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Simplified geology of the Chaleur Bay Synclinorium, showing the locations of samples collected for CA-ID-TIMS dating (including those published previously). Numerical superscripts on published ages refer to data sources: 1 -Wilson and others (2005); 2 -Wilson and Kamo (2008); 3 -Wilson and Kamo (2012); 4 -Walker and others (1993). The Chaleur zone is located north of the Rocky Brook-Millstream Fault and the Tobique zone is south of the fault. Inliers of Cambrian to Upper Ordovician rocks (Miramichi Group, Bathurst and Fournier Supergroups, and Balmoral Group) are shown in light gray. Uncolored areas are underlain by miscellaneous sedimentary cover rocks ranging in age from Late Ordovician to Early Carboniferous. Abbreviations: RS Restigouche Syncline; JRS Jacquet River Syncline; NRS Nigadoo River Syncline; SF Simpsons Field Formation. Volcanic edifices of the Wapske Formation in the central Tobique basin: MC Mount Carleton; SE Serpentine Mountain; BK Black Mountains; BL Blue Mountains; GL Gulquac Mountains. The inset at upper left illustrates the three subdivisions of the Matapedia Cover Sequence: CB Chaleur Bay Synclinorium; AP Aroostook -Percé Anticlinorium; CG Connecticut Valley -Gaspé Synclinorium. Cross-section A-A' is shown in figure 6.
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Geochronological data from volcanic rocks aid in reconstructing the Silurian–Devonian evolution of the northern Appalachians of New Brunswick in the context of Salinic (Silurian) and Acadian (Devonian) orogenesis. Late Silurian to Early Devonian sedimentation, volcanism and deformation in northern New Brunswick is complex, and characterized by tran...
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Abstract. Understanding the formation of economically important porphyry-Cu-Au deposits requires the knowledge of the magmatic-to-hydrothermal processes that act within the much larger underlying magmatic system and the timescales on which they occur. We apply high-precision zircon geochronology (CA-ID-TIMS) and spatially resolved zircon geochemist...
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... The northern Appalachians were subjected to multiple subduction/accretionary events, dominated by accretion of various terranes to the southeastern margin of composite Laurentia, which, as a result, progressively grew outward (van Staal et al., 1998; van Staal and Barr, 2012). A feature pertinent to this paper was a stage of shallow to flat slab subduction interpreted to be responsible for the advancing magmatism locally recognized in the north-ern Appalachians (Bradley et al., 2000;Wilson et al., 2017) during part of the latest Silurian to Devonian Acadian orogenic cycle (Murphy et al., 1999;Tucker et al., 2001;Schoonmaker et al., 2005;Hibbard et al., 2006; van Staal and Barr, 2012). It is still unclear when and where the progressive shallowing of the slab and phase of advancing magmatism occurred in the northern Appalachians, which hinders current understanding of the cause of along-strike variations in the tectonic evolution of the northern Appalachians (van Staal and Zagorevski, 2023). ...
... A northwestward younging trend is more clearly indicated by the distribution of Early Devonian magmatism relative to the Silurian magmatism ( Figs. 2 and 8). After a short-lived magmatic gap (∼5 m.y.), the magmatism migrated to the northwest by ∼90 km from the suture zone, which is consistent with the previously established pattern of hinterland migration of the Acadian deformation front in Maine and New Brunswick (Bradley et al., 2000;Wilson et al., 2017). A younging trend from ca. 415 Ma near the Dover-Hermitage Bay fault (boundary) zone to ca. 405 Ma at ∼90 km northwest from the suture zone suggests that the rate of magma migration was at least ∼9 km/m.y., which, if due to flat slab development and associated hinterland-directed arc migration (see below), also constrains the rate of underthrusting of Avalonia beneath the Gander margin (composite Laurentia). ...
... On the (Y + Nb)-Rb tectonic discrimination diagram, these rocks overlap the syncollisional and volcanic arc granite fields (Fig. 13A). These features also characterize Early Devonian silicic rocks in the Quebec, New Brunswick, Maine, and New Hampshire regions (Hon et al., 1992;Wilson et al., 2005Wilson et al., , 2017; Dorais, 2022). Many strongly peraluminous monzogranites and syenogranites and the adakitic rocks represented by the granodiorite to syenogranite group suggest that they were likely derived from partial melting of the thickened lower crust (Fig. 11E), i.e., a compressional syncollisional setting. ...
