2016

Permanent URI for this collectionhttps://hdl.handle.net/1807/71215

Browse

Now showing 1 - 20 of 86

The pre-Late Wisconsin stratigraphy of southern Simcoe County, Ontario: Implications for ice sheet build-up, decay, and Great Lakes drainage evolution
(Canadian Science Publishing, 2016-12-28) Mulligan, Riley P.M.; Bajc, Andy F.
Recent three-dimensional mapping investigations in southern Simcoe County, Ontario allow refinement of the existing regional stratigraphic framework. Analysis of 25 continuously-cored boreholes has revealed a complex but consistent sediment succession that provides a record of the last two glacial cycles (Marine Isotope Stages 1-6). Five stratigraphic units (SU 1-5) comprise the pre-Late Wisconsin record. The stratigraphy is floored by a presumed Illinoian glacial complex consisting of a lower, coarse-grained till (SU 1), locally overlain by stratified glaciolacustrine and glaciofluvial sediments (SU2), but more commonly capped by a stone-poor, fine-grained till (SU 3) of the Georgian Bay lobe. A widespread subaerial unconformity developed on the upper surface of SU3 contains organic-bearing, non-glacial deposits (SU 4) ranging between 54 800 Âą 3000 (considered beyond the limits of radiocarbon dating) and 37 450 Âą 590 14C yr BP. SU 4 is abruptly overlain by a thick succession of rhythmically laminated lacustrine muds graded upwards into glaciolacustrine silts and clays interrupted by regionally continuous sand bodies (SU 5). The succession is capped (and locally truncated) by Late Wisconsin Newmarket Till. The sedimentary record of southern Simcoe County is correlated with other well-studied reference sections in southern Ontario and contains information that informs reconstructions of former ice extents in the lower Great Lakes region following the Illinoian glaciation. Several sediment units host aquifers, but limited thickness and spatial extent, as well as issues with naturally-occurring dissolved gases and solids, restrict their use for groundwater supply.
Geophysical, geological and hydrogeological characterization of a tributary buried bedrock valley in southern Ontario
(Canadian Science Publishing, 2016-12-28) Steelman, Colby M; Arnaud, Emmanuelle; Pehme, Peeter; Parker, Beth L
Buried bedrock valleys infilled with Quaternary-aged sediment have the potential to become productive aquifers due to prevalent sand and gravel deposits often associated with these topographic lows. In areas where groundwater is drawn from the underlying bedrock aquifer, buried bedrock channels may significantly affect the spatial distribution of recharge and localized contaminant pathways. Therefore, understanding the form, distribution and the nature of Quaternary infill sediments within these buried bedrock river valleys, and their relationship to hydraulically-transmissive bedrock features is an important aspect of groundwater resource management. Here, we evaluate the effectiveness of electrical resistivity and seismic refraction collected over a partially urbanized 150 ha area with variable vegetation, roads, and structures, to map the spatial distribution of sediments and delineation of a channel segment associated with a regional bedrock valley. Electrical resistivity and seismic refraction was performed along 13 (covering ~11.6 km) and 7 transects (covering ~0.9 km), respectively, to map and characterize the bedrock surface morphology beneath a variable thickness of unconsolidated deposits. Three continuously cored holes and downhole geophysical logs, supplemented with four nearby water well records captured the in-channel as well as adjacent Quaternary stratigraphy (~15-40 m). Cores recorded multiple glacial till deposits and ice marginal processes associated with ice advances and retreats. Hydraulic transmissivity of the bedrock around the valley feature was evaluated using a FLUTeâ ˘ hydraulic transmissivity profiling technique. This study demonstrates the potential of combining several surface geophysical methods with sedimentological analysis of continuous cores and hydraulic data for characterizing tributary bedrock channel morphology and Quaternary infill at a scale relevant to localized studies of municipal production well recharge zones and contaminant transport and fate.
