Zircon crystals reveal onset of plate tectonics

May 31, 2012
Zircon crystals reveal onset of plate tectonics

(Phys.org) -- We're familiar with the theory that the Earth's crust is composed of tectonic plates that move, sometimes dramatically to create earthquakes and tsunamis - but until recently, nobody knew how long this movement has been going on.

An international team of researchers, including Dr. Anthony Kemp from The University of Western Australia, believes they have found out and their work is published in Nature today.

Dr. Kemp, an Australian Research Council Future Fellow in UWA's School of Earth and Environment, said as far as we know, Earth is the only planet in the with active .

"The purpose of this study was to examine the earliest rock record to find out when plate tectonics started and when the began to form," he said.

"We analyzed zircon crystals from of Greenland.  These rocks included some of the oldest and best-preserved parts of the Earth's crust and were between 2.85 and 3.9 billion years old.

"In much the same way that tree rings record the growth of a tree, zircons provide important insights into the nature and composition of the magma (molten material deep within the Earth's crust) from which the zircon crystallised."

The researchers analyzed the isotopes of oxygen and hafnium in the zircon to learn more about the crystals' growth bands and discovered that the Greenland crust had evolved in two stages.  The first involved a simple re-melting of 3.9 billion year-old rocks, followed by a second more complex period after about 3.2 billion years ago involving more diverse magma sources associated with re-melting and the formation of new continental material.

"We attribute this transition to the onset of plate tectonics at approximately 3.2 billion years ago and infer that significant volumes of crust began to be stabilized as continents only after that time," Dr. Kemp said.

"We're now trying to verify and extend these findings by studying rocks from the Pilbara, which span the same key time period from 2.8 to 3.6 billion years ago.  A broader aim is to identify the triggers for plate tectonics.

"High-precision isotope measurements will be done at the Advanced Geochemistry and Mass Spectrometry Facility recently established at UWA by Winthrop Professor Malcolm McCulloch."

The project was led by Dr. Tomas Naeraa from the Geological Survey of Denmark and , and also involved researchers from Sweden and Germany.

Explore further: Radioisotope studies show the continental crust formed 3 billion years ago

Related Stories

Bias in the rock record?

Jan 14, 2009

(PhysOrg.com) -- The fossil record is known to be biased by the unevenness of geographical and stratigraphical sampling, and the lack of exposed rocks containing fossils. In a recent Perspective in Science [2 Jan ...

Younger, hotter Earth still not understood

Sep 13, 2010

Plate tectonics may not have operated on a younger and hotter Earth according to new research from the University of Bristol carried out on preserved remnants of ancient continental crust in the Hudson Bay ...

Study reveals ancient rocks linked to old Earth's crust

Feb 24, 2010

(PhysOrg.com) -- A new geological study which took place in the Pilbara region of Western Australia brings us one step closer to understanding more precisely the timing of when the primordial earth crust was ...

A new theory on the formation of the oldest continents

Mar 12, 2012

German geologists from the Universities of Bonn and Cologne have demonstrated new scientific results in the April issue of the scholarly journal Geology, which provide a new theory on the earliest phase of continental format ...

Recommended for you

ESA image: Northwest Sardinia

19 hours ago

This image over part of the Italian island of Sardinia comes from the very first acquisition by the Sentinel-2A satellite.

Experiments open window on landscape formation

Jul 02, 2015

University of Oregon geologists have seen ridges and valleys form in real time and—even though the work was a fast-forwarded operation done in a laboratory setting—they now have an idea of how climate ...

NASA image: Canadian wildfires continue

Jul 02, 2015

Canada is reeling from an early fire season this year as dozens of fires ravage at least three provinces of the country. All of the following reports are as of July 2, 2015.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.