minerals-12-00981-v2.pdf

Citation: Barros, R.; Kaeter, D.;
Menuge, J.F.; Fegan, T.; Harrop, J.
Rare Element Enrichment in Lithium
Pegmatite Exomorphic Halos and
Implications for Exploration:
Evidence from the Leinster
Albite-Spodumene Pegmatite Belt,
Southeast Ireland. Minerals 2022, 12,
981. https://doi.org/10.3390/
min12080981
Academic Editors: Axel Müller and
Encarnación Roda-Robles
Received: 31 May 2022
Accepted: 28 July 2022
Published: 1 August 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
minerals
Article
Rare Element Enrichment in Lithium Pegmatite Exomorphic
Halos and Implications for Exploration: Evidence from the
Leinster Albite-Spodumene Pegmatite Belt, Southeast Ireland
Renata Barros 1,2,*, David Kaeter 1,3, Julian F. Menuge 1,3 , Thomas Fegan 4 and John Harrop 4
1 School of Earth Sciences, University College Dublin, Belfield, D04 V1W8 Dublin, Ireland;
david.kaeter@gmail.com (D.K.); j.f.menuge@ucd.ie (J.F.M.)
2 Geological Survey of Belgium, Royal Belgian Institute of Natural Sciences, 1000 Brussels, Belgium
3 iCRAG, University College Dublin, Belfield, D04 V1W8 Dublin, Ireland
4 Blackstairs Lithium Limited, The Black Church, St. Mary’s Place, D07 P4AX Dublin, Ireland;
fegan.thomas@gmail.com (T.F.); jcharrop@gmail.com (J.H.)
* Correspondence: renata.barros@ucdconnect.ie
Abstract: Pegmatitic deposits of critical metals (e.g., Li, Ta, Be) are becoming increasingly significant,
with growing interest in understanding metal enrichment processes and potential vectors to aid
the discovery of new resources. In southeast Ireland, the Leinster pegmatite belt comprises several
largely concealed Li-Cs-Ta albite-spodumene-type pegmatites. We carried out detailed mineralogical
characterization and whole-rock geochemical analyses of six drill cores intersecting pegmatite bodies
and their country rocks. Exomorphic halos 2–6 m thick, enriched in Li, Rb, Be, B, Cs, Sn and Ta, are
identified in both mica schists and granitic rocks adjacent to spodumene pegmatites. Metasomatism
in wall rocks visible to the naked eye is restricted to a few tens of centimeters, suggesting country rock
permeability plays a key role in the dispersion of these fluids. We propose that halos result from the
discharge of rare element-rich residual fluids exsolved near the end of pegmatite crystallization. Halo
geochemistry reflects the internal evolution of the crystallizing pegmatite system, with residual fluid
rich in incompatible elements accumulated by geochemical fractionation (Be, B, Cs, Sn, Ta) and by
auto-metasomatic resorption of spodumene and K-feldspar (Li, Rb). The possibility of identifying rare-
element enrichment trends by analysis of bedrock, stream sediments and soils brings opportunities
for mineral exploration strategies in Ireland and for similar albite-spodumene pegmatites worldwide.
Keywords: Leinster pegmatite belt; spodumene pegmatite; exomorphic halo; geochemical exploration
1. Introduction
Pegmatites are typically very coarse-grained, usually small, igneous rock bodies.
Granitic pegmatites, the commonest type, constitute economic sources of many industrial
and critical minerals [1–3]. As industry develops a growing range of high-technology
products containing rare elements, interest in understanding pegmatite petrogenesis and
rare-metal enrichment grows accordingly. In this context, spodumene pegmatites are
particularly significant due to their high concentrations of economically extractable Li and
the presence of other metals used in high-technology applications, such as Ta and Sn. Global
production of Li has increased about three times in the last five years to fulfill the increasing
demand from the lithium-ion battery market, mostly towards the decarbonization of
transport [4]. In Europe, Li was added to the Critical Raw Materials list in 2020 and there is
a strong interest in expanding local production to reduce its criticality [5].
The relatively sudden upturn in interest in Li has exposed the incomplete geological
understanding of Li-rich pegmatites. Key unresolved questions concern changes in magma
or melt chemistry during crystallization and chemical interactions with country rocks
during and after crystallization. Concerning the latter, it is well-known that rocks that host
Minerals 2022, 12, 981. https://doi.org/10.3390/min12080981 https://www.mdpi.com/journal/minerals

Minerals 2022, 12, 981 2 of 21
different types of magmatic-related deposits undergo varying degrees of hydrothermal
alteration, weakening away from the mineralized body [6]. Globally, such exomorphic
halos (Li, Rb, Cs, Be, B, F, H2O, Sn) are common in the country rocks hosting Li-rich
pegmatites and their exploration potential is known [7–12], though their mineralogy and
geochemistry have rarely been studied in detail in relation to pegmatite petrogenesis
(e.g., [7,13,14]). The links between the development of exomorphic halos and the evolution
of pegmatite crystallization are also poorly explored. The lack of detailed petrogenetic
models for albite-spodumene pegmatites and their halos has greatly limited the scope of
mineral exploration techniques for this pegmatite type, especially means by which the most
prospective pegmatites in a swarm could be targeted.
In Leinster, southeast Ireland, a spodumene pegmatite belt has been known since
the 1960s. It is virtually unexposed, but numerous concentrations of boulders have led to
repeated mineral exploration interest. Since 1970, exploration drilling has demonstrated
several spodumene pegmatites in the belt, which has its main bodies located along the
eastern margin of the mainly ~400–420 Ma [15] S-type Leinster Batholith. Exploration has
largely focused on known boulder accumulations and soil geochemical anomalies due to
the lack of other effective exploration strategies.
Previously published mineralogical, petrographic and geochemical descriptions of
Leinster pegmatites in general did not account for their interaction zones with wall rocks
(e.g., [16,17]). Advances in the understanding of the internal processes and geochemical
evolution in these pegmatites [18–20] now allow for better insight into the formation of
exomorphic halos. Moreover, a recent and ongoing mineral exploration drilling campaign
has provided an excellent opportunity for study.
In this paper, we set out a petrographic description and whole-rock geochemical
analyses of six drill cores through spodumene pegmatite and immediate country rocks
whose recovery is close to 100%. This information is supported by the logging of the drill
core and previous work on outcrops and boulders in the field. Particular attention is paid
to the nature of contacts between pegmatites and their country rocks. We qualitatively
model the crystallization history of the intrusions and show that exomorphic halos that
developed in wall rocks adjacent to the spodumene pegmatites are enriched in various rare
elements of economic interest such as Li, Cs, Ta and Sn. We argue that exomorphic halos
are formed at a late stage of the internal evolution of pegmatite bodies, contemporaneously,
with the change from the crystallization of coarse early-primary minerals to fine-grained
late-primary albitization. Both halo formation and albitization result from the expulsion of
volatile and fluxing elements from the crystallizing pegmatite melt. Finally, we discuss the
implications of our interpretations for mineral exploration.
2. Study Area
The study area is located in southeast Ireland within the Leinster Terrane (Figure 1),
which is dominated by sedimentary rocks deposited between the Cambrian and Lower
Ordovician in the Iapetus basin and deformed and affected by low-grade metamorphism
during the Caledonian orogenic cycle resulting, ultimately, from the closure of the Iapetus
Ocean [21–23]. The Ribband Group is the most dominant in the area and of special interest
as these are immediate country rocks, usually in the hanging wall, of some Leinster peg-
matites. The group consists of a thick succession of finely laminated mudstones deposited
during the Lower Ordovician, with occurrences of coticule and andesite lava [24].

Minerals 2022, 12, 981 3 of 21
The largest of the granitic bodies in the Leinster Terrane is the Leinster Batholith,
composed at least in part of sheeted intrusions of S-type two-mica granitic rocks [25–27].
It is mapped as four plutons of granite-granodiorite aligned with the NE–SW regional
strike (Figure 1). The ascent and emplacement of magma batches that compose the Leinster
Batholith is thought to have been facilitated by the East Carlow Deformation Zone (ECDZ),
a 3 km wide dip-slip ductile deformation zone active from the Middle Ordovician to the
late Carboniferous [24,28]. The largest and least exposed part of the Leinster Batholith is the
Tullow Lowlands pluton, which hosts LCT pegmatites along its eastern margin within the
ECDZ. It comprises equigranular and homogeneous granitic rocks, occasionally porphyritic
with K-feldspar megacrysts, as well as foliated and sheeted margins with abundant granitic
fingers within the adjacent schist, many of which remain undifferentiated in the local
geological sequence [24,27]. Their compositions vary from monzogranite to granodiorite,
with subordinate tonalite [16]. The heat provided by the emplacement of large volumes of
Leinster and older Blackstairs granitic magmas has imposed a thermal aureole of contact
metamorphism (up to 400 m wide) in the Ribband Group, turning regional greenschist
facies metasediments into pelitic and psammitic schists, with subordinate amphibolites
and chlorite schists of a volcanic origin [24]. The development of schistosity along with
porphyroblasts of sillimanite, staurolite, garnet, andalusite and biotite indicate aureole
temperatures above 500 ◦C [24,29].
The Leinster lithium pegmatite belt includes several mineralized (spodumene-bearing)
and many simple (quartz-feldspar-muscovite ± garnet) granitic pegmatite bodies ranging
from tens of cm to tens of m wide, with spodumene pegmatites known from at least ten
localities along the eastern margin of the Leinster Batholith (Figure 1). Mineralized peg-
matites are of the Li-Cs-Ta (LCT) albite-spodumene type [30] and host high concentrations
of Li (estimated between 1.5–3% Li2O) and economic potential for Ta and Sn. There appears
to be no regional or district zonation of pegmatite composition relative to the margin of the
Tullow Lowlands pluton. Occurrences are mostly within the ECDZ and thinner intrusions
present complex interfingering relationships with their country rocks, which are primarily
the Tullow Lowlands pluton and marginal granitic intrusions (Figure 2), but occasionally
Ribband Group schists. Mineralized pegmatites typically have a mineral assemblage of
10–40% spodumene and varying quantities of K-feldspar, albite, quartz, muscovite and
garnet, with accessory apatite, beryl, columbite-tantalite group minerals and sphalerite,
among others [18–20]. They are usually unzoned bodies, but some thicker intrusions have
quartz-rich cores. Primary megacrysts of spodumene and K-feldspar are often broken
and may be parallel to the pegmatite contact surface near borders, which might indicate
crystallization associated with deformation event(s) in the ECDZ or to internal stresses
generated by pegmatite crystallization.