Carbonic fluids in the Hamadi gold deposit, Sudan: Origin and contribution to gold mineralization
(Canadian Science Publishing, 2016-12-02) Cheng, Xihui; Xu, Jiuhua; Wang, Jianxiong; Xue, Qingbo; Zhang, Hui
The Hamadi gold deposit is located in North Sudan, and occurs in the Neoproterozoic metamorphic strata of the Arabian–Nubian Shield. Two types of gold mineralization can be discerned: gold-bearing quartz veins and altered rock ores near ductile shear zones. The gold-bearing quartz veins are composed of white to gray quartz associated with small amounts of pyrite and other polymetallic sulfide minerals. Wall-rock alterations include mainly beresitization, epidotization, chloritization, and carbonatization. CO2-rich inclusions are commonly seen in gold-bearing quartz veins and quartz veinlets from gold-bearing altered rocks; these include mainly one-phase carbonic (CO2 ± CH4 ± N2) inclusions and CO2–H2O inclusions with CO2/H2O volumetric ratios of 30% to ∼80%. Laser Raman analysis does not show the H2O peak in carbonic inclusions. In quartz veins, the melting temperature of solid CO2 (Tm,CO2) of carbonic inclusions has a narrow range of −59.6 to −56.8 °C. Carbonic inclusions also have CO2 partial homogenization temperatures (Th,CO2) of −28.3 to +23.7 °C, with most of the values clustering between +4.0 and +20 °C; all of these inclusions are homogenized into the liquid CO2 state. The densities range from 0.73 to 1.03 g/cm3. XCH4 of carbonic fluid inclusions ranges from 0.004 to 0.14, with most XCH4 around 0.05. In CO2–H2O fluid inclusions, Tm,CO2 values are recorded mostly at around −57.5 °C. The melting temperature of clathrate is 3.8–8.9 °C. It is suggested that the lowest trapping pressures of CO2 fluids would be 100 to ∼400 MPa, on the basis of the Th,CO2 of CO2-bearing one-phase (LCO2) inclusions and the total homogenization temperatures (Th,tot) of paragenetic CO2-bearing two-phase (LCO2–LH2O) inclusions. For altered rocks, the Tm,CO2 of the carbonic inclusions has a narrow range of −58.4 to ∼−57.0 °C, whereas the Th,CO2 varies widely (−19 to ∼+29 °C). Most carbonic inclusions and the carbonic phases in the CO2–H2O inclusions are homogenized to liquid CO2 phases, which correspond to densities of 0.70 to ∼1.00 g/cm3. Fluid inclusions in a single fluid inclusion assemblage (FIA) have narrow Tm,CO2 and Th,CO2 values, but they vary widely in different FIAs and non-FIAs, which indicates that there was a wide range of trapping pressure and temperature (P–T) conditions during the ore-forming process in late retrograde metamorphism after the metamorphism peak period. The carbonic inclusions in the Hamadi gold deposit are interpreted to have resulted from unmixing of an originally homogeneous aqueous–carbonic mixture during retrogress metamorphism caused by decreasing P–T conditions. CO2 contributed to gold mineralization by buffering the pH range and increasing the gold concentration in the fluids.
U–Pb zircon geochronology and depositional history of the Montresor group, Rae Province, Nunavut, Canada
(Canadian Science Publishing, 2016-12-19) Percival, John A.; Davis, William J.; Hamilton, Michael A.
Paleoproterozoic metasedimentary successions of the northwestern Canadian Shield provide records of tectonic events, but the definition of depositional ages has proved elusive. Although previously poorly understood, the Montresor belt of western Nunavut yields new insight into the 2.2–1.8 Ga time window. On the basis of U–Pb analyses of detrital zircon in sedimentary rocks and igneous zircon in sills, we conclude that arenite of the lower Montresor group was deposited between 2.194 and 2.045 Ga, and arkose of the upper Montresor group after 1.924 Ga, adding constraints on the Rae cover sequence. The lower Montresor arenite yielded an older group (3.05–2.58 Ga) and a younger, more tightly constrained group (2.194 ± 0.014 Ga). Four of six zircon grains analyzed from a gabbro sill within the lower Montresor have discordant 207Pb/206Pb ages (2.71, 2.66, 2.53, and 2.39 Ga) and are considered to be inherited, whereas two grains provide an age of 2045 ± 13 Ma, interpreted to date crystallization and providing a minimum age for the lower Montresor package. Upper Montresor arkose contains detrital zircon with probability density peaks at 2.55–2.25 and 2.1–1.92 Ga, together with scattered older grains (3.8–2.65 Ga). The youngest grain yields an age of 1924 ± 6 Ma, establishing a maximum age for sandstone deposition. Provenance is inferred to have been from the west, where igneous sources of 2.5–2.3 Ga (Queen Maud block) and 2.03–1.89 Ga (Thelon orogen) are known. Collectively, the new ages suggest a minimum 120 million year gap between deposition of the pre-2045 ± 13 Ma lower and post-1924 ± 6 Ma upper parts of the Montresor group. Similar age constraints may apply to other parts of the Rae cover sequence.
