Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Significance and Distribution of Apatite in the Doig Phosphate Zone

Version 1 : Received: 7 September 2020 / Approved: 8 September 2020 / Online: 8 September 2020 (04:54:58 CEST)

How to cite: Lacerda Silva, P.; Bustin, R.M. Significance and Distribution of Apatite in the Doig Phosphate Zone. Preprints 2020, 2020090170 (doi: 10.20944/preprints202009.0170.v1). Lacerda Silva, P.; Bustin, R.M. Significance and Distribution of Apatite in the Doig Phosphate Zone. Preprints 2020, 2020090170 (doi: 10.20944/preprints202009.0170.v1).

Abstract

The Doig Phosphate Zone (DPZ) is a phosphate-bearing marine unit located at the base of the Doig Formation, in the Triassic section of the Western Canada Sedimentary Basin. The DPZ has a maximum thickness of 90 m and extends across northeastern British Columbia and western central Alberta. In this study we characterize the significance and interpret the origin of apatite in the DPZ, through mineralogical and geochemical analyses, thin section study and field emission-scanning electron microscopy. The occurrence of apatite in the DPZ is not evenly distributed, but restricted to discrete 10 to 20 cm thick beds, located near the base of the DPZ. Phosphorites are of two types: grainstones composed primarily of unconformity-bounded coated grains, and intraclastic phosphorites composed of detrital silt-sized grains and apatite coated grains in a cryptocrystalline phosphatic matrix. The phosphorite beds are records of stratigraphic condensation due to low detrital input during transgression. The erosionally-truncated phosphatic coated grains and intraclasts are interpreted to be a result of various phases of phosphatization, exhumation, erosion reworking, winnowing and redeposition in alternating quiescence and storms or bottom currents. The abundance of pyrite and chalcophile trace elements, as well as the low concentration of proxy elements for organic matter productivity and preservation, are further evidences of stratigraphic condensation, with sulfidic pore water development and extensive organic recycling promoted by biological activity during the long exposure times. The phosphorites were formed under oxygenated water conditions, as suggested by the depletion in Ce and presence of a diverse benthic fauna.

Subject Areas

Doig Phosphate Zone; phosphorite; apatite; coated grains

Comments (0)

We encourage comments and feedback from a broad range of readers. See criteria for comments and our diversity statement.

Leave a public comment
Send a private comment to the author(s)
Views 0
Downloads 0
Comments 0
Metrics 0


×
Alerts
Notify me about updates to this article or when a peer-reviewed version is published.
We use cookies on our website to ensure you get the best experience.
Read more about our cookies here.