1 The Canaan River pluton is located on Canaan River and in the surrounding area, about 40 km west of Moncton in southeastern New Brunswick (Fig. 1). Hamilton (1962) was the first to describe the megacrystic granite on Canaan River west of Moncton (Fig. 1), but since then very little work has been done. Whalen et al. (1986) named the granite the Canaan River pluton and sampled it as part of a larger isotopic and geochemical study. More detailed mapping of the Paleozoic inliers and surrounding Carboniferous rocks was conducted by St. Peter and Johnson (2006; 2008) and John-son and St. Peter (2008), but the pluton has never been formally named.

2 The Canaan River area is largely underlain by flat-lying Pennsylvanian sandstone that is part of the Carboniferous New Brunswick Platform of Poole (1967), an area of uplifted Early Paleozoic basement within the larger Late Devonian to Lower Permian Maritimes Basin of Atlantic Canada (Roliff 1962; Bradley 1982; Gibling et al. 2008). The platform covers an area of over 25 000 km² and forms the roughly tri angular area of Pennsylvanian Pictou Group that is exposed at surface over much of the eastern part of the province. The Pictou Group either disconformably overlies Mississippian red beds and peralkaline volcanic rocks or lies directly on pre-Carboniferous basement, as is the case with the Canaan River pluton (Ball et al. 1981; Fyffe and Barr 1986; Gray et al. 2010).

3 Pre-Carboniferous inliers are restricted to the southern parts of the platform between Chipman and Canaan River near the boundary between the New Brunswick Platform and the Cocagne Subbasin (Fig. 1). In addition to granite, thick turbidite sequences belonging to the Silurian Kings-clear Group of the Fredericton belt (e.g., Fyffe et al. 2011) and minor diorite are also exposed. These inliers are the surface expression of a shallow-buried basement high referred to as the “Minto-Chipman/Canaan River basement high”, which was delineated by a series of shallow boreholes that were drilled during a study to determine the coal potential of the Pennsylvanian rocks (Ball et al. 1981). Twelve of the boreholes that were drilled in the Chipman and Canaan River areas intersected granodiorite, slate, phyllite, and schist at depths of less than 122 m beneath the Pennsylvanian cover. The distribution of the boreholes that intersected pre-Carboniferous rocks indicated that the boundaries of the basement high are in part controlled by parallel, northwest-trending faults, suggesting a horst-like structure (Ball et al. 1981). A regional aeromagnetic survey subsequently revealed prominent, parallel, northwest-trending linear magnetic highs, one of which appears to mark the western boundary of the predicted basement horst (Kiss et al. 2004a, 2004b, 2004c). These positive linear magnetic features were interpreted to be mafic dykes intruded into northwest-trending structures, possible feeders to Mississippian volcanic rocks present west of the Canaan River area (Thomas and Kiss 2005). Subsequent mapping has shown that in most cases the bedrock at surface directly over the linear magnetic anomalies is part of the Pictou Group, thus indicating that the dykes are at least in part buried at shallow depths beneath the sandstone cover (St. Peter and Johnson 2006; Johnson and St. Peter 2008). One exception is on Coal Creek (Fig. 1), where a less prominent, northwest-trending linear magnetic anomaly oblique to the main trend of interpreted dykes is related to a lamprophyre dyke in the Flume Ridge Formation of the Kingsclear Group (St. Peter and Johnson 2008).

4 The boundary between the New Brunswick Platform and the Cocagne Subbasin to the southeast (Gussow 1953; St. Peter and Johnson 2009) is the northeast-striking Belleisle Fault (Fig. 1). In southwestern New Brunswick where Carboniferous cover is lacking, the Belleisle Fault separates Neoproterozoic and Early Paleozoic rocks of the New River, St. Croix, and Annidale belts and Silurian rocks of the Mascarene and Fredericton belts to the west, from the Early Silurian Kingston belt on the east (Barr et al. 2002; White et al. 2006; Fyffe et al 2011). Immediately west of the Belleisle Fault, the Neoproterozoic and younger rocks are intruded by Late Silurian to Late Devonian granitic to gabbroic plutons of the Saint George Batholith, and even farther west by the Pokiok Batholith (Fig. 1).

