Superior Province Research Articles

Petrotectonics of chromite in Archean anorthosite-bearing layered intrusions: Implications for Archean tectonics

The origin of Archean layered anorthosite-gabbro-peridotite-chromitite intrusions and their relationship to the extant tectonic style on early Earth have been controversial for decades. The geochemistry and microtextures of chromite in Archean anorthosite-bearing layered intrusions have major implications for these issues, and the “anorthosite problem” posited by N.L. Bowen in 1917, because the chromite is highly refractory and resistant to chemical modification, and thus it preserves significant petrogenetic and tectonic information. This study presents a comparison of chromites from the Archean anorthosite-bearing layered intrusions of the Fiskenæsset complex (ca. 2.97 Ga) in southwest Greenland and the Mayville intrusion and Bird River sill (ca. 2.74 Ga) in the Superior Province of Canada. Amphibole occurs as secondary minerals and inclusions within the chromites, revealing a hydrous parental magma, which hints at a subduction zone setting. Moreover, the mineral chemistry of chromite from the non-anorthositic components of these layered complexes shows that the Fiskenæsset complex formed in an intra-oceanic arc setting, while the Mayville intrusion and Bird River sill formed in a continental back-arc setting. However, the chromites derived from the anorthosites from all the complexes define a hitherto unclassified category of chromite chemistry, for both oceanic-type and continental margin−type arcs. Our results suggest that the style of modern plate tectonics (intra-oceanic arcs and continental arcs) was present in the Archean and formed sufficiently thick continental crust to form continental arcs by the Mesoarchean−Neoarchean.

Corrigendum to “Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry” [Precambrian Res. 418 (2025) 107705

Corrigendum to “Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry” [Precambrian Res. 418 (2025) 107705

Deformation Controlled Fluid Mass‐Transfer Processes in Ancient Orogens

AbstractDespite abundant empirical evidence, the details of coupled deformation and mass transfer processes within a framework of the crustal architecture of ancient orogens remains enigmatic. Geophysical imaging of the Larder Lake‐Cadillac deformation zone, a well‐endowed crustal‐scale fault system in the Superior Province of the Canadian Shield, characterizes the crustal architecture and fault geometry of the system through the lower crust. By comparing the geophysically determined structure of the Larder Lake‐Cadillac deformation zone to stress changes induced by Archean (peak orogeny) rupture of the fault system, we show domains of earthquake‐triggered deformation coincide with the geophysically imaged low resistivity zones. These low resistivity zones likely formed due to Archean mineral bearing fluid migration from underlying fertile source zones to downstream (shallower) crustal reservoirs and, ultimately, near surface traps. The multi‐disciplinary approach identifies the syntectonic mass‐transfer processes and mineral bearing fluid pathways, providing an interpretive framework for unraveling the geophysical manifestation of the deformation controlled processes responsible for upflow of metalliferous fluids that may result in ore deposit formation in collisional orogens.

Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry

Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry

Modeling and scientific analysis of pediatric medication evaluation based on MDM-DEA-Malmquist model: construction of health management in pediatrics in developing countries

BackgroundThe developing countries represented by China have huge population potential and child population. However, due to economic and social development constraints, pediatrics need help regarding resources and technology. The level of pediatric medical care remains inadequate.MethodsThis article constructs an MDM matrix framework for the pediatric medical nursing level. Combining the lean model theory, the key indicators of children's medical care are analyzed. Thus, it helps medical institutions scientifically evaluate and guide pediatric nursing. Based on the linkage extension of the MDM model and the DEA-Malmquist model, an evaluation system was established to reflect the current situation of pediatric drug use in China. The study used provincial indicator data on pediatric medication in China from 2015 to 2021.ResultsWe found that indicators such as physician literacy, health records, child status, and parental awareness were the most important under different medication cycles and goals. The importance of pre-administration evaluation was as high as 53.5%, and the importance of post-administration evaluation was only 13.7%. The efficacy of pediatric medication in developed provinces was significantly optimized. The input–output structure of pediatric medication in superior provinces was consistent with the feedback sequence of the MDM matrix.ConclusionsThis indicates that the evaluation results of the MDM matrix have guiding significance for optimizing pediatric medication efficacy. This paper aims to help developing countries establish an optimized pediatric medication evaluation system and improve the pediatric healthcare environment.

