Scientists find evidence of how platinum metals form in 60-year-old Scottish volcano

Research by scientists at Keele University, the University of Manchester and University College Dublin has shed new light on how precious metals are concentrated in igneous rocks.

The solidified remains of subvolcanic magmatic intrusions harbor the highest concentrations of platinum group metals in the Earth’s crust, such as platinum, palladium, and rhodium. Scientists refer to these bodies as layered mafic intrusions. Traditional models suggest that these layered intrusions form in high-volume magma chambers, but this new research has found that small amounts of magma are more likely to be repeatedly injected into a glass slurry.

The research, published in Nature Geoscience, demonstrates the case for reevaluation of the long-standing belief in how layered mafic intrusions are formed.

The research included conducting a detailed study of an extinct volcano roughly 60 million years old on the island of Rum in north-western Scotland. The mineral crystals in the Ron intrusion were analyzed using a new micro-sampling approach, to identify isotopic variations of the strontium element.

Measured variations of strontium isotopes provide evidence that crystallization of minerals in and around precious metal rich layers occurred within 10 to 100 years. The data also shows that layered intrusions, as in Ron, are formed by repeated self-intrusion of magma during solidification rather than by prolonged cooling from the bottom up and from the top down.

This new knowledge has important implications for understanding precious metal mineralization in mafic igneous systems in general.

Dr. Ralf Gertisser of Keele University, reader of mineralogy and petrology at the Keele School of Geography, Geology, and Environment, said: “The study significantly influences our understanding of how layered intrusions and deposits form. of precious metals within them. “

Dr. Luke Hepworth, former Ph.D. a student at Keele University College of Geography, Geology and Environment, added: “There is scope for the model proposed here to be extrapolated to rocks containing precious metals in mafic intrusions into larger and more economically significant layers, such as the Complex. Bushveld in South Africa and the Stillwater complex in the United States. “

Dr. Brian O’Driscoll, Senior Lecturer in Petrology, University of Manchester, said: “These new data highlight that the crystallization of layered intrusions and their associated platinum group metal mineralization can be a dynamic and rapid process. It will be exciting to see if these ideas can be extended to other economically important deposits in the future. ”