Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 1 of 26 1 2 Canadian Journal of Earth Sciences (Author Accepted Manuscript) U–Pb zircon geochronology and implications of Cambrian plutonism in the Ellsworth belt, Maine 3 4 Jeffrey C. Pollock1, Douglas N. Reusch2, and Gregory R. Dunning3 5 1Department of Earth and Environmental Sciences, Mount Royal University, Calgary, AB T3E 6K6, 6 Canada, jcpollock@mtroyal.ca 7 2Department of Geology, University of Maine at Farmington, Farmington, ME 04938, USA 8 3Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada 9 10 ABSTRACT 11 The Ellsworth belt is one of several fault-bounded blocks exposed along the southeastern coast of Maine 12 that formed within Ganderia. New ID-TIMS U–Pb geochronological data integrated with field relationships 13 provide additional insights into the timing of magmatism and deformation in the Ellsworth belt. The 14 deformed Lamoine Granite was selected for U–Pb zircon analysis in order to: i) establish the protolith age; 15 ii) provide direct temporal constraints on regional low-grade metamorphism and deformation; and iii) 16 elucidate relationships between the Ellsworth belt and coeval rocks elsewhere in the Appalachian orogen. 17 The Lamoine Granite was emplaced within the Ellsworth Schist at 492 ± 1.7 Ma; this is the first unequivocal 18 evidence for a Furongian magmatic event in the Ellsworth belt. The schistosity in the Lamoine Granite is 19 parallel to the main fabric of the host Ellsworth Schist and provides a maximum estimate for timing of the 20 regional metamorphic overprint. Widespread deformation in the Ellsworth belt where kinematic indicators 21 indicate a top-to-northwest sense of shear is attributed to thrusting during which progressive horizontal 22 shortening, caused crustal thickening and peak greenschist facies metamorphism. The Cambrian U–Pb age 23 permits correlation of the Lamoine Granite with the Cameron Road Granite in the Annidale belt of New 24 Brunswick where subduction-related magmas intruded the Penobscot arc–back-arc and were subsequently 25 deformed during the Penobscot Orogeny. 26 27 Keywords: Appalachians, Ganderia, geochronology, granites, Maine, Cambrian 28 29 30 31 PREAMBLE The Cambrian Ellsworth belt occupies the eastern portion of the Penobscot Bay inlier, coastal 32 Maine (Fig. 1; Reusch et al. 2018). It remains an inadequately documented yet highly significant part of 33 Ganderia, the leading tectonic element in the peri-Gondwanan realm of the Appalachian orogen (Hibbard 34 et al. 2007). Bimodal volcanic rocks of the Ellsworth belt and a slice of mantle peridotite have been © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 35 interpreted to record rifting of Ganderia from Gondwana between 510 and 500 Ma (Schulz et al. 2008; 36 van Staal et al. 2012). Its complex, heterogeneous deformation suggests a protracted but still poorly 37 understood accretionary history. While Ganderia’s Paleozoic tectonic evolution is well established in 38 other parts of the Appalachian orogen (e.g., Rogers et al. 2006; Johnson et al. 2012; Pollock et al. 2012), a 39 detailed understanding of the Ellsworth belt’s role in this evolution has been hampered by a dearth of 40 high-precision isotopic age determinations. 41 Plutonic rocks are abundant throughout the Penobscot Bay inlier. The anomalous pre-Silurian 42 deformed Lamoine Granite in the Ellsworth belt is of special interest because it contrasts with the 43 majority of Silurian to Devonian massive plutons (e.g., Stewart 1998; Tucker et al. 2001). However, 44 rather little is known of the age, character, and significance of this penetratively deformed and 45 metamorphosed unit—specifically whether it represents basement, synrift magmatism, or post-rift 46 subduction-related magmatism. Detailed bedrock mapping (Reusch and Hogan 2002; Reusch 2003a; 47 Pollock 2008) suggested that it may be coeval with, or pre-date, adjacent Cambrian volcanic rocks. 48 In the Ellsworth belt, a major unanswered question concerns the regional tectonic significance of 49 an angular unconformity between the Ellsworth Schist and overlying Castine Volcanics. The Lamoine 50 Granite was speculated to contain the same foliation as within pebbles of presumed Ellsworth Schist in 51 the basal conglomerate of the Castine Volcanics. Other reasons for selecting the Lamoine Granite for U– 52 Pb zircon geochronology were to: i) test whether these outcrops represent isolated exposures of Ganderian 53 basement; ii) provide a maximum age for regional greenschist metamorphism and northwest-vergent 54 deformation; and iii) compare its age with previously published ages from the region (e.g., Tucker et al. 55 2001; Schulz et al. 2008). 56 In this study, we present a new high precision U–Pb zircon age by ID-TIMS on the deformed and 57 metamorphosed Lamoine Granite that may bear on the nature of the Ellsworth-Castine unconformity. 58 Implications of the new U–Pb age are used in conjunction with data from regional field investigations 59 (Reusch 2003b; Pollock 2008) to compare the history of granitic magmatism, deformation and regional 60 metamorphism in the Ellsworth belt with the interpreted tectonic evolution of Ganderia elsewhere in New 61 England (e.g., Putnam-Nashoba belt) and Atlantic Canada (e.g., Annidale belt and Exploits subzone). 62 GEOLOGICAL SETTING 63 The Penobscot Bay inlier, ca. 4500 km2 in area, extends from the Sennebec Pond Fault west of 64 the Camden Hills on the west shore of Penobscot Bay to the east shore of Frenchman Bay and beyond. It 65 hosts one of the most complete pre-Silurian sequences in Ganderia of the Appalachian peri-Gondwanan 66 realm (Hibbard et al. 2007). The inlier comprises the dominantly continental St. Croix and Islesboro belts 67 (Reusch et al. 2018) and, to the east, the Ellsworth belt of contrasting oceanic affinity (Schulz et al. 2008). 68 The Islesboro belt contains the oldest known Gondwanan Proterozoic basement in Maine. The Penobscot © The Author(s) or their Institution(s) Page 2 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 3 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 69 Bay inlier is juxtaposed with strata of the Fredericton Trough along the Sennebec Pond Fault to the 70 northwest. Silurian strata of the Coastal Volcanic belt unconformably overlie the inlier to the southeast. 