The migration and character of magmatism over time can provide important insights into the tectonic evolution of an orogen. We present evidence for three separate stages of compositionally distinct granitoid magmatism associated with the Acadian orogenic cycle in the eastern and southern Newfoundland Appalachians. The interpretations are based on new zircon U-Pb ages, geochemical data, and Sr-Nd-Hf-O isotopic data for 18 samples from 15 Silurian and Devonian granitoid plutons, combined with previously published data. The three stages outline hinterland- and foreland-directed migration trends and represent subduction (435−420 Ma), syncollision (415−405 Ma), and postcollision (395−370 Ma) settings in the Acadian orogenic cycle. The Silurian plutons (435−420 Ma) of the first stage consist mainly of quartz diorite, tonalite, granodiorite, monzogranite, and syenogranite, with high-K calc-alkaline and enriched Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = −5 to −2; εHf[t] = −3 to −1; δ18O = +6‰ to +8‰). They are interpreted to record the subduction of oceanic lithosphere of the Acadian seaway that separated the leading edge of composite Laurentia, represented by the Gander margin, and Avalonia. Early Devonian plutons (415−405 Ma) of the second stage contain more voluminous monzogranite and syenogranite; they have calc-alkaline to high-K calc-alkaline features, adakite-like compositions, and more depleted Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = −6 to 0; εHf[t] = +1 to +3; δ18O = +5‰ to +6‰). Plutons of this stage occur mostly to the northwest of the Silurian granitoids, indicating a regional-scale northwestward (hinterland-directed) migration of magmatism with a rate of >9 km/m.y. The migration is interpreted to have been related to the progressive shallow underthrusting of Avalonia beneath the Gander margin (composite Laurentia) at least as far as 90 km inboard. The Middle to Late Devonian plutons of the third stage (395−370 Ma) consist mainly of monzogranite, syenogranite, and alkali-feldspar granite, which are silica- and alkali-rich granites with large negative Eu anomalies. These rocks are concentrated along both sides of the Dover−Hermitage Bay fault zone, which represents the boundary between Avalonia and composite Laurentia, to the southeast of the Silurian and Early Devonian igneous rocks. This stage of magmatism represents a foreland-directed (retreating) migration. The Early Devonian and Middle to Late Devonian episodes of magmatism were separated by a gap between 405 Ma and 395 Ma and recorded an evolution from (high-K) calc-alkaline to alkaline compositions, ascribed to partial delamination of Avalonian lithospheric mantle in a postcollisional setting.
... Croix Belt) and Silurian Kingsclear Group (Fredericton Belt) to the northwest, from Silurian lithologies of the Mascarene Group (Mascarene Belt) to the southeast. The Sawyer Brook Fault was initiated as a fault scarp at the same Wilson et al. 2017;Johnson et al. 2018), ages are from time as the deposition of the Oak Bay Formation prior to 438 ± 4 Ma (Fyffe et al. 1999;Miller and Fyffe 2002). ...
... The Silurian Salinic orogeny is interpreted to reflect accretion of Ganderia to the Taconic-modified margin of composite Laurentia (van Staal et al., 2008(van Staal et al., , 2009(van Staal et al., , 2014(van Staal et al., , 2021Waldron et al., 2017). Tectonism associated with the Salinic orogeny is recorded by syn-tectonic deposition in the Fredricton trough, loading of the Gander margin, and associated metamorphism that is well documented in Atlantic Canada and coastal Maine (Dokken et al., 2018;van Staal et al., 2008; van Staal & de Roo, 1995;West et al., 1995West et al., , 2021Wilson et al., 2017). However, tectonometamorphism at this time in southern New England has not been well recognized by geochronologic or petrologic studies (Eusden et al., 2023;Hillenbrand et al., 2023;Karabinos et al., 2017). ...
