Tag Archives: geology

geochemistry

Curtin home to new geochemistry equipment that unlocks geochemical secrets

AuScope supports the purchase, upgrade and maintenance of geochemical research infrastructure at Curtin and has recently received $5 million in Federal Government funding. The investment will be used on a new replacement Sensitive High-Resolution Ion Microprobe (SHRIMP) age-dating geochemistry instrument, which will be installed at the John de Laeter Research Centre at the University’s Bentley Campus.

Funded through the National Collaborative Research Infrastructure Strategy, the new SHRIMP will enable continued geochemistry research and innovation at the world-leading zircon geochronology facility at the centre.

Curtin University Vice-Chancellor Professor Deborah Terry congratulated the John de Laeter Research Centre team for presenting a strong case for funding to upgrade the existing 25-year-old SHRIMP.

“A quarter of a century ago, Professor John de Laeter led a proposal to commission a new SHRIMP ion microprobe at Curtin, which would subsequently bring about new understandings of the Australian continent, the Earth’s tectonic plates and the age of the Solar System, among other breakthroughs,” Professor Terry said.

“This new SHRIMP instrument will enable the continuation of the important research that has been demonstrated over many years as having tremendous benefit to government, industry and academia.

“The funding allows our researchers to remain working at the forefront of a science that shapes our collective understanding of the Earth and its place in the Universe.”

John de Laeter Research Centre Director Professor Brent McInnes said the SHRIMP instrument had played a huge role in the advancement of geoscience and geochemistry research in Australia and around the globe, enabling new scientific discoveries and reshaping the geological map of Australia.

“The new funding will allow industry, government and academic researchers to undertake new Earth and planetary research, such as those related to deep drilling projects and asteroid sample return missions,” Professor McInnes said.

The John de Laeter Research Centre has strong links with the Geological Survey of Western Australia and Geoscience Australia, and provides geochemistry, geochronology and isotope geoscience data critical to their missions of mapping and understanding the Australian continent and its resources.

AuScope’s SHRIMP instrument forms part of the Earth Composition and Evolution infrastructure  located at Curtin University, The University of Melbourne and Macquarie University.

This article was originally published by Curtin University.

Continents collide

Continents collide

Collecting rock samples at 5200 m on a recent trip to the Tibetan Plateau, Professor Simon Wilde, from the Department of Applied Geology at Curtin University, was pleased to have avoided the symptoms of altitude sickness. The last time he conducted fieldwork in a similar environment had been about 20 years before in Kyrgyzstan, Central Asia, and he’d managed then to also avoid altitude headaches. Nonetheless, he says, Tibet was tough. Due to the atmospheric conditions, the Sun was intensely strong and hot but the ground was frozen. “It’s a strange environment,” he says.

Wilde was invited by scientists at the Guangzhou Institute of Geochemistry, part of the Chinese Academy of Sciences, to collect volcanic rock samples at the Tibetan site. The region is geologically significant because it is where the Indian tectonic plate is currently “driving itself under the Eurasian plate”, he explains. During their recent field trip, Wilde and his Chinese colleagues collected about 100 kg of rocks, which were couriered back to Guangzhou and Curtin for study. The researchers will be drawing on a variety of geochemistry techniques to analyse the material as they try to paint a picture of what happens when two continents collide, gaining insight into the evolution of Earth’s crust.

“We’re trying to unravel a mystery in a sense,” says Wilde. “We don’t have the full information, so we’re trying to use everything we can to build up the most likely story.”

The Guangzhou geochemists will be analysing trace elements in the rock samples to uncover information about their origins and formation. Back at Curtin, Wilde is working on determining the age of zircon crystals collected from the site, using a technique called isotopic analysis. This involves measuring the ratios of atoms of certain elements with different numbers of neutrons (isotopes) to reveal the age of crystals based on known rates of radioactive decay.

It’s work that’s providing a clearer picture of Earth’s early crustal development and is an area in which Wilde is internationally renowned (see profile, p18).

Gaining an idea of the past distribution of Earth’s continental crust has implications for the resources sector, Wilde explains. “It’s important for people working in metallogeny [the study of mineral deposits] to see where pieces of the crust have perhaps broken off and been redistributed,” he says. “There could be continuation of a mineral belt totally removed and on another continent.”


Continents collide: Copper in demand

Professor Brent McInnes, Director of the John De Laeter Centre for Isotope Research, is also interested in the collision of tectonic plates – to help supply China’s increasing demand for domestic copper. “The rapid urbanisation of China since the 1990s has created a significant demand for a strategic supply of domestic copper, used in air conditioners, electrical motors and in building construction,” explains McInnes. Most of the world’s supply of copper comes from a specific mineral deposit type known as porphyry systems, which are the exposed roots of volcanoes formed during tectonic plate collisions.

McInnes’ research involves taking samples from drill cores, rock outcrops and mine exposures in mountainous regions around the world to be studied back in the lab. Specifically, he and his research team are able to elucidate information about the depth, erosion and uplift rate of copper deposits using a technique called thermochronology – a form of dating that takes into account the ‘closure temperature’, or temperature below which an isotope is locked into a mineral. Using this information, scientists can reveal the temperature of an ore body at a given time in its geological history. This, in turn, provides information with important implications for copper exploration, such as the timing and duration of the mineralisation process, as well as the rate of exposure and erosion.

