Using trace elements in spinel and thermodynamic modeling to constrain the petrogenesis of Archean chromitites

This study presents a systematic investigation of the petrogenesis and parental magma characteristics of Mesoarchean chromitites from the North Atlantic Craton in SW Greenland based on integrated geochemical analysis of major and trace elements in chromite combined with thermodynamic simulations. The results indicate that these chromitites were predominantly derived from komatiitic parental magmas that experienced varying degrees of crustal contamination, including assimilation of tonalitic and potassium-rich granitoids. Although major elements serve as effective discriminators of tectonic settings in modern systems, their utility is limited in Archean terrains due to compositional overlap as a result of the effects of postmagmatic metamorphism and metasomatism. Nevertheless, major elements remain informative when integrated with trace element and thermodynamic modeling. In contrast, trace elements (e.g., Sc, Ti, V, Mn, Co, Ni, Zn, and Ga) exhibit relatively homogeneous distributions and provide more robust insights into parental magma composition and crustal assimilation processes. Thermodynamic modeling further confirms that the involvement of crustal materials under hydrous conditions played a critical role in chromitite formation. This study underscores the prevalence of melt-rock interaction and metasomatism during the hotter Archean conditions, and highlights the importance of a multiproxy approach for reconstructing ancient tectonic settings, offering new petrogenetic and geochemical constraints on early geodynamic processes and the onset of plate tectonics.