The Devonian Horn River Group and the basal Imperial Formation of the central Mackenzie Plain, N.W.T., Canada: Multiproxy stratigraphic framework of a black shale basin
(Canadian Science Publishing, 2016-11-25) Kabanov, Pavel; Gouwy, Sofie Annie
This study proposes six new lithostratigraphic units and redefines two others within the Horn River Group (HRG), a shale-dominated succession recently prospected for shale hydrocarbons. Its lower Hare Indian Formation rests on a drowning unconformity. In the SOB area (the area between Norman Wells and the Keele tectonic zone), this formation consists of the Bluefish black shale, Francis Creek grey shale, and Prohibition Creek black shale members. The latter two are lateral equivalents of the grey shale Bell Creek Member (updated definition) in the northern part of the study area. The overlying Canol Formation in the SOB area is divided into the Vermillion Creek and Dodo Canyon members. The Prohibition – Dodo Canyon package is ≥100 m thick and composed of brittle siliceous mudrocks with median SiO2 68%–79%, Al2O3 6%–9%, varying amount of calcite and dolomite, and type I–II kerogen with median TOC 4.5%. The thin Canol Formation blanketing Kee Scarp carbonate banks is identified as its Dodo Canyon Member. The latter is a “sweet bed” for fracking with median SiO2 75%–79%, TOC 5.1%, and trace-metal signatures indicating strongest anoxia in the section. The Mirror Lake Member in the base of the overlying Imperial Formation consists of soft illite-rich grey shales with minor siderite and dolomite. The overlying Loon Creek Member is composed of Canol-like black shale facies in its basal part and less organic-rich, lighter-colored shales and siltstones above. The Loon Creek Member is partly coeval with an overlying succession of sandstones and siltstones of the Canyon Member in its updated definition. Conodont data do not indicate significant time gaps between lithostratigraphic units. The majority of standard conodont zones from the uppermost Eifelian (ensensis Zone) up to the middle Frasnian (punctata Zone) are recognized. Assemblages of the hemiansatus and semialternans/latifossatus zones are missing probably owing to scarcity of conodont samples. The base of the HRG approximates the Eifelian–Givetian boundary, and the Hare Indian Formation is mostly Givetian. The Vermillion Creek Member spans the Givetian–Frasnian boundary. In places where thick Kee Scarp carbonates aggrade on thick sections of the Bell Creek Member, the Kee Scarp – Canol contact is found within the transitans Zone and the Middle Frasnian punctata Zone conodont assemblage is found in the basal part of the Dodo Canyon Member. The main part of the Dodo Canyon Member and basal beds of the Imperial Formation remain undated.
Focal depth distribution of the 1982 Miramichi earthquake sequence determined by modeling depth phases
(Canadian Science Publishing, 2016-12-06) Ma, Shutian; Motazedian, Dariush
On 9 January 1982, in the Miramichi region of New Brunswick, Canada, an earthquake with body-wave magnitude (mb) 5.7 occurred, and extensive aftershocks followed. The mainshock was felt throughout Eastern Canada and New England, USA. The mainshock and several principal aftershocks were digitally recorded worldwide, but smaller aftershocks were digitally recorded only at regional stations. Digital stations were not yet popular in 1982; therefore, available regional digital waveform records for modelling are very limited. Fortunately, two Eastern Canada Telemetered Network (ECTN) stations, EBN and KLN, produced excellent waveform records for most of the aftershocks until their closure at the end of 1990. The waveform records can be retrieved from the archive database at the Geological Survey of Canada (GSC). Since EBN had clear sPmP records of the larger aftershocks (with magnitude mN ≥ 2.8), we were able to determine focal depths for these larger events. Most of the focal depth solutions for the 113 larger aftershocks were within a depth range of 3–6 km. The majority of the depths were at about 4.5 km. Some aftershocks had depths of about 1–2 km. The focal depth solutions for the shallow events were confirmed by the existence of prominent crustal Rayleigh waves. As the records for the foreshock and the mainshock at EBN were not available, we used the records at station LMN for the foreshock and a teleseismic depth phase for the mainshock. The teleseismic depth phase comparison shows that the mainshock and its three principal aftershocks migrated from a depth of about 7 km to near the Earth’s surface.