Minerals 2022, 12, 981 4 of 21
Minerals 2022, 12, x 4 of 22
Figure 1. Simplified overview of the geology of the Leinster Terrane, south of the Iapetus suture,
southeast Ireland. The Iapetus suture is according to [27]. The Leinster Batholith is shown in both
overview (top left, inset) and the main map; major structures from the left: HSZ = Hollywood Shear
Zone, ECDZ = East Carlow Deformation Zone [28]; WFZ = Wicklow Fault Zone [31]; CTF =
Courtown–Tramore Fault [32]; BM = Ballycogly mylonites. Geological units from the 1:500,000
geological mapping shapefiles of Geological Survey Ireland.
3. Materials and Methods
The description of rock types and textures and samples collected to characterize
pegmatite bodies and country rocks were mostly carried out from in situ occurrences
intercepted by drill cores from the localities Aclare and Moylisha (Figure 2), part of the
ongoing exploration campaign of Blackstairs Lithium Ltd. since 2011. Additional work
was carried out on outcrops in the areas of Monaughrim, Moylisha, Graiguenamanagh
and Killiney Hill, as well as boulders located in Stranakelly, Moylisha, Monaughrim and
Aclare.
A detailed description was made of six drill cores of variable inclinations (45° to
vertical) with virtually complete recovery that intercepted shallow-dipping pegmatites
approximately perpendicular to contacts with country rocks, three from Aclare (6 cm
diameter) and three from Moylisha (4 cm diameter), that represent the bedrock
occurrences most enriched in spodumene (Figure 2).
Ninety-three representative samples were chosen for microscopic characterization
with a Nikon Eclipse LV100POL polarizing optical microscope, using transmitted light,
and a Hitachi TM-1000 scanning electron microscope in the School of Earth Sciences,
University College Dublin, Ireland. Backscattered electron (BSE) images were obtained
during electron microprobe work [18] using the Cameca SX 100 electron microprobe at
the Joint Laboratory of Electron Microscopy and Microanalysis of the Department of
Geological Sciences, Masaryk University, Brno, Czech Republic.
Figure 1. Simplified overview of the geology of the Leinster Terrane, south of the Iapetus suture,
southeast Ireland. The Iapetus suture is according to [27]. The Leinster Batholith is shown in
both overview (top left, inset) and the main map; major structures from the left: HSZ = Holly-
wood Shear Zone, ECDZ = East Carlow Deformation Zone [28]; WFZ = Wicklow Fault Zone [31];
CTF = Courtown–Tramore Fault [32]; BM = Ballycogly mylonites. Geological units from the 1:500,000
geological mapping shapefiles of Geological Survey Ireland.
3. Materials and Methods
The description of rock types and textures and samples collected to characterize
pegmatite bodies and country rocks were mostly carried out from in situ occurrences
intercepted by drill cores from the localities Aclare and Moylisha (Figure 2), part of the
ongoing exploration campaign of Blackstairs Lithium Ltd. since 2011. Additional work
was carried out on outcrops in the areas of Monaughrim, Moylisha, Graiguenamanagh and
Killiney Hill, as well as boulders located in Stranakelly, Moylisha, Monaughrim and Aclare.
A detailed description was made of six drill cores of variable inclinations (45◦ to
vertical) with virtually complete recovery that intercepted shallow-dipping pegmatites
approximately perpendicular to contacts with country rocks, three from Aclare (6 cm
diameter) and three from Moylisha (4 cm diameter), that represent the bedrock occurrences
most enriched in spodumene (Figure 2).
Ninety-three representative samples were chosen for microscopic characterization
with a Nikon Eclipse LV100POL polarizing optical microscope, using transmitted light,
and a Hitachi TM-1000 scanning electron microscope in the School of Earth Sciences,
University College Dublin, Ireland. Backscattered electron (BSE) images were obtained
during electron microprobe work [18] using the Cameca SX 100 electron microprobe at the

Minerals 2022, 12, 981 5 of 21
Joint Laboratory of Electron Microscopy and Microanalysis of the Department of Geological
Sciences, Masaryk University, Brno, Czech Republic.
Whole-rock geochemical analyses were obtained for pegmatites, hanging wall and
footwall (country rocks to pegmatite intrusions) as part of the exploration campaign. The
six drill cores were each split in half and divided into lithologically homogeneous parts,
between 7 cm and 3.05 m long, resulting in 272 samples varying between 200 g and 2 kg,
depending on interval length. These samples were then crushed, decomposed by four-acid
digestion and analyzed for 48 elements by ICP-MS by ALS Minerals (Loughrea, Co. Galway,
Ireland). Routine practices were used to ensure data quality control: sample duplicates
(1 in every 20 samples), homogeneous quartz pebbles (1/40) and certified standards (1/20).
Results showed reproducibility between duplicates within 15% for most elements and no
contamination problems. Detection limits for the elements analyzed ranged between 0.02
and 100 ppm.
The volumes of the samples analyzed are considered representative to estimate the
whole-rock geochemistry of pegmatite wall rocks and Leinster pegmatites, considering
their typical grain size around 2 cm and negligible variations in pegmatite mineralogy
among drill cores, boulders and outcrops of the same locality. It is assumed that the drill
core samples are representative of the pegmatite bodies from border to border and that
each pegmatite body crystallized from a single batch of magma [33].
Minerals 2022, 12, x 5 of 22
Whole-rock geochemical analyses were obtained for pegmatites, hanging wall and
footwall (country rocks to pegmatite intrusions) as part of the exploration campaign. The
six drill cores were each split in half and divided into lithologically homogeneous parts,
between 7 cm and 3.05 m long, resulting in 272 samples varying between 200 g and 2 kg,
depending on interval length. These samples were then crushed, decomposed by four-
acid digestion and analyzed for 48 elements by ICP-MS by ALS Minerals (Loughrea, Co.
Galway, Ireland). Routine practices were used to ensure data quality control: sample
duplicates (1 in every 20 samples), homogeneous quartz pebbles (1/40) and certified
standards (1/20). Results showed reproducibility between duplicates within 15% for most
elements and no contamination problems. Detection limits for the elements analyzed
ranged between 0.02 and 100 ppm.
The volumes of the samples analyzed are considered representative to estimate the
whole-rock geochemistry of pegmatite wall rocks and Leinster pegmatites, considering
their typical grain size around 2 cm and negligible variations in pegmatite mineralogy
among drill cores, boulders and outcrops of the same locality. It is assumed that the drill
core samples are representative of the pegmatite bodies from border to border and that
each pegmatite body crystallized from a single batch of magma [33].
Figure 2. Location of drill collars studied in (A) Aclare and (B) Moylisha. Both areas represented are
within the ECDZ. Geological units from the 1:500,000 geological mapping shapefiles of Geological
Survey Ireland. Whit Star—Spodumene pegmatites.
4. Results
4.1. Mineralogical and Petrographic Features
A full description of the pegmatites and wall rocks is provided by [18] and
summarized below. Spodumene pegmatites in Leinster are unzoned with spodumene
present from contacts to the center of the intrusion or weakly zoned with a quartz core.
Intrusions are mostly dominated by the early primary assemblage composed of medium-
to-coarse-grained spodumene, quartz, K-feldspar, albite, muscovite, garnet (Figure 3A)
and a variety of accessory phases, such as Mn-bearing fluorapatite, sphalerite and
cassiterite. Spodumene occurs as large subhedral prisms or laths from a few mm to tens
Figure 2. Location of drill collars studied in (A) Aclare and (B) Moylisha. Both areas represented are
within the ECDZ. Geological units from the 1:500,000 geological mapping shapefiles of Geological
Survey Ireland. White stars as in Figure 1.
4. Results
4.1. Mineralogical and Petrographic Features
A full description of the pegmatites and wall rocks is provided by [18] and summarized
below. Spodumene pegmatites in Leinster are unzoned with spodumene present from
contacts to the center of the intrusion or weakly zoned with a quartz core. Intrusions
are mostly dominated by the early primary assemblage composed of medium-to-coarse-
grained spodumene, quartz, K-feldspar, albite, muscovite, garnet (Figure 3A) and a variety
of accessory phases, such as Mn-bearing fluorapatite, sphalerite and cassiterite. Spodumene

