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The Laird Lake property, southwest Red Lake greenstone belt, straddles the contact between the Balmer (2.99–2.96 Ga) and the Confederation (2.74–2.73 Ga) assemblages. The property is 10 km along strike from the Madsen and Starrat–Olsen Au mines that are hosted near the contact. The Balmer assemblage consists of fine-grained, aphyric, locally pillowed mafic volcanic rocks, ultramafic intrusive and volcanic rocks with flow breccia textures hosting local spinifex-bearing clasts, and banded-iron formations. In contrast, the Confederation assemblage comprises porphyritic mafic volcanic rocks intercalated with intermediate to felsic volcanic rocks that include crystal lapilli tuffs, crystal tuffs, and tuffs. The Balmer assemblage is composed of tholeiitic mafic volcanic rocks with minor Al-undepleted komatiites, whereas the Confederation assemblage is calc–alkalic. Neodymium isotopes, in conjunction with trace element geochemistry, suggests that parts of the Balmer assemblage were weakly contaminated by an older intermediate basement. Both arc and back-arc volcanism occurs in the Confederation assemblage, with the arc rocks showing a stronger crustal component than the back-arc rocks. A maximum U–Pb age of 2741 ± 19 Ma for a crystal tuff and an age of 2737.68 ± 0.79 Ma for a diorite are consistent with a Confederation assemblage affinity for the intermediate calc–alkaline rocks south of the Au-bearing horizon. The Balmer assemblage represents an oceanic plateau formed by plume magmatism on the margins of the North Caribou Terrane, whereas the Confederation assemblage at Laird Lake formed in an oceanic arc setting where both arc and back-arc volcanism occurred simultaneously. [ABSTRACT FROM AUTHOR]

New mapping of the Barberton Greenstone Belt in South Africa shows that the central part is a pseudo-stratigraphy made of shallow-water and deep-water siliciclastic and volcanic slide blocks, with individual blocks ranging in size from tens of meters to >10 km in length. The outcrop pattern and scale are remarkably similar to those of large-scale Miocene to recent submarine landslides in New Zealand along the active Hikurangi subduction zone that are periodically triggered by earthquakes on the subduction megathrust, providing evidence for megathrust earthquakes in the Paleoarchean. [ABSTRACT FROM AUTHOR]

The late Archean Western Dharwar Craton supergroup has volcanic and sedimentary rocks deposited during 2900–2600 Ma underlain by the Sargur Group basement of 3.36–3.2 Ga granitic gneiss and older supracrustal rocks. The western part of the craton, known as the western province (Dharwar Foreland), comprises four major schist belts (Western Ghats-Bababudhan-Shimoga-Chitradurga). A regional gravity and magnetic (Total Field) survey was done in the Shimoga region. The geophysical data of the study area reveal the subsurface extension and behaviour of the exposed rocks of the area. The Euler deconvolution was used to define the depth of the anomaly sources. Euler depth solution for the spherical body (structural index 2), window size = 10, and depth tolerance = 5% depicts the depth of the various sources. The Euler depth solutions cluster over the hook-shaped schist rock of the Medur group (at the northern part of the area) reveals that the body's depth varies from 1 to 4 km in the central part, and at the northern flank, it goes up to 7 km. The solution also brought out the depth of the anomalous body near Hithala, within 4 km. The 2D forward depth modelling of the anomalous zone brings out the involvement of the tectonic forces in the generation of this anomalous body. The more precise depth from the model has been estimated between 2 and 3 km. The model clearly shows the relationship between schist rocks and the basement. However, the high-gravity anomaly has been modelled as the manganese bearing horizon, which has come to optimum depth because of folding and faulting in the region, thus providing a favourable zone for manganese deposition. [ABSTRACT FROM AUTHOR]

