I suppose that they have used the word "non-ferrous" in a rather loose way, i.e. referring to the classic non-ferrous metals and to the other metals similar to them, which accumulate into sulfides, not into oxides.
The lithophile metals, which have higher affinity for oxygen, e.g. aluminum, magnesium, titanium etc. are not particularly abundant around volcanoes. Such metals could be separated from minerals only starting with the 19th century, so before that all the "non-ferrous" metals were obtained from sulfides or alteration products of sulfides. Some continue to use "non-ferrous" with the ancient meaning, not with its literal meaning.
The sulfide minerals and a few other minerals associated with sulfides are byproducts of magma cooling, either by phase separation from magma or by dissolution and precipitation in hot fluids, in actual volcanoes and also in places where the raising magma did not reach the surface.
There are a large number of important metals, e.g. copper, zinc, lead, molybdenum, silver and many others, which come almost exclusively from sulfide minerals or from minerals produced by atmospheric alteration of former sulfide minerals, so those may be said to be mostly of volcanic origin.
The lithophile metals, which have higher affinity for oxygen, e.g. aluminum, magnesium, titanium etc. are not particularly abundant around volcanoes. Such metals could be separated from minerals only starting with the 19th century, so before that all the "non-ferrous" metals were obtained from sulfides or alteration products of sulfides. Some continue to use "non-ferrous" with the ancient meaning, not with its literal meaning.
The sulfide minerals and a few other minerals associated with sulfides are byproducts of magma cooling, either by phase separation from magma or by dissolution and precipitation in hot fluids, in actual volcanoes and also in places where the raising magma did not reach the surface.
There are a large number of important metals, e.g. copper, zinc, lead, molybdenum, silver and many others, which come almost exclusively from sulfide minerals or from minerals produced by atmospheric alteration of former sulfide minerals, so those may be said to be mostly of volcanic origin.