Minerals 2022, 12, 981 6 of 21
occurs as large subhedral prisms or laths from a few mm to tens of cm. The lack of intrusion
scale of the geochemical and mineralogical zonation suggests early-stage Li saturation in
the pegmatite melts [18].
3D). Albitization tends to be stronger downwards across spodumene pegmatite
intersections. Albitite is recognized as a replacive late primary mineral assemblage at the
final stages of pegmatite crystallization [18,19], as it both overgrows and partially replaces
the primary minerals of the spodumene intervals. It consists of albite crystals (~90%), often
aligned where they occur in larger volumes, with minor muscovite and accessory garnet,
apatite, beryl, cassiterite and columbite-group minerals. Variable alterations of
spodumene to fine-grained mica and the resorption of K-feldspar are frequent and often
only relics or pseudomorphs can be observed (Figure 3C,D). Large albitized spodumene
and F-rich apatite crystals often result in a vermicular habit, though elsewhere, only the
rims of these crystals are consumed. Particularly in Moylisha, interstitial and fracture-
filling lithiophilite and polylithionite rims in muscovite are common in the albitite.
Figure 3. Representative textures indicating the internal evolution of spodumene pegmatites in
Aclare; the same evolution is observed in Moylisha. Mineral abbreviations: Ab = albite, Coltan =
columbite-tantalite group minerals, Grt = garnet, Kfs = K-feldspar, Ms = muscovite, Qz = quartz, Sp
= sphalerite, Spd = spodumene. (A) Typical early primary assemblage with no albitization. (B) Early
primary assemblage with patches of late primary albitite. (C) Interconnected albitite patches with
visible alteration of early primary assemblage. (D) Predominant late primary albitite with relics of
spodumene, quartz and muscovite. Extent of albitization is represented by white dashed lines. Scale
bar is valid for all images.
The hanging wall of the uppermost Aclare spodumene pegmatite is the Ribband
Group’s Maulin Formation (Figure 2) consisting of garnet, staurolite and andalusite-
bearing mica schists. A lens of undifferentiated foliated granodiorite forms the footwall
of the uppermost intersections and fully encloses deeper Aclare pegmatites (Figure 2).
Moylisha pegmatites are hosted in the margin of the Tullow Lowlands pluton (Figure 2),
characterized by porphyritic granodiorite. Contacts with wall rocks are typically sharp
and vary from irregular to subparallel to the regional foliation [18]. Spodumene pegmatite
exocontacts in all country rock types are characterized by visibly altered zones containing
a higher concentration of mafic minerals; the thickness of these zones varies from 2 to 20
cm (Figure 4).
Figure 3. Representative textures indicating the internal evolution of spodumene pegmatites
in Aclare; the same evolution is observed in Moylisha. Mineral abbreviations: Ab = albite,
Coltan = columbite-tantalite group minerals, Grt = garnet, Kfs = K-feldspar, Ms = muscovite,
Qz = quartz, Sp = sphalerite, Spd = spodumene. (A) Typical early primary assemblage with no
albitization. (B) Early primary assemblage with patches of late primary albitite. (C) Interconnected
albitite patches with visible alteration of early primary assemblage. (D) Predominant late primary
albitite with relics of spodumene, quartz and muscovite. Extent of albitization is represented by white
dashed lines. Scale bar is valid for all images.
The volume of fine-grained albitite, common in spodumene pegmatites, varies through-
out intrusions, from isolated to interconnected patches (Figure 3B,C) and occasionally in
intervals of tens of cm dominated by the fine-grained assemblage (Figure 3D). Albitization
tends to be stronger downwards across spodumene pegmatite intersections. Albitite is
recognized as a replacive late primary mineral assemblage at the final stages of pegmatite
crystallization [18,19], as it both overgrows and partially replaces the primary minerals of
the spodumene intervals. It consists of albite crystals (~90%), often aligned where they
occur in larger volumes, with minor muscovite and accessory garnet, apatite, beryl, cassi-
terite and columbite-group minerals. Variable alterations of spodumene to fine-grained
mica and the resorption of K-feldspar are frequent and often only relics or pseudomorphs
can be observed (Figure 3C,D). Large albitized spodumene and F-rich apatite crystals often
result in a vermicular habit, though elsewhere, only the rims of these crystals are consumed.
Particularly in Moylisha, interstitial and fracture-filling lithiophilite and polylithionite rims
in muscovite are common in the albitite.
The hanging wall of the uppermost Aclare spodumene pegmatite is the Ribband
Group’s Maulin Formation (Figure 2) consisting of garnet, staurolite and andalusite-bearing
mica schists. A lens of undifferentiated foliated granodiorite forms the footwall of the
uppermost intersections and fully encloses deeper Aclare pegmatites (Figure 2). Moylisha
pegmatites are hosted in the margin of the Tullow Lowlands pluton (Figure 2), characterized
by porphyritic granodiorite. Contacts with wall rocks are typically sharp and vary from
irregular to subparallel to the regional foliation [18]. Spodumene pegmatite exocontacts
in all country rock types are characterized by visibly altered zones containing a higher

Minerals 2022, 12, 981 7 of 21
concentration of mafic minerals; the thickness of these zones varies from 2 to 20 cm
(Figure 4).
by aligned micas and quartz elongation surrounding oligoclase phenocrysts (>1 cm)
(Figure 5C). The Aclare spodumene pegmatite exocontact in granodiorite is less
pronounced than in schist (Figure 4B); medium-grained (1 to 2 mm) radiating tourmaline
“poikiloblasts” (Figure 5D) and light red siderophyllite are present. The porphyritic
granodiorite has abundant microcline megacrysts that may carry fine-grained oligoclase
inclusions and occasional inclusions of biotite and myrmekite. In Moylisha, this rock may
be foliated, with preserved K-feldspar megacrysts (Figure 5E). The Moylisha spodumene
pegmatite exocontact is also less pronounced than in schist (Figure 4C), notably
characterized by the presence of tourmaline (Figure 5F).
Figure 4. Exocontacts of spodumene pegmatites in the three country rock types. Mineral
abbreviations: Ab = albite, Sid = siderophyllite, Spd: spodumene, Tur = tourmaline. (A) Hanging
wall mica schist with a 15 cm zone of tourmaline and siderophyllite enrichment just above the
spodumene pegmatite top contact, drill hole ACL 13-02. (B) Footwall foliated granodiorite with 5
cm zone enriched in siderophyllite adjacent to spodumene pegmatite bottom contact; note
tourmaline-rich vein further from the contact, drill hole ACL 13-02. (C) Hanging wall porphyritic
granodiorite with 10 cm zone enriched in siderophyllite just above spodumene pegmatite top
contact, drill hole MOY 13-03.
Figure 4. Exocontacts of spodumene pegmatites in the three country rock types. Mineral abbrevia-
tions: Ab = albite, Sid = siderophyllite, Spd: spodumene, Tur = tourmaline. (A) Hanging wall mica
schist with a 15 cm zone of tourmaline and siderophyllite enrichment just above the spodumene
pegmatite top contact, drill hole ACL 13-02. (B) Footwall foliated granodiorite with 5 cm zone
enriched in siderophyllite adjacent to spodumene pegmatite bottom contact; note tourmaline-rich
vein further from the contact, drill hole ACL 13-02. (C) Hanging wall porphyritic granodiorite with
10 cm zone enriched in siderophyllite just above spodumene pegmatite top contact, drill hole MOY
13-03.
Maulin Formation mica schists are dominated by bands of biotite (commonly altered
to chlorite), muscovite and quartz, commonly with porphyroblasts of staurolite, garnet
and andalusite (e.g., Figure 5A). Within the spodumene pegmatite exocontact (Figure 4A),
the schist is mainly composed of light pink siderophyllite, pleochroic brown tourmaline
(ranging between schorl and dravite) with darker rims, quartz and accessories including
apatite, beryl (Figure 5B) and ilmenite. The foliated granodiorite has its foliation de-
fined by aligned micas and quartz elongation surrounding oligoclase phenocrysts (>1 cm)
(Figure 5C). The Aclare spodumene pegmatite exocontact in granodiorite is less pronounced
than in schist (Figure 4B); medium-grained (1 to 2 mm) radiating tourmaline “poikiloblasts”
(Figure 5D) and light red siderophyllite are present. The porphyritic granodiorite has
abundant microcline megacrysts that may carry fine-grained oligoclase inclusions and
occasional inclusions of biotite and myrmekite. In Moylisha, this rock may be foliated,
with preserved K-feldspar megacrysts (Figure 5E). The Moylisha spodumene pegmatite
exocontact is also less pronounced than in schist (Figure 4C), notably characterized by the
presence of tourmaline (Figure 5F).
4.2. Whole-Rock Geochemistry
Leinster pegmatites have complex textures (e.g., Figure 3) and variable compositions
within sampled intervals, which brings challenges for whole-rock geochemical characteri-

Minerals 2022, 12, 981 8 of 21
zation. Based on previous work [16,18,33], it is estimated that the main components, Si and
Al, show similar variations between non-albitized and albitized spodumene pegmatites,
with SiO2 between 67 and 73 wt.% and Al2O3 between 17 and 22.9 wt.%; Fe and Li are
major elements in spodumene pegmatites (up to 3.84 wt.% Fe2O3 and 4.28 wt.% Li2O),
but much less abundant in albitite (<0.3 wt.% Fe2O3 and <0.01 wt.% Li2O); Na is more
abundant in albitite (8.53–11.56 wt.%) than in spodumene pegmatite (1–3.2 wt.% NaO).
Minerals 2022, 12, x 8 of 22
Figure 5. Mineralogy and textures in wall rocks. Mineral abbreviations: And = andalusite, Brl =
beryl, Bt = biotite, Kfs = K-feldspar, Ms = muscovite, Pl = plagioclase, Qz = quartz, Sid =
siderophyllite, Tur = tourmaline; samples from drill holes in parentheses. (A) Inclusion-rich
andalusite porphyroblasts enveloped by aligned muscovite in mica schist (ACL 13-02). (B) Medium-
grained light brown tourmaline crystals with dark brown rims within light pink siderophyllite,
beryl and quartz in spodumene pegmatite exocontact in mica schist (ACL 13-02), 2 cm away from
the contact with spodumene pegmatite. (C) Zoned plagioclase megacryst with inclusion-rich core
and clear rim with irregular borders, within aligned biotite and muscovite crystals in foliated
granodiorite (ACL 13-04). (D) Radiating tourmaline “poikiloblast” adjacent to quartz and zoned
plagioclase in footwall granodiorite exocontact to spodumene pegmatite (ACL 13-04), 2.5 cm away
from the contact with spodumene pegmatite. (E) Microcline megacryst in porphyritic granodiorite
(MOY 13-03). (F) Tourmaline crystals in spodumene pegmatite exocontact in porphyritic
granodiorite (MOY 13-03), 3 cm away from the contact with spodumene pegmatite.
4.2. Whole-Rock Geochemistry
Leinster pegmatites have complex textures (e.g., Figure 3) and variable compositions
within sampled intervals, which brings challenges for whole-rock geochemical
characterization. Based on previous work [16,18,33], it is estimated that the main
components, Si and Al, show similar variations between non-albitized and albitized
Figure 5. Mineralogy and textures in wall rocks. Mineral abbreviations: And = andalusite,
Brl = beryl, Bt = biotite, Kfs = K-feldspar, Ms = muscovite, Pl = plagioclase, Qz = quartz,
Sid = siderophyllite, Tur = tourmaline; samples from drill holes in parentheses. (A) Inclusion-rich
andalusite porphyroblasts enveloped by aligned muscovite in mica schist (ACL 13-02). (B) Medium-
grained light brown tourmaline crystals with dark brown rims within light pink siderophyllite, beryl
and quartz in spodumene pegmatite exocontact in mica schist (ACL 13-02), 2 cm away from the
contact with spodumene pegmatite. (C) Zoned plagioclase megacryst with inclusion-rich core and
clear rim with irregular borders, within aligned biotite and muscovite crystals in foliated granodiorite
(ACL 13-04). (D) Radiating tourmaline “poikiloblast” adjacent to quartz and zoned plagioclase in
footwall granodiorite exocontact to spodumene pegmatite (ACL 13-04), 2.5 cm away from the contact
with spodumene pegmatite. (E) Microcline megacryst in porphyritic granodiorite (MOY 13-03).
(F) Tourmaline crystals in spodumene pegmatite exocontact in porphyritic granodiorite (MOY 13-03),
3 cm away from the contact with spodumene pegmatite.