Despite countless advances in recent years, exploration for volcanogenic massive sulfide (VMS) deposits remains challenging. This is particularly the case in the Yilgarn Craton of Western Australia, where outcrop is limited, weathering is deep and extensive, and metamorphism is variable. At Erayinia in the southern Kurnalpi terrane, intercepts of VMS-style mineralization occur along ~35 km strike length of stratigraphy, and a small Zn (-Cu) deposit has been defined at King (2.15 Mt at 3.47% Zn). An extensive aircore and reverse circulation drilling campaign on the regional stratigraphy identified additional VMS targets, including the King North prospect. Through a combination of detailed rock chip logging, petrography (inc. SEM imaging), and lithogeochemistry, we have reconstructed the volcanic stratigraphy and alteration halos associated with the King North prospect. Hydrothermal alteration assemblages and geochemical characteristics at King North (Mg-Si-K enrichment, Na depletion, and high Sb, Tl, Eu/Eu*, alteration index, CCPI, and normative corundum abundance values) are consistent with an overturned VMS system. The overturned footwall stratigraphy at King North is dominated by metamorphosed volcanic rocks, namely the following: garnet amphibolite (tholeiitic, basaltic), biotite amphibolite (andesitic, calc-alkaline), chlorite–quartz schist (dacitic), and narrow horizons of muscovite–quartz schist (dacitic to rhyolitic, HFSE-enriched). The hanging-wall to the Zn-bearing sequence is characterized by quartz–albite schists (metasedimentary rocks) and thick sequences of amphibolite (calc-alkaline, basaltic andesite). An iron-rich unit (>25% Fe2O3) of chlorite–actinolite–quartz schist, interpreted as a meta-exhalite, is associated with significant Cu-Au mineralization, adjacent to a likely syn-volcanic fault. Extensive Mg metasomatism of the immediate felsic footwall is represented by muscovite–chlorite schist. Diamond drilling into the deep hanging-wall stratigraphy at both King North and King has also revealed the potential for additional, stacked VMS prospective horizons in the greenstone belt stratigraphy. The discovery of HFSE-enriched rhyolites, zones of muscovite–chlorite schist, presence of abundant sulfide-rich argillaceous metasedimentary rocks, and a second upper meta-exhalite horizon further expand the exploration potential of the King–King North region. Our combined petrographic and lithogeochemical approach demonstrates that complex volcanic lithologies and VMS alteration signatures can be established across variably metamorphosed greenstone belts. This has wider implications for more cost-effective exploration across the Yilgarn Craton, utilizing RC drilling to reconstruct the local geology and identify proximal halos, and limiting more costly diamond drilling to key areas of complex geology and deeper EM targets. [ABSTRACT FROM AUTHOR]

There are numerous Neoarchean metasedimentary rock packages in the Slave craton, and they serve as important archives of tectonic processes. Little is documented on the Neoarchean sedimentary packages of the Winter Lake greenstone belt of the central Slave craton, however, and their interpretation can aid in the understanding of the final stages of Slave craton amalgamation. This project investigates the depositional environments and tectonic settings of the Itchen Formation and Sherpa Formation of the Winter Lake greenstone belt. Our study provides constraints for reconstructing the Neoarchean evolution of the central Slave craton through bedrock mapping and facies analysis. The Itchen Formation consists of submature mudstone, siltstone, and sandstone, with preserved graded bedding, planar bedding, and flame structures. Unconformably overlying the Itchen Formation is the Sherpa Formation, which is dominated by polymictic conglomerates and coarse-grained sandstones with preserved cross-bedding, imbricated clasts, and scour surfaces. The Itchen Formation is interpreted to have been deposited in a convergent basin (i.e., retro-arc foreland basin), where two facies associations outline turbidite and suspension sedimentation consistent with submarine fan deposition on a continental slope and a basin floor environment. By contrast, the Sherpa Formation has three facies associations representing dominantly alluvial–fluvial environments in terrestrial–marine–lacustrine settings deposited in pull-apart basins resulting from transtensional forces associated with the Beniah fault zone. [ABSTRACT FROM AUTHOR]