5 The purpose of this paper is to present a U–Pb (zircon) age for a sample of megacrystic granite collected from the Canaan River pluton on Thornes Brook (Fig. 2) and to compare its chemical characteristics to plutons of similar age in southern New Brunswick.

15 Four samples of megacrystic monzogranite and two samples of diorite were selected from the Canaan River pluton for whole-rock chemical analysis (Table 1). All samples were analyzed for major and trace elements, and three of the samples (two of monzogranite and one of diorite) also for rare-earth elements. Analyses for one additional sample of megacrystic granite (P9-WXNB353) from Whalen et al. (1996) were also utilized. To facilitate discussion of the geochemistry, analyses for granites of similar Lower Devonian (upper Lochkovian) age in the Saint George Batholith (John Lee Brook and Wellington Lake plutons) and Pokiok Batholith (Hawkshaw Granite) were plotted on the geochemical diagrams for comparison. The analyses for the John Lee Brook Granite include samples 85MM154B, 7f1/87 and 7g76/87 from McLeod (1990) and P8-WXNB350 from Whalen et al. (1996). The one set of analyses from the Wellington Lake Granite (sample 15-72) is from Mohammadi et al. (2017). The set of twelve analyses for the Hawkshaw Granite are from Whalen (1993).

16 The five monzogranite samples from the Canaan River pluton range in SiO₂ content between 67% and 70%, and the two quartz diorite samples have 55% and 59% SiO₂ (Table 1). Based on major-element components, the felsic rocks vary from granite to quartz monzonite and granodiorite; the Canaan River dioritic samples are quartz monzodiorite (Fig. 6a). The Canaan River and all of the other upper Lochkovian age granite samples plot in the high-K field on the silica versus K ₂ O diagram with the exception of the shoshonitic Wellington Lake Granite (Mohammadi et al. 2017) (Fig. 6b). On the aluminum saturation index (ASI) diagram, the Canaan River monzogranite samples plot in and near the field defined by chemical data from twelve samples of the Hawkshaw Granite from Whalen (1993), although the former samples are slightly more peraluminous (Fig. 6c). The Canaan River samples plot near the upper limit (<1.1) for I-type granite and transitional to S-type granite (Chappell and White 1974, 2001), which is similar to the S-type John Lee Brook Granite, although the latter is slightly more alkaline (Fig. 6c).

17 Both the felsic and mafic components of the Canaan River pluton exhibit similar rare-earth element (REE) patterns, with enrichment in light REE, small negative Eu anomalies, and relatively flat but slightly decreasing heavy REE profile (Fig.7a). The overall abundance of REE decreases with increasing SiO ₂ content in the samples and is highest in the quartz diorite sample (~55% SiO ₂ ) and lowest in the mon zogranite sample 07SJ-184a (~70% SiO ₂ ), consistent with fractionation of REE-bearing minerals such as apatite and zircon. The quartz diorite also has slightly lower abundances of most large-ion-lithophile elements (LILE), with the exceptions of Sr and Eu (Fig. 7b), consistent with differentiation and fractional crystallization of plagioclase. The Hawkshaw Granite samples show nearly identical trace element patterns, although with lower Ba (Fig. 7b). The John Lee Brook and Wellington Lake granites are also enriched in light REE relative to heavy REE but have much larger negative Eu anomalies than the Canaan River and Hawkshaw (Figs. 7a, c). The single Wellington Lake sample also has the highest absolute abundances of REE consistent with its A-type chemistry (Mohammadi et al. 2017). In contrast to all of the other samples the majority of John Lee Brook samples are enriched in the heaviest REE (Fig. 7c). The Canaan River, Hawkshaw, and John Lee Brook samples all have negative Nb and Ti anomalies, suggesting a subduction component or assimilation of an upper crustal material (Figs. 7b, d) consistent with the positions of most of the samples in the overlapping volcanic-arc and post-collisional granite fields (Fig. 8a) and in the field for slab failure plutons (Fig. 8b) on tectonic setting discrimination diagrams. Some of the Hawkshaw samples plot toward the within-plate granite field, as does the single Wellington Lake sample, but the latter has significantly higher Y (Fig. 8b).