71 The Ellsworth belt extends for over 250 km along the south coast of Maine-New Brunswick and 72 is interpreted from seismic data (Stewart 1998) to be several kilometres thick. It comprises a structurally 73 complex supracrustal assemblage of mainly low-metamorphic grade. Rocks include polydeformed quartz- 74 feldspar-chlorite-mica schists (Ellsworth Schist) and Miaolingian bimodal volcanic rocks of marine 75 origin. Minor occurrences of pelagic chert, limestone, and black shale are present on North Haven Island; 76 serpentinized peridotite is present on Deer Isle (Reusch et al. 2018). The Ellsworth Schist, dominant 77 component of the belt in the study area between Penobscot Bay and Frenchman Bay (Fig. 2), is 78 juxtaposed northwestward against sedimentary rocks of the St. Croix belt along the steeply dipping Turtle 79 Head fault. Westward, ca. 3 km northeast of Castine, the Ellsworth belt structurally overlies younger 80 Penobscot Formation metamorphosed black shales of the St. Croix belt. Basement of the Ellsworth belt is 81 nowhere exposed, however, Nd- and Pb-isotopic data (Schulz et al. 2008) suggest it resembles 82 Neoproterozoic Ganderian basement in Atlantic Canada. 83 84 Lamoine Granite 85 Within the Ellsworth belt, the Lamoine Granite is a 1500 m long, east-west striking sill that crops 86 out along the north shore of Mount Desert Narrows (Fig. 3A). The unit dips moderately to the south and 87 has a maximum width of ca. 100 m. It is a white to pale-grey-weathered granite composed of medium- 88 grained, equigranular anhedral quartz and feldspar; the assemblage is metamorphosed to lower 89 greenschist (chlorite-muscovite) facies. Fracture surfaces are commonly hematite coated. The granite is 90 flanked by the Ellsworth Schist on its north side but an unequivocal intrusive contact with the schist is 91 nowhere exposed. Both McGregor (1964) and Reusch (2003a) interpreted the Lamoine Granite to have 92 been emplaced in the Ellsworth Schist as a hypabyssal pluton related to the Rhyolite of Goose Cove. The 93 schistosity (Fig. 3B) in the Lamoine Granite is defined by strongly aligned muscovite and chlorite that 94 parallel the regional schistosity in the Ellsworth Schist. The granite, therefore, pre-dates the main episode 95 of deformation in the Ellsworth belt. 96 Additional relative age constraints are provided by an undeformed, massive flow-laminated 97 rhyolite dyke (Reusch 2003b) that extends from Lamoine Beach to Racoon Cove (Fig. 2). This intrusion 98 clearly crosscuts the penetrative D2 fabric present in the Lamoine Granite and Ellsworth Schist. The dyke 99 is interpreted as a feeder to the nearby Silurian (424 ± 2 Ma) Cadillac Mountain intrusive complex 100 (Seaman et al. 1995). 101 102 Ellsworth Schist © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 103 The Ellsworth Schist (Smith et al. 1907; Schulz et al. 2008) of the Ellsworth belt comprises a 104 structural assemblage of polydeformed and metamorphosed bimodal volcanic and sedimentary rocks. The 105 unit is dominated by a white-weathering, dark green quartz-feldspar-muscovite-chlorite rock—a phyllite 106 to schist consisting of alternating laminae of quartz-feldspar and chlorite-rich mafic material. Stewart 107 (1998) described bimodal marine volcanic rocks in 10–100 m thick units. Basalt flows and pillows 108 typically contain chlorite, actinolite, and minor epidote and mm-size feldspars. Rhyolite layers, which 109 range in thickness from several cm to 1 m thick and more, are typically grey and weather cream to white; 110 some are interpreted as quartz and/or feldspar crystal tuffs. The Egypt member of the Ellsworth Schist is a 111 ca. 1 km thick assemblage of metamorphic rocks exposed in the core of a late (D3) synform. It consists of 112 feldspar-porphyroblastic schists, amphibolites, and greenstones. The Morgan Bay member of the 113 Ellsworth Schist, which crops out on the west shore of Union River Bay, comprises medium-bedded 114 pelitic schists, impure quartzites, and minor conglomerate. The age of the Ellsworth Schist is constrained 115 by a U–Pb zircon age of 508.6 ± 0.8 Ma from quartz-phyric felsic tuffs at a location ca. 25 km to the 116 southwest of the Lamoine Granite (Schulz et al. 2008). 117 Metamorphism 118 The Ellsworth Schist is regionally metamorphosed to greenschist facies. Mineral assemblages 119 throughout the unit are characterized by quartz and albite, with abundant chlorite ± epidote, and the 120 replacement of plagioclase and K-feldspar by muscovite. Most quartzo-feldspathic layers are bounded by 121 layers of biotite-muscovite-chlorite. The highest-grade metamorphic rocks (M3) occur in the distinctly 122 younger contact aureoles of Silurian and younger plutons, where pelitic layers of the Ellsworth Schist 123 contain appreciable andalusite, cordierite, and tourmaline (Reusch 2003a). 124 Deformation 125 Several phases of deformation are identified in the Ellsworth Schist. Outside of the Morgan Bay 126 member, unequivocal sedimentary bedding is nowhere readily discernible. The oldest fabric preserved 127 within the Ellsworth Schist is a well-developed, thin segregation of green chlorite and white sericite. The 128 dominant foliation is a composite schistosity, S2, which was formed by transposition of the earlier S1 129 schistosity (Fig. 3C). This main D2 fabric along Mount Desert Narrows is subhorizontal to moderately 130 dipping across the open F3 Hancock-Trenton antiform; farther north, it is moderately developed to locally 131 intense and becomes steep close to the Turtle Head fault. Ductile deformation associated with D2 is 132 evident from tight to isoclinal asymmetric folds developed in thin quartz laminations, sigmoid quartz 133 veins, and S–C foliations in shear bands (Fig. 4). These kinematic indicators associated with the D2 fabric 134 indicate a predominant top-to-northwest sense of shear. Associated with the S2 foliation is a well- 135 developed lineation (L2), outlined by the preferred orientation of syn-kinematic quartz crystals and pyrite 136 aggregates. Most of the elongation lineations measured on S2 display a (pre-F3) preferred gentle plunge to © The Author(s) or their Institution(s) Page 4 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 5 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 137 the southeast (Fig. 5). Minor late phase folds are present locally. The D3 deformation—e.g., Hancock- 138 Trenton antiform ca. 2 km north of the Lamoine Granite—consists of large-scale asymmetric, open to 139 tight folds (F3) with subvertical axial surfaces and subhorizontal east-west-trending fold axes that are 140 distinct from the orientation of F2 fold axes. A younger S3 crenulation cleavage developed in 141 phyllosilicate layers overprints the main S2 schistosity and is coplanar with D3 fold axial surfaces. D3 is 142 attributed to the latest Silurian–Devonian Acadian Orogeny. 