S G Bergh

L Haaland

L Arbaret

M Forien

.80-1.75 Ga granite suites in the West Troms Basement Complex, northern Norway: Palaeoproterozoic magma emplacement during advancing accretionary orogeny, from field observations

Keywords:

The Ersfjord Granite is part of a suite of c.1.80-1.75 Ga syeno-granites in the West Troms Basement Complex, northern Norway, presumed to belong to the Transscandinavian Igneous Belt (TIB-1) in the Fennoscandian Shield. Previous data suggest the granite formed post-collisional and ascended as a batholite pluton from a source of sub-continental mantle and/or mafic-intermediate lower crust. We argue that the Ersfjord Granite was emplaced initially (c. 1.80 Ga) as multiple tabular sills in a back-arc extensional setting, then as successive melt injections (c. 1.78-1.75 Ga) in an evolving Andean/Cordilleran type accretionary orogen at the waning stages of the Svecofennian orogen. Field observations indicate melt ascent initiated as successive sills (EG-I) into wellfoliated Meso/Neoarchaean TTG gneisses. Some sills preserved a magmatic layering, others injected and assimilated the host rock gneisses leaving pendants of mafic gneiss/migmatite residuum in between the granite sills. The first tectonic patches of melts (EG-II) ascended into the middle/upper crust along regional shear zones and injected into ductile imbricate thrust stacks (D1 event) during NE-SW directed crustal shortening and medium grade P-T conditions, using the sills and ancestor migmatite pendants as melt pathways. Then the tabular EG-I and II granite sheets and adjacent gneisses were coaxially folded by upright macro-folds (D2 event) and steep, granitic pegmatite dyke swarms (EG-III) intruded parallel to the fold axial surface and in related D2 thrusts, at low grade metamorphic conditions. The final melt emplacement (D3 event) included granite pegmatite dykes and sills (EG-IV) along subvertical D3 fold limbs and steep strike-slip shear zones. Our provisional backarc and successive accretionary orogenic emplacement model for the Ersfjord Granite may explain ascent of many other TIB-1 magmas in the Fennoscandian Shield. Keywords 1.80-1.75 Ga TIB-1 related granites, sill intrusions, syn-tectonic thrust emplacement (D1), axial-planar dykes (D2), transpressive dykes (D3), back-arc extension, advancing accretionary orogen.

Introduction

Granites are widespread in the middle and upper continental crust from throughout the geological record, both as intrusive batholites, tabular sheets/sills, and discordant dykes in the host rocks [START_REF] Vigneresse | Crustal regime of deformation and ascent of granitic magma[END_REF]. One major site where juvenile continental crust grows and thickens is along convergent plate margins in advancing accretionary orogens associated with arc subduction (e.g., [START_REF] Condie | Accretionary orogens in space and time[END_REF][START_REF] Cawood | Accretionary orogens through Earth history[END_REF]. Such orogens form when the overriding plate advances towards the downgoing plate causing repeated amalgamation of crustal fragments like magmatic arcs, rift/oceanic basins, volcano-sedimentary wedges, high-and low-pressure metamorphic rocks, and juvenile granitoid magmas, requiring strong mechanical coupling, localized strain in shear zones, and thermal rejuvenation [START_REF] Cawood | Accretionary orogens through Earth history[END_REF]. Most petrological studies indicate that the primary source of granitoid melts in such orogens is from melting of mafic upper mantle rocks in magmatic arcs and/or back-arcs, and residual para-and ortho-gneisses and granulite/migmatites of the lower continental crust, and most likely melting occurred in a syn-to post-orogenic setting (Brown and Solar, 1998a;[START_REF] Sawyer | When the continental crust melts[END_REF]. The processes however, by which continental margin crust is enriched in juvenile felsic magmas, i.e., the nature of segregation, extraction, and ascent of melt triggered by accretionary tectonism, are still uncertain [START_REF] Brown | Evolution and Differentiation of the Continental Crust[END_REF][START_REF] Brown | Granite: From genesis to emplacement[END_REF].

The present paper addresses emplacement mechanisms of a major c.1.80-1.75 Ga, TIB-1 related syeno-granitoid magmatic suite in the Meso/Neoarchean to Palaeoproterozoic West Troms Basement Complex (WTBC), northern Norway (Figs. 1, 2;[START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. The WTBC accreted along the northwestern margin of the Fennoscandian Shield during the latest stages of the Svecofennian orogeny [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF], northeast of the high-pressure subduction-related juvenile magmatic arc in the Lofoten-Vesterålen area (Fig. 1; [START_REF] Griffin | Archaean and Proterozoic crustal evolution in Lofoten-Vesterålen, N Norway[END_REF][START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF][START_REF] Corfu | Multistage metamorphic evolution and nature of the amphibolite-granulite facies transition in Lofoten-Vesterålen, Norway, revealed by U-Pb in accessory minerals[END_REF].

Previous workers consider the 1.80-1.75 Ga TIB-1 magmatism in WTBC as post-collisional and caused by lithospheric reworking [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. We resolve how the widespread and repeated pulses of granitic magmas rather intruded as sills and partly assimilated the host rocks first in an area of extension with elevated heat flow, probably a back-arc setting, and then, in succession during convergent (D1-D3) ductile deformation in a small-scale advancing Andean or North American Commenté [LA2]: I prefer «batholith» but sometime batholite is also found in english...as you want Cordillera type accretionary orogen (cf. [START_REF] Cawood | Accretionary orogens through Earth history[END_REF]. We argue based on field observations, for syn-tectonic ascent and emplacement mechanisms of the granites, in a tectonic setting characterized by compressional shear zone strain typical of accretionary orogens (cf. Brown and Solar, 1998a, b;[START_REF] Vernon | Axial-surface leucosomes in anatectic migmatites[END_REF][START_REF] Weinberg | Magma migration, folding, and disaggregation of migmatites in the Karakoram shear zone, Ladakh, NW India[END_REF].

Geological setting and previous work

2. 1 The Fennoscandian Shield

The northern Fennoscandian Shield (Fig. 1) evolved through multiple Archaean orogenic and magmatic events (2.72-2.62 Ga) followed by Palaeoproterozoic rifting (2.5-2.0 Ga), and lastly by complex convergent, arc-accretion and collisional orogenic events at ca. 2.0-1.5 Ga including the Lapland-Kola, Svecofennian, Nordic, and Gothian orogenies [START_REF] Hölttä | Archaean of Greenland and Fennoscandia[END_REF][START_REF] Lahtinen | The Precambrian Bedrock of Finland -Key to the evolution of the Fennoscandian Shield[END_REF][START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF]. These events resulted in crustal growth by amalgamation of an Archaean nuclei in the northeast and widespread Palaeoproterozoic accretionary growth towards the southwest (Kärki et al., 1993;[START_REF] Nironen | The Svecofennian Orogen: a tectonic model[END_REF][START_REF] Åhäll | Long-term convergence along SW Fennoscandia: 330 my. of Proterozoic crustal growth[END_REF].

Archaean crust is present in the northeast of the Fennoscandian Shield overlain by a widespread Paleoproterozoic volcano-sedimentary basin cover formed during a period of major crustal extension at 2.5-2.0 Ga [START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF][START_REF] Bingen | Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, Norway: Tectonic implications in a Fennoscandia context[END_REF][START_REF] Lahtinen | Multiply deformed Paleoproterozoic foreland fold and thrust belt in northern Fennoscandia -The peripheral Kuusamo belt as a key example[END_REF]. At c. 2.10 Ga the Archaean continent broke up and resulted in smaller terranes, e.g., the Karelian and Norrbotten provinces (Fig. 1). In the late Palaeoproterozoic interval most known Precambrian juvenile crust crystallized by arc-related magmatism [START_REF] Daly | The LaplandKola orogen: Palaeoproterozoic collision and accretion of the northern Fennoscandian lithosphere[END_REF][START_REF] Condie | Accretionary orogens in space and time[END_REF][START_REF] Cawood | Accretionary orogens through Earth history[END_REF] during the Lapland-Kola , Svecofennian , and Nordic orogens (Gorbatschev and Bogdanova, 1993;[START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF][START_REF] Lahtinen | Palaeoproterozoic accretionary processes in Fennoscandia[END_REF]. In addition, the Transscandinavian Igneous Belt (1.87 Ga TIB-0 and 1.80-1.75 Ga TIB-1) formed during a major arc-magmatic episode that took place across the entire Fennoscandian shield [START_REF] Larson | A chronological subdivision of the Transscandinavian Igneous Belt-three magmatic episodes?[END_REF][START_REF] Gorbatschev | The Transscandinavian Igneous Belt (TIB) in Sweden: a review of its character and evolution[END_REF][START_REF] Högdahl | The transscandinavian igneous belt (TIB) in Sweden: A review of its character and evolution[END_REF], and was followed by the Gothian orogeny farther south in Scandinavia (Fig. 1; [START_REF] Gaál | An outline of the Precambrian evolution of the Baltic Shield[END_REF][START_REF] Åhäll | Long-term convergence along SW Fennoscandia: 330 my. of Proterozoic crustal growth[END_REF]. The Transscandinavian Igneous belt is trending NNW-SSE and intruded along the southwestern boundary of the Bothnian Basin of the Svecofennian domain, stretching. 2000 km across the entire southern part of Sweden northward to Lofoten-Vesterålen and WTBC areas in northern Norway (Fig. 1;[START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF][START_REF] Högdahl | The transscandinavian igneous belt (TIB) in Sweden: A review of its character and evolution[END_REF].