Crystallization conditions and magmatic–hydrothermal evolution of syenite dykes spatially associated with gold mineralization: the example of the Dolodau syenite–carbonatite complex, Abitibi greenstone belt

The Dolodau syenite–carbonatite complex is one of several syntectonic intrusions of the Abitibi greenstone belt, Superior craton, Canada. It formed during the syntectonic period, which is the main deformation stage leading to craton stabilization. Such magma can be involved in intrusion-related gold systems (IRGS) and be overprinted by orogenic gold systems (OGS), with IRGS and OGS being the main gold mineralizing systems of the syntectonic period. Determining whether magmas of the syntectonic period can transport enough gold to fertilize the upper crust requires insights into the crystallizing conditions and the volatile content of these magmas. Retrieving such data from the altered rocks generally encountered in mineralized areas is best accomplished by accumulating case studies. This study focuses on the Au–W–Ag mineralization spatially associated with the Dolodau intrusive complex to evaluate its fertility for Au. Using field relationships, petrographic observations, whole rock geochemical analyses, and mineral chemistry (titanite, apatite), we show that Dolodau is a carbonatite–syenite–granodiorite intrusive suite that crystallized rapidly at shallow depth in an active fault zone. The magma was S- and Cl-poor according to apatite chemistry, and it was likely incapable of transporting a significant amount of gold through the crust. It is concluded that the Dolodau Au–W–Ag mineralization is an OGS related to a major northeast–southwest-oriented fault.

Geochronology and geochemistry of deeply buried basement along the western Superior Craton and eastern Trans-Hudson Orogen (North America)

The Paleoproterozoic Trans-Hudson Orogen of North America resulted from the amalgamation of the Wyoming, Hearne, Sask, and Superior cratons. Previous work has constrained the timing of terminal collision of the Hearne, Sask, and Superior cratons to ca. 1.83−1.80 Ga (Canadian Shield), and the Wyoming and Superior cratons to 1.78−1.72 Ga (Black Hills, South Dakota, USA). More than 1200 km separate the Canadian Shield and Black Hills, between which there is no crystalline basement exposure due to Phanerozoic sedimentary cover, and limited data exist. This study presents U-Pb zircon geochronologic, major and trace element geochemical, and isotopic (εHf zircon and εNd whole-rock) data from two basement drill cores ∼3000 m deep collected along the western edge of the Superior Craton and eastern margin of the Trans-Hudson Orogen overprint, between the Canadian Shield and Black Hills. The western core contains ca. 1.83 Ga mafic gneiss with juvenile isotopic [εHf(i) and εNd(i)] geochemical signatures and an amphibolite-grade metamorphic overprint. The eastern core contains ca. 2.7 Ga granitic gneiss with trace element and juvenile isotopic geochemical signatures that are consistent with granitoids from the western Superior Craton. Paleoproterozoic (ca. 1.79−1.77 Ga) granitoid intrusions occur in both cores that display trace element signatures suggestive of origination in a continental arc setting. Isotope geochemistry plus inherited zircon populations indicate that intrusive granitoids are mixtures of juvenile Paleoproterozoic mantle and recycled crustal material. The ca. 1.79−1.77 Ga granitic magmatism observed falls chronologically between the terminal Hearne, Sask, and Superior collision and the Wyoming and Superior collision, and the data presented herein represent a step toward better understanding the buried southern Trans-Hudson Orogen.

