Accepted Manuscript
Title: The Farsund intrusion (SW Norway): A marker of Late-Sveconorwegian (Grenvillian) tectonism emplaced along a newly defined major shear zone
Authors: Olivier Bolle, Hervé Diot, Jean-Paul Liégeois, Jacqueline Vander Auwera
PII: S0191-8141(10)00050-7 DOI: 10.1016/j.jsg.2010.04.003 Reference: SG 2438
To appear in: Journal of Structural Geology
Received Date: 4 November 2009 Revised Date: 2 April 2010 Accepted Date: 11 April 2010
Please cite this article as: Bolle, O., Diot, H., Liégeois, J.-P., Auwera, J.V. The Farsund intrusion (SW Norway): A marker of Late-Sveconorwegian (Grenvillian) tectonism emplaced along a newly defined major shear zone, Journal of Structural Geology (2010), doi: 10.1016/j.jsg.2010.04.003
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT 1 The Farsund intrusion (SW Norway): a marker of Late-Sveconorwegian (Grenvillian)
2 tectonism emplaced along a newly defined major shear zone
3
4
5 Olivier Bolle a, *, 1, Hervé Diot b, Jean-Paul Liégeois c and Jacqueline Vander Auwera a
6
7 a Dpt. de Géologie, Université de Liège, Bd. du Rectorat – Bât. B20, B-4000 Sart Tilman,
8 Belgium
9 b Pôle Sciences et Technologie, Université de La Rochelle, Av. M. Crépeau, F-17042 La
10 Rochelle Cedex 01, France
11 c Isotope Geology Division, Royal Museum for Central Africa, B-3080 Tervuren, Belgium.
13 14 MANUSCRIPT 15
16 Submitted to the Journal of Structural Geology
17
18
19 Abstract
20 21 The ca. 930 MaACCEPTED Farsund intrusion (SW Norway) belongs to a series of 0.99-0.92 Ga post- 22 collisional plutons from the Sveconorwegian (Grenvillian) orogen. It is made of two rock
23 facies (charnockite and quartz mangerite, and subordinate quartz monzonite and quartz
24 monzodiorite) that show mingling relationships. As shown elsewhere, these two facies
25 belong, respectively, to the two suites of A-type affinity recognized in the Sveconorwegian
1 ACCEPTED MANUSCRIPT 26 post-collisional magmatism of Southern Norway, namely the AMC and HBG suites. A
27 structural study of the Farsund intrusion, based on the anisotropy of magnetic susceptibility
28 (AMS) technique, is presented here. The AMS is controlled by the shape-preferred orientation
29 of low-Ti titanomagnetite grains and it can be used as a proxy for the global petrofabric. The
30 AMS data, when combined with micro- to macrostructural observations, unfold the
31 occurrence of a steeply-dipping shear zone, straddling the NE border of the pluton and
32 characterized by a likely strike-slip component of shearing. This high-strain zone is roughly
33 coincident with the boundary between the outcrop domains of the AMC and HBG suites, and
34 was formed or, more probably, reactivated during the gravitational collapse of the
35 Sveconorwegian orogen, in an extensional (possibly transtensional) tectonic regime. It would
36 have controlled the ascent and emplacement of the Farsund intrusion, and materializes as well
37 the structural weakness that would have channelled the magmas of the neighbouring and
38 coeval Rogaland anorthosite province (RAP). It is also suggested that vertical, gravity-driven 39 movements were recorded in the Farsund intrusion MANUSCRIPT and its close surroundings. They would 40 have been induced in a very hot environment, akin to that prevailing in the Precambrian ultra-
41 hot orogens, but linked in the present case to the emplacement of anorthosites and
42 penecontemporaneous igneous bodies, including the Farsund intrusion.
43
44
45 Keywords: Anisotropy of magnetic susceptibility; Charnockite; Granite emplacement; 46 Transtension; GravityACCEPTED tectonism; Sveconorwegian orogen 47
48
49 * Corresponding author. Tel: +32 4 3662260. Fax: +32 4 3662921. E-mail address:
50 [email protected] (O. Bolle).
2 ACCEPTED MANUSCRIPT 51 1 Research Associate from the F.N.R.S., Belgium.
52
53
54 1. Introduction
55
56 Granitoids occupy an important volume of the continental crust, especially in orogenic
57 belts, and they represent key markers of the Earth’s crust evolution. In particular, it is now
58 well established that granitic plutons are syntectonic in many cases and, hence, that they may
59 be used as markers of crustal deformation at the time of their emplacement, since they are
60 capable of recording tectonic strain in the course of their crystallization, down to solid-state
61 conditions (see the review in Bouchez, 2000). The use of the anisotropy of magnetic
62 susceptibility (AMS) technique (e.g. Rochette et al., 1992; Borradaile and Jackson, 2004) in
63 the structural mapping of granitic plutons has greatly contributed to demonstrate the common 64 syntectonic nature of granitoid emplacement (Bouchez MANUSCRIPT et al., 1990; Archanjo et al., 1994; de 65 Saint Blanquat and Tikoff, 1997; Ferré et al., 1997; Gleizes et al., 1997; Trindade et al., 1999;
66 Benn et al., 2001; Bolle et al., 2003b; Román-Berdiel et al., 2004; Čečys and Benn, 2007;
67 Joly et al., 2007; Henry et al., 2009; among others). In granitoids, the AMS, which is one of
68 various types of magnetic fabrics, arises mostly from the crystallographic- and/or shape-
69 preferred orientation of the magnetic rock-forming minerals; it is representative, in many
70 cases, of the global, usually ill-defined petrofabric which, therefore, can be determined 71 accurately throughACCEPTED AMS measurements (Bouchez, 1997, 2000). 72 We have applied the AMS technique to the ca. 930 Ma Farsund intrusion (Falkum and
73 Petersen, 1974; Falkum et al., 1979; Dupont et al., 2005), which belongs to a series of post-
74 collisional plutons that intruded the Sveconorwegian orogen, a segment of the Grenvillian belt
75 exposed in Southern Norway and SW Sweden, during the early Neoproterozoic (0.99-0.92
3 ACCEPTED MANUSCRIPT 76 Ga). The Farsund intrusion, quite famous in igneous petrology since the term "farsundite" has
77 been proposed as a synonym for hypersthene granite or charnockite (Streckeisen, 1974; but
78 see Wilson, 1977), is supposed to have escaped regional folding (Falkum, 1985, 1998). It is a
79 potentially important marker of the structural and petrological evolutions of the
80 Sveconorwegian post-collisional magmatism, given its likely location near a major
81 lithotectonic boundary (Duchesne et al., 1999; Vander Auwera et al., subm.).
82
83 2. Geological setting
84
85 2.1. The Sveconorwegian orogen
86
87 The Sveconorwegian orogen forms the southwestern, youngest portion of the Baltic
88 Shield (the exposed part of Fennoscandia; Fig. 1a). This orogen is covered by Caledonian 89 nappes to the west and is truncated by the Late MANUSCRIPT Carboniferous–Permian Oslo graben in its 90 central part. It is divided into several N-S to NW-SE–trending crustal segments (or terranes)
91 made of Paleo- to Mesoproterozoic crust reworked during the 1.14-0.90 Ga Sveconorwegian
92 orogeny (Bingen et al., 2008b; Bogdanova et al., 2008) and separated by major shear-zones.
93 Models of terrane juxtaposition during the Sveconorwegian orogeny (see Bingen et al., 2005,
94 2008b for recent contributions and references) evoke thrusting of allochton terranes on the
95 easternmost, parautochtonous domain of the orogen and large, sinistral relative displacements 96 between these terranesACCEPTED along the N-S–trending orogen-parallel shear zones, during collision 97 between the SW margin of Fennoscandia and another major plate, possibly Amazonia. The
98 strike-slip component of movement points to an oblique collision and indicates a
99 transpressive tectonic regime at the orogen scale.
4 ACCEPTED MANUSCRIPT 100 Numerous post-collisional plutons, dated at 0.99-0.92 Ga (compilation of U-Pb ages and
101 new data in Bingen et al., 2008b), occur in the Sveconorwegian orogen (Fig. 1a). They are
102 dominated by biotite or hornblende + biotite (rarely biotite + muscovite), metaluminous to
103 slightly peraluminous granitoids (Bogaerts et al., 2003; Eliasson et al., 2003; Vander Auwera
104 et al., 2003). These granitic plutons form two roughly N-S–trending belts across the orogen
105 (Fig. 1a). The first belt (Andersen et al., 2001; Eliasson et al., 2003), to the east, encompasses
106 three major plutons (the Flå, Iddefjord and Bohus granites) that are elongated parallel to the
107 boundary of two terranes. The second belt (Andersen et al., 2001; Vander Auwera et al.,
108 2003, 2008), to the west, is larger and occurs mostly to the west of the Mandal–Ustaoset Line,
109 a lineament materialized by faults and shear zones that is generally regarded as a lithospheric-
110 scale discontinuity (Sigmond, 1985; Bingen and van Breemen, 1998). Anorthosite to
111 charnockite plutons occur to the SW of the western granitic belt (Duchesne et al., 1985;
112 Duchesne, 2001; see also next section). 113 The post-collisional plutons were mostly emplaced MANUSCRIPT during the 0.97-0.90 Ga Dalane phase, 114 as defined by Bingen et al. (2008b) in their four-phase model of the Sveconorwegian
115 orogeny. The Dalane phase corresponds to a gravitational collapse of the orogen,
116 characterized by core complex and gneiss dome formation (Bingen et al., 2006), and ductile
117 to brittle normal reactivation or overprinting of the major shear-zones (Andréasson and
118 Rodhe, 1990; Starmer, 1993; Mulch et al., 2005).
119 120 2.2. The RogalandACCEPTED–Vest-Agder sector 121
122 The Farsund intrusion is exposed to the west of the Mandal–Ustaoset Line, in the
123 Rogaland–Vest-Agder sector (Fig. 1a, b). This sector consists of a high-grade gneiss complex,
124 intruded by several post-collisional plutons.
5 ACCEPTED MANUSCRIPT 125 The high-grade gneiss complex is made of three lithological units (Fig. 1b; Falkum, 1985,
126 1998): banded, granitic and augen gneisses. The banded gneiss consists of alternating
127 quartzofeldspathic and mafic (amphibolite or metanorite) layers, typically 1- to 50-cm-thick
128 and is variably migmatitic. It contains small bodies of amphibolite and pyroxene-rich
129 gneisses, as well as intercalations of metasediments (garnetiferous gneiss and schist,
130 metaquartzite, calc-silicate rocks, marble). The granitic gneiss is a locally augen-bearing,
131 faintly-foliated orthogneiss. Available U-Pb dates of banded and granitic gneisses indicate
132 protolith formation between 1.55 and 1.03 Ga (summary in Bingen et al., 2008b). Most augen
133 gneiss bodies are metamorphosed megacrystic granodiorite plutons of the syn-collisional
134 (1.05 Ga) high-K calc-alkaline Feda suite (Fig. 1a; Bingen and van Breemen, 1998). A few
135 minor augen gneiss bodies belong to the pre-collisional (1.19-1.15 Ga) A-type Gjerstad suite
136 that occurs all-over Southernmost Norway (Zhou et al., 1995; Bingen and van Breemen,
137 1998). 138 The post-collisional plutonism in the Rogaland MANUSCRIPT–Vest-Agder sector is represented by two 139 petrographically, chemically and geographically distinct suites of A-type affinity (Fig. 1b;
140 Vander Auwera et al., 2003): a hornblende + biotite ferro-potassic granitoid (HBG) suite
141 described all over Southern Norway and an orthopyroxene-bearing or anorthosite-mangerite-
142 charnockite (AMC) suite restricted to the Rogaland–Vest-Agder sector. The plutons defining
143 the HBG suite belongs to the western granitic belt of the Sveconorwegian orogen (Fig. 1a). U-
144 Pb geochronology dates their emplacement at 0.96-0.95 Ga in the Rogaland–Vest-Agder 145 sector (Vander AuweraACCEPTED et al., subm.), as best defined by the 950 ± 5 Ma Lyngdal granodiorite 146 (Bogaerts et al., 2003, 2006) and the 957 ± 7 Ma Holum monzogranite (Bolle et al., 2003b;
147 Bingen et al., 2006) (see Fig. 1b for location). The AMC suite is defined by the Rogaland
148 anorthosite province (RAP; Fig. 1b; Duchesne et al., 1985; Duchesne, 2001), a huge igneous
149 complex that mainly consists of four coalescent large intrusions (the Egersund-Ogna, Åna-
6 ACCEPTED MANUSCRIPT 150 Sira and Håland-Helleren anorthosites, and the Bjerkreim-Sokndal layered intrusion, BKSK)
151 and two outliers (the Hidra and Garsaknatt leuconorites). The RAP was built in a short period
152 of time, at 0.93-0.92 Ga (U-Pb ages; Pasteels et al., 1979; Schärer et al., 1996; Vander
153 Auwera et al., subm.). Some composite plutons containing hornblende + biotite and
154 orthopyroxene granitoids are found in the vicinity of the RAP (Fig. 1b). The Farsund
155 intrusion, which extends the RAP towards the SE, is the most voluminous of them.