143 Contact relationships 144 The stratigraphic base of the Ellsworth Schist is not exposed; however, it structurally overlies 145 metamorphosed black shales of the Cambrian–Ordovician Penobscot Formation (Osberg et al. 1985; 146 Reusch 2003a). The Ellsworth Schist is overlain by volcanic rocks of the Castine Volcanics in eastern 147 Penobscot Bay and along the Bagaduce River east of Castine. The Castine Volcanics comprise a 2 km 148 thick sequence of subaqueous rhyolite and basalt, locally pillowed; interbedded marine volcaniclastic 149 sedimentary rocks; sparse impure carbonate beds; layers of iron- and manganese-rich marine chemical 150 precipitates; and a major volcanic-hosted massive sulphide deposit (Schulz et al. 2008). Rocks of the 151 Castine Volcanics are metamorphosed to sub-greenschist (chlorite) facies and generally lack a penetrative 152 foliation. The rocks are folded into a series of open folds that have long wavelengths and small 153 amplitudes with northeasterly trends (Stewart 1998). Eruption of the Castine Volcanics during the 154 Drumian is established by overlapping zircon ages of 503.5 ± 2.5 Ma from fine-grained felsic tuff (Schulz 155 et al. 2008) and 503 ± 4 Ma from massive rhyolite (Ruitenberg et al. 1993). A thin basal conglomerate 156 marks the Ellsworth-Castine contact (Fig. 3D). The conglomerate contains matrix-supported angular to 157 subrounded pebbles of green silicic metamorphic rock (Stewart 1998) that are interpreted as clasts of the 158 underlying Ellsworth Schist implying a basal angular unconformity/nonconformity. 159 160 161 U–Pb GEOCHRONOLOGY A sample of Lamoine Granite was collected from the southwest edge of Lamoine Beach on the 162 north shore of Mount Desert Narrows, Hancock County, Maine (UTM: 19N 555854, 4921932, NAD 27). 163 Sample preparation and analyses were performed at the Radiogenic Isotope Laboratory, Memorial 164 University of Newfoundland utilizing isotope dilution-thermal ionization mass spectrometry. Zircons 165 were isolated from ca. 30 kg of unweathered rock using a jaw crusher and Bico disc mill, and 166 concentrated using a Wilfley table, diiodomethane (CH2I2), and a Frantz isodynamic separator. Individual 167 zircon crystals were individually hand selected from the least magnetic fraction using a binocular 168 stereomicroscope. All zircons were air abraded (Krogh 1982) to remove the metamict outer surfaces in 169 order to reduce the effects of radiogenic Pb loss and age discordance. Zircon dissolution was carried out 170 with HF and HNO3 in Teflon bombs and mixed with a 205Pb/235U isotope tracer. U and Pb were separated © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 171 by anion exchange chromatography and loaded on a Re filament for analysis using a Finnigan MAT 262V 172 thermal ionization-mass spectrometer following the procedures of Sánchez-García et al. (2008). Atomic 173 ratios were corrected for fractionation, spike, and laboratory blank of 1 pg of common lead at the age of 174 crystallization calculated from the model of Stacey and Kramers (1975), and 1 pg U blank. Analytical 175 uncertainties are cited at the 95 per cent confidence interval. Age calculations and U–Pb data were plotted 176 using the Isoplot program of Ludwig (2012) with the 238U (1.55125 × 10–10 a–1) and 235U (9.8485 × 10–10 177 a–1) decay constants and present day 238U/235U ratio of 137.88 determined by Jaffey et al. (1971). 178 The Lamoine Granite yielded abundant, predominantly clear, euhedral prismatic crystals that vary 179 in length between 50 μm and 150 μm on the long axis (Fig. 6). Three fractions of four or five zircon 180 crystals were analyzed and produced mutually overlapping and concordant points (Fig. 7). The fractions 181 have low uranium contents and 206Pb/238U ages between 490 ± 4.0 and 494 ± 4.6 Ma. (Table 1). The 182 weighted average of all three analyses is 492 ± 1.7 Ma (95 per cent confidence interval, MSWD = 0.73), 183 which is the emplacement age of the Lamoine Granite. 184 185 DISCUSSION 186 Ellsworth deformation and metamorphism 187 Our U–Pb data from the Ellsworth belt provide new constraints on granitic magmatism with 188 implications for Paleozoic tectonothermal events elsewhere in Ganderia. The 492 ± 1.7 Ma age of the 189 Lamoine Granite records Cambrian magmatism within the Ellsworth belt, and is the youngest pre- 190 metamorphic age. This precludes the Lamoine Granite from representing crustal basement to the 191 Ellsworth belt. 192 On the basis of field relationships, McGregor (1964) and Reusch (2003a) interpreted the Lamoine 193 Granite as a high-level intrusion that is comagmatic with the Goose Cove rhyolite of the Ellsworth Schist 194 (Fig. 2). The age obtained in this study, however, demonstrates that the pluton is ca. 16 million years 195 younger than the Miaolingian (508.6 ± 0.8 Ma) volcanic rocks from Sand Point (South Blue Hill) 22 km 196 to the southwest (Schulz et al. 2008). Thus, the Lamoine Granite represents a hitherto unrecognized 197 Furongian magmatic event in the Ellsworth belt. 198 The age of the Lamoine Granite constrains the timing of polyphase deformation and 199 metamorphism in the Ellsworth belt. The Lamoine Granite was emplaced ca. 16 million years after 200 deposition of the protolith of the sample of Ellsworth Schist collected from South Blue Hill (Schulz et al. 201 2008), and the granite has the same D2 fabric as the enclosing schist. The schistosity in the Lamoine 202 Granite, defined by chlorite and muscovite, is parallel to the schistosity (S2) in the Ellsworth Schist, 203 suggesting that both units were simultaneously metamorphosed to greenschist facies. Complicating 204 matters, the S2 fabric in the Ellsworth Schist transposes the S1 (metamorphic) compositional layering. © The Author(s) or their Institution(s) Page 6 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 7 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 205 Specifically, the Lamoine Granite is reported to cut the earlier metamorphic foliation (S1) in the Ellsworth 206 Schist (J.P. Hibbard, personal communication, 2007). Stewart et al. (1995) interpreted penetrative 207 deformation and greenschist-facies metamorphism in the Ellsworth Schist to have occurred prior to 208 deposition of the overlying ca. 503 Ma Castine Volcanics. However, if the schistosity in the Lamoine 209 Granite and main fabric in the Ellsworth Schist are contemporaneous, it indicates that development of the 210 regional metamorphic foliation (S2) must post-date emplacement of the 492 Ma granite intrusion. 