The New Brunswick segment of the Canadian Appalachians contains a variety of gold deposits and occurrences that formed at different stages of the Appalachian orogeny. The Tobique-Chaleur Zone, situated in the northern part of New Brunswick, hosts several orogenic and epithermal gold mineralization systems that are spatially related to large-scale crustal faults or their subsidiary splays, such as the Rocky Brook-Millstream Fault. Although gold mineralization in northern New Brunswick is hosted by auriferous quartz veins, finding pathfinder elements, indicator minerals and alteration associated with gold mineralization remains challenging. Herein, the portable X-ray fluorescence (p-XRF; Olympus Vanta (TM)) spectrometer, in conjunction with micro-X-ray fluorescence (mu -XRF) energy dispersive spectrometry (EDS), was applied to selected core intervals from four gold systems in the region: the Williams Brook, McIntyre Brook, Mulligan Gulch and Simpson Field occurrences. We generated p-XRF-based multi-element datasets from selected intervals, then applied compositional data analysis, including principal component analysis (biplots) and cluster analysis, to interpret them. Although the p-XRF analysis and subsequent multivariate compositional data analysis provide geochemical patterns and highlight indicator elements associated with gold mineralization, the study also includes a comprehensive mineralogical analysis. The p-XRF geochemical data help the interpretation of the mineralogy, but the explicit mineralogical composition is confirmed through detailed petrographic and mu-XRF analyses. Gold-bearing minerals were further identified by mu -XRF-EDS analysis, revealing that gold is mainly associated with sulfide minerals, namely pyrite, chalcopyrite, pyrrhotite, stibnite and arsenopyrite. In addition to the above, our mineralogical studies further indicate that fine-grained muscovite and illite, produced by potassic and silicification alteration styles, are associated with gold-bearing quartz veins.

The Benjamin River South porphyry system (BRS) lies within the mid-Paleozoic Appalachian realm of Ganderia, representing an area of approximately 80 km(2) in northeastern New Brunswick. This region hosts the hypabyssal Blue Mountain Granodiorite Suite (BMGS) including BRS porphyries, which contains multiple, locally auriferous porphyry Cu-Mo occurrences associated with several cupolas ranging in size from 60 to similar to 600 m in diameter, situated northeast of the main Blue Mountain Granodiorite. These mineralized cupolas intrude into two Siluro-Devonian-aged volcano-sedimentary rock units (Benjamin and Bryant Point formations). The adjacent slightly older Benjamin River Intrusive Complex, dated at 418 +/- 1 Ma (U-Pb zircon), is cogenetic with the host regional rift-related bimodal volcano-sedimentary suite. The mineralized cupolas of the BRS porphyries (BMGS-BRS) were dated by U-Pb zircon (400.7 +/- 0.4 Ma); these Early Devonian intrusive tonalite-granodiorite phases (to andesitic textured), which host the mineralization are light cream to tan colored, plagioclase and hornblende-biotite porphyries within a variably f.g.- to m.g. hypidiomorphic granular quenched groundmass. In the samples with only very minor alteration-mineralization (<200 ppm Cu, <40 ppm Mo), the average Cu concentration is 69 ppm, whereas Mo averages 5 ppm, with an average of 0.35% S. Primary hydrothermal pyrite and chalcopyrite mineralization occur mostly as disseminations, with local pervasive replacement and also stockwork vein-style mineralization. This is associated with potassic alteration (+/- phyllic) in various proportions within the porphyries, and less commonly in the surrounding volcano-sedimentary bimodal sequence. Pervasive biotitization with K-feldspathization reflecting potassic alteration of pre-existing ferromagnesian phases and igneous feldspars are reflected by increases in K/Na, Fe, and S, along with copper and molybdenum in the lithogeochemical data. Later mineralization consists of base-metal-bearing pyritic veins that cut the pervasive disseminated mineralized zones. Molybdenite commonly occurs in quartz-bearing veins that cut across the primary mineralization. Weak, pervasive propylitic alteration overprints much of the primary mineralization-alteration, although some is controlled by veins. The BMGS suite ranges from diorite to granodiorite, plotting within the alkalic-calcic to calc-alkalic fields. Geochemically, they classify as magnesian granites, with FeOt/(FeOt+MgO) increasing only slightly with SiO2 content, reflecting their oxidized nature. The extremely low Zr (100-160 ppm) and Th (2-5 ppm), along with relatively low Ti and V (with Ti/V > 35), also suggest an oxidized calc-alkalic affinity with minimal crustal contamination. This is further supported by very low Zr/Y (average 22) and Th/Y (average 5.0), but higher Nb/Y (average 2.0), as well as high Sr/Y and La/Yb values, are due to very low Y and HREE, like those found in slab-derived adakitic systems related to late Acadian Orogeny slab failure. High T-P partial melting of hydrothermally altered oceanic slabs probably generates BMGS magmas enriched in H2O, SO2, HCl, and chalcophile metals that remain incompatible during fractionation at higher fO(2). In this region, these processes occur in a post-collisional setting during the initiation of slab failure, where upwelling asthenosphere supplies advective heat to enhance partial melting of slab and possibly suprasubduction mantle lithosphere. Late collisional transpression to transtension in the region due to oblique collision promote rapid ascent of the fertile BMGS melt through subduction-modified lithosphere into the upper crust. Interaction of oxidized slab melts with subduction-modified lithospheric mantle and juvenile volcano-plutonic crust in the region preserves oxidation, establishing conditions favorable for porphyry Cu-Au mineralization.