156 The metamorphic grade in the Rogaland–Vest-Agder gneiss complex increases
157 westwards, from upper amphibolite to granulite facies, as reflected by a sequence of four
158 isograds (Fig. 1b; Tobi et al., 1985; Bingen et al., 1996): clinopyroxene-in, orthopyroxene-in,
159 osumilite-in and (inverted) pigeonite-in isograd. This isograd pattern results from the
160 superposition of three Sveconorwegian metamorphic events, dated by U-(Th)-Pb
161 geochronology (Möller et al., 2003; Tomkins et al., 2005; Bingen et al., 2008a): M1, a
162 medium-P, regional metamorphic stage linked to crustal thickening (1.035-0.97 Ga); M2, a 163 low-P – high- to ultra-high-T stage induced by the MANUSCRIPT multi-emplacement of the RAP (0.93-0.92 164 Ga); M3, a low-P retrograde stage related to post-M2 cooling. U-(Th)-Pb data also
165 demonstrates that the orthopyroxene isograd is a composite M1–M2 isograd, while the
166 pigeonite, osumilite and clinopyroxene isograds relate to M2 (Möller et al., 2003; Bingen et
167 al., 2008a). This latter phase represents a major thermal event, reflecting the superimposition
168 of penecontemporaneous magmatic heat pulses, for which various geothermobarometres
169 indicate peak temperatures of 800°C to > 1000°C close to the RAP and 700-750°C in the 170 vicinity of the orthopyroxeneACCEPTED isograd, at pressures of about 5 kbar (Wilmart and Duchesne, 171 1987; Holland et al., 1996; Westphal et al., 2003; and references therein).
172 The high-grade gneisses were affected by at least four to six phases of folding (Huijsmans
173 et al., 1981; Falkum, 1985, 1998; Starmer, 1993). The first, most probably pre-
174 Sveconorwegian and composite phase produced mesoscopic to large-scale isoclinal folds with
7 ACCEPTED MANUSCRIPT 175 axial plane foliation, whereas the next phases gave rise to N-S–trending large-scale folds,
176 with gradually greater interlimb angles (isoclinal to close folds), steeper axial planes
177 (presumably recumbent to upright folds) and smaller amplitudes. These superimposed folds
178 are coeval with high-grade metamorphism. The last phase of deformation is an exception,
179 since it produced gentle to open large-scale folds, commonly along E-W axes and, apparently,
180 without any related metamorphic recrystallization. Following Falkum (1998), most
181 superimposed folds, with the notable exception of the latest ones, successively developed
182 along the same N-S–trending axis, in response to syn-orogenic E-W horizontal shortening.
183 The emplacement of both the HBG and AMC suites in the Rogaland–Vest-Agder sector is
184 coeval with regional-scale ductile deformation, responsible for some of the youngest folds
185 observed in the high-grade gneiss complex (Falkum, 1998; Bolle et al., 2003b; Bingen et al.,
186 2006). Ductile, gravity tectonism within the RAP, namely diapiric emplacement of the
187 Egersund-Ogna, Åna-Sira and Håland-Helleren anorthosites (Duchesne et al., 1985; 188 Barnichon et al., 1999) and gravity-driven subsidence MANUSCRIPT of the BKSK (Paludan et al., 1994; 189 Bolle et al., 2000, 2002), is also a well established feature. All these evidence for late-
190 Sveconorwegian ductile deformation overlapping with post-collisional plutonism were taken
191 by Bingen et al. (2006) as arguments, among other evidence, to interpret the Rogaland–Vest-
192 Agder high-grade domain as a large-scale gneiss dome, progressively exhumed between 0.96
193 and 0.92 Ga, during, and possibly triggered by, the production of the HBG and AMC suites.
194 195 3. Petrology andACCEPTED field structural description of the Farsund intrusion and its country 196 rocks
197
198 The Farsund intrusion is a NW-SE elongated pluton which crops out over an area of ca.
199 105 km2, on peninsulas and islands that are separated from each other by fjords (Fig. 2). The
8 ACCEPTED MANUSCRIPT 200 country rocks to the north consist of alternating units of banded and granitic gneisses, with a
201 major body of augen gneiss (the Feda gneiss) belonging to the 1.05 Ga Feda suite. To the
202 south, the intrusion is flanked by banded gneisses. The gneisses are in amphibolite facies to
203 the NE, and in granulite facies to the NW and to the south (Falkum et al., 1979; Falkum,
204 1982, 1998). The southern banded gneisses are partly covered by Quaternary moraines and,
205 opposing most geological maps (e.g. Middlemost, 1968; Falkum et al., 1979), we propose that
206 these deposits also hide a portion of the Farsund intrusion (Fig. 2; see argument below). The
207 intrusion borders the Lyngdal granodiorite and the Hidra leuconorite, respectively to the SE
208 and to the NW, and is locally separated from these two plutons by a thin septum of gneiss
209 (Fig. 2; Falkum et al., 1972, 1979; Marker et al., 2003).
210 The Farsund intrusion is made of two intermingled facies, i.e. two facies showing
211 mingling relationships, whose petrography and spatial distribution cannot be shown on Fig. 2
212 and will be detailed below: a dominant dark facies containing orthopyroxene (here referred to 213 as Opx facies), and a subordinate light facies containing MANUSCRIPT hornblende and biotite (here referred 214 to as Hbl + Bt facies). Both facies display relatively coarse-grained varieties (charnockite and
215 quartz mangerite vs. mostly quartz monzonite, with grain size ≤ ca. 1 cm), that are locally
216 intermingled with several-dm- to some-km-sized finer-grained bodies (charnockite and quartz
217 mangerite vs. mostly quartz monzodiorite, with grain size ≤ ca. 5 mm). The coarser-grained
218 varieties also contain cm- to some-dm-large mafic microgranular enclaves. Zircon U-Pb
219 geochronology gives similar ages for the two facies (931 ± 2 Ma for the Opx facies and 926 ± 220 4 Ma for the HblACCEPTED + Bt facies; Dupont et al., 2005), confirming their coeval character. Whole- 221 rock and mineral chemistry, and Sr and Nd isotope data further prove that the Opx and Hbl +
222 Bt facies belong to the AMC and HBG suites, respectively (Dupont et al., 2005). The AMC
223 and HBG sources were thus both involved in the genesis of the Farsund magmas. The age of
224 ca. 930 Ma also implies that the emplacement of the Farsund intrusion is contemporaneous
9 ACCEPTED MANUSCRIPT 225 with the multi-emplacement of the RAP and, thus, participated to the heat production
226 responsible for the high- to ultra-high-T M2 metamorphic event.
227 The pluton contains numerous gneiss xenoliths of variable nature, that appear to come
228 mainly from the banded gneisses. Most of these xenoliths are rather small (from a-few-cm- to
229 1-m-large). A huge gneiss body in the SE central part of the pluton (Fig. 2), dissected by the
230 surrounding magmas, may represent a roof pendant or a remnant (pinnacle) of the underlying
231 floor. Dykes of aplite and pegmatite are scarce, and always thin (cm- to dm-large).
232 A foliation and a mineral lineation, mainly defined by a shape-preferred orientation (SPO)
233 of feldspars and mafic aggregates, are visible in the pluton. The mafic microgranular enclaves
234 and the gneissic xenoliths are aligned with the foliation that is usually well-defined, contrary
235 to the lineation which is only locally well-expressed (see below). The foliation dips are
236 always steep and the strikes are dominantly NW-SE, except to the SW where they
237 progressively rotate westwards from NW-SE, through E-W, to SW-NE, revealing folding of 238 the southern part of the pluton (Fig. 2). Moreover, MANUSCRIPT the SW-NE–striking foliations abut against 239 the northern limit of the moraine cover, which may be taken as an argument for the
240 occurrence of a pluton lobe under the Quaternary deposits, as we propose in Fig. 2. It is also
241 worth noting that the exposed margins of the pluton seem to be generally steep, in agreement
242 with the steeply-dipping foliations.
243 The SPO degree progressively increases to the NE, with mafic aggregates being more and
244 more stretched and wrapped around feldspars, and it reaches a maximum in an up to 1.5-2- 245 km-large zone alongACCEPTED the contact with the high-grade gneisses. In this more deformed zone, 246 strain localization (strong grain size reduction and very strong SPO, associated with L-fabrics
247 or dm-scale close to isoclinal folds and ductile shear-zones) occurs at the margin and in
248 narrow corridors. Well-defined lineations, as locally measured in the latter zones of strain
249 localization, have plunges of ca. 30° towards the SE or SSE (Fig. 2). In the high-grade
10 ACCEPTED MANUSCRIPT 250 gneisses, gneissic foliations and mineral lineations concordant with the structures in the more
251 deformed zone along the NE contact are found up to 1-2 km away from the margin (Fig. 2).
252 Hence, our field structural observations unfold the occurrence of a few-km-large steeply-
253 dipping and roughly linear belt, that straddles the NE border of the Farsund intrusion and
254 which we interpret as a ductile shear zone (here referred to as the Farsund shear zone), given
255 the obvious mylonitization of the pluton associated with it.
256 To the north of the pluton, outside the Farsund shear zone, the gneissic foliations and the
257 most common types of lineations in the metamorphic envelope, namely mineral and
258 crenulation lineations, exhibit a more complicated pattern, resulting from fold interference
259 (Fig. 2; Falkum, 1998). To the south, the banded gneisses draw a large-scale antiform or
260 dome, with associated mineral lineations that are gently to moderately plunging,
261 predominantly to the NNE (Fig. 2). The foliation pattern in the south of the Farsund intrusion
262 is concordant with this folded structure, at the map scale. 263 In summary, the Farsund intrusion is concordant MANUSCRIPT with the regional structure observed in 264 the gneisses near the margins: the pluton is elongated parallel to a steeply-dipping shear zone
265 that straddles the NE margin (the Farsund shear zone) and it is concordant to a large-scale
266 antiform or dome to the south. Let us note that the foliations in the Farsund intrusion are
267 parallel to that measured in the huge gneiss body found in the SE central part of the pluton
268 (Fig. 2).
269 The Lyngdal granodiorite, as the Farsund intrusion, exhibits a penetrative, usually steeply- 270 dipping foliation.ACCEPTED In the main E-W–trending body of the pluton (see location on Fig. 1b), the 271 foliations are dominantly E-W–striking, whereas in the ca. N-S–striking limb extending to the
272 north (Fig. 1b), they are NE-SW–striking in average (Fig. 2; Middlemost, 1968; Falkum et
273 al., 1979; Falkum, 1982). In the vicinity of the Farsund intrusion, the foliation strikes
274 progressively evolve westwards from E-W to NNW-SSE or even N-S, and the foliation
11 ACCEPTED MANUSCRIPT 275 pattern is concordant with that of the Farsund intrusion and the banded gneisses to the SW
276 (Fig. 2). However, around the city of Farsund, the foliations in the Farsund intrusion run
277 parallel to the contact with the Lyngdal granodorite and are clearly oblique to the planar
278 fabrics in the latter pluton (Fig. 2). In the same area, up to 1-m-large ductile shear zones,
279 oblique to the earlier foliation, are locally observed in the Lyngdal granodiorite, up to 500-
280 600 m away from the margin. These shear-zones are moderately- to steeply-dipping (ca. 50-
281 80°) and are trending parallel to the contact with the Farsund intrusion. In agreement with
282 Falkum et al. (1972, 1979), we conclude that the foliation deflection in the Farsund intrusion
283 and the shearing in the Lyngdal granodiorite, as locally observed along the contact between
284 the two plutons, were induced during emplacement of the ca. 930 Ma Farsund intrusion and
285 its expansion at the expense of the already crystallized ca. 950 Ma Lyngdal granodiorite.
286 Moreover, N- to ENE–plunging mineral lineations with moderate to steep plunges occur
287 around the Farsund city, on each side of the contact between the Farsund intrusion and the 288 Lyngdal granodiorite (Fig. 2; Falkum et al., 1979 ),MANUSCRIPT pointing to a common strain history for the 289 two plutons, at least locally.
290 A few field observations conducted in the Hidra leuconorite reveal the occurrence of a N-
291 S–striking and steeply-dipping, rough penetrative foliation, mainly defined by a SPO of
292 orthopyroxene grains. The steeply-dipping foliation pattern in the Farsund intrusion is
293 roughly concordant with that evidenced in the Hidra leuconorite, but is slightly deflected
294 towards parallelism with the margin when approaching the leuconorite body (Fig. 2). Such a 295 foliation deflectionACCEPTED is associated with the development of a mylonitic zone in the Farsund 296 intrusion, extending all along the eastern margin of the Hidra leuconorite, up to a few
297 hectometres away from the contact (Fig. 2). This high-strain zone (here referred to as the
298 Hidra mylonitic zone) is characterized, at the outcrop scale, by a grain size reduction and by
299 strongly stretched mafic aggregates wrapped around feldspar porphyroclasts; quartz and
12 ACCEPTED MANUSCRIPT 300 feldspar ribbons are also observed in narrow corridors of strain localization. In the northern,
301 tongue-like end of the Farsund intrusion (see location on Fig. 2), the mylonitization is
302 superimposed on strained rocks from the Farsund shear zone, giving rise to very well-
303 developed quartz and feldspar ribbons, and an extremely strong SPO. Geochronologically, the
304 Farsund intrusion and the Hidra leuconorite are penecontemporaneous, at ca. 930 Ma
305 (Pasteels et al., 1979; Dupont et al., 2005) and, at this stage of the study, we ascribe formation
306 of the Hidra mylonitic zone to the emplacement of the Hidra leuconorite shortly after
307 crystallization of the Farsund intrusion.
