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The Mesoproterozoic Husky Creek Formation is an interlayered redbed and basalt package that overlies a ca. 2.5 km thick, regionally extensive basaltic plateau linked to the 1.27 Ga Mackenzie Large Igneous Province. This succession provides an opportunity to study the interaction between contemporaneous fluvial sedimentation and flood basalt volcanism. The Husky Creek Formation is approximately 1900 m thick, consisting predominantly of fluvial channel and subordinate floodplain and eolian strata dominated by lithic detritus intercalated with basalt flows. U–Pb dating of detrital zircon grains collected from four stratigraphic levels in the Husky Creek Formation reveals two main age groupings: (1) a 1270 Ma peak attributed to the Mackenzie Large Igneous Province; and (2) Pre-1.6 Ga detrital zircon ages, which reflect sources from a broad region of northwestern Laurentia and are interpreted to be recycled from underlying sedimentary rocks of the Hornby Bay Basin. An upsection decrease in the proportion of ca. 1270 Ma zircon grains, coupled with increasing sandstone compositional maturity, reflects the expansion of the drainage basin during burial of a volcanic pile, with recycling becoming more dominant as the Husky Creek Formation accumulated. The Husky Creek Formation was deposited in the waning stages of the Mackenzie Igneous Event by west-flowing rivers into a geographically restricted basin above an extensive mafic volcanic plateau. This paper provides insight into fluvial basin development during the aftermath of one of Earth's largest igneous events. [ABSTRACT FROM AUTHOR]

Petrological modeling and geochronology (Lu–Hf garnet, U–Pb monazite, zircon, and titanite) for seven mid-amphibolite to granulite-facies metamorphic rocks in the Thelon tectonic zone (Ttz) provide new insights into the evolution of this orogen. A Grt-Sp-Sil diatexite records 2.01–2.00 Ga garnet and monazite growth during >830 °C contact metamorphism associated with voluminous convergent margin plutonism. The most widespread, 1.96–1.90 Ga metamorphism is associated with clockwise pressure (P)–temperature (T) paths, indicating it was driven by crustal thickening. Earlier (1.96–1.92 Ga) and lower temperature (630 °C–730 °C; 6–8 kbar) metamorphism in the eastern Slave craton contrast with ∼860 °C (7.5 kbar), 1.91–1.90 Ga diatexites in the central, Paleoproterozoic plutonic rock-dominated, core of the Ttz. These differences are interpreted to reflect lower vs. upper plate settings, respectively. A contribution of mantle heat is suggested by the counter-clockwise P–T path and 885 °C (5.7 kbar) conditions recorded by diatexite associated with c. 1.9 Ga peraluminous leucogranite that dominates a corridor along the Ttz–Rae craton boundary. A tectonic model is proposed wherein the Ttz evolved at an accretionary margin after rifting of Ttz microcontinent (mTtz) off the Rae craton at c. 2.2–2.1 Ga. Voluminous plutonism at 2.01–1.98 Ga formed via east-dipping subduction under mTtz. Following 1.97 Ga collision of the Slave craton and mTtz, west-dipping subduction generated 1.96–1.95 Ga plutonism in the composite mTtz-Slave upper plate. Collision of Rae craton at 1.95–1.94 Ga led to crustal thickening, widespread 1.91–1.90 Ga high-grade metamorphism and extensive crustal melting in the central Ttz. [ABSTRACT FROM AUTHOR]

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The internal metamorphic-plutonic zone of the middle Paleoproterozoic Wopmay orogen, northwestern Canadian Shield, exposes an oblique section through a prograde Buchan-type metamorphic sequence. New petrographic, petrologic, and geochronologic analyses of pelite and quartz arenite samples from the eastern margin of the internal zone quantify the evolving conditions and timing of metamorphism and enable the discriminant evaluation of competing tectonic models. Study of fabric development and mineral growth relationships indicates that prograde metamorphism occurred late within a craton-verging, crustal-shortening ("Calderian") deformation event. Phase equilibria modeling was used to calculate pressure-temperature (P-T) path segments and determine peak conditions from andalusite-muscovite grade at ~3.3 kbar and 575 °C to sillimanite-K-feldspar ± granitic leucosome grade at ~4.8-6.2 kbar and 670-745 °C. In situ monazite geochronology indicates that thermal peak metamorphic conditions were reached between 1878.6 ± 6.5 Ma and 1872 ± 9 Ma. Ages of detrital zircon within quartz arenite across the width of the metamorphic sequence document a diagnostic easterly Slave craton-Thelon tectonic zone derivation that links the metasedimentary rocks, including those previously considered to be "exotic" in a proposed tectonic klippe model for the internal zone, to the adjacent craton. Integration of these results with observations on the relatively low state of strain and the bracketing of a common (single) metamorphic field gradient for all garnet-bearing mineral zones confirm that the latter have preserved their prograde isogradic continuity from time of formation, and that the leading edge of a tectonic klippe consisting of rocks exotic to the Coronation margin does not traverse the study area. [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]

