University of Oulu

Graul, S., Kallaste, T., Moilanen, M., Ndiaye, M. and Hints, R. 2023. Early diagenetic transformation stages revealed by micro analytical studies of shelly phosphorites, Rakvere region. Estonian Journal of Earth Sciences, 72(1), 34–37.

Early diagenetic transformation stages revealed by micro-analytical studies of shelly phosphorites, Rakvere region

Saved in:
Author: Graul, Sophie1; Kallaste, Toivo1; Moilanen, Marko2;
Organizations: 1Department of Geology, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn, Estonia
2Oulu Mining School, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.3 MB)
Persistent link:
Language: English
Published: Estonian Academy Publishers, 2023
Publish Date: 2023-09-27


Furongian–Tremadocian phosphorites of Estonia are sandstone rich in biogenic apatite, represented by brachiopod detritus. The study focuses on the mineralogical and micro-analytical characterisation of phosphorites from the Aseri, Toolse, and Kabala deposits based on FE-SEM and EPMA analyses. The shell fragments are composed of alternating compact and porous laminae, but with considerably poor preservation of pristine textures, superseded by the formation of authigenic CAF-apatite during the early diagenesis. In all settings, the shells showed preferential uptake of Sr into the porous cryptocrystalline laminae. The altered areas are composed of massive apatite crystallites with Mn-enriched layers. They are frequently covered with pyrite, indicating progressive recrystallisation under the influence of interstitial fluids and fluctuations in redox gradients in coastal environments.

see all

Series: Estonian journal of earth sciences
ISSN: 1736-4728
ISSN-E: 1736-7557
ISSN-L: 1736-4728
Volume: 72
Issue: 1
Pages: 34 - 37
DOI: 10.3176/EARTH.2023.12
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Funding: This study was supported by the ERDF and the Estonian Research Council via project RESTA23. The publication costs of this article were partially covered by the Estonian Academy of Sciences.
Copyright information: © 2023 Authors. This is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (