For years, magnetic maps of East Antarctica have shown something strange about the region from Princess Elizabeth Land: a large amplitude linear magnetic anomaly under kilometers of ice that runs along the coast parallel to the margin of the continent. It was something that satellites and planes could detect, but no one knew exactly what rock was producing it until now.
Discovering it. If the problem is that this anomaly was under a large amount of ice, a team of researchers within the framework of a Russian-Chinese cooperation He has done the most logical thing to find what was happening: start drilling.
What they have found after putting a large drill to work is not only a magnetic rock that gave that peculiar pattern, but it is the geological “scar” of an ancient island arc that collided with the continent almost 1,000 years ago, when the supercontinent was forming. Rodinia.
A challenge. The study that includes this discovery focuses mainly on the Rayner tectonic province, an area that is geologically critical because it is considered a “mobile belt.” That is, it is a collision zone where ancient blocks of crust were crushed against each other.
The problem with Antarctic geology is that almost everything they are interested in is buried, and in this case the team had to cross 541 meters of ice to be able to reach the rock that interested them.
What did they find? What they took from the bottom of Antarctica was not common granite as can occur in other areas, but rather the core recovered is a mafic granulite. Something that is very important, since granulites are metamorphic rocks that have suffered infernal temperatures and pressures.
After power analyze this rock So interesting, it was seen that this was what was causing the linear anomalies seen from space. And as we say, it is not a very normal stone, since it is rich in ferromagnetic minerals, capable of altering the magnetic field locally.
Investigating Rodinia. Once with the sample in hand, the team applied geochemistry techniques and dating to be able to counterbalance these data with everything that was known in previous research. What was seen is that there was a great violent history behind it, since it was known that the rock was originally born as magma about 970 million years ago.
From its birth, that rock was pushed into the depths and “cooked.” The data indicate that it was subjected to temperatures between 650 and 790 ºC and pressures equivalent to depths of 15 to 18 kilometers. In this way, the researchers’ conclusion is that this rock was part of a volcanic arc of islands like those of Japan. But the most interesting thing is that this arc was not originally in Antarctica, but was forcibly “stuck” against the ancient continent during a massive collision that gave rise to the formation of Rodinia.
The Indian connection. To understand the magnitude of the find, you have to look beyond Antarctica, as geologists have long suspected that the Rayner Province in Antarctica and the Eastern Ghats Province in India They are twins separated at birth.
And the new data reinforces this theory, since the conditions of “high temperature” metamorphism found in this drilling are almost identical to those documented in India. This leads us to conclude that 900 million years ago, the east coast of India and this part of Antarctica were joined, forming a huge mountain range created by the collision of tectonic plates.
Images | 66 north
In Xataka | In the United States there is an incredible river that does what seems impossible: defy the laws of gravity
GIPHY App Key not set. Please check settings