Where East meets West: the geological crossroads of Iran and Afghanistan

In the earth sciences – and beyond – Iran and Afghanistan have a certain iconic status as largely inhospitable areas, rich in raw materials. But where does this remarkable geology come from? Researchers from the University of Central Asia and Utrecht University have now reconstructed the history of this 'geological Silk Road' in detail. "Culturally, the region lies at the crossroads of European, Central Asian, East Asian, Indian and Arab influences. Our reconstruction shows that the same is true geologically." Their results are published in the scientific journal Gondwana Research.

The researchers also included the Pamir Mountains, which forms the west side of the Tibetan Plateau, in their research. "The entire region, from the Pamirs to Iran, has a very complex geological history," explains Dr Nalan Lom, an earth scientist at the University of Central Asia in Khorog (Tajikistan) and formerly a researcher at Utrecht University, where she conducted the research into the geology of the area mentioned. "For some two hundred million years, this region has been kneaded as dough, as it were. Pieces of the earth's crust disappeared into the depths of the mantle, while other parts were scraped off, pushed up into mountains, and then stretched and squeezed again. And in these kinds of plate-tectonic highways the processes that form minerals and metal ores take place."

Chain collision

Co-author Douwe van Hinsbergen, Professor of Earth Sciences at Utrecht University, adds: "In this area, initially the blocks from Iran that broke away from Arabia 270 million years ago collided with Europe some 50 million years later. We then discovered that Afghanistan consists of an enormous piece of crust that was squeezed westward out of the Tibetan Plateau, into Iran. Once that was done, the whole area was compressed yet again by the collision with India."

Crescent

As if that wasn't enough, Arabia then collided with it from the southwest. "That latter collision is interesting,” Van Hinsbergen continues. “The Arabian continent collided first in northwestern Iran, while ocean crust from the Arabian plate kept subducting under Iran and Pakistan and kept pulling on the plate. As a result, Arabia rotated and tore away from Africa, which led to the formation of the Red Sea. In the collision zone near Iran, the Arabian continent was pushed down a bit, creating the Persian Gulf. And in the southeast, on the edge of the Arabian plate, there was a mountain range, which runs through Oman in a crescent. Where that mountain ledge is pushed down, a bend formed in the Persian Gulf. That is now the Strait of Hormuz. The  small islands in that strait are the peaks of the drowned mountain range."

Long-term history

Like Van Hinsbergen, Lom is particularly interested in the long-term history of mountain belts and the reconstruction of ancient tectonic systems. "We combed through decades of geological literature, looking for information on old fault systems, rotating pieces of crust, and the remains of former small oceanic basins that once existed in Iran. You wouldn't think so, but it once looked a bit like the western Mediterranean, with deep-sea basins between Afghanistan and western Iran. If Turkey and Greece would be pushed all the way against Spain, the first two would look like Afghanistan, and what is now Italy and Sardinia and Corsica would become something like present-day Iran." For this kind of reconstruction, it is important to peel back the entire history step by step. "Among other things, we use the advanced GPlates plate reconstruction software," adds Lom. "This software also came in very handy in the case of Iran, Afghanistan and the Pamir Mountains."

Major reconstructions

This research is part of a series of other large reconstructions led by Van Hinsbergen, such as those of the lost continents of Greater Adria and Argoland, and the lost megaplate Pontus. "Thanks to this kind of earth science puzzle work, we ultimately have a better understanding of how the current earth's surface came into being, or what our world looked like in the distant past. And that knowledge can help others in the search for natural resources, for example for the energy transition, but also to better understand earthquakes."