Minerals 2022, 12, 981 9 of 21
Whole-rock concentrations for a series of relevant major and mostly trace elements in
Aclare and Moylisha pegmatite and country rock samples are presented as Supplementary
Table S1 and summarized in Table 1. In Aclare drill cores (Figure 6A–C), foliated granodior-
ite and mica schist have concentrations within a factor of twenty when compared to the
upper continental crust (UCC) [34]. In the foliated granodiorite, enrichment in Li, Cs, Sn,
Be, U and Pb and depletion in Ni, Hf and Zr is observed, while the schist is enriched in Li,
Cs, Sn, Zn, Mn and Pb and depleted in Sr, Na and Ca. The samples of both rock types up
to 1.5 m away from spodumene pegmatites contacts contain 10 to 200 times higher Li, Cs,
Sn, Rb and Be, and lesser Ta enrichment, compared to UCC. In schist, enrichment in Zn
and Pb is also observed in the halo. Li and Cs enrichment in schist may extend beyond the
sampling limit of 6 m above the spodumene pegmatite contact.
Minerals 2022, 12, x 11 of 22
Figure 6. Whole-rock concentrations of elements of interest normalized against the upper
continental crust (UCC; values from [34]) for the Aclare drill cores (A) ACL 13-02, (B) ACL 13-04
and (C) ACL 13-05.
Figure 6. Whole-rock concentrations of elements of interest normalized against the upper continental
crust (UCC; values from [34]) for the Aclare drill cores (A) ACL 13-02, (B) ACL 13-04 and (C) ACL
13-05.

Minerals 2022, 12, 981 10 of 21
Table 1. Summary of whole-rock analyses of pegmatites and country rocks.
Aclare
Mica Schist (n = 10)
Foliated Granodiorite
(n = 28)
Spodumene Pegmatite,
Primary Assemblage
(n = 43)
Albitized Spodumene
Pegmatite (n = 30)
mean min max mean min max mean min max mean min max
Al wt.% 0.01 2% 8.42 7.11 9.65 7.69 7.28 8.34 7.02 6.26 7.95 6.62 4.28 8.14
Be ppm 0.05 3% 7.3 2.4 43.1 10.8 2.6 42.9 142.1 60.6 284.0 143.1 20.0 271.0
Ca wt.% 0.01 2% 0.31 0.20 0.53 1.44 0.69 2.09 0.15 0.04 0.57 0.30 0.02 2.67
Cs ppm 0.05 4% 124.2 8.0 1000 247.1 11.6 1000 85.2 32.9 264.0 80.4 6.6 418.0
Fe wt.% 0.01 1% 4.84 4.08 6.07 2.00 1.65 2.28 0.45 0.21 0.66 0.38 0.15 0.78
Hf ppm 0.1 2% 2.9 2.3 3.7 1.3 1.0 1.6 1.3 0.3 3.0 1.7 0.3 3.4
K wt.% 0.01 2% 2.52 1.88 2.79 1.85 1.42 3.17 1.64 0.49 4.89 1.96 0.29 5.58
Li ppm 0.2 3% 514.2 105.0 2420 692.2 175.5 2870 8824 98.8 19,700 506.5 15.2 2470
Mn ppm 5 2% 782 437 2480 538 358 1030 947 151 2100 643 77 3300
Mo ppm 0.05 12% 2.7 1.4 4.0 0.7 0.5 0.9 0.1 0.1 0.1 0.1 0.1 0.1
Na wt.% 0.01 1% 1.04 0.63 1.21 2.92 1.94 3.39 2.31 0.88 5.81 4.03 1.32 6.78
Nb ppm 0.1 6% 13.6 12.1 15.4 7.8 5.1 19.2 31.3 12.7 80.5 30.5 11.1 109.5
Ni ppm 0.2 8% 43.8 32.2 53.1 10.5 8.6 12.0 2.8 1.2 5.0 1.9 1.1 3.2
P ppm 10 4% 502 330 1310 741 400 2050 690 210 2550 852 170 2310
Pb ppm 0.5 6% 47.6 9.4 211.0 21.3 11.3 77.8 8.9 2.4 58.4 18.6 2.3 70.0
Rb ppm 0.1 4% 299.4 121.0 1580 501.4 118.5 2240 623.7 208.0 2100 615.1 72.1 1590
Sc ppm 0.1 3% 18.0 15.1 20.4 6.2 5.3 6.8 0.2 0.1 0.9 0.2 0.1 0.7
Sn ppm 0.2 4% 25.4 2.7 208.0 50.8 3.6 225.0 81.3 34.2 158.5 54.2 7.7 123.0
Sr ppm 0.2 2% 102.7 89.5 124.5 230.0 139.5 323.0 16.8 2.9 42.9 20.3 3.7 76.7
Ta ppm 0.05 5% 1.16 0.80 2.91 3.89 0.44 23.30 29.80 5.43 55.10 42.54 4.64 402.0
Th ppm 0.2 8% 10.3 7.9 12.0 4.8 4.0 5.9 0.6 0.2 3.1 0.9 0.2 3.1
Tl ppm 0.02 2% 1.72 0.57 9.79 3.31 0.58 14.00 4.30 1.27 16.55 4.25 0.33 16.25
U ppm 0.1 3% 3.2 2.2 3.9 2.1 1.4 4.2 6.1 1.6 13.5 8.1 0.7 25.5
W ppm 0.1 3% 2.6 1.7 3.5 0.8 0.2 3.0 0.3 0.1 1.5 0.5 0.1 0.9
Y ppm 0.1 7% 15.9 10.9 21.6 6.5 4.9 8.7 0.4 0.1 2.0 0.8 0.1 3.9
Zn ppm 2 2% 221 70 862 98 51 372 55 18 163 101 18 303
Zr ppm 0.5 5% 98.8 80.7 131.0 37.0 31.8 42.5 10.3 1.4 23.2 15.3 1.3 42.8
Moylisha
Porphyritic Granodiorite
(n = 77)
Simple Pegmatite
(n = 42)
Spodumene Pegmatite,
Primary Assemblage
(n = 19)
Albitized Spodumene
Pegmatite (n = 23)
mean min max mean min max mean min max mean min max
Al wt.% 0.01 2% 7.49 6.68 10.5 6.95 4.32 10.2 6.72 6.14 7.61 6.12 0.89 7.47
Be ppm 0.05 3% 13.5 4.5 103.0 48.9 4.5 285.0 153.0 95.1 218.0 126.8 1.6 262.0
Ca wt.% 0.01 2% 1.19 0.71 1.54 0.39 0.11 1.42 0.10 0.05 0.30 0.13 0.01 0.31
Cs ppm 0.05 4% 64.0 9.8 343.0 44.4 14.2 226.0 75.4 49.3 115.5 57.0 15.9 143.5
Fe wt.% 0.01 1% 1.72 1.22 2.00 0.65 0.31 1.21 0.39 0.27 0.56 0.28 0.17 0.50
Hf ppm 0.1 2% 2.9 1.9 4.7 1.5 0.2 10.0 2.1 0.9 4.1 2.1 0.2 4.8
K wt.% 0.01 2% 2.90 1.54 4.67 3.18 1.58 5.00 2.28 0.82 3.82 2.23 0.64 4.95
Li ppm 0.2 3% 608.4 287.0 2560 258.1 80.2 1540 5500 239.0 12,750 340.1 63.2 1390
Mn ppm 5 2% 624 406 2530 916 159 5990 907 539 1340 681 44 1520
Mo ppm 0.05 12% 0.6 0.1 14.4 0.8 0.1 10.4 0.1 0.1 0.3 0.3 0.1 1.5
Na wt.% 0.01 1% 2.61 0.69 3.14 2.81 0.98 5.26 2.79 1.10 4.67 4.00 0.13 6.32
Nb ppm 0.1 6% 8.9 5.8 59.2 12.5 4.5 48.1 27.9 10.7 72.6 37.0 3.3 119.5
Ni ppm 0.2 8% 6.4 4.0 8.5 2.6 1.1 4.9 2.6 1.4 4.6 2.5 0.7 16.2
P ppm 10 4% 961 540 7000 779 190 7240 526 270 1180 480 90 1580
Pb ppm 0.5 6% 28.8 8.1 36.3 24.4 6.8 46.3 16.5 7.4 29.6 17.9 5.5 40.7
Rb ppm 0.1 4% 321.6 175.5 1360 402.5 224.0 1400 657.5 255.0 1300 478.5 176.0 1270
Sc ppm 0.1 3% 4.5 2.8 5.5 1.0 0.2 3.0 0.1 0.1 0.7 0.1 0.1 0.3
Sn ppm 0.2 4% 34.9 5.5 430.0 56.9 18.2 395.0 61.6 36.1 78.3 28.6 1.9 45.1
Sr ppm 0.2 2% 153.9 40.9 194.5 38.9 17.4 87.0 12.3 5.5 27.8 20.0 4.1 77.7
Ta ppm 0.05 5% 2.28 0.65 40.40 7.29 1.28 89.00 26.48 9.06 85.90 37.91 0.88 99.50
Th ppm 0.2 8% 11.4 6.5 14.4 3.3 0.4 26.0 2.3 0.9 4.1 2.9 0.2 7.5
Tl ppm 0.02 2% 1.89 1.00 9.15 2.34 1.08 8.38 4.56 1.43 10.05 3.32 0.87 12.15
U ppm 0.1 3% 4.9 1.8 15.6 6.5 0.8 25.6 6.3 1.5 16.8 5.8 1.7 10.5
W ppm 0.1 3% 0.9 0.2 5.8 1.1 0.2 4.6 0.3 0.1 0.4 0.4 0.1 0.6
Y ppm 0.1 7% 8.2 5.6 9.6 4.5 0.6 22.7 0.2 0.1 1.0 0.7 0.1 5.6
Zn ppm 2 2% 91 56 301 46 14 215 79 32 144 65 4 125
Zr ppm 0.5 5% 97.6 58.0 120.5 26.2 3.5 102.5 13.4 4.7 28.1 13.3 1.0 29.9
Bold = detection limits; italicized = mean relative standard deviation of analyses. Complete analyses in
Supplementary Table S1.
At the same locality, spodumene-bearing intervals in pegmatites have up to 1000 times
more Li, and around 100 times more Cs, Be, Sn, Ta and Rb, than country rocks. They
are depleted in W, Fe, Ni, Th, Y, Sr and Ca, a signature common to albite-spodumene
pegmatites elsewhere, e.g., [35–37]. There is a large variation in Li, Cs, Sn, Rb, Zn, K, Nb and
Y concentrations among different pegmatite samples, which may primarily be explained
by variations in the proportions of spodumene and K-feldspar (primary assemblage) and
minor phases such as sphalerite and columbite-tantalite group minerals in albitite (late