Similar Archaean-Palaeoproterozoic basement provinces exist northwest of and within tectonic windows of the much younger Caledonian orogen in northern Norway (Fig. 1). There, small volumes of 1.87-1.86 Ga (TIB-0) intrusions exist in the Lofoten and Vesterålen areas (Fig. 1), in addition to much more voluminous phases of TIB-1 related (c.1.80 Ga) granitoid magmas that belong to the anorthosite-mangerite-charnockite-granite (AMCG) plutonic suite [START_REF] Griffin | Archaean and Proterozoic crustal evolution in Lofoten-Vesterålen, N Norway[END_REF][START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF][START_REF] Corfu | Multistage metamorphic evolution and nature of the amphibolite-granulite facies transition in Lofoten-Vesterålen, Norway, revealed by U-Pb in accessory minerals[END_REF]. Similar aged granites with a range of ages between 1.87 Ga,and >1.63 Ga are present on the islands of Senja and Kvaløya in western Troms, including the 1792 ± 5 Ma Ersfjord Granite (Fig. 2; [START_REF] Andresen | The age of the Precambrian basement in western Troms, Norway[END_REF]. The age of the Ersfjord Granite corresponds to the youngest, TIB-1 plutons [START_REF] Högdahl | The transscandinavian igneous belt (TIB) in Sweden: A review of its character and evolution[END_REF]) which formed coeval with late stages of the Svecofennian orogeny.

Other TIB-1 related c. 1.80 Ga monzo-and syenogranites crop out in the Rombak and Tysfjord tectonic windows in the Caledonides south of Lofoten (Fig. 1; [START_REF] Andresen | Age and tectonic setting of the Tysfjord gneiss granite, Efjord, North Norway[END_REF][START_REF] Korneliussen | The geochemistry of Lower Proterozoic mafic to felsic igneous rocks, Rombak Window, North Norway[END_REF][START_REF] Angvik | Geochemical evidence for arc-related setting of Paleoproterozoic (1790 Ga) volcano-sedimentary and plutonic rocks of the Rombak Tectonic Window[END_REF]. Additionally, several granitic suites dated at c.1.80 Ga are present east of the Caledonian nappe front along strike with the WTBC [START_REF] Slagstad | Geology and metallogenic potential of the northwesternmost Norrbotten Province around Altevatn in Troms, northern Norway[END_REF]. These suites merge with A-type monzonitic, modern Andes type intrusive rocks in the Norrbotten province of Sweden (Fig. 1; Bergmann, 2018), formed in a Cordillera type back arc setting by eastward accretion/subduction associated with TIB-1 plutonic rocks farther west (e.g., [START_REF] Bergman | Description of regional geological and geophysical maps of northern Norrbotten County (east of the Caledonian orogen)[END_REF][START_REF] Martinsson | Age and character of late-Svecokarelian monzonitic intrusions in northeastern Norrbotten, northern Sweden[END_REF].

The West Troms Basement Complex

The WTBC is a Meso-/Neoarchaean to Palaeoproterozoic province [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF]) located west of the Scandinavian Caledonides (Fig. 2; [START_REF] Roberts | The Scandinavian Caledonides: event chronology, palaeogeographic settings and likely modern analogues[END_REF][START_REF] Augland | Early Ordovician to Silurian evolution of exotic terranes in the Scandinavian Caledonides of the Ofoten-Troms areaterrane characterization and correlation based on new U-Pb zircon ages and Lu-Hf isotopic data[END_REF] and considered an autochthonous part of the Fennoscandian Shield farther east (Fig. 1;[START_REF] Henkel | Magnetic crustal structures in northern Fennoscandia[END_REF][START_REF] Olesen | Basement structure of the continental margin in the Lofoten-Lopphavet area, northern Norway: constraints from potential field data, on land structural mapping and palaeomagnetic data[END_REF][START_REF] Bergh | Was the Precambrian basement of western Troms and Lofoten-Vesterålen in northern Norway linked to the Lewisian of Scotland? A comparison of crustal components, tectonic evolution and amalgamation history[END_REF][START_REF] Bergh | Archaean elements of the basement outliers west of the Scandinavian Caledonides in Northern Norway: architecture, evolution and possible correlation with Fennoscandia[END_REF][START_REF] Nasuti | New high-resolution aeromagnetic and radiometric surveys in Finnmark and North Troms: linking anomaly patterns to bedrock geology and structure[END_REF]. The WTBC comprises TTG gneisses (2.92-2.6 Ga; [START_REF] Myhre | U-Pb geochronology along an Archaean geotransect in the West Troms Basement Complex, North Norway[END_REF] present in three terranes or litho-tectonic segments; a northeastern segment with juvenile (2.96-2.83 Ga) TTG granitoid rocks in Vanna and Ringvassøya, a southwestern segment of sanukitoid type granitoids (2.71-2.69 Ga) in Senja, and an intervening segment on Kvaløya, with remnants of 2.96 Ga, possible reworked TTGs (Fig. 2; [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. These crustal segments are separated by regional scale ductile shear zones like the Senja shear belt on Senja [START_REF] Zwaan | Geology of the Precambrian West Troms Basement Complex, northern Norway, with special emphasis on the Senja Shear Belt: a preliminary account[END_REF] and the Kvalsund shear zone on Ringvassøya (Fig. 2; [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF]. The host rock TTGs to the Ersfjord Granite on Kvaløya (Fig. 3) belong to the Gråtind Migmatite, Kattfjord Complex, Kvalsund Gneiss, and Bakkejord Diorite aged between 2.96 and 2.61 Ga [START_REF] Zwaan | Database for alle geologiske opplysninger om den prekambriske geologien på Kvaløya, Troms fylke[END_REF][START_REF] Corfu | Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archaean and Palaeoproterozoic events and younger overprints[END_REF][START_REF] Myhre | U-Pb geochronology along an Archaean geotransect in the West Troms Basement Complex, North Norway[END_REF]. Main lithologies are tonalites, tonalitic gneisses, and migmatitic felsic and mafic gneisses [START_REF] Zwaan | Database for alle geologiske opplysninger om den prekambriske geologien på Kvaløya, Troms fylke[END_REF][START_REF] Armitage | Structural development of the Mjelde-Skorelvvatn Zone on Kvaløya, Troms: a metasupracrustal shear belt in the Precambrian West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF].

The Meso/Neoarchaean rocks in WTBC are assembled with several meta-supracrustal rift-related volcano-sedimentary sequences aged at 2.40-1.97 Ga [START_REF] Myhre | Palaeoproterozoic (2.0-1.95 Ga) pre-orogenic supracrustal sequences in the West Troms Basement Complex, North Norway[END_REF], mafic dyke swarms (2.4 and 2.2 Ga; Kullerud et al., 2006;[START_REF] Bergh | Low-grade sedimentary rocks on Vanna, North Norway: a new occurrence of a Palaeoproterozoic (2.4-2.2 Ga) cover succession in northern Fennoscandia[END_REF][START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF], and granitoid and mafic igneous rocks in complex c. 1.80-1.75 Ga fold-thrust belt systems [START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF]. The first juvenile magmatic pulse occurred at 1.87 Ga in Lofoten-Vesterålen (TIB-0) and was followed by 1.80-1.75 Ga TIB-1 related granites and diorites injected during multiple arc-and accretionary tectonomagmatic phases (D1-D3) in the WTBC [START_REF] Andresen | The age of the Precambrian basement in western Troms, Norway[END_REF][START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. Thus, magmatism linked to the Lapland-Kola orogen and/or the early Svecofennian orogenic events (1.92-1.88 Ga) (cf. [START_REF] Daly | The LaplandKola orogen: Palaeoproterozoic collision and accretion of the northern Fennoscandian lithosphere[END_REF][START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF] are totally lacking in WTBC. The reason may be that the WTBC was separated and/or escaped deformation along the active Andes type Fennoscandian margin until TIB-related, 1.87 and 1.80-1.75 granites intruded due to westward progression of the orogenic deformation toward the shield margin [START_REF] Corfu | Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archaean and Palaeoproterozoic events and younger overprints[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF][START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF].

The Ersfjord Granite

The Ersfjord Granite [START_REF] Andresen | The age of the Precambrian basement in western Troms, Norway[END_REF] belongs to the voluminous 1.80-1.75 Ga TIB-1 suite of monzo-/syeno-granite intrusions in the WTBC [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF], on the islands of Kvaløya and Senja (Fig. 2). Previous workers considered these granites to be post-collisional batholitic plutons [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. In their model, the granites were largely undeformed and generated by post-tectonic delamination (e.g., [START_REF] Korja | Seismic and geoelectric evidence for collisional and extensional events in the Fennoscandian shieldimplications for Precambrian crustal evolution[END_REF] of a deep-seated crustal root which formed earlier in the Svecofennian orogeny at c. 1.92-1.85 Ga (Laurent et al., 2019). Similar lithospheric reworking models have been proposed for 1.80-1.75 Ga TIB-1 granitoids [START_REF] Åhäll | Growth-related 1.85-1.55 Ga magmatism in the Baltic shield: a review addressing the tectonic characteristics of Svecofennian, TIB 1-related, and Gothian events[END_REF]Høgdahl et al., 2004;[START_REF] Gray | Geodynamic models of mature continental collision: evolution of an orogen from lithospheric subduction to continental retreat/delamination[END_REF], but these models are not necessarily valid for the WTBC (this work), which account for a younger tectono-magmatic event with larger input of contaminated/ partially melted Archaean-Palaeoproterozoic crust [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF].

The present work shows that the Ersfjord Granite is not a single plutonic batholite, but rather intruded as sills and dykes in several tectonic pulses/events from c. 1.80 to 1.56 Ga, and termed EG-I to EG-V (see Table 1). These Ersfjord granite intrusions are all mostly massive, coarse-/medium-grained and porphyric, but locally also well foliated, with K-feldspar, plagioclase, quartz, primary biotite/ amphibole, epidote/-allanite, occasional muscovite, titanite, epidote, and Fe-Ti oxides/ magnetite, and accessory apatite and zircon [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. Crystallization of the massive EG-I sills is previously dated at 1792 ±5 Ma, with metamorphic overprints at 1769±3 Ma and 1756±3 Ma [START_REF] Andresen | The age of the Precambrian basement in western Troms, Norway[END_REF][START_REF] Corfu | Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archaean and Palaeoproterozoic events and younger overprints[END_REF], whereas similar massive, sill-like granites in Senja yielded ages between 1798 and 1784 Ma [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF], the latter thus marking the termination of the most voluminous of the TIB-1 granites in WTBC. Then, successive granite sills and dykes injected into the WTBC in Kvaløya synchronous with orogenic compression (c. , including W-E thrusting (D1), coaxial macro-folding (D2), orogen-parallel thrusting and lateral (transpressive) shearing (D3), and during post-orogenic reworking at 1.63-1.56 Ga [START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF] (Table 1). In the foreland on Vanna Island, [START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF] applied D1-D2 events, which correspond to D2-D3 in WTBC elsewhere.

Methods and data

Data used in this study (see Table 1) are from recent field and structural analyses by the authors and a master study [START_REF] Haaland | Geometry and kinematic evolution of ductile shear zones in the Ersfjord[END_REF]. Detailed structural analyses were made in Ersfjord Granite sills (EG-I), conformable granite-internal migmatite zones, and related melts in D1 ductile shear zones/thrusts (EG-II), and as melts in the foliation of adjacent TTG gneisses. Fully exposed contacts of the EG-I granite sills with TTGs were studied at Kjølen in the east and Tverrfjellet in the west (Fig. 3). Then we mapped and analyzed relative to host rock deformation, a D2 granite dyke swarm (EG-III) which intruded along axial-planar shear zones of upright D2 macro-folds at Otervika, c.10 km south of the

Commenté [LA3]: Batholith?

Commenté [LA4]: I'm not sure that a master report that cannot be easely found (it is ?) by readers will be accepted as a valid reference....In addition Haaland is co-author; therefore it is not necessary to cite this report... main Ersfjord Granite body, and finally, resolved melt emplacement into subvertical D3 folds and strike-slip shear zones. The structural analysis involved determining the geometry of orogenic structures and kinematic characters of D1-D3 ductile shear zones that formed synchronous with EG-II to IV melt emplacement, and their relation to shortening strain and deformation patterns in the surrounding TTGs.

Results

The Ersfjord Granite in Kvaløya defines two large and several smaller, oblate-to lens-shaped, N-S to NW-SE trending geometric bodies arranged as several hundred granite sheets, or sills (Fig. 4a) parallel with the main foliation of surrounding TTG gneisses and metasupracrustal rocks (Fig. 3). The contacts with the host rocks are intrusive as in sills, except when they are reworked by D1 and D2 ductile thrusts (see below). Internally, these sills (EG-I) vary in thickness from ≤2 to c. 100 m, and typically are separated conformably by narrow mafic migmatite zones and superimposed ductile shear zones.

Numerous smaller, and mineral-texturally similar granite sheets/sills, foliation-parallel lenses, and dyke swarms exist in the adjacent TTGs, e.g., in the Senja shear belt, in Kvalsund Gneiss east of Kaldfjord, in Kattfjord Complex gneisses at Otervika in southwestern Kvaløya, and in the Kvalsund shear zone on Ringvassøya (Figs. 2,3).

Pre-tectonic sills (EG-I) and migmatite zones

The EG-I sills have an internally weak, but rhythmic, pervasive planar fabric composed of alternating coarse-and medium-grained granite with variable amount of aligned biotite and amphibole (Fig. 4bc). This fabric dips gently both NE, NW, and north, but is mostly subparallel to sill contacts and foliation in the surrounding TTG gneisses and superposed D1-ductile shear zones (Fig. 3). The coarseand medium-grained layers contain igneous textures with rectangular-shaped phenocrysts of perthitic feldspar and twinned plagioclase, with sharp grain contacts (Fig. 4d). Locally, aligned plagioclase phenocrysts yield a mineral lineation (Fig. 4e) which is plunging variably but mostly c. W-E. The layered fabric is often truncated and partly reorganized internally by felsic dykes with irregular contacts but similar texture and grain sizes as in the host EG-I sills (Fig. 4e).

Clusters and lenses of slightly aligned amphibolite pods exist as dismembered layers parallel to and inside thick EG-I sills, and the mafic and felsic components in combination, define a pseudo-layering (Fig. 5a-c). Locally, more fine-grained granites are seen as rim clusters around larger mafic pods (Fig. 5d). In addition to the mafic intercalations, extensive and prevalent, conformable mafic migmatite fabrics separate the EG-I sills and their distributed magmatic fabric. Such mafic migmatite zones are visible from a distance as regular depressions in between benches/ledges of the massive EG-I sills (Figs. 4a). The migmatite zones vary in thickness from <1m to 20 meters (Fig. 6a,b) and contain internally, fabric-parallel lenses and wedges of weakly layered EG-I sills with sharp to variously diffuse edges, and locally they are surrounded/cut by smaller, layer-oblique EG-I veins (Fig. 6c,d).

Distinct K-feldspar rich, red-colored granites that are petrographically and texturally similar to most EG-I sills (cf. [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF] are also widely present in the surrounding Meso/Neoarchaean TTG gneisses farther west (Fig. 3) and in the Senja shear belt and Kvalsund shear zone (Fig. 2). In outcrops, such sills display sharp (intrusive) contacts and define rhythmic, massive and/or weakly layered granites in between tonalitic and mafic gneisses, whereas others have irregular and truncating, wedgelike contacts (Fig. 7b-d). Some sills are connected by discordant granite veins/clusters bifurcating into the mafic TTG gneiss foliation (Fig. 7b,c), others have irregular and locally boudinage contacts with the foliation of surrounding TTGs (Fig. 7e).

Syn-tectonic injections (D1-D3)

Granites injected in D1 ductile thrusts (EG-II)

Several generations of tectonic-related Ersfjord granitic melts (Table 1b-d) post-date the EG-I sill intrusions (cf. [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. We observed and defined the oldest tectonic melts (EG-II) as those that injected into migmatite zones in between EG-I sills and became themselves internally tightly folded, thrusted, and sigmoidal sheared (Figs. 8,9,10), thus defining ductile D1 shear zones.

The large-scale architecture of D1 shear zones is expressed as irregular, anastomosing EG-I sills and migmatite zones at Hollendaren (Fig. 3), where internal truncations define lenses, duplexes, and imbricate stack-like structures (Fig. 8a). Despite these irregularities, most D1 shear zones in the Ersfjord Granite overall are conformable with EG-I sills, migmatite zones, and foliation in the surrounding TTGs (Fig. 3). Along the eastern contact between EG-I sills and Kvalsund Gneiss TTGs at Kjølen, sigmoidal-shaped granite (EG-II) define slices in a thrust-related duplex with top-to-the west displacement (Fig. 8b). Similar west directed D1 thrusts are mapped inside the main Ersfjord Granite body at Hatten and Store Blåmann (Fig. 3), comprising isoclinal D1 folds (Fig. 8c) with variably oriented fold axes that spread along an average shear zone girdle with strike mostly perpendicular to the main westerly shearing direction (Fig. 11a). Stretching lineations are few, probably due to static metamorphic overgrowth on foliation surfaces, but reveal similar shear direction (Fig. 11a). The southwestern contact of the Ersfjord Granite with TTGs at Tverrfjellet (Fig. 3) is also a major thrust zone with top-to-the west sense of shear (Fig. 11a). This shear zone is up to 100 m thick and contains repeated, well-foliated granite lenses and aligned mafic pods in migmatite zones mostly conformable with the underlying TTG foliation.

In outcrops, EG-II sills in D1 shear zones are distinguished from EG-I sills in being overprinted by a ductile metamorphic foliation (Fig. 9a,b) which is distinguished from the magmatic fabric by presence of new-grown, syn-kinematic amphibole, flaky biotite, and locally garnet in a recrystallized quartzfeldspar matrix (Fig. 9c-f), suggesting mineral growth during shearing and amphibolite facies metamorphic conditions (see Table 1b). Strong foliation-internal elongation, boudinage, and lateral pinch-out of the EG-II sills and mafic pods can be seen along this foliation (Figs. 9b). The foliation wrapping around mafic pods are cut by both felsic EG-II vein-networks (Fig. 9a), and veins that are transposed and dismembered and often tightly folded by asymmetric, isoclinal and recumbent folds (Fig. 10a,b). Injected EG-II veins are present both along the axial-surfaces and limbs of such internal tight folds (Fig. 10c,d). All these observations of EG-II sills injected into D1 shear zones are summarized in Fig. 10e (see discussion).