308
309 4. Sampling and analytical procedures
310
311 One hundred and twenty-five sites have been sampled for AMS measurements (Fig. 3;
312 Table 1). Most of them (114) are located in the Farsund intrusion. Eleven localities were also 313 sampled in the Lyngdal granodiorite, in the junction MANUSCRIPT area between the main body and the 314 northern limb of the pluton. The samples consist of oriented cylinders (25 mm in diameter),
315 cored with a portable drill. A total of 261 cores was collected (usually two cores per site).
316 The upper part of each core has been cut, in the laboratory, into two, rarely one, 22-mm-
317 high cylinder(s), providing 520 specimens (usually four per site). The AMS of each specimen
318 was measured, in a low magnetic field, using the Kappabridge KLY–3S susceptometer of
319 AGICO Ltd. Measurements provided the magnitude and orientation of the three principal 320 axes of the ellipsoidACCEPTED describing AMS in a low magnetic field (K1 ≥ K2 ≥ K3). An average 321 ellipsoid was calculated from the AMS measurements, for each sampling site, following the
322 tensor averaging method of Hext (1963).
323 The lower part of the cores were used to make (sometimes polished) thin sections, in
324 order to characterize the petrography of each sampling site. Thin sections from forty-three
13 ACCEPTED MANUSCRIPT 325 hand-size samples from the Farsund intrusion (most of them analyzed for geochemical
326 purpose by Dupont, 2004) were also integrated in the present study.
327
328 5. Petrography and microstructural description of the sampled area
329
330 5.1. Petrography and mineral chemistry
331
332 Our microscope examination of the AMS samples confirms and completes previous
333 petrographical descriptions of the Farsund intrusion and the Lyngdal granodiorite
334 (Middlemost, 1968; Falkum et al., 1979; Bogaerts et al., 2003, 2006; Dupont, 2004).
335 Alkali feldspar, plagioclase and quartz, as main rock-forming minerals, zircon, apatite, and
336 sporadic allanite and sulfides (pyrite, pyrrhotite, chalcopyrite), as accessory minerals, are
337 shared by all facies. Orthopyroxene, clinopyroxene, hornblende, biotite, titanite, ilmenite and 338 magnetite are also present, as main or accessory MANUSCRIPT minerals, but their occurrence and 339 proportions vary according to the lithology (Table 1): (1) in the Opx facies, the Fe-Mg
340 silicates are orthopyroxene, hornblende, and subordinate clinopyroxene and biotite, titanite is
341 markedly absent, and ilmenite is usually dominating over magnetite; (2) in the Hbl + Bt
342 facies, as well as in the Lyngdal granodiorite, the Fe-Mg silicates are hornblende, biotite
343 (absent in some samples) and sporadic clinopyroxene, titanite is a notably abundant accessory
344 in many samples, and magnetite is more abundant than in the Opx facies and it is dominating 345 over ilmenite. TheACCEPTED high magnetite vs. ilmenite ratio and the occurrence of titanite in the Hbl + 346 Bt facies and the Lyngdal granodiorite reflect the oxidizing character of the HBG magmas
347 (Vander Auwera et al., 2003) from which they crystallized. Moreover, hornblende may be
348 more or less abundant than orthopyroxene in the Opx facies, which allows to distinguish
349 between an Opx + Hbl sub-facies (orthopyroxene content ≥ hornblende content) and a Hbl +
14 ACCEPTED MANUSCRIPT 350 Opx sub-facies (hornblende > orthopyroxene, with biotite being locally a relatively abundant
351 accessory; Table 1). Hornblende is usually dominating over biotite in the Hbl + Bt facies, as
352 well as in the Lyngdal granodiorite (Table 1).
353 Quartz typically forms anhedral, usually irregular grains. Plagioclase is an oligoclase to
354 basic andesine (An22-35; Wilson, 1977; Falkum et al., 1979; Bogaerts et al., 2003, 2006;
355 Dupont, 2004), that may be antiperthic in the Farsund intrusion. It is subhedral and locally
356 weakly zoned. Alkali feldspar varies from microperthitic orthoclase to microperthitic
357 microcline, the latter being extensively developed in the Lyngdal granodiorite only.
358 Mesoperthite is also common in the Opx facies. Myrmekite intergrowths at feldspar grain
359 boundaries are very abundant. Orthopyroxene is mostly ferrosilitic (Dupont, 2004), and
360 occurs both as oikocrysts of inverted pigeonite and subhedral (locally prismatic) primary
361 grains. Clinopyroxene in the Opx facies is augitic (Dupont, 2004) and forms exsolution
362 lamellae in orthopyroxene, as well as small grains or granules. It is diopsidic in the Lyngdal 363 granodiorite (Bogaerts et al., 2003, 2006) and in theMANUSCRIPT Hbl + Bt facies, where it is found only as 364 small relic inclusions in hornblende. Hornblende belongs to the hastingsite-edenite group
365 (Bogaerts et al., 2003, 2006; Dupont, 2004). It makes up grains of variable size and shape
366 (including oikocrysts), as well as, in the Opx facies, rims around the Fe-Ti oxides. Biotite is
367 subhedral to euhedral. Titanite rims the oxides or is found as small, usually anhedral grains.
368 Ilmenite is optically homogeneous, except in some samples from the Lyngdal granodiorite,
369 where it shows tiny hematite exsolutions. Magnetite is a Ti-poor titanomagnetite (Dupont, 370 2004) and exhibitsACCEPTED evidence of subsolidus reactions (mostly trellis and sandwich 371 microstructures formed by ilmenite lamellae; Duchesne, 1972) that are common in the
372 Farsund intrusion only. Apatite, locally zoned zircon and sporadic allanite make up small,
373 usually euhedral grains.
15 ACCEPTED MANUSCRIPT 374 The rock texture is subhedral in the Farsund intrusion, where it evolves from
375 inequigranular to equigranular from the coarse-grained facies (average grain size of 2-4 mm),
376 through the fine-grained-facies (ca. 1-2 mm), to the microgranular enclaves (ca. 500 m).
377 Chilled facies is common in the latter, with apatite needles and Fe-Ti oxide grains dispersed
378 in the other minerals. Samples from the Lyngdal granodiorite are coarse-grained (average
379 grain size of 2-5 mm) and display a subhedral inequigranular texture, with frequent
380 phenocrysts of plagioclase and/or alkali feldpsar, up to ca. 1-cm-long. In the coarse-grained
381 rocks, aggregation of the Fe-Mg silicates and other accessory minerals, into more or less
382 elongated clusters, is usually a rule.
383 Alteration is weakely developed, except in a few samples. It is expressed by
384 damouritisation of feldspars, transformation of orthopyroxene into an orange-brown to rusty
385 mineral (possibly iddingsite; Falkum et al., 1979) plus pyrite or magnetite, chloritization of
386 biotite (chlorite being accompanied by sericite, pistachitic epidote, calcite and/or pyrite in the 387 Hbl + Bt facies and in the Lyngdal granodiorite) MANUSCRIPT and corrosion of pyrite by a rusty rim 388 (possibly Fe-hydroxide). Microfractures filled with chlorite, calcite, magnetite or pyrite
389 locally cut across the mineral assemblage.
390
391 5.2. Distribution of the petrographic facies in the Farsund intrusion
392
393 A large zone of Hbl + Bt facies occurs in the west of the pluton and seems to be distributed 394 along the trend ACCEPTEDof the folded pattern drawn by the foliations in the area. This facies is also 395 observed along the western boundary of the huge gneiss body in the SE central part of the
396 pluton and, more locally, close to the NE margin in the Farsund shear zone (Fig. 3). The Hbl
397 + Opx sub-facies tends to concentrate in the core of the pluton, while the Opx + Hbl sub-
16 ACCEPTED MANUSCRIPT 398 facies tends to occur mostly close to the margins, and to the north and south of the main zone
399 of Hbl + Bt facies (Fig. 3). Hence, the Farsund intrusion displays a roughly defined zonation.
400 Most samples of the Hbl + Opx sub-facies that are spatially associated with the Hbl + Bt
401 facies actually belong to the HBG suite (Fig. 3), despite they contain orthopyroxene, as
402 demonstrated by chemical (whole-rock and mineral) and isotopic (Sr and Nd) data obtained at
403 the AMS sites, either on hand-size samples or on the AMS samples themselves (Dupont,
404 2004; Vander Auwera and Bolle, work in progress). For example, the hornblende Fe#
405 [Fe/(Fe+Mg) cationic ratio] in the Hbl + Bt facies and in the associated Hbl + Opx sub-facies
406 are similar (0.59-0.65, down to 0.45 in titanite-bearing rocks), but lower to that of the Opx +
407 Hbl and Hbl + Opx sub-facies, as found elsewhere in the pluton (0.73-0.81). A complete
408 geochemical investigation of the Farsund intrusion is outside the scope of the present study
409 and will be conducted in a separated paper (Vander Auwera and Bolle, work in progress).
410 Finally, fine-grained lithologies make an important part of the HBG zones, while fine-grained 411 AMC rocks are anecdotal (Fig. 3; Table 1). MANUSCRIPT 412
413 5.3. Microstructures
414
415 Minerals from the two sampled plutons display various microscope-scale evidence of
416 ductile deformation. The quartz microstructure ranges from a slight undulose extinction to a
417 well-defined pattern of subgrains (Fig. 4a, b). The largest grains of alkali feldspar and 418 plagioclase are alsoACCEPTED frequently undulatory. Curvature of polysynthetic twins in the plagioclase 419 is quite common, but usually weak (Fig. 4c), and very rare mechanical twins are also
420 observed in this mineral. Slight curvature or kinking may affect some primary grains of
421 orthopyroxene (Fig. 4d). In addition, the quartz-quartz and feldspar-feldspar grain boundaries
422 are commonly serrated, suggesting dynamic recrystallization through high-T grain boundary
17 ACCEPTED MANUSCRIPT 423 migration (Hirth and Tullis, 1992; Passchier and Trouw, 2005). The high-T conditions of the
424 deformation (>500-600°C) is also attested by frequent irregular quartz-feldspar grain
425 boundaries (Fig. 4e), the dominantly square shape of quartz subgrains (Fig. 4a) and the
426 abundance of myrmekites (Passchier and Trouw, 2005; and references therein). Such high
427 temperatures are coherent with a ductile strain acquired at the end of or shortly after magma
428 crystallization and also comply, at least for the Farsund intrusion, with the thermal conditions
429 of the high- to ultra-high-T M2 metamorphic event. Quartz grains with elongated subgrains,
430 usually occurring together with grains that display square-shaped subgrains, are also locally
431 observed, essentially in the Lyngdal granodiorite (Fig. 4b), pointing to deformation at slightly
432 lower temperatures (Passchier and Trouw, 2005).
433 In the Farsund shear zone, microstructural peculiarities, compared to less-deformed areas,
434 are mostly observed in the zones of strain localization (narrow corridors and along the
435 margin) and consist of a higher rate of intracrystalline deformation in quartz and feldspars, 436 and an increase of the number of quartz grains with MANUSCRIPT elongated subgrains. In the portion of the 437 Lyngdal granodiorite affected by the emplacement of the Farsund intrusion, microstructural
438 peculiarities consist of locally well-developed elongated subgrains in large grains of quartz
439 associated with abundant aggregates of small quartz grains (probably new grains developed
440 by dynamic recrystallization made predominantly through subgrain rotation; Hirth and Tullis,
441 1992; Fig. 4b). Rocks from the Hidra mylonitic zone exhibit very peculiar microstructural
442 features, namely a fine-grained matrix (average grain size of 0.5-1 mm) containing large 443 grains of quartzACCEPTED and alkali feldspar (<1 cm) that range from more or less elongated 444 porphyroclasts to ribbons with shape ratios of 1/3 up to 1/7 and which usually show few
445 evidence of intracrystalline deformation (Fig. 4f); strongly ductily deformed porphyroclasts of
446 plagioclase (1.5-3.5 mm) also occur sporadically. The occurrence of quartz and feldspar
18 ACCEPTED MANUSCRIPT 447 ribbons still indicates straining at high temperatures, but points to a stronger deformation
448 followed by important static recrystallization (Passchier and Trouw, 2005).
449 No reliable kinematic indicators were observed in thin section, as well as in the field,
450 neither in the Farsund shear zone, nor in the Hidra mylonitic zone. The scarcity of
451 assymetrical markers and incompletely transposed elements is especially worth noting. Such a
452 feature is typical of shear zones developed under high-grade conditions and can be largely
453 attributed to a high recrystallization degree (Passchier et al., 1990; Passchier and Trouw,
454 2005).
