A Laurentian provenance for the Dalradian rocks of north Mayo, Ireland, and evidence for an original...

doi:10.1144/0016-76492009-147 2010; v. 167; p. 1033-1048 Journal of the Geological Society

Claire A. McAteer, J.Stephen Daly, Michael J. Flowerdew, Martin J. Whitehouse and Chris L. Kirkland

ComplexGneissevidence for an original basement�cover contact with the underlying Annagh

A Laurentian provenance for the Dalradian rocks of north Mayo, Ireland, and

Journal of the Geological Society

serviceEmail alerting to receive free email alerts when new articles cite this article click here

requestPermission to seek permission to re-use all or part of this article click here

Subscribe to subscribe to Journal of the Geological Society or the Lyell Collection click here

Notes

Downloaded by University College Dublin on 7 September 2010

© 2010 Geological Society of London

http://jgs.lyellcollection.org/cgi/alerts

http://www.geolsoc.org.uk/gsl/publications/page417.html

http://jgs.lyellcollection.org/subscriptions

Journal of the Geological Society, London, Vol. 167, 2010, pp. 1033–1048. doi: 10.1144/0016-76492009-147.

1033

A Laurentian provenance for the Dalradian rocks of north Mayo, Ireland, and

evidence for an original basement–cover contact with the underlying Annagh

Gneiss Complex

CLAIRE A. MCATEER1*, J. STEPHEN DALY 1, MICHAEL J. FLOWERDEW 2,

MARTIN J. WHITEHOUSE 3 & CHRIS L. KIRKLAND3

1UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland2British Antarctic Survey, High Cross, Madingley Road, Camfbridge CB3 0ET, UK

3Laboratory for Isotope Geology, Swedish Museum of Natural History, S-104 05, Stockholm, Sweden

*Corresponding author (e-mail: [email protected])

Abstract: Metasediments of the early Dalradian Grampian Group (Erris Group) and probable equivalents

(Inishkea Division) structurally overlie Palaeoproterozoic to Neoproterozoic Annagh Gneiss Complex

orthogneisses in NW Mayo, Ireland. Sm–Nd isotopic data suggest a Palaeoproterozoic source for the

metasediments. K-feldspar and granitoid clasts from the Doonamo Formation, Erris Group, record U–Pb

zircon ages of c. 1740 Ma and c. 980 Ma, respectively. These ages are within error of the c. 1730–1750 Ma

Mullet gneisses and c. 990 Ma Grenvillian migmatitic leucosomes in the underlying Annagh Gneiss Complex.

U–Pb detrital zircon data reveal that the Erris Group was deposited after c. 955 Ma, with predominant input

from c. 1640, c. 1500 and c. 990 Ma interpreted Laurentian sources (Labradorian, Pinwarian and Grenvillian

terranes, respectively). Limited detrital zircon data from the Inishkea Division yield similarly aged detritus

and a tentative maximum depositional age of c. 1005 Ma. Correlation of both sequences with the Scottish

Dalradian Grampian Group is considered valid based on detrital zircon U–Pb and whole-rock Sm–Nd data.

The clast ages support the hypothesis that the Dalradian unconformably overlies the Annagh Gneiss Complex

in north Mayo, whereas the detrital zircon data imply more distal Laurentian sources. Dalradian deposition is

thereby tied to the margins of Laurentia.

Supplementary material: U–Pb zircon (secondary ion mass spectrometry) data and descriptions of dated

zircon grains are available at http://www.geolsoc.org.uk/SUP18414.

Basement–cover relationships are crucial in reconstructing pa-

laeogeography as they link younger cover sequences to older

basement rocks at the time of deposition. However, these

relationships can be obscured by deformation, possibly leading to

misinterpretations, inappropriate tectonic models and erroneous

past continental configurations. In north Mayo, Ireland, the

Dalradian Supergroup, a major continental margin sequence,

thought to have been deposited on the Laurentian margin of the

Iapetus ocean (Cawood et al. 2003; Banks et al. 2007),

structurally overlies its postulated basement, the Palaeoprotero-

zoic to Neoproterozoic Annagh Gneiss Complex (Max & Long

1985; Kennedy & Menuge 1992; Fitzgerald et al. 1994;

Winchester & Max 1996; Daly 2001, 2009). Western Ireland is

one of the few places where the potential basement to the

Dalradian can be observed. The only other exposures are in the

Central Highlands, Scotland, where the Dalradian may rest

unconformably on the Glen Banchor and Dava Successions of

possible Moine affinity (Piasecki 1980; Robertson & Smith

1999; Strachan et al. 2002), and in the Inner Hebrides, Scotland,

where the Colonsay Group (possible lower Dalradian) rests

unconformably on the Palaeoproterozoic Rhinns Complex

(McAteer et al. 2010).

Early Dalradian deposition took place in the Neoproterozoic

(Dempster et al. 2002), a critical interval in Earth’s history that

saw the break-up of the supercontinent Rodinia, possible glacia-

tion of the entire planet and the emergence of the first hard-

bodied organisms (Grotzinger et al. 1995; Dalziel 1997; Hoffman

et al. 1998; Karlstrom et al. 2000). A better understanding of the

Neoproterozoic palaeogeography of Rodinia may help establish

how the past continental configurations evolved and how an

evolving palaeogeography influenced these phenomena. However,

in the case of north Mayo, Caledonian tectonics (Sanderson et al.

1980) has hampered efforts to decipher the relationship between

the Dalradian metasediments and the structurally underlying

Annagh Gneiss Complex. In the absence of clear field relation-

ships, other methods need to be employed.

In this paper U–Pb detrital zircon data are presented for the

lower Dalradian Grampian Group (Erris Group) and probable

equivalents (Inishkea Division), which structurally overlie the

Annagh Gneiss Complex in north Mayo. The data are compared

with possible source areas whose chronology is well established

(including the Annagh Gneiss Complex) and with U–Pb detrital

zircon data from the Grampian Group of Scotland (which has a

unique detrital zircon signature distinct from the rest of the

Dalradian; Cawood et al. 2003, 2007; Banks et al. 2007). Other

potential correlatives (i.e. the upper part of the Dalradian and

other major Neoproterozoic stratigraphic sequences such as the

Moine Supergroup and the Torridonian; Rainbird et al. 2001;

Cawood et al. 2003, 2004; Friend et al. 2003; Kinnaird et al.

2007; Kirkland et al. 2008) are also examined.

In addition to the detrital zircon study, whole-rock geochem-

istry and Sm–Nd isotopic analyses are presented for both the

Erris Group and the Inishkea Division as well as U–Pb zircon

ages for K-feldspar and granitoid clasts from pebbly horizons

within the Erris Group, which are petrographically similar to

lithologies within the Annagh Gneiss Complex.

The data are used to investigate the source(s) of the metasedi-

ments, possible correlatives and their relationship to the under-

lying Annagh Gneiss Complex. On a broader scale the data shed

some light on Neoproterozoic palaeogeography at the time these

rocks were deposited.

Geological setting

Metasediments of the Erris Group and Inishkea Division structu-

rally overlie the Palaeoproterozoic to Neoproterozoic Annagh

Gneiss Complex in north Mayo, Ireland (Fig. 1). Winchester &

Max’s (1996) unified stratigraphy for the Erris Group in Mayo is

adopted in this work (Table 1). Although there has been no

formal stratigraphic subdivision of the Inishkea Division, single

occurrences are ascribed informal stratigraphic names based on

location (e.g. Kinrovar Schist, Scotch Port Schist). The metasedi-

ments, the Annagh Gneiss Complex and basement–cover rela-

tionships are discussed sequentially below.

Metasediments (Erris Group and Inishkea Division)

The banded quartz–plagioclase–mica psammites and locally

pebbly horizons of the Erris Group (Winchester et al. 1988;

Winchester & Max 1996; Daly 2001, 2009; Fig. 1) pass

stratigraphically upwards into Dalradian (Appin Group) rocks

(Winchester et al. 1988; Winchester & Max 1996). Thus the

Erris Group is generally accepted to belong to the Dalradian

Grampian Group (Winchester & Max, 1996; Table 1).

Fig. 1. Schematic geological map of the study area adapted from Kennedy & Menuge (1992), Max et al. (1992), Winchester & Max (1996) and Daly &

Flowerdew (2005). Sample numbers and Sm–Nd model ages (Ma) are shown in white text with black boxes. White stars denote XRF and Sm–Nd

analyses only. Black stars denote XRF, Sm–Nd and U–Pb zircon analyses. Clasts C61B-1, C61B-10, C61D-30 and C61G-7 are from the same locality as

C61A. Inset map adapted from Chew et al. (2008). MT, Moine Thrust; GGF, Great Glen Fault; HBF, Highland Boundary Fault; FCBL, Fair Head–Clew

Bay Line; SUF, Southern Uplands Fault.

C . A. McATEER ET AL .1034

The relationship between the Inishkea Division and the

Dalradian Supergroup has proven more controversial. First recog-

nized by Trendall & Elwell (1963), the strongly foliated schists

and psammitic gneisses of the Inishkea Division were originally

believed to be part of an older, pre-Dalradian, Erris Complex

(Crow et al. 1971; Max & Sonet 1979; Winchester & Max

1984), which also included the Annagh Gneiss Complex. They

were later described as the products of Caledonian reworking of

rocks similar to the Annagh gneisses (Sutton & Max 1969; Crow

& Max 1976). Ambiguous structural evidence (Crow & Max

1976; Max & Long 1985; Winchester & Max 1987) and Rb–Sr

data (Max et al. 1983) then led to the suggestion that the

Inishkea Division metasediments were younger than the Annagh

gneisses but older than the Dalradian.

Kennedy & Menuge (1992, 1993) argued that there is no

evidence, structural or isotopic, to support a pre-Dalradian age

for the Inishkea Division (Yardley et al. (1987) also questioned

previous structural evidence). Furthermore, they recorded a

stratigraphic contact between the Inishkea Division and overlying

Erris Group north of Scotch Port and with rocks of possible

Appin Group affinity at Kildun (Fig. 1; Kennedy & Menuge

1992). This led them to infer that parts of the Inishkea Division

(namely the Kinrovar Schist) may belong to the Appin Group

(Kennedy & Menuge 1992). The rocks at Kildun, however, were

placed in the Erris Group by Winchester & Max (1996; and are

depicted as such in Fig. 1). Whereas Max & Winchester (1993)

maintained that all contacts between the Inishkea Division and

the Dalradian are tectonic, Daly (2001) also reported strati-

graphic contacts between them.

