Professor Bill Collins
PhD (La Trobe)
Visit: School of Environmental and Life Sciences,
University of Newcastle
Granite Petrology and Geodynamics. Although starting my studies on granite petrology, particularly A-type granites, my research has broadenedto understand how and why granites are generated and emplaced within different tectonic settings. This work involves field, structural, geochemical and isotopic studies, and has extended to include the role of basaltic systems in generating and influencing the composition of granitic magmas. As a result, a holistic approach is undertaken to understanding granite systems in geodynamic context.
Granite Petrology and Crustal Growth.
More recently, work in North Queensland (northern Tasmanides) is focused on the determining what granites reveal about the lower crust. A 1000 km long seismic traverse shows several geophysical domains which do no outcrop, so we are systematically analyzing U-Pb, Lu-Hf and O isotopes from zircons from granites along the traverse to unravel the nature of these deep seated regions. The results will have major implications for understanding crustal growth mechanisms.
Global tectonics. Another major research project (ARC Discovery) is to study the causes of Pangean breakup, by focussing on the Mesozoic orogenic development of the Andes and US Cordillera. Was Pangea split apart by thermal upwelling (superplumes) or was it pulled apart at the peripheries by convection associated with subduction retreat? It is in the circum-Pacific orogens that the crust is most likely to record thickening and/or thinning events that coincide with Atlantic opening during Pangean breakup. With Gavin Mantle (PhD student) we have established a global correlation between REE composition of arc basalts and Moho depth from active volcanoes. We can use this correlation to determine when (and by how much) the crust thickened or thinned during orogenic events. Presently, we are applying this concept to Andean and Cordilleran orogenic evolution to answer the Pangean question.
Brief description of research impact:
The North Queensland project is a collaboration with the Geol. Survey of Queensland. Using granite petrology along deep seismic sections to determine the nature of buried geophysical domains is a new way of doing “big science” in Australia, focused on growth and evolution of continental crust.
Collins WJ, Wiebe R, Healy B & Richards SW (2006) Replenishment, Crystal Accumulation and Floor Aggradation in the Megacrystic Kameruka Suite, Australia. Journal of Petrology, 47 (11), 2073 - 2104
Mantle G & Collins WJ (2006) Correlation of REE with Moho depth for modern volcanic arc basalts.
In: Geochimica et Cosmochimica Acta 389 - 389. Elsevier (18)
Collins, W.J., 2003. Slab pull, mantle convection, and Pangean assembly and dispersal. Earth and Planetary Science Letters 205, 225 - 237.
Collins, W.J. 2002. Hot orogens, tectonic switching and creation of continental crust. Geology, 30, 535-538.
Collins W.J. 2002. Nature of extensional accretionary orogens. Tectonics 21 (4); 10.1029/2000TC001272