Because of the confusion in the literature regarding usage of LILE, it is recommended that the term be restricted to lithophile trace elements having small charge to ionic radius ratios and which also have ionic radii greater than those of Ca 2+ and Na 1+ , the largest cations common to rock forming minerals. relative to more compatible trace elements. The LILE are strongly enriched in the upper continental crust (. ), but occur in lower concentrations in the deep continental crust due to its overall more mafic character and selective loss of some LILE during high-grade metamorphism (see Metamorphism).