Geological Surveys Branch

Fredericton, Canada

Geological Surveys Branch

Fredericton, Canada
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Zhang W.,Chinese Academy of Geological Sciences | Zhang W.,University of New Brunswick | Lentz D.R.,University of New Brunswick | Charnley B.E.,Geological Surveys Branch
Journal of Geochemical Exploration | Year: 2017

The Mount Pleasant polymetallic deposits are located along the southwestern margin of the Late Devonian Mount Pleasant Caldera Complex in southwestern New Brunswick, Canada. The Fire Tower Zone (W-Mo-Bi) and the North Zone (Sn-Zn-In) comprise the main mineralized zones within the Mount Pleasant deposit. The rock units examined at surface in both zones are highly altered and are surface weathered to some extent. In order to classify these rock units with confidence, the Olympus X-5000 portable X-ray Fluorescence (pXRF) spectrometer was used in this study to rapidly obtain the geochemical composition of these rocks, identify lithologic discriminants, and find alteration/mineralization indicators in these areas. The immobile elements Ti, Zr, Nb, Y, and Th were selected to discriminate among various rock types. The Little Mount Pleasant Formation has the highest Ti and Zr and the Mount Pleasant Granitic Suite (MPGS, GI and GII) contains the highest Y, Nb, and Th. The McDougall Brook Granitic Suite (MBGS) has an intermediate composition between them. The element ratios of Zr/Ti, Nb/Ti, Y/Ti, and Th/Ti effectively discriminate these rock units and increase from the Little Mount Pleasant Formation, to the MBGS, and then to the MPGS. Greisen and propylitic alteration are reflected by strong depletion of K and Rb in some samples. The Fe and Mn typically are leached out of the mineralization system during the greisen alteration. Principal component analysis (PCA) was performed on the pXRF datasets. The first principal component (PC1) of the pXRF data from both the Fire Tower Zone and the North Zone mainly extracts information on Ti, Zr, Ce, Cr, V, Nb, Y, U, and Th, and thus represents different rock units. The PC2 is characterized by high-positive loadings of K, Rb, Fe, and Mn and negative loading of As and Mo. It is interpreted as the W-Mo mineralization indicator showing by the enrichment in Mo and depletion of K, Rb, Fe, and Mn associated with quartz + topaz + sericite + fluorite alteration. The PC3 consists of positive loadings of Sn, Zn, Cu, and S and slightly negative loadings of Sr and Ba, and thus represents the Sn-Zn mineralization in this area. © 2017 Elsevier B.V.

Stimson M.R.,New Brunswick Museum Saint John | Miller R.F.,New Brunswick Museum Saint John | MacRae R.A.,Saint Mary's University, Halifax | Hinds S.J.,Geological Surveys Branch
Ichnos:an International Journal of Plant and Animal | Year: 2017

Microbially induced sedimentary structures (MISS) are an important facet of recent paleoichnological work because of their taphonomic implications. MISS are extensively studied in terms of their formation processes, recognition in the ancient record, and their diverse morphologies. Classification and terminology schemes are based on their appearance and mode of formation; however, the taxonomic treatment of MISS remains debated. Traditionally MISS have been considered sedimentary structures, and arguments have been made that they cannot be treated as trace fossils under the International Code of Zoological Nomenclature (ICZN) due to MISS being formed by communities of microbiota including algae, cyanobacteria, and others, rather than a single tracemaker. Here, we reexamine MISS using an ichnotaxonomic approach and apply ichnologic terminology and binomial names. Upon reexamining the holotype of Kinneyia Walcott, a genus commonly used to describe some MISS, we argue it cannot be used to correctly describe wrinkle or ripple-like features seen in MISS, and we agree with previous authors that Kinneyia is likely not biogenic in origin. We here assign a new ichnogenus and ichnospecies, Rugalichnus matthewii, to ripple-like sedimentary wrinkle marks known as MISS, separating them from the nomen dubium genus Kinneyia. © 2017 Taylor & Francis Group, LLC