Presumed D1 deformed EG-II sills are also widely observed along foliation of the surrounding TTG gneisses. Possible EG-II injections in TTGs include those granite sills that are internally displaced, thickened, transposed, and partly folded into the foliation, and tight to isoclinal folded and repeated granite veins in between thicker granite sills (Fig. 10f).

Granites related to upright D2 macro-folds (EG-III)

A regional scale N-S to NW-SE trending D2 antiform exists between Ersfjord and Kattfjord [START_REF] Armitage | Structural development of the Mjelde-Skorelvvatn Zone on Kvaløya, Troms: a metasupracrustal shear belt in the Precambrian West Troms Basement Complex, North Norway[END_REF] which folded all the TTGs and two metasupracrustal belts, and the Ersfjord Granite itself in Kvaløya (Figs. 3,11b). Other major D2 folds are an antiform at Tverrfjellet (Figs. 3,12), synformal folding of EG-I and -II sills between Hatten and Middagstind (Fig. 3), folds north and east of Kaldfjord, and a synform in the west at Otervika (Fig. 3). Notably illustrative is the D2 antiformal folding of the Tverrfjellet (D1) shear zone (Fig. 12a,b), shown by a change in dip direction on each fold limbs but consistent WSW-directed internal shear sense, thus demonstrating post-D1folding. At small-scale, D2 folds are asymmetric, and west-verging and they cut D1 foliation and EG-II sills at a high angle, and new EG-III sills are injected into these shear zones, and as separate dykes (Fig. 12c).

In the west at Otervika (Fig. 3) the TTGs and enclosed EG-I sills several tens of meters thick are

folded by an open synformal D2 fold and cut by a widespread, axial planar granite pegmatite dyke swarm (EG-III) dipping moderately to the SW (Fig. 13a,b). One such pegmatite dyke which petrographically resembles coarse-grained varieties of EG-I sills, is previously dated at 1774 ± 5 Ma [START_REF] Corfu | Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archaean and Palaeoproterozoic events and younger overprints[END_REF]. In outcrop the EG-III pegmatite dykes vary from planar to irregular, displaying abundant interconnected veins and straight contacts with the adjacent TTGs (Fig. 13b). The dyke contacts are mostly sharp and crosscut the D1 gneiss foliation and EG-I sills at high angle, but we observe injection of EG-III veins into the foliation of the mafic host gneisses as well as indentation of mafic gneiss layers into the EG-III pegmatites.

Similar D2 pegmatite dykes are present in TTGs of the Senja Shear Belt, and as irregular, transposed EG-III injections along several D2 axial-planer ductile thrusts in Kattfjord Complex gneisses north of Kaldfjord (Fig. 13c), adjacent to where the main Ersfjord Granite contact itself is a D2-related thrust (Fig. 3). A major, moderately east-dipping D2 shear zone is mapped at Buren (Figs. 3,4a), which cuts EG-I and -II sills and differs from D1-thrusts in comprising massive EG-III sills transposed and altered to ortho-/ultramylonitic fabrics, but with same top-to-the west thrust sense (Fig. 13d). The mylonites consist of recrystallized, sigmoidal-shaped feldspar and quartz porphyroclasts, often surrounded by a matrix of S-C shaped flaky muscovite and biotite fishes (Fig. 13e). Additional growth of aligned epidote, chlorite, and albite in mafic lenses of the shear zone at Buren addresses lower metamorphic conditions during the D2 event (i.e., greenschist facies) than for the D1 thrusting.

Granites injected in steeply plunging D3 folds and strike-slip zones (EG-IV)

A third group of structures into which Ersfjord granites injected are steeply NNE-to NW-plunging D3 macro-and meso-folds accompanied by subvertical NNE-SSW sinistral and NW-SE dextral strike-slip shear zones. The strike-slip shear zones are centimeter-to meter-thick, typically mylonitic, and oriented parallel to limbs and axial surfaces of steeply plunging D3 folds (Fig. 14a-c). Shear-sense estimates appear from drag-folding and ductile offset of D2 dykes (Fig. 14c,d), and by local subhorizontal stretching lineations. Macro-scale D3 folds reveal the same geometry and are inferred from refolding of D2 macro-folds at Tverrfjellet and east of Kaldfjord (Fig. 11b).

The D3 shear zones also comprise syn-kinematic injected granite pegmatite dykes and veins (EG-IV) texturally like D2 dykes, but more quartz-and K-feldspar rich (Table 1). An argument in support of D3 age for these dykes is that older EG-III dykes present in the adjacent TTG gneisses have been folded by similar, steeply NNE-plunging folds, and replaced by sheared granite veins (EG-IV) parallel to their axial surfaces (Fig. 14d).

Thin section studies of D3 shear zones show a typical mylonitic foliation consisting of sigmoidal lenses of saussuritized plagioclase clasts (albite), in a fine-grained matrix with syn-kinematic aggregates of recrystallized amphibole (now epidote + chlorite), biotite, and iron oxides (Fig. 14e), accounting for greenschist facies metamorphic conditions during D3.

Post-tectonic granite injections (EG-V)

The youngest felsic intrusions in the WTBC belong to a suite of post-D3 granite pegmatite dykes spanning ages between 1633 and 1562 Ma in the Astridal metasupracrustal belt in Senja [START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. Such pegmatites have patchy and jagged contacts with TTGs and are also found in Kvaløya where they crosscut all EG-I to -IV intrusions and are associated with quartz + biotite + muscovite + epidote mineral assemblages, as in Senja [START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF].

Discussion

Pre-tectonic sill intrusion and emplacement (EG-I)

The Ersfjord Granite body is not a single batholithic pluton as previously assumed [START_REF] Andresen | The age of the Precambrian basement in western Troms, Norway[END_REF][START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF], but rather a set of regionally extensive tabular granite sills (EG-I). The thickest EG-I sills comprise a pervasive elongated fabric which we interpret as magmatic based on intergrowth of crystalline, rectangular feldspar phenocrysts, rhythmic banding/layering, and aligned texture of flaky biotite and hornblende (Figs. 4,5). These textures may have developed by sheet/sill-internal flowage and/or in-situ local fractionation allowing magmatic layers to form in between already emplaced and newly injected sills (Table 1a). The granites possibly mixed with felsic components of the TTG crust, leaving trails of the mafic migmatite neosomes as rafts or pendant zones in conformable pseudo-layers (Fig. 5). This theory is verified by granite sills merging into and embedding mafic bodies (Figs. 5,6), suggesting direct magma injection into the foliated host rocks (cf. [START_REF] Pawley | A user's guide to migmatites[END_REF]. Such a mechanism would indicate upward transfer of voluminous granite melts as high-permeability magma sills into still viscous host rock TTGs (Fig. 7), and where the granite sills became separated from still solid leuco-and melanosome residuum layers (cf., Brown, 2010a[START_REF] Brown | Granite: From genesis to emplacement[END_REF].

Melting and emplacement of the huge amount of EG-I sills may have been triggered by high heat flow, for example in an extensional back-arc setting of the presumed evolving WTBC accretionary system. In this setting the vertical transfer of magma was large enough to segregate multiple, repeated and voluminous batches of melts that migrated into the upper crust along rheological weak fabrics (cf. [START_REF] Hyndman | Subduction zone backarcs, mobile belts and orogenic heat[END_REF][START_REF] Magee | Magma Plumbing Systems: A Geophysical Perspective[END_REF], such as Kvalsund shear zone and Senja shear belt. Then, several sheet-like pulses of magma ascended as extensive sills into the TTGs through the coalescence of either channelized magma segments, fingers, or lobes [START_REF] Pollard | The form and growth of fingered sheet intrusions[END_REF][START_REF] Schofield | Magma fingers and host rock fluidization in the emplacement of sills[END_REF][START_REF] Magee | Lateral magma flow in mafic sill complexes[END_REF][START_REF] Magee | Magma Plumbing Systems: A Geophysical Perspective[END_REF]. Relatively small volumes of magma, however, formed compared to volumes in classic plutons attached to e.g., migmatite gneiss domes (e.g., [START_REF] Whitney | Gneiss domes and crustal flow[END_REF].

Syn-tectonic D1 emplacement of sills during ductile thrusting (EG-II)

The onset of major NE-SW compression in the WTBC may have started after intrusion of EG-I granite sills at c. 1784-1774 Ma [START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF][START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF] in a presumed, closing back-arc system (cf. [START_REF] Silver | Comments on the growth of accretionary wedges[END_REF]. The tectonic-induced EG-II melts were channelized into D1 ductile thrusts subparallel with TTG gneiss foliation and ductile detachment faults (Table 1b) that controlled progressive supply of sill-like magmas [START_REF] Magee | Magma Plumbing Systems: A Geophysical Perspective[END_REF]. Crustal thickening by imbricate D1 thrusting then allowed new, smaller batches of EG-II magma to flow and reactivate the channels, while adjacent portions of the intrusion partly crystallized (cf. [START_REF] Holness | The Traigh Bhàn na Sgùrra sill, Isle of Mull: Flow localization in a major magma conduit[END_REF][START_REF] Currier | Mapping real time growth of experimental laccoliths: The effect of solidification on the mechanics of magmatic intrusion[END_REF] and became folded and transposed in the D1 thrusts (Fig. 10). These thrust-parallel veins and clusters of granite formed synchronously as interstitial melts that partly obliterated the relic mafic pendant fabric and re-melted the Neoarchaean TTG gneiss foliation. Magma injection and local re-melting of the TTGs synchronous with ductile deformation is supported by internal felsic net-veins (Fig. 9a) and may explain why renewed melt migration pathways remained operational over a large time frame (cf. [START_REF] Magee | Lateral magma flow in mafic sill complexes[END_REF]. Furthermore, preliminary age dating shows that the Neoarchaean TTG foliation in areas near main Ersfjord Granite bodies is late-Svecofennian (1.80-1.77 Ga) in age, and thus became fully overprinted and reworked by the regionally widespread D1-foliation (cf. [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF][START_REF] Myhre | U-Pb geochronology along an Archaean geotransect in the West Troms Basement Complex, North Norway[END_REF].