Interpretations of the depositional setting for both the Erris

Group and the Inishkea Division are complicated by Caledonian

metamorphism and deformation, which also inhibit rigorous

basin analysis (Daly 2001). The Erris Group is thought to have a

fluviatile to marginal marine setting (Winchester et al. 1988;

Daly 2001), whereas the Inishkea Division may represent a suite

of greywackes deposited in a restricted basin (Winchester & Max

1987). Cross-bedding, channelling and compaction structures

have been recorded in the Erris Group (Winchester et al. 1988;

this study). Graded bedding, slump conglomerates and bottom

compaction structures have been reported in the Inishkea Divi-

sion (Max & Winchester 1993).

The Inishkea Division and the Erris Group are geochemically

similar to the Grampian Group in Scotland (Max & Winchester

1993; Winchester & Max 1996) and both sequences have similar

whole-rock Sm–Nd depleted mantle model ages (tDM; Inishkea

Division 1609–1986 Ma; Erris Group 1619–1754 Ma; Kennedy

& Menuge 1992; J. S. Daly & J. F. Menuge, unpubl. data) to the

Scottish Grampian Group (Banks et al. 2007; J. S. Daly & J. F.

Menuge, unpubl. data). When combined with the stratigraphic

relationships outlined above, these geochemical and isotopic

similarities suggest that the Inishkea Division and the Erris

Group are probable correlatives and that both probably correlate

with the Scottish Grampian Group. Based on geochemical

characteristics, an Appin Group affinity for the Kinrovar Schist

(Inishkea Division; Kennedy & Menuge 1992, 1993), is, how-

ever, unlikely (Max & Winchester 1993).

Annagh Gneiss Complex

The predominantly Palaeoproterozoic, granodioritic to granitic

orthogneisses (Winchester & Max 1984; Daly 2001) of the

Annagh Gneiss Complex (Kennedy & Menuge 1992; Menuge &

Daly 1994) structurally underlie the Erris Group and the Inishkea

Division in north Mayo (Fig. 1). Formerly part of the Erris

Complex (Crow et al. 1971), and originally considered to be of

Archaean age (Hull 1882), the Annagh gneisses were later

reinterpreted as Caledonian migmatites developed from the

surrounding metasedimentary rocks (Kilroe 1907; Trendall &

Elwell 1963; Phillips et al. 1969). This interpretation prevailed

until Sutton & Max (1969) recognized that the Annagh gneisses

were intensely deformed prior to the Caledonian orogeny and

Brindley (1969) suggested that Hull’s (1882) interpretation be re-

examined. It has since been demonstrated that the Annagh

Gneiss Complex, the protoliths of which were shown to be of

plutonic origin (based on geochemistry and field evidence;

Winchester & Max 1984), was deformed during the Grenville

orogeny (van Breemen et al. 1976, 1978; Max & Sonet 1979;

Aftalion & Max 1987). Menuge & Daly (1990) suggested that

the Annagh gneisses represented crust that formed in two distinct

episodes, one at c. 1.9 Ga and the other at c. 1.35 Ga.

The chronology of the Annagh Gneiss Complex is now well

established (Table 2; Daly 1996, 2001, 2009; Daly & Flowerdew

2005) and it can be divided into the c. 1.75 Ga Mullet gneiss, c.

1.28 Ga Cross Point gneiss and c. 1.18 Ga Doolough gneiss (Fig.

1; Daly 1996). The Mullet gneisses are characterized by

migmatized quartzofeldspathic orthogneisses and locally darker

micaceous bands. Compositionally they are I-type metaluminous

monzodiorites, granodiorites (which predominate) and granites

with a magmatic arc chemistry (Daly 1996). The syenitic to

granitic Cross Point gneiss displays A-type, within-plate geo-

chemistry (Fitzgerald et al. 1996). Pre-Grenville amphibolite

bodies occur in both the Mullet and Cross Point gneisses (Daly

1996). The Doolough gneisses consist of subalkaline granites

and trondhjemites with some amphibolite. These juvenile

gneisses, which are very highly strained, are cut by the c.

1015 Ma Doolough Granite (Daly 1996). Several generations of

Grenville-aged granite–pegmatite sheets cut the Annagh Gneiss

Complex (Daly 1996; Table 2).

Grenville deformation of the Annagh Gneiss Complex oc-

curred in three phases (Daly 1996). The first two phases occurred

between c. 1177 and c. 1015 Ma (Daly 1996). The third event

took place between c. 995 and c. 960 Ma (Daly 1996). There is

no evidence to suggest that the Annagh Gneiss Complex was

affected by a post-Grenville, pre-Grampian orogeny (Daly &

Table 1. Simplified stratigraphy of the north Mayo Dalradian adapted from Winchester & Max (1996) with likely position of the Inishkea Division

North Mayo Dalradian Scottish Dalradian Dalradian Supergroup

Benmore FormationBroad Haven Formation

9>>=>>;

9=; Glen Spean Subgroup

9>>>>=>>>>;

Belderg FormationErris Group

Grampian GroupDoonamo Formation

�Corrieyairack Subgroup

Inishkea Division

PROVENANCE OF THE NORTH MAYO DALRADIAN 1035

Flowerdew 2005). The pre-Caledonian history of the Annagh

Gneiss Complex is summarized in Table 2.

Detailed descriptions of the Annagh Gneiss Complex ortho-

gneisses have been given by Winchester & Max (1984, 1988)

and Daly (1996, 2001, 2009). Details of field relationships have

been given by Sutton (1969, 1972), Sutton & Max (1969), Max

(1970) and Menuge & Daly (1990).

Basement–cover relationships

All contacts between the Erris Group, the Inishkea Division, and

other parts of the Dalradian with the Annagh Gneiss Complex

are tectonic. However, the metasediments consistently face away

from the orthogneisses (Max & Long 1985; Winchester et al.

1988; Winchester & Max 1996), and post-Grenville metadoler-

ites cutting the Annagh Gneiss Complex are similar to pre-

deformational dykes in both the Erris Group and the Inishkea

Division (Sutton 1972; Winchester & Max 1988; Menuge &

Daly 1990; Kennedy & Menuge 1992; Fitzgerald et al. 1994;

Daly 1996). This suggests that the metasediments were stitched

together with the older ‘basement’ prior to deformation. Sm–Nd

isotopic data demonstrate that both the Inishkea Division and the

Erris Group were derived from a Palaeoproterozoic source

similar to the Annagh Gneiss Complex (Kennedy & Menuge

1992; J. S. Daly & J. F. Menuge, unpubl. data). Moreover, K-

feldspar and granitic clasts, from pebbly horizons within the

Erris Group, petrographically resemble lithologies within the

Annagh Gneiss Complex (Fig. 2). All of these observations

suggest that the Annagh Gneiss Complex represents the deposi-

tional basement to the Dalradian of NW Ireland.

Sample descriptions and localities

One psammite and four clasts (three K-feldspar clasts and one

granitoid clast) were sampled from the stratigraphically lowest

subdivision of the Erris Group, the Doonamo Formation. In

addition, four mica schists from the Inishkea Division were also

sampled (Fig. 1).

Samples of the Doonamo Formation were collected along a

shoreline exposure at Spinkadoon (Fig. 1). At this locality beds

up to 1 m thick of tabular, laterally continuous psammites are

interbedded with thin bands of mica schist (up to c. 20 cm thick)

and occasional pebble beds (eight pebble horizons were identi-

fied). Bedding strikes roughly east–west, dips c. 508 to the south

and youngs to the south away from the structurally underlying

Annagh Gneiss Complex. The rocks are foliated, more intensely

so in the finer-grained mica-schist horizons. The foliation dips

shallowly to the north, cutting bedding at an angle of c. 408.

Channelling, cross-bedding, trough cross-bedding and hummocky

cross-stratification were observed in the psammites (Fig. 2b).

The pebble beds are matrix-supported, display erosive bases

and appear to pinch out laterally. The pebbles occur predomi-

nantly towards the tops of the beds and are elongated as a result

of strain during the Caledonian orogeny (Sanderson et al. 1980).

In the thicker pebble horizons (Fig. 2a), the pebbles are

distributed throughout the bed. Granitoid and quartzo-feldspathic

gneissic pebbles are common as well as centimetre-sized quartz

and K-feldspar clasts. The pelitic matrix of these beds consists of

quartz (33%), biotite (28%), epidote (14%), muscovite (9%),

opaque minerals (9%) and minor amounts of apatite, plagioclase,

orthoclase, microcline and titanite.

The sedimentary structures in the psammites suggest a shallow

marine depositional setting, with the hummocky cross-stratifica-

tion indicative of deposition between fair-weather wave base and

storm wave base. The pebble beds may represent transgressive

lag deposits, which would have formed as the shoreline retreated

causing a winnowing of coarser material and reworking of some

of the material below. This seems to be the case for the pebble

horizon displayed in Figure 2a, where a small lens of coarser

material in the underlying psammite might suggest a reworking

event. However, the frequency of these pebble horizons (eight

occurrences over c. 35 m) suggests that they are unlikely to be

entirely controlled by transgressive events. An alternative expla-

nation is that the pebble horizons may represent interfingering

between a deltaic front and shoreline deposits, where debris

flow-like deltaic deposits are interspersed with shallow marine

deposits. This would account for the frequency of pebble

horizons. A combination of these scenarios is also possible.

One psammite (C61A) and four pebbles (K-feldspar clasts

C61B-1, C61B-10 and C61D-30, and C61G-7, a granitoid clast)

were collected at Spinkadoon. C61B-1 and C61B-10 were

sampled from a pebble horizon [F681391] c. 4 m above C61A.

