On the lognormal distribution of oxides in igneous rocks, using magnetic susceptibility as a proxy for oxide mineral concentration

Trace element concentrations in igneous rocks are frequently lognormally distributed, and Shaw (1961) suggested that minor minerals in igneous rocks might also be lognormally distributed. There is accumulating evidence to show that bulk magnetic susceptibility (BMS) often closely follows a lognormal distribution in fresh igneous rocks but, because BMS is dependent upon oxide-grain size and mineralogy, it is not obvious why this should be so. We …