The ductile D1 event in WTBC triggered transfer of repeated EG-II granitic melts at amphibolite facies conditions synchronous with compressional, thrust-type deformation [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF]. Our field data suggest that successive EG-II melts were formed and first used the relict migmatite pendant zones, then the D1 ductile thrusts and reworked TTG foliation as pathways for upward transfer of melts. A two-stage mechanism is favored, suggesting percolative flow of injected granite sills in the magmatic stage (Fig. 5), followed by viscous flow of melts channelized in the migmatite pendants which acted as ductile thrusts (Fig. 10) (cf. Brown and Solar, 1998b;[START_REF] Marchildon | Spatial distribution of melt-bearing structures in anatectic rocks from southern Brittany: Implications for melt-transfer at grain to orogen-scale[END_REF]. A provisional ascent model is that new EG-II magmas were extracted by tectonic reworking and transferred upwards until they reached the near-solid state, foliation-parallel D1 thrusts at higher level in the crust. The granite melts then migrated into the ductile thrusts along hinges and axial surfaces of recumbent isoclinal folds, causing transposition and layer disaggregation (Fig. 10). Thus, the driving force for ascent of new EG-II granite melts was likely strong and successive D1 ductile thrusting/ shearing and syn-tectonic flattening (cf. [START_REF] Vernon | Axial-surface leucosomes in anatectic migmatites[END_REF][START_REF] Weinberg | Magma migration, folding, and disaggregation of migmatites in the Karakoram shear zone, Ladakh, NW India[END_REF]. This occurred in a favorable NE-SW to E-W directed maximum D1 shortening field (Fig. 11a; [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF], based on elongated and sheared mafic pods and boudins, sigmoidal lenses, tight isoclinal fold axes, and stretching lineations in D1 thrusts both inside reworked migmatite zones of the Ersfjord Granite and in adjacent TTG-gneisses (Fig. 10). The spread in D1 fold axes orientation (Fig. 11a) is likely due to strain-dependent reorientation within different D1 shear zones, controlled by their location relative to sill boundaries, thin versus thick sills, and/or internal pendant migmatite zones.

Late-tectonic D2 regional folding and dyke injection (EG-III)

The previous obtained age of 1774 ± 5 Ma for the granite pegmatite dykes at Otervika [START_REF] Corfu | Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archaean and Palaeoproterozoic events and younger overprints[END_REF] constrains the absolute timing of the D2 macro-folding (Table 1c). During this event, both the EG-I and II sills and surrounding TTG foliation were D2 folded and then EG-III injected as granite pegmatite dykes along the axial surfaces and in corresponding D2 thrusts (Figs. 12c,13a,b). The D2 structures also developed by NE-SW to W-E directed maximum principal shortening (Fig. 11b), thus indicating that the D2 macro-folds, corresponding dyke swarm, and D2 thrusts resulted from coaxial crustal shortening relative to D1 [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF]. The metamorphic conditions during D2, however, were slightly lower (upper greenschist facies), but still high enough to transport volatile granitic melts. The difference in metamorphic grade, and c. 10 Ma age span between EG-I and EG-III melts at Otervika (Table 1a, c) favor melt injection during two separate magmatic events, rather than one progressive D1-D2 shortening. Further, the volume of dyke magma injected during the D2 folding was much less, which may indicate waning granitic magmatism (melting) after c. 1784 Ma. This is supported by a lower frequency of EG-III dykes in TTGs compared to the number of EG-I and II sills.

The EG-III pegmatite dykes at Otervika classify as a composite, discordant body of regularly spaced dyke (swarm) with a high aspect ratio [START_REF] Brown | Granite: From genesis to emplacement[END_REF]. Since the pegmatites injected both as dykes and thrusts parallel to the axial-surfaces of D2 folds (Fig. 12c), this suggest ascent of melts in compressional dykes (e.g., [START_REF] Brown | Melt extraction from lower continental crust[END_REF][START_REF] Brown | Synergistic effects of melting and deformation: An example from the Variscan belt, western France[END_REF][START_REF] Brown | Granite: From genesis to emplacement[END_REF], i.e., perpendicular to the regional shortening direction (Fig. 11b). Similar strain-related ascent conduits are recorded in many convergent settings [START_REF] Wickham | The segregation and emplacement of granitic magma[END_REF][START_REF] Lucas | Syn-tectonic magmatism and the development of compositional layering, Ungava orogen (northern Quebec, Canada)[END_REF]Brown and Solar, 1998a;[START_REF] Vernon | Axial-surface leucosomes in anatectic migmatites[END_REF][START_REF] Weinberg | Interaction between deformation and magma extraction in migmatites: Examples from Kangaroo Island, South Australia[END_REF]. For example, where tabular granites that link deeper migmatite zones to shallower plutons are transported in dykes oriented at a high angle to the maximum shortening direction (Reichhardt and [START_REF] Reichardt | Hornblende chemistry in meta-and diatexites and its retention in the source of leucogranites: An example from the Karakoram shear zone[END_REF][START_REF] Brown | Granite: From genesis to emplacement[END_REF]. The EG-III melts were most likely emplaced along semi-ductile, crack-like deformation bands in D2 thrusts (Fig. 12c) (cf. [START_REF] Brown | Melt extraction from lower continental crust[END_REF][START_REF] Brown | Synergistic effects of melting and deformation: An example from the Variscan belt, western France[END_REF]Brown, , 2010b) ) caused by external applied D2 shortening strain rather than by simple melt-internal (magmatic) over-pressure [START_REF] Bons | Stepwise accumulation and ascent of magmas[END_REF][START_REF] Bons | Melt extraction and accumulation from partially molten rocks[END_REF] or dilation in the crust.

The source of EG-III pegmatites is unknown, but an option is local re-melting of EG-I sills and subsequent ascent as melt portions into D2 dykes and thrusts. Arguments in support of re-melting is that isolated EG-III dykes merge out from EG-I sills in the TTGs (Fig. 7b-d). Therefore, and since just a small degree of partial melting is required to generate felsic pegmatites in convergent orogens, local re-melting is more likely than keeping the EG-I sills partial molten for >10 m.y.r.

4. Late/post-tectonic D3 transpression and dyke injections (EG-IV and V)

The last deformation event (D3) in the WTBC records a strain history of transpression, with subvertical folding and orogen-parallel (NW-SE directed) strike-slip ductile shearing (Table 1d; [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF]2015). New-formed granite pegmatite veins, sills, and dykes (EG-IV) were injected as sills and dykes along steep TTG foliation, axial surfaces and limbs of subvertical D3 folds (Fig. 14a-d), and into steep ductile, left-and right slip D3 shear zones that offset D2-dykes (Fig. 14d). These shear zones suffered high strain, internal mylonitization and lateral displacement synchronous with emplacement of the EG-IV melts, still in the ductile regime, but at a slightly higher crustal level (lower greenschist facies conditions) than for the D1 and D2 events. Continued crustal uplift/ exhumation and injection of e.g., Rapakivi-like granites (Rämö and Haapala, 1995;[START_REF] Ernst | Global record of 1600-700 Ma Large Igneous Provinces (LIPs): implications for the reconstruction of the proposed Nuna (Columbia) and Rodinia supercontinents[END_REF] may explain the last granites (EG-V) injected in the WTBC, in the time span 1633-1562 Ma, likely due to post-orogenic, crustal reworking and rejuvenation (cf. [START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF].