C61D-30 was sampled 4 m above this and C61G-7 was collected

from a stratigraphically lower pebble horizon almost 40 m below

C61A [F682392]. C61A is a quartz-rich (55%) psammite

(average grain size c. 200 �m) with muscovite (15%), biotite

(5%), epidote (10%), K-feldspar (5%; mostly orthoclase with

minor microcline) and minor amounts of plagioclase, opaque

minerals, titanite, zircon and apatite. The micas define a weak

foliation. Clasts C61B-1, C61B-10 and C61G-7 are coarse-

grained K-feldspar crystals and probably represent fragments of

granitic pegmatite. They are petrographically similar to Grenville

pegmatites in the Annagh Gneiss Complex and older K-feldspar

megacrystic sections of the Mullet gneisses (Fig. 2c). C61B-1

consists of a large, centimetre-sized perthite crystal (with some

clay and chlorite alteration) with inclusions of fine-grained white

Table 2. Pre-Grampian history of the Annagh Gneiss Complex

Age (Ma) Event

1753 � 3 Formation of Mullet gneiss protolith (crustal addition of juvenile magma); c. 1730–1750 Ma zircon alsoreported*

1271 � 6, 1287 +38/�35 Formation of Cross Point gneiss protolith at Tristia and Cross Point (anorogenic magmatism)1177 � 4 Formation of Doolough gneiss protolith (crustal addition of juvenile magma)

DG1 and DG2 Grenville deformation events1015 � 4 Intrusion of peralkaline Doolough Granite at Dooloughc. 999–980 Migmatization and pegmatite injection958 +17/�19 Metamorphic zircon defining DG3 Grenville foliation943 � 8† Post-tectonic titanite growth

Data from Daly (1996); additional data sources: * J. S. Daly (unpubl. data); † Daly & Flowerdew (2005).


mica, quartz, K-feldspar, epidote, zircon, opaque minerals and

small veinlets of finer-grained quartz, K-feldspar, epidote and

opaque minerals. C61B-10 consists of a microcline crystal (with

clay and chlorite alteration), c. 1.5 cm in size with inclusions of

white mica, opaque minerals, quartz, orthoclase, zircon and

epidote. C61G-7 is made up of a large, fractured orthoclase

crystal (with clay and chlorite alteration) about 1.2 cm in size

with inclusions of quartz, orthoclase, plagioclase, epidote, white

mica, zircon and opaque minerals and cross-cutting veinlets of

quartz, orthoclase, and plagioclase. C61D-30 is petrographically

similar to c. 990 Ma migmatitic leucosomes from Annagh Head

(Daly 1996) and consists of large microcline crystals up to

0.5 cm in size with finer-grained recrystallized quartz and K-

feldspar, some opaque minerals and fine-grained white mica and

minor amounts of zircon and biotite, partly replaced by chlorite.

Schists from the Inishkea Division (C62, C63, C66B, C67)

were collected at Carricklahan, Kinrovar, Tiraun Point and

Scotch Port (Fig. 1). Unlike the Doonamo Formation at Spinka-

doon, these rocks are strongly deformed and as a result

sedimentary structures, including bedding, are difficult to distin-

guish. Sample C62, of Carricklahan Schist (Max et al. 1992; Fig.

1), consists of quartz, biotite, muscovite, feldspar porphyroblasts

(plagioclase and K-feldspar with inclusions of quartz and white

mica), epidote and minor amounts of apatite, opaque minerals,

titanite and zircon. A strong foliation, defined by quartz, biotite,

muscovite and epidote, wraps around the feldspar porphyroblasts,

suggesting that they formed before the foliation. Compositional

layering, possibly defining original bedding, strikes roughly

NW–SE and dips about 608 northeastwards.

Sample C63, from the Kinrovar Schist (Fig. 1) is a coarse-

grained porphyroblastic schist comprising quartz, biotite, musco-

vite, garnet, feldspar porphyroblasts (plagioclase and K-feldspar

with inclusions of quartz, white mica, opaque minerals and

garnet), zircon and apatite. Biotite (with inclusions of zircon and

some chlorite replacement) and muscovite define a foliation that

wraps around the feldspar porphyroblasts. Garnet occurs as

inclusions within the feldspar porphyroblasts but can also be

found occasionally defining the foliation, possibly suggesting two

generations of garnet growth. Kennedy & Menuge (1992)

described the rocks from this locality, which are layered on a

scale of 5–30 cm, as pelitic porphyroblastic oligoclase or albite

garnet schists with muscovite and biotite. Sample C66B was

collected from the coast at Tiraun Point (Fig. 1) and is

petrographically similar to C63. A sample of the Scotch Port

Schist, C67 (Fig. 1), contains quartz, biotite, muscovite, garnet

porphyroblasts and some apatite, zircon and titanite. A strong

foliation, defined by biotite and muscovite, wraps around the

garnet porphyroblasts (which have fine-grained inclusions of

white mica and quartz), implying that the foliation post-dates

porphyroblast growth.

Sample preparation and analytical methods

Whole-rock major and trace element analyses and Sm–Nd

isotopic analyses were carried out on all samples, excluding

clasts, for which there was insufficient material. The Doonamo

Formation clasts (C61B-1, C61B-10, C61D-30, C61G-7) were

dated by the U–Pb zircon method and a U–Pb detrital zircon

study was carried out on samples C61A (Doonamo Formation

psammite, Erris Group), C63 (Kinrovar Schist, Inishkea Divi-

sion) and C67 (Scotch Port Schist, Inishkea Division).

Weathered material and veins were removed from samples

prior to crushing in a Retsch tungsten carbide jaw-crusher.

Whole-rock aliquots (c. 100 g) were milled in a tungsten carbide

Fig. 2. Doonamo Formation (Erris Group), Spinkadoon and Mullet

gneiss, Annagh Head. (a) A c. 20 cm thick pebble bed from the

Doonamo Formation (C61B-1 and C61B-10 sampled from this horizon)

overlying a cross-bedded psammite with lenses of coarser-grained

material at Spinkadoon. Photograph looking east; beds young to the

south. (b) Cross-bedding and hummocky cross-stratification, Spinkadoon.

(c) K-feldspar megacrystic orthogneiss (Mullet gneiss) and later

Grenville pegmatite, Annagh Head.


Tema mill. Major and trace element analyses (Table 3) were

carried out by X-ray fluorescence (XRF) spectrometry at the

Department of Geology, University of Leicester on fusion beads

and pressed powder pellets respectively.

Chemical separation of Sm and Nd for isotopic analysis

followed Pin et al. (1994) using TruSPEC and LN resins. Sm–

Nd isotope analyses (Table 4) were carried out on spiked samples

using a multi-collector VG 354 mass spectrometer at the School

of Geological Sciences, University College Dublin. Concentra-

tions were calculated offline from the measured ratios, following

correction for mass fractionation and spike addition. 143Nd/144Nd

ratios are relative to a 143Nd/144Nd ratio of 0.511850 for the La

Jolla standard (see Table 4).

Zircon grains were separated from �250 �m fractions using

di-iodomethane. Detrital mineral grains were randomly selected,

whereas those from clasts were selected by grain size, turbidity

and state of alteration in view of their expected igneous protolith.

Zircon grains were cast in an epoxy mount, polished and imaged

in both reflected and transmitted light. The gold-coated mount

was imaged by scanning electron microscopy (SEM) using

secondary electron (SE) and cathodoluminescence (CL) detectors

to determine the internal structure of the grains so as to guide in

situ analysis.

Zircon grains were analysed by secondary ion mass spectro-

metry (SIMS) on the NORDSIM Cameca IMS 1270 ion micro-

probe at the Swedish Museum of Natural History, Stockholm,

Sweden. U–Th–Pb zircon analyses followed the methods de-

scribed by Whitehouse & Kamber (2005). Pb/U calibration was

carried out using the 1065.4 � 0.3 Ma Geostandards zircon

91500, with U and Pb concentrations of 80 ppm and 15 ppm

respectively (Wiedenbeck et al. 1995). Common Pb corrections

were applied to a minority of data with 206Pb/204Pb ratios ,3000

(indicating significant common Pb), using the present-day terres-

trial common Pb estimate of Stacey & Kramers (1975). This

Table 3. Whole-rock major and trace element data for the Erris Group and the Inishkea Division

Erris Group Inishkea Division

Doonamo Formation Carricklahan Schist Kinrovar Schist Tiraun Point Scotch Port SchistC61A C62 C63 C66B C67

Oxides (wt %)SiO2 73.49 65.16 62.08 60.40 59.85TiO2 0.47 1.06 0.89 0.84 0.80Al2O3 11.84 13.77 16.60 17.25 17.77Fe2O3 3.53 6.45 6.62 6.74 6.63MnO 0.05 0.10 0.10 0.11 0.11MgO 0.78 1.63 2.10 2.43 2.80CaO 1.95 3.25 2.08 2.02 1.54Na2O 2.79 3.07 3.88 2.45 2.41K2O 3.11 3.19 2.93 4.10 4.70P2O5 0.06 0.20 0.26 0.27 0.23LOI 0.67 0.86 1.20 1.62 1.76Total 98.74 98.74 98.79 98.25 98.61Trace elements (ppm)Ba 934 893 767 1008 1192Cr 37 42 51 55 53Cu b.d. 9 24 34 18Ga 12 16 19 21 24Mo 1 1 1 2 1Nb 11 21 17 16 14Ni 8 14 23 31 29Pb 16 19 19 20 57Sc 8 13 16 16 17Th 4 14 13 15 16U 2 4 4 3 4V 42 90 93 97 99Y 20 43 37 23 34Zn 30 68 85 100 153Zr 167 563 301 205 164La 21 51 51 30 47Ce 46 114 105 64 90Sm 4 10 8 5 7Nd 23 54 43 27 40Cs b.d. 2 5 3 6Rb 92 117 115 157 189Sr 326 314 292 218 208SiO2/Al2O3 6.21 4.73 3.74 3.50 3.37Fe2O3/K2O 1.14 2.02 2.26 1.64 1.41Cr/Zr 0.22 0.07 0.17 0.27 0.32Rb/Sr 0.28 0.37 0.39 0.72 0.91Y/Sr 0.06 0.14 0.13 0.11 0.17Zr/Sc 19.71 43.81 18.78 12.76 9.82

LOI, loss on ignition. b.d., concentration below the lower limit of detection. Sm and Nd concentrations determined by TIMS.

C. A. McATEER ET AL .1038

assumes that any common Pb detected was due to surface

contamination during sample preparation.

All ages were calculated and plots generated using Isoplot

3.00 (Ludwig 2003). All ages are concordia ages (Ludwig 1998)

unless otherwise stated. All errors in ages presented and

discussed in the text are quoted at the 2� level; concordia age

errors are 2� except for those .100 Ma, which represent 95%

confidence levels. For U–Pb zircon geochronology of clasts only

data whose error ellipse intersects concordia are used to calculate

a concordia age. The same criterion was adopted to screen

analyses of detrital grains prior to plotting on age distribution

diagrams. Discordant data are discussed below. Where core and

rim ages are available for the same detrital grain only the rim

age is included in the age distribution plot. The significance of

corresponding cores is discussed below.

Results

Whole-rock geochemistry

Major and trace element analyses are listed in Table 3. Samples

C63, C66B and C67 (Inishkea Division from Kinrovar, Tiraun

Point and Scotch Port, respectively) plot as shales on a

log(Fe2O3/K2O) v. log(SiO2/Al2O3) plot (Herron 1988; Fig. 3).

