Chemical Fingerprinting in Detrital Ilmenite: A Viable Alternative in Provenance Research?

Detrital ilmenite grains carry unique chemical fingerprints that can be used in provenance research. The elemental composition (Mn, Ti, V, Mg, Cr, Al; reported in weight percent oxide as determined by electron probe microanalysis) of homogeneous detrital ilmenite grains from felsic plutonic and volcanic, intermediate volcanic, and mafic plutonic and volcanic parent rocks indicates that chemical signatures obtained in felsic and mafic igneous parent rocks are retained by detrital ilmenite grains in daughter sands. Grains from mafic igneous sources are enriched in TiO2 (50 +/- 1%) and have a more narrow range then grains from felsic igneous sources (48 +/- 2%). In addition, grains with MnO > 2.0% are most prevalent in sands from felsic rocks. Stepwise discriminant function analysis, using the oxides MnO, TiO2, V2O3, MgO, Cr2O3, and Al2O3 as the discriminating variables, found that grains from felsic and mafic igneous rocks could be correctly classified 86% of the time. However, when grains from intermediate volcanic sources were added to the model, correct classification dropped to 62%. The complex chemical nature of detrital ilmenite grains from intermediate igneous sources indicates that there is much yet to learn about the composition of detrital ilmenite grains. However, if used in conjunction with other methods, chemical fingerprinting in detrital ilmenite may be a valuable addition to provenance research.