Paleomagnetic evidence for Neoarchean plate mobilism

Plate tectonics is a unique feature of Earth, but its proposed time of initiation is still controversial, with published estimates ranging from ca. 4.2 to 0.7 Ga. Paleomagnetic data can provide a robust argument for one essential aspect of plate tectonics: large-scale relative lateral motions of distinct, rigid crustal blocks. Previously, the oldest relative horizontal motion between two or more blocks was constrained to a broad age interval of ca. 2.7–2.17 Ga using paleomagnetic data. In this study, we obtain a robust ca. 2.48 Ga paleomagnetic pole from Wyoming craton. Combining this result with the ca. 2.7–2.17 Ga apparent polar wander paths from Wyoming and Superior cratons, we suggest that they assembled during ca. 2.7–2.5 Ga and remained directly juxtaposed until ca. 2.17 Ga. Tectonostratigraphic data and geological proxies also suggest Wyoming and Superior collided at ca. 2.6 Ga. The results provide strong evidence for relative horizontal motion between crustal blocks during the Neoarchean. Together with other tectonic proxies, the data suggest plate mobilism in operation prior to 2.5 Ga.

The geology of the Greenstone orogenic gold deposit, Geraldton, Ontario, Canada: Structural controls, mineralogy, geochemistry, and geochronology

The geology of the Greenstone orogenic gold deposit, Geraldton, Ontario, Canada: Structural controls, mineralogy, geochemistry, and geochronology

Living in Their Heyday: Iron-Oxidizing Bacteria Bloomed in Shallow-Marine, Subtidal Environments at ca. 1.88 Ga.

The majority of large iron formations (IFs) were deposited leading up to Earth's great oxidation episode (GOE). Following the GOE, IF deposition decreased for almost 500 Myr. Subsequently, around 1.88 Ga, there was widespread deposition of shallow-water granular iron formations (GIF) within a geologically short time interval, which has been linked to enhanced iron (Fe) supply to seawater from submarine hydrothermal venting associated with the emplacement of large igneous provinces. Previous studies of Fe-rich, microfossil-bearing stromatolites from the ca. 1.88 Ga Gunflint Formation on the Superior craton suggested direct microbial oxidation of seawater Fe2+ (aq) by microaerophilic, Fe-oxidizing bacteria (FeOB), as a driver of GIF deposition. Although Fe-rich, microfossil-bearing stromatolites are common in 1.88 Ga GIF deposits on several cratons, combined paleontological and geochemical studies have been applied only to the Gunflint Formation. Here, we present new paleontological and geochemical observations for the ca. 1.89 Ga Gibraltar Formation GIFs from the East Arm of the Great Slave Lake, Northwest Territories, Canada. Fossil morphology, Rare Earth element (REE) concentrations, and Fe isotopic compositions support Fe oxidation by FeOB at a redoxcline poised above the fair-weather wave base. Small positive Eu anomalies and positive εNd (1.89 Ga) values suggest upwelling of deep, Fe-rich, hydrothermally influenced seawater. While high [Fe2+ (aq)] combined with low atmospheric pO2 in the late Paleoproterozoic would have provided optimal conditions in shallow oceans for FeOB to precipitate Fe oxyhydroxide, these redox conditions were likely toxic to cyanobacteria. As long as local O2 production by cyanobacteria was strongly diminished, FeOB would have had to rely on an atmospheric O2 supply by diffusion to shallow seawater to oxidize Fe2+ (aq). Using a 1-D reaction dispersion model, we calculate [O2(aq)] sufficient to deplete an upwelling Fe2+ (aq) source. Our results for GIF deposition are consistent with late Paleoproterozoic pO2 estimates of ~1%-10% PAL and constraints for metabolic [O2(aq)] requirements for modern FeOB. Widespread GIF deposition at ca. 1.88 Ga appears to mark a temporally restricted episode of optimal biogeochemical conditions in Earth's history when increased hydrothermal Fe2+ (aq) sourced from the deep oceans, in combination with low mid-Paleoproterozoic atmospheric pO2, globally satisfied FeOB metabolic Fe2+ (aq) and O2(aq) requirements in shallow-marine subtidal environments above the fair-weather wave base.

