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U-Pb ages of zircon from bentonites within the upper Cretaceous Bastion Ridge and Kanguk formations, Sverdrup Basin, provide constraints on sedimentation rates, biostratigraphic correlations, timing of Oceanic Anoxic Event 2 (OAE2) in the High Arctic, and the late magmatic history of the High Arctic Large Igneous Province (HALIP). A late Cenomanian to early Turonian age for the base of the Kanguk Formation is confirmed that supports correlations of the global OAE2 in the High Arctic. Sedimentation rates varied from 19 m Ma-1 between 93 and 91 Ma to 26 m Ma-1 between 91 and 83 Ma at Axel Heiberg Island. At Ellef Ringnes Island, the lower Kanguk Formation records high rates of ~70 mMa-1 between 94 and 93 Ma, which decrease to rates comparable to those of the upper Axel Heiberg section. Differences in sedimentation rates may reflect differences in setting prior to the major transgression in the latest Cenomanian to early Turonian. The timing of Arctic occurrences of the Scaphites nigricollensis and Scaphites depressus ammonite zones is shown to be broadly comparable to that of lower-latitude occurrences within the Western Interior Seaway. An eruption frequency of 0.5-2.5 Ma characterizes the late alkaline phase of HALIP magmatism. Volcanic bed thicknesses of 10-50 cm suggest ash transport distances of less than 1000 km. Long-lived volcanic centres, in the area of the Alpha Ridge, northern Ellesmere Island or northern Greenland, were the likely source of volcanic ash over a period of 10-15 Ma. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Wopmay orogen is modeled as a simple arc-continent collision involving the Archean Slave craton and an enigmatic continental arc terrane termed the Hottah terrane. Hottah is a composite terrane that includes a juvenile 2.6-2.1 Ga basement and a younger 1.93-1.90 Ga continental arc. The extent and crustal age structure of the terrane is poorly known which limits interpretations as to its origin, and eventual role in the development of the orogen. Multi-isotopic (U-Pb, Hf, O) analyses of detrital zircon from rocks of the Hottah terrane and its cover sequence are used to indirectly evaluate its age and crustal characteristics. The data confirm that ca 2.6-2.1 Ga crust is an important component of the terrane but Hf isotopic data indicate mostly non-juvenile compositions consistent with recycled Neoarchean crust sources. Ages of detrital zircon are distinct from those expected of the Slave craton but are similar to adjacent 2.0-1.90 Ga Paleoproterozoic terranes of northwestern Laurentia. The similarity to terranes such as the Ksituan/Buffalo Head and Taltson-Thelon magmatic zones, south and east of the Wopmay Orogen indicate that Hottah could represent a terrane that initially evolved adjacent to the earliest assembled parts of the Nuna continent between 2.0 and 1.9 Ga, and was rifted prior to the collision with the Slave margin that produced the Calderian orogeny. [ABSTRACT FROM AUTHOR]

Abstract: New geological and geochronological data from the MacQuoid supracrustal belt and the geometrically overlying Cross Bay plutonic complex highlight a distinct tectonothermal evolution for the northwestern part of the Hearne domain (northwestern Hearne subdomain), compared with adjacent areas in the Rae and Hearne, of the western Churchill Province, Canada. The supracrustal and intrusive rocks dominantly formed in the Neoarchean between <2.74 and 2.65Ga, with minor 2.61Ga granite, and experienced a polycyclic Neoarchean and Paleoproterozoic deformational history. The dominant tectonic fabric throughout much of the area formed between 2.56 and 2.50Ga, including the Big Lake shear zone, a granulite-facies mylonite zone that juxtaposed the Cross Bay plutonic complex over the MacQuoid supracrustal belt at 2.50Ga. The fabric transposed earlier fabrics whose age is poorly constrained. Additional tectonic events occurred during the Paleoproterozoic at 1.90Ga, and 1.84–1.81Ga. Differences between the geological histories of the northwestern part of the Hearne domain relative to the immediately adjacent Rae and Hearne areas highlight the tectonically distinct character of the northwestern Hearne subdomain. [Copyright &y& Elsevier]

