WOMEESA Webinar notes; The Brilliant Billion in Earth’s History-life & mineral deposits.

On the 7th April 2021 Women in Earth and Environmental Sciences in Australia [WOMEESA] held a webinar “The Brilliant Billion in Earth’s history – life and mineral deposits” by Indrani Mukherjee.

The concept of WOMEESA is to Create a unified Australasian network of women working in Earth and Environmental Sciences in academia, industry and government, and was launched in March 2018. https://www.womeesa.net/  Indrani Mukherjee is a postdoctoral research fellow in Geochemistry at the University of Tasmania, and works with the ARC Centre of Excellence in Ore Deposits [CODES]. Indrani has published a number of papers in Ore Geology Reviews, Elsevier and others.  https://www.utas.edu.au/profiles/staff/earth-sciences/indrani-mukherjee This presentation combined two major research aspects, that of application of pyrite geochemistry to ocean-atmosphere redox evolution, and application of pyrite to exploration. The presentation was accompanied by excellent and engaging slides that reflect her passion for this subject. The easy to listen to webinar was held in English with about 50 in attendance.

The bases of this science are that when rocks weather and wash out into the oceans, microbe life take up the elements as nutrients, that on death, are entrapped in sedimentary pyrite in black shales.  A LA-ICP-MS Laser Ablation-Inductively Coupled Plasma-Mass spectrometer is able to examine the trace elements in sedimentary pyrite. The abundance of a range of trace elements reflects the nutrient take up of micro bugs and so reflects upon the evolution of life in the “Boring Billion” years of earth’s history from about 1.8 to 0.8 billion years ago. These simple organisms are the precursor of more complex of life built on complex multi cell structures that we are more familiar with. This early life may have played a role in developing earths atmospheric oxygen. Patterns of trace elements over time suggest there was a period of low nutrients that may have forced evolution change, followed by a period of abundant trace elements allowing for growth and divergence. This work also opens the door on how our complex cells evolved.

Trace elements in sedimentary pyrite is being studied to look for zonation’s, such as outlined in the paper “Application of pyrite trace element geochemistry to exploration for SEDEX style Zn-Pb deposits: Mc Arthur Basin, Northern Territory, Australia 2017”