Regulation of fluorine chemistry and carbonate fluorapatite stability in deep sediments beneath the Peruvian upwelling zone
Donohue, Catherine Marie
Dickens, Gerald R.
Master of Science
Fluorine is abundant in the oceans, and carbonate fluorapatite precipitation in marine sediment is a significant removal mechanism. A paucity of data has led to several misconceptions of fluorine geochemistry and carbonate fluorapatite (CFA) diagenesis, a fluorine and carbonate substituted apatite (Ca10 (PO4)5.74(CO3)0.26F 2.26). This thesis will revise and expand our understanding of fluorine and CFA in deep sediment by proving fluorine's availability, documenting CFA precipitation, and demonstrating alkalinity controls on fluorine and CFA. Because CFA is the main mineral phase of economic phosphorite deposits, its development has warranted much study. However, previous research focused on PO43- and F concentrations in pore waters of shallow sediment (<10 meters) and is incomplete. Here, previous work is improved by directly measuring fluorine concentrations in sediments and pore waters from deep cores (>100 meters) near the upwelling zone of the Peru margin. These results are then related to CFA diagenesis.
Physical oceanography; Geochemistry