The Eagle Plain region, located in the northeastern Yukon Territory, Canada, forms a northern segment of the Cretaceous Western Interior Sea. Its preserved mid-Cretaceous strata (Whitestone River Formation and Eagle Plain Group) document an active structural regime, sea-level fluctuations, paleoecosystem changes and the paleogeographic evolution south of the gateway to the Polar Sea. This study integrates foraminiferal assemblages recovered from two wells (Molar P-34 and Ellen C-24) and one Late Albian bentonite age with well log signatures and previously established outcrop data. The proposed biostratigraphic framework correlates well between both wells and with the fauna observed in outcrops. Three biostratigraphic zones are recognized allowing for regional correlations; the Early Albian Gaudryina tailleuri Zone, the Middle to early Late Albian Gaudryina canadensis Zone, and the latest Albian Miliammina manitobensis Zone. A new 206 Pb/ 238 U age of 105.56 ± 0.25 Ma places the upper Whitestone River Formation into the Late Albian. Foraminiferal morphogroups and their relative proportions allow for paleoenvironmental reconstruction, including oxygen and nutrient conditions. The Ellen well represents deposition in a fully marine, well oxygenated proximal shelf setting during the Early to early Late Albian, resulting in the Whitestone River Formation. The Molar well represents a deep water, offshore setting with increased accommodation space marked by an increase in tubular suspension feeders, demonstrating a northwestward deepening of the basin. Foraminiferal assemblages of the Albian Whitestone River Formation reflect the widely recognized depositional cycles of the Western Interior Sea (Moosebar, Hulcross, Joli Fou and Mowry seas). During Albian time the northern gateway between the Polar and Western Interior seas was widely inundated, contrasting with an either short lived closure or severely restricted phase during the Albian/Cenomanian boundary interval. [ABSTRACT FROM AUTHOR]

Abstract: Monazite can be used for U–Pb and Th–Pb dating of a wide variety of rocks and geological processes, particularly metamorphism. In many instances ion microprobe analysis is the preferred method for dating monazite, combining good analytical precision with μm-scale spatial resolution. However, ion microprobe dates can be compromised by matrix effects on the ionisation efficiencies of different secondary ionic species, which can bias monazite Pb+/ThOn + and Pb+/UOn + data by as much as ∼40% and ∼30%, respectively, for known monazite compositions. These effects appear to be entirely attributable to the sputtering process, in which case similar effects exist in data from all ion probes. The effects on data ratios are modified, sometimes exacerbated or reversed, when data are subjected to the correlation-based Pb/Th and Pb/U calibrations that are now commonly used. One-dimensional calibrations of 206Pb+/270[UO2]+ and 208Pb+/264[ThO2]+ are recommended. Corrections derived from data for a suite of reference materials with diverse compositions can reduce biases in 208Pb/232Th ages to <∼2% and in 206Pb/238U ages to <∼1%. The matrix effects come predominantly from variations in the concentrations of Th, U, Pb, light rare earth elements (LREE) and Y. La/Ce is an effective proxy for REE composition in many monazites, but for some monazites it would also be necessary to monitor Nd. Matrix corrections can be applied without measuring all LREE, using ion probe data alone. Other interacting data complications, such as Pb/Pb fractionation and an isobar at 204Pb+, can be addressed without iterative data reduction. [Copyright &y& Elsevier]

[Display omitted] • Garnet-hosted xenotime and gold are dated at ca. 1827 Ma • Early gold veins are metamorphosed to amphibolite facies (505–689 °C) • New ages for gold mineralization also post-date metamorphism by up to 80 Myr • Post-orogenic gold mineralization is coeval with biotite cooling ages (ca. 1746 Ma) • Exhumation of the Trans-Hudson orogen triggered gold mineralization Metamorphic devolatilization is thought to be the critical process that can liberate gold from amphibolite facies source rocks to form orogenic gold deposits. However, a growing number of studies demonstrate that orogenic gold deposits are the product of multiple hydrothermal stages over 10 s to 100 s of Myr rather than one metallogenic event. Herein we report new geochronology results for orogenic gold deposits hosted within the Paleoproterozoic Lynn Lake greenstone belt (Manitoba, Canada) to address the knowledge gap. Garnet-hosted xenotime crystals, which occur in a folded pyrite veinlet with gold, yield a weighted average 207Pb/206Pb date at 1827 ± 8 Ma. This new and more precise age demonstrates that the earliest auriferous fluids at the MacLellan gold deposit coincided with the rapid burial of ca. 1836 Ma sedimentary rocks before regional metamorphism. New garnet-biotite geothermometry results further demonstrate that the earliest auriferous veins were preserved despite being metamorphosed to amphibolite facies conditions (505–689 °C). The peak metamorphic mineral assemblage is overprinted by: (1) the main xenotime- and gold-bearing deformation fabric (S 2 ; 1790–1827 Ma); (2) an overprinting xenotime- and monazite-bearing S 3 fabric that is also associated with gold-rich arsenopyrite (1769–1790 Ma); and (3) chlorite-hosted xenotime and gold (1747 ± 12 Ma) that are coeval with the oldest U-Pb apatite dates (1691–1740 Ma) and a prominent mode of 40Ar/39Ar biotite dates at ca. 1746 Ma. We suggest that the post-orogenic gold events are incompatible with the standard devolatilization model because they post-date subduction and peak-metamorphism by up to 80 Myr. Instead, the new geochronological results suggest that gold deposition at the MacLellan deposit was linked to burial and the subsequent exhumation of chemically reactive trap rocks through favourable temperature windows that allowed gold transport as sulphide complexes. Exhumation and far-field tectonics are interpreted as the most likely drivers of post-orogenic auriferous fluids rather than regional metamorphism and active subduction. This revised mineral systems model provides an explanation for the high prospectivity of high- and low-temperature mineral assemblages and suggests that mineral exploration should focus on the earliest ore-forming structures that are reactivated during multiple stages of orogenesis. [ABSTRACT FROM AUTHOR]

