EXPERIMENTAL STUDIES ON THE ORIGIN OF IRON DEPOSITS

There has been a scientific debate about the formation of massive magnetite ore deposits, also known as Kiruna type deposits. While some workers have suggested a hydrothermal origin for these deposits others have suggested that they are formed from iron rich magmas. This work consists of six chapters each one related to the understanding of the origin of iron deposits. In chapter 1 a natural example from Chile is investigated. Chapter 2 experimentally investigates the effects of phosphorous and other volatiles on the melting behavior of andesite. The results show that when more than 12% of pure H3PO4 is added to the andesite, it produces an immiscible P-Fe-rich melt. Chapter 3 investigates the upper-thermal stability of actinolite which is common in many deposits. Chapter 4 investigates if actinolite is stable in the presence of a P-Fe-rich melt. Natural examples of magma immiscibility and new phases recently found at El Laco deposit are presented on Chapter 5 and finally, a general model for the formation of massive magnetite-apatite-actinolite deposits is presented in Chapter 6.