Titanite geochemistry is an effective petrogenetic and metallogenic indicator of Cu-Mo-Au mineralized magmatic systems. It forms in various geological environments, including igneous and low-medium grade metamorphic, and low-temperature hydrothermal veins. Titanite is a common accessory phase in oxidized I-type granitoid intrusions, occurring with quartz, plagioclase, K-feldspar, apatite, +/- hornblende, +/- biotite, and +/- titanomagnetite, and is enriched in a variety of trace elements including halogens. Variably mineralized (Cu, Mo, and Au, i.e. fertile) Devonian oxidized adakitic I-type granodiorites to granites from the New Brunswick part of the northern Appalachians with magmatic titanite from relatively fresh magmatic assemblages were examined. The compositional data reveal that these titanites are variably enriched in high field strength elements (Ta = 6.76-750.7 ppm, Zr = 44.48-6879.9 ppm, Hf = 2.62-173.1 ppm, Th = 7.95-931.5 ppm, U = 5.25-458.3 ppm), light to heavy rare earth elements, and Sr (1.59-447.8 ppm). These titanites exhibit notably negative Eu and Y anomalies and slightly positive Ce anomalies. Larger negative Eu anomalies of some of the titanites imply more reduced magmatic crystallization conditions, at least locally. Varying degrees of negative Eu anomalies imply variable fractionation in the source and of plagioclase from these magmas. Typically, these fertile granitoids have high magmatic fO2, which promotes the incorporation of Ce4+ into titanites, accounting for positive Ce anomalies. Zr-in-titanite thermometry indicates that crystallization temperatures of the investigated intrusions ranged from 737 degrees to 899 degrees C, reflecting variability in their formation conditions. Crystallization pressures using the Al2O3 content of titanite are estimated to be between 182 and 382 MPa. Titanite Sr isotopes record a progressive magmatic evolution from an early mantle-derived magma to later magmatic interaction during ascent through the crust. These magmas ascend and are emplaced in post-collisional settings following the break-off of a subducting oceanic slab and the onset of transtensional tectonics. Heat from upwelling asthenosphere entered the slab gap, raising temperatures and inducing melting of the oceanic crust and possibly partial thickened suprasubduction subcontinental lithospheric mantle. Like other fertile adakitic porphyries, these Devonian oxidized intermediate magmas formed during slab failure then ascended rapidly through the thickened lithosphere in response to the changed geodynamic regime during post-collisional tectonic reorganization and lithospheric weakening processes.