211 Therefore, the Furongian age of the Lamoine Granite provides a minimum age for S1 and a maximum age 212 for the D2 structural-metamorphic (M2) overprint. 213 Emplacement of the Lamoine Granite was succeeded by a regional shortening event and 214 development of the main fabric of the Ellsworth Schist. The penetrative asymmetry of small-scale folds 215 and S–C shear bands—showing overall top-to-northwest kinematics (Reusch 2003a)—indicates 216 progressive horizontal shortening and crustal thickening attributed to thrust faulting (Hibbard 1995). The 217 L2 lineation occurs on the main foliation plane which is parallel to the plane of best cylindrical fit of 218 strongly non-cylindrical D2 fold hinges (Fig. 5). We interpret the elongate L2 mineral lineation to have 219 formed synchronously with tight to isoclinal folds of quartz layers in the S2 fabric. Regionally, except 220 where the mineral lineation is steeply plunging along faults, most of the L2 stretching lineations measured 221 on S2 display a preferred northwest-southeast plunging orientation at shallow angles. This indicates a 222 northwest-southeast oriented sense of shearing and thrusting. The typically southeast-plunging L2 mineral 223 stretching lineation is consistent with overall top-to-northwest transport. 224 Regional shortening of the Ellsworth belt was a tectonometamorphic event that post-dates 225 emplacement of the Lamoine Granite and formed under greenschist facies conditions in the mid-crust. 226 Abundant microfractures along fold hinges, and presence of deformed extensional quartz veins associated 227 with the S2 foliation (Fig. 4B), are consistent with a brittle strain pattern of deformation under conditions 228 of low deviatoric stress at a relatively high structural level in the lithosphere. However, the L2 stretching 229 lineation associated with the primary S2 foliation, and intrafolial folds, are semi-ductile structures. Their 230 co-existence implies deformation across the brittle-ductile transition. 231 In the Ellsworth belt, the minimum age of thrusting and associated metamorphism is constrained 232 by relatively unstrained fossiliferous rocks of the Silurian Ames Knob Formation. A specimen of 233 Pentamerus collected from near the base of the formation on North Haven Island is interpreted to be late 234 Llandovery (Brookins et al. 1973; Berry and Boucot 1970) which suggests that juxtaposition of the 235 Ellsworth belt with the St. Croix belt occurred prior to the Telychian. These relationships preclude 236 correlation of D2 in the Ellsworth belt with the Acadian orogeny; rather, D3 is the local manifestation of 237 the Acadian Orogeny. 238 © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 239 240 Implications for Cambrian unconformity A maximum 492 Ma age for regional metamorphism (M2) indicates that an earlier thermal event 241 produced the S1 fabric present in the Ellsworth Schist. Burial of the protolith, uplift and erosion of the 242 schist would need to have occurred in the short time span between the 509 Ma eruption of tuff in the 243 Ellsworth Schist and deposition of the Castine Volcanics ca. 503 Ma. Stewart and Wones (1974) 244 interpreted the penetrative deformation in the Ellsworth Schist to be absent in the Castine Volcanics. The 245 lack of refolded D1 structures in the Ellsworth Schist is consistent with interpretation of S1 as a gravity- 246 driven viscous compaction foliation. We suggest that S1/M1 may simply reflect compaction of hot 247 volcanogenic sediments. 248 Clasts of strained Ellsworth Schist that occur at the base of the Castine Volcanics, however, 249 indicate that the schist was deformed prior to incorporation into conglomerate beds and therefore must 250 record a deformation event prior to erosion from their source rocks. The unconformity at the base of the 251 Castine Volcanics occurred after D1 in the Ellsworth Schist, but before D2 responsible for the regional 252 greenschist facies metamorphism throughout the Ellsworth belt. 253 Age constraints and structural evidence suggest that both the Ellsworth Schist and Castine 254 Volcanics were metamorphosed in a single regional thermal event. The Castine Volcanics evidently 255 escaped the effects of the regional D2 shortening event that are prominent in the Ellsworth Schist. 256 Inhomogeneous deformation during thrusting, therefore, may be the primary control on contrasts in the 257 magnitude and nature of deformation in the Ellsworth belt. 258 259 Regional correlations in Ganderia 260 The new date for the Lamoine Granite allows comparison with the timing of similar magmatic 261 rocks elsewhere in the Appalachian orogen (Fig. 8). Metavolcanic rocks of the Gushee member of the 262 Penobscot Formation in the St. Croix belt yield less precise average U–Pb zircon ages (ca. 490–487 Ma, 263 Berry et al. 2016) that are slightly younger than the 492 Ma age of intrusive magmatism in the Ellsworth 264 belt. This correlation is significant, as structures and foliated metamorphic rocks in the St. Croix belt may 265 help to constrain when the Ellsworth and St. Croix belts were juxtaposed. Asymmetric low-angle folds 266 and old-over-young relationships indicate northwest-directed thrusting of the Rockport Group over the 267 Benner Hill Formation along the Clam Cove fault (Osberg and Berry 2020). Emplacement and 268 deformation must post-date rocks of the Benner Hill Formation that contain deformed Sandbian–Katian 269 brachiopods (Berry et al. 2016). The minimum age of juxtaposition is provided by metamorphism under 270 low-pressure amphibolite-facies conditions related to intrusion of high-level plutons in the Přídolí (West 271 et al. 1995). It is possible, considering the common polarity of structures, that the D2 deformation in the 272 Ellsworth belt and deformation in the St. Croix belt are related and coeval. This interpretation would © The Author(s) or their Institution(s) Page 8 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 9 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 273 imply a maximum Katian age for northwest-directed thrusting and peak metamorphism in the Penobscot 274 Bay inlier. 