| Title | Rare earth elements in conodont apatite: seawater or pore-water signatures? |
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| Author | Trotter, J A; Barnes, C R; McCracken, A D |
| Source | Palaeogeography, Palaeoclimatology, Palaeoecology vol. 462, 2016 p. 92-100, https://doi.org/10.1016/j.palaeo.2016.09.007 |
| Year | 2016 |
| Alt Series | Earth Sciences Sector, Contribution Series 20160001 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Manitoba; Ontario; Newfoundland and Labrador; Quebec; Nunavut |
| NTS | 2D; 2E; 2L; 2M; 11O; 11P; 12A; 12B; 12E; 12F; 12G; 12H; 12I; 12P; 16D; 16E; 16K; 16L; 16M; 16N; 22H; 25G; 25H; 25I; 25J; 25K; 25L; 25M; 25N; 25O; 25P; 26; 27; 36A; 36B; 36C; 36D; 36E; 36F; 36G; 36H; 36I;
36J; 36P; 37; 38A; 38B; 38F; 38G; 41G; 41H; 41J; 47C; 47D; 47E; 47F; 47G; 47H; 48; 52E; 52L; 52M; 57E; 57H; 58E; 58F; 58G; 58H; 59A; 59B; 62F; 62G; 62H; 62I; 62J; 62K; 62N; 62O; 62P; 63A; 63B; 63C; 63F; 63G; 63H; 63I; 63J; 63K; 68E; 68H |
| Area | Williston Basin; Manitoulin Island; Anticosti Island; Canadian Arctic Archipelago; Cornwallis Island; Baffin Island; Devon Island |
| Lat/Long WENS | -102.0000 -95.0000 55.0000 49.0000 |
| Lat/Long WENS | -83.2500 -81.5000 46.2500 45.5000 |
| Lat/Long WENS | -59.5000 -54.0000 52.0000 47.5000 |
| Lat/Long WENS | -64.7500 -61.5000 50.0000 49.0000 |
| Lat/Long WENS | -97.0000 -60.0000 76.7500 61.7500 |
| Subjects | paleontology; geochemistry; Nature and Environment; micropaleontology; microfossils; conodonts; pore water samples; models; apatite; paleoenvironment; biogeochemistry; biogenesis; sea water
geochemistry; marine sediments; mass spectrometer analysis; absorption; diagenesis; alteration; Laurentia; Animals; Phanerozoic; Paleozoic; Silurian; Ordovician |
| Illustrations | plots; tables |
| Program | Science laboratory network |
| Abstract | Rare earth element (REE) compositions of Lower Palaeozoic conodont microfossils from different sites in Laurentia are presented and compared to modern pore-water REE compositions reported in the
literature. These data are modelled to account for matrix-induced fractionation of REEs during uptake by apatite. The apatite-water partition co-efficients (Kd) for adsorption of REEs are applied to a range of modern pore-water compositions (i.e.
Pore-waterN × Kd), the resultant data being similar to Palaeozoic conodont apatite compositions. Similar resemblances to modern pore-water REE compositions are shown by palaeofluids derived from conodonts using the inverse relationship in REE
adsorption kinetics (i.e. Bioapatite/Kd), with rare low concentration samples yielding HREE-enriched patterns. These results clearly show the importance of matrix effects and hence the post-mortem physico-chemical processes by which elemental uptake
occurs in fossil biogenic minerals, which are crucial to consider when interpreting geochemical signatures. Furthermore, the similarities between apatite REE compositions of conodonts and those derived from modern pore-waters challenge prior
hypotheses of seawater REE evolution inferred directly from conodont apatite, and question the reliability of conodont apatite as archives of seawater REE chemistry. These outcomes likely have broader implications for fossil bioapatites in general
given the physico-chemical processes occurring within marine sediments and the inherent behaviour of apatite-REE systematics. |
| Summary | (Plain Language Summary, not published)
The rare earth element (REE) compositions in the mineral found in some fossils has been used to interpret shifts in ocean environments over geological
time, thus contributing to interpretations of hydrocarbon basin evolution. In this study of conodonts, which are jaw parts of extinct fish-like animals, the conclusion is that fossil apatites are not reliable archives of REE seawater chemistry and
instead reflect chemical changes within the seabed sediments. Conodonts are primarily used for determining the geological age and thermal history of rocks. Both of these are critical in studies of sedimentary basins and for improving the success of
hydrocarbon exploration. In addition, the conodont apatite mineral is increasingly used in geochemical studies of ancient environments - added value to the original collection use. |
| GEOSCAN ID | 297882 |
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