Field evidence, map compilation, geochemistry, geochronology, and potential field data document six intervals of Cretaceous magmatism in the central Sverdrup Basin. These are: (1) Hauterivian (ca. 130 Ma) vol-caniclastic deposition in the lower Isachsen Formation; (2) 126.6 ± 1.2 Ma (U-Pb zircon) gabbroic intrusion; (3) 120.8 ± 0.8 Ma (U-Pb baddeleyite) diabasic intrusion; (4) 105.40 ± 0.22 Ma (U-Pb detrital zircon) pyroclastic deposition at the top of the Invincible Point Member, Christopher Formation; (5) upper Albian (ca. 103 Ma) pillow and hydroclastic breccia in the upper Christopher Formation; and (6) uppermost Albian (ca. 101 Ma) volcanic breccia and scoria in the Hassel Formation. Whole-rock geochemical data show that these magmatic rocks are similar to previously documented High Arctic large igneous province tholeiitic basalts, but analyses of fresh glass in tuffs reveal evolved ferroandesite to dacite compositions not recorded in whole-rock data. Approximate ages of saucer-shaped sills inferred from the relationship of sill width to depth of emplacement suggest at least three intervals of sill emplacement between 130 and 120 Ma. The new data show that volcanism in the Sverdrup Basin was of greater spatial extent, and that magmatism occurred more frequently, than was previously recognized. Comparison of the new central Sverdrup Basin data and interpretations with other data sets from the Sverdrup Basin, Svalbard, and Franz Josef Land suggests that High Arctic large igneous province magmatism occurred over a more extended period of time in the central Sverdrup Basin than in other regions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zircon from lower crustal xenoliths record complex crust formation histories. [•] Cores record crust formation at ca. 3.5–2.6Ga and ca. 2.0–1.9Ga thermal reworking. [•] Metamorphic rims record regional lower crustal reworking at ca. 1.75Ga. [•] Lower crustal reworking likely resulted from 1.75Ga magma underplating. [•] Intracrystalline Pb-disturbance related to 1.75Ga granulite-facies metamorphism. [Copyright &y& Elsevier]

The timing of Sveconorwegian high-grade metamorphism is evaluated in the four lithotectonic units / terranes exposed in the Sveconorwegian belt in South Norway. U-Pb, Th-Pb and Re-Os data were obtained from 21 samples of Mesoproterozoic ortho- and paragneisses. In the Bamble Terrane, SIMS monazite U-Pb data constrain peak amphibolite- to granulite-facies metamorphism between 1137 ±1 and 1127 ±6 Ma, and unroofing at 1107 ±9 Ma. In the Kongsberg Terrane, a molybdenite Re-Os date at 1112 ±4 Ma and a monazite U-Pb date at 1092 ±1 Ma bracket amphibolite-facies metamorphism. In the Idefjorden Terrane, west of the Oslo rift, a pulse of Gothian metamorphism at 1539 ±8 Ma and three pulses of Sveconorwegian metamorphism at 1091 ±18 Ma, 1052 ±4 to 1043 ±8 Ma and 1024 ±9 Ma are recorded by monazite, zircon and titanite data. Amphibolitefacies metamorphism peaked at 1052 ±4 Ma in the kyanite field (1.00-1.17 GPa, 688-780 °C). At the boundary between the Idefjorden and Telemarkia Terranes, SIMS zircon U-Pb data constrain amphibolite-facies metamorphism between 1012 ±7 and 1008 ±14 Ma and provide a maximum age for shearing along the Vardefjell Shear Zone between these two terranes. Amphibolite-facies metamorphism in the Telemarkia hanging wall of the Vardefjell Shear Zone is coeval at 1014 ±1 Ma. In the Suldal Sector of the Telemarkia Terrane, monazite data yield an age of 1005 ±7 Ma for amphibolite- facies migmatitization. In the Rogaland-Vest Agder Sector of the Telemarkia Terrane, paired U-Pb and Th-Pb ID-TIMS monazite analyses date monazite growth to have been between 1013 ±5 and 980 ±5 Ma during M1 intermediate-pressure regional metamorphism, and between 927 ±5 and 922 ±5 Ma during M2 low-pressure high- to ultrahigh-temperature metamorphism. SIMS monazite dates at 1032 ±5 and 990 ±8 Ma in a granulite, situated outside the area affected by M2 metamorphism, demonstrate granulite-facies conditions during M1 metamorphism. Available data show that the four terranes in South Norway have distinct metamorphic histories. The Bamble and Kongsberg Terranes show evidence for early-Sveconorwegian metamorphism between 1140 and 1080 Ma. The Idefjorden Terrane, though locally affected by this early metamorphism, was mainly reworked by medium to high-pressure metamorphism between 1050 and 1025 Ma. The Telemarkia Terrane was reworked later between c. 1035 and 970 Ma. A high-temperature metamorphic phase at 930-920 Ma is specific for the Telemarkia Terrane and is related to post-collisional intrusion of the Rogaland anorthosite-mangerite-charnockite (AMC) Complex. [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]

