Newcastle University

As part of Newcastle University’s Gallery of Wonder, the display of photomicrographs are the result of 30 years of painstaking hunting, chipping and polishing to produce slithers of rock no more than 30 microns thick.

Originating deep underground as a result of volcanic activity, Professor Younger says these hard, black rocks rarely attract a second glance.

“To the naked eye they’re pretty unremarkable but under the microscope they tell an amazing story in patterns and colours you won’t find anywhere else in nature,” he explains.

“They are a glimpse into an otherwise unobservable world.”

The rocks – known as “mafic” (magnesium and ferrous (iron) rich) – date back as much as 2,500 million years and were formed in the deep-seated magma chambers far below active volcanoes.
 
“In some cases the ancient volcanic activity caused underground cracking of the Earth for hundreds of miles around, the molten rock spreading out to fill the gap,” explains Professor Younger.

“Thus the rocks sampled in the Cleveland Hills originated beneath an ancient volcano on the Isle of Mull, some 250 miles away in the Inner Hebrides.

“For geologists, these rocks help us to unravel some fundamental mysteries, concerning the otherwise-unobservable processes that occur deep below our feet.

“There isn’t - and never will be - a way to observe these processes directly, but when we look at these rocks down the microscope, we can reconstruct what must have gone on from the shapes and compositions of the minerals.”

One of the slides – a shimmering gold piece of olivine – is from the Whin Sill, a rock layer which was found half a mile below Newcastle during the recent drilling of the University’s geothermal borehole.

Led by Professor Younger, the exploration for hot water under Science Central – the site of the former Scottish and Newcastle Brewery – is beginning to heat up.

“We are now in the process of testing and analysing exactly what lurks down the borehole – and the main thing to report so far is that the temperature down there is even higher than we’d hoped, which is just phenomenal,” says Professor Younger.

“It’s a lengthy process, but we’re about halfway down and the temperature gradient we’re recording is almost 4oC/100m which means we’re looking at a temperature of almost 80 oC at the bottom of the borehole.”

In most of the UK, the background ‘geothermal gradient’, as it is called, is in the order of 2.2 to 2.5oC/100m.
 
The heat is a combination of that produced naturally by the buried granite and that which is conducted upwards from the semi-molten mantle of the Earth tens of kilometres below the surface.

“Any heat coming from the granite is likely to be moving towards Newcastle along a large system of faults and deeply-buried beds of sandstone,” explains Professor Younger.

“Frustratingly, we now need to mobilise some different gear to clear a small blockage in the borehole about halfway down where some shale beds have tipped across the hole since we flushed the mud out.

“It’ll take us a bit of preparation before we can do that, but with a fantastic geothermal gradient like this, we have every encouragement to get back in there as soon as possible and take the next steps towards harnessing this increasingly exciting resource.”

The geothermal project is the first piece of research to be carried out on Science Central which will become a hub for the University’s sustainability research and further reinforce Newcastle’s reputation as a City of Science and Technology.

Professor Younger’s rock slides are on display at the Gallery of Wonder, which is located in the University’s main quadrangle just through the iconic Arches, until December 2nd.  For more information about this and upcoming exhibitions go to http://www.galleryofwonder.co.uk/