The rigid and rocky continental crust is a striking feature of the our planet billions of years ago. To try to calculate the your age, researchers generally study decomposition of chemical substances trapped in rocks. Usually carbonate or limestone rocks recovered from the ocean, which consist of: 'calcite' (calcium carbonate) and / or 'dolomite' (calcium and magnesium carbonate).
However, these minerals are difficult to find in conditions that are pure enough to be analyzed. Thinking about it, one team of scientists developed a new way to date the pieces of the earth's crust. Research that was presented last Monday (26) at the European Union's Geosciences virtual conference showed that when analyzing a mineral called 'barite' (a combination of ocean salts and barium released by volcanic openings in the ocean), scientists found evidence that the age of the continents was misjudged by previous estimates.
Barite minerals form at the bottom of the sea, where hot, nutrient-rich water emanates from hydrothermal vents. According to the researchers, there is an intimate relationship between marine rocks and studies of the continental crust, since the continents and oceans have a long history of nutrient exchange.
Desiree Roerdink, a geochemist at the University of Bergen in Norway, says that a piece of barite, which has been on the planet for at least three and a half billion years, is a “great recorder” for observe the processes that occurred on Earth.
Wear of continents and barite deposits
As continents “wear out” naturally over time, they spill nutrients into the oceans. These nutrients help to promote marine life.
One of the elements that “leaks” from land to the sea is strontium (chemical element with the symbol 'Mr.'), an alkaline earth metal abundant in nature. By measuring the proportion of strontium in six different deposits of barite, the researchers were able to calculate the age of these minerals, which ranged from 3,2 to 3,5 billion years. From there, the team was able to deduce how long ago the ancient continents began to send strontium to the oceans.
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The team concluded that the Earth already had continents formed 3,7 billion years ago. In practice, half a billion earlier than previously estimated by studies based on carbonate minerals. In the end, in addition to indicating that the continents are much older than previously thought, the study also points out that the processes that “created” them, such as tectonic plates, for example, were also active since then.