There is a new exciting opportunity for a 2 year post-doctoral position (2018-2020) at the Centre for Exploration Targeting, School of Earth Sciences, UWA.
Please see the information regarding to the project in the link below:
A Terrestrial Hot Spring Setting for the Origin of Life? Darwin’s Warm Little Pond revisited
For more information please contact Marco Fiorentini
Description of the position
The post-doc will analyse sulphides, trace metals, and PGE in fresh drillcore materials collected previously as well as work in close collaboration with staff, PhD students and Honours students between UWA and UNSW to analyse the geochemistry of hydrothermally altered basalts to generate element mobilisation maps showing the transfer and concentration of elements.
Analyse Li and B isotopes of fresh and hydrothermally altered basaltic rocks to determine the amount of chemical alteration and/or surficial weathering. Specifically, the proposed project offered at UWA will have three key modules:
1) In situ, high precision compositional analysis of pyrites from Dresser hydrothermal veins and pyrite-replaced stromatolites, to test whether early life utilised and concentrated biologically available trace metals (e.g., Zn, Ni, Mo, Mn), using EDS and the NanoMin facility at Macquarie University. Together with detailed documentation of the macroscopic textural and mineralogical features that make up the various sinters associated with Dresser hot spring facies, we aim to unravel their cryptic chemical nature;
2) In situ, high precision compositional analysis of gold and the Platinum Group Elements to determine their role as catalysts to first life. While it is known that some metals such as Zn, Mo and Ni may have acted as catalysts to first life, it is presently unknown whether other elements with similar electronic configurations may also have played a significant role. The highly siderophile and chalcophile ultra-trace metals gold (Au) and the platinum-group elements (PGE: Os, Ir, Ru, Rh, Pt, Pd), which are transported in hydrothermal fluids as bisulfide and/or trisulfide complexes59,60
, are generally enriched in some hot spring systems (e.g., Champagne Pool, NZ). However, while most studies have investigated the precious metal budget of hot springs to better constrain ore forming processes, we shift focus and address the hypothesis of whether Au and PGE have played a key role in the origin of life. For example, some metallophilic bacteria such as Cupriavidus metallidurans and Delftia acidovorans, are able to turn gold-chloride (a toxic complex commonly found in nature) into 99.9% metallic gold61
. The PGE have long been neglected in the study of bacterial metabolism, but most recent studies have found intriguing evidence for the dependency of certain metallophilic proteobacteria on platinum62
. This finding is notable as ancient protoebacteria could have been ancestral to mitochondrial evolution in eukaryotes63
. So, the question is whether the patchy Au- and PGE-rich crust of our primordial planet, which had literally been sprinkled with base and precious metals by meteoritic bombardment64
, contributed to the creation of complex environments that may have facilitated the onset of life.
We will determine the Au and PGE abundance of Dresser hot spring deposits, as preserved in the unweathered samples from the 2004 PDP drillcores20
. Specifically, we will test for Pd, which is known to be mobile at relatively low temperatures in hydrothermal fluids. Is the average background anomalous? Is the detectable distribution homogenously or heterogeneously laid out and does it vary with alteration geochemistry and mineralogy (ie fluid, temperature)? What are the ratios of the various metals? Analyses will be undertaken using the recent analytical advances in the detection of low level (parts per trillion) Au and PGE concentrations through both wet chemistry dissolution and analysis of felsic rocks65
, and in-situ investigation of few-micron-size mineral phases;66
3) Multiple sulfur isotopes. In addition to tracking the presence of potential trace metal catalysts, we aim to utilize multiple sulfur isotope analysis to fingerprint the hydrothermal processes that may account for their transportation and biogenic fixation in ancient hot spring systems. In hydrothermal fluids, PGE and Au are commonly transported as bisulfide and/or trisulfide complexes. Advances in the in-situ analysis of multiple sulfur isotopes in sulfides67
allow for the first time to investigate the cryptic link between metallogeny and the sulfur cycle. Specifically, in this study we seek to map the key link between chemical variability and multiple sulfur analysis in the sulfide-bearing lithologies that make up the Dresser Formation, with the objective of 1) constraining key processes that may have generated the observed chemical and isotopic patterns, and 2) refining the understanding of the Archaean sulfur cycle and its role in the evolution of early Earth’s climate and biosphere.
The interpretation of sulfur behaviour in geological fluids and melts is based on a long-standing paradigm that sulfate, sulfide, and sulfur dioxide are the major sulfur compounds. This paradigm was recently challenged by the discovery of the trisulfur ion in aqueous S-bearing fluids from laboratory experiments at elevated temperatures. Although the potential prevalence of this important sulfur species remains insufficiently quantified at hydrothermal conditions, this ion may account for up to 10% of total sulfur (Stot
) dissolved in hydrothermal fluids at 300–500 °C, and more than 50% (Stot
) at 600–700 °C in S-rich fluids produced via prograde metamorphism of pyrite-bearing rocks. The trisulfur ion may favour the mobility of sulfur itself and associated metals (Au, Cu, Pt, Mo) in geological fluids over a large range of depth and provide the source of these elements for orogenic Au and porphyry-epithermal Cu–Au–Mo deposits. Hence, in the framework of this Project, we aim to unravel the multiple sulfur isotope architecture of the Dresser Formation to unlock its significance in terms of the nature of metal transport mechanisms