Reply to the comments on “Late Archean sedimentary basins in the northeastern Superior Province, Canada: Plume-generated crustal tears or syn-convergent accretionary belts?” of Svojtka et al. (2024)

Reply to the comments on “Late Archean sedimentary basins in the northeastern Superior Province, Canada: Plume-generated crustal tears or syn-convergent accretionary belts?” of Svojtka et al. (2024)

The Holleford structure: Insights into the pre- and post-impact geology of the Frontenac Terrane, Canada

A multi-chronometric investigation has been conducted on the ∼2.0-km-diameter Holleford impact structure of Ontario, Canada. In situ triple quadrupole laser ablation−inductively coupled−mass spectrometry U-Pb and Rb-Sr geochronology, along with (U-Th)/He thermochronology, have been applied to multiple mineral phases from impact melt-bearing breccias and overlying sedimentary units. Impact-induced resetting is absent in all three isotopic systems. While Holleford’s small size resulted in insufficient heating to reset geochronometers during impact, our investigation has defined a more detailed pre- and post-impact geologic setting within the Precambrian basement and overlying Paleozoic lithologies. Target rock age determinations include those associated with the Proterozoic Frontenac Terrane. These are manifest as the Rigolet (1004 ± 5 Ma, U-Pb apatite dating) and Ottawan (1074 ± 12 Ma, Rb-Sr biotite dating) phases of the Grenville Orogeny. Pre-Grenville ages associated with the Penokean (1806 ± 46 Ma, apatite dating) and the Shawinigan (1184 ± 8 Ma, U-Pb titanite dating; 1134 ± 21 Ma, U-Pb zircon dating) orogenies are also retained. A Paleoproterozoic age records Superior Province tectonometamorphism (2421 ± 97 Ma, U-Pb zircon dating). Dated post-impact events include dolomitization associated with Silurian marine transgression (430 ± 14 Ma, U-Pb dolomite dating) and regional K-metasomatism of Mississippian age (346 ± 5 Ma, U-Pb titanite dating). Extremely young (U-Th)/He ages (27−3 Ma) were obtained from planar fractured and recrystallized apatite, which we interpret to be the result of impact-induced diffusion domain reduction. This, combined with low-temperature heating due to burial, significantly limited He retention. Stratigraphic constraints place the Holleford impact event at ca. 458 Ma, close to the Darriwilian−Sandbian boundary of the Ordovician. This age indicates that Holleford may be part of the Late Ordovician group of terrestrial impact craters related to L-chondrite parent breakup.

The S3 orogenic gold targeting algorithm: A case study from the Timmins gold camp, Ontario, Canada

Mineral exploration targeting of orogenic gold deposits is challenging, especially in concealed terrains. To meet this challenge, a practical orogenic gold targeting method using structural complexity (SC), self-organizing map (SOM) and supervised deep neural network (SDNN) is proposed. As orogenic gold deposits are structurally controlled, the use of high-resolution aeromagnetic data in order to delineate concealed structures is routinely performed by mineral explorationists. SC is defined as the intersection density or the orientation diversity of linear structures, which can be derived from those magnetic data and/or acquired by geological structural mapping. Common features from both the SC and the magnetic data can be grouped together into one class by the SOM, essentially an unsupervised neural network classification method. A small percentage of the data can also be designated as anomalous classes by the SOM. The SOM results can support gold exploration targeting in areas lacking any known gold deposits or occurrences. However, the predictive targeting of orogenic gold mineralization can also be achieved with the support of a SDNN using the SC results. The SDNN can be trained by the SC data over known gold deposits or occurrences. The top few percentiles of the target probabilities are used for target generation. As the orogenic gold targeting process involves SC, SOM, and SDNN, it may be called the S3 method. This proposed S3 method is tested using public domain high-resolution aeromagnetic data covering the world-class Timmins gold camp in the Abitibi greenstone belt, Superior Province, Ontario, Canada. The results document that the S3 algorithm is an effective and robust AI-supported method to target concealed orogenic gold mineralization.

Mantle plume trail beneath the ca. 1.1 Ga North American Midcontinent Rift revealed by magnetotelluric data.