275 Subvolcanic and intrusive rocks of the Annidale belt of southern New Brunswick are obvious 276 correlatives of the Lamoine Granite. The 493 ± 2 Ma (McLeod et al. 1992) subvolcanic rhyolite and felsic 277 breccia of the Lawson Brook Formation and penetratively deformed 490 ± 2 Ma Cameron Road Granite 278 have LREE-enriched geochemical signatures (Johnson et al. 2012) consistent with magmatism influenced 279 by subducting oceanic lithosphere in a back-arc setting. The age of the Cameron Road Granite, its 280 composition, hypabyssal textural features, and post-emplacement schistosity—all support the assertion 281 that the Lamoine Granite is consanguineous. 282 Temporally equivalent volcanic and plutonic rocks resembling those of the Ellsworth belt are 283 common in the central Newfoundland type area of Ganderia. The Lamoine Granite is coincident with the 284 493.9 +2.5/−1.9 Ma Pipestone Pond and Coy Pond ophiolite complexes (Dunning and Krogh 1985) of the 285 Exploits subzone in Newfoundland. The latter are interpreted to represent remnants of an ophiolite belt 286 generated in a back-arc setting (Jenner and Swinden 1993). Furongian plutonic and volcanic elements of 287 both the Annidale belt and Exploits subzone are inferred to represent a magmatic arc system (Penobscot 288 arc–backarc), formed upon Neoproterozoic basement along the margin of Ganderia. In contrast, the 289 Miaolingian volcanic rocks of the Ellsworth belt are viewed as an oceanic rift that developed inboard 290 (southeast, present day coordinates) of the ocean-facing margin of the active Penobscot arc (Schulz et al. 291 2008). 292 Similar rock types and relationships are also preserved in southeast New England. Kay et al. 293 (2017) correlated metavolcanic and sedimentary rocks in the high-grade Putnam-Nashoba belt with 294 bimodal volcanic and sedimentary sequences in the Annidale belt. Lithological, structural geochemical 295 and geochronological data support a model of these terranes representing the back-arc component of the 296 Furongian–Early Ordovician Penobscot arc–back-arc system. This same interpretation is implied by 297 Kuiper (2016). They consider the Ellsworth belt to have occupied a more proximal (southeast) location 298 with respect to Gondwana, consistent with its interpretation as an oceanic rift (Schulz et al. 2008) that led 299 to separation of Ganderia from Gondwana. 300 301 Tectonic interpretation 302 The 492 Ma Lamoine Granite strongly resembles the 490 Ma Cameron Road Granite of the 303 Annidale belt, 250 km distant in New Brunswick. In addition to similar age and lithology, both display a 304 strongly northwest-vergent fabric. The latter is associated with supra-subduction zone volcanism in the 305 back-arc region of the Penobscot arc (Johnson et al. 2012). In Maine, within the adjacent St. Croix belt, 306 metavolcanic rocks of the 490–487 Ma Gushee member ca. 50 km to the west, have island arc © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 307 geochemical signatures (Berry et al. 2016). Based on the close similarity in age, rock type, and 308 deformation style between the 492 Ma Lamoine Granite and volcanic and plutonic rocks in the Annidale 309 and St. Croix belts, we suggest the Lamoine Granite was erupted in a supra-subduction zone setting (Fig. 310 9) superimposed on the older oceanic rift setting inferred by Schulz et al. (2008). A progression of 311 younger ages to the west is consistent with slab rollback in that direction, which has been proposed for 312 Penobscot arc magmatism in Newfoundland (Zagorevski et al. 2010). 313 Post-Furongian deformation documented in the Ellsworth belt may be equivalent to Early 314 Ordovician regional deformation, referred to as Penobscottian, elsewhere in the orogen. In the central 315 Newfoundland type area of Ganderia, a major tectonic event during the Tremadocian–Floian is 316 characterized by penetrative deformation and low-grade metamorphism in a high-level fold-and-thrust 317 belt associated with ophiolite obduction onto the Gander margin and closure of the Penobscot back-arc 318 basin (Williams and Piasecki 1990; Zagorevski and van Staal 2011). Polarity of structures related to 319 Penobscottian orogenesis in Newfoundland (van Staal and Barr 2012) is generally assumed to be 320 southeast-directed. The 474 +6/−3 Ma Partridgeberry Hills Granite (Colman-Sadd et al. 1992) postdates 321 Early Ordovician obduction of Penobscot oceanic crust, stitches the Coy Pond ophiolite complex on the 322 Ganderian continental margin, and indicates that Penobscottian obduction and deformation was complete 323 by the Floian. 324 A minimum age for northwest-vergent deformation in New Brunswick is constrained by the 479 325 Ma Stewarton Gabbro, which stitches the terrane boundary between the Annidale belt and southeasterly 326 New River belt. This post-490/pre-479 Ma deformation is referred to as the Penobscot Orogeny (Fyffe et 327 al. 2011). No Penobscot stitching plutons have been identified in the Penobscot Bay inlier, however, 328 based on comparison with New Brunswick, we consider it most likely that Ellsworth D2 deformation is 329 Penobscottian. We also stress that it is not currently possible to rule out a younger maximum age for D2 330 deformation based on similar northwest-vergent structures of Late Ordovician–Silurian age present in the 331 St. Croix belt (West et al. 1995). But D2 is unlikely to be Acadian, as D2 structures are pre-Ludlow and 332 probably pre-Wenlock. 333 Two mechanisms have been proposed to explain the Penobscot event. Zagorevski et al. (2010) 334 invoked a collision between the west-facing Penobscot arc and a seamount. Waldron et al. (2015b) 335 invoked collision between a west-facing Penobscot arc, which originated east of Gondwana, and first a 336 Cayman-trough-like ophiolite (Ellsworth) then an east-facing promontory of Gondwana (St. Croix). 337 These end member scenarios are currently both viable, and their further evaluation constitutes a top 338 priority in Appalachian tectonics. We suggest a variation on the Zagorevski et al. (2010) scenario in 339 which, rather than a seamount, the west-facing arc collided with the main Iapetus spreading center. Such a 340 ridge-arc collision must have occurred along the periphery of Gondwana, and it would explain the © The Author(s) or their Institution(s) Page 10 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 11 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 341 observed sequence of Miaolingian rifting, Furongian arc and back-arc magmatism, Early Ordovician 342 northwest-vergent deformation, syn/post-collision gabbroic plutonism, and renewed Middle Ordovician 343 arc and back arc magmatism. 