Zircon is not a common accessory mineral of banded iron formation (BIF), but it occurs in all BIF samples from the Kostomuksha Greenstone Belt (KGB) in the Karelian Craton of the Fennoscandian Shield. The Kostomuksha BIF is of Algoma type and is part of three variably old rock associations: BIF-1 is part of a sedimentary sequence in Mesoarchean (2.87–2.84 Ga) basaltic komatiites with dacites, BIF-2 is located in Meso-Neoarchean (2.8–2.79 Ga) felsic volcanics, and BIF-3 is part of a Neoarchean (2.76–2.74 Ga) greywacke unit with felsic volcanics. Analysis of zircon has revealed grains with cores and several generations of rims. The U-Th-Pb systems of zircon indicate that its isotopic age varies considerably from 2.98 to 1.89 Ga, forming up to 4 age clusters in each sample. Most samples contain single inherited grains. The bulk of zircon in BIF is younger than the host rocks and is interpreted as metamorphic. Most of metamorphic zircons display an oscillatory zoning, and their Th/U ratio varies from 0.01 to 4.7, i.e. their origin is hard to interpret reliably, based on the above characteristics. Paleoproterozoic (1.89–1.85 Ga) zircons from BIF-1 and 3, occurring as rims and individual grains, are related to local tectono-thermal processes simultaneous with the formation of the Svecofennian orogen and were described for the central Karelian Craton for the first time. Thus, both inherited and metamorphic zircons have been revealed in Meso-Neoarchean BIF metamorphosed repeatedly in the Neoarchean-Paleoproterozoic under up to amphibolite-facies conditions. All metamorphic generations of zircons from BIF are correlated with the tectono-thermal events in the Karelian Craton, including the effect of the Svecofennian orogeny. [ABSTRACT FROM AUTHOR]

Volcaniclastic deposits are cynosures for reconstructing volcanic archives and evaluating the tectonic imprints of the study area. This paper presents an elaborate geological field litholog, petrography and geochemistry of ~1.2 km thick sequence of the quartz-feldspar porphyry (QFP) and rhyolites in the Kadiri–Hindupur section of the Kadiri Greenstone belt from Eastern Dharwar Craton (EDC). The QFP exhibits primary stratification; the thickness of the beds varies from very thin to thick (3–8 cm) and shows large-scale tabular cross-bedding in the lower half of the section. The bedding surfaces of QFPs are marked by current crescent-shaped marks (long axis: 5–25 cm, short axis: 2–8 cm), speculated as possible remnants of volcanic bombs and pyroclastic debris during the explosive volcanism. Petrographically, these QFPs are characterised by spectacular blue opalescent quartz grains with embayed grain boundaries, anhedral feldspar with sieved texture, fractured plagioclase and polycrystalline groundmass suggesting a volcaniclastic origin. They are also endowed with significant post-depositional textures such as domino-listric faulting and sigma-shaped porphyroblasts. Geochemically, QFPs are unaltered with trachyte-trachy dacite compositions showing high-potash, calc-alkaline nature displaying shoschonitic affinity. The primitive mantle normalised trace and rare earth elements are marked by an enriched LREE-LILE pattern coupled by negative zircon–hafnium, niobium–tantalum and titanium anomalies affirming their common genetic link to a prominent island arc–back-arc system where explosive volcanism produced the felsic crystal tuffs that were deposited and preserved as volcaniclastic QFP. The associated blocks and bombs produced the current crescent-shaped marks preserved on the bedding surfaces of QFPs. Research highlights: Research Highlights Quartz-feldspar porphyry (~1.2 km thick) occurs in the Kadiri Greenstone Belt, Eastern Dharwar Craton. Blue opalescent quartz and deformed plagioclase porphyry indicate volcaniclastic origin. Enigmatic current crescent-shaped marks represent remnants of volcanic bombs and pyroclastic debris. The primitive mantle normalised REE diagram is characterised by LREE-LILE enrichment. They represent Neoarchean pyroclastic volcanism and sedimentation in an island arc–back-arc setup. [ABSTRACT FROM AUTHOR]