The Tobique-Chaleur Zone (TCZ), located in northern New Brunswick and the neighboring Gaspé Peninsula, hosts a number of gold occurrences. Gold mineralization in TCZ is spatially associated with large-scale crustal structures or their subsidiary splays (e.g., the Rocky Brook-Millstream Fault system). The gold occurrences in the Chaleur Bay Synclinorium, are hosted primarily underlain by Upper Silurian to Early Devonian strata, with some lower Silurian strata also present. This study applies three supervised machine learning algorithms Random Forest (RF), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost) to generate mineral prospectivity mapping (MPM) for epithermal gold mineralization in the Tobique–Chaleur Zone of northern New Brunswick. A total of 24 evidence layers, derived from geological, geochemical, and geophysical datasets, were selected based on a mineral systems framework to represent key ore-forming processes including source, pathway, and trap components. Model performance was evaluated using Receiver Operating Characteristic (ROC) curves, with RF achieving the highest AUC (0.93), followed by SVM (0.92) and XGBoost (0.91). Additionally, prediction–area (P–A) plot analysis revealed that XGBoost was the most efficient model in terms of spatial targeting. A majority voting ensemble and confidence index map were employed to enhance robustness and quantify model uncertainty. The spatial correlation of high-prospectivity zones with known gold occurrences and key geological features validates the applied approach. These results demonstrate the effectiveness of integrated machine learning and mineral systems modeling in generating reliable and interpretable prospectivity maps for mineral exploration.

Using mineral prospectivity mapping (MPM), the mineral systems approach enables the identification of geological indicators linked to ore formation. This approach streamlines exploration by minimizing the time and cost required to identify areas with the highest mineral potential. With its extensive till cover and dense forests limiting bedrock exposure, New Brunswick provides an ideal environment to test this approach. The New Brunswick portion of the Canadian Appalachians hosts a diverse range of gold deposits and occurrences that formed during various stages of the Appalachian orogeny. In northern New Brunswick and the adjacent Gaspé Peninsula, the Tobique–Chaleur Zone contains several orogenic and epithermal gold systems that are closely associated with a large-scale crustal fault and its offshoots, i.e., the long-lived trans-crustal Rocky Brook–Millstream Fault system. To identify favorable zones for epithermal gold mineralization in northwestern New Brunswick, this study employed MPM by translating key mineral system components—such as ore metal sources, fluid pathways, traps, and geological controls—into mappable criteria for regional-scale analysis. The data were modeled through the integration of knowledge-based and data-driven methods, including fuzzy logic, geometric average, and logistic regression approaches. The concentration–area (C–A) fractal model was applied to reclassify the final maps based on prospectivity values obtained from these three approaches, dividing the mineral prospectivity maps into six classes, with threshold values emphasizing high-favorability zones. The fuzzy overlay model had the highest predictive accuracy (AUC 0.97), followed by the geometric average model (AUC 0.93), whereas the logistic regression identified more tightly constrained high-potential zones. In the prospectivity models, known epithermal gold mineralization consistently overlaps with regions of high favorability. This suggests a positive result from the use of MPM, indicating that this approach could be applicable to other regions and types of ore deposits.

Zircon is a common, widely distributed accessory mineral in most igneous rocks and its refractory nature records magmatic evolution in terms of oxygen and U-Th-Pb isotopes, and trace-element contents all of which reflect the intrinsic physio-chemical evolution of the magmatic systems in which it crystallized. Zircon compositions can be used as an indicator of relative fertility of hypabyssal intrusions in terms Cu ± Mo ± Au porphyry mineralization. To further characterize syn- to post-collisional adakitic Devonian oxidized I-type granitoids in the New Brunswick (specifically, those with Cu ± Mo ± Au porphyry-style mineralization), LA-ICP-MS analyses (guided by µXRF-EDS mapping and SEM-BSE imaging of polished thin sections) of zircons from 13 granitoids was conducted. The zircons studied were similar in terms of their textures (homogenous cores, patchy zoning, oscillatory zoning, and some unzoned zircon); however, they have a wide range of trace- and minor-element (Hf, HREE, Y, Th, U) compositions. Specifically, Zr/Hf ranges between 24–60, whereas Th/U ranges between 0.15 and 5.37. The presence of inherited zircon affects the concentrations of Th and U, as well as other key elements. Estimated crystallization temperatures of granitoids, ranging from 737 to 899°C, were calculated via Ti-in-zircon geothermometry assuming reduced TiO2 and SiO2 activities. The calculated log fO2 values for zircons from some of these granitoids indicate a highly oxidized magmatic signature. Zr/Hf, Eu/Eu⁎, and (Eu/Eu⁎)/Y in zircon, as well as zircon (Ce/Nd)/Y are some of the best indicators of porphyry fertility. The Ce/Ce* in zircon exhibit a large range (1.1–590), with higher Ce/Ce* reflecting more metallogenically favourable oxidizing conditions. If Eu/Eu⁎ in zircon is ≥0.4 (relatively oxidized conditions), it indicates a high potential for an ore-forming porphyry Cu mineralizing system. Lower Eu contents reflect relatively reducing conditions, as Eu anomalies vary with oxygen fugacity as well, and the relative abundance of Eu2+ is higher, but does not substitute into the zircon lattice. The evidence extracted from analyzing the zircon composition within New Brunswick’s I-type granitoids indicates the fertility of these hypabyssal intrusions.