Using the same parameters, C62 (Carricklahan Schist, Inishkea

Division) plots as a greywacke and C61A (Doonamo Formation,

Erris Group) plots as a borderline arkose–litharenite–greywacke.

Cr/Zr ratios (Table 3) are low, consistent with predominant input

from an acidic source region (Winchester & Max 1996). In

addition, low Rb/Sr and Y/Sr ratios (Table 3) suggest that these

sediments are immature (Winchester & Max 1996). Excluding

sample C62, Zr/Sc ratios are less than 30, consistent with

minimal sedimentary recycling (McLennan et al. 2003). Whereas

trace element signatures are similar for all samples (Fig. 4a), the

psammitic sample C61A is less enriched in REE than the more

pelitic samples. The trace element signatures of the analysed

samples are similar to average values for the Scottish Grampian

Group (Winchester & Glover 1988; Fig. 4b).

Sm–Nd data

Results are listed in Table 4. The single Erris Group sample from

the Doonamo Formation (sample C61A) yields a whole-rock

Sm–Nd model age (tDM) of 1723 Ma, Inishkea Division rocks

(samples C62, C63, C66B, C67) yield tDM ranging from 1728 to

1829 Ma (Fig. 1) and �Nd values for all samples lie within the

Sm–Nd evolutionary field of the Annagh Gneiss Complex (Fig.

5; Menuge & Daly 1990).

U–Pb zircon geochronology

C61B-1, K-feldspar clast, Doonamo Formation, Erris Group,

Spinkadoon. Zircon grains from C61B-1 (Fig. 6) comprise sub-

rounded, oscillatory-zoned prisms of 48–110 �m width and 82–

232 �m length, with a mean Th/U value of c. 0.3 consistent with

an igneous origin (Belousova et al. 2002). Eight out of 18

analyses (from five out of 12 zircon grains) define a concordia

age of 1743 � 4 Ma (Fig. 7a). This age is interpreted as the

magmatic age of the clast. Analyses of zircon rims are discordant

and, in common with the other discordant analyses, have been

variably influenced by recent Pb loss, all but four of which define

a weighted mean 207Pb/206Pb age (1744 � 6 Ma) within error of

the concordia age. These four analyses (spots 11, 2a, 3 and 7a),Table4.Whole-rock

Sm–Nddata

fortheErrisGroupandtheInishkeaDivision

Sam

ple

Fo

rmat

ion

Rock

typ

eG

rid

refe

ren

ceL

atit

ud

eL

on

git

ud

eS

m(p

pm

)N

d(p

pm

)1

47S

m/1

44N

d1

43N

d/1

44N

d� N

d

(90

0M

a)t D

M

(Ma)

ErrisGroup

C6

1A

Do

on

amo

Fo

rmat

ion

Psa

mm

ite

F6

82

39

15

4.2

84

11

�1

0.0

24

49

42

30

.10

97

0.5

11

86

2�

5.2

17

23

InishkeaDivision

C6

2C

arri

ckla

han

Sch

ist

Sch

ist

F6

10

21

25

4.1

21

53

�1

0.1

25

54

10

54

0.1

08

20

.511

84

0�

5.4

17

28

C6

3K

inro

var

Sch

ist

Sch

ist

F7

09

14

45

4.0

62

69

�9

.971

09

84

30

.11

17

0.5

11

81

3�

6.3

18

29

C6

6B

Inis

hk

eaD

ivis

ion

,T

irau

nP

oin

tS

chis

tF

616

23

45

4.1

41

83

�1

0.1

17

94

52

70

.11

44

0.5

11

86

3�

5.7

18

03

C6

7S

cotc

hP

ort

Sch

ist

Sch

ist

F6

45

36

05

4.2

55

34

�1

0.0

79

49

74

00

.11

11

0.5

11

86

2�

5.3

17

47

143N

d/1

44N

dra

tios

andt D

Mar

ere

lati

ve

toa

143N

d/1

44N

dra

tio

of

0.5

1185

for

the

La

Joll

ast

andar

d.

Mea

nval

ue

for

mea

sure

dL

aJo

lla

143N

d/1

44N

dra

tio¼

0.5

11

84

69�

0.0

00009

(2�

;n¼

9).

143N

d/1

44N

dra

tios

are

norm

aliz

edto

146N

d/

144N

d¼

0.7

219.

Dep

lete

dm

antl

eN

dm

odel

age

rela

tive

toth

em

antl

eev

olu

tion

model

of

DeP

aolo

(1981)

usi

ng

pre

sent-

day

CH

UR

rati

os

of

143N

d/1

44N

d¼

0.5

12638

and

147S

m/1

44N

d¼

0.1

966.

Bla

nk

Nd¼

0.4

1ng.


when anchored to 1743 Ma, define a discordia with a lower

intercept of 690 � 4 Ma (Fig. 7a).

C61B-10, K-feldspar clast, Doonamo Formation, Erris Group,

Spinkadoon. Zircon grains from C61B-10 comprise mainly pink

prismatic, oscillatory-zoned grains (Fig. 6) of 50–65 �m width

and 87–105 �m length. Six out of 10 analyses (from three out of

six zircon grains dated) yield a concordia age of 1744 � 6 Ma

(Fig. 7b). All analyses have Th/U ratios (c. 0.3) consistent with a

magmatic origin and, as such, the concordia age is interpreted as

dating the clast. Discordance of the remaining data (spots 2, 4b,

5 and 5b) may be explained by Pb loss (Fig. 7b).

C61G-7, K-feldspar clast, Doonamo Formation, Erris Group,

Spinkadoon. Only two analyses were obtained from a single

oscillatory-zoned prismatic zircon grain from sample C61G-7

(Fig. 6). One of these intersects concordia whereas the other is

reversely discordant. The data define a weighted mean 207Pb/206Pb age of 1750 � 12 Ma, which is interpreted as the magmatic

age of the clast, given its petrography and Th/U ratio (c. 0.27).

C61D-30, granitoid clast, Doonamo Formation, Erris Group,

Spinkadoon. Zircon grains from C61D-30 comprise mainly pink

and brown broken, rounded and sub-rounded prisms, most of

which display oscillatory zoning (Fig. 6). Five out of six grains

have low Th/U ratios (,0.02) and generally high U contents.

Five out of 13 analyses (spots 3, 3b, 6, 4 and 4b) plot near one

another on concordia but overlap insufficiently to define a

concordia age (Fig. 7c). Three of these (spots 3, 3b and 6) yield

a concordia age of 982 � 13 Ma. Alternatively a concordia age

of 973 � 13 Ma can be calculated from spots 3, 3b and 4. Spots

2a, 2c and 7 are reversely discordant, probably as a result of their

high U concentrations (3464 ppm, 3620 ppm and 3165 ppm,

respectively), which invalidates the standard calibration (91500

has only 81 ppm U; Fig. 7c). However, this does not affect the207Pb/206Pb ratios, and all eight analyses define a weighted mean207Pb/206Pb age of 972 � 8 Ma (MSWD ¼ 3.6, Fig. 7c). This age

is interpreted as dating the formation of the zircon in this clast,

possibly in a metamorphic event in view of the low Th/U ratios.

Given the high U concentrations of these grains, however, the

Th/U ratios could be misleading as an indicator of zircon growth

conditions. Of the remaining discordant data, spots 2b, 3c and 4c

are consistent with recent Pb loss (Fig. 7c) and yield a weighted207Pb/206Pb age within error of the age of the clast

(953 � 13 Ma). Spot 5 yields a 207Pb/206Pb age of 1022 � 49 Ma

and may indicate the presence of an inherited component (Fig.

7c). When plotted with the concordant analyses, spot 1 lies along

a discordia with lower and upper intercepts of 477 � 79 Ma and

964 � 12 Ma, respectively, consistent with Grampian Pb loss

(Fig. 7c).

C61A, detrital zircon, Doonamo Formation, Erris Group, Spinka-

doon. Zircon grains from C61A are 63–185 �m wide and 110–

285 �m long, colourless, pink and brown in colour, and rounded

to sub-rounded in shape. Most exhibit oscillatory zoning but

some sector-zoned grains are also present (Fig. 6). Zircon age is

independent of zircon colour and morphology. Of the grains

analysed 84 out of 99 yield a range of concordant ages between

c. 950 Ma and c. 1740 Ma, with peaks at c. 990 Ma, 1500 Ma

and 1640 Ma (Fig. 8). The youngest concordant detrital zircon

(grain 103, a CL-dark, unzoned grain) yields a concordia age of

955 � 12 Ma (Fig. 9). Another, possibly younger grain (grain

57), whose error ellipse barely touches concordia (Fig. 9), has a206Pb/238U age of 919 � 21 Ma (and a concordia age of

928 � 310 Ma). This grain is interpreted to have experienced Pb

loss, however, and is not deemed a reliable constraint on the

maximum depositional age of the Doonamo Formation. Its 207Pb/206Pb age of 986 � 51 is within error of that of the more robust

analysis of grain 103 (i.e. c. 955 Ma). We therefore interpret that

deposition of the Doonamo Formation took place after c.

955 Ma.

Dating cores and rims can potentially yield additional insight

into provenance by identifying inherited zircon components; how-

ever, this is rarely possible because of grain size limitations and

the diverse opportunities for discordance. Corresponding cores

and rims were dated in three grains; however, only one, grain 1,

yielded concordant data for both parts. Grain 1 has an oscillatory-

zoned core dated at 1377 � 19 Ma (spot 1b), and a CL-bright,

zoned rim (spot 1a) with an age of 998 � 15 Ma (Fig. 6).

Sixteen analyses were excluded from the age distribution plot

(Fig. 8) on the basis of discordance. All are within the same age-

range as the concordant data except for grain 3 (207Pb/206Pb age

of 1848 � 12 Ma), grain 57 (206Pb/238U age of 919 � 21 Ma)

and grain 87 (206Pb/238U age of 891 � 16 Ma) (Fig. 9). Grains

Fig. 3. Classification of Erris Group

(C61A) and Inishkea Division (C62, C63,

C66B, C67) samples after Herron (1988)

using log (Fe2O3/K2O) v. log (SiO2/Al2O3).


57 and 87 are interpreted as having suffered Pb loss and are

probably the same age, within error, as the youngest cluster of

concordant data at c. 1 Ga. (Fig. 9). Grain 3 has also experienced

Pb loss but possibly indicates the presence of an older, c.