Gneiss domes are an integral element of many orogenic belts and commonly provide tectonic windows into deep crustal levels. Gneiss domes in the New England segment of the Appalachian orogen have been classically associated with diapirism and fold interference, but alternative models involving ductile flow have been proposed. We evaluate these models in the Gneiss Dome belt of western New England with U‐Th‐Pb monazite, xenotime, zircon, and titanite petrochronology and major and trace element thermobarometry. These data constrain distinct pressure–temperature–time (P‐T‐t) paths for each unit in the gneiss dome belt tectono‐stratigraphy. The structurally lowest units, Laurentia‐derived migmatitic gneisses of the Waterbury dome, document two stages of metamorphism (455–435 and 400–370 Ma) with peak Acadian metamorphic conditions of ~1.0–1.2 GPa at 750–780°C at 391 ± 7 to 386 ± 4 Ma. The next structurally higher unit, the Gondwana‐derived Taine Mountain Formation, records Taconic (peak conditions: 0.6 GPa, 600°C at 441 ± 4 Ma) and Acadian (peak: 0.8–1.0 GPa, 650°C at 377 ± 4 Ma) metamorphism. The overlying Collinsville Formation yielded a 473 ± 5 Ma crystallization age and evidence for metamorphic conditions of 650°C at 436 ± 4 Ma and 1.2–1.0 GPa, 750–775°C at 397 ± 4 to 385 ± 6 Ma. The structurally higher Sweetheart Mountain Member of the Collinsville Formation yielded only Acadian zircon, monazite, and xenotime dates and evidence for high‐pressure granulite facies metamorphism (1.8 GPa, 815°C) at circa 380–375 Ma. Cover rocks of the dome‐mantling The Straits Schist records peak conditions of ~1 GPa, 700°C at 386 ± 6 to 380 ± 4 Ma. Garnet breakdown to monazite and/or xenotime occurred in all units at circa 375–360 and 345–330 Ma. Peak Acadian metamorphic pressures increase systematically from the structurally lowest to highest units (from 1.0 to 1.8 GPa). This inverted metamorphic sequence is incompatible with the diapiric and fold interference models, which predict the highest pressures at the structurally lowest levels. Based upon P‐T‐t and structural data, we prefer a model involving, first, circa 380 Ma thrust stacking followed by syn‐collisional orogen parallel extension, ductile flow, and rise of the domes between 380 and 365 Ma. Garnet breakdown at circa 345–330 Ma is interpreted to reflect further exhumation during collapse of the Acadian orogenic plateau. These results highlight the power of integrating petrologic constraints with paired geochemical and geochronologic data from multiple chronometers to test structural and tectonic models and show that syn‐convergent orogen parallel ductile flow dramatically modified earlier accretion‐related structures in New England. Further, the Gneiss Dome belt documents gneiss dome development in a syn‐collisional, thick crust setting, providing an ancient example of middle to lower crustal processes that may be occurring today in the modern Himalaya and Pamir Range.
... Nash Creek deposit is in the North of the Jacquet River Syncline (JRS) near the Bay of Chaleur, mainly underlain by the Early Devonian bimodal volcanic and intercalated marine sedimentary rocks of the Dalhousie Group. They were formed in a transtensional regime generated by transpression during the oblique accretion (Walker, 2009;Wilson et al., 2017;Barr and Geo, 2018). The deposits in New Brunswick are a sub-group of seafloor hydrothermal deposits hosted by mafic & felsic volcanics and sediments (Walker, 2009;Barr and Geo, 2018). ...
... In the geology of northeastern North America and the British Isles, the interval separating the Middle to early Late Ordovician Taconic-Grampian orogenies from the late Early to Middle Devonian Acadian Orogeny is problematic (Woodcock, 2012a-c;Strachan, 2012a,b;Dewey et al., 2015;Wilson et al., 2017). Based on palaeomagnetic, palaeontologic and provenance studies, most terranes associated with the peri-Gondwanan and peri-Baltican (sensu Landing et al., 2022) Avalonian and Ganderian domains (indicated in Fig. 1) were converging with Laurentia during most of the Ordovician and Silurian, but had already docked with it before the end of the Silurian (eg., Cocks and Torsvik, 2002;Murphy et al., 2004;van Staal et al., 2009van Staal et al., , 2012van Staal et al., , 2016Woodcock, 2012a,b). ...
... Based on palaeomagnetic, palaeontologic and provenance studies, most terranes associated with the peri-Gondwanan and peri-Baltican (sensu Landing et al., 2022) Avalonian and Ganderian domains (indicated in Fig. 1) were converging with Laurentia during most of the Ordovician and Silurian, but had already docked with it before the end of the Silurian (eg., Cocks and Torsvik, 2002;Murphy et al., 2004;van Staal et al., 2009van Staal et al., , 2012van Staal et al., , 2016Woodcock, 2012a,b). However, the conclusions of these studies still need to be reconciled with the structural and igneous rock records, as the Katian to earliest Emsian interval in these terranes is characterized by a paucity of igneous rocks with a clear arc signature and by rare and not regionally extensive compressional structures (Dostal et al., 1989(Dostal et al., , 1993Strachan, 2012a,b;Woodcock, 2012a-c;Wilson et al., 2017). This paper uses geochemical data on 417 samples of mafic to intermediate-felsic igneous rocks (45-70 % SiO 2 contents on a volatile-free basis) from the problematic 453-405 Ma interval in Ganderian, Avalonian composite East Avalonia laterally along the same plate margin, which generated slab-window volcanism at 454 Ma (Woodcock, 2012a, Jutras et al., 2020 (Figs. 2 and 4). ...
