Application of Rare Earth Elements in Geological Studies with Case studies.

1. APPLICATIONS OF RARE EARTH ELEMENTS IN
GEOLOGICAL STUDIES
A SEMINAR PRESENTATION
BY
ADEYINKA, SOLOMON ADEOLA
UNIVERSITY OF ILORIN
SUPERVISOR: DR. O.A. ADEKEYE
JANUARY, 2016

2. OUTLINE
• Introduction
• Objectives of Seminar
• Classification of Rare Earth Elements
• Geology and Abundance of Rare Earth Elements
• Application OF REEs in Geological Studies
• Case Studies

3. INTRODUCTION
• Rare Earth Elements (REEs) are seventeen (17)
elements, comprising Scandium (n=21), Yttrium
(n=39) and the fifteen (15) Lanthanides on the
periodic table of elements (atomic number 57 to
71) (Connelly, 2005).
• Scandium and Yttrium of Group IIIb on the
periodic table of elements are typically included
with the rare earth elements because they share
chemical, physical, and application properties
with the lanthanides (Table 1).

4. INTRODUCTION
Table 1. Periodic table of the elements showing Rare Earth Elements (Long et al., 2010)

5. OBJECTIVES
• To review the geology of rare earth elements
• To discuss the various applications of rare
earth elements in geological studies

6. CLASSIFICATION OF RARE EARTH ELEMENTS
• REEs are mainly classified into two groups:
- LIGHT RARE EARTH ELEMENTS (Lanthanum
to Samarium) and
- HEAVY RARE EARTH ELEMENTS (Europium
to Lutetium) (Table 2), based on their ionic
radii and other physicochemical properties
(Table 3):

7. CLASSIFICATION OF RARE EARTH ELEMENTS
Table 2. Periodic table of the elements showing the division between LREEs and HREEs (Schuler et al., 2011).

8. CLASSIFICATION OF RARE EARTH ELEMENTS
Table 3 Rare Earth elements—overview of selected characteristics (Zepf, 2013)

9. GEOLOGY OF RARE EARTH ELEMENTS
• Most of the REE are not as rare as the
group’s name suggests. Cerium is the most
abundant REE (Table 4), and it is actually
more common in the Earth’s crust than
copper or lead (Taylor and McLennan,
1985).
• REE-bearing mineral deposits have various
origins and modes of formation (Table 5)
and they occur on all continents of the
world (Figure 1).

10. GEOLOGY OF RARE EARTH ELEMENTS
Element Symbol Atomic
Number
Upper Crust
Abundance,
ppm
Chondrite Abundance,
ppm
Scandium Sc 21 16.0 na
Yttrium Y 39 22 na
Lanthanum La 57 30 0.34
Cerium Ce 58 64 0.91
Praseodymium Pr 59 7.1 0.121
Neodymium Nd 60 26 0.64
Promethium Pm 61 na na
Samarium Sm 62 4.5 0.195
Europium Eu 63 0.88 0.073
Gadolinium Gd 64 3.8 0.26
Terbium Tb 65 0.64 0.047
Dysprosium Dy 66 3.5 0.30
Holmium Ho 67 0.80 0.078
Erbium Er 68 2.3 0.20
Thulium Tm 69 0.33 0.032
Ytterbium Yb 70 2.2 0.22
Lutetium Lu 71 0.32 0.034
Table 4. REEs and their abundances in the Earth crust and in Chondrites (Taylor and McClennan 1985)

11. GEOLOGY OF RARE EARTH ELEMENTS
Table 5. Various Origins of REE-bearing mineral deposits with examples (Long et al., 2010)
SedimentaryMetamorphicIgneous

12. GEOLOGY OF RARE EARTH ELEMENTS
Figure 1. Map showing the global distribution of REE (BGS, 2011)

13. GEOLOGY OF RARE EARTH ELEMENTS
• The largest known REE resource in the world is
The Fe-REE-Nb at Bayan Obo in Inner Mongolia,
China, discovered by Russian geologists in 1927
(Castor and Hedrick, 2006).
• The Bayan Obo Group was deposited
unconformably on 2.35-Ga migmatites, and,
along with Carboniferous volcanics, was
deformed during a Permian continent-to-
continent collision event dominated by folding
and thrusting (Drew et al., 1990).