1850 Ma component (Fig. 9).

C63, detrital zircon, Kinrovar Schist, Inishkea Division, Kinro-

var. Detrital zircon grains from sample C63 are 60–178 �m wide

and 78–265 �m long, pink or colourless, and exhibit rounded to

sub-rounded morphologies. There is no obvious correlation

between zircon size, type or colour and age. Of the detrital grains

analysed, 12 of 15 yield concordant ages ranging from c.

1110 Ma to c. 1650 Ma (Figs 8 and 9). The zircon yield for this

sample was particularly low, possibly owing to it having a pelitic

protolith (Fig. 3). Grain 9 constrains the maximum depositional

age of the Kinrovar Schist to 1112 � 67 Ma (weighted mean207Pb/206Pb age of core (spot 9a, concordant but large error) and

rim (spot 9b, discordant) analyses, which are interpreted to be

the same age; Fig. 9). However, a younger maximum deposi-

tional age is possible, as grain 1 (Fig. 6) yields a discordant rim

analysis (spot 1b) interpreted as Pb loss from c. 1000 Ma (Figs 8

and 9; 207Pb/206Pb age for this analysis is 1025 � 44 Ma).

Discordant core data from the same grain suggest Pb loss from c.

1650 Ma (spot 1a), indicating an inherited component (Figs 6

and 9).

Analysis of the zoned rim of grain 8 (spot 8c) yields a

concordia age of 468 � 12 Ma. This rim has a very low Th/U

ratio (0.009) and is interpreted as a post-depositional meta-

morphic overgrowth (Fig. 6), formed during the Grampian

orogeny (Daly & Flowerdew 2005).

Fig. 4. Multi-element plots showing trace

element distributions for (a) C61A,

Doonamo Formation (Erris Group), C62,

Carricklahan Schist (Inishkea Division),

C63, Kinrovar Schist (Inishkea Division),

C66B, Inishkea Division (Tiraun Point) and

C67, Scotch Port Schist (Inishkea Division)

and (b) average values for the samples

plotted in (a) and semipelites from the

Corrieyairack and Glen Spean subgroups of

the Scottish Grampian Group (data from

Winchester & Glover 1988). Data

normalized to Average Upper Crust (AUC;

Taylor & McLennan 1981). Black bar

indicates lower limit of detection.


C67, detrital zircon, Scotch Port Schist, Inishkea Division, Scotch

Port. Zircon grains from sample C67 are 79–110 �m wide and

95–220 �m long, oscillatory-zoned and mostly pink or pinkish

brown, sub-rounded prisms. This sample had a poor zircon yield,

which, as for sample C63, is probably attributable to it having a

pelitic protolith (Fig. 3). Four grains from seven yield concordia

ages of 1186 � 22 Ma, 1252 � 26 Ma, 1264 � 26 Ma and

1520 � 15 Ma (spots 6, 1, 7 and 3, respectively; Fig. 9). The

youngest of these provides a reliable maximum age for the

deposition of the Scotch Port schist. The remaining three grains

(grains 2, 4 and 5), when corrected for the presence of common

Pb, yield concordia ages of 1005 � 22 Ma, 1178 � 27 Ma and

1450 � 25 Ma, respectively (spots 2b, 4a and 5b). The youngest

of these, spot 2b, extends the age limit on the time of deposition

to 1005 � 22 Ma. Ages for grains 2 and 5 are based on analyses

of zircon rims (spots 2b and 5b). Corresponding core analyses

for these grains (spots 2a and 5a) indicate c. 1150 Ma and c.

1620 Ma, inheritance, respectively (Fig. 6).

Discussion

Provenance

Palaeoproterozoic whole-rock Sm–Nd tDM values (1723–

1829 Ma) suggest a similar source for the Erris Group and the

Inishkea Division and all ages are within range of previously

determined Sm–Nd data (Kennedy & Menuge 1992; J. S. Daly

& J. F. Menuge, unpubl. data). �Nd values for both sequences are

consistent with an Annagh Gneiss Complex-type source (Fig. 5;).

The samples analysed have similar chemical compositions with

low Cr/Zr ratios indicative of predominant input from an acidic

source (Winchester & Max 1996). In addition, the samples have

relatively low Zr/Sc ratios suggesting minimal sedimentary

recycling (McLennan et al. 2003), which would suggest that the

detrital zircons are probably first cycle.

U–Pb zircon data from four clasts (K-feldspar and granitoid

clasts) within the Doonamo Formation at Spinkadoon are

consistent with derivation from the structurally underlying

Annagh Gneiss Complex. Two of the K-feldspar clasts (C61B-1,

C61B-10) have identical concordia ages with a weighted mean

value of 1743 � 3 Ma, whereas the third (C61G-7) has a 207Pb/206Pb age of 1750 � 12 Ma. These ages are comparable with the

U–Pb thermal ionization mass spectrometry (TIMS) age of 1753

� 3 Ma for the Mullet gneiss of the Annagh Gneiss Complex

(Daly 1996), which also records c. 1730–1750 Ma crystallization

ages (J. S. Daly, unpubl. data). The clasts are coarser-grained

than the samples dated by Daly (1996), although K-feldspar

megacrystic gneisses are common within the Mullet gneiss (Fig.

2c). Rocks of similar age occur on Rockall Bank (Daly et al.

1995; Fig. 10), but these are characterized by polygonal granular

textures, which are not present in the analysed clasts.

Clast C61D-30 yields a weighted mean 207Pb/206Pb age of 972

� 8 Ma. This age falls within the time range of late Grenville

(Rigolet phase) pegmatite formation and metamorphism recorded

in the Annagh Gneiss Complex (Daly 1996, 2009). An older

discordant zircon in this sample, with a 207Pb/206Pb age of 1022

� 49 Ma (spot 5), is consistent with inheritance from the c.

1015 Ma Doolough Granite (Daly 1996, 2009).

The detrital zircon data tell an entirely different story. The

Erris Group was deposited after c. 955 Ma (concordia age of

youngest detrital zircon from the Doonamo Formation, C61A)

with age peaks of c. 990 Ma, c. 1500 Ma and c. 1640 Ma

dominating the zircon spectra. Deposition of the Inishkea Divi-

sion is tentatively constrained to have been later than c. 1005 Ma

(youngest detrital zircon from the Scotch Port Schist, C67), and

although based on limited data also consists of Mesoproterozoic

detritus with some Neoproterozoic and late Palaeoproterozoic

grains. A single discordant analysis from the Doonamo Forma-

tion (sample C61A, grain 3) points to a detrital contribution from

a c. 1850 Ma source; otherwise, early Palaeoproterozoic and

Archaean detrital zircons are absent in both the Erris Group and

Inishkea Division. However, the absence of age peaks in limited

datasets (e.g. the Inishkea Division) cannot reliably be used to

exclude particular age populations. Conversely, grains present in

small datasets may represent a significant component of the

sediment (Vermeesch 2004; Andersen 2005). The available

sparse detrital zircon data for the Inishkea Division are similar to

those of the Doonamo Formation and a similar provenance for

the two is not unlikely.

The detrital zircon signature of the Doonamo Formation, for

which there are sufficient data for assessment (Andersen 2005),

suggests a more distal source for the majority of the psammitic

detrital zircons than the more locally derived clasts. However,

some grains are compatible with a source similar to the Annagh

Gneiss Complex. Grains from C61A, which fall in the age

bracket of c. 960–1000 Ma, are consistent with Grenville mag-

Fig. 5. Nd evolution diagram showing �Nd

values for Erris Group (C61A) and Inishkea

Division (C62, C63, C66B and C67)

metasediments at inferred time of

deposition (c. 900 Ma). Annagh Gneiss

Complex Nd evolution lines from Menuge

& Daly (1990).


matic and metamorphic events in the Annagh Gneiss Complex.

A single grain in C61A (grain 92, 1184 � 20 Ma) and another

from C67 (grain 4, 1178 � 27 Ma) may correlate with the c.

1177 Ma Doolough gneiss, whereas c. 1270 Ma grains (two in

C61A, five in C63 and two in C67) and c. 1750 Ma grains (three

in C61A) are consistent with derivation from the Cross Point and

Mullet gneisses, respectively (Daly 1996, 2009). Paired core and

rim ages from grain 2 (1152 � 27 Ma and 1005 � 22 Ma,

respectively) from the Scotch Port Schist (C67, Inishkea Divi-

sion), suggest derivation from the c. 1015 Ma Doolough Granite

Fig. 6. CL images of selected zircon grains showing ion microprobe

spots as numbered ellipses labelled with U–Pb ages. White continuous-

line scale bars represent 100 �m; white dashed scale bars represent

50 �m. Single spot ages are given for detrital zircons (all concordia ages

except for those with asterisks, which are 207Pb/206Pb ages and represent

discordant analyses). Concordia ages are shown for zircon from

Doonamo Formation clasts (except C61G-7 and C61D-30, which

represent weighted mean 207Pb/206Pb ages).Fig. 7. Tera–Wasserburg concordia diagrams for zircon from Doonamo

Formation clasts. Ages are concordia ages, except for C61D-30, which is

a weighted mean 207Pb/206Pb age. All errors are 2�. (a) C61B-1: black

continuous-line ellipses represent concordant data used to calculate

concordia age; grey ellipses represent discordant data displaying Pb loss

from c. 1744 Ma; black dashed ellipses with spot numbers represent

discordant data defining discordia age (MSWD ¼ 2.2). (b) C61B-10:

concordant data (black continuous-line ellipses) used to calculate

concordia age (inset); discordant data (grey-filled dashed ellipses with

spot numbers) are the result of Pb loss. (c) C61D-30: concordant data

(black continuous-line ellipses with black spot numbers) and discordant

data (grey-filled ellipses, reversely discordant; dashed ellipses with grey

spot numbers, Pb loss). Weighted mean 207Pb/206Pb age of clast from

concordant and reversely discordant data. Concordant data and spot 1

define discordia (MSWD ¼ 1.5).


with inheritance from the c. 1177 Ma Doolough gneiss (Daly

1996; Fig. 6).