Regional implications and geotectonic model

The southwestern margin of the Fennoscandian Shield grew by accretion of juvenile arc-magmatic granitoids during the late-Svecofennian (c. 1.80 Ga), Nordic (c. andGothian (1.64-1.52 Ga) orogenies [START_REF] Gaál | An outline of the Precambrian evolution of the Baltic Shield[END_REF][START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF][START_REF] Bingen | The Mesoproterozoic in the Nordic countries[END_REF]. Farther northwest, the Ersfjord Granite in WTBC is coeval in age with the youngest granitoids of the Transscandinavian Igneous Belt (TIB-1), formed at c. 1.80-1.75 Ga during waning stages of a voluminous, late-Svecofennian arc-magmatic collisional event [START_REF] Åhäll | Growth-related 1.85-1.55 Ga magmatism in the Baltic shield: a review addressing the tectonic characteristics of Svecofennian, TIB 1-related, and Gothian events[END_REF][START_REF] Nironen | The Svecofennian Orogen: a tectonic model[END_REF][START_REF] Ahl | Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon[END_REF]Andersen et al., 2009;[START_REF] Andersson | The Transscandinavian Igneous Belt (TIB) in Sweden: A Review of Its Character and Evolution[END_REF][START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF][START_REF] Gorbatschev | The Transscandinavian Igneous Belt (TIB) in Sweden: a review of its character and evolution[END_REF][START_REF] Högdahl | The transscandinavian igneous belt (TIB) in Sweden: A review of its character and evolution[END_REF]. These TIB-1 granitoids are monzonitic and display I-to A-type geochemical affinities, attesting for melting of mafic to intermediate arc-like crust (Andersen et al., 2009;[START_REF] Andersson | The Transscandinavian Igneous Belt (TIB) in Sweden: A Review of Its Character and Evolution[END_REF][START_REF] Rutanen | Mafic plutonic rocks in a continental-arc setting: geochemistry of 1.87-1.78 Ga rocks from south-central Sweden and models of their palaeotectonic setting[END_REF] and/or mantle-derived crystalline melts [START_REF] Skår | U-Pb geochronology and geochemistry of early Proterozoic rocks of the tectonic basement windows in central Nordland, Caledonides of north-central Norway[END_REF]. Since the same geochemical signatures were obtained for similar aged syeno-granitoids in the WTBC, a comparable source as for the TIB-1 granitoids was proposed [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. The spatial link of the many other c. 1.80-1.75 Ga TIB-1 related granitoid magmatic suites in northern Norway [START_REF] Griffin | Archaean and Proterozoic crustal evolution in Lofoten-Vesterålen, N Norway[END_REF][START_REF] Andresen | Age and tectonic setting of the Tysfjord gneiss granite, Efjord, North Norway[END_REF][START_REF] Korneliussen | The geochemistry of Lower Proterozoic mafic to felsic igneous rocks, Rombak Window, North Norway[END_REF][START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF], and granitoids in the Norrbotten Province of Sweden farther east of the TIB belt (Fig. 1), suggests they may all be co-magmatic and back arc related (e.g., [START_REF] Bergman | Description of regional geological and geophysical maps of northern Norrbotten County (east of the Caledonian orogen)[END_REF]Bergmann, 2018;[START_REF] Martinsson | Age and character of late-Svecokarelian monzonitic intrusions in northeastern Norrbotten, northern Sweden[END_REF].

The Lofoten-Vesterålen AMCG suite intrusions, however, were emplaced mostly as massive plutons in a non-compressive (extensional) environment without large pendants of the host rocks (Griffin et al., 1979;[START_REF] Corfu | U-Pb Age, setting and tectonic significance of the AnorthositeMangerite-Charnockite-Granite Suite, Lofoten-Vesterålen[END_REF][START_REF] Corfu | Multistage metamorphic evolution and nature of the amphibolite-granulite facies transition in Lofoten-Vesterålen, Norway, revealed by U-Pb in accessory minerals[END_REF][START_REF] Coint | Evidence for Silicate-Liquid Immiscibility in Monzonites and Petrogenesis of Associated Fe-Ti-P-rich rocks: Example from the Raftsund Intrusion, Lofoten, Northern Norway[END_REF], and presumably post-tectonic relative to the main Svecofennian Orogeny (cf. [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. Early arc delamination following NE-ward subduction at c. 1.80 Ga is proposed to have started in Lofoten slightly before or synchronous with crustal accretion and re-assembly of Neoarchaean crustal segments farther northeast, i.e., in the WTBC (Fig. 15a; [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF]. In this scenario, the 1.80 Ga Ersfjord Granite sills (EG-I), and granites in Senja intruded into TTGs in a back-arc extensional environment within the central TTG crustal segment on Kvaløya and bounding Neoarchaean shear zones (Senja shear belt, Kvalsund shear zone).

(Fig. 15a), i.e., pre-collisional relative to D1-D3 compressional events (Fig. 15b). A back-arc setting is the only region that can provide enough heat flow for long-term melting and ascent of the large granitoid EG-I sills in a setting adjacent to continental crust affected by compression (e.g., [START_REF] Hyndman | Subduction zone backarcs, mobile belts and orogenic heat[END_REF][START_REF] Currie | The thermal structure of subduction zone back arcs[END_REF][START_REF] Currie | Thinning of continental backarc lithosphere by flow-induced gravitational instability[END_REF].

The presence in WTBC of multiple crustal (TTG) segments, rift-related volcano-sedimentary sequences, fold-thrust belts, and intervening ductile shear zones into which juvenile mafic and felsic/granitoids (EG-II to IV) intruded [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF][START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF], account for continued shortening (D1-D3), amalgamation and melting in an advancing Andean or Cordilleran type accretionary orogenic setting (Fig. 15b). Such orogens are characterized by strong mechanical coupling and upper plate compression and transpression due to oblique assembly, crustal uplift, and thermal rejuvenation (cf. [START_REF] Cawood | Linking accretionary orogens with supercontinent assembly[END_REF][START_REF] Cawood | Accretionary orogens through Earth history[END_REF][START_REF] Lallemand | On the relationships between slab dip, back-arc stress, upper plate absolute motion, and crustal nature in subduction zones[END_REF][START_REF] Lallemand | Subduction dynamics as revealed by trench migration[END_REF]. Similar advancing accretionary events occurred in the WTBC (Fig. 15b,c), northeast of the Lofoten-Vesterålen magmatic arc, during the late-to post-Svecofennian collisional stages, and/or the Nordic and Gothian orogenies (cf. [START_REF] Lahtinen | Paleoproterozoic evolution of Fennoscandia and Greenland[END_REF][START_REF] Dallmeyer | 40Ar/39Ar mineral ages within the Western Gneiss terrane, Troms, Norway: evidence for polyphase Proterozoic tectono-thermal activity (Svecokarelian and Sveco-norwegian)[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. The bounding Senja shear belt and Kvalsund shear zone may have provided the sites of thermal and rheological weakening (cf. [START_REF] Sandiford | Tectonic feedback, intraplate orogeny and the geochemical structure of the crust: A central Australian perspective[END_REF], and thus were favorable pathways for the renewed ascending Ersfjord and Senja EG-II to IV granitoid melts (Fig. 15b,c).

Our proposed advancing accretionary orogenic setting for emplacement of the Ersfjord Granite melts is supported by known melt ascent in both modern and ancient orogens (e.g., [START_REF] Brown | The generation, segregation, ascent and emplacement of granite magma: The migmatite-to crustally-derived granite connection in thickened orogens[END_REF][START_REF] Petford | Granite magma formation, transport, and emplacement in the Earth's crust[END_REF]. Modern examples include the North and South American Cordillera along the eastern Pacific, characterized by accretion and strike-slip motion of earlier rifted arcs and micro-continents, and formation of fold-thrust belts in retro-arcs (e.g., [START_REF] Johnston | The Great Alaskan Terrane Wreck: Reconciliation of paleomagnetic and geological data in the northern Cordillera[END_REF][START_REF] Bergh | Linked thrust and strike-slip faulting during Late Cretaceous terrane accretion in the San Juan thrust system, Northwest Cascades orogen, Washington[END_REF][START_REF] Lee | Petrology and tectonics of Phanerozoic continent formation: From island arcs to accretion and continental arc magmatism[END_REF][START_REF] Cawood | Accretionary orogens through Earth history[END_REF]. Ancient examples are the Neoproterozoic to Palaeozoic Central Asian Orogenic Belt [START_REF] Kröner | Accretionary growth and crust formation in the Central Asian Orogenic Belt and comparison with the Arabian-Nubian shield[END_REF][START_REF] Windley | Tectonic models for accretion of the Central Asian Orogenic Belt[END_REF], the juvenile Palaeoproterozoic Yavapai and Mazatzal provinces [START_REF] Bergh | The Chaparral shear zone of central Arizona; deformation partitioning and heterogenous bulk crustal shortening during Proterozoic orogeny[END_REF][START_REF] Karlstrom | Long-lived (1.8-1.0 Ga) convergent orogen in southern Laurentia, its extensions to Australia and Baltica, and implications for refining Rodinia[END_REF], and Palaeoproterozoic orogens on the Australian craton [START_REF] White | Spatially focused melt formation in aluminous metapelites from Broken Hill, Australia[END_REF][START_REF] Collins | Pervasive magma transfer through the lower-middle crust during noncoaxial compressional deformation: An alternative to diking[END_REF]. In all these accretionary orogens, granitic melts migrated through continental crust by compression, upward via structurally controlled pathways like foliation and ductile, crustal shear zones (e.g., [START_REF] Brown | Crustal melting and melt extraction, ascent and emplacement in orogens: Mechanisms and consequences[END_REF]Brown, , 2010a;;Brown andSolar, 1998a, b, 1999), with ancestor melanosomes [START_REF] White | Spatially focused melt formation in aluminous metapelites from Broken Hill, Australia[END_REF], and by granite melts associated with folds, boudins, and linear features [START_REF] Collins | Pervasive magma transfer through the lower-middle crust during noncoaxial compressional deformation: An alternative to diking[END_REF].

