mineralization for exploration at Cannington mine. Mineralization prior to our work was thought to be synsedimentary. Our work showed that it was syntectonic and formed during the development of N-S striking structures. Consequently, exploration had to be modified to drill for structural traps rather than by following out stratigraphic units
Bell, T.H. & Welch, P.W., 2002. Prolonged Acadian Orogenesis: Revelations from FIA Controlled Monazite Dating of Foliations in Porphyroblasts and Matrix. American Journal of Science, 302, 549-581.
Bell, T.H., Ham, A.P. & Kim H.S., 2004. Partitioning of deformation along an orogen and its effects on porphyroblast growth during orogenesis. Journal of Structural Geology, 26, 825-845.
Ham, A.P. & Bell, T.H., 2004. Recycling of foliations during folding. Journal of Structural Geology, 26, 1989-2009.