Minerals 2022, 12, 981 11 of 21
primary assemblage). Samples dominated by the primary assemblage have the highest
Li, mostly >100 times UCC; samples dominated by the late primary assemblage show
enrichment in Be, Ta, Nb and Y, but a major depletion in Li, when compared to the primary
assemblage (e.g., Figure 6C). The quartz-feldspar core zone of ACL 13-04 presents a similar
trend to the albitite, with around 100 times less Li when compared to spodumene-bearing
samples (Figure 6B).
In Moylisha drill cores (Figure 7A–C), the porphyritic granodiorite shows a similar
pattern to the foliated granodiorite: enrichment of up to 30 times UCC in Li and Sn, up to
10 times UCC in Cs, Be, Rb, Ta and U, and a depletion down to 0.1 times UCC in W and Ni.
Granodiorite adjacent to spodumene pegmatites, up to 2 m from contacts, shows Li, Cs, Ta,
Sn, Be and Rb from 10 to 100 times UCC. Peaks of Be and Sn concentrations in granodiorite
samples distant from spodumene pegmatites are also observed (e.g., Figure 7B) and could
result from interactions with simple pegmatites.
Minerals 2022, 12, x 12 of 22
Figure 7. Whole-rock concentrations of elements of interest normalized against the upper
continental crust (UCC; values from [34]) for the Moylisha drill cores (A) MOY 13-01, (B) MOY 13-
02 and (C) MOY 13-03.
4.3. Characterization of Exomorphic Halos
An enrichment in many incompatible elements is observed in spodumene pegmatite
exocontacts in the three different country rock types. The elements Li, Cs, Ta, Rb, Be and
Figure 7. Whole-rock concentrations of elements of interest normalized against the upper continental
crust (UCC; values from [34]) for the Moylisha drill cores (A) MOY 13-01, (B) MOY 13-02 and
(C) MOY 13-03.

Minerals 2022, 12, 981 12 of 21
Moylisha spodumene pegmatites have up to 600 times more Li than UCC, along with
elevated Be, Rb, Sn and Ta (up to 100 times UCC). As with Aclare spodumene pegmatites,
they are depleted in W, Fe, Ni, Y, Zr, Sn and Ca. Albitized spodumene pegmatites are
depleted in Li, but are not significantly different in Be, Ta, Nb and Sn concentrations, com-
pared to unalbitized spodumene pegmatites. Simple pegmatites present some enrichment
in Li, Be, Sn, Cs and Rb (around 3 to 10 times UCC, with Be reaching around 80 times UCC)
and depletion in Sr, Ba, Hf, Zr and Y, similar to, but less pronounced than in, spodumene
pegmatites.
4.3. Characterization of Exomorphic Halos
An enrichment in many incompatible elements is observed in spodumene pegmatite
exocontacts in the three different country rock types. The elements Li, Cs, Ta, Rb, Be and Sn
show the most noticeable exomorphic halo effect, with the most significant enrichments
in country rocks closest to spodumene pegmatites, as shown in the drill core geochemical
profiles (Figures 8 and 9). At Aclare (Figure 8), the mica schist shows pronounced concentra-
tion peaks of all these elements adjacent to the upper spodumene pegmatite contact, even
where a direct contact was not preserved in the drill core (e.g., Figure 8B). This halo effect
is also observed in the foliated granodiorite in the footwall, although the enrichment is
less pronounced. Foliated granodiorite xenoliths in spodumene pegmatites, when present,
show enrichment in Cs, Rb and Be compared to the parent granitic rock. At Moylisha
(Figure 9), the halo effect is less pronounced, likely due to the less permeable and/or less
reactive nature of the wall rock (porphyritic granodiorite) and the complexity imposed by
several simple pegmatite intrusions; however, elevated Li and Cs concentrations in the
hanging wall of spodumene pegmatites can be identified (most clearly in Figure 9C).
Table 2 presents an approximate quantification of the concentrations of elements lost
from pegmatite magma to the exomorphic halo for Li, Be, Sn, Ta, Cs and Rb. This is
estimated through data in Supplementary Table S1 following three steps: (1) identifying
the lowest concentrations of the elements in wall rocks within 20 m of a contact with a
spodumene pegmatite to obtain the approximate composition prior to pegmatite emplace-
ment (or “background”); for the drill core MOY 13-01, the distance interval from contact
considered was 10 m due to the small thickness of the spodumene pegmatites; (2) estimat-
ing the total weights of the elements in the halos by summing all the wall rock sampled
intervals, weighted by interval length, with the background subtracted; (3) estimating the
total pre-halo pegmatite weights by similarly summing all pegmatite and halo intervals.
Differences in rock density are ignored, which provides a limitation to our calculations.
However, the relative differences in specific gravity are unlikely to exceed 10% between
spodumene pegmatite and mica schist and 5% between spodumene pegmatite and granite.
The spreadsheet with calculations is presented as Supplementary Table S2. For these cal-
culations, all simple pegmatite intervals in Moylisha drill cores, the boulder at the top of
the drill core MOY 13-01 and the wall rock xenoliths in ACL 13-02 and ACL 13-05 were
excluded, so that the calculation of the halo element inventories would be conservative; if
simple pegmatites were intruded before spodumene pegmatites and lay within spodumene
pegmatite halos, halo inventories would be slightly larger than calculated. Halo inventories
may also be larger if halos were wider than covered by the analyzed samples, which were
located within the maximum 20 m interval of available core length.
The estimated amount of Li lost from the spodumene pegmatites ranges from 2%
to 12%; the smallest Li loss is observed in drill core ACL 13-04, which has the thickest
zoned pegmatite, and the largest Li loss is observed in drill core MOY 13-03, where the
intervals dominated by late primary albitite are most frequent (see Figure 7C). The estimated
amounts of Be and Ta in the halos also represent no more than 7% of the pre-halo pegmatite
inventory. Larger proportions of Sn, Rb and Cs were lost to the exomorphic halos: estimates
range from 10% to 43% for Sn, 6% to 24% for Rb and 17% to 63% for Cs.

Minerals 2022, 12, 981 13 of 21
22, 12, x 14 of 22
Figure 8. Geochemical profiles for Aclare drill cores (A) ACL 13-02, (B) ACL 13-04 and (C) ACL 13-
05. A 30-cm-wide spodumene pegmatite intrusion is omitted in (B). Drill holes intercepted
pegmatites at ~90°.
Figure 8. Geochemical profiles for Aclare drill cores (A) ACL 13-02, (B) ACL 13-04 and (C) ACL 13-05. A
30-cm-wide spodumene pegmatite intrusion is omitted in (B). Drill holes intercepted pegmatites at ~90◦.

Minerals 2022, 12, 981 14 of 21
022, 12, x 15 of 22
Figure 9. Geochemical profiles for Moylisha drill cores (A) MOY 13-01, (B) MOY 13-03 and (C) MOY
13-03. Drill holes intercepted pegmatites at ~90°.
Figure 9. Geochemical profiles for Moylisha drill cores (A) MOY 13-01, (B) MOY 13-03 and (C) MOY
13-03. Drill holes intercepted pegmatites at ~90◦.