14. GEOLOGY OF RARE EARTH ELEMENTS
• The two largest are the Main and East ore
bodies (Figure 2), each of which include iron-
REE resources with more than 1,000 m of
strike length and average 5.41% and 5.18%
rare earth oxides (REOs), respectively (Yuan et
al. 1992).
• Total Reserves have been reported as 48 Mt of
REOs (average grade 6%)

15. GEOLOGY OF RARE EARTH ELEMENTS
• Intrusion of large amounts of Permian granitoid
rocks also resulted from this collision. It has been
dated at 1600 Ma (Yuan et al., 1992) and 550 to
400 Ma (Chao et al., 1997).
• The Bayan Obo ore is hosted by dolomite of the
Bayan Obo Group, a Middle Proterozoic clastic
and carbonate sedimentary sequence that occurs
in an 18-km-long syncline (Qiu et al., 1983; Chao
et al., 1997; Drew et al., 1990).

16. GEOLOGY OF RARE EARTH ELEMENTS
Figure 2. Geologic map of the Main and East iron-REE-niobium ore bodies at Bayan Obo,
China (Chao et al. 1997).

17. GEOLOGY OF RARE EARTH ELEMENTS
• The REE ore consists of three major types:
REE-iron ore, the most important type; REE
ore in silicate rock; and REE ore in dolomite
(Yuan et al. 1992)
• Major oxide chemistries of several Bayan Obo
ore types are shown in Table 6. The REEs are
mainly bastnasite and monazite, but at least
20 other REE-bearing minerals have been
identified (Yuan et al. 1992).

18. GEOLOGY OF RARE EARTH ELEMENTS
Table 6. Minerals that contain REEs and occur in economic or potentially economic deposits (Mariano,1989a)

19. GEOLOGICAL APPLICATION OF REEs
• Some REE tools used as proxies in geological
studies include:
1. La Anomalies,
2. Ce Anomalies,
3. Eu Anomalies
4. Y/Ho ratios
5. Nd isotope ratios (143Nd/144Nd) and
6. Sm/Nd ratios

20. GEOLOGICAL APPLICATION OF REEs
Geological application of REEs includes:
• Paleoenvironmental studies
• Provenance studies
• Sedimentary processes
• Petrogenetic modelling
• Geochronology
• Paleoclimate reconstruction

21. APPLICATION OF REE TO PETROLEUM SYSTEMS
1. The Paleodepositional environment
reconstruction of source rocks (Murray et al.,
1990; Pi et al., 2013).
• REE compositions of kerogens (petroleum
precursors) could place better constraints on
oceanic redox conditions (Pi et al., 2013)

22. APPLICATION OF REE TO PETROLEUM SYSTEMS
2. Classification of crude oils or solid bitumens.
• Parnell (1988) found that dysprosium (Dy)
contents may be of value in discriminating
between solid bitumens from different sources.
• Akinlua et al. (2008) classified Niger Delta oils of
different sources using the contents and patterns
of light rare earth elements (LREE).
• Jiao et al. (2010) analyzed REE compositions of
two end-member oils of the Cambrian-Ordovician
in the Tarim Basin, and determined whether the
oils were derived from mixed sources.

23. APPLICATION OF REE TO PETROLEUM SYSTEMS
• Ramirez-Caro (2013) compared REE patterns of
Mississippian oils and Devonian Woodford shales
from Anadarko Basin, and demonstrated that
Mississippian oils were generated from the
Woodford shales.
• Manning et al. (1991) evaluated Nd isotope
values (143Nd/144Nd) and Sm/Nd ratios as
potential tools for oil-source correlation by
comparing both ratios in source rocks, hydrous
pyrolysates from source rocks and crude oils.

24. GEOLOGICAL APPLICATION OF REEs
3. Provenance studies and Sedimentary
processes
• It has been established that REEs in
terrigenous sediments are exceptionally
unreactive, thus making them very useful for
provenance studies. Sediments, especially in
rivers are sources of transportation and sinks
for REEs (McLennan, 1989).

25. GEOLOGICAL APPLICATION OF REEs
4. Petrogenetic modeling
• Europium (Eu) anomalies (positive or negative
departures of europium from chondrite- normalized
plots) have been found to be particularly effective for
Petrogenetic modeling.
• The relative abundance of individual lanthanide
elements has been found useful in the understanding
of magmatic processes and natural aqueous systems.
Comparisons are generally made using a logarithmic
plot of lanthanide abundances normalized to
abundances in chondritic (stony) meteorites.

