Geologists show British mainland was formed by ancient three-way collision

For hundreds of years, scientists believed that the modern-day British mainland was formed by the collision of two ancient land masses, Avalonia and Laurentia. However, a new study partially supported by the EU-funded OS.EARTH project suggests that a third continental land mass, Armorica, was also involved in the process. The findings were published in the ‘Nature Communications’ journal.

According to a news article posted on the University of Plymouth website, the scientists believe the research provides a fresh perspective on Great Britain’s formation. Lead author Dr Arjan H. Dijkstra said: “It has always been presumed that the border of Avalonia and Armorica was beneath what would seem to be the natural boundary of the English Channel. But our findings suggest that although there is no physical line on the surface, there is a clear geological boundary which separates Cornwall and south Devon from the rest of the UK.”

Connection between England and France

The researchers examined rock samples from 22 locations in south-west Britain – Devon and Cornwall – that were left exposed following geological events such as underground volcanic eruptions. As noted in the news article, these took place around 300 million years ago and brought magma from depths of 100 km to the earth’s surface. Through a detailed process that involved X-ray fluorescence spectrometry as well as isotopic analysis, the scientists examined the levels of two elements in the rock samples, strontium and neodymium.

The findings were later compared with previous studies elsewhere in the United Kingdom and mainland Europe. These showed that there is a clear boundary, or suture, running from the south coast of Devon to Cornwall in the west. The study revealed that areas north of this boundary appear to share their geological roots with the rest of England and Wales, while everything south seems to be geologically linked to France and mainland Europe. A video in the same news article highlights the abundance of tin and tungsten in south-west England. These are metals also found in Brittany and other areas of mainland Europe, but not so evident elsewhere in the United Kingdom. “We always knew that around 10,000 years ago you would have been able to walk from England to France,” Dr Dijkstra added. “But our findings show that millions of years before that, the bonds between the two countries would have been even stronger. It explains the immense mineral wealth of South West England, which had previously been something of a mystery, and provides a fascinating new insight into the geological history of the UK.”

The OS.EARTH (Osmium alloys & the pulse of the Earth) project ran between 2011 and 2015. It studied “the vital clues about the large-scale melting events in the history of the Earth that are preserved within the mantle in the form of tiny grains of alloys of the element osmium (Os),” according to CORDIS. During the project, a new methodology for fast automated mineralogy analysis was used with the help of scanning electron microscopy.

For more information, please see:
project on CORDIS