Remnants of Early Mesozoic basalt of the Central Atlantic Magmatic Province in Cape Breton Island, Nova Scotia, Canada
(Canadian Science Publishing, 2016-11-11) White, Chris E.; Kontak, Daniel J.; Demont, Garth J.; Archibald, Douglas
Amygdaloidal basaltic flows of the Ashfield Formation were encountered in two drill holes in areas of positive aeromagnetic anomalies in the Carboniferous River Denys Basin in southwestern Cape Breton Island, Nova Scotia. One sample of medium-grained basalt yielded a plateau age of 201.8 ± 2.0 Ma, similar to the U–Pb and 40Ar/39Ar crystallization ages from basaltic flows and dykes in the Newark Supergroup. A second sample of zeolite-bearing basalt yielded a discordant age spectrum and a younger age of ca. 190 Ma, which is interpreted to date a widespread hydrothermal event related to zeolite formation. Whole-rock chemical data show that the Ashfield Formation basalt is low-Ti continental tholeiite, consistent with its within-plate tectonic setting. Chemically, it resembles basaltic flows in the Mesozoic Fundy and Grand Manan basins exposed in southern Nova Scotia and eastern New Brunswick and elsewhere in Central Atlantic Magmatic Province (CAMP). The age and geochemical data from the Ashfield Formation provide the first evidence for early Mesozoic CAMP volcanism in Cape Breton Island and demonstrate that the event was more widespread in Nova Scotia than previously thought, which has implications for its continuity and extent elsewhere within CAMP.
Coastal retreat rates and sediment input in the Minas Basin, Nova Scotia
(Canadian Science Publishing, 2016-12-02) Wilson, Erin K.; Hill, Paul S.; van Proosdij, Danika; Ruhl, Monique
The strong tidal currents of the Minas Passage in the Bay of Fundy, Nova Scotia, have made this area an important site for testing and development of tidal power technologies. Understanding sediment processes in this area is essential for determining the impacts that large-scale tidal power extraction would have on the system. Previous estimates of sediment input to the Basin suggest that much more sediment enters the Basin than accumulates within it; therefore, the bottom sediment texture should be in hydrodynamic equilibrium with bottom currents. A recent study, however, showed that sediment texture is generally finer that what was expected based on current speeds. This paper uses geographic information systems methods to provide updated and more highly resolved measurements of the amount of sediment entering the Minas Basin from the dominant source, which is coastal erosion. Volumetric input from coastal erosion is 1.1 × 106 m3·a−1, which is more than two times smaller than previous estimates. This updated value makes input rates comparable to accumulation rates, and agrees with the hypothesis that bottom sediment texture is not in equilibrium with current speeds. Grain-size distributions also support the hypothesis that the Minas Basin acts as a sediment trap.
Investigating the Paleozoic-Mesozoic low-temperature thermal history of the southwestern Canadian Arctic: insights from (U-Th)/He thermochronology
(Canadian Science Publishing, 2016-11-08) Midwinter, Derrick; Powell, Jeremy; Schneider, David; Dewing, Keith
The Arctic Amerasia Basin, located between the Canadian margin and Alaska, formed by purported Jurassic–Cretaceous rifting related to the rotation of the Arctic Alaska – Chukotka microcontinent from northern Laurentia. Rifting may have been accompanied by rift shoulder uplift and cooling that is recorded in low-temperature thermochronometers. Furthermore, the southwestern Canadian Arctic has a widespread Devonian–Cretaceous unconformity with a poorly understood burial-unroofing history. We evaluate new zircon (U–Th)/He thermochronology (ZHe) and organic maturity (vitrinite reflectance (VRo)) data from Neoproterozoic strata of the Amundsen Basin, Cambrian strata of the Arctic Platform, and Devonian strata of the Franklinian Basin to help resolve the sedimentary thickness deposited and eroded during the time represented by the regional unconformity. ZHe and VRo models identify the thermal maximum occurring between the late Paleozoic – Mesozoic interval. Proximal to the rifted Canadian margin, models estimate 3.7–4.5 km of deposition between the Devonian–Cretaceous, in marked contrast to <1 km towards the craton. Jurassic–Cretaceous exhumation is estimated at 2.3–3.5 km and is more uniform across the region. Although the magnitude of burial and erosion can be resolved by modelling, the timing of these events cannot be elucidated with confidence. The thermochronology models can be satisfied by either (1) late Paleozoic – early Mesozoic burial with a thermal maximum prior to Jurassic rifting, followed by cooling; or (2) Late Devonian maximum burial, with gradual unroofing until Cretaceous sedimentation. Although continued deposition into the Mesozoic towards the craton interior seems unlikely, it remains possible that there was continued deposition proximal to the rifted Canadian margin.