26. GEOLOGICAL APPLICATION OF REEs
5. Geochronology
• REE isotopes, particularly of neodymium and
samarium, have found use in petrogenetic modelling
and geochronology
6. Nd isotopes serve as a pointer to changes in erosional
input, sedimentation rates and ocean circulation in
marine sediments (Dahlqvist et al., 2005)
7. Neodymium isotopes in planktonic foraminifera
records the response of continental weathering and
ocean circulation rates to climatic change (Vance and
Burton, 1999).

27. Case study One
Preliminary investigation of rare earth element (REE) composition of shales in the
Oshosun Formation exposed in the Sagamu quarry, eastern Dahomey Basin
Southwestern Nigeria.
O.A. Adekeye et al., 2007
Introduction
 The Oshosun Formation in eastern Dahomey Basin, southwestern Nigeria consists
of shale sediments, which are significant for their phosphorite and pyrite
compositions and are fossiliferous. The shales are lower Eocene-middle Eocene
age, are well laminated and contain glauconitic grains.
 The study area for this work is located at Sagamu quarry of the West African
Portland Cement (WAPCO) where the sedimentary section is exposed.
 The result of this study was used to predict the shale sediment precursors and
Source rock type to enhance the geological knowledge of the shale build-up.

28. Case study One (cont.)
Methodology
 Five (5) selected shale samples were analysed for their rare earth elements by
Neutron Instrumental Activation Technique. This method involves the irradiation
of samples together with a standard with neutron flux. REEs content in the
samples were determined by comparing their residual counts after cooling from a
reference standard irradiated under the same condition as samples. The standard
used in this study is DMMAS-16-1.
Results and Discussions/Findings
 Results of the rare earth elements (REE) analysis of the five shale samples from
the Eocene Oshosun Formation indicates REEs values ranging from ~0.5 to
139ppm.
 Strong positive Ce anomalies were consistent in all the six shale samples analysed.
The enrichment of Ce indicates that the Oshosun shales have undergone some
degree of phosphatization leading to the precipitation of phosphate minerals.
 The chondrite-normalised REE abundances are generally lower than those
reported for North American shale composites and for most Mississippian Valley
Type Lead-zinc deposits with strong europium anomalies that were derived from
predominantly arkosic rocks with abundant plagioclase feldspars.

30. Summary of Case study one
 The shales of the Oshosun Formation investigated for their rare earth elements
(REE) show a preliminary pattern of their composition.
 The results show a slight enrichment in the light rare earth elements but a
significant depletion in the heavy REE similar to the seawater derived shales. This
signifies that the shale precursors are granitic rocks with large proportions of alkali
feldspars and low contents of plagioclase feldspars.
 The enrichment of Ce indicates that the Oshosun shales have undergone some
degree of phosphatization leading to the precipitation of phosphate minerals.

31. Case Study Two
Rare earth elements fingerprints: Implication for provenance, tectonic and
depostional settings of clastic sediments of Lower Benue Trough, Southeastern
Nigeria.
O. C. Adeigbe and A. Y. Jimoh, 2014
Introduction
 The study areas, Lower Benue Trough is divided into Asu River Group (ARG) and
Cross River Group (CRG) and it is delimited by longitudes 7°00'E and 8°30'E and
latitudes 5°00'N and 6°30'N. ARG covers Awi, Abakaliki and Mfamosing Formations
while Ekenkpon, Eze-Aku, New Netim, Awgu and Agbani Formations fall within
CRG.
 The study aimed at using geochemical approach through rare earth elements
(REE) to deduce provenance and depositional environment.

32. Case Study Two (cont.)
Figure 1. Correlation chart of all outcrops studied showing their locations, formations and groups.

33. Case Study Two (cont.)
Methodology
 A total of 56 fresh outcrop samples collected from eight (8) Formations: Awi,
Abakaliki, Mfamosing Formations which constitute ARG and Ekenkpon, Eze-Aku,
New Netim Marl, Awgu, Agbani Formations which constitute CRG were obtained
from the study area.
 The samples were subjected to detailed lithologic description by visual
examination. Geochemical analysis was done using Inductively Coupled Plasma
Mass Spectroscopy (ICP-MS) to determine trace and rare-earth elements using
lithium metaborate/tetraborate fusion method.
Results and Discussions
 The chondrite normalized REE plots shows enrichment in the LREE over the HREE
with negative Eu anomaly for both ARG and CRG. While the (Eu/Eu*) average for
ARG and CRG are 0.74 and 0.73 respectively indicating Quartzose sedimentary,
Intermediate igneous and Felsic igneous provenances for the sediments.
 The Cerium anomaly (Ce/Ce*) values average 1.20 and1.68 in ARG and CRG
respectively indicating oxidizing and shallow marine environment. The REE pattern
is consistent with that of the Upper Continental Crust (UCC).