Three variably old groups of banded iron formation (BIF) are known in the Kostomuksha Greenstone Belt (KGB) of the Karelian Craton. This paper deals with the earliest of them, Mesoarchean (2.87–2.81 Ga) BIF-1. BIF-1 occurs among the komatiite–basalt unit of the KGB. BIF-1 consists mainly of quartz and magnetite, with varying amounts of amphibole, biotite, and garnet; the variations of SiO2 (48.3–58.6 wt %) and (21.34–33.82 wt %) suggest that the rocks are BIF. BIF-1 of the KGB, as well as most Archean BIFs, contain high concentration, display a contrasting positive Eu anomaly, lack of Ce anomaly, and the depletion of LREE relative to HREE. However, they differ from other BIFs in the higher Al2O3, TiO2, MgO, K2O, Cr, Ni, Zr, Ba, Cu and Zn concentrations. BIF-1 was formed in a marine basin at an anoxic atmosphere due to hydrothermal fluids, the proportion of which varies from 20 to 80%, and a terrigenous component derived mainly from basalts, komatiites, and dacites of host rocks. Mesoarchean BIF-1 of the KGB was accumulated in a small rift structures within an oceanic volcanic plateau, the formation of which is associated with the influence of a mantle plume on the oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23‰ are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17‰ and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4 + in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life. [ABSTRACT FROM AUTHOR]

The results of studies of carbonaceous matter (CM) and the S isotopic composition of associated sulfides in metapelites of the Neoarchean banded iron formation of the Kostomuksha greenstone belt of Karelia (Karelian Craton of the Fennoscandinavian Shield) are presented. The petrographic observations show that the CM occurs inside and between silicates, in sulfides, or at the grain boundaries between the sulfide crystals and biotite or amphibole. The results of scanning electron and atomic force microscopy showed the presence of several CM types distinct in structure and C content. The analysis of Raman spectra of CM revealed the presence both of well-ordered graphite and weakly structured kerogene in samples. The isotopic composition of the total organic carbon is typical of biogenic processes. The δ13Corg values from –27.9 to –30.6‰ are consistent with the fixation of carbon by photo- or chemoautotrophs. The S isotopic composition of associated sulfides is characterized by a positive Δ33S anomaly (up to +0.94‰) and negative δ34S values (from –2.06 to –4.1‰). The positive Δ33S values indicate a genetic link with photochemical elemental sulfur (S8) from the atmosphere, whereas the negative δ34S values reflect the fractionation of isotopes during bacterial-related processes. Based on these observations, we suggest that the primary CM mostly has a biogenic origin. [ABSTRACT FROM AUTHOR]

Reactivation of pre-existing fractures is attributed to fluid pressure conditions and orientation of fractures with respect to the tectonic stress field. In most cases, multiple fluid pressure events reactivate fracture networks. However, it is difficult to perceive and quantify the number of such fluid pressure events directly from a heterogeneous vein data distribution. In the present study, we undertake a statistical approach, well known and extensively used for fuzzy clustering of planar data to approximate the minimum number of fluid pressure events which formed/reactivated fractures. We have also combined the deterministic method for quantifying the minimum number of such fluid pressure events with the traditional method of scaling 3D Mohr circles to determine the absolute fluid pressure magnitudes. The method has been applied to published data of the Gadag-Chitradurga greenstone belt, a prominent Archean greenstone belt of the western Dharwar Craton, south India, to understand the mechanism behind shallow crustal emplacement of auriferous quartz veins within a transtensional tectonic regime. Further, we provide field evidence of fracture reactivation and estimate their reactivation potential, which play a significant role in the spatial variation of fluid pressure along the greenstone belt. Identifying data clusters using Bingham statistics for Pf determination. [ABSTRACT FROM AUTHOR]

Petrochronology of monazite in volcanic rocks of the Hutti deposit in the Eastern Dharwar Craton (India) has been studied to understand the magmatic and hydrothermal events that have affected the area. The volcanic rocks occurring in the Hutti greenstone belt are bimodal in nature and contain both felsic and metabasalt. The felsic volcanic rocks in the area preserve accessory minerals like monazite, allanite, and apatite, whereas the same is absent in metabasalts. Petrographic observation of felsic volcanic rock shows corona growth of allanite and apatite (in addition to huttonite) clustering around monazite grains. This corona texture, termed allanite cluster, occurs parallel to the shear planes (C‐plane) of the felsic volcanic rock and characterizes late‐stage hydrothermal activity in the area. Texturally, monazite in the felsic volcanic rock occurs included within arsenopyrite (<1 μm), and in association with apatite, allanite, and occasionally with huttonite/thorite (~10–40 μm), in which monazite grains preserve geochemical heterogeneity in both intra‐ and inter‐grains. The U–Th–PbTotal dating of monazite associated with the allanite cluster shows two age peaks (both from intra‐ and inter‐grains) at 2658 ± 17 Ma (older) and 2534 ± 38 Ma (younger), in which the older age represents the magmatic/crystallization age of the studied felsic volcanic rock overprinted by a later hydrothermal event in the study area. Based on monazite geochemistry‐geochronology, the present study deduces two texturally constrained events related to the primary crystallization of monazite (~2.65 Ga) and subsequent alteration of the same during a later hydrothermal event (ca. 2.53 Ga) that has affected the felsic volcanic rock in the Hutti gold deposit. [ABSTRACT FROM AUTHOR]