344 345 CONCLUSIONS 346 This U–Pb geochronological study of deformed granite from the Ellsworth belt in coastal Maine 347 indicates that the deformed leucocratic granite exposed at Lamoine Beach crystallized at 492 ± 1.7 Ma. 348 This age is the first unequivocal evidence for a Furongian intrusive event in the Ellsworth belt and 349 precludes the Lamoine Granite from representing basement to the Ellsworth Schist. The schistosity in the 350 granite is parallel to main fabric in the enclosing schist and provides a maximum estimate for age of 351 regional deformation and associated metamorphic overprint. We attribute the main deformation to 352 thrusting of the Ellsworth belt over the St. Croix belt adjacent to the northwest. Kinematic indicators 353 indicate a top-to-northwest sense of shear that resulted from progressive horizontal shortening, causing 354 crustal thickening and peak greenschist-facies metamorphism. The age of this orogenic event is 355 constrained to be younger than 492 Ma. 356 A Furongian age for the Lamoine Granite requires that the unconformity between the Ellsworth 357 Schist and Castine Volcanics predates the regional D2 deformation, and is therefore unrelated to 358 juxtaposition of the Ellsworth and St. Croix belts. Polarities of structures, degree of metamorphism, and 359 style of plutonism of the Ellsworth belt resemble Cambrian–Ordovician rocks and structures in the 360 Gander domain in New England and Atlantic Canada. Specifically, the Lamoine Granite correlates with 361 the Cameron Road Granite in the Annidale belt of New Brunswick which suggests that both are products 362 of subduction-related magmatism in the Penobscot arc and back-arc. Deformation in the Ellsworth belt 363 has similarities with the Penobscot Orogeny in New Brunswick. A ridge-arc collision model explains 364 Ellsworth, St. Croix, and Annidale belt relationships by relating structural styles, metamorphism, and 365 plutonism to collision between a west-facing Penobscot arc and the main spreading centre in the Iapetus 366 Ocean. 367 368 369 ACKNOWLEDGMENTS We thank Sherri Strong for assistance with sample preparation and her exceptional U–Pb 370 chemistry and mass spectrometry analysis. Thanks are extended to Henry Berry IV and Dave Stewart 371 (1928–2015) for support and sharing their knowledge of the Ellsworth area during memorable field 372 excursions. We greatly appreciate stimulating discussions with Jim Hibbard, who generously provided 373 information from his work in the area and for demonstrating the early deformation history of the © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 374 Ellsworth Schist. JCP is indebted to Bob Marvinney for the invitation and opportunity to work in Maine. 375 Helpful and thorough reviews by Susan Johnson and Ian Honsberger improved the manuscript. 376 377 REFERENCES 378 Berry, W.B.N. and Boucot, A.J. 1970. Correlation of the North American Silurian rocks: GSA Special 379 Paper, 102: 289. 380 Berry, H.N., West, D.P., and Burke, W.B. 2016. 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Geology, 44: 455–458. 419 McGregor, J., 1964, Geology of the Ellsworth quadrangle and vicinity, Maine: Ph.D. dissertation, 420 University of Illinois. 421 Ludwig, K.R. 2012. User's Manual for Isoplot Version 3.75–4.15: A Geochronological Toolkit for 422 Microsoft Excel Berkeley Geochronological Center Special Publication, 5. 423 McLeod, M.J., Ruitenberg, A.A., and Krogh, T.E. 1992. Geology and U–Pb geochronology of the 424 Annidale Group, southern New Brunswick: Lower Ordovician volcanic and sedimentary rocks formed 425 near the southeastern margin of Iapetus Ocean. Atlantic Geology, 28: 181–192. 426 Osberg, P.H. and Berry, H.N. 2020. Bedrock geology of the Camden quadrangle, Maine: Maine 427 Geological Survey, Open-File Map 20-8, 2 map plates, scale 1:24,000. Maine Geological Survey Maps. 428 2125. 429 Pollock, J.C. 2008. Bedrock geology of the Ellsworth Quadrangle, Maine. Department of Conservation, 430 Maine Geological Survey, Open-File Map 08-88, scale 1:24000. 431 Pollock J.C., Hibbard, J.P., and van Staal C.R. 2012. A paleogeographical review of the peri-Gondwanan 432 realm of the Appalachian orogen. Canadian Journal of Earth Sciences. 49: 259–288. 433 https://doi.org/10.1139/e11-049 434 Reusch, D.N., Holm-Denoma, C.S., and Slack, J.F. 2018. U–Pb zircon geochronology of Proterozoic and 435 Paleozoic rocks, North Islesboro, coastal Maine (USA): links to West Africa and Penobscottian 436 orogenesis in southeastern Ganderia? Atlantic Geology, 54: 189–221. 10.4138/atlgeol.2018.007 437 Reusch, D.N. 2003a. Bedrock Geology of the Mainland Portion of the Newbury Neck and Salsbury Cove 438 7.5-Minute Quadrangles: Department of Conservation, Maine Geological Survey Open-File 03–92, 14 p. © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 439 Reusch, D.N. 2003b. Bedrock Geology of the Salsbury Cove Quadrangle, Maine. Department of 440 Conservation, Maine Geological Survey Open-File Map 03–91, scale 1:24,000. 441 Reusch, D.N., and Hogan, J.P. 2002. Bedrock geology of the Newbury Neck quadrangle, Maine: Maine 442 Geological Survey, Open-File Map 02-162, scale 1:24000. 443 Rogers, N., van Staal, C.R., McNicoll, V., Pollock, J., Zagorevski, A., and Whalen, J. 2006. 444 Neoproterozoic and Cambrian arc magmatism along the eastern margin of the Victoria Lake Supergroup: 445 A remnant of Ganderian basement in central Newfoundland? Precambrian Research, 147: 320–341, 446 10.1016/j.precamres.2006.01.025. 447 Ruitenberg, A.A., McLeod, M.J., and Krogh, T.E. 1993. 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Description of the Penobscot Bay quadrangle, Maine. 457 U.S. Geological Survey Geologic Atlas, Folio 149, 14 p., scale 1:125000. 458 Stacey, J.S. and Kramers, J.D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage 459 model. Earth and Planetary Science Letters, 26, 207–221. 10.1016/0012-821X(75)90088-6. 460 Stewart, D.B. 1998. Geology of northern Penobscot Bay, Maine: U.S. Geological Survey, Micellaneous 461 Investigation Series, Map I- 2551, map scale 1:62,500. 462 Stewart, D.B., Unger, J.D., and Hutchinson, D.R. 1995. Silurian tectonic history of Penobscot Bay region, 463 Maine Atlantic Geology, 31: 67–79. 464 Stewart, D.B. and Wones, D. R. 1974, Bedrock geology of northern Penobscot Bay area, in Osberg, P. H. 465 (editor), Guidebook for field trips in east-central and north-central Maine: New England Intercollegiate 466 Geological Conference, 66th Annual Meeting, Orono, Maine: 223–239. 467 Tucker, R.D., Osberg, P.H., and Berry, H.N., IV. 2001. The geology of part of Acadia and the nature of 468 the Acadian Orogeny across central and eastern Maine. American Journal of Science, 301, 205–260. 