34. Case Study Two (cont.)

35. Summary of Case Study Two
 The chondrite normalized values for the rare earth elements of the three
Formations making up the Asu River Group revealed an appreciable enrichment in
the LREE (La-Nd) over the HREE (Er-Lu).
 The average europium anomaly (Eu/Eu*) value of the three Formations is 0.73 and
this coincides with the range of sediments from a felsic sources. While the cerium
anomaly (Ce/Ce*) value of 1.20 shows that the sediments were deposited in an
oxidizing environment and confirmed that the sediments of the Asu River Group
tend towards felsic sources as earlier confirmed by the europium anomaly.
 The REE pattern of the Cross River Group shows an enrichment of LREE and
depletion of HREE and indicates negative europium anomaly which is similar to
sediments of ARG.
 Evidences from the cerium anomalies with values >1 indicate an oxidizing
environments and that the sediments of Eze Aku, Ekenkpon, New Netim Marl,
Awgu and Agbani Formations were deposited in a shallow marine environment.

36. Case study Three
Rare Earth Elements (REE) as Geochemical Clues to Reconstruct
Hydrocarbon Generation History.
D. Ramirez-Caro, 2013
Introduction
• In this study, REE geochemical investigations were targeted on oils generated
in the Woodford shale and overlaying Mississippian formation located in the
Anadarko Basin, north-central Oklahoma.
• The REE distribution patterns and total concentrations of the organic matter of
the Woodford shale reveal a potential avenue to investigate hydrocarbon
maturation processes in a source rock.
• This study provides a valuable insight into the understandings of the REE
landscapes in the organic fraction of the Woodford Shale in northern Oklahoma,
linking these understandings to the REE analysis of an oil generated from the same
source bed and comparing it to oil produced from younger Mississippian oil. The
information gathered from this study may ultimately prove useful to trace the
chemical history of oils generated from the Woodford Shale source beds.

37. Regional Paleozoic Stratigraphic column in the Anadarko Basin.

39. Case study Three (cont.)
Methodology
• Ten samples of the organic matter fraction and 10 samples of the silicate-
carbonate fraction of the Woodford shale from north central Oklahoma were
analyzed by methods developed at Kansas State University. Thirteen oil samples
from Woodford Devonian oil and Mississippian oil samples were analyzed for REE
by inductively coupled plasma mass spectrometry (ICP-MS) and inductively
coupled plasma atomic emission mass spectrometry (ICP-AES). .
Results and Interpretation
• REE concentration levels in an average shale range from 170 ppm to 185 ppm, and
concentration levels in modern day plants occur in the ppb levels.
• The REE concentrations in the organic matter of the Woodford Shale samples
analyzed ranged from 300 to 800 ppm. The high concentrations of the REEs in the
Woodford Shale, as compared to the modern-day plants, are reflections of the
transformations of buried Woodford Shale organic materials in post-depositional
environmental conditions with potential contributions of exchanges of REE coming
from associated sediments.

40. Case study Three (cont.)
• The distribution patterns of REEs in the organic materials normalized to PAAS
(post-Archean Australian Shale) had the following significant features:
(1) all but two out of the ten samples had a La-Lu trend with HREE enrichment in
general,
(2) all but two samples showed Ho and Tm positive enrichments,
(3) only one sample had positive Eu anomalies,
(4) three samples had Ce negative anomalies, although one was with a positive Ce
anomaly,
(5) all but three out of ten had MREE enrichment by varied degrees.

41. Case study Three (cont.)

42. Summary of Case study three
• The REE distribution patterns for the Mississippian oil samples show a general
LREE enrichment with a minor MREE enrichment. Five out of the seven samples
have a Cerium negative anomaly and all of the samples have a Europium positive
anomaly.
• The Devonian oil samples have REE distribution patterns with a general LREE
enrichement, and a more prominent MREE enrichment is noticeable, when
comparing this samples to the Mississippian oil samples. Three out of the six
samples have cerium depletion and like the Mississippian oil samples, they show
europium enrichment.

