The origin and composition of carbonatite-derived carbonate-bearing fluorapatite deposits

Carbonate-bearing fluorapatite rocks occur at over 30 globally distributed carbonatite complexes and represent a substantial potential supply of phosphorus for the fertiliser industry. However, the process(es) involved in forming carbonate-bearing fluorapatite at some carbonatites remain equivocal, with both hydrothermal and weathering mechanisms inferred. In this contribution, we compare the paragenesis and trace element contents of carbonate-bearing fluorapatite rocks from the Kovdor, Sokli, Bukusu, Catalão I and Glenover carbonatites in order to further understand their origin, as well as to comment upon the concentration of elements that may be deleterious to fertiliser production. The paragenesis of apatite from each deposit is broadly equivalent, comprising residual magmatic grains overgrown by several different stages of carbonate-bearing fluorapatite. The first forms epitactic overgrowths on residual magmatic grains, followed by the formation of massive apatite which, in turn, is cross-cut by late euhedral and colloform apatite generations. Compositionally, the paragenetic sequence corresponds to a substantial decrease in the concentration of rare earth elements (REE), Sr, Na and Th, with an increase in U and Cd. The carbonate-bearing fluorapatite exhibits a negative Ce anomaly, attributed to oxic conditions in a surficial environment and, in combination with the textural and compositional commonality, supports a weathering origin for these rocks. Carbonate-bearing fluorapatite has Th contents which are several orders of magnitude lower than magmatic apatite grains, potentially making such apatite a more environmentally attractive feedstock for the fertiliser industry. Uranium and cadmium contents are higher in carbonate-bearing fluorapatite than magmatic carbonatite apatite, but are much lower than most marine phosphorites

A public relations identity for the 2010s

New voices are being heard and new questions are being asked within the field of public relations. However, in its present multifaceted state, public relations research is still struggling with recurring questions regarding academic and practical contributions. This position article presents some common starting points for a public relations identity for the 2010s aiming to preserve both consistency and multiplicity. We argue that public relations should be studied as a social activity in its own right and that it must be understood in relation to its societal context. Furthermore, we point to some concepts (trust, legitimacy, understanding and reflection) that are crucial to understanding public relations practice. We also argue that issues of power, behavior, and language have to be dealt with if public relations is to be taken seriously as an academic field. Building on these ideas we make some suggestions for empirical research. Finally, we propose, on a philosophical level, to develop a critical realist framework in order to study public relations scientifically