From Curtin University (AU): Conflicting stores from one university:: “Study shows Earth’s ancient water cycle was key to making continents” vs “Evidence that giant meteorite impacts created the continents” 

From Curtin University (AU)

The first story:

Greta Carlshausen
Media Officer
Tel: +61 8 9266 3549
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greta.carlshausen@curtin.edu.au

Vanessa Beasley
Deputy Director
Tel: +61 8 9266 1811
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vanessa.beasley@curtin.edu.au

A new Curtin University study has found that water was transported much deeper in the early Earth than previously thought, shedding new light on how the continents were originally formed.

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The study, published in Earth and Planetary Science Letters [below], answers long-standing questions about the early Earth water cycle.

Lead researcher Dr Michael Hartnady, from the Curtin School of Earth and Planetary Sciences, said how water is stored and transported through Earth’s crust influences everything, from where volcanoes and mineral deposits form to where earthquakes occur.

“Although we understand the modern deep-water cycle, we know very little about how it worked when Earth was still a very young planet,” Dr Hartnady said.

“Multiple lines of geological evidence show that water was transported to great depths within Earth all the way back to 3.5 billion years ago, although it is not well understood how exactly it got there.”

Researchers used sophisticated modelling to show that primitive high-magnesium volcanic rocks – that erupted onto the ocean floor in the early Earth – would have soaked up much more seawater than more modern lavas.

“This water, which is locked into particular crystals within the rock, would have been released as the rocks were buried and began to ‘sweat’. In modern lavas, this sweating happens at a temperature of about 500 degrees Celsius,” Dr Hartnady said.

“Our findings indicate that much of the seawater initially bound within the ancient primitive lavas would have been released at much higher temperatures, greater than 700 degrees Celsius.

“Importantly, this means that the water was transported much deeper into the early Earth than previously thought. Its release would have caused surrounding rocks to melt ultimately to form the continents.”

Dr Hartnady said this research helped to explain the inner workings of the planet from more than 2.5 billion years ago.

“Interestingly, the oldest parts of the continents, the cratons, also contain some of the largest gold deposits on Earth including the Golden Mile near Kalgoorlie,” Dr Hartnady said.

“These gold deposits required huge volumes of water to form, and we still don’t have a good explanation for where it came from. Our new research may help solve these and other questions, perhaps even those related to the origins of life.”

This research was funded by the Australian Research Council, Geological Survey of Western Australia and Northern Star Resources Ltd.

The second story:

Evidence that giant meteorite impacts created the continents

New Curtin research has provided the strongest evidence yet that Earth’s continents were formed by giant meteorite impacts that were particularly prevalent during the first billion years or so of our planet’s four-and-a-half-billion year history.

Dr Tim Johnson from Curtin’s School of Earth and Planetary Sciences said the idea that the continents originally formed at sites of giant meteorite impacts had been around for decades, but until now there was little solid evidence to support the theory.

“By examining tiny crystals of the mineral zircon in rocks from the Pilbara Craton in Western Australia, which represents Earth’s best-preserved remnant of ancient crust, we found evidence of these giant meteorite impacts,” Dr Johnson said.

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A gorge at Karijini National Park shows off the rocks of the Pilbara craton. Credit: iStock

“Studying the composition of oxygen isotopes in these zircon crystals revealed a ‘top-down’ process starting with the melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.

“Our research provides the first solid evidence that the processes that ultimately formed the continents began with giant meteorite impacts, similar to those responsible for the extinction of the dinosaurs, but which occurred billions of years earlier.”

Dr Johnson said understanding the formation and ongoing evolution of the Earth’s continents was crucial given that these landmasses host the majority of Earth’s biomass, all humans and almost all of the planet’s important mineral deposits.

“Not least, the continents host critical metals such as lithium, tin and nickel, commodities that are essential to the emerging green technologies needed to fulfill our obligation to mitigate climate change,” Dr Johnson said.

“These mineral deposits are the end result of a process known as crustal differentiation, which began with the formation of the earliest landmasses, of which the Pilbara Craton is just one of many.

“Data related to other areas of ancient continental crust on Earth appears to show patterns similar to those recognised in Western Australia. We would like to test our findings on these ancient rocks to see if, as we suspect, our model is more widely applicable.”

Dr Johnson is affiliated with The Institute for Geoscience Research (TIGeR), Curtin’s flagship earth sciences research institute.

Take your pick.

Science papers:
First story
Earth and Planetary Science Letters

Second story
Nature

See the First story full article here .

See the Second story full article here.

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Curtin University (AU) is an Australian public research university based in Bentley and Perth, Western Australia. The university is named after the 14th Prime Minister of Australia, John Curtin, and is the largest university in Western Australia, with over 58,000 students (as of 2016).

Curtin would like to pay respect to the indigenous members of our community by acknowledging the traditional owners of the land on which the Perth campus is located, the Wadjuk people of the Nyungar Nation; and on our Kalgoorlie campus, the Wongutha people of the North-Eastern Goldfields.

Curtin was conferred university status after legislation was passed by the Parliament of Western Australia in 1986. Since then, the university has been expanding its presence and has campuses in Singapore, Malaysia, Dubai and Mauritius. It has ties with 90 exchange universities in 20 countries. The University comprises five main faculties with over 95 specialists centres. The University formerly had a Sydney campus between 2005 & 2016. On 17 September 2015, Curtin University Council made a decision to close its Sydney campus by early 2017.

Curtin University is a member of Australian Technology Network (ATN), and is active in research in a range of academic and practical fields, including Resources and Energy (e.g., petroleum gas), Information and Communication, Health, Ageing and Well-being (Public Health), Communities and Changing Environments, Growth and Prosperity and Creative Writing.

It is the only Western Australian university to produce a PhD recipient of the AINSE gold medal, which is the highest recognition for PhD-level research excellence in Australia and New Zealand.

Curtin has become active in research and partnerships overseas, particularly in mainland China. It is involved in a number of business, management, and research projects, particularly in supercomputing, where the university participates in a tri-continental array with nodes in Perth, Beijing, and Edinburgh. Western Australia has become an important exporter of minerals, petroleum and natural gas. The Chinese Premier Wen Jiabao visited the Woodside-funded hydrocarbon research facility during his visit to Australia in 2005.