Dykes intruding along the Melanson Brook Fault record two magmatic episodes in northern New Brunswick. Dykes at the South Gold Zone of the Elmtree gold deposit are aphanitic and magnesian-calcic, whereas those at Ellis Brook (2.5 km to the west) are ilmenite-series and weakly peraluminous with hornblende- and plagioclase-porphyritic phases. Elevated 147 Sm/ 144 Nd generated by partial melting, titanium depletion, absence of rare earth element fractionation, and trondhjemite-like compositions indicate that the South Gold Zone dykes were sourced from low-volume fluid-fluxed melting of gabbroic crust. An Sm-Nd-depleted model mantle age of 1.1 Ga for the Ellis Brook dykes suggests that they were sourced from melting of Ganderian crustal rocks rather than the sinking Acadian slab. 143 Nd/ 144 Nd evolution curves for the South Gold Zone dykes intersect that of the Ellis Brook dykes at 432 and 427 Ma. This suggests that the magma from which the South Gold Zone dykes crystallized was extracted from a similar source area as the magma that generated the Ellis Brook dykes. Evidence of fluid exsolution in the Ellis Brook dykes indicates that they could be a potential source for reduced intrusion-related gold mineralization. The Ellis Brook dykes yielded a U-Pb zircon age of 391 +/- 5 Ma, which is consistent with the timing of oceanic slab break-off at the end of the Acadian orogenic cycle. Extraction of South Gold Zone magma occurred up to 40 Myr earlier, likely during the Salinic orogenic cycle.

Development of the continental shelf has accelerated significantly as nations around the world seek to harness offshore renewable energy. Many areas marked for development align with submerged palaeolandscapes. Poorly understood and difficult to protect, these vulnerable, prehistoric landscapes provide specific challenges for heritage management. Indeed, there now appears to be a schism between what underwater cultural heritage policy intends and what it is achieving in practice. Shortcomings in international and national legislature ensures that large parts of the continental shelf, including areas under development, may have little or no legal protection. Increasingly impacted by extensive development, these unique cultural landscapes are ever more at risk. However, heritage challenges posed by such development also create opportunities. An immense amount of data is being generated by development, and there is an opportunity to establish broader cooperative relationships involving industrial stakeholders, national curators, government bodies, and heritage professionals. As a matter of urgency, the archaeological community must better engage with the offshore sector and development process. If achieved, we may revolutionise our knowledge of submerged prehistoric settlement and land use. Otherwise, our capacity to reconstruct prehistoric settlement patterns, learn from past climate change, or simply manage what are among the best-preserved postglacial landscapes globally may be irreparably undermined.

The Storegga tsunami (c. 8150 cal BP) is geologically well attested from various isolation basins across the west Norwegian coast. Ascertaining the impact it had upon the Mesolithic peoples who lived through it, however, remains a difficult proposition; one further complicated by broadly synchronic processes of climate change and sea-level rise. This paper presents a regional scale approach to addressing this matter through a multiproxy study comprising: 1) the performance of a new numerical tsunami run-up simulation for six different focus areas; 2) characterising the impact of the tsunami upon key resource base ecosystems; 3) characterising the potential for complication arising from contemporaneous processes of environmental change caused by the '8.2 ka BP event', and sea-level rise associated with the early-mid Holocene 'Tapes' transgression, and 4) the reconstruction of temporal traditions in site location relative to the contemporary palaeoshoreline within the six focus areas used for the numerical simulation. Severity of run-up and inundation is found to be acutely variable according to coastal geomorphology and topography, bathymetry, and proximity to the propagation centre. Although the tsunami may have had a severely negative impact upon some coastal inhabitants and ecosystems, it is not possible from current evidence to reliably infer unequivocal impacts relating to the tsunami through the archaeological record, nor is it clear that impact upon key ecosystem components was necessarily lasting, widespread, or even entirely negative for coastal hunter-fisher-gatherers. Variability in projected run-up and settlement histories highlight the appeal of regionally based approaches to reconstructing impact, at least where data resolution may permit. The tsunami does not appear to have prompted a lasting shift away from coastally oriented ways of life.

