Geophysicists head to Hajar Mountains in search of black gold

A major research project to study the formation of the picturesque range is under way as it is one of the few places in the world where the dense oceanic crust and upper parts of the Earth's mantle are on top of the less dense continental crust.

A view of part of the Hajar Mountains in Wadi Ghalilah, north of Ras Al Khaimah, the UAE’s northern-most emirate,. Silvia Razgova / The National

RAS AL KHAIMAH // With their majestic peaks, the Hajar Mountains across the UAE and Oman are one of the region’s landscape highlights.

Running from the Musandam Peninsula down through the east coast of the Emirates and across the north of Oman, they offer a wonderful array of hiking trails, archaeological sites and photo opportunities.

Aside from their great value to adventure-seeking residents and tourists, the mountains have great geological significance.

What makes them of great interest to scientists is the way that the heavier oceanic crust has been pushed up over the lighter continental crust – a process that is still not fully understood.

Dr Simone Pilia, an Italian geophysicist in the UAE, said scientists understood “the overall picture”, but were still unsure how more dense oceanic crust and upper parts of the Earth’s mantle – the section between the core and crust – could be move to “less dense and more buoyant continental crust”.

“In most parts of the world, the oceanic crust is usually the one that goes beneath. In some cases and for reasons we don’t know, the oceanic crust goes up,” Dr Pilia said.

The material exposed over the top of the continental crust is known as ophiolite. This raised material usually contains igneous or volcanic rocks rich in iron and magnesium, and these can also be found in many major mountain ranges, such as the Himalayas, the Andes and the Swiss Alps.

Dr Pilia moved to the UAE last year to take part in a major research project into how the mountains have been formed.

He is a research associate at the Petroleum Institute in Abu Dhabi, a university and research centre that has teamed up with the Ministry of Energy and the UK’s University of Oxford to determine the structures associated with the UAE’s orogenic belt, where the crust has been pushed upwards to form mountains.

The area has been intensively studied, but much about the geology beneath the mountains is not understood.

The research will provide valuable information to oil and gas specialists searching for new supplies, and will help to train a new generation of geoscientists.

It could last up to four years, but results could be published in a major scientific journal much earlier.

About 700 kilometres long and up to 50km wide, the Hajar Mountains are said to be the biggest and best preserved “ophiolite thrust sheet complex” on Earth.

Through a process called obduction, as much as 15km of the oceanic crust and upper mantle has been pushed on top of the continental crust.

Since last year, the researchers have been gathering data that could offer new insights as to how this process took place.

The project’s chief investigator is the institute’s Dr Mohammed Ali, an associate professor of geophysics.

From Oxford, Prof Tony Watts of the marine geology and geophysics departments and Prof Mike Searle of the earth sciences department are taking part, along with two postgraduate students.

A key method the scientists have employed is seismic refraction, which uses equipment, such as air guns, that produce pulses of sound over the ocean.

The way these sound waves are refracted or deflected gives information on what the structure of the Earth beneath the sea bed is like. This data has already been recorded during a three-week sea probe.

“Some compressed air was released in the water and produced a big bubble. The energy propagates into the crust and we record the answer from the crust,” said Dr Pilia, who completed his PhD last year at the Australian National University. He said the data off the east coast of Fujairah would be “very useful” for determining if there could be oil in the area.

Dr Pilia said that in contrast to the mountains this area has so far attracted little attention, and “pretty much nothing has been done there”.

On land, the researchers are using seismometers, small instruments buried about half a metre underground that record earthquakes and other movements in the earth.

Powered by a solar panel and checked every two to three months, these are being placed at regular intervals all the way across the UAE. After about a year, the seismometers will be moved to record data from another place.

“These are very, very sensitive instruments that can record earthquakes from pretty much all over the world. or even record sounds of people or cars passing by,” said Dr Pilia.

The seismic analysis also stretches into areas covered by the sea because the formation of the mountains causes the upper part of the Earth to bend, creating “foreland basins” that often contain oil.

By undertaking a comprehensive seismic survey, the scientists can measure the thickness of the foreland basins, which is useful for those assessing what natural resources are present.

Gravitational and magnetic information is also being collected as part of the researchers’ ultimate goal, to better understand the deep crustal and mantle structures of the northern and eastern UAE. It is almost like producing a three-dimensional map of these areas.

The data will also help to improve the understanding scientists have of mountain formation in other parts of the world.

“In the earth sciences community, this is known as a great place to study geology and to study orogenic belts,” said Dr Pilia.

“It’s very well studied because it’s probably the only part of the world where the ophiolites are so well exposed. It’s the easiest place to understand what’s going on.

“Many times the formation or the evidence is covered by some younger material but here you just go to the field and see it with your own eyes.

“I’m definitely looking forward to having some results and to providing an explanation as to what’s going on here.”

The oil and gas industry will also be looking forward to seeing the results. The detailed information will help specialists in the sector interpret their own data.

In particular, the seismic refraction data, showing how the waves spread through the crust and mantle, and giving an accurate indication of the thickness of the crust, will make it easier for those searching for oil and gas to produce accurate measurements of depth.

So uncovering the mysteries of mountain formation should pay commercial dividends.