Origin and evolution of ore-forming fluids, and genesis of the Duhuangling and Jiusangou gold deposits in eastern Yanbian, northeast China
(Canadian Science Publishing, 2016-11-18) Zhao, Ke-Qiang; Sun, Jing-Gui; Li, Liang; Men, Lan-Jing; Nagao, Keisuke; Chai, Peng
The Duhuangling and Jiusangou gold deposits are located east of the Yanbian area, NE China. We present the results of systematic studies of the ore geology, fluid inclusion (FI) features, and isotopic geochemistry of the two gold deposits. Four mineralization stages have been defined in each gold deposit: pyrite + sericite + quartz (stage I), quartz + pyrite ± chalcopyrite ± arsenopyrite (stage II), quartz + native gold + polymetallic sulfide (stage III), and quartz–calcite (stage IV). FIs from the two gold deposits are similar and contain five types: pure vapor phase (V-type), vapor-rich phase (RV-type), liquid-rich phase (RL-type), daughter mineral-bearing polyphase (S-type), and pure liquid phase (L-type) FIs. Stage I FIs homogenize at temperatures of 350–450 °C, yielding salinities of 5.40–48.67 wt.％. FIs from both stages II and III samples homogenize at 160–350 °C, yielding salinities of 5.71–39.75 wt.％. FIs in pyrite from the stage II have 3He/4He ratios of 0.0069–0.0148 Ra and 40Ar/36Ar ratios of 1302–4433, demonstrating that ore-forming fluids of the two gold deposits were derived from the crust. The dD values of the two gold deposits range from −107‰ to −92‰, with d18OH2O values of 4.3‰ to 9.0‰, indicating that the ore-forming fluids were mainly magmatic water in origin. Lead isotope data suggest that the ore-forming materials were originated from deep crust. Integrated data indicate that both Duhuangling and Jiusangou gold deposits are medium- to high-temperature, hydrothermal gold deposits.
Age and origin of the Cannon Point syenite, Essex County, New York: Southernmost expression of Monteregian Hills magmatism?
(Canadian Science Publishing, 2016-11-11) Bailey, David G.; Lupulescu, Marian V.; Chiarenzelli, Jeffrey R; Traylor, Jonathan P.
Two syenite sills intrude the local Paleozoic strata of eastern New York State and are exposed along the western shore of Lake Champlain. The sills are fine-grained alkali feldspar syenites and quartz syenites, with phenocrysts of sanidine and albite. The two sills are compositionally distinct, with crossing REE profiles and different incompatible element ratios, prohibiting a simple petrogenetic relationship. Zircon extracted from the upper sill yield a U-Pb age of 131.1 +/- 1.7 Ma, making the sills the youngest known igneous rocks in New York State. This age is similar to the earliest intrusions in the Monteregian Hills of Quebec, over 100 km to the north. Sr and Nd radiogenic isotope ratios are also similar to those observed in some of the syenitic rocks of the eastern Monteregian Hills. The Cannon Point syenites have compositions typical of A-type, within-plate granitoids. They exhibit unusually high Ta and Nb concentrations, resulting in distinct trace element signatures that are similar to silicic rocks of the Valles Caldera, a large, rift-related magmatic system. We suggest that the Cannon Point syenites were melts derived primarily by anatexis of old, primitive, lower crustal material in response to Mesozoic rifting and to the intrusion of mantle-derived magmas. The sills indicate that the effects of continental rifting were spatially and temporally extensive, resulting in the reactivation of basement faults in the Lake Champlain valley hundreds of kilometers west of the active rift boundary, and crustal melting over 50 Ma after the initiation of rifting.
