Assessment of the engineering behavior of ultramafic and mafic rocks using chemical indices

•The alteration of ophiolitic rocks can be quantified using chemical indices.•Chemical indices form various correlations with the strength properties of rocks.•The WPI index is the most suitable for the engineering assessment of peridotites.•The LOI provides a general estimation of the strength properties of mafic rocks.•Geochemistry assists in the selection of the most suitable aggregate materials.

Geochemistry is of great importance for the interpretation of the geomechanical quality of rock materials used in various construction applications. This paper investigates the interrelationships between selected chemical indices and various engineering parameters of ultramafic and mafic rocks from the Vourinos, Pindos, Koziakas and Othrys ophiolite complexes (northern and central Greece). The significance of these indices for the engineering assessment of ophiolitic aggregates is strongly demonstrated based on statistical analysis of the experimental results. The studied lithologies include dunites, olivine-rich harzburgites, typical harzburgites, plagioclase-bearing lherzolites, troctolites, diorites and dolerites, which show various degrees of alteration and tectonic deformation. The effect of alteration on rock strength and particularly the relationships between specific chemical indices and the engineering parameters are determined using simple regression analysis. The results designate that the WPI index is the most appropriate for the assessment of the engineering behavior of ultramafic lithologies, while the LOI index seems to provide a general estimation of the strength properties of mafic rocks.