18 The Canaan River monzogranite samples plot in or near the boundary of the combined field of I- and S- granites on diagrams that distinguish those granite types from A-type granitoids but near the upper limit in all of Ga/Al ratio and alkali element oxide and Zr contents (Figs. 9a, b). However, they do not show characteristics of evolved I- and S-type granites (Figs. 9c, d). The Hawkshaw granite dataset overlaps the Canaan River samples on diagrams utilizing Ga/Al ratio and alkali element oxide and Zr contents to distinguish I- and S-type granites from A-type granites (Figs. 9a, b) and are similarly unevolved to slightly more evolved than the Canaan River samples (Figs. 9c, d). In contrast, the Wellington Lake granite plots clearly as A-type (Figs. 9a–d), as determined previously by Mohammadi et al. (2017) and the John Lee Brook near the boundary of I- and S-types (Figs. 9a, b), but clearly in the fractionated granite field (Figs. 9c, d).

19 Mohammadi et al. (2017) observed that La/Yb and epsilon Nd values varied systematically across the Saint George Batholith from southeast to northwest and demonstrated that the Early Devonian plutons in the northwest have considerably higher La/Yb ratios and lower epsilon Nd values than the Late Silurian plutons in the southeast. The La/Yb values determined for the Canaan River pluton range from 12.3 to 17.3, and therefore are significantly lower than those of the younger megacrystic Jimmy Hill, Magaguadavic, and Gaytons granites, but are comparable to the John Lee Brook and Hawkshaw granites of similar age (Table 2). However, when comparing the epsilon Nd data, the intrusions in the Saint George Batholith are mostly isotopically positive, ranging from + 3.3 for the A-type Welsford Granite to slight-ly negative - 0.4 for the S-type Tower Hill pluton (Whalen et al. 1994, 1996). In contrast, both the Canaan River and Hawkshaw granites have relatively high isotopically negative epsilon Nd values of - 2.0 and - 2.5, respectively, indicating that melting of surpracrustal material was involved in the generation of both of these granites (Whalen et al. 1996).

20 Late Silurian to Late Devonian intrusions are abundant in all lithotectonic belts northwest of the Belleisle Fault in southern and central New Brunswick (Figs. 1, 10). In contrast, the only known plutons of this age in Ganderian belts southeast of this fault are the ca. 390 Ma Gaytons Granite and similar granite intersected at depth in several boreholes on the buried Westmorland uplift (Barr et al. 2007; St. Peter and Johnson 2009). Devonian megacrystic varieties like that on Canaan River occur only in the Gaytons Granite, the Magaguadavic and Jimmy Hill granites in the Saint George Batholith and the Hawkshaw Granite in the Pokiok Batholith. The Gaytons Granite is composed main-ly of megacrystic quartz monzonite that yielded a Middle Devonian U–Pb (zircon) age of 390 ± 0.5 Ma (Barr et al. 2007), so is significantly younger than the 412.3 ± 2.6 Ma age determined for the Canaan River pluton. The host rocks of the Gaytons Granite are not exposed but the intrusion is chemically and mineralogically identical to and the same age as quartz monzonite drilled beneath Carboniferous strata south of Moncton and associated with buried anorthosite and ferronorite of the Lower Coverdale plutonic suite (White 1996; Barr et al. 2007; Tesfai 2011; Miller et al. 2018). It is unlikely that the Canaan River pluton is related to the Middle Devonian A-type Gaytons Granite (Barr et al. 2007). Indeed, documentation of many tens of kms of post-Devonian movement on the Belleisle Fault (Waldron et al. 2015) make any links between the Gaytons and Canaan Riv-er plutons unlikely.