Minerals 2022, 12, 981 15 of 21
Table 2. Estimated mean concentrations (ppm) of key elements in the exomorphic halos, weighted by
drill hole interval length.
Drill
Core
Element (ppm)
Total
(SP + Wall Rocks)
Total
(Wall Rocks Only)
% of Element
in Halo
ACL 13-02
Li 3881 189 5%
Cs 126 48 38%
Ta 25 2 7%
Rb 744 103 14%
Be 149 4 3%
Sn 79 17 22%
ACL 13-04
Li 9840 171 2%
Cs 129 55 43%
Ta 27 1 3%
Rb 672 78 12%
Be 134 3 2%
Sn 94 9 10%
ACL 13-05
Li 4021 134 3%
Cs 227 144 63%
Ta 41 2 4%
Rb 671 78 12%
Be 172 2 1%
Sn 71 9 13%
MOY 13-01
Li 3501 216 6%
Cs 109 31 28%
Ta 23 1 3%
Rb 758 77 10%
Be 150 6 4%
Sn 60 14 23%
MOY 13-02
Li 4138 113 3%
Cs 86 14 17%
Ta 35 1 2%
Rb 672 41 6%
Be 170 8 5%
Sn 60 9 15%
MOY 13-03
Li 1503 187 12%
Cs 100 48 48%
Ta 43 1 3%
Rb 563 138 24%
Be 137 10 7%
Sn 62 26 43%
SP = spodumene pegmatites. Totals calculated exclude background. Full detailing of calculations in
Supplementary Table S2.
5. Discussion
5.1. Pegmatite-Country Rock Interactions and Exomorphic Halo Formation
The metasomatism of wall rocks has been well studied around a variety of types of
granitic intrusions and related ore deposits (e.g., [38–40]). Chemical changes and often
recognizable mineral assemblages are developed, mostly following an alkalic to argillic
sequence that represents the increasing activity of H+ ions in the system as it evolves
to lower temperatures and pressures [6]. This process has been linked to the fracture-
controlled expulsion of highly reactive hydrothermal saline and water-/vapor-rich fluids
that build up during magmatic evolution [41,42]. It is not uncommon that late-stage
magmatic fluids are also carriers of various elements of economic interest, so exomorphic
halos and ore deposits could be frequently linked.
Wall-rock halos formed by hydrothermal alterations can range from decimeter to
meter scales in Sn-W deposits (e.g., [43]) and up to kilometer scale alteration zones in
porphyry deposits (e.g., [44]). Studies on halos around evolved pegmatites [8,11,12,14]
have identified replacive metasomatic aureoles of a few to tens of meters into different types
of host rocks, which may enclose the pegmatite body almost continuously. Concentrations
of Li, Rb and Cs above the background in the metamorphosed volcanic country rock of a
lithium pegmatite dike were detected up to 150 m away from the contact [45].

Minerals 2022, 12, 981 16 of 21
The crystallization of tourmaline and/or rare element-bearing micas are commonly
described in lithium pegmatite wall rocks, e.g., [13,46,47]. In Leinster, the presence of tour-
maline in spodumene pegmatite wall rock schists of the Ribband Group has already been
described [17]. Moreover, the existence of exomorphic halos around Leinster pegmatites
has previously been inferred from soil enrichment in Li, Rb, Ba, Sr, Cu, Zn, Pb and Sn above
spodumene pegmatites, with concentrations up to double that in soil above more distal
granitic or metasedimentary rocks [48].
Exomorphic halos identified around Leinster spodumene pegmatites in this study
are characterized by enrichment in Li, Rb, Be and especially Cs, as well as the high-field-
strength elements Ta and Sn, in both mica schist and granitic rocks near contacts with the
pegmatites (Figure 10A). The geochemical signature of the exomorphic halos partly matches
the overall signature of albitite (e.g., increased Be and Rb linked to the crystallization of
beryl and siderophyllite in halos), but contrasts with the signatures of Li, Cs, Sn and Ta,
which are depleted in albitite when compared to halos (e.g., Figures 6A and 7B). Halo
enrichment in B can also be inferred from the formation of tourmaline in spodumene
pegmatite exocontacts (e.g., Figure 5B,D,F); since tourmaline is rare in the pegmatites, it is
assumed that B was present, but not saturated, throughout pegmatite crystallization [18].
It is proposed that halos are associated with albitite crystallization and were, therefore,
formed after the crystallization of coarse-grained pegmatite crystals. Consequently, even
though the studied drill core geochemical profiles may fail to reveal some three-dimensional
variation, halo chemistry is qualitatively consistent with mineralogical and textural features
in all drill cores analyzed.
Minerals 2022, 12, x 18 of 22
exocontact samples. A systematic analysis has not yet been done for granitic country
rocks, but Rb2O and Cs2O in exocontacts in granite are detectable at concentrations of
around 0.4 wt.% and 0.15 wt.%, respectively. Individual quantitative SEM-EDS point
analyses (following the method described in [19]) of dark mica in granodiorite within 1 m
of the spodumene pegmatite contact at Aclare yielded up to 0.9% wt.% Rb2O and 1.9%
wt.% Cs2O.
In Leinster, the fluid’s geochemical composition (B, H2O) seems to have controlled
the partitioning of Li, Rb, Be, Sn and Ta, and have been an cause of the especially strong
partitioning of Cs, into the fluid and, consequently, to the halos, which supports some
previous findings [48]. The presence of meter-scale exomorphic halos of alkali elements
and fluxes is in accordance with halos described around spodumene pegmatites
elsewhere [8,9,53,54]. However, evidence for the mobilization of Ta has not been
previously described in pegmatite halos. It is also important to note that the percentage of
elements in halos (Table 2) in this pegmatitic system can reach over 5% for Ta and Be, over
10% for Li and Rb and over 40% for Cs and Sn, which has major implications for the
estimation of pegmatite starting compositions for geochemical modeling, especially when
the minerals in which some of these elements are essential are absent from pegmatites, as
is the case in Leinster for B and Cs. Existing pegmatite concentrations of these elements
must be regarded as minimal until their potential loss to wall rocks is evaluated.
Figure 10. Example of BSE images and EDS map of halo micas showing enrichment in the elements
discussed. (A) Micas in granitic wall rock enriched in Rb, Cs and probably Li (ACL 13-05). (B). Micas
enriched in Fe, Rb (and probably Li), tentatively classified as siderophyllite, in fractures in the
Figure 10. Example of BSE images and EDS map of halo micas showing enrichment in the ele-
ments discussed. (A) Micas in granitic wall rock enriched in Rb, Cs and probably Li (ACL 13-05).
(B) Micas enriched in Fe, Rb (and probably Li), tentatively classified as siderophyllite, in fractures in
the hanging wall mica schist approximately 3 m from the top of a spodumene pegmatite intersection
(ACL 13-02).

Minerals 2022, 12, 981 17 of 21
With the ongoing crystallization of a pegmatite body and formation of rare-element
minerals, it is expected that the residual fluid will be enriched in H2O and fluxes that control
the solubility of other incompatible elements, e.g., [19,20,49]. Considering the petrographic
characteristics explored earlier, it is suggested that after a crystalline framework was formed, the
H2O- and flux-rich residual fluids from pegmatite crystallization led to its alteration through
“auto-metasomatism”, in which K-feldspar and spodumene were consumed [18–20]. At some
stage, a hydrothermal fluid exsolved from the residual fluid, probably as H2O reached
a saturation of ~11.5 wt % in Al-saturated melts [50], after the resorption of aluminous
minerals into the fluid caused increased polymerization, and was mobilized into country
rocks causing exomorphic halos. Therefore, this fluid generated in the final stages of
pegmatite crystallization, in part, crystallized within the intrusion, forming the albitic late
primary assemblage, and in part, was mobilized into country rocks through fracturing
(Figure 10B), in agreement with a recent model of magmatic-hydrothermal transition at
the end of pegmatite crystallization [19,20]. Excess Li, B, Rb and other elements in the
halo-forming fluid are consistent with the absence of major phases bearing these elements
in albitite. This model is supported by the consistent internal evolution of pegmatites
and halo budgets among different areas and spodumene pegmatite bodies. More complex
interactions and halo patterns due to multiple pegmatite pulses cannot be ruled out, but
more detailed structural and geochronological characterization would be required to detect
and resolve them.
Since no obvious mineralogical changes in wall rocks have been observed more than
a few tens of centimeters from pegmatite contacts, micas in wall rocks are likely to be the
main distal halo mineral. Micas can generally accommodate all halo elements identified,
e.g., [51,52], and thus, compositions of micas crystallized in wall rocks during halo formation
are likely to differ significantly from the compositions of these minerals outside halos. This
has been reported in Leinster for a few of the elements [18]: Rb2O and Cs2O in micas
in a mica schist vary from below the detection limit in distal samples (>5 m away from
spodumene pegmatite contact) to up to 0.8 wt% Rb2O and 0.4 wt% Cs2O in exocontact
samples. A systematic analysis has not yet been done for granitic country rocks, but Rb2O
and Cs2O in exocontacts in granite are detectable at concentrations of around 0.4 wt.%
and 0.15 wt.%, respectively. Individual quantitative SEM-EDS point analyses (following
the method described in [19]) of dark mica in granodiorite within 1 m of the spodumene
pegmatite contact at Aclare yielded up to 0.9% wt.% Rb2O and 1.9% wt.% Cs2O.
In Leinster, the fluid’s geochemical composition (B, H2O) seems to have controlled
the partitioning of Li, Rb, Be, Sn and Ta, and have been an cause of the especially
strong partitioning of Cs, into the fluid and, consequently, to the halos, which supports
some previous findings [48]. The presence of meter-scale exomorphic halos of alkali el-
ements and fluxes is in accordance with halos described around spodumene pegmatites
elsewhere [8,9,53,54]. However, evidence for the mobilization of Ta has not been previously
described in pegmatite halos. It is also important to note that the percentage of elements in
halos (Table 2) in this pegmatitic system can reach over 5% for Ta and Be, over 10% for Li
and Rb and over 40% for Cs and Sn, which has major implications for the estimation of
pegmatite starting compositions for geochemical modeling, especially when the minerals
in which some of these elements are essential are absent from pegmatites, as is the case
in Leinster for B and Cs. Existing pegmatite concentrations of these elements must be
regarded as minimal until their potential loss to wall rocks is evaluated.
5.2. Economic Implications
Albite-spodumene pegmatites, such as those at Leinster, are economically interesting
due to their typically higher Li concentrations compared to other LCT pegmatite types [30].
Soil concentrations of Li, Rb, Ta and Cs have been used to target areas for exploration in
the poorly exposed Leinster belt [48]. The use of country rock chemical composition as an
exploration tool for spodumene pegmatites in Leinster is shown to be another viable tool,
in agreement with findings from similar studies in other evolved pegmatites, e.g., [45,55].