“Institutions such as the Chinese Academy of Sciences have been awarded large research grants to investigate porphyry copper deposits in mountainous terrains in southern and western China, and have sought to form collaborations with world-leading researchers in the field,” says McInnes.

“We’re trying to unravel a mystery, in a sense. We don’t have the full information, so we’re trying to use everything we can to build up the most likely story.”


Continents collide: Interpreting species loss

Professor Kliti Grice, founding Director of the WA-Organic and Isotope Geochemistry Centre, researches mass extinctions. As an organic and isotope geochemist, Grice (see profile, p12) studies molecular fossils in rock sediments from 2.3 billion years ago through to the present day, also known as biomarkers. These contain carbon, oxygen, hydrogen, nitrogen, or sulphur – unlike the rocks, minerals and trace elements studied by inorganic geochemists Wilde and McInnes.

Grice uses tools such as tandem mass spectrometry, which enables the separation and analysis of ratios of naturally occurring stable isotopes to reconstruct ancient environments. For example, carbon has two stable isotopes – carbon-12 and carbon-13 – and one radioactive isotope, carbon-14. The latter is commonly used for dating ancient artefacts based on its rate of decay. A change in carbon-12 to carbon-13 ratios in plant molecules, however – along with a change in hydrogen – can reveal a shift in past photosynthetic activity.

Grice has uncovered the environmental conditions during Earth’s five mass extinction events and has found there were similar conditions in the three biggest extinctions – the end-Permian at 252 million years ago (Ma), end-Triassic at 201 Ma and end-Devonian at 374 Ma. Among other things, there were toxic levels of hydrogen sulphide in the oceans. Grice discovered this by studying molecules from photosynthetic bacteria, which were found to be using toxic hydrogen sulphide instead of water as an electron donor when performing photosynthesis, thereby producing sulphur instead of oxygen.

“The end-Permian and end-Triassic events were almost identical in that they are both associated with massive volcanism, rising sea levels and increased run-off from land, leading to eutrophication,” Grice explains. Eutrophication occurs when introduced nutrients in water cause excessive algal growth, reducing oxygen levels in the environment. “There were no polar ice caps at these times, and the oceans had sluggish circulations,” she adds.

In 2013, Grice co-authored a paper in Nature Scientific Reports documenting that fossils in the Kimberley showed that hydrogen sulphide plays a pivotal role in soft tissue preservation. This modern day insight is valuable for the resources sector because these ancient environments provided the conditions for many major mineral and petroleum systems. “When you have these major extinction events associated with low oxygen allowing the organic matter to be preserved – along with certain temperature and pressure conditions over time – the materials break down to produce oil and gas,” Grice says.

For example, the Permian-Triassic extinction event – during which up to 95% of marine and 70% of terrestrial species disappeared – produced several major petroleum reserves. That includes deposits in Western Australia’s Perth Basin, says Grice, “and probably intervals in the WA North West Shelf yet to be discovered.”

Gemma Chilton

mass extinction

Molecular detective studies mass extinction events

When the Earth warmed and the oceans turned toxic with hydrogen sulfide about 250 million years ago, up to 95% of marine life and 70% of terrestrial species were wiped out – the largest of five mass extinction events in Earth’s history. Much of what we know about these is thanks to research by John Curtin Distinguished Professor Kliti Grice – organic and isotope geochemist and founder of Curtin’s WA-Organic and Isotope Geochemistry Centre within the Institute for Geoscience Research and the John De Laeter Centre for Isotope Research. Grice studies the molecular signatures of chemicals that have been made by micro-organisms, plants and animals, and deposited in lakes and oceans, thousands or even hundreds of millions of years ago.

Her work requires a deep knowledge of biochemical pathways, geology, chemistry, ecology, stable isotopes within organic molecules, and cutting edge analytical techniques in order to interpret clues left behind in rocks and determine which organisms lived in certain aquatic regions and when.

“I look at everything from about 2.3 billion years ago, through to the present day, including recovery after the mass extinction events,” she says. “Most people know about the dinosaur mass extinction, which was unique because it was due to a meteorite impact,” she says. But the other mass extinctions were caused by changes in the atmosphere and oceans.

Grice is working on the Triassic-Jurassic extinction, which occurred about 200 million years ago when supercontinent Pangaea began to break up. “There was a lot of carbon dioxide and flood basalts from volcanic eruptions. We established that the same conditions existed in the oceans then as they did in the largest mass extinction event 50 million years earlier,” she says. These events were biochemically driven, with environmental events leading to high carbon dioxide and hydrogen sulfide in bodies of water.

Grice’s research is also relevant to petroleum and mineral exploration, as well as to modern day climate and environmental changes. “We work with people across disciplines including geologists, engineers, mathematicians, biologists and geographers,” she says.

Grice is passionate about working with PhD students and early and mid-career scientists and helping them develop. “I like sharing my enthusiasm and ideas – seeing young scientists grow, helping them with their research and providing opportunities, including visits to different parts of the globe.”

Michelle Wheeler