... The shutdown of south-dipping Iapetan slab subduction is penecontemporaneous with the onset of southwest-dipping subduction of the Tornquist slab beneath the northeastern part of composite East Avalonia and the Late Ordovician convergence of the latter with Baltica Noble et al., 1993;Torsvik and Rehnström, 2003) (Fig. 5). Katian times also saw the development of north-dipping subduction zones beneath composite Laurentia, which produced the Brunswick subduction complex from consumption of the Tetagouche-Exploits back-arc slab (van Staal et al., 1990(van Staal et al., , 1998(van Staal et al., , 2009; van Staal, 1994;Wilson et al., , 2015Wilson et al., , 2017 while the Southern Uplands accretionary wedge was developing from consumption of the Iapetan slab beneath geological terranes now belonging to the British Isles and Greenland ; Leggett et al., 1979;Ryan and Dewey, 1991;Strachan, 2012b;Hollocher et al., 2016;Chew and Strachan, 2014;McConnell et al., 2021) (Figs. 2 and 5). ...
Geochemical data from Katian to earliest Emsian ( 453–405 Ma) igneous rocks in northeastern North America and the British Isles were compiled to identify tectono-magmatic events related to ocean closure and the formation of the Appalachian–Caledonian Belt. These rocks all have geochemical affinities with plate-margin settings, but only a few can be attributed to arc magmatism, whereas the others have slab-failure signatures or affinities with anhydrous, extensional plate-margin (A2-type) settings. Based on these setting attributions as well as constraints from the palaeomagnetic, palaeontologic, structural, stratigraphic and sedimentologic records, a model for Iapetus and Rheic ocean closure is proposed, which also involves three subordinate ocean plate segments: the Tornquist Sea, Acadian Seaway and Tetagouche–Exploits oceanic back-arc basin. The model includes several new perspectives, such as (1) an early Silurian rather than late Silurian closure of the Tetagouche–Exploits back-arc basin; (2) Acadian Seaway slab failure at the Ludlow–Pridoli boundary due to its interaction at depth with the over lying and slowly-sinking Tetagouche–Exploits slab, which generated profuse, extensional, A2-type vol canism; and (3) an Early Devonian reactivation of Acadian Seaway slab subduction, possibly due to Rheic Ocean closure and the convergence of a Gondwanan promontory against Avalonia, which was attached to oceanic lithosphere of the Acadian Seaway. Furthermore, age constraints allowed to identify chronological trends in the geochemical signatures of the igneous rocks under study, which suggest that development of a new tectono-magmatic signature was gradual due to compositional inheritance from the previous setting. These trends also suggest that, although the transition from active subduction to slab failure generates an increase in Nb/Y and light over heavy rare earth elements, these ratios tend to decrease with time due to a fading contribution of the sinking slab at the source, whereas high-field-strength element contents tend to increase due to a lack of new water input from subduction.
... Zhang et al. [49] indicated that negative Nb and Ti anomalies in granitic rocks are related to their sources that had been metasomatized by subduction-related fluids, crustal contamination, or fractionation of Ti minerals (e.g., ilmenite and spinel). Wilson et al. [50] also suggested that negative anomalies of trace elements such as Nb are related to subduction-modified or continental sources. Figure 15 reveals that the ELG samples fall in the field of unfractionated I-type granites. ...