Whilst the 1.1 Ga North American Midcontinent Rift (MCR) system is formed in association with the Keweenaw mantle plume, the absence of a northern third rift arm or aulacogen (a general characteristic of mantle plumes) has previously not been well understood. To help clarify this unusual plume-rift relationship and to better establish the region affected by the Keweenaw mantle plume, we present the first electrical resistivity model of the MCR derived from 3D inversion of EarthScope USArray and Lithoprobe magnetotelluric (MT) data, extending northwards into the Archean Superior Province. Our model shows a prominent highly conductive anomaly trending NW-SE at the base of Western Superior's cratonic lithospheric mantle, cross-cutting and extending for over 300km on both sides of the western rift branch. We propose that this anomaly reflects the ancient signature of a plume trail, resulting from metasomatism and/or partial melting of the sulfide-rich basal lithospheric mantle during impingement of the Keweenaw mantle plume.

Improving signal-to-noise ratios of ambient noise cross-correlation functions using local attributes

SUMMARY For seismographic stations with short acquisition duration, the signal-to-noise ratios (SNRs) of ambient noise cross-correlation functions (CCFs) are typically low, preventing us from accurately measuring surface wave dispersion curves or waveform characteristics. In addition, with noisy CCFs, it is difficult to extract relatively weak signals such as body waves. In this study, we propose to use local attributes to improve the SNRs of ambient noise CCFs, which allows us to enhance the quality of CCFs for stations with limited acquisition duration. Two local attributes: local cross-correlation and local similarity, are used in this study. The local cross-correlation allows us to extend the dimensionality of daily CCFs with computational costs similar to global cross-correlation. Taking advantage of this extended dimensionality, the local similarity is then used to measure non-stationary similarity between the extended daily CCFs with a reference trace, which enables us to design better stacking weights to enhance coherent features and attenuate incoherent background noises. Ambient noise recorded by several broad-band stations from the USArray in North Texas and Oklahoma, the Superior Province Rifting EarthScope Experiment in Minnesota and Wisconsin and a high-frequency nodal array deployed in the northern Los Angeles basin are used to demonstrate the performance of the proposed approach for improving the SNR of CCFs.

Correction to: Petrogenesis and Geodynamic Evolution of the Archean Shawmere Anorthosite Complex and Associated Gneisses, Kapuskasing Uplift, Superior Province, Canada

Correction to: Petrogenesis and Geodynamic Evolution of the Archean Shawmere Anorthosite Complex and Associated Gneisses, Kapuskasing Uplift, Superior Province, Canada

Crustal and uppermost mantle structures of the North American Midcontinent Rift revealed by joint full-waveform inversion of ambient-noise data and teleseismic P waves

Crustal and uppermost mantle structures of the North American Midcontinent Rift revealed by joint full-waveform inversion of ambient-noise data and teleseismic P waves

Testing the TTG–Metabasite Connection in the Southern Superior Province: an Integrated Geochemical, Isotopic, and Petrogenetic Modelling Approach

Abstract Archean cratons are dominated by tonalite–trondhjemite–granodiorite (TTG) suites, the products of crustal differentiation that formed early continental crust. These rocks may have been primarily generated by partial melting of hydrated basaltic crust in a variety of settings including subduction zones or the deep lithosphere. Sources are mainly inferred from examination of TTGs alone, as potential source rocks are rarely exposed. In the southern Superior Province, Canada, the Kapuskasing Uplift exposes an important crustal cross-section with upper- to middle-crustal TTGs and lower-crustal metabasites, which show evidence of having produced trondhjemitic anatectic melt. Here, we test the hypothesis that these metabasites were the source of the Mesoarchean to Neoarchean TTGs in the Kapuskasing Uplift by combining phase equilibrium and melt trace element modelling with whole-rock and zircon Lu–Hf isotope analysis and geochronology (garnet Lu–Hf and zircon U–Pb) of metabasic samples. By comparison of the results with existing data from TTGs in the Kapuskasing Uplift, we determined that the metabasites are plausible source rocks for the TTGs. The Lu–Hf systematics of the metabasites and TTGs are the most robust evidence of a genetic connection. Modelling results support an increase in TTG source depth over time. New geochronological data constrain partial melting of metabasite and crystallization of anatectic melt between ca. 2685 Ma and ca. 2600 Ma, coeval with crystallization of only the youngest TTGs. Overall, these results indicate a complex history of intracrustal differentiation in the Kapuskasing Uplift, with partial melting of two isotopically distinct lower-crustal metabasic sources at different times and depths.