455
456 6. AMS study
457
458 6.1. AMS scalar parameters
459
460 The bulk magnetic susceptibility, Km = (K1 + KMANUSCRIPT2 + K3)/3, ranges in the whole data set from 461 9.3 to 172.9 x 10-3 SI (Table 1), with an average of 32.8 ± 21.9 x 10-3 SI. Such high values
462 (>>10-3 SI) indicate that the magnetic mineralogy is dominated by ferromagnetic minerals
463 (Rochette et al., 1992; Bouchez, 2000), namely titanomagnetite which is ubiquitous in the
464 studied samples and has a ferrimagnetic behaviour given its low Ti content (e.g. Clark, 1997).
465 The dominant contribution of low-Ti titanomagnetite to the bulk magnetic susceptibility has
466 been established, through various techniques, in other AMC and HBG magnetite-bearing 467 rocks from the areaACCEPTED (Bolle et al., 2000; Bolle et al., 2003b). 468 Histograms of Km show two distinct, only slightly overlapping populations in the Farsund
469 intrusion (Fig. 5a): (1) the Opx facies, with similar average Km values for the Opx + Hbl sub-
470 facies (24.2 ± 3.9 x 10-3 SI) and the Hbl + Opx sub-facies (26.4 ± 10.5 x 10-3 SI), and (2) the
-3 471 Hbl + Bt facies, with a much higher average Km value of 75.0 ± 42.3 x 10 SI. The
19 ACCEPTED MANUSCRIPT
472 overlapping of Km values is defined mostly by some samples of the Hbl + Opx sub-facies
473 belonging to the HBG suite, that have a higher magnetite content than their AMC
474 counterparts (sites 40, 62, 65; Table 1). It is also worth noting that the highest Km values
475 (>100 x 10-3 SI) are found in titanite-bearing, fine-grained rocks, that have very high
476 magnetite contents (sites 66b, 81, 87; Table 1). The Km values for the Lyngdal granodiorite
477 are similar to those of the coarse-grained representatives of the Hbl + Bt facies (Fig. 5a; Table
478 1), with an average of 62.3 ± 11.3 x 10-3 SI. It can be concluded here that there is a good
479 correlation between Km and the petrographic type (magnetite content), and, also, that Km is a
480 useful discriminant between the low-fO2 AMC and high-fO2 HBG suites, at least at the pluton
481 scale. Accordingly, contouring of Km in the sampled area (Fig. 5b) reveals areas of maximum
482 values (>40 x 10-3 SI) corresponding to the HBG zones of the Farsund intrusion and to the
483 Lyngdal granodiorite.
484 Interestingly, the contoured map of Km fits the aeromagnetic anomaly map of the area 485 (references in Olesen et al., 2004), where the Lyngdal MANUSCRIPT granodiorite and the western (main) 486 HBG zone of the Farsund intrusion are outlined by strong positive anomalies, whereas the rest
487 of the Farsund intrusion (mostly AMC rocks) is occupied by lower positive anomalies. The
488 positive aeromagnetic anomalies over the Farsund intrusion and the Lyngdal granodiorite are
489 thus induced anomalies, whose intensity varies according to the magnetite content of the
490 rocks. Such a conclusion complies with the results of McEnroe et al. (2001) which have
491 shown that, in the RAP, rocks rich in multi-domain magnetite are related to positive magnetic 492 anomalies inducedACCEPTED by the present Earth’s field, whereas rocks rich in hemo-ilmenite cause 493 negative anomalies related to magnetic remanence acquired during a time of reversed
494 magnetic polarity.
495 The anisotropy degree and shape of the magnetic fabric are expressed here using the Pj
496 and Tj parameters of Jelinek (1981), respectively:
20 ACCEPTED MANUSCRIPT
497 P exp 2 ln K K 2 (i = 1 to 3) and T 2lnK lnK lnK lnK lnK , j i m j 2 1 3 1 3 i
498 where Pj expresses the departure from an undeformed, spherical AMS ellipsoid (Pj = 1), and 499 Tj indicates a prolate (neutral, oblate) ellipsoid for -1 ≤ Tj < 0 (Tj = 0, 0 < Tj ≤ 1).
500 The Pj values are in the interval 1.10–2.08 (Table 1), with an average of 1.33 ± 0.15, which
501 means that moderately anisotropic magnetic fabrics dominate the data set. In a Pj vs. Km
502 diagram, the Lyngdal granodiorite defines a trend characterized by an increase of Pj with
503 increasing Km (Fig. 6a), a relationship that is common in magnetite-bearing granitoids and can
504 be attributed, at least partly, to interactions between ferromagnetic grains (Bouchez, 2000).
505 Such a positive correlation between Pj and Km is a bit more roughly defined for the Hbl + Bt
506 facies and is not obviously displayed for the Opx facies (Fig. 6a). For the latter facies,
507 samples coming from the Hidra mylonitic zone and from areas of strain localization in the
508 Farsund shear zone are shifted towards high Pj values in the Pj vs. Km diagram (Fig. 6a). The 509 Pj parameter is thus also related, at least locally,MANUSCRIPT to the amount of strain undergone by the 510 rocks. The competiting effects of the magnetic susceptibility (magnetite content) and
511 deformation rate on the anisotropy degree is well illustrated on a contoured map of Pj (Fig.
512 6c): areas of maximum values (>1.4) are observed in the Lyngdal granodiorite and in the
513 western (main) HBG zone of the Farsund intrusion, and also in the Farsund shear zone and in
514 the Hidra mylonitic zone, with peak values (>1.8) in the strongly-strained, northern tongue-
515 like end of the pluton.
516 The Tj parameter varies from -0.94 to 0.68 (Table 1), with an average of -0.39 ± 0.37,
517 indicating that theACCEPTED magnetic fabric is dominantly prolate. A Tj vs. Pj diagram (Fig. 6b) and
518 comparison of a contoured map of Tj (Fig. 6d) with Fig. 5b indicate that the shape of the
519 magnetic fabric is not related to its anisotropy degree, nor to the bulk magnetic susceptibility
520 (magnetic content). Actually, this parameter simply relates essentially to the shape of the
521 magnetite grains. Indeed, since magnetite dominates the magnetic susceptibility, the magnetic
21 ACCEPTED MANUSCRIPT 522 fabric is mainly related to the subfabric of this oxide, which means that the AMS primarily
523 results from the SPO of the ferrimagnetic grains (Archanjo et al., 1995; Grégoire et al., 1998;
524 Launeau and Cruden, 1998). The contouring of Tj (Fig. 6d) further shows that strongly prolate
525 magnetic fabrics (Tj > 0.5; strongly elongated magnetite grains) are mainly concentrated in
526 the core of the Farsund intrusion and that oblate magnetic fabrics (Tj > 0; flattened magnetite
527 grains) are mostly found in the vicinity of the Hidra leuconorite and in the Lyngdal
528 granodiorite, at some distance of the Farsund intrusion.
529
530 6.2. AMS directional data
531
532 The pattern of the magnetic foliations (planes perpendicular to the K3 axes) in the Farsund
533 intrusion (Fig. 7) mimics that of the field foliations (Fig. 2) and, consequently, the average
534 orientations of the magnetic and field foliations are very similar (N138E/87SW for the former 535 and N146E/89NE for the latter; equal-area projections MANUSCRIPT in Figs. 2, 7a). Slight to moderate 536 obliquenesses are, however, locally observed in the central part of the pluton (Figs. 2, 7), but
537 are probably not significant since the magnetic fabrics in the area are strongly prolate
538 (foliations less defined than the lineations and, hence, more difficult to measure accurately;
539 Fig. 6d). The AMS data further reveals that the foliations wrap around the huge gneiss body
540 in the SE central part of the pluton. Such a deflection of the foliations is indicative of a more
541 rigid behaviour of the gneiss body during deformation of the surrounding rocks. In the 542 Lyngdal granodiorite,ACCEPTED the orientations of the magnetic and field foliations are also similar 543 (Figs. 2, 7). In particular, the AMS data confirm the dominantly NW-SE strikes of the
544 foliations near the contact with the Farsund intrusion (concordance with the foliation pattern
545 in the latter pluton, on the regional scale) and the E-W trend of the foliation pattern further
546 east (Fig. 7).
22 ACCEPTED MANUSCRIPT
547 The magnetic lineations (K1 axes) in the Farsund intrusion are mostly moderately to
548 steeply plunging towards the SE (Fig. 8) and their average orientation (N143E/67SE) is
549 similar to that of the best-fit -axis (N151E/75SSE) determined for the partial girdle defined
550 by the magnetic foliation poles (equal-area projections in Figs. 7a, 8a), which confirms
551 (cylindrical) folding of the pluton. Detailed inspection of Fig. 8 shows that the orientation of
552 the magnetic lineations in the Farsund shear zone complies with that of the field lineations
553 (Fig. 2): magnetic lineations are dominantly trending parallel to the NE margin, with gentle to
554 moderate plunges (≤ ca. 50°) towards the SE or SSE. It also emerges from Fig. 8 that the
555 magnetic lineations in the Farsund intrusion and the Lyngdal granodiorite, together with
556 mineral lineations locally measured in both plutons and in the gneisses near the intrusive
557 contacts define a single pattern characterized by: (1) a general steepening, from moderate
558 (locally gentle) to steep (up to locally 85°) plunges, towards the southern border of the
559 Farsund intrusion and (2) rotations, as seen in map view, in such a way that the lineation 560 trajectories converge towards an area located at MANUSCRIPT the SE end of the Farsund intrusion. The 561 orientation of this pattern is modified in the Hidra mylonitic zone and close to it (Fig. 8).
562 There, the lineations are dominantly steeply plunging towards W to NW or, in the northern
563 tongue-like end of the Farsund intrusion and in the neighbouring high-grade gneisses, N to
564 NE.
565
566 7. Magnetic fabric vs. petrofabric 567 ACCEPTED 568 The AMS scalar parameters provide some semi-quantitative informations on the studied
569 rocks: Km correlates with the magnetite content (AMC vs. HBG signature) and Pj is locally
570 related to the strength of the petrofabric. The concordance of the magnetic foliations and
571 lineations with the field foliations and lineations further indicates that the magnetic fabrics
23 ACCEPTED MANUSCRIPT 572 can be used as proxies for the petrofabrics and may help in revealing their significance. For
573 instance, combination of the AMS directional data with the field and microscope structural
574 observations show that the petrofabrics in the Farsund intrusion are no more purely magmatic:
575 the widespread occurrence of microstructures attributed to mostly high-T, solid-state
576 deformation, the continuity of the structures across the pluton and their concordance with
577 those measured in the surrounding rocks (especially the continuity of the lineations across the
578 pluton margins; Fig. 8b) demonstrate that a sub-solidus straining was superimposed onto the
579 magmatic fabric, in continuity with the magmatic deformation. In the Farsund shear zone and
580 in the Hidra mylonitic zone, sub-solidus straining and recrystallization are obviously
581 extensive, whereas elsewhere in the pluton, the moderate imprint of the solid-state
582 deformation, as revealed by the microstructural analysis, and the foliation deflection that is
583 locally observed along the contact with the Lyngdal granodiorite (Figs. 2, 7) indicate that the
584 rock texture is still partly inherited from the magmatic state. 585 Coaxiality between the magnetic fabrics, controlled MANUSCRIPT by the SPO of minor magnetite grains 586 and the rock shape fabrics, dominated by the SPO of silicates can now be justified, in the light
587 of the magmatic- to solid-strain history established for the Farsund intrusion. The main
588 reasons for such a correspondance are that: (1) magnetite, a liquidus mineral that started
589 crystallizing early in the sequence of crystallization (Dupont, 2004), aligned preferentially
590 parallel to the other crystals in the magma (as demonstrated through image analysis in other
591 magnetite-bearing granitoids; Archanjo et al., 1995; Launeau and Cruden, 1998) and (2) such 592 a mimetic orientationACCEPTED has not been modified by sub-solidus straining and recrystallization, 593 since both processes were operating in the continuity of the magmatic deformation. Coaxiality
594 between magnetic fabrics and petrofabrics also requires magnetite grains being dominantly
595 multi-domain (intrinsic maximum and minimum AMS axes parallel to the largest and shortest
596 grain dimensions, respectively), which is the case here given magnetite grain size is usually
24 ACCEPTED MANUSCRIPT 597 >20 m (rough boundary between multi- and pseudo-single-domain magnetic behaviours in
598 magnetite; Clark, 1997). Fine-grained secondary magnetite, as revealed by the petrographic
599 analysis, is in trace amount and its influence on the magnetic fabrics is therefore negligible.
600
601 8. Structural control on the emplacement of the Farsund intrusion
602
603 The lineations in the steeply-dipping Farsund shear zone are predominantly gently to
604 moderately-plunging (Figs. 2, 8), pointing to a strike-slip component of shearing. Indeed, one
605 can safely consider that the magnetic and mineral lineations approximate the axis of
606 maximum finite stretching, and it can also be assumed that they are relatively close to a solid-
607 state flow (shear) direction, at least in the most strained rocks such as those of the Farsund
608 shear zone. In absence of any reliable sense-of-shear marker, both the sense of strike-slip
609 shearing (dextral or sinistral) and the dip-slip component of shearing (normal or inverse) 610 cannot be determined. One can only assume a MANUSCRIPT normal component, given the extensional 611 tectonic regime that prevailed at the time of emplacement of the Farsund intrusion, i.e. during
612 the Dalane phase of Bingen et al. (2008b) characterized regionally by the exhumation of the
613 Rogaland–Vest-Agder sector as a large-scale gneiss dome (Bingen et al., 2006). If this
614 interpretation holds true, the Farsund shear zone would be a transtension structure.