43. Case Study Four
Evaluating rare earth elements as a proxy for oil-source correlation. A case study
from Aer Sag, Erlian Basin, northern China
P. Gao et al., 2015
Introduction
• Traditional geochemical tools for oil-source correlation such as biomarkers and
carbon isotopes can be hampered by thermal maturation and secondary alteration
(including biodegradation and water washing) and can lose their original
significance. Less attention has been paid to the application of REE to the
petroleum system.
• The newly found Aer Sag, located on the northeast margin of the Erlian Basin, first
produced commercial oil in 2006. It is a NE trending half-graben, covering an area
of 2000 km2, with 800 km2 in China and the rest in Mongolia.
Methodology
This study analyzed organic extracts and their corresponding whole rock materials for
REE compositions by inductively coupled plasma–mass spectrometry (ICP–MS).
Twenty-one samples were collected from the Lower Cretaceous of the Aer Sag, Erlian
Basin, northern China, including 14 mudstone samples and 7 oil sand

44. Case Study Four (cont.)
a, Crude oils from Well YM2 and Well TD2
sourced from the Middle-Upper Ordovician and
Cambrian marine source rocks, respectively are
regarded as two end-member oils in the Tarim
Basin, China (Jiao et al., 2010). TD2 crude oil
became denser by thermal alteration, with a
density
of 1.0217 g/cm3 1010 falling into the category
of heavy oil (Xiao et al., 2004).
b , Mississippian crude oils from Kansas State
and Anadarko Basin, USA sourced from
Devonian
Woodford (Chattanooga) shale enriched in
marine organic matter (Ramirez-Caro, 2013;
McIntire, 2014; 1013 Kwasny, 2015).
c , Dushanzi oil seeps from southern margin of
Junggar Basin mainly derived from Paleogene
lacustrine source rocks (Clayton et al., 1997; Li
et al., 2013).
d , Organic extract samples of marine
influenced coals from China can represent
transitional oil.
e , Niger delta crude oils with substantial
terrestrial organic matter input can represent
terrestrial oil (Akinlua et al., 2008).

45. Case Study Four (cont.)
a, Crude oils from Well YM2 and Well TD2 sourced from the Middle-Upper
Ordovician and
Cambrian marine source rocks, respectively are regarded as two end-member
oils in the Tarim
Basin, China (Jiao et al., 2010). TD2 crude oil became denser by thermal
alteration, with a density
of 1.0217 g/cm3 1010 falling into the category of heavy oil (Xiao et al., 2004).
b , Mississippian crude oils from Kansas State and Anadarko Basin, USA
sourced from Devonian
Woodford (Chattanooga) shale enriched in marine organic matter (Ramirez-
Caro, 2013; McIntire, 2014; 1013 Kwasny, 2015).
c , Dushanzi oil seeps from southern margin of Junggar Basin mainly derived
from Paleogene
lacustrine source rocks (Clayton et al., 1997; Li et al., 2013).
d , Organic extract samples of marine influenced coals from China can
represent transitional oil.
e , Niger delta crude oils with substantial terrestrial organic matter input can
represent terrestrial oil (Akinlua et al., 2008).

46. Case Study Four (cont.)
Fig. 1. PAAS normalized plots of the rare earth elements in various types of oils or extracts
from the world. REE patterns are plotted according to median values of available data.

47. Case Study Four (cont.)
Fig. 2. Cross-plot of REE values against the LaN/YbN ratio of various types of oils
or extracts from around the world

48. Summary of Case study four
• An attempt was made using rare earth elements (REE) for oil-source correlation
• REE cannot be used alone for oil-oil and/or oil-source correlations. Oil-source
correlations using REE were not consistent with conclusions based on biomarker
data and trace element ratios. Only one pair of oil-source rock relationships was
successfully established using REE.

49. CONCLUSION
 REEs can be of Primary origin (Carbonatites, Alkaline igneous rocks, Iron-REE,
Hydrothermal veins and Stockworks) or Secondary origin (Laterites, Marine,
Alluvial and Paleo-placers).
 REEs are essential tools in geological research for paleoenvironmental studies,
geochronology, oil-source correlation in petroleum systems, petrogenetic
modelling, provenance studies, sedimentary processes, paleoclimate
reconstruction and ocean water circulation.

50. THANK YOU