Minerals 2022, 12, 981 18 of 21
However, if the halo formation model proposed is realistic, the less altered pegmatite
bodies will have less pronounced halos of these elements and will be harder to target, yet
be potentially of a higher grade. Spodumene is the economic target mineral in Leinster and
because its breakdown is related to the presence of albitite, pegmatites with well-preserved
spodumene may have spatially smaller soil anomalies than pegmatites with an extensive
spodumene breakdown. The possible existence of spodumene pegmatites that have lost all
their spodumene by an alteration to albitite, or otherwise, must also be considered. Such
intrusions might be surrounded by intense Li halos, but be of no economic interest for Li.
Differences in the initial concentrations of H2O and other fluxing elements such as B, F and
P in the pegmatite-forming magma may influence the extent of the later replacement and
rare-element mineral breakdown at late-stages of pegmatite crystallization. Three other
factors likely to affect halo formation include depth of emplacement, expected to have
a strong control on fluid escape, the mineralogy and texture of host rocks, expected to
control the dimensions and density of fluid-filled fractures, and the orientation of pegmatite
intrusions, with halo-forming fluids more prone to escape upwards than downwards.
The proportions of rare elements released to the halo vary from element to element and
between different pegmatites. Whilst the controlling factors in these variations are not well
understood, in the studied examples, a much larger proportion of Cs (over 40%) appears to
be lost to the halo compared to other economically valuable elements (Li, Rb and Ta) where
typically less than 20% is lost (Table 2). Unusually low levels of a late-stage alterations
during the magmatic-hydrothermal transition at the end of pegmatite crystallization may,
therefore, likely be the most prospective for economic Cs’ concentrations in pegmatites,
unless the alteration is correlated with concentrations of these elements in pegmatite
magma. The possibility of economic Cs, and other element, concentrations in pegmatite
halos must also be considered if the elements occur here in an economically extractable
form. This, in turn, requires further detailed work on halo mineralogy, mineral chemistry
and texture with a geometallurgical focus.
6. Conclusions
Unzoned to weakly zoned spodumene pegmatites in the Leinster pegmatite belt host
high concentrations of Li (1.5–3% Li2O) and are a potential source of high-technology
metals such as Ta and Sn. Their predominant primary assemblage consists of spodumene
+ K-feldspar + albite + quartz + muscovite, and common accessory minerals include
garnet, apatite and beryl. Spodumene crystals are typically present from within a few
centimeters from the wall rocks to the centers of intrusions, suggesting early-stage Li-
saturation. Primary minerals are often replaced by late primary fine-grained albitite,
comprising albite (~90%) with accessory minerals including muscovite, garnet, apatite,
beryl, cassiterite and columbite-group minerals. This sodic alteration can be restricted,
occurring as isolated patches amongst primary minerals or accumulated in larger volumes
with oriented albite laths, suggesting a flow structure.
Exomorphic halos were formed in both mica schists and granitic rocks adjacent to
spodumene pegmatites, as evidenced by the mineralogy and geochemistry of wall rocks.
Although observable mineralogical halos only extend a few to tens of centimeters, min-
imum exomorphic halo widths of two to five meters into country rocks are identified,
presenting enrichment in Li, Rb, Be, B, Cs, Sn and Ta, a signature that, in part, compares
with and, in part, contrasts with that of fine-grained albitite in spodumene pegmatites. It is
suggested that after a process of auto-metasomatism, in which coarse, pegmatitic K-feldspar
and spodumene were partially resorbed into residual liquid, a fluid rich in H2O and B
exsolved, leading to the partitioning of the halo elements into this fluid. Hydrothermal
fluid was probably expelled into country rocks, where it formed rare-element halos, at
the time of albitite crystallization. The economically relevant enrichment of rare metals
in spodumene pegmatites and their halos presents challenges as well as opportunities to
mineral exploration strategies.

Minerals 2022, 12, 981 19 of 21
Supplementary Materials: The following supporting information can be downloaded at:
https://www.mdpi.com/article/10.3390/min12080981/s1, Supplementary Table S1: Results of
lithogeochemistry of drill cores, and Supplementary Table S2: Exomorphic halo calculations.
Author Contributions: Conceptualization, R.B. and J.F.M.; Data curation, Renata Barros; Formal
analysis, R.B.; Investigation, R.B., D.K. and T.F.; Methodology, R.B., J.F.M. and J.H.; Resources, J.H.;
Supervision, J.F.M. and J.H.; Visualization, R.B. and D.K.; Writing—original draft, R.B.; Writing—
review and editing, D.K., J.F.M., T.F. and J.H. All authors have read and agreed to the published
version of the manuscript.
Funding: This research was funded by CAPES (Coordenação de Aperfeiçoamento de Pessoal de
Nível Superior), grant number 99999.009548/2013-00. This publication has emanated from research
supported in part by a research grant from the Science Foundation Ireland (SFI) [grant number
13/RC/2092], co-funded under the European Regional Development Fund, and from a study funded
by the European Commission’s Horizon 2020 innovation program under grant agreement No 869274,
project GREENPEG New Exploration Tools for European Pegmatite Green-Tech Resources.
Data Availability Statement: The data presented in this study are available in this article and its
Supplementary Material.
Acknowledgments: The authors thank five anonymous reviewers who provided valuable feedback
to improve this manuscript. The authors also thank two anonymous reviewers for their comments
and suggestions on an earlier version of this manuscript. The authors thank Tom Culligan for making
the thin sections, the staff of Aurum, especially Mark Holdstock, Graham Parkin and Emma Sheard,
the staff of Blackstairs Lithium Ltd., especially Patrick McLaughlin and Gregory Sotiropoulos, and
Radek Škoda and Petr Gadas from Masaryk University Brno for some of the BSE images used in the
paper.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Glover, A.J.; Rogers, W.Z.; Barton, J.E. Granitic Pegmatites: Storehouses of Industrial Minerals. Elements 2012, 8, 269–273.
[CrossRef]
2. Linnen, R.L.; Van Lichtervelde, M.; Černý, P. Granitic Pegmatites as Sources of Strategic Metals. Elements 2012, 8, 275–280.
[CrossRef]
3. London, D. Rare-Element Granitic Pegmatites. In Rare Earth and Critical Elements in Ore Deposits. Society of Economic Geologists;
Verplanck, P.L., Hitzman, L.W., Eds.; Society of Economic Geologists, Inc.: Littleton, CO, USA, 2016; Volume 18, pp. 165–194.
4. United States Geological Survey. Mineral Commodity Summaries; United States Geological Survey: Reston, VA, USA, 2022; p. 202.
5. European Commission. Critical Raw Materials Resilience: Charting a Path towards Greater Security and Sustainability; European
Commission: Brussels, Belgium, 2020; p. 23.
6. Pirajno, F. Hydrothermal Processes and Mineral Systems; Springer: Berlin/Heidelberg, Germany, 2009; p. 1250.
7. Smith, R.E.; Perdrix, J.L.; Davis, J.M. Dispersion into pisolitic laterite from the Greenbushes mineralized Sn-Ta pegmatite system,
Western Australia. J. Geochem. Explor. 1987, 28, 251–265. [CrossRef]
8. Shearer, C.K.; Papike, J.J.; Simon, S.B.; Laul, J.C. Pegmatite-wallrock interactions, Black Hills, South Dakota: Interaction between
pegmatite-derived fluids and quartz-mica schist wallrock. Am. Mineral. 1986, 71, 518–539.
9. Trueman, D.L.; Černý, P. Exploration for rare-element granitic pegmatites. In Granitic Pegmatites in Science and Industry: Mineralog-
ical Association of Canada Short Course Handbook; Černý, P., Ed.; Mineralogical Association of Canada: Quebec, QC, Canada, 1982;
Volume 8, pp. 463–493.
10. Selway, J.B.; Breaks, F.W.; Tindle, A.G. A review of rare-element (Li-Cs-Ta) pegmatite exploration techniques for the Superior
Province, Canada, and large worldwide tantalum deposits. Explor. Min. Geol. 2005, 14, 1–30. [CrossRef]
11. Galeschuk, C.R.; Vanstone, P.J. Exploration for buried rare-element pegmatites in the Bernic Lake area of southeastern Manitoba.
In Rare-Element Geochemistry and Mineral Deposits, Geological Association of Canada, Short Course Notes; Linnen, R.L., Samson, I.M.,
Eds.; Geological Association of Canada: St. John’s, NL, Canada, 2005; Volume 17, pp. 153–167.
12. Galeschuk, C.R.; Vanstone, P.J. Exploration techniques for rare-element pegmatite in the Bird River greenstone belt, southeastern
Manitoba. In Proceedings of the Exploration 07: Fifth Decennial International Conference on Mineral Exploration, Toronto, ON,
Canada, 9–12 September 2007; Milkereit, B., Ed.; 2007; pp. 823–839.
13. Jolliff, B.; Papike, J.; Laul, J. Mineral recorders of pegmatite internal evolution: REE contents of tourmaline from the Bob Ingersoll
pegmatite, South Dakota. Geochim. Cosmochim. Acta 1987, 51, 2225–2232. [CrossRef]
14. Morgan VI, G.B.; London, D. Alteration of amphibolitic wallrocks around the Tanco rare element pegmatite, Bernic Lake,
Manitoba. Am. Mineral. 1987, 72, 1097–1121.