High-silica adakites exhibit specific compositions, as follows: SiO2 ≥ 56 wt.%, Al2O3 ≥ 15 wt.%, Y ≤ 18 ppm, Yb ≤ 1.9 ppm, K2O/Na2O ≥ 1, MgO < 3 wt.%, high Sr/Y (≥10), and La/Yb (>10). Devonian I-type adakitic granitoids in the northern Appalachians of New Brunswick (NB, Canada) share geochemical signatures of adakites elsewhere, i.e., SiO2 ≥ 66.46 wt.%, Al2O3 > 15.47 wt.%, Y ≤ 22 ppm, Yb ≤ 2 ppm, K2O/Na2O > 1, MgO < 3 wt.%, Sr/Y ≥ 33 to 50, and La/Yb > 10. Remarkably, adakitic intrusions in NB, including the Blue Mountain Granodiorite Suite, Nicholas Denys, Sugar Loaf, Squaw Cap, North Dungarvan River, Magaguadavic Granite, Hampstead Granite, Tower Hill, Watson Brook Granodiorite, Rivière-Verte Porphyry, Eagle Lake Granite, Evandale Granodiorite, North Pole Stream Suite, and the McKenzie Gulch porphyry dykes all have associated Cu mineralization, similar to the Middle Devonian Cu porphyry intrusions in Mines Gaspé, Québec. Trace element data support the connection between adakite formation and slab break-off, a mechanism influencing fertility and generation of porphyry Cu systems. These adakitic rocks in NB are oxidized, and are relatively enriched in large ion lithophile elements, like Cs, Rb, Ba, and Pb, and depleted in some high field strength elements, like Y, Nb, Ta, P, and Ti; they also have Sr/Y ≥ 33 to 50, Nb/Y > 0.4, Ta/Yb > 0.3, La/Yb > 10, Ta/Yb > 0.3, Sm/Yb > 2.5, Gd/Yb > 2.0, Nb + Y < 60 ppm, and Ta + Yb < 6 ppm. These geochemical indicators point to failure of a subducting oceanic slab (slab rollback to slab break-off) in the terminal stages of subduction, as the generator of post-collisional granitoid magmatism. The break-off and separation of a dense subducted oceanic plate segment leads to upwelling asthenosphere, heat advection, and selective partial melting of the descending oceanic slab (adakite) and (or) suprasubduction zone lithospheric mantle. The resulting silica-rich adakitic magmas ascend through thickened mantle lithosphere, with minimal affect from the asthenosphere. The critical roles of transpression and transtension are highlighted in facilitating the ascent and emplacement of these fertile adakitic magmas in postsubduction zone settings.