Abstract: Cretaceous sediments in the Northern Interior Plains are widespread and their interbasinal lithostratigraphic correlations indicate several regional unconformities that require biostratigraphic confirmation. This study proposes a new zonation based on benthic foraminifera utilising the reference section for the Albian to Turonian Arctic Red and Trevor formations located along the Hume River in the Peel Plateau region (Northwest Territories). A new absolute age date of 107.0±1.9Ma from a bentonite extends the biostratigraphic range of the Early Albian Quadrimorphina albertensis Zone into the Middle Albian. Integration of the new temporal framework with detailed sedimentological observations provides an interpretation of the dynamic depositional history for this northern region of the Western Interior Seaway (WIS). Cretaceous strata in the Peel Plateau record deposition of the initial transgression of the WIS in two pulses of relative sea-level rise (Martin House Formation) and subsequent offshore marine sedimentation in a deep foreland basin (Arctic Red Formation). The global eustatic sea-level minimum at the Albian–Cenomanian boundary and renewed uplift of the Keele Arch impacted palaeogeography in this region with previously unnoticed subaerial exposure and palaeosol development. This unconformity can be correlated to the east into the Mackenzie Plain. Transgression brings anoxic bottom waters during the Early Cenomanian (Slater River Formation) that result in an interval almost barren of foraminifera. During the Turonian, a time of high eustatic sea-level, the study area marks a relatively shallow site where pulses of prograding shorelines are recorded in upward shallowing parasequences bound by pebble lags overlain by flooding surfaces (Trevor Formation). East of the Peel Plateau in the Mackenzie Plain area, an unconformity separates Albian Arctic Red from ?Upper Cenomanian–Turonian strata, there named the Slater River Formation. In order to recognise the significant unconformity associated with the loss of Albian foraminifera and the angular unconformity observed in seismic profile, we propose the use of the Slater River Formation to describe the strata bound by the pisoidal ironstone and the first metre-plus sandstone bed marking the base of the interbedded mudstones and sandstones of the overlying Trevor Formation. The Hume River section is proposed as the type section for the Slater River Formation. [Copyright &y& Elsevier]

• Provenance of Meall Dearg Formation (Torridonian succession) investigated in detail. • Detrital-zircon U-Pb ages compared to compilation from Lewisian Gneiss Complex. • Provenance from Lewisian Gneiss Complex resolved at the terrane scale. • Fluvial-aeolian sediment mixing investigated by detrital-zircon age distributions. • Meall Dearg Formation represents late stage of a rift basin within Laurentia. The Meall Dearg Formation is a 1.2 Ga fluvial-aeolian sandstone exposed in the northwestern Highlands of Scotland, and represents one of the least studied rock units in the Torridonian succession, especially in terms of sedimentary provenance. Three hundred and nine detrital zircon grains were analysed from four samples of the Meall Dearg Formation using sensitive high-resolution ion microprobe, allowing for its provenance to be resolved at the terrane scale. Ages range from c. 3,100 to c. 1,750 Ma, with dominant proportions between c. 2,900 and c. 2,650 Ma, and subordinate fractions of c. 2,500 Ma and c. 1,900 Ma. U-Pb protolith-zircon ages from eight previous studies across the Lewisian Gneiss Complex were compiled and compared to detrital-age distributions of the Meall Dearg Formation. Strong similarities in age trends and palaeocurrent data corroborates the hypothesis of sedimentary provenance from the Lewisian Gneiss Complex. Detritus was prevalently derived from the Rhiconich and Gruinard terranes, and subordinately from the Assynt, Gairloch (including the Loch Maree Group and Ard Gneiss), and Ialltaig terranes. Age distributions from the fluvial and aeolian samples show near-matching distributions, indicating sediment transfer between adjacent depositional environments, and possibly derivation from similar source regions. The Meall Dearg Formation, part of the Stoer Group, is postulated to record the overfilling stage of a rift basin near the eastern flank of the Columbia Supercontinent at c. 1.2 Ga. Critical comparisons can be drawn between the Stoer Group and Gardar Rift of southern Greenland, based on their age, palaeogeography, and patterns of rift-basin development. [ABSTRACT FROM AUTHOR]