Gravity and magnetic modelling of layered mafic-ultramafic intrusions in large igneous province plume centre regions; Case studies from the: 1.27 Ga Mackenzie, 1.38 Ga Kunene-Kibaran, 0.06 Ga Deccan and 0.13-0.08 Ga High Arctic events
(Canadian Science Publishing, 2016-11-11) Blanchard, Jennifer Amanda; Ernst, Richard; Samson, Claire
Gravity and magnetic data from the global EGM2008 and EMAG2 datasets are used to identify geophysical anomalies in Large Igneous Province (LIP) plume centre regions with the goal of characterizing mafic-ultramafic intrusions linked to those LIPs. Geophysical anomalies within eighteen LIPs distributed globally are investigated. Four of these LIPs are selected for detailed modelling: the 1.27 Ga Mackenzie, 1.38 Ga Kunene-Kibaran, 0.06 Ga Deccan and 0.13-0.08 Ga High Arctic LIPs. We recognize three spatial distribution types for intrusions in plume centre regions. These are: 1) intrusions emplaced along a circular fault system that circumscribe the plume centre, 2) intrusions emplaced along linear rifts that, in some cases, converge towards the plume centre, and 3) single/unclassified intrusions. Modelling supports that the geophysical anomalies associated with these LIPs tend to be produced by large (radius > 30 km) and deep-seated crustal intrusions, with densities consistent with mafic-ultramafic rock and magnetic susceptibilities consistent with serpentinized ultramafic rock, except within the Deccan where intrusions are smaller, mainly mafic in composition, and positioned at shallower depths in the crust.
Intensified aridity in the Qaidam Basin during the middle Miocene: constraints from ostracod, stable isotope and weathering records
(Canadian Science Publishing, 2016-10-27) Song, Bowen; Ji, Junliang; Wang, Chaowen; Xu, Yadong; Zhang, Kexin
The thick and continuous Cenozoic successions in the Qaidam Basin provide an excellent paleoclimate archive. Here, we focus on the ostracod fauna, stable isotope records, and paleoweathering indices from a well-dated Cenozoic sedimentary section in the Qaidam Basin, to develop an understanding of the middle Miocene aridification in central Asia. Microfossil analyses suggest that the ostracod species diversity suddenly decreased after 13.3 Ma, and that the dominant ostracod genus shifted from Ilyocypris to Cyprideis. Stable isotope data from ostracod valves display abrupt positive shifts of 3.75‰ in δ18O values and 5.28‰ in δ13C values since 13.3 Ma. The Chemical Index of Weathering (CIW) and K/Na ratios decrease markedly after 13.3 Ma, reflecting a significant decrease in chemical weathering intensity. These combined and consistent observations suggest that the Qaidam Basin has experienced increased aridification since 13.3 Ma. The dating was obtained direct from previous magnetostratigraphic studies and can be accurately correlated with global climate evolution and regional tectonic events. A comparing of these results with global paleoclimatic records and previous geologic studies of the Tibetan Plateau, revealed that global cooling rather than uplift of the Tibetan Plateau played a key role in the drying of the Qaidam Basin at approximately 13 Ma.
A large onychodontiform (Osteichthyes: Sarcopterygii) apex predator from the Eifelian-aged Dundee Formation of Ontario, Canada.
(Canadian Science Publishing, 2016-12-06) Mann, Arjan; Rudkin, David M.; Evans, David C.; Laflamme, Marc
The Devonian marine strata of southwestern Ontario, Canada have been well documented geologically, but their vertebrate fossils are poorly studied. Here we report a new onychodontiform (Osteichthyes, Sarcopterygii) Onychodus eriensis n. sp. from the Dundee Formation (Eifelian-Givetian boundary, 390-387 Ma) of southwestern Ontario represented by two well-preserved onychodontiform lower jaws. The most complete specimen consists of a large (28cm), well preserved right jaw with most of the dentition present. The dentary has 50 teeth, not including the parasymphysial tusk whorl, which is poorly preserved but consists of at least three tusks. The anteriormost teeth of the dentary are also not complete, but the second dentary tooth is notably procurved. The posterior teeth are conical and approximately equal in size for much of the length of the tooth row. Onychodus eriensis n. sp. differs from the closely related contemporary species Onychodus sigmoides, and all other onychodonts, in that it has a strong dorsal curvature of the anterior dentary ramus, and marked anterior expansion of the dentary. An expanded phylogenetic analysis of Devonian onychodontiforms suggests that O. eriensis is closely related to Onychodus jandemarrai. The new material indicates that Onychodontiformes is more diverse than previously recognized, and that further analysis of vertebrate remains from southwestern Ontario will lead to additional insights into the diversity of Devonian sarcopterygians.
Structure and kinematic evolution of the Duke River fault, Southwestern Yukon
(Canadian Science Publishing, 2016-10-02) Cobbett, Rose Natalie; Israel, Steve; Mortensen, James K.; Joyce, Nancy; Crowley, James J.L.