• Hadean mantle was involved into formation-reworking process of NCC from 3.8Ga until 2.45Ga. • Early basalts can derive from a common 4.4Ga mantle formed shortly after lunar impact. • Eoarchean 142Nd heterogeneity seems analytical, rather than truly heterogeneous. • Hadean depleted domains can remain convectively isolated for 1.7 billion years. The 146Sm-142Nd systematics of Archean rocks have been extensively studied to decipher chronological and compositional constraints on Hadean differentiation processes. However, the paucity of 142Nd data on Meso- and Neoarchean mantle-derived rocks relative to earlier periods contributes to uncertainty about the ultimate fate of primordial silicate reservoirs in the convective system of the early Earth. Here we present 146,147Sm-142,143Nd and 176Lu-176Hf zircon data for Mesoarchean (3.0–3.1 Ga) to Paleoproterozoic (2.45 Ga) granitoids, amphibolites and sedimentary rocks representing the main lithological units of the eastern North China Craton (NCC). The analyzed samples have well-resolved positive 142Nd anomalies, suggesting that the Hadean materials have been involved into the generation and evolution of the Eoarchean-Neoarchean continental crust of the eastern NCC. The model age of differentiation (4. 44 − 0.07 + 0.05 Ga) and the 147Sm/144Nd source ratio (0.211 ± 0.002) estimated from the 3.1 Ga Caozhuang amphibolites are identical to those of the 3.8–3.6 Ga rocks from the North Atlantic Craton and the 2.7 Ga pyroxenites from the Abitibi Greenstone Belt, suggesting that these mantle-derived rocks originated from a common, moderately depleted reservoir that differentiated in the wake of the Moon-forming impact and evolved in closed-system until at least 2.7 Ga. These observations contradict the commonly accepted notion of progressive homogenization of 142Nd anomalies in the Archean due to crustal recycling and convective mixing, and instead suggest that primordial differentiation produced a long-lived, depleted reservoir that remained largely isolated from convective mixing on a timescale of several billion years. [ABSTRACT FROM AUTHOR]

This study aims to delineate concealed subsurface linear structures and their relationship with mineralisation in the Iramba-Sekenke greenstone belt. Results reveal three different types of linear structures and their concealed continuations, which were previously not identified. These structures include dykes trending in NE-SW and NS; shear zones with NW-SE trending and faults that trend in NE-SW, NW-SE and N –S. The faults and shear zones, which were previously shown to terminate at the northwestern end of the Iramba Plateau due to sediment cover, have been revealed to continue into Wembere depression. Moreover, the aeromagnetic and gravity results show that some faults are intruded by dykes in the same trends, which were not previously identified. The geological relationship between these linear structures shows that the youngest structures are the western dolerite dyke trending N –S and the oldest is the NE-SW Wembere-Iramba Plateau fault. The delineation of geological structures from magnetic and gravity data using different analysis techniques reveals that the mining pits are located close to geological structures trending in NW-SE, NE-SW and N –S directions. The integration of the findings from CET grid analysis techniques, together with magnetic maps and geological information reveals a good correlation between known occurrences of minerals and promising exploration target areas. The good correlation between the artisanal mining pits with the location of the potential exploration targets is consistent with the location of lineaments and provides future promising prospects for mineral exploration. The correlation suggests that mineralisation and ore deposits in the study area are respectively structurally controlled and hosted in deformed rocks. This study is potentially useful as a guide for the delineation of concealed subsurface linear structures and integration of structural geometry and geophysical methods for exploration of hidden mineral deposits in the Iramba-Sekenke greenstone belt. • New geological linear structures have been extracted trending in NW–SE and NE–SW. • The faults and shear zones have been revealed to continue into Wembere depression. • Some faults, previously not identified, are intruded by dykes in the same trend. • Potential exploration targets correlate with the location of geological lineaments. • Mineralisation are structurally controlled and ore deposits hosted in deformed rocks. [ABSTRACT FROM AUTHOR]