Wilson R.A.,Geological Surveys Branch | Van Staal C.R.,Geological Survey of Canada | Kamo S.L.,University of Toronto
American Journal of Science | Year: 2017

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 transgressive-regressive sedimentary cycles, local disconformities and angular unconformities, and two stages (ca. 422-419 Ma, and ca. 417-407 Ma) of typically bimodal, within-plate magmatism. These events overlapped the end of the Salinic orogenic cycle, related to the ca. 430 Ma collision of the Ganderian passive margin with composite Laurentia, and the beginning of the Acadian cycle, which is associated with subsequent (ca. 424-422 Ma) collision and underthrusting of Avalonian crust beneath composite Laurentia (now including the Gander margin). Following Ganderia-Laurentia collision, the earlier (Pridolian) stage of withinplate magmatism is interpreted to result from ca. 425 Ma detachment of the subducting Tetagouche backarc lithospheric slab and is linked to the Salinic cycle, along with local, pre-Acadian (Salinic C) deformation of Ludlow-Pridoli rocks. Break-off of the Tetagouche slab also led to rapid uplift and subsequent extensional collapse of the Salinic metamorphic core, resulting in latest Silurian-earliest Devonian D3 vertical shortening and flat belt formation in the Brunswick subduction complex. Precise ID-TIMS U-Pb (zircon) dating of volcanic rocks reveals the existence of a 2.2 myr hiatus in the stratigraphic record, corresponding to an interpreted latest Silurian- earliest Devonian erosional surface between volcanic rocks identified with the Salinic cycle (Dickie Cove Group and lower part of Tobique Group) and those associated with the Acadian cycle (Dalhousie Group). The disconformity coincides with a widespread marine regression recorded by roughly coeval deposition of shallow-water to intertidal redbeds across the northern Appalachians. Marine regression is closely followed by deposition of Lochkovian deep marine sedimentary rocks (turbidites) in the Seboomook foredeep. This regressive-transgressive sequence immediately precedes arrival of the northwest-migrating Acadian deformation front, and is interpreted as evidence of a migrating Acadian forebulge-foredeep system associated with flexural loading of Ganderian crust by the Acadian orogenic wedge situated farther southeast in southern New Brunswick and coastal Maine. Early Devonian volcanism and Acadian retro-arc foreland deformation are linked to flat-slab convergence of Avalonia after underthrusting of buoyant Avalonian continental crust began ca. 418 Ma. It is proposed that the latest Silurian-earliest Devonian disconformity and marine regression mark the beginning of the Acadian orogenic cycle, implying that, in northern New Brunswick, the effects of waning, late Silurian (Salinic) deformation temporally overlapped the early, far-field effects of Acadian orogenesis.

LoDuca S.T.,Eastern Michigan University | Miller R.F.,New Brunswick Laboratory | Wilson R.A.,Geological Surveys Branch
Atlantic Geology | Year: 2013

Carbonaceous compressions from the Pridolian to middle Lochkovian Indian Point Formation in the Flatlands area of New Brunswick comprising a central axis with irregularly arranged unbranched appendages are assigned to Medusaegraptus mirabilis. This is the first report of intact thalli of this noncalcified macroalgal taxon from a locality outside of western New York. The biotic composition, stratigraphic context, and sedimentology of this occurrence suggest a shallow-marine depositional setting roughly comparable to that for the type material of Medusaegraptus mirabilis from Gasport, New York. © Atlantic Geology 2013.

Zhang W.,University of New Brunswick | Lentz D.R.,University of New Brunswick | Thorne K.G.,Geological Surveys Branch | McFarlane C.,University of New Brunswick
Ore Geology Reviews | Year: 2016