As the back cover of the book notes, Chantal Conneller’s ‘The Mesolithic in Britain: Landscape and Society in Times of Change’ presents the first true synthesis of the British Mesolithic in 90 years. This is somewhat incredulous to think, but not a trivial point when considering the significance of this publication. To put this into perspective, the central premise around which The Mesolithic in Britain is structured is the proposal of a new chronological framework. When Grahame Clark’s PhD thesis was published in 1932 (the last time a synthesis of this kind was undertaken) the radiocarbon method was still 17 years away from being successfully demonstrated. To say that an update is overdue would be beyond an understatement. There have, of course, been less synthetical treatments of the British Mesolithic (e.g. Palmer 1977, Wymer 1991, Smith 1992), edited volumes (e.g. Conneller and Warren 2006), and summary papers and overviews (e.g. Tolan-Smith 2008). In addition, several parts of the British Isles have benefited immensely from being the subject of regionally focussed collections of papers and studies, including from recent decades, the Mesolithic of Scotland (Saville 2004, Warren 2005), Wales (Lillie 2015), and the northeast of England (Waddington and Pedersen 2007) among others. It has been apparent, since Clark’s treatment of the matter, that the British Mesolithic has never been a monolithic entity. An improved resolution of regional trends only makes the challenge of conducting an overview of the whole, and all the variability that that entails, an inherently challenging proposition to do justice. For a long time, the period has been framed through an ‘early/late’ division, but this has always been overly simplistic, and has increasingly come to obfuscate more than it helps to elucidate. Consequently, this division is eschewed in favour of a newly updated and more highly attuned alternative. The book begins by reviewing the history of British Mesolithic research, from Clark and his predecessors through to more contemporary leaders of the field, such as the late Caroline Wickham-Jones. It explores problems with the traditional framework before suggesting an alternative, comprising four phases with a chapter devoted to each, except for the first phase, which is given two chapters focusing on the differing nature of the earliest Mesolithic record from the north and south. These phases are, as follows: (1) 9500– 8200 BC (chapter focus on northern pioneers) and 9300–8200 BC (chapter focus on the ‘Early Mesolithic’ of the south), (2) 8200–7000 BC the ‘Middle Mesolithic’, (3) 7000–5000 BC the ‘Late Mesolithic’ and (4) 5000–4000 BC, the ‘Final Mesolithic’. These divisions are broadly reflective of spatial and temporal trends in microlith typology, underpinned where possible by an expanded and improved radiocarbon database. There is significant utility in this approach. Despite the chronological control brought to bear through radiometric dating, the nature of the Mesolithic record is such that many finds may remain undatable outside of typological affinity. The construction of a chronological framework that precludes the incorporation of a sizable chunk (if not a majority) of the relevant material, would be of limited value. Conneller is keenly aware, however, of the limitations inherent in using a limited sample of cultural referents (i.e. lithics) to infer larger patterns of cultural change and continuity, noting that this new schema should serve to ‘break down the Mesolithic into useful segments for analysis, some of which do seem to be related to a broader suit of new settlement feature, and thus might be seen as examples of “relevant” change’ (p. 24). While seeking to emphasize how life changed between 9300 and 3900 cal BC (p. 23), these divisions can perhaps ‘best be seen as a heuristic for dividing and comparing our data’ (p. 35).

The volcanic-hosted massive sulfide (VHMS) deposits of the Bathurst Mining Camp have been significant contributors to Canada's historic Zn, Pb, Cu, and Ag production. Most of these deposits are hosted by the Tetagouche Group, many of which occur at the top of the Nepisiguit Falls Formation (footwall) along the contact with the conformably overlying Flat Landing Brook Formation (hanging wall), i.e., the Brunswick belt. Exploration along this prolific belt can benefit greatly from predictive modeling of prospectivity for VHMS deposits using machine learning (ML)-based mineral prospectivity mapping (MPM), which is the chief objective of this study. However, ML-aided MPM of this belt is faced with three challenges: (i) weak geochemical and geophysical signatures of VHMS deposits (i.e., poor predictor variables) owing to the complex tectono-stratigraphy of the host sequence and extensive glacial cover, (ii) over-fitting stemming from its limited number of VHMS deposits, and (iii) stochastic uncertainties of predictive models linked to the diversity in local geological settings of various VHMS deposits. This study adopted an ensemble regularized regression methodology combining ensemble modeling with LASSO, Ridge, and Elastic Net regularized regression techniques for addressing the above challenges. Herein, we demonstrate that the adopted framework can reduce the severity of over-fitting, handle poor predictor variables, and mitigate the effects of stochastic uncertainties in ML-based MPM. These results are followed by discussions of the pros and cons of the framework adopted in this study.