In southwest Yukon, the boundary between the Alexander terrane and Wrangellia corresponds with the Duke River Fault. In this paper, we report on observations of the Duke River Fault from four localities in southwest Yukon, and provide new constraints on (1) Permian regional metamorphism within the Alexander terrane, (2) Cretaceous ductile deformation along the Duke River fault and (3) post-Miocene brittle deformation along the fault. Within these areas, the Duke River Fault juxtaposes imbricated, pervasively foliated and folded greenschist-facies rocks of the Alexander terrane southwest of the fault against sub-greenschist-facies, less deformed rocks of Wrangellia. Multiple lines of evidence from this region indicate the Alexander terrane has been juxtaposed against Wrangellia along a southwest-dipping thrust fault. 40Ar/39Ar dates from muscovite, that grew during faulting or have been reset by motion along the Duke River Fault, range from 79 to 105 Ma, suggesting that ductile movement along the fault is at least as old as Cretaceous (Albian to Cenomanian). This phase of faulting is interpreted as the local expression of Cretaceous shortening which has been documented the length and width of the Cordillera. Cretaceous structures along the Duke River Fault are overprinted by brittle deformation that affects rocks as young as Miocene (or Pliocene?). The Duke River Fault appears to be accommodating present day transpression through uplift and reactivation of the thrust fault.
Flux of methane release and carbon dioxide sequestration at Winterhouse Canyon, Gros Morne, Newfoundland, Canada; a site of continental serpentinization
(Canadian Science Publishing, 2016-10-01) Morrissey, Liam; Morrill, Penny
We measured CO2, CH4, and N2O gas fluxes from a pool of ultra-basic water discharging from serpentinized rock in Winterhouse Canyon, Gros Morne, Newfoundland. The flux of CH4 released and CO2 sequestered were calculated to be 4.6 x 10-7 mol/m2min and 1.9 x 10-5 mol/m2min, respectively, while N2O concentrations showed little change. The net radiative forcing due to the changing concentrations of CO2 and CH4 during the sampling period was -0.21, suggesting that the ultra-basic pool in WHC has a net cooling effect on the atmosphere. Similarly, the net global warming potential over a time horizon of 100 years was -7, also suggesting a cooling of the atmosphere. Overall this study was the first to consider the impact of green houses coming into and out of an ultrabasic pool above serpentinized rock and demonstrated the need for more research on the net global impacts of serpentinization. Key words: Serpentinization, Greenhouse Gas, Flux, Chemical Enhancement
Parentage of Archean basement within a Paleoproterozoic orogen and implications for on-craton diamond preservation: Slave craton and Wopmay orogen, NW Canada
(Canadian Science Publishing, 2016-09-16) Ootes, Luke; Jackson, Valerie A; Davis, William J; Bennett, Venessa; Smar, Leanne; Cousens, Brian L
The Wopmay orogen is a Paleoproterozoic accretionary belt preserved to the west of the Archean Slave craton, NW Canada. Reworked Archean crystalline basement occurs in the orogen and new bedrock mapping, U-Pb geochronology, and Sm-Nd isotopic data further substantiate a Slave craton parentage for this basement. Detrital zircon results from unconformably overlying Paleoproterozoic supracrustal rocks also support a Slave craton provenance. Rifting of the Slave margin began at ca. 2.02 Ga with a second rift phase constrained between ca. 1.92 and 1.89 Ga, resulting in thermal weakening of the Archean basement and allowing subsequent penetrative deformation during the Calderian orogeny (ca. 1.88 to 1.85 Ga). The boundary between the western Slave craton and the reworked Archean basement in the southern Wopmay orogen is interpreted as the rifted cratonic margin, which later acted as a rigid backstop during compressional deformation. Age-isotopic characteristics of plutonic phases track the extent and evolution of these processes that left penetratively deformed Archean basement, Paleoproterozoic cover, and plutons in the west, and â rigidâ Archean Slave craton to the east. Diamond-bearing kimberlite occurs across the central and eastern parts of the Slave craton, but kimberlite (diamond-bearing or not) has not been documented west of ~114â °W. It is proposed that, while the crust of the western Slave craton escaped thermal weakening, the mantle did not and was moved out of the diamond stability field. The Paleoproterozoic extension-convergence cycle preserved in the Wopmay orogen provides a reasonable explanation as to why the western Slave craton appears to be diamond-sterile.