• The study reveled the formation of the Neoarchean conglomeratic Ament Bay basin. • The basin is similar to the Timiskaming assemblage in sedimentation and setting. • The basin is dissimilar to the latter in crustal architecture and gold endowment. • The lack of gold in the basin is due to existence of underlying gneissic basement. • Timiskaming-like basins similar in geology may not contain similar gold endowment. The Neoarchean conglomeratic Timiskaming assemblage is considered to be one of the most gold-endowed rock associations in the Abitibi greenstone belt of the southern Superior craton. Identifying Timiskaming-like basins, therefore, may facilitate new discoveries of gold deposits in other Archean greenstone belts. This study focuses on the conglomeratic Ament Bay assemblage (ABA) in the Neoarchean Sturgeon Lake greenstone belt of the western Wabigoon terrane of the western Superior craton. Geologic mapping and petrographic analysis show that the ABA consists of a ≥1000 m thick conglomerate-arenite lithofacies and a conformably overlying ≥200 m thick greywacke-mudstone lithofacies, which are interpreted to indicate a sub-aerial fan delta that transitioned into subaqueous turbidites. The depositional age is constrained to be between 2697.5 ± 1.2 and 2693.2 ± 0.9 Ma by the statistically defined minimum age of the ABA detrital zircons and igneous zircons of an alkalic intrusion within the ABA, respectively. Detrital zircons from seven ABA samples are characterized by ca. 2930, 2780–2770, and 2750–2690 Ma age populations along with minor zircons of ca. 3300–3000 Ma, which are consistent with proximal sources mostly in the western Wabigoon terrane and secondarily in the adjacent Winnipeg River terrane. Petrography of conglomerate clasts and sandstone supports these provenances and reveals additional sources from proximal mafic volcanic rocks. The ABA is interpreted to result from uplift and erosion associated with the late-stage convergence between the western Wabigoon and Winnipeg River terranes and to be partially controlled by a regional fault zone and accompanied by broadly coeval alkalic magmatism. Overall, the ABA is similar to the typical Timiskaming assemblage in lithofacies, depositional environments, structural setting, and syn -depositional alkalic magmatism, but dissimilar to the latter in gold endowment. The apparent lack of gold in the ABA is likely due to assimilation of crustal components into the coeval alkalic melts and a shallow-penetrating fault zone, in contrast to the juvenile nature of alkalic magmatism and deep-penetrating fault zones associated with the Timiskaming assemblage. This study suggests that Timiskaming-like basins similar in geology are not necessarily equivalent to the typical Timiskaming assemblage in gold endowment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Most high-density Pilbara greenstones confined to upper crust. • Granitic complexes extend to depths of 10–20 km and some have higher density cores. • Lower crust reworked or deep greenstone subsidence not widespread. The Paleoarchean East Pilbara Terrane contains some of the oldest rocks on Earth, and has a distinctive surface architecture of granite domes surrounded by arcuate greenstone belts. Explanations for creation of the domes include fold interference, core complex formation and the subsidence of a dense, mafic crust between relatively buoyant granitic complexes. In the latter "sagduction" process, greenstones are often viewed as descending to the base of the crust. Here we present a 3-D inversion of Bouguer gravity data for density contrast constrained by shear wave velocities and a seismic reflection profile. We show that the East Pilbara Terrane is predominantly characterized by a two-layer crust with high-density greenstone rocks largely confined to the upper crust, which is inconsistent with vertical tectonic models requiring large-scale greenstone preservation in the lower crust. The eastern margin of the terrane is marked by a west-to-east transition from low-density ovoid bodies to linear northwest-trending sources associated with the Proterozoic Paterson Orogen. We identify the previously unknown 10–15 km wide Tumbinna Pool Dome, between the Mount Edgar and Yilgalong domes. Higher density sources related to the surface distribution of greenstone rocks largely occur above 10–15 km depth, though they may locally reach >15 km depth on the north side of the Mount Edgar Dome. Some granitic domes have higher density cores related to distinct granite suites, while the Split Rock Supersuite appears to exhibit systematically lower density at depths of 5–10 km. Low-density sources due to small intrusions such as the North Pole Dome only extend to depths up to 10 km, while the large Mount Edgar Dome can be identified at depths as great as 15–20 km. Some low-density bodies in the lower crust, one of which underlies the Yilgalong Dome, correlate with regions of reduced seismic reflectivity, which we interpret to be possible relict migmatisation zones or melt pathways. A weakly constrained ESE-trending high-density region immediately below the Moho correlates with isolated sub-Moho reflectors, and may be a relict zone of rifting and delamination. [ABSTRACT FROM AUTHOR]

