Iron shows the way to copper and gold

Kirunavaara is also the site that has given the ore its name, the Kiruna types of apatite iron ore, a name that is used internationally. In many places around the world, such as Chile and Sweden, copper and gold have also been found near certain iron ores, a fact that has led researchers from Luleå University of Technology in Sweden to believe that these “big three” were formed at the same time, deep down in the crust of the earth.

At Tjärrojåkka, about fifty kilometers west southwest of Kiruna, the Geological Survey of Sweden (SGU) found an iron deposit in the mid 1960s, and a few years later a nearby copper/gold mineralization was discovered. No mining ever took place since the deposit was too small to be profitable, but all the information­drill cores, protocols, and analysis results­are preserved at the SGU information office in Malå. Tjärrojåkka is the best Swedish example of proximate iron and copper/gold finds and has therefore been used as the object of study in Åsa Edfelt’s doctoral dissertation, which she will defend at Luleå University of Technology on May 25.

“The point of departure for my studies has been to examine whether iron ores and copper/gold ores can be formed during one and the same ore-formation event, and to identify properties in them that can be used for prospecting both in Sweden and abroad,” says Åsa Edfelt.

“I have carried out comparative studies of age, chemical characteristics of minerals, formation temperatures, and the consistency of the ore-forming solutions in these two finds at Tjärrojåkka and found that they were formed during one and the same event.”

In her research, Åsa Edfelt has also shown that the mineral apatite could possibly be used to determine what types of iron ore are lead to copper. The findings are of great significance to the prospecting market, which is currently red hot both in Sweden and in other parts of the world. Some 50 iron deposits are already known in northern Sweden and may also be of interest when it comes to copper and gold.

Brief wordlist
Deposit­-an occurrence of ore or industrial minerals, building stones, oil, gas, sand, gravel, or other naturally occurring types of ground or rocks

Ore-­naturally occurring mineral concentration containing metal that is economically worth extracting

Mineralization­-name of the mineral concentration