An unusual molybdenite occurrence in northeastern New Brunswick, referred to herein as the Pabineau Lake Mo (PLM), is situated to the south of Bathurst. This occurrence consists of high-grade molybdenite-bearing granites that occur within the large Pabineau Falls Granite (PFG). To help evaluate the evolution of this occurrence, a large composite sample containing disseminated, very coarse molybdenite (up to 5.02 wt% MoS2) was collected from mineralized granitic blocks excavated from a blasted trench. Although the host rocks are assumed to be PFG, being the only defined intrusive body in the area, major- and trace-element geochemical data together with U-Pb geochronological results suggest that the molybdenite is hosted by an intrusion distinct from the PFG. The radiogenic Sr-Nd-Hf-Pb isotopic data of the host intrusion are consistent with Gander Zone granites of the Appalachians orogenic system. The PLM's granitic host rock is characterized by a high silica content (78.93 wt% SiO2), an enrichment in incompatible elements, and a high molybdenum content. The high initial Sr-87/Sr-86 of 0.71268, negative ENd of -1.28, and high Pb isotope ratios together with trace- and major-element concentrations indicate a moderately to highly radiogenic Sr source and derivation from a significant amount of supracrustal materials, with a contribution from the upper mantle; a source similar to that proposed for the Gander Zone Siluro-Devonian granitic bodies. A positive epsilon Hf (+1.34) also suggests involvement of sedimentary components. This is consistent with elevated Cr (20 ppm) and Ni (20 ppm). The involvement of a pelagic sedimentary component is invoked to explain the enrichment in elements commonly associated with mafic compositions. A new precise, LA ICP-MS zircon crystallization age of 390 +/- 1 Ma makes the PLM host granite Middle Devonian, which argues against a direct relationship with the older PFG (397.2 +/- 1.9 Ma). The new age opens the possibility of an as yet undelineated, mineralized intrusion within the Gander Zone, which has perhaps been missed during previous investigations due to the extensive glacio-fluvial cover and very limited bedrock exposures. Alternatively, the younger age could be attributed to very slow cooling and/or intra-pluton fractionation, resulting in a younger much more fractionated phase of the PFG. However, there is no geochemical evidence for such a prolonged continuous fractional crystallization process. Notably, recent geophysical surveys on the Bathurst Mining Camp indicate that the PFG is substantively larger than its surface expression as it continues to the east beneath the Carboniferous unconformity. Comparing ages of PLM and PFG with the nearby Nicholas-Denys Granodiorite (381 +/- 4 Ma) and Antinouri Lake Granite (372 +/- 4 Ma), it appears that magmatic activity in the region occurred every 10 Myr over a span of about 30 Myr. Collectively, this evidence suggests the potential of significant buried intrusions within this tectonic belt of the Gander Zone. At the PLM, this might include exposure of an otherwise hidden intrusion that is younger and much more fractionated than the PFG. More detailed geophysical and geochemical analyses would be required to revise the current geological map and, most importantly, trace unmapped units at depth to possible additional mineralized sequences.

Gold mineralization at Williams Brook in northern New Brunswick is hosted within the Siluro-Devonian, bimodal, volcano-sedimentary rocks of the Tobique–Chaleur Zone (Wapske Formation). Gold mineralization occurs in two styles: (1) as disseminations (refractory gold) in rhyolite, and (2) in cross-cutting quartz veins (free gold). Dating of the felsic volcanic host rocks by in situ LA–ICP–MS zircon U–Pb geochronology returned ages of 422 ± 3, 409 ± 2, 408 ± 3, 405 ± 2, and 401 ± 9 Ma. Zr/Y of subvolcanic felsic intrusion (<8 for syn-mineralization and >8 for post-mineralization) suggests evolution from transitional to more alkalic affinities. Two mineralizing events are recognized; the first is a disseminated mineralization style formed at ∼422–416 Ma and the second consists of quartz-vein-hosted gold emplaced at 410–408 Ma. Felsic rocks from Williams Brook and elsewhere in the Tobique Group (i.e., Wapske, Costigan Mountain, and Benjamin formations), and the Coastal Volcanic Belt have similar Th/Nb ratios of ∼0.1 to 1, reflecting similar levels of crustal contamination, and similar Nb and Y content, suggesting A-type affinities. These data indicate a similar environment of formation. Regionally, mafic rocks show similar within-plate continental signatures and a E-MORB mantle source that formed from partial melts of 10%–30%. Mafic volcanic rocks from Williams Brook have a more alkaline affinity (based on Ti/V) and derivation from lower percentage partial melting (∼5%). The chemical and temporal variations in the Williams Brook rocks suggest that they were erupted in an evolving transpressional tectonic setting during the oblique convergence of Gondwana and Laurentia.