Perspectives for future studies

Since Ersfjord Granite melts injected as sills (and dykes) both during pre-collisional extension and synchronous with convergent D1-D3 tectonic events, a direct spatial and temporal comparison of granitic magmas and ductile fabrics can be made. Our field-based approach provides an excellent basis for further geochronological and petrological-metamorphic studies (work in progress). Specific tasks would be: (1) U-Pb zircon dating of the EG-I through -IV generations of granitic sills and pegmatite dykes, and similar intrusions in the surrounding TTG gneisses, which is critical to genetically link the various melts. (2) Resolving the source of magma from geochemical signatures, e.g., mantle-or lower crust-generated [START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF], and/or by partial melting of host rock gneisses. (3) Testing fluid-induced in situ melting/anataxis from a local source in the adjacent TTGs. (4) Isotopic studies of felsic and mafic melts in the migmatite pendant zones to be compared with leucosome and neosomes of migmatitic TTGs, to test if they are new Palaeoproterozoic melts, or remains of Neoarchaean migmaties. (5) Resolving the source and genesis of D2 and D3 granitic dykes, by re-melting of the pre-tectonic granite sills or from a fluid-enriched migmatite (TTG gneiss) source. 6) Establish the metamorphic history, P-T conditions and evolution of metamorphic minerals grown during the D1-D3 events. Such studies are valid to further test our local field-based granite emplacement model, and in evaluating magma sources and ascent of other TIB-1 granitoid intrusions both in the WTBC and comparable Fennoscandian Shield.

Conclusions 1)

The Ersfjord Granite in the WTBC is not a single batholite body, but a system of tabular granite sills (EG-I) injected into Neoarchaean crustal segments (c. 1.80-1.78 Ga) triggered by pre-existing ductile shear zones and TTG fabrics in a back-arc extensional setting. The EG-I sills have an internal, distributed magmatic layering and rhythmic remains of Neoarchaean mafic migmatite pendant zones.

The magmatic fabric of the sills developed during the melt/sill flowage and assimilation with the surrounding, foliated TTGs, leaving irregular mafic migmatite pendants in conformable layers between the sills. These pendant zones acted as favorable conduits/pathways for later segregation and tectonic ascent of granitic melts.

2) New but smaller granite melts (EG-II) then formed and ascended syn-tectonically in a west-directed imbricate thrust nappes/stack (D1 event; 1.78-1.77 Ga) due to upper plate compression in an advancing Andean-type accretionary orogen. Thrust-parallel EG-II veins and clusters of granite channelized synchronously as interstitial melts that became sheared and partly obliterated the relic mafic pendant fabrics, at medium grade conditions.

3) Later, during a separate low grade tectono-magmatic event (D2; 1.774 Ga) granite pegmatite melts (EG-III) intruded as dyke swarms along the axial-surface of upright D2 macro-folds and in steep D2 thrusts, coaxial to D1 but higher in the accreted and thickened crust. Discordant EG-III dykes formed by compression at a high angle to the maximum D2 strain (NE-SW shortening), and not from melt overpressure. Still younger granite pegmatite melts (EG-IV) intruded along steep strike-slip shear zones and axial-surfaces of subvertical folds, in an orogen-parallel NW-SE shortening strain field (D3 event; c. 1.75 Ga).

4) The 1.80-1.75 Ga Ersfjord Granite suite in WTBC demonstrates granitoid magmatism and melt emplacement during pre-collisional back-arc extension, then continent closure and accretion(D1), coaxial shortening and crustal uplift (D2), transpressive reworking by oblique convergence (D3), and thermal rejuvenation (post-D3), in accord with an evolution history of a small-scale, advancing Andean and/or North American Cordillera type accretionary orogen.

Figure captions

Figure 1. Overview geological map of the Fennoscandian Shield showing the Archaean Kola, Karelian and Norrbotten cratons, timing of major Palaeo-and Mesoproterozoic tectonic events (Lapland-Kola, Svecofennian and Gothian orogens), plutonic rocks of the Transscandinavian Igneous belt, and regional ductile shear zones (from Koistinen et al., 2001 and[START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. Note location of the West Troms Basement Complex and Lofoten-Vesterålen areas to the northwest of the Paleozoic Caledonian Orogen. Abbreviations: BSSZ=Bothnian-Senja shear zone, MOL=Malangen-Onega lineament, R=Rombaken, RLZ=Raahe-Ladoga shear zone, Tys=Tysfjord, TIB=Transscandinavian Igneous Belt, WTBC=West Troms Basement Complex.

Figure 2. Geological and structural overview map with cross-section of the West Troms Basement Complex, after [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF] and [START_REF] Paulsen | Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences[END_REF]. The Ersfjord Granite bodies are in the middle part of the complex, on the island of Kvaløya. Figure 3. Geological and structural map of the Ersfjord Granite suite and the surrounding host rock TTG gneisses and metasupracrustal belts in Kvaløya, with interpreted cross-section. Mapped structures include foliation in the TTG gneisses, and traces of migmatite pendant zones and D1 ductile shear zones inside the Ersfjord Granite. Note also the Tverrfjellet shear zone (TSZ), D1 and D2 shear zones at Buren, and upright macro-folds (D2). Map is modified from [START_REF] Zwaan | Bedrock Map Tromsø[END_REF], [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Haaland | Geometry and kinematic evolution of ductile shear zones in the Ersfjord[END_REF]. Abbreviations: Msb=Mjelde-Skorelvvatn belt, Stb=Steinskardtind belt. Figure 13. a) Macro-scale D2 synform that folds EG-I sills and the surrounding Kattfjord Complex TTGs at Otervika (see location in figure 3) and showing granitic pegmatite dykes (EG-III) intruded along the axial surface of the fold. Note regular dip of the dykes to the SW (right). b) Outcrop photograph of EG-III granite pegmatite dykes that crosscut foliated TTGs along road-cut in 13a. Note regular orientation of some dykes, complex splay geometries of subsidiary dykes, and locally irregular and bifurcating contacts indicating shearing along dyke contacts. The foliation of TTGs dips left (NE) and comprise internal EG-II veins. c) EG-III granite dykes injected at high angle with D1 foliation in Kattfjord Complex gneisses and along the axial surface of asymmetric D2 meso-folds. Note irregular and transposed EG-III veins caused by injection during thrusting. Locality: 1 km north of Kaldfjord (see location in figure 3). d) Details from a mylonitic D2 shear zone with EG-III granite at Buren, displaying internal feldspar clasts with sigmoidal-shape and top-to-the left (west) sense-of-shear. Location: 69⁰43'13N, 18⁰37'2E. e) Thin-section image of the mylonitic texture in EG-III granite at Buren (figure 13d). Sigmoidal and recrystallized quartz lenses are enclosed within a matrix of white mica and biotite, and mica-fishes oblique to the shear zone define S-C structure. Image is oriented W-E and in cross-polarized light. [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. a) Precollisional stage with subduction southwest of Lofoten, then delamination of the mafic lower crust and intrusion of voluminous TIB-1 magmas in Lofoten AMCG-suite (Laurent et al., 2029). Farther northeast 2.4-2.0 Ga rift-basins started to close in between Neoarchaean crustal fragments in WTBC. Extension in back-arcs on Senja and Kvaløya generated large volumes of Ersfjord Granite melts, intruded as EG-1 sills, using Senja shear belt and Kvalsund shear zone as melt pathways. b) Syn-orogenic SW-NE crustal shortening , imbricate nappe thrusting/ stacking, and recumbent folding of arc-related crustal blocks (D1-event) in an evolving accretionary setting. Renewed EG-II Ersfjord Granite melts intruded using EG-1 sills and migmatite pendants as melt pathways. c) Late-tectonic accretion and coaxial, regional macro-folding (D2event) followed by orogen-parallel shortening and transpression (D3 event) [START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF], when the crust uplifted, and terranes fully amalgamated. EG-III and EG-IV granite pegmatite dykes and sills intruded as axial-planar dykes and thrusts in D2 folds, and along subvertical D3 fold limbs and steep D3 strike-slip shear zones, in the vicinity of Senja shear belt and Kvalsund shear zone. Abbreviations: Ab=Astridal belt, KSZ=Kvalsund shear zone, MSB=Mjelde-Skorelvvatn supracrustal belt, RGb= Ringvassøya greenstone belt, Svb= Svanfjellet supracrustal belt, Ssb=Senja shear belt, Tb=Torsnes supracrustal belt, Vg=Vanna Group. Table 1. Summary characteristics of injected Ersfjord Granite magmas in WTBC, termed EG-I to V, and including previous age dating results (from Corfu et al., 2003;[START_REF] Armitage | Structural development of the Mjelde-Skorelvvatn Zone on Kvaløya, Troms: a metasupracrustal shear belt in the Precambrian West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF][START_REF] Myhre | U-Pb geochronology along an Archaean geotransect in the West Troms Basement Complex, North Norway[END_REF][START_REF] Laurent | Building up the first continents: Mesoarchean to Paleoproterozoic crustal evolution in West Troms, Norway, inferred from granitoid petrology, geochemistry and zircon U-Pb/Lu-Hf isotopes[END_REF], structural characteristics, metamorphism, tectonic setting, and tectonic-induced melt emplacement (this work).

Figure 4

 4 Figure 4. a) Panorama view of the main Ersfjord Granite body between Buren and Store Blåmann (see location in figure 3) showing internal tabular fabric dipping gently NW and defining light-colored sheets/sills (EG-I). b) Close-up view of EG-I granite sill with thin-laminated layers and uniform rhythmic banded, dark biotite-hornblende rich granite. Locality, Hatten. c) Magmatic layers of coarsegrained K-feldspar and biotite-hornblende-rich EG-I granite in irregular lens-shaped arrangement within the distributed magmatic fabric. Locality, Store Blåmann. d) Sharp contact between coarse-and

Figure 5 .