It is unresolved when eolian processes began to significantly affect global mean sand composition and texture through abrasion and enhanced sorting. Reports of Proterozoic eolian textures and sedimentary structures are common, in particular from 1.8 Ga on, but the Archean (4.0–2.5 Ga) geologic record possesses only seven reported eolian occurrences which generally do not manifest more than a few diagnostic features of eolian transport. We investigate in detail sandstone units within the Moodies Group (ca. 3.22 Ga) of the Barberton Greenstone Belt, South Africa, one of the oldest well-preserved terrestrial–marine sandy successions. Eight examined locations show terrestrial facies associations, high degrees of compositional and textural maturity, and large-scale foresets; however, none show convincing evidence of eolian transport but several can be excluded with confidence. In comparison to recent eolian strata, grains are generally slightly too coarse-grained, too angular, and mostly too poorly sorted. The common presence of shale laminations, granules, rare pebbles, and shale rip-up clasts demonstrates that the investigated strata were either of aqueous origin or had been formed by eolian processes but were subsequently aqueously reworked. This is vexing because the sandy-gravelly fluvial, coastal floodplain, and estuarine depositional environments of Moodies Group strata may have been hospitable to potentially powerful and long-lasting Archean eolian processes. Early Archean eolian strata may have had a limited depositional area, may have been extensively reworked, or formed under non-actualistic conditions. Thus, the significance of eolian processes on early Earth and their potential contribution to the high degree of textural and compositional maturity of Archean quartzarenites remains poorly constrained. [ABSTRACT FROM AUTHOR]

• Geochemical subdivision of mafic-intermediate volcanic rocks based on immobile element ratios. • Blake River Group geochemical diversity is mostly caused by crustal interaction with TTG-like contaminant. • VMS deposits in the Blake River Group show a potential relationship with crustal assimilation. • Composition of mafic to intermediate volcanic rocks has potential for VMS vectoring. Volcanogenic massive sulfide (VMS) deposits, prevalent since the Archean, constitute a well-explored ore deposit type. Nonetheless, the factors contributing to variations in fertility among volcanic centers, assemblages within greenstone belts, or entire greenstone belts remain unclear. For instance, the Blake River Group (BRG) of Ontario and Quebec, Canada, hosts almost half of the total VMS tonnage of the entire Abitibi greenstone belt, yet represents less than 10 % of its map surface. This study utilizes a large dataset (n = 2271) of whole-rock geochemistry for mafic to intermediate volcanic rocks to understand the BRG petrogenesis, and its implications for VMS endowment in the Abitibi. Principal Component Analysis shows that Ti, Th, and Yb are the primary contributors to the dataset's variation. This yields a two-ratio diagram (Th/Yb versus Zr/Ti) revealing seven geochemical groups with coherent map patterns referenced as tholeiitic basalts, tholeiitic intermediate rocks, medium-Th basalts, transitional intermediate rocks, high-Th basalts, calc-alkaline intermediate rocks and low-Zr basalts. A least altered subset of the data is used to analyze major element patterns. BRG mafic to intermediate magmas show variable degrees of Fe-Ti enrichment/depletion during their evolution, with simultaneous Al 2 O 3 depletion or lack thereof. Utilizing a single parental mafic tholeiitic magma, the Magma Chamber Simulator enables the modeling of major and trace element compositions for each geochemical group. Fractional crystallization (FC) models with variable initial water contents can explain the range of the tholeiitic basalt and tholeiitic intermediate compositions. Assimilation fractional crystallization (AFC) models successfully replicate most of the geochemical groups using a TTG average composition for the assimilant. While mafic-intermediate host rock geochemical signatures are not the sole factor influencing VMS endowment in volcanic belts, regional analysis reveals that the vast majority of volcanic rocks in geological formations bearing VMS deposits in the BRG are crustally contaminated lacking tholeiitic geochemical groups. Conversely, poorly endowed formation consistently contain samples from these groups. Moreover, the Bousquet formation, which hosts several world-class gold-rich VMS deposits, displays the highest rates of crustal assimilation, further suggesting that petrogenesis of mafic-intermediate volcanic rocks is linked to VMS metallogenesis in the BRG. [ABSTRACT FROM AUTHOR]