469 10.2475/ajs.301.3.205 470 van Staal, C.R. and Barr, S.M. 2012. Lithospheric architecture and tectonic evolution of the Canadian 471 Appalachians. In Tectonic Styles in Canada Revisited: the LITHOPROBE perspective. Edited by J.A. 472 Percival, F.A. Cook and R.M. Clowes. Geological Association of Canada, Special Paper 49: 41–95. © The Author(s) or their Institution(s) Page 14 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 15 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) 473 van Staal, C.R., Barr, S.M., and Murphy, J.B. 2012. Provenance and tectonic evolution of Ganderia: 474 Constraints on the evolution of the Iapetus and Rheic oceans. Geology, 40: 987–990. 10.1130/G33302.1. 475 van Staal, C.R., Whalen, J.B., Valverde-Vaquero, P., Zagorevski, A., and Rogers, N. 2009. Pre- 476 Carboniferous, episodic accretion-related, orogenesis along the Laurentian margin of the northern 477 Appalachians. In Ancient orogens and modern analogues. Edited by J.B. Murphy, J.D. Keppie, and A.J. 478 Hynes. Geological Society of London, Special Publications, 327: 271–316. 479 Waldron, J.W.F., Barr, S.M., Park, A.F., White, C.E., and Hibbard, J.P. 2015a. Late Paleozoic strike-slip 480 faults in Maritime Canada and their role in the reconfiguration of the northern Appalachian orogen. 481 Tectonics, 34: 1–24. 10.1002/2015TC003882. 482 Waldron, J.W.F., Schofield, D.I., and Reusch, D.N. 2015b. Arc-microcontinent interaction in the early 483 history of the Iapetus Ocean. 2015. In Abstracts with Programs, Geological Society of America Annual 484 Meeting, Baltimore, Maryland, USA, 47(7): 861. 485 West D.P. Jr., Guidotti C.V., and Lux D.R. 1995. Silurian orogenesis in the western Penobscot Bay 486 region, Maine. Canadian Journal of Earth Sciences, 32(11): 1845–1858. 487 Williams, H. and Piasecki, M.A.J. 1990. The Cold Spring Melange and a possible model for Dunnage– 488 Gander zone interaction in central Newfoundland. Canadian Journal of Earth Sciences, 27: 1126–1134. 489 Zagorevski, A., van Staal, C.R., Rogers, N., McNicoll, V J., and Pollock, J. 2010. Middle Cambrian to 490 Ordovician arc-back arc development on the leading edge of Ganderia, Newfoundland Appalachians. In 491 From Rodinia to Pangea: The lithotectonic record of the Appalachian region. Edited by R.P. Tollo, M.J. 492 Bartholomew, J.P. Hibbard, and P.M. Karabinos. Geological Society of America Memoir, 206: 1–30. 493 Zagorevski, A. and van Staal, C.R. 2011. The Record of Ordovician Arc–Arc and Arc–Continent 494 Collisions in the Canadian Appalachians During the Closure of Iapetus. In Arc-Continent Collision, 495 Frontiers in Earth Sciences. Edited by D. Brown and P.D. Ryan, 341–371. 10.1007/978-3-540-88558- 496 0_12. 497 498 Figure 1. Geology of the Penobscot Bay inlier. Abbreviations, DI: Deer Island; FB: Frenchman Bay; 499 NHI: North Haven Island; THF: Turtle Head Fault. Base map from Hibbard et al. (2006) 500 Figure 2. Simplified geological map of the Mount Desert Narrows area, Maine. Base map from Reusch 501 (2003a). 502 Figure 3. Representative photos of outcrop field relationships: (A) Deformed medium-grained granite 503 that contains L2 lineation, indicating that its emplacement pre-dated the D2 deformation; (B) Lamoine 504 Granite selected for U–Pb analysis that contains the penetrative S2 foliation parallel to the host Ellsworth 505 Schist; (C) Foliated (S2) muscovite-chlorite schist; (D) Conglomerate bed at the base of the Castine © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) 506 Volcanics that contains pebbles of vein quartz and a cobble of strained green silicic metamorphic rock 507 similar to the underlying Ellsworth Schist implying a basal angular unconformity. 508 Figure 4. Representative structures displaying top-to-northwest sense-of-shear within albite-quartz- 509 chlorite-muscovite rocks of the Ellsworth Schist, Newbury Neck and Ellsworth quadrangles: (A) S–C 510 shear bands (penny for scale); (B) Asymmetrically deformed quartz vein (pen for scale); (C) 511 Asymmetrically folded quartz veins (notebook for scale); (D) S–C shear bands (chl: chorite, alb: albite); 512 (E) mica fish; (F) Asymmetrically boudinaged quartz vein. 513 Figure 5. Equal-area lower-hemisphere projection of bedding (n=81, blue, contour interval [CI]=5%); S2 514 foliation (n=201, red, CI=5%); L2 lineations (N=86; green; CI=10%). Individual D2 fold hinges (●, n=56), 515 lie along a best-fit great circle (021/20), the pole (Pf=70o→291) to which is coaxial to the pole to 516 foliation. Although S2 was refolded during D3 (Acadian Orogeny), L2 stretching lineations display the 517 preferred northwest-southeast orientation. 518 Figure 6. Representative photomicrograph of zircons separated from the least magnetic fraction. 519 Figure 7. U–Pb ages and Concordia diagram for Lamoine Granite. 520 Figure 8. Tectonostratigraphic evolution of the Ganderian margin of the Appalachian orogen in Maine, 521 New Brunswick, and Newfoundland. Modified from van Staal and Barr (2012). Ages of units are U–Pb 522 zircon and cited in the text; and from Dunning et al. (1990) and Colman-Sadd et al. (1992). Abbreviation, 523 CRG: Cameron Road Granite 524 Figure 9. Schematic Early Palaeozoic evolution of Ganderia. (A) Oldest part of the Penobscot arc is ca. 525 514 Ma. Ellsworth bimodal volcanic rocks and serpentinized mantle suggest departure of Ganderia from 526 Amazonia in Miaolingian (509–504 Ma). (B) Continued extension of Penobscot arc, presumably due to 527 slab rollback, opens the back-arc (e.g., ophiolite in Newfoundland); Lamoine Granite intruded in the 528 back-arc; increasing buoyancy of eastern Iapetan lithosphere suggests mechanism for decrease in dip 529 angle. (C) Mid-Iapetan ridge collides with Penobscot arc, closing the back arc basin affording a 530 mechanism for top-to-northwest sense of shear and subsequent intrusion of mafic stitching plutons (e.g., 531 Stewarton Gabbro). Upper plate regime becomes extensional again post-ridge collision as the relative 532 plate velocity decreases. 