21 The Saint George Batholith west of the Belleisle Fault (McLeod 1990; Mohammadi et al. 2017) is divided into three main groups based on age and petrogenetic characteristics: (1) Late Silurian bimodal A-type plutons (Bocabec, Utopia, Jake Lee, Welsford and Wellington Lake); (2) Early Devonian I – and S –type felsic intrusions (Magaguadavic, Jimmy Hill, John Lee Brook and Tower Hill), and (3) a much younger suite of Late Devonian fractionated I– type intrusions (Mount Douglas and satellite plutons). The megacrystic Magaguadavic and Jimmy Hill granites are also younger than the granite on Canaan River, as they have Early Devonian (Emsian stage) U–Pb (zircon) ages of 396 ± 1 Ma (Bevier 1990) and 403± 2 Ma (Davis et al. 2004), respectively. The only granite in the Saint George Batholith similar in age to the Canaan River pluton are the garnetiferous, two-mica John Lee Brook Granite and the Wellington Lake biotite granite both of which have upper Lochkovian ages of 413.3 ± 1 Ma and 415.5 ± 2.1, respectively (Mohammadi et al. 2017), however as described above they are different compositionally and geochemically than the Canaan River pluton.

22 The Pokiok Batholith is situated about 50 km northwest of the Saint George Batholith, on the west side of the Fredericton Fault (Venugopal 1979; McCutcheon et al. 1981; Lutes 1987; Whalen 1993; and Yang et al. 2008) (Fig. 1). The batholith intruded rocks of the Fredericton belt on its southeastern side and Cambrian to Early Ordovician rocks of the Miramichi belt (van Staal and Fyffe 1991; Fyffe 2001) along its northwestern side. All of the plutons in the Pokiok Batholith are Early Devonian (Bevier and Whalen 1990a, 1990b; Mc-Leod et al. 2003; Beal et al. 2010) and have chemical characteristics typical of I-type granitoids (Whalen 1993; Yang et al. 2008). A U–Pb (titanite) age of 411 ± 2 Ma (Bevier and Whalen 1990a, 1990b) for the Hawkshaw Granite, and a 414 ± 2 Ma (U–Pb zircon) age for related granodiorite at depth in the Lake George area (McLeod et al. 2003; Leonard et al. 2006; Lentz et al. 2016) indicate that the Hawkshaw Granite is the only megacrystic granite in the region known to be similar in age to the Canaan River pluton. Despite having no radiometric age control and chemical data from only one sample, Whalen et al. (1996) noted the lithological and geochemical similarities between the Canaan River and Hawkshaw megacrystic granites and our dating and geochemical data presented above further support a link between these two granites.

23 The systematic changes in isotopic and geochemical characteristics observed across the Saint George Batholith by Mohammadi et al. (2017) are similar to those previously observed by Whalen et al. (2006) across a major suture zone in central Newfoundland. This led Mohammadi et al. (2017) to suggest that the changes were reflecting the position of these granites relative to the Acadian suture zone. The Belleisle Fault is a major structure that separates the Silurian Kings-ton arc and Mascarene backarc basin that formed above a northwest-directed subduction zone beneath the trailing edge of Ganderia (Fyffe et al. 1999, 2011; Barr et al. 2002). The older parts of the Saint George Batholith were emplaced following the arrival of Avalonia during the middle Silurian onset of the Acadian orogeny (Fyffe et al. 1999, 2009, 2011; Barr et al. 2002; van Staal et al. 2009; Mohammadi et al. 2017).