The NE-trending multiphase Late Devonian Eagle Lake granite (ELG) in southwestern New Brunswick is mineralized, consisting of hypabyssal porphyritic stocks and dikes that intruded Silurian metabasic volcanic rocks; however, its various phases, ages, and associations with notable stockwork Cu-Mo-Au mineralization and alteration have yet to have been studied. The ELG suite is predominantly composed of phenocrysts and a microcrystalline groundmass of quartz, K-feldspar, and plagioclase, with minor biotite and accessory minerals. In situ LA ICP-MS U-Pb zircon dating of this pluton yielded 360 ± 5 Ma (Late Devonian), so this pluton is considered part of the Late Devonian granitic series in southwestern New Brunswick. The isotopic analysis of two granitic samples yielded an initial 143 Nd/ 144 Nd of 0.512164 and 0.512184, initial 87 Sr/ 86 Sr of 0.70168 and 0. 70675, and initial 176 Hf/ 177 Hf of 0.282619 and 0.282631. The εNd (360 Ma) is −0.37 to +0.03, whereas the εHf (360 Ma) values are +2.1 and +2.5. Pb isotopic analysis yielded a 206 Pb/ 204 Pb of 18.49 and 18.72, 207 Pb/ 204 Pb of 15.62 and 15.63, and 208 Pb/ 204 Pb of 38.26 and 38.37, indicative of a relatively radiogenic source contaminating a primitive mantle melt. Potassic alteration and pyrite-quartz stockwork Cu-Mo-Au veining is evident in some parts of these porphyries. Petrographic and geochemical evidence indicates that this composite pluton is a low-T, I-type granite with zircon saturation temperatures between 720 • and 825 • C, with emplacement depths of 10.3 to 4.4 km. ELG was emplaced along a major structural trend manifested by contemporaneous faults and shear zones, i.e., the Belleisle Fault Zone in southern New Brunswick.
... It should be noted that major sources for gold in the Appalachians are Cambrian to Ordovician sedimentary rocks and Cambrian to Ordovician magmatic arcs. The New Brunswick portion of the Canadian Appalachians hosts for types of gold deposits, which formed during various stages of the Appalachian orogeny and subsequent episodes of exhumation and erosion (Wilson et al., 2017;Romer and Kroner, 2018). Among gold deposits in New Brunswick, the structurally controlled, orogenic-and intrusion-related auriferous systems are the most important deposit types. ...
... The proposed study area is located in northern New Brunswick and the project will focus on gold deposits/occurrences in the Tobique-Chaleur, and Kedgwick, belts. Northern New Brunswick is underlain by the post-Taconic, Middle Paleozoic Matapédia Cover Sequence (MCS) and deformed Early Paleozoic inliers to the northwest (Popelogan) and southeast (Miramichi and Elmtree) (Wilson, 2017). Numerous gold occurrences/deposits occur in and around the Tobique-Chaleur Zone in northern New Brunswick and the adjacent Gaspé Peninsula. ...
... Although these are dominantly orogenic style Au occurrences, a few epithermal style occurrences spatially related to the Rocky Brook-Millstream and the Restigouche Grand Pabos faults are recognized. For example, gold mineralization in the Williams Brook area exhibits characteristics of low-sulfidation epithermal style systems (Wilson, 2017). Gold abundances were obtained from the Dalhousie Road, McCormack Brook, Simpsons Field and Upsalquitch Forks occurrences (Ruitenberg et al. 1989). ...
This project will focus on four aspects 1) postulation of a framework that can be applied to a suite of mineral-system derived targeting criteria and generating mineral prospectivity mapping (MPM) through geological, geochemical and geophysical data; 2) recognition and analysis of structural features, that are spatially and genetically related to gold mineral systems in northern New Brunswick; 3) geochemical processing using multiple approaches for separation of anomaly from the background; and 4) determining the age of the gold mineralization and its relationship with magmatic to tectonic events using radiogenic isotopic geochronology.
... Acadian convergence continued during the Early Devonian in the northern Appalachians and Caledonides of the British Isles and led to shallow underthrusting of a large part of Avalonia beneath Laurentia (van Staal et al., 2021). Underthrusting was most pronounced in the northern Appalachians (Mojaver et al., 2021), where it produced a Puna-style orogenic plateau in southern New England ( Fig. 1; Hillenbrand et al., 2021) and a retro-arc foreland basin that progressively migrated westward over time (Bradley et al., 2000;Wilson et al., 2017). Post-seaway closure convergence was probably driven by the rapid southerly or southeasterly drift of Laurentia (van Staal et al., 1998, their fig. ...