 5 Figure 5. Field examples of EG-I granite sills with mafic intercalations. a-b) Road-cut section with sketch interpretation showing coarse-grained EG-I sills. Note irregular lenses and clusters of mafic/amphibolitic pods (dark grey shade) embedded in the granite sills. Locality; south of Grøtfjord. c) Lenses and intercalations of aligned mafic pods within EG-I sill, defining pseudo-layers. Locality, Hatten. d) Massive EG-I granite sill with isolated mafic lenses and pods (dark grey) that are slightly elongated. Note light-colored granite rims around individual mafic pods. Locality; Buren.

Figure 6

 6 Figure 6. a) Outcrop photograph of repeated mafic migmatite zones conformable with massive EG-I sills in the mountain Hatten. b) Section through a migmatite zone at Hatten, with textural details including (c, d) decimeter to meter-thick wedge-shaped, biotite-rich EG-I sills and inter-layered, partly dismembered mafic migmatite gneisses and pods. Hammer for scale is circled yellow.

Figure 7 .

 7 Figure7. Photos of presumed EG-I granites injected as sills into the surrounding TTG gneisses. a) Foliation-parallel K-feldspar rich granite layer/sill in mafic TTGs. Locality, Senja shear belt south of Astridal belt (see location in figure2). Note aligned hornblende defining planar fabric in the granite. b) Series of TTG gneisses intruded by conformable, massive coarse-grained granite sills. Note sharp sill contacts and discordant linkage of small granite vein (dyke) between the two granite layers. Locality: Kvalsund shear zone on Ringvassøya. c) Coarse-grained granite cluster which bifurcates into the foliation of mafic TTGs, in Kvalsund shear zone. d) Massive and coarse-grained granite arranged as wedge-shaped sills around well-foliated mafic gneisses. Locality; Kvalsund shear zone. e) Series of TTG gneisses with foliation-parallel granite layers/sills, one which comprises boudinage (center of photo) and cut by a younger granite dyke (D2) (upper right in photo).

Figure 8

 8 Figure8. a) Photo of mountainside below Hollendaren (see location in figure3), showing EG-I granite sills with an irregular attitude and variable dips, defining internal imbricates and duplex-like structures. Sense-of shear is to the west (left) as apparent from duplex geometries (in center of photo). b) Contact zone between the main Ersfjord Granite body and Kvalsund Gneiss at the mountain Kjølen. Sigmoidal lenses of granite (EG-II) and intercalated amphibolite gneisses are mixed in a ductile thrust system with top-to-the-west shear sense. Geographic location: 69⁰44'43''N, 18⁰46'11''E. c) Close-up view of injected EG-II granite slice and TTG gneiss along thrust surface in figure9b. Note isoclinal fold and transposed EG-II lenses in mica-rich ductile shear fabric.

Figure 9

 9 Figure 9. a) Details from a mafic migmatite zone in between EG-I sills, which is injected by irregular EG-II granite sills (lower part of photo) with internal vein-networks (in center of photo) parallel to a weak ductile foliation (D1). Locality; Buren. b) Mafic migmatite zone with aligned, variously dismembered EG-II sheets/sills of granite injected parallel to a foliation (D1), some surrounding mafic pods. Locality; Store Blåmann. c, d) Thin-section image of foliated biotite-rich EG-II granite sill (as in 9b) showing granoblastic microcline, albite, and quartz in a well-defined lepidoblastic biotite D1 oliation (D1). e, f) Thin section image of foliated mica-rich granite gneiss with garnet porphyroblast in mica-rich D1 foliation. Locality; Tverrfjellet shear zone. Images are shown in cross-polarized light (c, e) and plane-polarized light (d, f).

Figure 10 .

 10 Figure 10. Outcrop photographs of syn-tectonic EG-II sills and veins within migmatite zones reworked as D1 ductile shear zones. a) Coarse-grained EG-II veins injected along D1 foliation and isoclinally folded. Locality: Hatten, 69⁰40'44''N, 18⁰32'52''E. b) Multiple coarse-grained EG-II granite sills that are internally folded by isoclinal folds and transposed, dismembered, and embedded axial-planar into

Figure 11 .

 11 Figure11. Lower-hemisphere stereo-nets showing structural orientation data for the main D1 and D2 event features in key areas within and outside the main Ersfjord Granite bodies. a) D1 ductile shear zone foliation outlined as single great circles, average orientation, and poles. Separate D1 stereo-plots below are from key localities at Tverrfjellet, Hatten, and Buren. Great circles display an average D1 shear zone orientation for each locality, with enclosed D1 fold axis orientations, and stretching lineations. Note the large spread in trend of measured fold axes along average D1 shear zones, whereas stretching lineations vary less, between WNW and WSW. b) Orientation data for D2 macrofolded D1 foliation (great circles and poles) in Tverrfjellet shear zone, TTGs at Tverrfjellet and between Mjelde-Skorelvvatn and Steinskardtind supracrustal belts, and from D1 and D2 shear zones at Buren. Local D2 fold axis orientations are obtained from constructed β-axes. Note that variations in D2 fold axial surfaces infer refolding by large-scale D3 folds.

Figure 12 .

 12 Figure 12. Panorama view (a) and interpretation (b) of the D2 folded Tverrfjellet shear zone and overlying EG-II Ersfjord Granite sills at the contact with Gråtind Migmatite TTGs southwest of Middagstind (see figure 3 for location). Note intrafolial D1 folds and sigmoidal mafic pods and EG-II lenses in Tverrfjellet shear zone with consistent top-SW shear sense, and the slightly discordant contact to TTGs below. Above the Tverrfjellet shear zone, multiple and conformable D1 shear zones alternate with massive EG-I sills. c) Sketch summarizing features related to D2 macro-folds in TTGs at Otervika. Note axial-planar D2 thrust with injected EG-III veins and associated thrust-related folds (at Buren), and injected EG-III dykes (see details in figure 13).

Figure 14

 14 Figure 14. a) Steep D3 ductile shear zone with internal, red-colored EG-IV granite pegmatite, arranged as a sheet truncating subhorizontal (presumed EG-I) sills. Locality; Senja shear belt. 69⁰27'35''N, 18⁰11'21''E b) Close-up horizontal view of the shear zone in 14a, showing EG-IV granite with ductile foliation, lens-shaped K-feldspar clasts, and a mica-rich matrix. c) Steep D3 shear zone inside Ersfjord Granite sills at Hatten. 69⁰40'48''N, 18⁰33'12''E. Note EG-I sills drag-folded sinistrally into the shear zone boundaries. View is to the north. d) Horizontal view of a discordant EG-III pegmatite granite dyke in foliated TTGs. The dyke is D3 folded and transposed into a steep D3

Fig. 15 .

 15 Fig. 15. Schematic geotectonic evolution and emplacement model for the 1.80-1.75 Ga Ersfjord Granite suite and the Senja granitoids in the WTBC, and their relation to the Lofoten-Vesterålen TIB-1 Magmatic Suite in a SW-NE diagrammatic transect (modified after[START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF][START_REF] Bergh | Multiple post-Svecofennian 1750-1560 Ma pegmatite dykes in Archaean-Palaeoproterozoic rocks of the West Troms Basement Complex, North Norway: Geological significance and regional implications[END_REF]. a) Precollisional stage with subduction southwest of Lofoten, then delamination of the mafic lower crust and intrusion of voluminous TIB-1 magmas in Lofoten AMCG-suite(Laurent et al., 2029). Farther northeast 2.4-2.0 Ga rift-basins started to close in between Neoarchaean crustal fragments in WTBC. Extension in back-arcs on Senja and Kvaløya generated large volumes of Ersfjord Granite melts, intruded as EG-1 sills, using Senja shear belt and Kvalsund shear zone as melt pathways. b) Syn-orogenic SW-NE crustal shortening, imbricate nappe thrusting/ stacking, and recumbent folding of arc-related crustal blocks (D1-event) in an evolving accretionary setting. Renewed EG-II Ersfjord Granite melts intruded using EG-1 sills and migmatite pendants as melt pathways. c) Late-tectonic accretion and coaxial, regional macro-folding (D2event) followed by orogen-parallel shortening and transpression (D3 event)[START_REF] Bergh | Neoarchaean to Svecofennian tectono-magmatic evolution of the West Troms Basement Complex, North Norway[END_REF], when the crust uplifted, and terranes fully amalgamated. EG-III and EG-IV granite pegmatite dykes and sills intruded as axial-planar dykes and thrusts in D2 folds, and along subvertical D3 fold limbs and steep D3 strike-slip shear zones, in the vicinity of Senja shear belt and Kvalsund shear zone. Abbreviations: Ab=Astridal belt, KSZ=Kvalsund shear zone, MSB=Mjelde-Skorelvvatn supracrustal belt, RGb= Ringvassøya greenstone belt, Svb= Svanfjellet supracrustal belt, Ssb=Senja shear belt, Tb=Torsnes supracrustal belt, Vg=Vanna Group.

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Commenté [LA5]: It is not clear in fig 10e what are the EGII layers with respect to EGI symbols. May be change the size or density of cross symbols for EGII...

Acknowledgements

The field-based data for this article were obtained through several years of study by the first author, and more detail structural analysis (MSci) undertaken by the second author, and by research partners at the Geological Survey of Norway and Université d'Orléans, France. The work is part of ongoing regional tectono-magmatic studies in the WTBC at UiT-The Arctic University of Norway. Financial support was achieved from UiT.