533 Table 1. U–Pb data for Lamoine Granite. © The Author(s) or their Institution(s) Page 16 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 17 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 1 70oW 0 30 69oW Augusta Bangor km 44 o N Norumbega Fault P Hack ma ta on 68oW 45 o N Fault Zone d k Ca sti ne THF Ellsworth Camden o or b les Casco Bay Fig. 2 Is scot Bay nob NHI Pe DI FB Machias Mt. Desert Island Gulf of Maine Laurentia Laurentian margin Penobscot Peri-Gondwana Peri-Gondwanan arcs Ganderia Peri-Laurentian arcs Avalonia Meguma Annidale belt Exploits subzone Bay inlier Devonian and younger Clastic sedimentary rocks Plutonic rocks Silurian Plutonic rocks (felsic/mafic) Central Maine trough Ordovician and older Liberty-Orrington belt (volcanic/sedimentary) Coastal Volcanic belt St. Croix belt Fredericton Trough Ellsworth belt © The Author(s) or their Institution(s) Page 18 of 26 Figure 2 r Rive 30 ing er n Riv 30 Unio n Marlboro rd a 5 Jo 5 er 30 Riv 20 50 s East Surry 44°30’ ill 20 25 N 20 Lamoine Corner 25 Raccoon C ove Bayside U n ion Ber r y C ove Lamoine Beach 25 25 10 River D Trenton ert Eas ter n Bay Uz 492±1.7 Ma 25 Sand Point 10 Thomas I. ou nt West Trenton es 30 50 N a r ro w s 40 Ba y M 35 G oos e Cove 20 T ho m as Bay 10 Salsbury Cove Hulls Cove 40 Alley Island 30 35 B ay Red Rock Corner 30 68°27’30’’ Oak Point W 0 e r ste N or th w es t n 1 Cove MOUNT DESERT ISLAND Green Island Indian Point km 45 44°22’30’’ LEGEND DEVONIAN? Gabbro and granite, undivided SILURIAN Bar Harbor Formation Siltstone and sandstone SILURIAN-DEVONIAN Massive rhyolite Cadillac Mtn. Intrusive Suite CAMBRIAN Ellsworth Schist Muscovite-chlorite schist Egypt member: volcanogenic feldspathic schist CAMBRIAN Lamoine granite Medium-grained granite Rhyolite of Goose Cove Gabbro-diorite 45 Lineation related to foliation .......................... Granitoid rocks, undivided Foliation (inclined) ......................................... Geological boundary (approximate) ............................ 50 Antiform ......................................................... Bedding, tops known (inclined) ................................... 70 Primary igneous layering (inclined) ............................. 45 Fault (approximate) ....................................... U–Pb age (zircon).......................................... © The Author(s) or their Institution(s) Uz 68°15’ 25 Sk Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 19 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 3 A C NW B L2 SE D © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) A NW S SE C F2 NW NW SE E NW NW 500 μm © The Author(s) or their Institution(s) Page 20 of 26 Figure 4 B C NW SE D chl C S alb SE 500 μm F SE C S SE 500 μm Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 5 N 0 30 33 30 20 plane 35 3 fold 15 ge s 40 10 12 0 0 2 21 0 S © The Author(s) or their Institution(s) Poles to foliation (S2) 15 hi n 10 5 Per cent per 1% area E D2 20 Pf W 10 Per cent per 1% area of 30 25 Lineation (L2) 60 0 Poles to bedding 15 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 21 of 26 5 Per cent per 1% area Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 6 200 μm © The Author(s) or their Institution(s) Page 22 of 26 Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 23 of 26 Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 7 LAMOINE GRANITE 0.0815 0.0805 0.0785 505 238 206 Pb U 0.0795 485 0.612 495 500 490 Z2 0.0775 Z1 0.62 Z3 492 +/-1.7 Ma 207 235 U Pb 0.628 0.636 0.644 © The Author(s) or their Institution(s) AMES KNOB FM DAPINGIAN FLOIAN 477 472±2 Ma 497 MIAOLINGIAN 509 SERIES 2 CLAM COVE FAULT FURONGIAN LONDON 492±1.7 Ma ? TREMADOCIAN 485 479±2 Ma ca. 490–487 Ma PENOBSCOT FM GUSHEE SETTLEMENT FM STEWARTON GB ? 487±3 Ma 477.6±1.8 Ma ESS FM LAWSON LAMOINE GR CRG O’NEILL BROOK BROOK FM CARPENTER BROOK FM SCHIST CASTINE VOL 503.5±2.5 Ma 490±2 Ma 493±2 Ma ELLSWORTH SCHIST RED INDIAN LINE DARRIWILLIAN 467 F HILL FM TURTLE HEAD FAULT SANDBIAN BENNER COOKSON GP 458 KATIAN ORDOVICIAN HIRNANTIAN DAVIDSVILLE GP BADGER GP 443 453 INDIAN ISLANDS GP 422.3±1.2 Ma F PIPESTONE POND 494 +2.5 -1.9 Ma RIFTING 509±1 Ma 508.6±0.8 Ma EDIACARAN ROCKPORT GP TERRENEUVIAN 541 563±2 Ma GANDER BASEMENT ? 565±2 Ma CRIPPLEBACK LAKE Deformation with sense of transport direction Continental Volcanic Arc &/or Backarc Oceanic Volcanic Arc &/or Backarc Terrestrial to Shallow Marine Siliciclastic & Volcanic rocks Marine Sandstone, Shale, & Conglomerate Varicoloured Shale, Chert, &/or limestone Melange Oceanic rift Sandstone & Conglomerate Crystalline Basement Sandstone &/or Shale SSZ Ophiolite or Infant Arc F © The Author(s) or their Institution(s) Fossil locality Mafic to Felsic Intrusive rocks U–Pb age SALINIC OROGENY 424±2 Ma GANDER GP LLANDOVERY YOUNGTOWN DOG BAY LINE WENLOCK BOTWOOD GP CADILLAC MTN 420±2 Ma Gander margin Gander arcs PENOBSCOT ARC 433 PŘÍDOLÍ LUDLOW SE Newfoundland Annidale Ellsworth St. Croix SILURIAN 423 427 New Brunswick Maine Age (Ma) Page 24 of 26 PENOBSCOT OBDUCTION NW C A M B R I A N Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 al use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version Figure 8 Canadian Journal of Earth Sciences (Author Accepted Manuscript) Figure 9 Canadian Journal of Earth Sciences (Author Accepted Manuscript) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record. Page 25 of 26 NW SE A) 514–500 Ma GANDERIA Iapetus Ocean Ellsworth rift Penobscot arc Amazonia B) 500–487 Ma GANDERIA Iapetus Ocean Penobscot arc Penobscot back arc Lamoine Granite Rheic Ocean Amazonia Iapetus Ocean Popelogan arc Penobscot suture C) 486–475 Ma New River Elmtree peri-Laurentia © The Author(s) or their Institution(s) Can. J. Earth Sci. Downloaded from cdnsciencepub.com by Mount Royal University on 10/18/21 use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official versio Canadian Journal of Earth Sciences (Author Accepted Manuscript) Page 26 of 26 Table 1. U-Pb data for the Lamoine Granite JP41407: UTM (19N 0555854, 4921932 NAD 27) Fraction Z1 5 sml equant clr Z2 5 sml equant clr Z3 4 sml equant clr Weight Concentration (μg) U (ppm) Pb rad (ppm) 0.007 0.007 0.006 135 66 92 11.9 6 8.2 Measured TCPb (pg) 206Pb/204Pb 1.1 1.1 0.93 4647 2359 2965 Corrected Atomic Ratios 208Pb/206Pb 206Pb/238U 0.2348 0.2612 0.2526 0.07904 0.07966 0.07927 Age (Ma) ± 207Pb/235U ± 207Pb/206Pb ± 206Pb/238U 207Pb/235U 207Pb/206Pb 68 78 36 0.6243 0.6266 0.6232 46 60 32 0.05729 0.05705 0.05702 32 38 20 490.4 ± 4.0 494.1 ± 4.6 491.8 ± 2.1 Notes: Z=zircon, sml=small, clr=clear, All zircons were abraded (cf. Krogh, 1982). pg=picogram, mg=milligram. * atomic ratios corrected for fractionation, spike, laboratory blank of 1 pg of common lead at the age of the sample calculated from the model of Stacey and Kramers (1975), and 1 pg U blank. Two sigma uncertainties calculated with an unpublished error propagation procedure are reported after the ratios and refer to the final digits. © The Author(s) or their Institution(s) 493 494 492 503 493 492