615 In the northern tongue-like end of the Farsund intrusion and close to it, in the high-grade
616 gneisses, the lineations are steeply-plunging (Figs. 2, 8), pointing to a different kinematics for 617 the northern portionACCEPTED of the Farsund shear zone. As tackled above, rocks from the tongue-like 618 end are extremely strained (very well-developed quartz and feldspar ribbons, extremely strong
619 SPO and Pj values >1.8), as a consequence of the mylonitization along the eastern margin of
620 the Hidra leuconorite, that was locally superimposed on strained rocks from the Farsund shear
621 zone. The development of the Hidra mylonitic zone, that we ascribe to the emplacement of
25 ACCEPTED MANUSCRIPT 622 the Hidra leuconorite, is also responsible for the local steepening of the lineations and
623 probably erased the likely strike-slip component recorded further south in the Farsund shear
624 zone.
625 Actually, the structural pattern along the NE margin of the Farsund intrusion is quite
626 similar to that observed at the eastern border of the RAP (Fig. 9a): (1) N-S– to NW-SE–
627 striking, steeply-dipping foliations occur in a roughly linear, several-km-large zone that
628 straddles the eastern margin of the RAP (Krause and Pedall, 1980; Falkum, 1982; Bolle et al.,
629 1997, 2000; Marker et al., 2003) and (2) along that margin, a strong SPO with narrow
630 corridors of strain localization is developed (Rietmeijer, 1979; Bolle et al., 1997, 2000) in
631 felsic rocks from the BKSK (quartz mangerites and charnockites forming the cap of the
632 layered intrusion; Fig. 1b; Duchesne and Wilmart, 1997) and in the so-called Apophysis of
633 the BKSK (a sheet-like igneous body, coeval with the BKSK felsic rocks, made of various
634 intermingled felsic to jotunitic rocks and that is sandwiched between the Åna-Sira anorthosite 635 and the high-grade gneisses; Fig. 1b; Bolle and Duchesne,MANUSCRIPT 2007). Hence, there is a steeply- 636 dipping shear zone that straddles the eastern border of the RAP, similar to the Farsund shear
637 zone which runs along the NE margin of the Farsund intrusion. The Farsund shear zone can
638 be viewed as a branch of this larger structure that will be here referred to as the RAP shear
639 zone (Fig. 9a). Mineral and magnetic lineations in the RAP shear zone and close to it are
640 dominantly steeply-plunging (Demaiffe, 1977; Bolle et al., 1997, 2000; Vander Auwera et al.,
641 2006), as it is the case at the northern end of the Farsund shear zone. The usually steep nature 642 of the lineations,ACCEPTED as well as local variations in the orientation and thickness of the zone with 643 steeply-dipping foliations in the gneisses (Fig. 9a), suggest that the emplacement of the RAP
644 and the coeval to subsequent gravity tectonism (Duchesne et al., 1985; Paludan et al., 1994;
645 Barnichon et al., 1999; Bolle et al., 2000, 2002) have restructured the RAP shear zone,
26 ACCEPTED MANUSCRIPT 646 erasing, in particular, any evidence of the likely strike-slip component that is recorded in the
647 Farsund shear zone (this point will be discussed with more details in the next section).
648 The Farsund and RAP shear zones represent two branches of a major structure that had
649 not been reported so far. However, the occurrence of a large-scale discontinuity to the east of
650 the RAP has been envisaged by Duchesne et al. (1999) who stated that a lithospheric-scale
651 weakness zone would be responsible for a large Moho offset identified to the south of the
652 Farsund intrusion, on an offshore deep seismic profile (Andersson et al., 1996). Duchesne et
653 al. (1999) proposed that the N-S-elongated Feda gneiss (Fig. 9a) could materialize that
654 weakness zone, in the same way as the Mandal gneiss, another N-S–striking representative of
655 the Feda suite, seals the southward prolongation of the Mandal–Ustaoset Line (Fig. 1b). The
656 linear aspect of the N-S–trending unit and the common occurrence of N-S–striking, gently-
657 plunging lineations inside it (Falkum, 1998) agree with the idea of the Feda gneiss
658 materializing a major (strike-slip) structure (Duchesne et al., 1999). However, the gentle to 659 moderate dips of the foliations and the folding of MANUSCRIPT the southern tip of the gneiss body (Fig. 2) 660 cannot be explained straightforward with this model. Hence, if the Feda gneiss is really
661 elongated along a lithospheric-scale weakness zone, the latter was probably no longer active
662 during the Dalane phase, contrary to the Farsund and RAP shear zones.
663 The close spatial association of the Farsund intrusion, as well as the RAP, with a major
664 shear zone is certainly not accidental. Actually, the collocation of igneous bodies, especially
665 granitic plutons, with large-scale shear zones and faults is common, and it is now widely 666 admitted that theseACCEPTED major structural weaknesses may control the upward transfer and 667 emplacement of magmas in the crust (e.g. Hutton, 1988; D’Lemos et al., 1992; Archanjo et
668 al., 1994; Ferré et al., 1997; Brown and Solar, 1998; Liégeois et al., 2003; Čečys and Benn,
669 2007; Joly et al., 2007; Henry et al., 2009). Such a model of tectonically-controlled
670 magmatism applies to the Sveconorwegian post-collisional plutons: models of genesis, ascent
27 ACCEPTED MANUSCRIPT 671 and emplacement controlled by large-scale discontinuities were proposed for the Flå–
672 Iddefjord–Bohus granitic belt (emplacement along the neighbouring terrane boundary; Fig.
673 1a; Andersson et al., 1996; Eliasson et al., 2003), for plutons of the western granitic belt
674 (emplacement along the Mandal–Ustaoset Line; Fig. 1a; Vander Auwera et al., 2003) and for
675 the RAP (emplacement along the lithospheric-scale weakness zone detected through deep
676 seismic data; see above; Duchesne et al., 1999). We propose that the structural weakness
677 materialized by the RAP and Farsund shear zones would have controlled not only the ascent
678 and emplacement of the RAP magmas, but also that of the Farsund intrusion which extends
679 the RAP towards the SE.
680
681 9. Evidence of gravity tectonism
682
683 The two events of gravity tectonism evidenced in the RAP, i.e. the diapiric emplacement 684 of the Egersund-Ogna, Åna-Sira and Håland-Helleren MANUSCRIPT anorthosites (Duchesne et al., 1985; 685 Barnichon et al., 1999), and the gravity-driven subsidence of the BKSK (Paludan et al., 1994;
686 Bolle et al., 2000, 2002) relay each other in time, although being partly coeval. Indeed, the
687 BKSK was emplaced and crystallized on top of the anorthosites (Wilson et al., 1996) and,
688 following Bolle et al. (2002), its downward transfer was made through the sinking, into the
689 surrounding low-density anorthosites and granulitic gneisses, of the high-density mafic floor
690 of the layered intrusion (a cumulate series of noritic average composition, locally more than 691 7-km-thick, lyingACCEPTED under the felsic rocks; Fig. 1b). Such a sinking was made possible through 692 very high temperatures related to the multi-emplacement of the RAP and consequent crustal
693 softening, and is indissociable from late upward transfer of the anorthosites.
694 We attribute the steepening of the lineations in the RAP shear zone to the latest gravity-
695 induced vertical movements, i.e. the subsidence of the BKSK and the relative upward flow of
28 ACCEPTED MANUSCRIPT 696 the neighbouring anorthosites and granulitic gneisses. Hence, the RAP shear zone would have
697 localized late, gravity-induced “readjustments” between bodies of contrasted densities
698 (BKSK, anorthosites and granulitic gneisses). Intrusions such as the Hidra and Garsaknatt
699 leuconorites, as well as the Apophysis (Fig. 9a) were emplaced late in the tectonomagmatic
700 history of the RAP (Demaiffe, 1977; Bolle and Duchesne, 2007), probably concurrently with
701 the late gravity-induced movements. Therefore, the roles played, in the genesis of the Hidra
702 mylonitic zone and the associated steepening of the lineations, by the emplacement of the
703 Hidra leuconorite and the late gravity-induced movements cannot be distinguished from each
704 other.
705 The convergent aspect of the lineation trajectories towards an area where the lineations
706 are very steeply-plunging, as observed in the SE part of the Farsund intrusion (Fig. 8b), is
707 related to a syn- to post-emplacement vertical stretching which became localized at the triple
708 junction between the Farsund intrusion, the Lyngdal granodiorite and the antiform or dome 709 that affects the southern banded gneisses, and that MANUSCRIPT we interpret as being also gravity-induced. 710 This vertical stretching is associated with the folding of the Farsund intrusion along a steeply-
711 plunging axis (sub-parallel to the average magnetic lineation; Figs. 7a and 8a), which in turn
712 is probably coeval with the folding or doming of the southern banded gneisses. The fold
713 geometry, especially the steeply-plunging axis, and the regional tectonic context prevailing at
714 ca. 930 Ma (Bingen et al., 2008b) preclude that the folding could result from syn-orogenic
715 horizontal shortening, contrary to most folds evidenced in the high-grade gneiss complex 716 (Falkum, 1998).ACCEPTED Actually, the folding records the last generation of folds that affected the 717 gneisses and whose representatives located close to the RAP are thought to be coeval with the
718 multi-emplacement of the anorthosite province (Falkum, 1998). Based on the striking
719 similarity between the observed lineation pattern and that typical of subsiding troughs, as the
720 one evidenced in the BKSK (Fig. 9b), we propose that the folding of the Farsund intrusion
29 ACCEPTED MANUSCRIPT 721 and the associated vertical stretching reflect gravity-induced vertical movements that occurred
722 in the hot environment developed near the RAP and its offshore extension (gravity and
723 aeromagnetic anomalies indicate that the Sveconorwegian post-collisional plutons, including
724 the RAP, extend offshore towards 80 km away from the coast; Fig. 1a; Andersson et al.,
725 1996; Olesen et al., 2004). Interestingly, a 20-30-km-large offshore negative gravity anomaly,
726 coupled to a negative magnetic anomaly, appears on geophysical maps immediately to the
727 south of the Farsund intrusion (Olesen et al., 2004) suggesting the occurrence in that area of a
728 large offshore anorthosite body. It cannot be excluded that the stretching localized in the SE
729 portion of the Farsund intrusion could correspond to a return (downward) flow (Barnichon et
730 al., 1999) developed during (late?) upward transfer of this anorthosite.
731 In summary, it is proposed that gravity-driven movements were localized along the
732 eastern border of the RAP, as well as at the SE end of the Farsund intrusion. These vertical
733 movements developed in a very hot environment linked to the multi-emplacement of the RAP 734 and its offshore extension, which is also responsible MANUSCRIPT for the M2 metamorphic event. The very 735 high thermal conditions in and around the RAP, locally enhanced by the emplacement of the
736 Farsund intrusion, and the related vertical movements might have lasted for a quite long
737 period of time (several million years), as suggested by thermal modeling of the anorthosite
738 emplacement (Westphal et al., 2003). This probably explains why gravity tectonism would
739 have erased, in the RAP shear zone, any evidence of the likely strike-slip (possibly
740 transtensional) tectonism evidenced in the Farsund shear zone. 741 The gravity ACCEPTEDtectonism that was active at and after ca. 930 Ma in the RAP and, as 742 suggested here, in its close surroundings is akin to that prevailing in the Archean orogenic
743 crust and, more generally, in the Precambrian ultra-hot orogens (Chardon et al., 2009). In the
744 latter case, however, vertical movements were occurring at a much broader scale due to
30 ACCEPTED MANUSCRIPT 745 regional high heat flow and could have been triggered, at least in some cases, by horizontal
746 shortening.
747
748 10. NW-SE– to E-W– versus N-S–trending structures
749
750 The structural database presented here needs to be improved by additional investigations,
751 in particular to materialize the southern and northern extension of the Farsund and RAP shear
752 zones, respectively. However, on the basis of the available structural data, some light can be
753 shed on the geodynamical significance of the structural trend evidenced in the Farsund
754 intrusion and its surroundings.
755 The Farsund and RAP shear zones represent a major discontinuity (the Farsund-RAP
756 shear zone), belonging to the N-S to NW-SE–trending shear-zone network that cuts across the
757 Sveconorwegian orogen (Fig. 1a) and which could represent a transpressional structure 758 reactivated in the extensional (possibly transtensional MANUSCRIPT as suggested here) tectonic regime that 759 characterizes the Dalane phase of Bingen et al. (2008b). The Farsund-RAP shear zone could
760 also materializes the limit of two distinct major lithotectonic units, as it is roughly coincident
761 with the boundary between the outcrop areas of the AMC and HBG suites whose evolutions
762 were controlled by two contrasted crustal contaminants (Bolle et al., 2003a; Vander Auwera
763 et al., subm.). In turn, this suggests that the shear zone could be inherited from a pre-
764 Sveconorwegian, Mesoproterozoic or Paleoproterozoic structure generated during the birth of 765 the continental crustACCEPTED in the area (as old as 1.85 Ga, based on Nd model ages of high-grade 766 gneisses; Menuge, 1988). The NW-SE strike of the structure, contrasting with the N-S trend
767 of the Rogaland–Vest-Agder gneiss complex (Fig. 1b) and, at a larger scale, with that of the
768 southern portions of Sveconorwegian shear-zones (Fig. 1a) points, moreover, to interference
769 with the N-S–trending Sveconorwegian structures during reactivation. Alternatively, the NW-
31 ACCEPTED MANUSCRIPT 770 SE strike might equally indicate that the Farsund-RAP shear zone would have formed during
771 the Dalane phase and could be equivalent to a transfer or accomodation zone (also called
772 "fault-domain boundary"; Schlische and Withjack, 2009), oblique to the main structural
773 domains. This second hypothesis dismisses, however, a model considering the Farsund-RAP
774 shear zone as a limit between two different pre-Sveconorwegian domains.
