[Aqualist] Potential Ph.D projects at University of Queensland

[Dr Jian-xin Zhao]

POTENTIAL PhD PROJECTS in EARTH SCIENCES



Project 1: U-series dating and multi-proxy climate records in speleothems -
comparison between Northern and Southern Hemisphere records, jointly
supervised by Zhao, Golding and Uysal



Study of Quaternary climatic records is the key to understanding of
mechanisms driving climate change, assessment of anthropogenic impact on
current climate and prediction of future climate trend and catastrophic
climatic events. Precise and reliable dating of various climatic archives
and multi-proxy characterisation of such archives are crucial to the
resolution of such fundamental issues. This project attempts to use
speleothems as a climatic archive to place constraints on fundamental issues
in Quaternary climatic studies, such as the timing and characteristics of
the Last Interglacial and sub-orbital climatic oscillations on millennial to
decadal time scales (particularly during the Last Glacial and Holocene
period). The proposed study will also provide a better understanding of the
East Asian and Australian monsoon activity and the rainfall variation in
Australia and their relationship to the El Nino - Southern Oscillation
(ENSO) that is vital to Australia's sustainable economic development and
social well-being.

Speleothems, secondary calcite deposits (e.g. stalagmite, stalactite and
flowstone) formed in caves, contain valuable palaeoclimatic information in
terms of variations in their chemical and stable isotopic compositions
through time. They form across a wide range of climatic zones during periods
of severe climatic changes, and are therefore widely available for sampling.
Compared with other terrestrial records, speleothems have the advantage to
be accurately dated back to ~600 kyr BP by uranium (U)-series disequilibrium
methods, allowing climatic proxies to be placed into an accurate
chronological framework. A number of proxies in speleothems, such as C-O-Sr
isotopes, trace element ratios (e.g. Sr/Ca, Ba/Ca, U/Ca), growth rate
variations and luminosity of growth bands, can be used to extract
palaeoclimatic information.

During our previous studies, we have collected a large number of speleothems
from caves in Australia, China and Turkey and still maintain a good working
relationship with local cave management authorities.

The successful candidate will be expected to undertake some field
investigation and sample collection in key sites. Afterwards, the candidate
will undertake high-precision U-series dating and stable isotope and trace
element analyses of the newly-collected and existing speleothems using UQ's
state-of-the-art isotope and trace element facilities.  The major objective
of this project is to compare climate proxy changes between Northern (China,
Turkey) and Southern (Australia, New Zealand) Hemispheres records for
comparable time periods, with particular focus on the Last Interglacial and
the transition between Last Glacial to Holocene.  Stalagmites dated to form
during such periods are already available under collection.



Project 2: U-series dating and multi-isotope analysis of travertine in
co-seismic fissures - constraints on earthquake recurrence and mantle
degassing in Turkey, jointly supervised by Uysal, Zhao and Golding



The tragic effects of major earthquakes have been a major concern in human
history, so understanding and predicting such devastating events is of
paramount importance.  Reconstruction and quantification of recurrence rates
of prehistoric seismic events is crucial to understanding recent seismic
activity and quantifying future activity.  Before the invention of the
seismograph in the 1880's, the occurrence and magnitude of earthquakes were
often poorly constrained.  An additional problem is that historical and
instrumental records are far too short for evaluation of long-term seismic
activity.

This project aims to develop a new method that allows precise dating of late
Quaternary seismic events (in the time range of 0-500,000 years before
present) using the uranium-series technique.  Samples for dating will be
collected from travertine deposits precipitated from hot-spring waters in
extensional fissures along major active faults in western Turkey and from
the calcites deposited on fault planes during the neotectonic events in
southwest Turkey. The samples will also be used for multi-isotope analysis
using radiogenic (He, Sr and Nd) and stable (O and C) isotopes to constrain
the role of mantle fluids in crustal environments and travertine formation.
The successful candidate will explore the application of the U-series dating
of carbonate deposits from seismically active areas to provide important
temporal information relevant to establishing recurrence intervals of late
Quaternary and prehistoric major earthquake events.  Precise dating of
prehistoric earthquakes will be of great value for seismic hazard studies
and earthquake forecasting research, for which accurate estimates of
recurrence intervals are critical.