Secondary-ion mass spectrometry (SIMS) U–Pb and trace element data are reported for zircon to address the controversial geochronology of eclogite-facies metamorphism in the Lindås nappe, Bergen Arcs, Caledonides of W Norway. Caledonian eclogite-facies overprint in the nappe was controlled by fracturing and introduction of fluid in the Proterozoic—Sveconorwegian—granulite-facies meta-anorthosite-norite protolith. Zircon grains in one massive eclogite display a core–rim structure. Sveconorwegian cores have trace element signatures identical with those of zircon in the granulite protolith, i.e. 0.31≤Th/U≤0.89, heavy rare earth element (HREE) enrichment, and negative Eu anomaly. Weakly-zoned to euhedral oscillatory-zoned Caledonian rims are characterized by Th/U≤0.13, low LREE content (minimum normalized abundance for Pr or Nd), variable enrichment in HREE, and no Eu anomaly. A decrease of REE towards the outermost rim, especially HREE, is documented. This signature reflects co-precipitation of zircon with garnet and clinozoisite in a feldspar-absent assemblage, and consequently links zircon to the eclogite-facies overprint. The rims provide a mean 206Pb/238U crystallization age of 423±4 Ma. This age reflects eclogite-forming reactions and fluid–rock interaction. This age indicates that eclogite-facies overprint in the Lindås nappe took place at the onset of the Scandian (Silurian) collision between Laurentia and Baltica. [ABSTRACT FROM AUTHOR]

Investigates the Zircon Uranium-Lead geochronology in the Bergen arc eclogites in western Norway. Implications for the pre-Scandian evolution of the Caledonides; Formation of eclogites in an orogenic belt; Evaluation of the pre-collision history of eclogite terranes.

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: TIMS and SHRIMP U–Pb zircon geochronology of selected parts of the Puncoviscana Formation suggest its deposition took place mainly during the Early Cambrian, coeval with 540–535Ma calc-alkaline Pampean arc volcanism mainly preserved as tuff beds in the oldest identified parts of this unit. Syn- to post-tectonic plutons constrains the Tilcarian–Pampean orogeny to have occurred between ca. 530Ma and deposition of the unconformably overlying Middle-Upper Cambrian Meson Group. Deposition of the Puncoviscana Formation continued after the onset of the Tilcarian–Pampean orogeny. We propose that the Puncoviscana Formation rocks older than 530Ma were deposited in the arc-trench gap of the west-facing Pampean arc and/or the associated trench, whereas the rocks younger than 530Ma were deposited in a syn-collision foreland basin. The Puncoviscana Formation rocks were progressively assembled into a west-younging accretionary complex, consistent with the style of deformation and low-grade metamorphism. The age of the syn-collision plutons (≤530Ma) suggest the foredeep deposits record the transition from trench to foreland basin, due to arrival of the Arequipa-Antofalla block at the west-facing trench at ca. 530Ma. Our geochronological and Pb-isotope investigations suggest that the Arequipa-Antofalla terrane was a coherent, ribbon-shaped crustal block that also included the western part of the Pampia terrane. A compilation of existing U–Pb zircon studies suggests that the Pampean arc extended along the length of the proto-Andean margin of West Gondwana, represented by the previously amalgamated Amazonia and Rio de La Plata cratons, and probably was initiated during the late Ediacaran after 600Ma. Following earlier workers, we reaffirm that the Arequipa-Antofalla block was originally separating Laurentia and Amazonia in Rodinia. It probably rifted from Laurentia during the Ediacaran between 600 and 570Ma, following an earlier departure of Amazonia (∼650Ma?). The separation of Arequipa-Antofalla from Amazonia and Laurentia opened the Puncoviscana and Iapetus oceans respectively. [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]

Highlights: [•] We identify a ca. 830–810Ma back-arc basin in the southeastern Yangtze Block. [•] The basalts of Shaojiwa Formation might have been derived from a slightly depleted mantle source metasomatized by fluid. [•] The rhyolites of Shaojiwa Formation can be explained by fractional crystallization of the basaltic magma. [•] The precursor magma of the amphibolites might have been originated from an N-MORB source modified by slab-derived fluids. [•] Widespread Neoproterozoic igneous rocks (850–810Ma) in the Jiangnan Orogen most likely occurred in back-arc environment. [Copyright &y& Elsevier]