775 The E-W strike which characterizes the main body of the Lyngdal granodiorite (Fig. 1b)
776 and most steeply-dipping foliations found inside it (Figs. 2, 7) represents an even greater
777 anomaly in the predominantly N-S–trending structural pattern of the Rogaland–Vest-Agder
778 sector. It is tempting to link this E-W trend to emplacement along a discontinuity that would
779 be a satellite of the Sorgenfrei–Tornquist Zone, an E-W- to NW-SE–trending, large (20-45
780 km) and complex –mostly offshore– fracture zone cutting across the Precambrian basement
781 and the Phanerozoic cover of the southwesternmost corner of Fennoscandia (Fig. 1a;
782 Berthelsen, 1998; see also the review of Pharaoh, 1999). This intraplate major structure was 783 mostly active during Late Palaeozoic and Mesozoic MANUSCRIPT times, in the course of which successive 784 tectonic phases gave rise to faults with normal and/or strike-slip component, and grabens
785 (Pegrum, 1984; Liboriussen et al., 1987; Mogensen, 1994). However, it has been argued that
786 the Sorgenfrei–Tornquist Zone might have a much longer and more complex history, as it is
787 often the case for lithospheric-scale structures, and already existed since Proterozoic time.
788 Indeed, the Sorgenfrei–Tornquist Zone is believed to belong to a set of Precambrian
789 lineaments cutting across the Fennoscandian basement (references in Pegrum, 1984). The 790 elongation of offshoreACCEPTED Sveconorwegian intrusive bodies along the Sorgenfrei–Tornquist Zone 791 also implies that location of the fracture zone has been governed by structuring of the
792 Proterozoic basement (Fig. 1a; Olesen et al., 2004).
793
794 11. Conclusions
32 ACCEPTED MANUSCRIPT 795
796 As shown elsewhere, the Farsund intrusion was constructed by coeval magmas belonging
797 to the AMC and HBG suites, the two Sveconorwegian post-collisional magmatic suites of A-
798 type affinity identified in Southern Norway. The bulk magnetic susceptibility, in the Farsund
799 intrusion and the neighbouring Lyngdal granodiorite, correlates with the rock magnetite
800 content and, hence, discriminates between the low-fO2 (magnetite-poor) AMC and high-fO2
801 (magnetite-rich) HBG rocks. Combination of the AMS data with the field and microscope
802 structural observations further suggests that two structural events were active during and after
803 emplacement of the Farsund intrusion.
804 First, the Farsund intrusion is elongated parallel to the here defined Farsund shear zone, a
805 steeply-dipping structure that straddles the NE border of the pluton. This shear zone exhibits a
806 likely strike-slip component of shearing and possibly corresponds to a transtension structure.
807 It branches from the Rogaland anorthosite province (RAP) shear zone, a similarly steeply- 808 dipping structure that straddles the eastern margin MANUSCRIPT of the RAP. The Farsund-RAP shear zone 809 represents a newly discovered large-scale zone of weakness, roughly coincident with the
810 boundary between the outcrop domains of the AMC and HBG suites. It was active at the time
811 of emplacement of the Farsund intrusion and the RAP, i.e. during the gravitational foundering
812 of the Sveconorwegian orogen (the so-called Dalane phase). This major NW-SE–striking
813 shear zone, oblique to the N-S–trending Sveconorwegian terrane boundaries, is either a new
814 structure (oblique "fault-domain boundary"?) formed during the Dalane phase or, more 815 probably, an inheritedACCEPTED transpressional structure reactivated during this phase. In the latter 816 case, it could be an interference between N-S–trending Sveconorwegian structures and
817 discontinuities inherited from the crust generation in the area during the Mesoproterozoic or
818 the Paleoproterozoic. In both cases, it is proposed that the Farsund-RAP shear zone would
819 have controlled the ascent and emplacement of the Farsund intrusion and the RAP.
33 ACCEPTED MANUSCRIPT 820 The RAP shear zone probably evolved as a zone of localization of gravity-induced
821 deformation linked to vertical readjustements between bodies of contrasted densities
822 (anorthosites, BKSK, granulitic gneisses). The Farsund intrusion has also recorded a syn- to
823 post-emplacement vertical stretching that became localized to the SE of the pluton and which
824 was possibly also gravity-induced. All these gravity-driven movements developed in a very
825 hot environment, similar to that prevailing in the Precambrian ultra-hot orogens, but having
826 here a local origin, the heat being supplied by the emplacement of anorthosites and coeval
827 igneous bodies, including the Farsund intrusion.
828
829 Acknowledgements
830
831 Technical assistance was received from J.P. Cullus. Field work was partly funded by the
832 F.N.R.S. (National Fund for Scientific Research, Belgium). Helpful suggestions by B. 833 Bingen, and constructive comments by K. Benn MANUSCRIPT and an anonymous reviewer were greatly 834 appreciated.
835
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45 ACCEPTED MANUSCRIPT 1110 Vander Auwera, J., Weis, D., Duchesne, J.C., 2006. Marginal mafic intrusions as indicators
1111 of downslope draining of dense residuals melts in anorthositic diapirs? Lithos 89, 329-352.
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1121 Bjerkreim-Sokndal layered intrusion, Southwest Norway. In: Cawthorn, R.G. (Ed.),
1122 Layered intrusions. Elsevier, Amsterdam, pp. 231-255. 1123 Zhou, X.Q., Bingen, B., Demaiffe, D., Liégeois, J.P.,MANUSCRIPT Hertogen, J., Weis, D., Michot, J., 1995. 1124 The 1160 Ma Hidderskog meta-charnockite: implication of this A-type pluton for the
1125 Sveconorwegian belt in Vest-Agder (SW Norway). Lithos 36, 51-66.
1126
ACCEPTED
46 ACCEPTED MANUSCRIPT 1127 Figure captions
1128
1129 Fig. 1. (a) Sketch map of the western portion of the Sveconorwegian orogen (simplified from
1130 Bingen et al., 2005; offshore data after Andersson et al., 1996; Pharaoh, 1999; Olesen et al.,
1131 2004; inset map of Fennoscandia modified after Bogdanova et al., 2008); RVA, Rogaland–
1132 Vest-Agder sector; MUL, Mandal-Ustaoset Line; Fl, Id and Bo are Flå, Iddefjorden and
1133 Bohus granites. (b) Geological map of the Rogaland–Vest-Agder sector (after Sigmond et al.,
1134 1984; Mandal-Ustaoset Line and isograds from Falkum, 1982; Tobi et al., 1985; Bingen et
1135 al., 1996; boundaries for the Rogaland anorthosite province and the Farsund intrusion from
1136 references listed in the caption of Fig. 2). Pig-, Osm-, Opx- and Cpx-in are pigeonite-,
1137 osumilite-, orthopyroxene- and clinopyroxene-in isograds; Fe and Ma, Feda and Mandal
1138 gneisses; EGOG, Hå, He and ÅS are Egersund-Ogna, Håland, Helleren and Åna-Sira
1139 anorthosites; BKSK and Ap, Bjerkreim-Sokndal layered intrusion and its Apophysis; Hi and 1140 Ga, Hidra and Garsaknatt leuconorites; Ly1 and MANUSCRIPT Ly2, main body and northern limb of the 1141 Lyngdal granodiorite; Ho, Holum monzogranite. Ages quoted in the legend were compiled
1142 from available U-(Th)-Pb geochronological data (see text for references).
1143
1144 Fig. 2. Geological and structural map of the Farsund intrusion and its surroundings. Modified
1145 after Falkum et al. (1979), Krause and Pedall (1980), Falkum (1982, 1998) and Marker et al.
1146 (2003). Most structural measurements in the Farsund pluton and close to its margins are from 1147 this study. A contouredACCEPTED equal-area projection (lower hemisphere; contours at 1-2-4-6-8-10 %) 1148 shows the distribution of the foliation poles in the Farsund intrusion. “Igneous” fabric, as
1149 opposed to gneissic fabric, refers to the fabric observed in the igneous bodies, irrespective of
1150 the degree of solid-stated deformation superimposed on the magmatic fabric. The concordant
1151 gneisses have steeply-dipping foliations and, based on locally available measurements,
47 ACCEPTED MANUSCRIPT 1152 gently- to moderately- or steeply-plunging mineral lineations that are parallel to the structures
1153 measured in neighbouring strongly-foliated rocks from the Farsund intrusion and the
1154 Rogaland anorthosite province. The axial plane traces of large-scale folds in the gneisses, as
1155 shown to the north of the Farsund intrusion, belong to the F2 to F5 folding phases of Falkum
1156 (1998). The limit of the area labelled “Quaternary moraines” corresponds to an approximate
1157 boundary of a coastal plain covering the bedrock.
1158
1159 Fig. 3. Distribution map of the lithofacies, constructed from combined microscope and field
1160 observations. AMS sampling sites are located. Other samples are from Dupont (2004), and
1161 Vander Auwera and Bolle (work in progress). An approximate boundary between AMC and
1162 HBG zones is drawn in the Farsund intrusion. This boundary is primary a limit between Opx
1163 and Hbl + Bt samples; some Hbl + Opx samples were integrated in the HBG zones, on the
1164 basis of chemical analyses conducted at or close to the sampling site. 1165 MANUSCRIPT 1166 Fig. 4. Photomicrographs (transmitted light, crossed nicols) illustrating microscope-scale
1167 evidence of ductile deformation in the Farsund intrusion and the Lyngdal granodiorite. (a)
1168 chessboard pattern in a quartz grain, defined by square-shaped subgrains (Opx + Hbl sub-
1169 facies, site 54; Table 1); (b) quartz grain with elongated subgrains, fringed with aggregates of
1170 small quartz grains probably developed by dynamic recrystallization, in a sample from the
1171 Lyngdal granodiorite collected at ca. 600 m from the contact with the Farsund intrusion (site 1172 41; Table 1); (c)ACCEPTED plagioclase grain with curved polysynthetic twins (Opx + Hbl sub-facies, site 1173 89; Table 1); (d) slight kinking of a primary orthopyroxene grain (Opx + Hbl sub-facies, site
1174 48; Table 1); (e) irregular quartz (above) vs. microperthitic orthoclase (below) grain boundary
1175 (Opx + Hbl sub-facies, site 49; Table 1); (f) quartz ribbons and dynamically recrystallized
1176 matrix in a sample from the Hidra mylonitic zone (Opx + Hbl sub-facies, site 27; Table 1).
48 ACCEPTED MANUSCRIPT 1177
1178 Fig. 5. (a) Partial histograms of the bulk magnetic susceptibility (Km); (b) Contoured map of
1179 Km. See remark in Table 1.
1180
1181 Fig. 6. (a) Plot of Jelinek’s (1981) AMS anisotropy degree (Pj) vs. bulk magnetic
1182 susceptibility (Km) (strongly-strained rocks come from the Hidra mylonitic zone and from
1183 areas of strain localization in the Farsund shear zone); (b) Jelinek’s (1981) plot of AMS shape
1184 (Tj) vs. anisotropy degree (Pj); (c) Contoured map of Pj; (d) Contoured map of Tj. See remark
1185 in Table 1.
1186
1187 Fig. 7. (a) Map of the magnetic foliations, with contoured equal-area projections of the
1188 foliation poles (lower hemispheres; contours at 1-2-4-6-8-10 % for the Farsund intrusion and
1189 1-6-12 % for the Lyngdal granodiorite). Gneissic foliations and some “igneous” foliations 1190 from Fig. 2 are also shown. (b) Contoured map ofMANUSCRIPT the magnetic foliation dips, with foliation 1191 trajectories. Gneissic and “igneous” foliations from Fig. 2 were combined with the magnetic
1192 foliations to draw the trajectories. In the high-grade gneisses to the NE of the Farsund
1193 intrusion, only the trajectories of the concordant, steeply-dipping foliations, as found close to
1194 the pluton margin, are drawn (for more structural details in the area, see Fig. 2). Subvertical
1195 foliation has dip ≥ ca. 80°. See also the remark in Table 1.
1196 1197 Fig. 8. (a) MapACCEPTED of the magnetic lineations, with contoured equal-area projections (lower 1198 hemispheres; contours at 1-3-6-9-12 % for the Farsund intrusion and 1-8-16 % for the
1199 Lyngdal granodiorite). Most mineral lineations from Fig. 2 are also shown. (b) Contoured
1200 map of the magnetic lineation plunges, with lineation trajectories. Mineral lineations from
49 ACCEPTED MANUSCRIPT 1201 Fig. 2 were combined with the magnetic lineations to draw the trajectories. See also the
1202 remark in Table 1.