Petrogenesis and Geodynamic Evolution of the Archean Shawmere Anorthosite Complex and Associated Gneisses, Kapuskasing Uplift, Superior Province, Canada

Abstract In this study, we integrated extensive field, petrographic, whole-rock major and trace element, and Nd–Pb–Sr–O isotope, and zircon U–Pb ages, trace element and Lu–Hf isotope data from the Neoarchean Shawmere Anorthosite Complex and surrounding gneisses to unravel their petrogenetic origin and tectonic history. The ~2765 Ma Shawmere Anorthosite Complex is interpreted to have been emplaced into a sequence of interlayered greywacke and basalt deposited in an intra-continental arc rift system above a north-dipping subduction zone. The complex consists mainly of anorthosite, leucogabbro, gabbro, and hornblendite that were emplaced as several batches of magmas and crystal mushes originating from sub-arc mantle sources. In contrast to the previous studies, our field and petrographic data suggest an igneous origin for the most hornblende in the complex, implying hydrous parental magmas. A hydrous magma origin is also consistent with the high-anorthite content (mostly 70–90%) of the plagioclase in the complex. Percolation of hydrous basaltic melts through gabbroic cumulates in crustal magma chambers led to extensive (>50%) replacement of igneous clinopyroxene by igneous hornblende. Continued subduction resulted in the closure of the intra-arc rift system and the intrusion of the complex by tonalite, granodiorite and diorite between 2765 and 2680 Ma in an Andean-type margin. The complex and surrounding gneisses underwent hornblende granulite-facies metamorphism mainly between 2680 and 2620 Ma, overlapping with mid-crustal east-west extension between 2660 and 2640 Ma. The granulite-facies metamorphism is recorded by the replacement of hornblende, plagioclase and clinopyroxene by garnet and the development of a garnet-orthopyroxene-plagioclase metamorphic assemblage with a granoblastic texture. Tectonic rebounding of mid-crustal rocks to upper crustal levels after 2620 Ma led to the formation of an extensive network of extensional fractures and retrograde metamorphism. Migration of CO2-rich hydrous fluids along the extensional fractures and grain boundaries resulted in the precipitation of many metasomatic minerals mainly at the expense of hornblende and plagioclase, including epidote, clinozoisite, tremolite, actinolite, paragonite, margarite, titanite, quartz, calcite, sillimanite, dolomite, and chlorite. Prevalent replacement of hornblende by garnet during prograde metamorphism and metasomatic replacement of hornblende and plagioclase by retrograde mineral assemblages disturbed the Sm–Nd, U–Th–Pb, and Rb–Sr isotope systems.

Quartz arenites as signatures of cratonisation: examples from the Archaean Stratigraphic Record, southern Africa

Abstract Holocene quartz-rich sands such as in the Orinoco River of Venezuela and Columbia, develop under a unique set of conditions including tectonic stability, intense weathering and long-term storage of sediment prior to burial. This review paper proposes that a similar set of conditions existed on the Mesoarchaean Earth by 3.0 Ga. Compositionally and texturally mature quartz arenites are present in the Mesoarchaean Hospital Hill Subgroup and correlative lower Mozaan Group, in the cover rocks of the Beitbridge Complex in the Limpopo Belt and at Buhwa in southern Zimbabwe as well as the Neoarchaean Manjeri Formation of Zimbabwe. These quartz arenites are interpreted as first-cycle and developed following the formation of stable cratons under conditions of slow subsidence (<10 cm/1 000 years), intense weathering in a hostile chemical environment related to the ambient carbon dioxide-rich atmosphere, long-distance intrabasinal transport by tides and/or waves and microbial processes that influenced the local chemical environment. Similar examples of Mesoarchaean quartz arenites are documented from the Yilgarn Block in Western Australia, the Slave and Superior provinces in Canada and the Dharwar and Singhbhum cratons in India. On a global scale, cratonisation was diachronous with the Kaapvaal Craton stabilised on a regional scale by 3.0 Ga whereas microcontinents existed over the remainder of Earth.