24 Whalen et al. (2006) attributed the changes in La/Yb and epsilon Nd values over time in Newfoundland, to slab break-off and the transition from shallow-level melting of juvenile crust adjacent to the suture zone to deeper-level melting of old granitic basement farther away in the backarc area. Mohammadi et al. (2017) invoked the same model to explain the shift from older bimodal, A-type magmatism to felsic I- and S-type magmatism in the Saint George Batholith, suggesting it reflected the change from an extensional tectonic regime in the Masacrene backarc basin to a transpressional environment related to the continued convergence of the Avalonian microplate and slab-break off closer to the telescoped boundary between the Fredericton Trough, St. Croix belt, and Mascarene backarc basin (Fyffe et al. 2011).

25 The Canaan River, Hawkshaw, and John Lee Brook granites all exhibit strong negative Nb and Ti anomalies typical of arc-related rocks. However, the arc-like signature could be inherited from upper crustal source rocks as all of these granites were emplaced into rocks of the Fredericton trough, interpreted as a foredeep basin formed during loading of the passive margin of the Tetagouche backarc basin by the overriding Brunswick subduction complex (van Staal et al. 2003). The signature may also be indicative of slab-breakoff during the Acadia orogeny, as postulated by Whalen et al. (2006).

26 The arrival of the leading edge of Ganderia at the Laurentian margin and subsequent inversion of the Fredericton Trough during the terminal Salinic orogeny coincided with the arrival of Avalonia at its trailing edge and the onset of the Acadian orogeny, resulting in a highly complex geodynamic setting (e.g., van Staal et al. 2009; van Staal and Barr 2012). The mechanism by which the Pokiok Batholith and other plutons in the Central Plutonic belt were generated has been ascribed to crustal thickening following Salinic orogenesis and/or underthrusting of Ganderia’s trailing edge by the leading edge of Avalonia (van Staal et al. 2009; Wilson and Kamo 2016). The Early Devonian units of the Pokiok Batholith (e.g., Hawkshaw) and Saint George Batholith (e.g., John Lee Brook), as well and the Canaan River pluton (Fig. 10) were emplaced immediately after these terranes and their Silurian cover were telescoped into an area less than 150 km wide due to orthogonal shortening (Mohammadi et al. 2017). The current position of the Canaan River pluton suggests that the older A-type, bimodal intrusions proximal to the Acadian suture were cut out along the Belleisle and other faults in the Canaan River area by regional-scale strike slip faulting (Fig. 1).

27 The Canaan River pluton was emplaced into rocks of the Fredericton trough during the Lochkovian stage of the Early Devonian. Although its current position immediately west of the Belleisle Fault appears to suggest that it is in a similar tectonostratigraphic position as the southern parts of the Saint George Batholith, the ages and isotopic and chemical characteristics of the latter intrusions are considerably different. Although the isolated location and limited exposures of the Canaan River pluton make regional correlations uncertain, its tectonostratigraphic setting, U–Pb age and geochemical data presented above indicate that the Canaan River pluton is more similar to units on the northwestern margin of the Saint George Batholith and especially the Hawkshaw Granite of the Pokiok Batholith, emplaced into sedimentary rocks of the Fredericton Trough. This interpretation indicates that the older A-type, bimodal intrusions proximal to the Acadian suture have been cut out along the Belleisle Fault in the Canaan River area by regional-scale strike slip faulting, thus explaining the termination of the Saint George Batholith and the whole Coastal Maine Magmatic Province.

28 The similarity of the Canaan River pluton to the Hawkshaw Granite also raises the possibility of the potential for the Canaan River pluton to host tungsten and/or intrusion-related gold - antimony mineralization, as studies on the Lake George Antimony deposit suggest that it is related to granodiorite that has been genetically linked to the Hawkshaw phase of the batholith (Seal et al. 1985; Lentz et al. 2002; Yang et al. 2002, 2008; Thorne and McLeod 2003; Thorne 2005).