1203
1204 Fig. 9. (a) Schematic structural map of the Rogaland anorthosite province (RAP), Farsund
1205 intrusion and adjacent areas, highlighting foliation trajectories. Simplified from references
1206 quoted in the caption of Fig. 2, Rietmeijer (1979), Paludan et al. (1994), Jorde et al. (1995),
1207 Bolle et al. (2000) and Fig. 7b. Foliation trajectories are drawn from foliation and igneous
1208 layering in the anorthosite-leuconorite bodies, igneous modal layering in the cumulates of the
1209 Bjerkreim-Sokndal layered intrusion (BKSK), and “igneous” and magnetic foliations in the
1210 Farsund intrusion and the Lyngdal granodiorite (see Fig. 7), as well as in the BKSK felsic
1211 rocks and the Apophysis. In the BKSK, the planar fabric in the felsic rocks is concordant to a
1212 penetrative foliation (S1) overprinting the original layering (S0) in the cumulates; this S1
1213 foliation is usually parallel to S0 in the limbs of the lobes formed by the folded cumulates and, 1214 hence, it is not drawn in these areas. The concordant MANUSCRIPT steeply-dipping gneisses correspond to 1215 the belts of concordant gneisses defined on Fig. 2 and to their northern extension. (b)
1216 Comparison of the lineation pattern found in the present study (right) with that evidenced in
1217 the BKSK (left; drawn from magnetic lineations and, in the cumulates, mineral lineations,
1218 after Paludan et al., 1994 and Bolle et al., 2000). The Central Zone in the BKSK felsic rocks
1219 is an area where the lineation plunges are universally very steep (average orientation of
1220 N62E/87NE). ACCEPTED
50 Figure 1 ACCEPTED MANUSCRIPT
6°E 7°E Baltic Shield 59°N b Stavanger ROGALAND- VEST-AGDER SECTOR FENNOSCANDIA Fe
Opx-in Osm-in
5°E SVECONORWEGIAN 9°E 11°E Pgt-in Cpx-in OROGEN (W PART) a Fl EGOG BKSK Fe Ma
60°N Oslo MUL Egersund Ga
Hå He Sweden Norway Id ÅS Rogaland 59°N Flekkefjord Ma anorthosite Ap Bo RVA province Hi Fe Farsund Ly2 intrusionMANUSCRIPT ~ Skagerrak ~ Ho 58°N Ly1 Farsund see Fig. 9a Ma see Fig. 2 10 km Mandal 58°N ~ North Sea ~ Denmark 50 km ~ Kattegat ~ Caledonian nappe Denmark cover (Mesozoic-Caenozoic) Opx granitoid & Oslo graben (Upper Palaeozoic) 0.93-0.92 Ga Layered series (norite average composition) Sorgenfrei-Tornquist Zone AMC suite Anorthosite - leuconorite Caledonian nappe Opx & Hbl+Bt granitoid (ca. 0.93 Ga AMC & HBG suite) Post-collisional pluton (0.99-0.92 Ga) Hbl+Bt granitoid (0.96-0.95 Ga HBG suite) id. (offshore extension) Augen granitic gneiss (1.19-1.05 Ga) Syn-collisional Feda suite (1.05 Ga) Faintly-foliated (locally augen) granitic gneiss Metamorphic complex (undifferentiated) ACCEPTED Banded gneiss - minor metasediment - 1.55-1.03 Ga
orogen Terrane limit (major shear zone) minor amphibolite & pyroxene-rich gneiss
1.14-0.90 Ga Other shear zone and fault Isograd Sveconorwegian Approximate northern boundary of Fault belonging to the Mandal-Ustaoset Line the Rogaland-Vest-Agder sector
Fig. 1 - Bolle et al. Figure 2
6°35’E ACCEPTED MANUSCRIPT6°45’E 6°55’E 60 35 85 80
30 55 80 55 50 45 76 54 40 25 70 35 70 Flekkefjord 45 60 72 74 30 70 78 10 85 73 84 55 76 74 50 82 30 10 40 65 55 70 65 88 81 25 80 45 40 40 75 78 75 85 85 60 82 58° 86 15’N 82 86 40 55 35 45 65 75 45 70 30 88 25 75 85 87 40 65 43 40 85 75 75 32 25 20 82 88 60 40 84 80 70 70 86 35 60 87 55 83 50 80 80 Farsund shear zone62 85 70 84 69
82 35 55 70 Hidra 82 mylonitic zone 26 74 80 80 63 55 77 80 53 44 60 80 68 75 85 80 55 70 85 68 60 80 70 52 75 FARSUND 85 80 48 85 80 84 87 73 INTRUSION 83
85 60
80 80 80 85 80 83 75 80 85 80 80 73 83 85 83 70 80 80 80 80 85 80 80 85 82 84 80 82 ? 80 75 85 75 60 45 65 70 85 60 (Quaternary moraines) 45 65 MANUSCRIPT50 80 85 68 80 Not exposed 58 87 60 48 84 85 50 64 88 80 45 45 80 85 26 45 60 58 Farsund 73 82 84 60 75 80 70 65 33 35 70 80 78 50 72 58° 70 05’N 22 65 40 67 80 31 25 55 30 80 40 38 53 5 km 45 75
Farsund intrusion "Igneous" fabric Gneissic fabric Åna-Sira anorthosite Foliation Lineation Foliation Lineation N & Hidra leuconorite 1° - 29° 0° BKSK Apophysis 30° - 59° 1° - 29° 60° - 89° 30° - 59° Lyngdal granodiorite 60° - 89° 60° - 89° ACCEPTED(only strike) Various granitoids 90° 90° Feda augen gneiss 236/01 Granitic gneiss Trace of axial plane in the gneiss complex
Banded gneiss Antiform Overturned antiform Strongly-foliated rock Farsund intrusion & concordant gneiss Synform Overturned synform (n = 76) Major fault
Fig. 2 - Bolle et al. Figure 3
ACCEPTED MANUSCRIPT
AMS Other Samples Opx + Hbl Hbl + Opx (+ Bt locally) Hbl + Bt Hbl + Bt (Lyngdal granodiorite) Fine-grained facies dominating Probable AMC/HBG suite boundary
SAMPLING SITES & LITHOLOGY
N
1 km
MANUSCRIPT ?
ACCEPTEDFig. 3 - Bolle et al. Figure 4 Click here to download high resolution image ACCEPTED MANUSCRIPT
MANUSCRIPT
ACCEPTED Figure 5
ACCEPTED MANUSCRIPT
55 a b 50 -3 Km (10 SI) > 80 45 60-80 40 40-60 20-40 35 Farsund intrusion 0-20 Opx + Hbl 30 Hbl + Opx (+ Bt locally) Hbl + Bt N 25 AMS sites Number of 1 km 20
15 ? 10
5
0 0 20 40 60 80 100 120 140 160 180 -3 Km (10 SI) 10 MANUSCRIPT Lyngdal 5 granodiorite BULK MAGNETIC (Hbl + Bt) SUSCEPTIBILITY AMS sites Number of 0 0 20 40 60 80 100 120 140 160 180 -3 Km (10 SI)
Fig. 5 - Bolle et al. ACCEPTED Figure 6
ACCEPTED MANUSCRIPT
2.2 a c
2.0 Pj Strongly- strained rocks > 1.8 1.6-1.8 1.8 1.4-1.6 1.2-1.4 Pj 1.6 1-1.2
1.4 N
1.2 1 km
1.0 0 20 40 60 80 100 120 140 160 180 ? -3 Km (10 SI) 1.0 b
Oblate 0.5 magnetic fabric
d Tj 0.0 Tj 0.5 / 1 0 / 0.5 Prolate -0.5 / 0 -0.5 magnetic fabric -1 / -0.5 MANUSCRIPT -1.0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 N
Pj 1 km
Opx + Hbl Hbl + Opx (+ Bt locally) Hbl + Bt ? Hbl + Bt (Lyngdal granodiorite)
ANISOTROPY & SHAPE OF THE MAGNETIC FABRIC ACCEPTED
Fig. 6 - Bolle et al. Figure 7 ACCEPTED MANUSCRIPT
80 FOLIATIONS a b 83
71 Magnetic "Igneous" Gneissic 81 82 1° - 29°
87 30° - 59° 77 84 87 60° - 89° 78 78 81 80 90° 84 77 83 88 77 88 86 85 65 89 67 N 77 69 72 87 88 76 89 88 68 N 87 67 62 85 79 ? 84 81 84 57 77 85 76 77 83 70 1 km 85 60 79 63 84 85 209/03 63 85 84 86 73 Lyngdal granodiorite 71 79 84 68 74 63 80 67 (n = 13) 68 81 71 77 75 87 77 73 73 MANUSCRIPT 78 78 78 77 82 49 84 80 77 79 85 85 79 85 87 77 82 85 86 87 89 88 77 88 76 66 ? 77 82 83 76 77 89 77 79 Dip of magnetic foliation 79 N 71 79 57 89 60°-90° 61 76 48/03 66 80 79 30°-60°
66 Foliation trajectory with dip attitude 75
57 41 Trajectory of subvertical foliation
Farsund intrusion (n = 112) ACCEPTED
Fig. 7 - Bolle et al. Figure 8 ACCEPTED MANUSCRIPT
73 LINEATIONS a b 82
70 81 Magnetic Mineral
47 1° - 29°
41 76 30° - 59° 72 37 81 60° - 89° 78 54 28 34 68 68 29 54 41 49 28 31
27 31 N 33 40 32 25 46 54 N 50 35 285/75 64 44 32 ? 43 45 45 42 55 61 54 56 53 46 1 km 59 58 56 79 56 58 61 59 60 65 59 Lyngdal granodiorite 71 57 76 65 62 68 63 66 66 (n = 13) 73 67 67 77 70 64 MANUSCRIPT 67 73 72 58 69 73 76 69 77 49 77 82 76 80 77 85 61 79 70 79 77 77 83 79 85 76 76 67 73 67 63 62 65 ? 75 82 65 68 77 81 Plunge of magnetic lineation 76 75 79 59 N 61 19 60°-90° 57 76 66 72 67 30°-60°
58 0°-30° 68
143/67 49 Lineation trajectory with plunge attitude
41
Farsund intrusion (n = 112) ACCEPTED
Fig. 8 - Bolle et al. Figure 9
ACCEPTED MANUSCRIPT
6°00'E 6°20'E 6°40'E a
Feda gneiss 58° 30'N
R A P s h e a
r
z
o
58° n 20'N 10 km e
Feda Caledonian nappe gneiss
Strongly-foliated felsic Farsund shear zone to intermediate rock Undifferentiated
suites Foliation trajectory with dip attitude 58° 10'N Layering trajectory with dip attitude AMC & HBG in the BKSK cumulates
Concordant steeply-dipping gneiss ? Not exposed Undifferentiated
gneiss Trajectory of gneissic foliation High-grade Major fault MANUSCRIPT b Lineation plunge 60°-90° 30°-60° 0°-30° Lineation trajectory with plunge attitude
? Limit of the Central Zone (BKSK)
ACCEPTED
Fig. 9 - Bolle et al. Table 1
ACCEPTED MANUSCRIPT
Table 1. AMS data
Site n X Y Type Km Pj Tj K1 K3 Site n X Y Type Km Pj Tj K1 K3
Dec Inc Dec Inc Dec Inc Dec Inc