The Sisson Brook W-Mo-Cu deposit was formed by hydrothermal fluids likely related to the Nashwaak Granites (muscovite-biotite granite, Group I; and biotite granite, Group II) and related dykes (biotite granitic dykes, Group III; and a feldspar-biotite-quartz porphyry dyke, Group IV). Chemical data obtained using EPMA and LA-ICP-MS data of primary magmatic biotites were used to investigate magmatic processes and associated hydrothermal fluids.Trace element features of biotite in the Group I two-mica granite suggest other magmatic processes along with a simple fractional crystallization. The K/Rb ratios and compatible elements (Cr, Ti, Co, V, and Ba) in biotite from Groups II, III, and IV decrease, whereas incompatible elements including Ta, Tl, Ga, Cs, Li, and Sn increase with magma fractionation. No correlation of Cu, W and Mo with K/Rb ratios is evident, suggesting that partitioning of Cu, W, and Mo into biotite may not be entirely controlled by magma fractionation.Halogen fugacity of the parental magma of the Nashwaak Granites and related dykes, calculated from zircon saturation temperature shows that Group I has high fHF/fCl ratios (broadly higher than 0), similar to the plutons at the Henderson porphyry Mo deposit. The fHF/fCl ratios of the other groups are generally lower than 0, comparable to the Santa Rita porphyry Cu deposit. The fH2O/fHCl and fH2O/fHF ratios inferred from biotite in the Nashwaak Granites and related dykes range from 3 to 5 and from 4 to 5, respectively. The inferred oxygen fugacity shows that the dyke phases (Groups III and IV) have the oxygen fugacity around the nickel-nickel oxide buffer. The plutonic phases (Groups I and II) have the oxygen fugacity around the quartz-fayalite-magnetite (QFM) buffer at high temperatures and oxidized to nickel-nickel oxide buffer at lower temperatures. This oxidation process in the plutonic phases (Groups I and II) could be caused by H2 release at or near H2O vapor saturation at high H2O/Fe2+. The magma associated with the biotite dykes (Group III) is more likely the source of the hydrothermal fluids at the Sisson Brook deposit since it has the highest differentiation degree and seems to have formed in an oxidized setting, necessary for Mo to concentrate in the late stage fluids. © 2016 Elsevier B.V.

Zulu J.D.S.,University of New Brunswick | Lentz D.R.,University of New Brunswick | Walker J.A.,Geological Surveys Branch | McFarlane C.R.M.,University of New Brunswick
Journal of Geochemical Exploration | Year: 2016

The Key Anacon deposits, Bathurst Mining Camp, New Brunswick, are hosted in upper greenschist- to amphibolite-facies felsic volcanic rocks. The occurrence of cordierite-biotite and garnet-biotite-muscovite assemblages parallel to the regional tectonic fabric in the metamorphosed hydrothermal alteration zones point to a pre-metamorphic mineralization event that was synchronous with sub-aqueous volcanism. Modeling the altered felsic volcanic rocks in the system K2O-Fe2O3-MgO-Al2O3-SiO2-H2O-TiO2 (KFMASHT) and comparing the observed peak metamorphic assemblages with those produced in a petrogenetic grid allows us to interpret the style of pre-metamorphic hydrothermal alteration related to deposit formation. The compositional change in the stratigraphic footwall (structural hanging wall) is characterized by mass gains of 0.1 to 4.0 wt.% Fe2O3 (Total), 0.7 to 22.2 wt.% MgO, and 0.5 to 55.2 wt.% CaO, and mass losses of 25.1 to 56.7 wt.% SiO2, 0.2 to 2.0 wt.% Na2O, and 0.3 to 3.8 wt.% K2O (the values of the mass changes cited here are in absolute terms).Variable gains and losses of Zn, Pb, and Cu are characteristic of the footwall alteration zones with Zn displaying gains proximal to the massive sulfide lens, and losses distal to the sulfide lens. The alteration indices (AI) values increase as the massive sulfide lens are approached from either the footwall or hanging wall, whereas the Ghandi index (GI) discriminates the intensely chlorite-altered rocks proximal to mineralization from the sericitic altered rock in more distal areas. Overall, there is an increase of the GI from the weakly to moderately altered zone (GI = 1.3 to 6.0) to the more intensely altered zone (GI = 6.1 to 60). These physical and geochemical observations are consistent with early feldspar-destructive alteration followed by chloritization proximal to the sulfide lens and accompanied by sericitization alteration distal prior to sulfidation and oxidation during prograde metamorphism. © 2016 Elsevier B.V.

