By Dan Oancea - Twitter

 

A golden meteorite was about to strike the Earth. A huge crowd followed its smoky trail, embarking on a new kind of gold rush. Scientists have gone mad about it too - but all this happened just in the pages of “Hunt for the Meteor”, published about 100 years ago by Jules Verne, the visionary founder of Sci-Fi.

Nobody has ever found the golden meteorite, but people have started to realize that some of the giant craters that riddle the scenery could indeed be the result of a real meteor impact. At least this was the opinion of a 1902 Philadelphia mining engineer about a crater that lies in the sands of the Arizona desert and is surrounded by nickel-iron fragments. Daniel Barringer was the owner of a considerable fortune made by the discovery of silver mines in the Arizona’s mountains. Lacking our understanding of high-speed impacts he reasoned that the big chunk of meteoritic iron is still buried deep in the crater. Twenty six years later, after spending his fortune on top of investor’s money-about $10 million in today’s dollars- the Meteor Crater Exploration and Mining Company stopped working the shafts and galleries that were supposed to lead to a 10 million tons meteorite.

In 1883, a blacksmith identified copper sulphide in the rocks cut by the advancement of the Canadian Pacific railway at Sudbury, Ontario. It later became the Murray Mine. In 1891 a new company was formed to mine the metal: the Canadian Copper Company, a company that soon enough became aware that the mined ore contained a more valuable metal: Nickel. It changed its name in the International Nickel Company (INCO) and today, over 100 years later it still does the very same business mining the richest nickel deposit in the world.

The interpretation of the oval shape structure that hosts the Sudbury deposit generated hot debates, but everything came to an end in 1963, when U.S. geologist Robert Dietz, who at that time was working for NASA trying to put the first man on the Moon, recognized it as an impact structure. Well, not quite to an end, if we consider that in the early 1960s, Dietz was laughed out of the room at a geological conference when he tried to present its revolutionary theory. Later on, he teamed up with Walter Peredery, a young Canadian geologist and proved them all wrong.

Realizing the potential of impact craters to host mineral ores a new staking rush took place, mostly in North America. In Canada, another famous meteorite crater, the Manicouagan , is explored by daring junior exploration companies like Manicouagan Minerals, Fancamp Exploration and Quinto Technology (find more about their work by accessing InfoMine’s comprehensive database).

The Carswell structure of Saskatchewan benefited too from a meteor impact in the Cluff Lake area, where the impact created an uplift of the Athabascan sandstone revealing a number of large unconformity-type uranium deposits. Eso Uranium is carrying out its exploration programs in this area that represents the site of a renowned past producer-the Cogema’s Cluff Mine.

The above sea level portion of the rim of a huge meteorite impact crater known as the Chicxulub impact crater, located in Mexico has been studied amongst others by Glamis Gold.

The Vredefort impact structure of South Africa well-known for its gold-uranium deposits is intensively mined by different companies.

Lately, Great Australian Resources started investigating the South African Morokweng impact crater, where drilling intercepted high-grade nickel sulphide mineralization. Their confidence has been boasted by a geological report that summarized that all the conditions necessary for the formation of an ore body in impact structures are in place:

- A metal source: the Archaean gneissic basement,

- A concentrating mechanism: homogenization and differentiation through impact induced melting, and

- A trap for the mineralization: brecciated and fractured footwall rocks below the melt sheet.

A paper called “The formation, morphology, and economic potential of meteorite impact craters” gives us a good idea about processes involved in high-speed meteoritic impacts, while listing some of the most important deposits of this type.

Now, are we indeed in a shortage of exploration targets?

The authors of “Unraveling the Earth’s Geological History from Space using Impact Craters” provide us with a glimpse of the impact craters of our solar system, including the Earth, of course. The paper considers that:

“There are currently about 160 known impact craters on our planet, with diameters ranging from a few hundred meters to several hundred kilometers. This low number is due to the relatively young age and the dynamic nature of the terrestrial geosphere. We also have to take into account the fact that two-thirds of the Earth’s surface is covered by oceans, and that the tectonic movements of continental plates, as well as erosion, volcanism and sedimentation processes, have erased and/or hidden most of the original morphological effects of impact-cratering.”

According to their map, most of the impact craters are concentrated in the Pre-Cambrian shields, areas known to have been stable over the eons.  If North America, Europe and Australia have received a pretty fair amount of study, the scarcity of known impact craters in South America and Africa suggests the lack of systematic inter-disciplinary studies.  An algorithm based on the ‘Hough transform’ is also reported by the authors as very useful in the identification of impact craters from satellite imagery.

After reading some articles on the subject, I’m starting to feel that buying a plane ticket for trying to find impact craters in the under explored cratons of South America or Africa is not a bad idea at all.

Did you get the bug, yet?