1 4 58325 54700 Opx + Hbl (c) 29.4 1.61 0.06 329 68 93 13 62 4 59360 53972 Hbl + Opx (c) 46.8 1.10 0.14 292 41 46 25 2 4 59046 55637 Opx + Hbl (c) 24.9 1.45 0.09 323 78 82 6 63 4 60279 54250 Opx + Hbl (c) 20.3 1.14 -0.05 123 49 215 2 3 4 59186 56116 Opx + Hbl (c) 19.7 1.32 0.19 259 81 79 9 64 4 59757 54897 Opx + Hbl (c) 23.9 1.20 0.65 146 54 239 2 4 4 59173 56812 Opx + Hbl (c) 25.3 1.40 0.02 278 76 79 13 65 4 59571 47494 Hbl + Opx (c) 43.7 1.13 -0.39 181 65 81 4 5 4 59745 56978 Opx + Hbl (c) 27.5 1.23 0.19 166 72 58 6 66a 4 59836 48496 Hbl + Ttn (c) 60.9 1.07 0.68 208 63 70 21 6 4 60085 56390 Opx + Hbl (c) 22.5 1.28 0.33 164 54 57 12 b 4 Hbl + Bt + Ttn (f) 156.4 1.37 -0.17 129 79 246 5 7 4 60358 55951 Opx + Hbl (c) 26.0 1.21 0.17 164 34 67 10 8 (average) 118.8 1.32 -0.16 132 79 246 5 8 4 59951 55553 Opx + Hbl (c) 22.5 1.26 0.49 151 68 28 13 67 4 60482 49559 Opx + Hbl (c) 29.5 1.17 -0.72 146 54 245 6 9 4 66941 51244 Opx + Hbl (c) 22.7 1.51 -0.52 148 46 56 2 68 6 61934 48103 Hbl (c) 40.4 1.21 -0.89 148 60 57 0 10 4 67022 49925 Hbl + Opx (c) 19.5 1.34 -0.79 137 45 42 5 69 6 61424 46887 Hbl + Opx (f) 30.0 1.26 -0.42 131 63 299 27 11 4 65835 50435 Opx + Hbl (c) 21.5 1.32 -0.66 151 32 42 28 70 6 60677 47360 Hbl + Opx (f) 36.2 1.25 -0.47 155 62 279 17 12 4 64714 50539 Opx + Hbl (c) 22.4 1.42 -0.56 144 44 30 23 71 4 65055 44692 Opx + Hbl (c) 19.2 1.26 -0.38 121 79 16 3 13 4 63232 50846 Opx + Hbl (c) 24.1 1.37 -0.53 153 35 47 22 72 4 64282 44767 Opx + Hbl (c) 24.6 1.34 -0.24 137 85 1 4 14 4 62517 49402 Hbl (c) 78.8 1.21 -0.73 179 53 81 6 73 2 66510 44281 Hbl + Bt (f) 45.2 1.26 -0.09 117 63 23 2 15 4 62130 50219 Hbl + Opx (c) 48.4 1.17 -0.36 162 43 254 3 74 4 65830 43653 Opx + Hbl (c) 24.4 1.36 -0.45 60 75 209 13 16 4 61118 50453 Hbl (c) 69.6 1.24 -0.71 150 64 243 2 75 4 64786 49343 Hbl + Opx (c) 32.0 1.29 -0.61 138 56 40 5 17 4 60270 50905 Opx + Hbl (c) 24.7 1.21 -0.68 146 50 55 1 76 4 66040 49173 Opx + Hbl (c) 19.2 1.33 -0.80 150 46 45 14 18a 6 61352 48841 Hbl (f) 37.5 1.28 -0.87 154 60 264 11 77 4 66286 48158 Hbl + Opx (c) 15.7 1.34 -0.73 151 61 52 5 b 2 Hbl (c) 51.9 1.15 -0.30 139 53 257 19 78 4 66391 46949 Hbl + Bt (c) 39.6 1.28 -0.40 136 66 289 22 8 (average) 41.6 1.23 -0.72 149 59 261 13 79 4 65826 46495 Hbl + Opx (c) 19.7 1.15 -0.75 109 77 245 10 19 4 71048 48771 Opx + Hbl (c) 24.4 1.28 -0.71 162 58 61 7 80 4 65095 48395 Hbl + Opx (c) 32.8 1.32 -0.73 159 58 50 11 20 4 69719 48625 Opx + Hbl (c) 18.7 1.39 -0.65 170 56 48 20 81 4 64486 47824 Hbl + Bt + Ttn (f) 172.9 1.57 -0.41 151 59 5 27 21 4 67670 46339 Hbl + Opx (c) 17.5 1.28 -0.83 157 58 273 15 82 4 65316 47466 Hbl + Opx (c) 18.9 1.24 -0.58 143 57 240 5 22 4 68596 47100 Hbl + Opx (c) 25.6 1.30 -0.59 174 66 44 16 83 4 62959 46650 Opx + Hbl (c) 23.9 1.21 -0.75 133 67 324 22 23 4 69600 47500 Hbl + Opx (c) 9.3 1.24 -0.72 176 76 61 6 84 4 63524 47151 Opx + Hbl (c) 21.6 1.17 -0.73 134 68 14 11 24 4 61845 57428 Opx + Hbl (c) 23.5 1.34 0.21 136 41 43 3 85 4 62569 47315 Opx + Hbl (c) 27.4 1.27 -0.59 145 71 315 19 25 4 61075 58082 Opx + Hbl (c) 30.8 1.27 0.24 132 47 230 8 86 4 63235 48007 Opx + Hbl (c) 20.7 1.28 -0.93 137 65 241 6 26 4 59242 60301 Hbl + Opx (c) 37.0 1.87 0.19 46 82 250 7 87 4 63879 48628 Bt + Ttn + Hbl (f) 102.2 1.61 -0.92 153 56 3 30 27 4 59566 59362 Opx + Hbl (c) 31.7 2.08 0.00 52 70 250 19 88 4 63845 49645 Opx + Hbl (c) 20.7 1.32 -0.62 146 55 44 9 28 4 60260 58548 Opx + Hbl (c) 26.4 1.37 0.08 51 81 241 9 89 4 62999 44783 Opx + Hbl (c) 25.2 1.25 -0.49 133 79 16 5 29 4 58625 61224 Hbl + Opx (c) 37.6 1.75 -0.08 350 73 227 10 90 4 64963 45888 Hbl + Opx (c) 22.3 1.18 -0.43 135 77 321 13 30 4 64482 46766 Hbl + Opx (c) 18.4 1.20 -0.70 116 73 225 6 91 4 66224 51642 Opx + Hbl (c) 24.6 1.44 -0.58 129 25 37 3 31 4 63875 46025 Opx + Hbl (c) 24.8 1.19 -0.59 214 69 337 12 92 4 65684 52024 Opx + Hbl (f) 21.0 1.42 -0.63 140 40 31 21 32 4 63563 45295 Opx + Hbl (c) 21.9 1.15 -0.38 126 80 7 5 93 4 64933 51781 Opx + Hbl (c) 19.2 1.40 -0.75 136 32 34 18 33 4 62625 45964 Opx + Hbl (c) 19.2 1.17 -0.73 133 76 338 12 94 4 64297 52414 Opx + Hbl (c) 22.8 1.43 -0.56 144 33 46 13 34 4 61911 46272 Opx + Hbl (c) 21.5 1.20 -0.70 148 72 318 17 95 4 65108 52728 Hbl + Bt + Opx (c) 31.8 1.55 -0.81 134 27 225 1 35 4 61267 44678 Opx + Hbl (c) 22.8 1.28 -0.61 187 73 303 8 96 4 66151 52924 Hbl + Bt (c) 41.1 1.25 -0.33 153 31 48 23 36 4 61345 45505 Opx + Hbl (c) 24.8 1.22 -0.80 107 76 305 13 97MANUSCRIPT 4 68842 48297 Opx + Hbl (c) 21.6 1.29 -0.82 166 59 19 27 37 4 60715 45019 Opx + Hbl (c) 35.0 1.24 -0.62 174 83 310 5 98 4 69789 49389 Opx + Hbl (c) 26.7 1.42 -0.53 149 61 35 13 38 3 60248 46536 Opx + Hbl (c) 23.0 1.12 -0.41 144 67 268 13 99 4 69121 49935 Opx + Hbl (c) 21.3 1.40 -0.58 134 45 32 11 39 4 59928 45980 Opx + Hbl (c) 26.9 1.20 -0.52 140 77 302 12 100 3 68482 49600 Opx + Hbl (c) 18.6 1.39 -0.91 132 42 7 33 40a 6 58782 46644 Hbl + Opx (c) 55.8 1.10 0.47 151 68 318 21 101 4 68526 50920 Hbl + Opx (c) 21.2 1.47 -0.27 151 54 41 14 b 4 Hbl + Opx (f) 33.2 1.25 0.05 149 69 309 20 102 4 68611 44435 Hbl + Opx (c) 21.6 1.27 -0.60 111 76 213 3 c 4 Hbl + Opx (MME) 34.5 1.36 -0.16 133 74 301 16 103 4 68352 45242 Hbl + Opx + Bt (c) 18.5 1.24 -0.84 142 70 263 11 14 (average) 44.6 1.16 0.11 143 70 312 19 104 4 68527 46161 Hbl + Opx (c) 17.8 1.24 -0.71 171 69 270 3 41 4 73461 42125 Hbl + Bt + Ttn (L) 60.2 1.65 -0.11 317 19 214 33 105 6 69559 46454 Opx + Hbl (c) 16.3 1.22 -0.22 164 64 54 9 42 4 72065 41895 Opx + Hbl (c) 21.9 1.32 -0.25 347 76 177 14 106 4 69433 45217 Hbl + Opx + Bt (c) 17.3 1.26 -0.55 111 77 230 6 43 4 71183 41556 Opx + Hbl (c) 31.4 1.47 -0.61 4 66 172 24 107 4 70929 43633 Hbl + Opx (c) 35.8 1.13 0.26 318 65 51 1 44 4 68956 41820 Opx + Hbl (c) 19.8 1.28 -0.18 46 57 195 29 108 4 63952 44650 Hbl + Opx (c) 12.5 1.19 -0.82 151 67 244 1 45 4 67993 43157 Opx + Hbl (c) 25.7 1.35 -0.35 77 76 217 11 109 4 71346 39476 Hbl + Bt (L) 49.5 1.46 -0.01 38 49 260 33 46 4 68737 43548 Opx + Hbl (c) 27.5 1.31 -0.94 101 77 267 13 110 4 70798 38751 Hbl + Bt (L) 66.5 1.48 -0.49 32 41 215 49 47 4 69521 42711 Opx + Hbl (c) 31.9 1.31 -0.60 64 79 233 11 111 4 71204 45321 Opx + Hbl (c) 22.1 1.29 -0.16 233 85 59 5 48 4 67363 43419 Opx + Hbl (c) 23.1 1.28 -0.49 88 68 216 14 112 4 70513 45667 Hbl + Opx (c) 15.4 1.25 -0.33 222 82 51 8 49 4 67422 44302 Opx + Hbl (c) 24.5 1.24 -0.59 119 67 353 14 113 4 70605 46674 Opx + Hbl (c) 21.0 1.26 0.09 214 67 37 23 50 4 67470 44925 Hbl + Opx (c) 34.5 1.29 -0.56 129 79 304 11 114 4 71618 46042 Hbl + Opx (c) 20.6 1.35 -0.34 208 73 38 17 51 4 66869 43373 Opx + Hbl (c) 23.1 1.33 -0.64 43 82 208 7 115 4 71892 43949 Opx + Hbl (c) 31.6 1.38 -0.47 191 81 40 8 52 4 68062 42688 Opx + Hbl (c) 17.6 1.25 -0.72 72 61 200 19 116 4 72773 45452 Hbl + Bt (L) 66.8 1.64 -0.88 181 61 73 10 53 4 69615 43963 Opx + Hbl (c) 27.2 1.19 -0.58 95 62 242 24 117 4 72162 46078 Hbl + Bt (L) 68.4 1.69 -0.10 223 73 86 13 54 4 70385 44343 Opx + Hbl (c) 32.4 1.36 -0.53 147 76 48 2 118 4 73661 45828 Hbl + Bt + Ttn (L) 49.0 1.50 0.13 221 49 37 41 55 4 71198 44488 Hbl + Opx (c) 22.3 1.28 -0.44 230 77 44 13 119 4 74838 41948 Hbl + Bt + Ttn (L) 87.4 1.72 0.12 261 72 26 10 56 4 72299 44817 Hbl + Opx (c) 19.3 1.42 -0.55 224 77 46 13 120 4 75296 43079 Hbl + Bt + Ttn (L) 62.9 1.48 0.27 250 75 27 11 57 4 62800 56800 Opx + Hbl (c) 27.8 1.48 0.29 137 37 44 3 121 4 76868 43681 Hbl + Bt + Ttn (L) 70.4 1.51 0.68 251 65 11 13 58 4 62930 55945 Opx + Hbl (c) 23.6 1.30 -0.53 124 28 221 12 122 4 77476 42533 Hbl + Bt + Ttn (L) 52.2 1.33 0.54 285 59 17 1 59 4 63609 55300 Opx + Hbl (c) 32.0 1.24 -0.12 127 29 34 7 123 4 75934 42029 Hbl + Bt + Ttn (L) 75.1 1.45 0.04 252 67 10 11 60 4 62987 54441 Opx + Hbl (c) 22.4 1.27 -0.40 139 28 47 4 124 4 73680 40376 Hbl + Bt + Ttn (L) 48.7 1.36 -0.14 343 58 207 24 61 2 62397 54003 Opx + Hbl (c) 22.9 1.20 -0.52 136 31 43 5 125 4 75085 39992 Hbl + Bt + Ttn (L) 52.3 1.35 -0.22 335 68 202 15
ACCEPTED n: number of specimens; X and Y: coordinates (in m), in the WGS84 UTM grid (32V zone – LK (03E/64N) 100 km square); Km: -3 magnitude of the bulk magnetic susceptibility (in 10 SI); Pj and Tj: Jelinek’s (1981) anisotropy degree and shape parameter; K1 and K3: long and short principal axes of the AMS ellipsoid (magnetic lineation and pole to the magnetic foliation, respectively); Dec and Inc: declination and inclination of the axes; Opx: orthopyroxene; Hbl: hornblende; Bt: biotite; Ttn: titanite; (c): coarse-grained facies; (f): fine-grained facies; (MME): mafic microgranular enclave; (L): Lyngdal granodiorite. Intermingled facies with contrasted grain sizes have been sampled at AMS sites 18, 40 and 66. For each of these three sites, the average values of the AMS parameters (Km, Pj, Tj, K1 Dec and Inc, K3 Dec and Inc), as measured in the various facies, are considered in Figs 4-7. Such an averaging does not give any anomaly in the maps of Figs 4a, 5c-d, 6 and 7.