Reading Provenance from Detrital Quartz

Abstract

Quartz is the most abundant and durable mineral in all siliciclastic sediments representing almost all common parent rocks. In multicycle sediments some quartz may survive from several generations away and represent some remote parent rocks. Therefore, quartz has the greatest potential of all detrital minerals for reading provenance of arenites.

To this day, Krynine’s genetic classification of detrital quartz as modified by Folk remains as the focal point for many petrologic investigations. Continuous lattice dislocation produces undulosity in quartz crystals, whereas discontinuous high density lattice dislocation gives rise to polycrystallinity. Because lattice dislocation in quartz is much more common in metamorphic rocks than in igneous rocks, strongly undulose and finely polycrystalline detrital quartz grains in sediments tend to indicate dominance of metamorphic source rocks. Controlled studies show that abundance of such detrital grains in the medium sand-size range, if plotted in the diamond diagram proposed by the Indiana group, can successfully discriminate the dominance of different source rocks. Additionally, the internal fabric of detrital polycrystalline quartz grains may also indicate the relative importance of stress causing lattice dislocation and of thermal annealing in parent rocks.

Although the shape of detrital quartz grains is probably not diagnostic of specific parent rocks, availability of new well tested morphometric methods such as Fourier grain shape analysis or fractal geometry may have some promise for provenance interpretation. Trace and minor element abundances in individual detrital quartz grains hold the promise of assigning each grain to a specific rock type, but we have to wait for the sophisticated technology to be routinely available to sedimentary petrologists before such endeavours are made.