Seismic velocity model of the crust in the northern Canadian Cordillera from Rayleigh wave dispersion data
(Canadian Science Publishing, 2016-10-01) Ma, Shutian; Audet, Pascal
Models of seismic velocity structure of the crust in the seismically active northern Canadian Cordillera remain poorly constrained, despite their importance in the accurate location and characterization of regional earthquakes. On 29 August 2014, a moderate earthquake with magnitude MB 5.0 occurred in the Northwest Territories, Canada, ~100 km to the east of the Cordilleran Deformation Front, which generated high-quality Rayleigh wave data. We carefully selected 23 seismic stations that recorded the Rayleigh waves and divided them into 13 groups according to the azimuth angle between the earthquake and the stations; these groups mostly sample the Cordillera. In each group, we measured Rayleigh wave group velocity dispersion, which we inverted for one-dimensional shear-wave velocity models of the crust. We thus obtained 13 models that consistently show low seismic velocities with respect to reference models, with a slow upper and lower crust surrounding a relatively fast mid crustal layer. The average of the 13 models is consistent with receiver function data in the central portion of the Cordillera. Finally, we compare earthquake locations determined by the Geological Survey of Canada using a simple homogenous crust over a mantle half space with those estimated using the new crustal velocity model, and show that estimates can differ by as much as 10 km.
The Geology, Petrology and Geochronology of the Archean Côté Gold Large-Tonnage, Low-Grade Intrusion-Related Au(-Cu) Deposit, Swayze Greenstone Belt, Ontario, Canada
(Canadian Science Publishing, 2016-06-19) Katz, Laura Rachel; Kontak, Dan; Dubé , Benoït; McNicoll, Vicki
The Archean Côté Gold Au(-Cu) deposit is the first large gold deposit discovered in the Swayze greenstone belt of the Abitibi Subprovince. The deposit is a low-grade, large-tonnage type with a combined indicated and inferred resource of 8.65 M oz Au. The deposit is hosted by the Chester intrusive complex (CIC), a multi-phase, subvolcanic intrusion comprised of low-Al tonalite, diorite and quartz diorite, plus magmatic and hydrothermal breccia bodies. The age of the tonalite and dioritic phases is constrained at 2741 to 2739 ± 1 Ma using high-precision ID-TIMS U-Pb zircon geochronology. Although these phases are co-temporal and co-spatial, they appear to be petrogenetically unrelated. The CIC was emplaced into mafic metavolcanic rocks of the Arbutus Formation whose geochemistry reflects a back-arc environment. The tonalite of the CIC is coeval and co-genetic with the felsic to intermediate metavolcanic rocks of the Yeo Formation. Emplacement of the CIC into a shallow crustal level is inferred based on the incorporation of screens and inclusions of the Yeo Formation and is supported by the presence of textures in tonalite and dioritic rocks (e.g., granophyres, miarolitic cavities and pegmatites), as well as Al-in-hornblende geobarometry results of ≤1.3 ± 0.6 kbars. The CIC is petrologically similar to other subvolcanic, low-Al tonalite-trondhjemite-diorite intrusions that underlie VMS-type deposits and which themselves may contain syn-intrusion mineralization. Several geochemically unrelated dykes and deformation events crosscut and postdate the CIC.
Arctosaurus osborni, a Late Triassic archosauromorph reptile from the Canadian Arctic Archipelago
(Canadian Science Publishing, 2016-10-16) Sues, Hans-Dieter
Arctosaurus osborni is known only from an incomplete cervical vertebra from the Upper Triassic Heiberg Formation of Cameron Island, Nunavut, Canada. Re-examination of the unique specimen indicates that it represents an archosauromorph reptile, possibly from the clade Allokotosauria. To date, Arctosaurus osborni represents the sole record of Late Triassic continental tetrapods from Nunavut and the northernmost record of such animals anywhere in the world. Arctosaurus osborni est connu seulement d'une vertèbre cervicale incomplète provenant de la Formation Heiberg du Trias supérieur de l'île Cameron, Nunavut, Canada. Révision de l'exemplaire unique indique qu'il représente un reptile archosauromorphe, peut-être de le groupe Allokotosauria. À ce jour, Arctosaurus osborni représente le seul record des tétrapodes continentaux du Trias supérieur du Nunavut et le record du plus septentrional de ces animaux partout dans le monde.

Browse

Recent Submissions