Metamorphism

All post-Grenville deformational events in the Annagh Gneiss

Complex can be matched with events in the overlying metasedi-

ments (Yardley et al. 1987; Kennedy & Menuge 1992; Daly &

Flowerdew 2005) and are demonstrably Grampian (c. 470 Ma) in

age (Daly & Flowerdew 2005). Furthermore, metadolerites that

share the same deformational history as their enclosing metasedi-

ments (the Doonamo Formation and the Scotch Port Schists)

experienced post-metamorphic cooling at c. 450 Ma (Ar–Ar age,

Daly & Flowerdew 2005). In addition, a Grampian (c. 470 Ma)

overgrowth is recorded by one zircon from the Inishkea Division

(Kinrovar Schist, C63, spot 8c) and is interpreted as a post-

depositional overgrowth, consistent with the Rb–Sr muscovite

age of c. 450 Ma obtained from the main foliation by Chew et

al. (2003). A c. 470 Ma Pb loss event is also suggested in the c.

980 Ma clast C61D-30 (discordant data lie along a discordia with

upper and lower intercepts of 965 � 12 Ma and 477 � 79 Ma,

respectively). The geological significance, if any, of the c.

690 Ma lower discordia intercept, recorded in the c. 1740 Ma

clast C61B-1, is unclear at present.

Correlation

Correlation between the Erris Group and the Inishkea Division

seems valid on the basis of whole-rock geochemistry, Sm–Nd

isotopic data and U–Pb detrital zircon ages. The U–Pb detrital

zircon data, although limited for the Inishkea Division, permit

correlation of the Erris Group and the Inishkea Division with the

lowest subdivision of the Dalradian, the Grampian Group

(Cawood et al. 2003; Banks et al. 2007), and with the Moine

Supergroup (Friend et al. 2003; Cawood et al. 2004; Kirkland et

al. 2008). Both the Dalradian Grampian Group and the Moine

Supergroup are characterized by late Palaeoproterozoic peaks,

Mesoproterozoic detritus, some Neoproterozoic detritus and little

if any early Palaeoproterozoic or Archaean detritus (Cawood et

al. 2003, 2004; Friend et al. 2003; Banks et al. 2007; Kirkland et

al. 2008). A correlation with the Moine Supergroup is unlikely

for the Erris Group, however, given its stratigraphic relationship

to the upper parts of the Dalradian in north Mayo (Winchester et

al. 1988; Winchester & Max 1996). Kennedy & Menuge’s (1992)

interpretation of a stratigraphic contact between the Inishkea

Division and overlying Erris Group north of Scotch Port also

supports a Grampian Group affinity for the Inishkea Division.

The lack of Archaean detritus in the Inishkea Division detrital

zircon age spectrum suggests that a correlation with the Dalra-

dian Appin Group, or even the Torridonian, is unlikely (Rainbird

et al. 2001; Cawood et al. 2003; Kinnaird et al. 2007). It must be

pointed out, however, that the detrital zircon data for the Inishkea

Division are not sufficient to reliably rule out possible correla-

tives, as only a small amount of detritus has been sampled in this

study. However, given that detrital grains present in very small

datasets are likely to represent a significant constituent of the

sediment (Vermeesch 2004; Andersen 2005), some Archaean

grains, which are the dominant mode in the Appin Group

(Cawood et al. 2003), might be expected in the Inishkea Division

if an Appin Group correlation was appropriate. Using this

argument, albeit a circular one, it is unlikely that the Kinrovar

Schist has an Appin Group affinity (as suggested by Kennedy &

Menuge 1992). This concurs with geochemical evidence

(Winchester & Max 1988; Max & Winchester 1993) that the

Inishkea Division is compatible only with the lower Dalradian

Grampian Group. The original argument that the Kinrovar Schist

belonged to the Appin Group was based on the assumption that

the rocks at Kildun (Fig. 1), in stratigraphic contact with the

Inishkea Division, were part of the Appin Group (Kennedy &

Menuge 1992). These rocks have since been included in the Erris

Group (Winchester & Max 1996; Fig. 1).

Fig. 8. Number v. zircon age distribution plots for C61A, Doonamo

Formation (Erris Group), C63 Kinrovar Schist (Inishkea Division) and

C67 Scotch Port Schist (Inishkea Division), north Mayo. Ages are

concordia ages except for the youngest grain in C63 (grain 9, 207Pb/206Pb

age). Black boxes with white text denote the age of the youngest zircon

for each sample (2� errors). Dashed rectangle for C63 depicts a

discordant analysis from grain 1 (spot 1b), interpreted as Pb loss from c.

1000 Ma. All other data are concordant (i.e. error ellipses intersect

concordia). Grey bars denote Sm–Nd whole-rock model ages (tDM, Ma)

for each sample. n, number of grains.


Fig. 9. Tera–Wasserburg concordia

diagrams for detrital zircons in sample

C61A, Doonamo Formation (Erris Group)

(black ellipses denote concordant data,

n ¼ 84/99 grains; black-filled ellipse

indicates grain 103, the youngest

concordant analysis; grey-filled ellipses

denote discordant data discussed in the text,

with spot numbers); C67, Scotch Port

Schist (Inishkea Division) (concordant data

with spot numbers, n ¼ 7/7 grains, and spot

5a, an inherited core analysis; grey-filled

ellipses denote common Pb corrected data);

C63, Kinrovar Schist (Inishkea Division)

(black ellipses denote concordant data,

n ¼ 12/15 grains; grey-filled ellipses denote

discordant data discussed in the text, with

spot numbers).

Fig. 10. Rodinia palaeogeography and source regions. (a) Reconstruction of Rodinia at c. 900 Ma adapted from Li et al. (2008). ES, East Svalbard; G,

Greenland; R, Rockall Bank; S, Scotland. Dashed rectangle highlights area in (b). (b) Schematic palaeogeographical reconstruction of the North Atlantic

region c. 900 Ma showing potential source regions for the Dalradian of north Mayo, Ireland. Arrow indicates likely sedimentary transport route. Age of

crustal elements from Ahall & Gower (1997), Rivers (1997) and Daly et al. (2001). Distribution of crustal elements as given by Li et al. (2008). K-M,

Ketilidian–Makkovikian.


Winchester & Max (1996) correlated the Doonamo Formation

with the Corrieyairack Subgroup of the Scottish Grampian Group

on the basis of whole-rock geochemistry (Table 1). As the

chemistry of the Inishkea Division is similar to that of the

Doonamo Formation (Max & Winchester 1993; Fig. 4) and both

have detrital zircon signatures consistent with those of the

Corrieyairack Subgroup (i.e. late Palaeoproterozoic, Mesoproter-

ozoic and early Neoproterozoic detritus; see Banks et al. 2007) it

is proposed that they represent the Irish equivalents to the

Corrieyairack Subgroup (Table 1). However, more data are

needed from the Inishkea Division to properly characterize its

detrital zircon age spectrum. The younger Erris Group forma-

tions (not included in this study) are geochemically similar to the

Glen Spean Subgroup of the Grampian Group (Winchester &

Max 1996; Table 1).

Deposition of the Grampian Group in Ireland is constrained

to have taken place after c. 955 Ma (youngest detrital zircon)

and before c. 470 Ma (Grampian metamorphism of the metase-

diments, Daly & Flowerdew 2005). A Sm–Nd mineral iso-

chron age of 625 � 47 Ma for the Mam Sill that cuts the

Appin Group near Horn Head in Donegal, and a U–Pb zircon

age of c. 590 Ma for a gabbro–pegmatite of a correlative sill

at Dooros Point, Donegal (Kirwan et al. 1989; Daly 2009),

suggests a minimum depositional age of c. 590 Ma for the

Appin Group and, by inference, the Grampian Group in north

Mayo.

Source regions and Neoproterozoic palaeogeography

The Neoproterozoic site of Dalradian deposition is thought to

have occupied a triple-junction position between three major

cratons within the supercontinent Rodinia, Laurentia, Baltica and

Amazonia (Soper 1994; Cawood et al. 2003; Banks et al. 2007;

Fig. 10). The locally derived clasts from the Erris Group (C61B-

1, C61B-10, C61G-7 and C61D-30) support other lines of

evidence, discussed above, that the Annagh Gneiss Complex

represents the depositional basement to the Dalradian in NW

Ireland. Furthermore, the detrital zircon data for the Erris Group

are consistent with a Laurentian provenance with age peaks at c.

1640 Ma, c. 1500 Ma and c. 990 Ma corresponding to Labrador-

ian (c. 1.71–1.60 Ga), Pinwarian (c. 1.51–1.45 Ga) and Grenvil-

lian (c. 1.3–0.95 Ga) terranes, respectively (Rivers 1997;

Wasteneys et al. 1997; Fig. 10). Although the detrital zircon data

for the Inishkea Division are limited they are also consistent with

similar Laurentian sources. Although most of the detrital zircon

grains analysed as part of this study seem to have a more distal

source than the locally derived clasts, some are consistent with

derivation from the Annagh Gneiss Complex (discussed above).

The c. 1300 Ma detritus in both the Erris Group (C61A) and the

Inishkea Division (C63) may have been derived locally from a c.

1310 Ma granitic orthogneiss from the northern Porcupine High,

offshore western Ireland (Daly et al. 2008).

Paired core and rim ages can potentially allow more accurate

identification of their source. However, care must be taken not to

include older core ages in zircon age distribution plots where the

age of the source is constrained by a younger rim analysis. Grain

1 from the Doonamo Formation (C61A; see Fig. 6), with a c. 1.0

Ga overgrowth around a c. 1380 Ma core, is consistent with

derivation from the c. 1.4–1.3 Ga Dysart–Mt. Holly Granitoids

in the western Grenville Province (Rivers & Corrigan 2000).

Grain 2 from the Scotch Port Schist was probably derived from

the Doolough Granite (it yields a rim age within error of the c.

1015 Ma Doolough Granite and a core age within error of the c.

1177 Ma Doolough gneiss; Daly 1996; discussed above) whereas

grain 5, also from the Scotch Port Schist, yields a c. 1620 Ma

Labradorian core and a c. 1450 Ma overgrowth, and was

probably derived from the Pinware Terrane (Wasteneys et al.

1997; Rivers & Corrigan 2000; Heaman et al. 2004; Fig. 10).

Although Baltica offers another possibility for Labradorian-,

Grenville- and Pinwarian-aged sources (within the Sveconorwe-

gian and Svecofennian provinces; Puura & Floden 1999; Ahall &

Connelly 2008; Fig. 10), a Laurentian provenance concurs with

previous interpretations of a westerly derived source for both the

Inishkea Division and the Erris Group (Winchester & Max

1987). Local derivation for the K-feldspar and granitoid clasts

also seems more likely than a Svecofennian origin. Amazonia

can also be excluded for this reason, but more importantly as it

lacks c. 1.7–1.6 Ga magmatic activity (Banks et al. 2007, and

references therein) that could account for the strong c. 1640 Ma

peak in the detrital data. Dalradian deposition is therefore tied to

the margins of Laurentia.