The North American continent has a rich record of the tectonic environments and processes that occur throughout much of Earth history. This Memoir focuses on seven “turning points” that had specific and lasting impacts on the evolution of Laurentia: (1) The Neoarchean, characterized by cratonization; (2) the Paleoproterozoic and the initial assembly of Laurentia; (3) the Mesoproterozoic southern margin of Laurentia; (4) the Midcontinent rift and the Grenville orogeny; (5) the Neoproterozoic breakup of Rodinia; (6) the mid-Paleozoic phases of the Appalachian-Caledonian orogen; and (7) the Jurassic–Paleogene assembly of the North American Cordillera. The chapters in this Memoir provide syntheses of current understanding of the geologic evolution of Laurentia and North America, as well as new hypotheses for testing.
... The timing of this juxtaposition is locally constrained to between 423 and 395 Ma (Kellet et al., 2021), or ca. 424 to 422 Ma (Wilson et al., 2017), but may not be everywhere the same age along the length of this structure (see Kellett et al., 2014). The origin and wider context of Avalonia within the tectonic evolution of the Appalachians are beyond the scope of this guidebook, but it, along with similar rocks in Europe, North Africa and South America, is generally considered to be an amalgam of mainly juvenile crustal blocks that developed along the margin of Rodinia and were subsequently accreted to the northern Gondwanan margin (e.g., Nance et al., 2008; Cocks andFortey, 2009). ...
... The W enlock to P ridoli s patio-temporal d evelopment of this extensional fault network is consistent with the findings of van Staal et al. (2014), who noted that Silurian magmatism gets progressively younger west-to-east across the Dunnage Zone. Such extensional fault systems may have formed during thinning associated with asthenospheric and lithospheric decompression melting and upwelling related to slab rollback and break-off, and potentially lithospheric delamination, following the terminal Salinic collision of Ganderia with composite Laurentia (Pitcher 1983(Pitcher , 1993Wilson 2007;Wilson et al. 2017;Dostal et al. 2020;Bustard et al. 2021). This fault zone appears to correlate with the Cape Ray-Victoria Lake-Valentine Lake fault corridor in southwestern and central Newfoundland, strongly suggesting that the orogenic gold system of central Newfoundland is continuous along-strike in the northern Appalachians. ...
Bimodal igneous suites and associated immature clastic sedimentary rocks are characteristic of many orogenic gold-mineralized, crustal-scale fault zones globally. In the central Newfoundland Appalachian orogen, the Rogerson Lake Conglomerate belt and Botwood basin are Late Silurian (Wenlock to Pridoli), fault-controlled sedimentary rock sequences and magmatic suites closely associated with orogenic gold mineralization; however, the spatio-temporal evolution of faulting and associated sedimentation and magmatism are not fully resolved.
U–Pb zircon geochronological results were obtained by using an integrated approach employing LA-ICPMS (laser ablation-inductively coupled plasma mass spectrometry) followed by CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) on the same detrital samples. Using this approach, a maximum depositional age for sedimentary rocks of the Rogerson Lake Conglomerate sequence is 421.9 ± 1.0 Ma (Pridoli), which confirms that they are younger than, and stratigraphically overlie, ca. 422–420 Ma igneous rocks exposed along the central Newfoundland gold belt. Towards the stratigraphic middle of the Botwood basin in north-central Newfoundland, a tuffite layer intercalated with graded siltstone produced a maximum depositional age of 427.9 ± 3.1 Ma (Wenlock; Homerian). The age of emplacement of an autobrecciated, flow-banded rhyolite dome of the Charles Lake volcanic belt along the northwestern Botwood basin is 429.3 ± 0.7 Ma (Wenlock; Homerian). The high-precision CA-ID-TIMS zircon data establish a clear link between Wenlock to Pridoli magmatism and sedimentation throughout central Newfoundland. Furthermore, these geochronological results are consistent with a structural model involving the southeastward (present-day coordinates) advancement of a transient extensional fault system across strike of the Exploits Subzone between ca. 429 and 418 Ma, with propagation along strike to the southwest (Rogerson Lake Conglomerate belt) between ca. 422 and 418 Ma. Extensional faulting may have contributed to basin formation, subsidence, and exhumation of pre-Late Silurian rocks of the Exploits Subzone.
Time-transgressive, extension-related magmatism and clastic sedimentation appear to mark the transition between the Salinic and Acadian orogenic cycles along the central Newfoundland gold belt. Transient Wenlock to Pridoli lithospheric extension may have been important for increasing heat and fluid flow in the crust as a prelude to Devonian crustal thickening, fluid focussing, and orogenic gold mineralization.