The central part of the Central plutonic belt in New Brunswick is underlain by numerous plutons of calc-alkaline, foliated and unfoliated granite that intrude Cambrian to Early Ordovician metasedimentary rocks. U-Pb (zircon) dating demonstrates that granites range in age from Middle Ordovician to Late Devonian, although most are late Silurian to Early Devonian. An age of 467 ± 7 Ma has been obtained on the foliated McKiel Lake Granite, whereas unfoliated intrusions yield ages of 423.2 ± 3.2 Ma (Bogan Brook Granodiorite), 420.7 +1.8/-2.0 Ma (Nashwaak Granite), 419.0 ± 0.5 Ma (Redstone Mountain Granite), 416.1 ± 0.5 Ma (Beadle Mountain Granite), 415.8 ± 0.3 Ma (Juniper Barren Granite), 409.7 ± 0.5 Ma (Lost Lake Granite), and 380.6 ± 0.3 Ma (Burnthill Granite). All plutons exhibit mixed arc-like and within-plate geochemical signatures, although the Redstone Mountain and Burnthill granites are dominantly within-plate type. Trace element data reveal a close overall geochemical similarity between Ordovician and Silurian – Devonian plutons, indicating that all were generated by partial melting of similar crustal sources and/or share a similar petrogenesis. Late Silurian to Early Devonian plutons mainly comprise biotite and/or muscovite-bearing, peraluminous granite and are considered prospective for granophile-element mineralization. All plutons contain Sn well in excess of the granite global average abundance, and several contain average tin values comparable to productive stanniferous granites elsewhere. The Burnthill, Lost Lake, Beadle Mountain and Nashwaak granites are geochemically most evolved and enriched in Sn and W. The Burnthill Granite in particular has experienced late-stage hydrothermal processes that have resulted in local enrichments of these elements. © Atlantic Geology 2016.

Dostal J.,Saint Mary's University, Halifax | Keppie J.D.,National Autonomous University of Mexico | Wilson R.A.,Geological Surveys Branch
Tectonophysics | Year: 2015

Upper Silurian to Lower Devonian volcanic rocks of the Gander Zone, from the northern mainland Appalachians of northern New Brunswick, occur in the Chaleur Bay Synclinorium which forms the southeastern part of the Middle Paleozoic Matapedia cover sequence. These rocks, which are parts of shallow marine to subaerial sequences (Dalhousie, Dickie Cove and Tobique groups), were erupted in a continental rift environment between ca. 422 and 407Ma. The volcanic rocks are mostly bimodal with mafic types corresponding predominantly to continental tholeiites inferred to be generated by partial melting of subcontinental lithospheric mantle (SCLM). The mafic rocks of all three groups have age-corrected eNd values ranging from +3.4 to +5.3, and depleted model mantle ages ranging from 0.65 to 0.95Ma that are interpreted to represent mantle enrichment ages associated with ancient Neoproterozoic subduction. This Neoproterozoic SCLM shows no contributions from juvenile Silurian mantle, suggesting that rifting was of limited extent and did not result in the replacement of the old SCLM by upwelling juvenile asthenosphere beneath the rift. These Nd isotopic data do not support the generation of the volcanic rocks by slab break-off, which would have likely introduced a juvenile asthenospheric mantle source for some of the Silurian-Devonian basaltic rocks. The ranges in eNd values and depleted mantle ages in northern New Brunswick are similar to those recorded in penecontemporaneous mafic lavas in Avalonia suggesting that the Neoproterozoic SCLM was common to both Avalonia and Ganderia. © 2015 Elsevier B.V.

