Early Earth Evolution

This group's interests lie in understanding the origin and evolution of early life on Earth and the dynamics of Precambrian provinces with multiphase thermal and deformational histories.

The tectonic significance of regional flat-lying fabrics in Precambrian rocks, Antarctica

Field-based project started in 1996 with support from the Australian Antarctic Division and ASAC, to place rocks from near the contact between the Archaean Napier and Proterozoic Rayner Complexes into their geological context in terms of the evolution of Gondwana. Work to date has addressed key structural, metamorphic and age relationships along the MacRobertson and Kemp Land coastlines, in collaboration with Prof. R. White (University of Mainz) and Dr Nathan Daczko (Macquarie University).

Plate tectonics – the ultimate process controlling change on Earth – produces a remarkable array of rock types. The approximately one billion year old rocks exposed along the Kemp and MacRobertson Land coast have been exhumed from the deep crust (~25 km depth) to be at Earth’s surface today. These rocks contain flat-lying fabrics that extend for hundreds of kilometres that do not resemble modern-day flat-lying rock fabrics. Fieldwork approved for the 2007/08 summer, but delayed to 2008/09 due to logistic problems, will characterise contrasting relationships in ancient rocks from two representative Antarctic locations, to examine the tectonic significance of the regional flat-lying rock fabrics. Prospective PhD students are invited to contact Prof. Geoff Clarke with respect to being involved in the project.

Emergence of the continents

The time interval 2.7 ± 0.05 Ga stands as the most dramatic in the Earth’s history. A large number of profound anomalies, from the core, to the mantle, to the crust, to the hydrosphere, to the atmosphere and finally to the biosphere, dresses a compelling case for a period of major re-organization in all the Earth’s envelops. The global changes that took place in the Late Archaean were the prelude to the birth of modern Earth. We developed a robust numerical model in linking the emergence of the continent to the secular cooling of the convective mantle. This work a part of a PhD cotutelle of Nicolas Flament which challenges the common view that the elevation of the surface of the continents was constant through time. In contrast, in seems that the emergence of the continents occurred during the late-Archaean.

The emergence of the continent in the late Archaean allowed for the coupling between the crustal geochemical reservoir with the mantle reservoir through erosion and subduction of continent-derived sediments. Therefore, the emergence of the continent could explain how the Earth system evolved from a period of crustal-growth (Archaean eon) to a period where crustal growth and recycling balance each other. For futher details contact Dr Patrice Rey.

Earth’s early biosphere and environments

Of all potential sources of biogeochemical information of early life, oil inclusions provide the most optimal conditions for the preservation of fossil microbial biosignatures even in rocks where other forms of organic matter are highly altered or absent. The aim of this 5-year ARC discovery project is to determine the molecular composition, including biomarkers, of oil preserved in inclusions and the environmental context of rocks of different ages through the early Earth's history from 3.25 to 1.6 Ga. The data will substantially enrich the organic geochemical record of the early Earth and hence provide new insights into the diversity and evolution of the early biosphere, the timing of the branch points on the Tree of Life, and how biosphere evolution and geochemical environments were linked in the early Precambrian. For further details contact Dr Adriana Dutkiewicz.

Early Ocean

Pristine diamond drill cores recently collected in the Pilbara Craton of Western Australia presents a unique opportunity to constrain the chemistry of the earliest ocean and the composition of the atmosphere and microbial ecosystems spanning the Archaean Eon. We use high-resolution methods including synchrotron-based techniques and vibrational spectroscopy on microfossils and fluid inclusions to gain insights into interactions between hydrothermal circulation, ocean water and mantle-derived fluids. This ARC International Linkage project will greatly expand our knowledge of the Earth's early habitats and the evolution of the primordial oceans and atmosphere. It may even provide new clues on the origin of life. For more information contact , Dr Patrice Rey or Dr Adriana Dutkiewicz.

Fluid-Rock interaction in the primitive Earth

In the primitive Earth, a wide range of phenomena including the formation of gold deposits and volcanogenic massive sulfide deposits (VMS), as well as the development of sulphur-supported ecosystems at hydrothermal vents were related to the mobilisation of mineralised fluids through the crust and their channelling toward the surface. Therefore, identifying and characterising crustal-scale Archaean plumbing systems and their tectonic settings is one of the most fundamental problems in Archaean geology and exobiology.

The east Pilbara craton in Western Australia hosts some of the oldest lode-gold deposits, VMS deposits, and traces of biological activity on Earth, all within a few tens of kilometres. It is one of the best-preserved and readily accessible Archaean cratons, a natural laboratory for early Earth processes and a region of unique significance to the world’s geoscientists and geobiologists alike.
Through ARC funded projects we are decoding, with a multidisciplinary team of researchers, the geological record of the east Pilbara craton. Our tools range from structural geology, to synchrotron radiation X-ray fluorescence to numerical modelling. For more information contact Dr Patrice Rey.

Magmatism and tectonics

Igneous rocks provide key insights into mantle and crustal processes that help to illuminate the planet’s early tectonic evolution. As on the modern Earth, recurring associations of different igneous rocks, rather than occurrences of any single rock type, provide the strongest criteria for testing tectonic models. Two important rock associations are presently the focus of study. One includes rocks widely considered to reflect the melting of subducting oceanic crust and related magma types that were generated by the interaction of such melts with the Earth’s mantle. Archean examples from 2.7 to 3.5 billion years ago are being compared to much younger counterparts from Xinjiang (northwest China) and Tibet in close collaboration with Prof. Wang Qiang (Guanzhou Inst. of Geochemistry). The other association involves moderately potassic shoshonitic rocks which possess a range of chemical characteristics that are widely considered to reflect the distinctive processes associated with modern-style subduction, the hallmark of plate tectonics. The relationships between these magma types and diamond and gold deposits are of particular economic interest and are the subject of collaborative studies with Professors P. Hollings and R. Mitchell in Canada. For further information contact Dr Derek Wyman.