Minerals 2022, 12, 981 20 of 21
15. Fritschle, T.; Daly, J.S.; Whitehouse, M.J.; McConnell, B.; Buhre, S. Multiple intrusive phases in the Leinster Batholith, Ireland:
Geochronology, isotope geochemistry and constraints on the deformation history. J. Geol. Soc. Lond. 2018, 175, 229–246. [CrossRef]
16. Luecke, W. Lithium pegmatites in the Leinster Granite (southeast Ireland). Chem. Geol. 1981, 34, 195–233. [CrossRef]
17. Whitworth, M.P. Petrogenetic implications of garnets associated with lithium pegmatites from SE Ireland. Mineral. Mag. 1992, 56,
75–83. [CrossRef]
18. Barros, R.; Kaeter, D.; Menuge, J.F.; Škoda, R. Controls on chemical evolution and rare element enrichment in crystallising
albite-spodumene pegmatite and wallrocks: Constraints from mineral chemistry. Lithos 2019, 352–353, 105289. [CrossRef]
19. Kaeter, D.; Barros, R.; Menuge, J.F.; Chew, D.M. The magmatic–hydrothermal transition in rare-element pegmatites from southeast
Ireland: LA-ICP-MS chemical mapping of muscovite and columbite–tantalite. Geochim. Cosmochim. Acta 2018, 240, 98–130.
[CrossRef]
20. Kaeter, D.; Barros, R.; Menuge, J.F. Metasomatic High Field Strength Element, Tin, and Base Metal Enrichment Processes in
Lithium Pegmatites from Southeast Ireland. Econ. Geol. 2020, 116, 169–198. [CrossRef]
21. Holdsworth, R.E.; Woodcock, N.H.; Strachan, R.A. Geological framework of Britain and Ireland. In Geological History of Britain
and Ireland, 2nd ed.; Woodcock, N.H., Strachan, R.A., Eds.; Wiley Blackwell: Chichester, UK, 2009; p. 442.
22. Chew, D.M. Grampian Orogeny. In The Geology of Ireland, 2nd ed.; Holland, C.H., Sanders, I., Eds.; Dunedin Academic Press:
Edinburgh, UK, 2009.
23. McKerrow, W.S.; Mac Niocaill, C.; Ahlberg, P.E.; Clayton, G.; Cleal, C.J.; Eagar, M.C. The Late Palaeozoic relations between
Gondwana and Laurasia. Geol. Soc. Lond. Spec. Publ. 2000, 179, 9–20. [CrossRef]
24. Tietzsch-Tyler, D.; Sleeman, A.G. Geology of Carlow-Wexford: A Geological Description to Accompany the Bedrock Geology 1:100,000
Map Series, Sheet 19; Geological Survey Ireland: Dublin, Ireland, 1994; p. 57.
25. McConnell, B.; Philcox, M.E. Geology of Kildare-Wicklow: A Geological Description, with Accompanying Bedrock Geology 1:100,000 Scale
Map, Sheet 16; Geological Survey Ireland: Dublin, Ireland, 1994; p. 69.
26. Grogan, S.E.; Reavy, R.J. Disequilibrium textures in the Leinster Granite Complex, SE Ireland: Evidence for acid-acid magma
mixing. Mineral. Mag. 2002, 66, 929–939. [CrossRef]
27. Chew, D.M.; Stillman, C.J. Late Caledonian orogeny and magmatism. In The Geology of Ireland, 2nd ed.; Holland, C.H., Sanders, I.,
Eds.; Dunedin Academic Press: Edinburgh, UK, 2009; pp. 143–173.
28. McArdle, P.; Kennedy, M.J. The East Carlow Deformation Zone and its regional implications. Geol. Surv. Irel. Bull. 1985, 3,
237–255.
29. Sweetman, T.M. The geology of the Blackstairs Unit of the Leinster Granite. Ir. J. Earth Sci. 1988, 9, 39–59.
30. Černý, P.; Ercit, T.S. The classification of granitic pegmatites revisited. Can. Mineral. 2005, 46, 2005–2026. [CrossRef]
31. McConnell, B.J.; Morris, J.H.; Kennan, P.S. A comparison of the Ribband Group (southeastern Ireland) to the Manx Group (Isle of
Man) and Skiddaw Group (northwestern England). Geol. Soc. Lond. Spec. Publ. 1999, 160, 337–343. [CrossRef]
32. Graham, J.R.; Stillman, C.J. Ordovician of the south. In The Geology of Ireland, 2nd ed.; Holland, C.H., Sanders, I., Eds.; Dunedin
Academic Press: Edinburgh, UK, 2009; pp. 103–117.
33. Barros, R.; Menuge, J.F. The Origin of Spodumene Pegmatites Associated with the Leinster Granite In Southeast Ireland. Can.
Mineral. 2016, 54, 847–862. [CrossRef]
34. Rudnick, R.L.; Gao, S. Composition of the continental crust. In Treatise on Geochemistry; Rudnick, R.L., Ed.; Elsevier: Amsterdam,
The Netherlands, 2003; Volume 3, pp. 1–64.
35. Lima, A.M.C. Estrutura, Mineralogia e Génese dos Filões Aplitopegmatíticos com Espodumena da Região Barroso-Alvão. Ph.D.
Thesis, Universidade do Porto, Porto, Portugal, 2000; p. 270.
36. Groat, L.A.; Mulja, T.; Mauthner, M.H.F.; Ercit, T.S.; Raudsepp, M.; Gault, R.A.; Rollo, H.A. Geology and mineralogy of the Little
Nahanni rare-element granitic pegmatites, Northwest Territories. Can. Mineral. 2003, 41, 139–160. [CrossRef]
37. London, D.; Kontak, D.J. Granitic pegmatites: Scientific wonders and economic bonanzas. Elements 2012, 8, 257–261. [CrossRef]
38. Štemprok, M.; Novák, J.K.; David, J. The association between granites and tin-tungsten mineralization in the eastern Krušné hory
(Erzgebirge), Czech Republic. Monogr. Ser. Miner. Depos. 1994, 37, 97–129.
39. Li, H.; Palinkaš, L.A.; Evans, N.J.; Watanabe, K. Genesis of the Huangshaping W–Mo–Cu–Pb–Zn deposit, South China: Role
of magmatic water, metasomatized fluids, and basinal brines during intra-continental extension. Geol. J. 2019, 55, 1409–1430.
[CrossRef]
40. Llera, A.R.; Fuertes-Fuente, M.; Cepedal, A.; Martin-Izard, A. Barren and Li–Sn–Ta Mineralized Pegmatites from NW Spain
(Central Galicia): A Comparative Study of Their Mineralogy, Geochemistry, and Wallrock Metasomatism. Minerals 2019, 9, 739.
[CrossRef]
41. Burnham, C.W. Magmas and hydrothermal fluids. In Geochemistry of Hydrothermal ore Deposits, 3rd ed.; Barnes, H.L., Ed.; Wiley
and Sons: New York, NY, USA, 1997; pp. 63–123.
42. William-Jones, A.E.; Heinrich, C.A. Vapor transport of metals and the formation of magmatic-hydrothermal ore deposits. Econ.
Geol. 2005, 100, 1287–1312. [CrossRef]
43. Lecumberri-Sanchez, P.; Vieira, R.; Heinrich, C.A.; Pinto, F.; Wälle, M. Fluid-rock interaction is decisive for the formation of
tungsten deposits. Geology 2017, 45, 579–582. [CrossRef]
44. Sillitoe, R.H. Porphyry Copper Systems. Econ. Geol. 2010, 105, 3–41. [CrossRef]

Minerals 2022, 12, 981 21 of 21
45. Martins, T.; Linnen, R.L.; Fedikow, M.A.F.; Singh, J. Whole-rock and mineral geochemistry as exploration tools for rare-element
pegmatite in Manitoba: Examples from the Cat Lake-Winnipeg River and Wekusko Lake pegmatite fields (parts of NTS 52L6,
63J13). Manit. Geol. Survey Rep. Act. 2017, 5, 42–51.
46. Roda-Robles, E.; Pesquera, A.; Gil-Crespo, P.P.; Torres-Ruiz, J. Occurrence, paragenesis and compositional evolution of tourmaline
from the Tormes Dome area, Central Iberian Zone, Span. Can. Mineral. 2011, 49, 207–224. [CrossRef]
47. Kontak, D.J. Nature And Origin of an LCT-Suite Pegmatite with Late-Stage Sodium Enrichment, Brazil Lake, Yarmouth County,
Nova Scotia. I. Geological Setting and Petrology. Can. Mineral. 2006, 44, 563–598. [CrossRef]
48. Luecke, W. Soil geochemistry above a lithium pegmatite dyke at Aclare, southeast Ireland. Ir. J. Earth Sci. 1984, 6, 205–211.
49. London, D.; Morgan, G.B., VI. The pegmatite puzzle. Elements 2012, 8, 263–268. [CrossRef]
50. London, D.; Hervig, R.L.; Morgan, G.B., VI. Melt-vapor solubilities and elemental partitioning in peraluminous granite-pegmatite
systems: Experimental results with Macusani glass at 200 MPa. Contrib. Mineral. Petrol. 1988, 99, 360–373. [CrossRef]
51. Tischendorf, G.; Förster, H.J.; Gottesmann, B.; Rieder, M. True and brittle micas: Composition and solid-solution series. Mineral.
Mag. 2007, 71, 285–320. [CrossRef]
52. Rosing-Schow, N.; Müller, A.; Friis, H. A Comparison of the Mica Geochemistry of the Pegmatite Fields in Southern Norway. Can.
Mineral. 2018, 56, 463–488. [CrossRef]
53. Bettenay, L.F.; Partington, G.A.; Groves, D.I. Development of exploration concepts for Sn-Ta pegmatites: Use of host rock
associations and alteration haloes. West. Aust. Miner. Pet. Res. Inst. Rep. 1985, 13, 171.
54. Shearer, C.K.; Papike, J.J. Pegmatite-wallrock interaction: Holmquistite-bearing amphibolite, Edison pegmatites, Black Hills,
South Dakota. Am. Mineral. 1988, 73, 324–337.
55. Linnen, R.L.; Galeschuk, C.; Halden, N.M. The use of fracture minerals to define metasomatic aureoles around rare-metal
pegmatites. In Proceedings of the 27th International Applied Geochemistry Symposium, Tucson, Arizona, 20–24 April 2015; p. 5.

minerals-12-00981-v2.pdf

More Related Content

Similar to minerals-12-00981-v2.pdf (20)

Recently uploaded (20)

minerals-12-00981-v2.pdf