Project 3: Multiple sulfur isotopes in Archaean hydrothermal systems as
tracers of the origin of ancient microbial metabolisms, jointly supervised
by Golding and Huston (GSA)



Stable isotope geochemistry has played a major role in our current
understanding of the sulfur and carbon cycles and the surface environment of
the Earth from the Archean to the present. The recent recognition of mass
independent sulfur isotope fractionation in Archaean and early Proterozoic
rocks has reinvigorated sulfur isotope geochemistry and provided an
unprecedented new tracer of the source of sulfur and impact of various
sulfur metabolisms in ancient sedimentary and hydrothermal environments.
Furthermore the timing of the origins of various microbial metabolisms is
poorly resolved with differing interpretations of the evolutionary
relationships between different prokaryote groups, which have important
implications for interpretation of the Archaean rock record and early Earth
biogeochemical cycles.

         This project will use multiple sulfur isotope records in ancient
hydrothermal systems to establish the timing of origination of various
microbial metabolisms and their role in the Archaean sulfur cycle. It will
test the hypothesis that sulfate reducers, particularly mesophilic lineages
had not yet evolved so the early Archaean sulfur cycle was dominated by
inorganic, hydrothermal and atmospheric processes with a possible role for
microbial sulfur reduction. The main focus of your study will be Archaean
volcanic-hosted massive sulfide (VHMS) mineral systems because their
paleohydrology and ages of formation are relatively well constrained.
Seafloor hydrothermal mineralisation is ultimately the result of high heat
flow which drives sub-seafloor convective circulation of seawater.  Deposits
are formed by precipitation of sulfides, oxides and native metals on or
immediately beneath the seafloor.  The identification of mass independent
sulfur isotope fractionation in a pilot study of samples from several
Archaean hydrothermal systems in Western Australia has established the
efficacy of our approach. A secondary outcome of the project will be a
greatly enhanced understanding of the fluid and metal sources for Archaean
VHMS deposits with implications for ore deposit models and deposit
targeting.



Background of candidates:


We are seeking highly motivated and enthusiastic students with a background
in Quaternary science, geography, geochemistry, structural geology or
similar (Projects 1 and 2) or Archaean geology, economic geology,
geochemistry, geomicrobiology or similar (Project 3). Other projects in the
areas of our research strengths will be outlined by staff during the
Postgraduate Recruitment Day Program. In all cases a first class honours
degree or research masters in a relevant field is required.



Applications and closing dates for international (IPRS) and local (APA)
scholarships:


Interested applicants should submit an application for a graduate
scholarship to UQ. The deadline for receipt of IPRS applications from
international students is 31st August 2005; for APA/UQ scholarships for
Australian and New Zealand students the deadline is 31st October 2005. The
successful candidate will be expected to commence between 2nd Jan and 31st
Mar 2006. Application forms and relevant information for both international
(IPRS) and local (APA) scholarships are available at
http://www.uq.edu.au/grad-school/index.html?page=9778&pid=9258.



For further information on potential PhD projects, please contact:

Drs Sue Golding (s.golding at earth.uq.edu.au), Jian-xin Zhao
(j.zhao at uq.edu.au), and Tonguc Uysal (t.uysal at earth.uq.edu.au)



 In addition, please come to:

Postgraduate Recruitment and Information Day
Earth Sciences
School of Physical Sciences, University of Queensland.

Thursday/Friday 22nd/23rd September, 2005

      Application form

      www.earth.uq.edu.au/DES_Research/DES_PG_InfoDay2005.html

      The closing date has been extended to September 16, 2005.













A/Prof. Sue Golding,

Postgraduate Coordinator

School of Physical Sciences

University of Queensland

Brisbane, QLD 4072

Ph. 07-3365 1159



Jian-xin Zhao
Principal Research Fellow
School of Physical Sciences
University of Queensland
Brisbane, Qld 4072

Ph. (07) 3346 9754 (W), (07) 3411 4369 (H)
Fax (07) 3365 8530 (W)
Mobile 0410683866
Email: j.zhao at uq.edu.au