Conclusions

K-feldspar and granitoid clasts from the Erris Group yield U–Pb

zircon ages of c. 1740 Ma and c. 980 Ma, consistent with local

derivation from the underlying Annagh Gneiss Complex. The c.

1640 Ma, c. 1500 Ma and c. 990 Ma peaks in the Erris Group U–

Pb detrital zircon age spectra record more distant Laurentian

sources (Labradorian, Pinwarian and Grenvillian, respectively).

Detrital zircon grains from the Inishkea Division are also

consistent with a Laurentian provenance, but the data are too few

to distinguish any notable peaks. Deposition of the Erris Group

occurred after c. 955 Ma, whereas deposition of the Inishkea

Division is more tentatively constrained to after c. 1005 Ma.

Correlation of the Erris Group and Inishkea Division with the

lower Dalradian Grampian Group is considered valid on the basis

of whole-rock geochemistry and Sm–Nd data, and U–Pb detrital

zircon data (although more detrital zircon data are needed from

the Inishkea Division). The clast data support other lines of

evidence that the Annagh Gneiss Complex represents the deposi-

tional basement to the lower Dalradian in north Mayo, one of the

few such ‘basement–Dalradian cover’ examples preserved. Dalra-

dian deposition can therefore be tied to the margins of Laurentia.

Thanks go to T. Culligan, M. Murphy and P. Haughton (UCD School of

Geological Sciences, University College Dublin) for thin sections,

assistance with TIMS isotopic analysis and sedimentology advice, respec-

tively. L. Ilyinsky and K. Linden are thanked for their help at the

NORDSIM facility, Stockholm. We also thank N. Marsh (University of

Leicester) for XRF analyses. I. Millar and B. Wade are thanked for

careful and insightful reviews. This research was funded by a UCD

Research Demonstratorship and an EU ‘SYNTHESYS’ grant awarded to

C.A.M. and an IRCSET Basic Research grant SC/2002/248 awarded to

J.S.D. This paper is NORDSIM Contribution 253.

References

Aftalion, M. & Max, M.D. 1987. U–Pb zircon geochronology from the

Precambrian Annagh Division gneisses and the Termon Granite, NW County

Mayo, Ireland. Journal of the Geological Society, London, 144, 401–406.

Ahall, K.I. & Connelly, J.N. 2008. Long-term convergence along SW

Fennoscandia: 330 m.y. of Proterozoic crustal growth. Precambrian Research,

161, 452–474.

Ahall, K.I. & Gower, C.F. 1997. The Gothian and Labradorian orogens:

variations in accretionary tectonism along a late Palaeoproterozoic Lauren-

tia–Baltica margin. GFF, 119, 181–191.

Andersen, T. 2005. Detrital zircons as tracers of sedimentary provenance; limiting

conditions from statistics and numerical simulation. Chemical Geology, 216,

249–270.

Banks, C.J., Smith, M., Winchester, J.A., Horstwood, M.S.A., Noble, S.R. &


Ottley, C.J. 2007. Provenance of intra-Rodinian basin-fills: The lower

Dalradian Supergroup, Scotland. Precambrian Research, 153, 46–64.

Belousova, E.A., Griffin, W.L., O’Reilly, S.Y. & Fisher, N.I. 2002. Igneous

zircon: trace element composition as an indicator of source rock type.

Contributions to Mineralogy and Petrology, 143, 602–622.

Brindley, J.C. 1969. Caledonian and pre-Caledonian intrusive rocks of Ireland. In:

Kay, M. (ed.) North Atlantic—Geology and Continental Drift. American

Association of Petroleum Geologists, Memoirs, 12, 336–353.

Cawood, P.A., Nemchin, A.A., Smith, M. & Loewy, S. 2003. Source of the

Dalradian Supergroup constrained by U–Pb dating of detrital zircon and

implications for the East Laurentian margin. Journal of the Geological

Society, London, 160, 231–246.

Cawood, P.A., Nemchin, A.A., Strachan, R.A., Kinny, P.D. & Loewy, S. 2004.

Laurentian provenance and an intracratonic tectonic setting for the Moine

Supergroup, Scotland, constrained by detrital zircons from the Loch Eil and

Glen Urquhart successions. Journal of the Geological Society, London, 161,

861–874.

Cawood, P.A., Nemchin, A.A., Strachan, R., Prave, A.R. & Krabbendam, M.

2007. Sedimentary basin and detrital zircon record along East Laurentia and

Baltica during assembly and breakup of Rodinia. Journal of the Geological

Society, London, 164, 257–275.

Chew, D.M., Daly, J.S., Page, L.M. & Kennedy, M.J. 2003. Grampian

orogenesis and the development of blueschist-facies metamorphism in

western Ireland. Journal of the Geological Society, London, 160, 911–924.

Chew, D.M., Flowerdew, M.J., Page, L.M., Crowley, Q.G., Daly, J.S.,

Cooper, M. & Whitehouse, M.J. 2008. The tectonothermal evolution and

provenance of the Tyrone Central Inlier, Ireland: Grampian imbrication of an

outboard Laurentian microcontinent? Journal of the Geological Society,

London, 165, 675–685.

Crow, M.J. & Max, M.D. 1976. The Kinrovar Schist. Scientific Proceedings of the

Royal Dublin Society, Series A, 5, 429–441.

Crow, M.J., Max, M.D. & Sutton, J.S. 1971. Structure and stratigraphy of the

metamorphic rocks in part of northwest County Mayo, Ireland. Journal of the

Geological Society, London, 127, 579–584.

Daly, J.S. 1996. Pre-Caledonian history of the Annagh Gneiss Complex, north-

western Ireland, and correlation with Laurentia–Baltica. Irish Journal of

Earth Sciences, 15, 5–18.

Daly, J.S. 2001. Precambrian. In: Holland, C.H. (ed.) The Geology of Ireland.

Dunedin Academic Press, Edinburgh, 7–45.

Daly, J.S. 2009. Precambrian. In: Holland, C.H. & Sanders, I.S. (eds) The

Geology of Ireland, 2nd edn. Dunedin Academic Press, Edinburgh, 7–42.

Daly, J.S. & Flowerdew, M.J. 2005. Grampian and late Grenville events recorded

by mineral geochronology near a basement–cover contact in north Mayo,

Ireland. Journal of the Geological Society, London, 162, 163–174.

Daly, J.S., Heaman, L.M., Fitzgerald, R.C., Menuge, J.F., Brewer, T.S. &

Morton, A.C. 1995. Age and crustal evolution of crystalline basement in

western Ireland and Rockall. In: Croker, P.F. & Shannon, P.M. (eds) The

Petroleum Geology of Ireland’s Offshore Basins. Geological Society, London,

Special Publications, 93, 433–434.

Daly, J.S., Balagansky, V.V., Timmerman, M.J., et al. 2001. Ion microprobe

U–Pb zircon geochronology and isotopic evidence for a trans-crustal suture

in the Lapland–Kola Orogen, northern Fennoscandian Shield. Precambrian

Research, 105, 289–314.

Daly, J.S., Tyrrell, S., Badenszki, E., Haughton, P.D.W., Shannon, P.M. &

Whitehouse, M.J. 2008. Mesoproterozoic orthogneiss from the northern

Porcupine High, offshore western Ireland. In: Abstracts, Annual Irish

Geological Research Meeting, University College Dublin, 24.

Dalziel, I.W.D. 1997. Overview: Neoproterozoic–Paleozoic geography and

tectonics: Review, hypothesis, environmental speculation. Geological Society

of America Bulletin, 109, 16–42.

Dempster, T.J., Rogers, G., Tanner, P.W.G., et al. 2002. Timing of deposition,

orogenesis and glaciation within the Dalradian rocks of Scotland: constraints

from U–Pb zircon ages. Journal of the Geological Society, London, 159, 83–

94.

DePaolo, D.J. 1981. Neodymium isotopes in the Colorado Front Range and crust–

mantle evolution in the Proterozoic. Nature, 291, 193–196.

Fitzgerald, R.C., Daly, J.S., Menuge, J.F. & Brewer, T.S. 1994. Mayo

metabasites—a guide to Dalradian/Basement relationships. In: Abstracts,

Annual Irish Geological Research Meeting, University of Ulster at Coleraine,

18.

Fitzgerald, R.C., Daly, J.S., Menuge, J.F. & Brewer, T.S. 1996. Petrogenesis

of the Annagh Gneiss Complex, NW County Mayo, Ireland. In: Abstracts,

Annual Irish Geological Research Meeting, University College Dublin, 23.

Friend, C.R.L., Strachan, R.A., Kinny, P.D. & Watt, G.R. 2003. Provenance of

the Moine Supergroup of NW Scotland: evidence from geochronology of

detrital and inherited zircons from (meta)sedimentary rocks, granites and

migmatites. Journal of the Geological Society, London, 160, 247–257.

Grotzinger, J.P., Bowring, S.A., Saylor, B.Z. & Kaufman, A.J. 1995.

Biostratigraphic and geochronologic constraints on early animal evolution.

Science, 270, 598–604.

Heaman, L.M., Gower, C.F. & Perreault, S. 2004. The timing of Proterozoic

magmatism in the Pinware Terrane of southeast Labrador, easternmost

Quebec and northwest Newfoundland. Canadian Journal of Earth Science,

41, 127–150.

Herron, M.M. 1988. Geochemical classification of terrigenous sands and shales

from core or log data. Journal of Sedimentary Petrology, 58, 820–829.

Hoffman, P.A., Kaufman, A.J., Halverson, G.P. & Schrag, D.P. 1998. A

Neoproterozoic Snowball Earth. Science, 281, 1342–1346.

Hull, E. 1882. On the Laurentian rocks of Donegal and other parts of Ireland.

Scientific Transactions of the Royal Dublin Society, Series 2, 1, 243–256.

Karlstrom, K.E., Bowring, S.A., Dehler, C.M., et al. 2000. Chuar Group of

the Grand Canyon: Record of break-up of Rodinia, associated change in the

global carbon cycle, and ecosystem expansion by 740 Ma. Geology, 28, 619–

622.

Kennedy, M.J. & Menuge, J.F. 1992. The Inishkea Division of northwest Mayo:

Dalradian cover rather than pre-Caledonian basement. Journal of the


Kennedy, M.J. & Menuge, J.F. 1993. Reply to Max, M.D. & Winchester, J.A.

