Evaluation of REY enrichment in Fe-Mn crusts from different seamounts and depths in the Canary Island Seamount Province Authors: Egidio Marino (Presenter), Francisco Javier González, Teresa Medialdea, Luis Somoza, Ana Belén Lobato, Jesús Reyes and Eva Bellido, Geological Survey of Spain (IGME-CSIC)

1. Evaluation of REY enrichment in Fe-Mn crusts from different
seamounts and depths in the Canary Island Seamount Province
Egidio Marino, Francisco Javier González, Teresa Medialdea, Luis Somoza,
Ana Belén Lobato, Jesús Reyes and Eva Bellido
ATLANTIS

2. Formation processes of Fe-Mn crusts and polymetallic nodules
• Hydrogenetic processes
• Diagenetic processes
• Hydrotermals processes
Genesis
Mn, Fe, REY

4. 42 samples recovered on 8 seamounts
16 different recovery sites
at different locations and depths
Canary Islands Seamounts Province
located on the west and south of
the archipelago
Africa
Atlantic Ocean

5. Samples are Fe-Mn crusts with variable thickness
from few centimeters to up to 25 cm
Under the microscope Fe-Mn crusts sho an high
variability of texture: dendritic, dense, mottled
most of the time in the same thin section

6. Diagenetic minerals
(todorokite, asbolane, buserite)
Accesory minerals
(quarts, feldspar, calcite, CFA)
Main minerals
(Vernadite, goethite)

8. Echo N=5
The Paps N= 17
Drago N= 8
Tropic N= 5
Gaire N= 4
Amuley N=1
Bimbache N=1
Las Hijas N=1
CISP Fe-Mn crusts are rich of several CRM
(Co, Ni, Mo, V and REY)

9. Influence of the genetic process
Diagenetic
Hydrogenetic

10. Vernadite ƩREY = 3800 µg/g
Fe-rich ƩREY = 780 µg/g
Asbolane/buserite ƩREY = 150 µg/g
Early diagenesys ƩREY = 460 µg/g
Vernadite ƩREY = 2700 µg/g
Todorokite ƩREY = 72 µg/g

11. Ce µg/g REE µg/g Y µg/g
Water
depth
(m)
Water
depth
(m)
Water
depth
(m)

12. 1500
1700
1900
2100
2300
2500
2700
2900
3100
6
8
10
12
14
CeSN/CesSN*
1500
1700
1900
2100
2300
2500
2700
2900
3100
200
300
400
500
La µg/g
1500
1700
1900
2100
2300
2500
2700
2900
3100
1000
1500
2000
2500
Ce µg/g
1500
1700
1900
2100
2300
2500
2700
2900
3100
120
170
220
270
320
Y µg/g
1500
1700
1900
2100
2300
2500
2700
2900
3100
2000
2500
3000
3500
4000
4500
ƩREY µg/g
Water
depth
(m)
Water
depth
(m)
Water
depth
(m)

13. CISP
~1600m

15. CONCLUSIONS
42 Fe-Mn crusts from 8 seamounts from the CISP have been studied for their contents of REY and their relationship with mineralogy,
genetic process, localization and depth.
Mineralogy and genetic processes are the main factors controlling REY contents. Hydrogenetic vernadite with slow growth rates
concentrate high contents (up to 4000 µg/g) of REY with highest contents represented by Ce up to 2300 µg/g.
Diagenetic asbolane, buserite and todorokite show low REY contents (on average 260 µg/g). Due to their mineral structure and fast
growth rates with up to 500 mm/Ma.
Another important factor is the formation depth of the samples. Fe-Mn crusts from shallower depth of 1800 m are more enriched in REY
(up to 3800 µg/g) due to the OMZ that promote very slow growth rates and also the dissolution of Fe-Mn minerals previously formed that
locally enrich seawater of dissolved REY. With depth REY contents slowly decrease reaching contents of 2800 µg/g at 3000 m water depth.
Together with depth the location of the samples and the water masses that bated them also influence REY contents. Fe-Mn crusts located
in the north face of the seamount show less REY contents due to the high oxygenated waters of the NADW. On the other hand, sample
deeper (4800 m) but located on the south part of the seamounts show high REY contents (average of 3300 µg/g) due to the mixing of
waters masses represented by the low oxygenated AAIW and the enriched in REY AABW.

16. Thanks
Grant agreement ID: 101091959
HORIZON-CL5-2021-D3-02-14, Project 101075609
ATLANTIS
(PID2021-12455OB-I00)