Thorne K.G.,Geological Surveys Branch | Fyffe L.R.,Geological Surveys Branch | Creaser R.A.,University of Alberta
Atlantic Geology | Year: 2013

The Mount Pleasant granite-related polymetallic deposit, located on the southwestern margin of the Late Devonian Mount Pleasant Caldera Complex in southwestern New Brunswick, contains a significant resource of tin, tungsten, molybdenum, zinc, indium, and bismuth. The Caldera Complex comprises Intracaldera, Late Caldera- Fill, and Exocaldera sequences, and associated subvolcanic granitic rocks. Three granitic intrusions (Granite I, II, and III) are recognized in the Mount Pleasant Granitic Suite in the vicinity of the Mount Pleasant deposit and are interpreted to be fractionated components of the more widespread McDougall Brook Granitic Suite. Granite I and Granite II are associated with tungsten-molybdenum and indium-bearing tin-zinc mineralization, respectively. Despite extensive research in the Caldera Complex, the exact age of mineralization at Mount Pleasant has never been firmly established. An inferred age of < 363 Ma was based on the correlation of the dated Bailey Rock Rhyolite in the Exocaldera Sequence with that of the undated McDougall Brook Granitic Suite, which intruded the Intracaldera Sequence. New Re-Os dates of 369.7 ± 1.6 Ma and 370.1 ± 1.7 Ma obtained from molybdenite samples associated with tungsten-molybdenum mineralization at the Fire Tower Zone constrain the age of intrusion of Granite I and the initial onset of mineralization to ca. 370 ± 2 Ma (early Famennian). This is significantly older than the U-Pb age of 363 ± 2 Ma (late Famennian) previously obtained from the Bailey Rock Rhyolite in the Exocaldera Sequence. The McDougall Brook Granitic Suite, which pre-dated mineralization, must also be at least seven million years older than the Bailey Rock Rhyolite. A re-examination of the gradational relationship between the McDougall Brook Granitic Suite and purported rocks of the Bailey Rock Rhyolite in the Intracaldera Sequence suggests that the rhyolite should instead be assigned to the Seelys Formation. Our results suggest that deposition of the tungsten-molybdenum mineralization was likely associated with caldera collapse and an early phase of resurgent doming in response to degassing of the magma chamber. This interpretation contrasts with previous models of the eruptive history at Mount Pleasant, which inferred that mineralization was coincident with the later waning stages of volcanism. © Atlantic Geology 2013.

Recently gathered stratigraphic and U–Pb geochronological data indicate that the pre-Triassic rocks of the Grand Manan Terrane on the eastern side of Grand Manan Island can be divided into: (1) Middle Neoproterozoic (late Cryogenian) quartzose and carbonate sedimentary sequences (The Thoroughfare and Kent Island formations); (2) a Late Neoproterozoic (early Ediacaran) volcanic-arc sequence (Ingalls Head Formation); and (3) Late Neoproterozioc (mid-Ediacaran) to earliest Cambrian (early Terreneuvian) sedimentary and volcanic-arc sequences (Great Duck Island, Flagg Cove, Ross Island, North Head, Priest Cove, and Long Pond Bay formations). A comparison to Precambrian terranes on the New Brunswick mainland (Brookville and New River terranes) and in adjacent Maine (Islesboro Terrane) suggests that the sedimentary and volcanic sequences of the Grand Manan Terrane were deposited on the continental margin of a Precambrian ocean basin that opened during the breakup of Rodinia in the Middle Neoproterozoic (Cryogenian) and closed by the Early Cambrian (Terreneuvian) with the final assembling of Gondwana. Rifting associated with the initial opening of the Paleozoic Iapetus Ocean began in the Late Neoproterozoic (late Ediacaran) and so overlapped in time with the closing of the Precambrian Gondwanan ocean. The southeastern margin of the Iapetus Ocean is defined by thick sequences of quartzrich Cambrian sediments (within the St. Croix and Miramichi terranes of New Brunswick) that were largely derived from recycling of Precambrian passive-margin sedimentary rocks preserved in the Grand Manan and Brookville terranes of New Brunswick and in the Islesboro Terrane of Maine. These Precambrian terranes are interpreted to represent dextrally displaced basement remnants of the Gondwanan continental margin of Iapetus, consistent with the model of a two-sided Appalachian system proposed by Hank Williams in 1964 based on his work in Newfoundland. © 2014 GAC/AGC®.

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