1993. Journal of the Geological Society, London, 150, 606–607.

Kilroe, J.R., 1907. The Silurian and metamorphic rocks of Mayo and north

Galway. Proceedings of the Royal Irish Academy, Section B, 26, 124–160.

Kinnaird, T.C., Prave, A.R., Kirkland, C.L., Horstwood, M., Parrish, R. &

Batchelor, R.A. 2007. The late Mesoproterozoic–Early Neoproterozoic

tectonostratigraphic evolution of Northwest Scotland: The Torridonian

revisited. Journal of the Geological Society, London, 164, 541–551.

Kirkland, C.L., Strachan, R.A. & Prave, A.R. 2008. Detrital zircon signature

of the Moine Supergroup, Scotland: Contrasts and comparisons with other

Neoproterozoic successions within the circum-North Atlantic region. Precam-

brian Research, 163, 332–350.

Kirwan, P.J., Daly, J.S. & Menuge, J.F. 1989. A minimum age for the deposition

of the Dalradian Supergroup sediments in Ireland. Terra Abstracts, 1, 16.

Li, Z.X., Bogdanova, S.V., Collins, A.S., et al. 2008. Assembly, configuration,

and break-up history of Rodinia: A synthesis. Precambrian Research, 160,

179–210.

Ludwig, K.R. 1998. On the treatment of concordant uranium–lead ages.

Geochimica et Cosmochimica Acta, 62, 665–676.

Ludwig, K.R. 2003. User’s Manual for Isoplot 3.00, a Geochronological Toolkit

for Microsoft Excel. Berkeley Geochronology Centre Special Publications, 4,

1–70.

Max, M.D. 1970. Mainland gneisses southwest of Bangor in Erris, northwest

County Mayo, Ireland. Scientific Proceedings of the Royal Dublin Society,

3A, 275–291.

Max, M.D. & Long, C.B. 1985. Pre-Caledonian basement in Ireland and its cover

relationships. Geological Journal, 20, 341–366.

Max, M.D. & Sonet, J. 1979. A Grenville age for pre-Caledonian rocks in NW

Co. Mayo, Ireland. Journal of the Geological Society, London, 136, 379–382.

Max, M.D. & Winchester, J.A. 1993. Discussion on the Inishkea Division of

northwest Mayo: Dalradian cover rather than pre-Caledonian basement

(Ireland). Journal of the Geological Society, London, 150, 605–607.

Max, M.D., Treloar, P.J., Winchester, J.A. & Oppenheim, M.J. 1983. Cr mica

from the Precambrian Erris Complex, NW Mayo, Ireland. Mineralogical

Magazine, 47, 359–364.

Max, M.D., Long, C.B. & MacDermot, C.V. 1992. The Bedrock Geology of

North Mayo (1:100 000). Geological Survey of Ireland, Dublin.

McAteer, C.A., Daly, J.S., Flowerdew, M.J., Connelly, J.N., Housh, T.B. &

Whitehouse, M.J. 2010. Detrital zircon, detrital titanite and igneous clast

U–Pb geochronology and basement–cover relationships of the Colonsay

Group, SW Scotland: Laurentian provenance and correlation with the

Neoproterozoic Dalradian Supergroup. Precambrian Research (in press).

McLennan, S.M., Bock, B., Hemming, S.R., Hurowitz, J.A., Lev, S.M. &

McDaniel, D.K. 2003. The roles of provenance and sedimentary processes

in the geochemistry of sedimentary rocks. In: Lentz, D.R. (ed.) Geochemistry

of Sediments and Sedimentary Rocks: Evolutionary Considerations to Mineral

Deposit-Forming Environments. Geological Association of Canada, New-

foundland, 7–38.

Menuge, J.F. & Daly, J.S. 1990. Proterozoic evolution of the Erris Complex,

Northwest Mayo, Ireland: neodymium isotope evidence. In: Gower, C.F.,

Rivers, T. & Ryan, B. (eds) Mid-Proterozoic Laurentia–Baltica. Geological

Association of Canada, Special Papers, 38, 41–51.

Menuge, J.F. & Daly, J.S. 1994. The Annagh Gneiss Complex in County Mayo,

Ireland. In: Gibbons, W. & Harris, A.L. (eds) A Revised Correlation of

Precambrian Rocks in the British Isles. Geological Society, London, Special

Reports, 22, 59–62.

Phillips, W.E., Kennedy, M.J. & Dunlop, G.M. 1969. Geologic comparison of

western Ireland and northeastern Newfoundland. In: Kay, M. (ed.) North

Atlantic—Geology and Continental Drift. American Association of Petroleum


Geologists, Memoirs, 12, 194–211.

Piasecki, M.A.J. 1980. New light on the Moine rocks of the Central Highlands of

Scotland. Journal of the Geological Society, London, 137, 41–59.

Pin, C., Briot, D., Bassin, C. & Poitrasson, F. 1994. Concomitant separation of

strontium and samarium–neodymium for isotopic analysis in silicate samples,

based on specific extraction chromatography. Analytica Chimica Acta, 298,

209–217.

Puura, V. & Floden, T. 1999. Rapakivi-granite–anorthosite magmatism—a way

of thinning and stabilisation of the Svecofennian crust, Baltic Sea Basin.

Tectonophysics, 305, 75–92.

Rainbird, R.H., Hamilton, M.A. & Young, G.M. 2001. Detrital zircon

geochronology and provenance of the Torridonian, NW Scotland. Journal of

the Geological Society, London, 158, 15–27.

Rivers, T. 1997. Lithotectonic elements of the Grenville Province: review and

tectonic implications. Precambrian Research, 86, 117–154.

Rivers, T. & Corrigan, D. 2000. Convergent margin on southeastern Laurentia

during the Mesoproterozoic; tectonic implications. Canadian Journal of Earth

Sciences, 37, 359–383.

Robertson, S. & Smith, M. 1999. The significance of the Geal Charn–Ossian

Steep Belt in basin development in the Central Scottish Highlands. Journal of

the Geological Society, London, 156, 1175–1182.

Sanderson, D.J., Andrews, J.R. & Phillips, W.E.A. 1980. Deformation studies

in the Irish Caledonides. Journal of the Geological Society, London, 137,

289–302.

Soper, N.J. 1994. Was Scotland a Vendian RRR junction? Journal of the


Stacey, J.S. & Kramers, J.D. 1975. Approximation of terrestrial lead isotope

evolution by a two-stage model. Earth and Planetary Science Letters, 26,

207–221.

Strachan, R.A., Smith, M., Harris, A.L. & Fettes, D.J. 2002. The Northern

Highland and Grampian terranes. In: Trewin, N.H. (ed.) The Geology of

Scotland, 4th edn. Geological Society, London, 81–147.

Sutton, J.S. 1969. The geology of the Mullet Peninsula, Co. Mayo, Ireland. PhD

thesis, Trinity College, University of Dublin.

Sutton, J.S. 1972. The pre-Caledonian rocks of the Mullet Peninsula, County

Mayo, Ireland. Scientific Proceedings of the Royal Dublin Society, 4A, 121–

136.

Sutton, J.S. & Max, M.D. 1969. Gneisses in the north-western part of County

Mayo, Ireland. Geological Magazine, 106, 284–290.

Taylor, S.R. & McLennan, S.M. 1981. The composition and evolution of the

continental crust: rare earth element evidence from sedimentary rocks.

Philosophical Transactions of the Royal Society of London, Series A, 301,

381–399.

Trendall, A.F. & Elwell, R.W.D. 1963. The metamorphic rocks of north-west

County Mayo, Ireland. Proceedings of the Royal Irish Academy, 62b, 217–

247.

van Breemen, O., Bowes, D.R. & Phillips, W.E.A. 1976. Evidence for basement

of late Precambrian age in the Caledonides of western Ireland. Geology, 4,

499–501.

van Breemen, O., Halliday, A.N., Johnson, M.R.W. & Bowes, D.R. 1978.

Crustal additions in late Precambrian times. Geological Journal, Special

Issue, 10, 81–106.

Vermeesch, P. 2004. How many grains are needed for a provenance study? Earth

and Planetary Science Letters, 224, 441–451.

Wasteneys, H.A., Kamo, S.L., Moser, D., Krogh, T.E., Gower, C.F. & Owen,

J.V. 1997. U–Pb geochronological constraints on the geological evolution of

the Pinware terrane and adjacent areas, Grenville Province, southeast

Labrador, Canada. Precambrian Research, 81, 101–128.

Whitehouse, M.J. & Kamber, B.S. 2005. Assigning dates to thin gneissic veins in

high-grade metamorphic terranes: a cautionary tale from Akilia, southwest

Greenland. Journal of Petrology, 46, 291–318.

Wiedenbeck, M., Alle, P., Corfu, F., et al. 1995. Three natural zircon standards

for U–Th–Pb, Lu–Hf, trace element and REE analysis. Geostandards

Newsletter, 19, 1–23.

Winchester, J.A. & Glover, B.W. 1988. The Grampian Group, Scotland. In:

Winchester, J.A. (ed.) Later Proterozoic Stratigraphy of the Northern

Atlantic Regions. Blackie, New York, 146–161.

Winchester, J.A. & Max, M.D. 1984. Geochemistry and origins of the Annagh

Division of the Precambrian Erris Complex, N.W. County Mayo, Ireland.

Precambrian Research, 25, 397–414.

Winchester, J.A. & Max, M.D. 1987. The pre-Caledonian Inishkea Division of

northwest Co. Mayo: its geochemistry and probable stratigraphic position.

Geological Journal, 22, 309–331.

Winchester, J.A. & Max, M.D. 1996. Chemostratigraphic correlation, structure

and sedimentary environments in the Dalradian of the NW Co. Mayo inlier,

NW Ireland. Journal of the Geological Society, London, 153, 779–801.

Winchester, J.A. & Max, M.D. 1988. Pre-Dalradian rocks in NW Ireland. In:



Winchester, J.A., Max, M.D. & Long, C.B. 1988. The Erris Group, Ireland. In:



Yardley, B.W.D., Barber, J.P. & Gray, J.R. 1987. The metamorphism of the

Dalradian rocks of western Ireland and its relation to tectonic setting.

Philosophical Transactions of the Royal Society of London, Series A, 321,

243–270.

Received 13 October 2009; revised typescript accepted 2 April 2010.

Scientific editing by Chris Clark.


A Laurentian provenance for the Dalradian rocks of north Mayo, Ireland, and evidence for an original...

Documents

Transcript of A Laurentian provenance for the Dalradian rocks of north Mayo, Ireland, and evidence for an original...