wholerock

Wholerock, or whole-rock chemistry, refers to the bulk chemical composition of a rock sample as determined by analyzing the rock as a single material. This approach contrasts with mineral-specific analyses that target individual minerals within the rock. Whole-rock data are used to characterize the overall composition and to support petrogenetic interpretations of igneous, metamorphic, and sedimentary rocks.

Preparation and analysis typically involve collecting a representative rock sample, crushing and homogenizing it, and dissolving the sample in acids to liberate its constituent elements. Major elements are commonly measured by X-ray fluorescence (XRF), while trace elements are often determined by inductively coupled plasma mass spectrometry (ICP-MS) or ICP-optical emission spectrometry (ICP-OES). Results are reported as oxide weights (e.g., SiO2, FeO, Al2O3) or as concentrations in parts per million for trace elements. Major-element data are frequently normalized to 100% total oxide to facilitate comparison among samples and with classification schemes.

Applications include rock classification, geochemical discrimination, and petrogenetic interpretation. Whole-rock chemistry helps distinguish rock types (felsic, intermediate, mafic, ultramafic) and supports analyses of magma differentiation, crustal contamination, and mantle source characteristics. It also underpins tectonic setting interpretations through trace-element patterns and ratios.

Limitations and considerations include sample representativeness in heterogeneous or altered rocks, potential biases from refractory minerals that resist digestion, and losses or gains of volatiles during digestion and analysis. Loss on ignition (LOI) and mineral phase contributions can influence results, and whole-rock data provide bulk information without mineral-specific textural or modal details.