Cadmium stable isotope ratios can serve as valuable tracers for biological and geological processes, including nutrients sampling from the surrounding medium, volatilization events, and terrestrial differentiation. However, studies of the isotope fractionation occurring during geological processes require the characterization of the isotope compositions of the different terrestrial reservoirs. Notably, the cadmium isotopic composition of the Bulk Silicate Earth (BSE) is still a matter of debate. To address this issue, we present high-precision cadmium isotope data from a diverse set of samples, including mid-oceanic ridge basalts (MORB) and komatiites obtained using a 106Cd 111Cd double spike system. We processed nine biological and geological reference materials (AGV-2, BCR-2, BHVO-2, BIR-1, COQ 1, GSP-2, NIST 2711, NOD-A-1, ERM BB 186) and two pure Cd solutions (AAS and ChemLab) to assess the accuracy and precision of the method. Our study revealed that twenty-three MORB samples (including ten analyses from the literature) from the Atlantic, Indian, and Pacific oceans have a homogeneous cadmium isotopic composition. The weighted mean isotope composition for these samples, expressed as δ114Cd (the permil deviation of the 114Cd/110Cd ratio from the NIST SRM 3108 Cd standard), is 0.07 ± 0.10 ‰ (2SD, n = 23). We also studied twelve komatiite samples from the Abitibi (Superior Craton, Canada), Barberton (Kaapvaal Craton, South Africa), and Kostomuksha (Baltic Shield, Fennoscandia) greenstone belts to characterize the deep Archean mantle isotope composition. These samples, combined with four analyses from the literature (Pickard et al., 2022) exhibited isotopic compositions ranging from −0.33 ± 0.04 ‰ to 0.26 ± 0.08 ‰. We observed a negative correlation between cadmium abundances and the degree of secondary alteration (measured by loss on ignition-LOI). For samples with low LOI (≤ 6 wt%), the isotope compositions of komatiites are quite consistent. On the other hand, the samples with higher LOI (between 6 and 8.4 wt%) tend to be more scattered and can have lighter isotope compositions. These correlations suggest that, although Cd isotope compositions in komatiites are quite resilient to alteration, heavier Cd isotopes can be mobilized into secondary alteration fluids, driving altered samples toward isotopically lighter compositions. This implies that secondary alteration exerts an important control on the isotope compositions of komatiites. Therefore, only the Cd isotope compositions of the least altered komatiites (i.e., those with LOI ≤ 6 wt%) have been used as proxies for their mantle source isotope composition. These samples (two from the Abitibi greenstone belt, one from the Barberton greenstone belt, one from the Baltic shield and one from the Belingwe greenstone belt) gave a weighted mean isotope composition of 0.14 ± 0.18 ‰ (2SD, n = 5). No significant isotope variation was found between the pristine samples from each region, despite ages ranging from 3549 ± 99 Ma to 2713 ± 29 Ma, indicating a possible isotopic homogeneity (within the currently achievable precision) of the Archean mantle for Cd starting as early as 3.55 billion years ago. We determined a Cd isotope composition for the mantle by combining the data for mean MORB and komatiites. This gave a δ114Cd value of 0.11 ± 0.10 ‰ (2SD, n = 28) for the Bulk Silicate Earth. This value is significantly heavier than previously proposed. • A novel Cd isotopic measurement using a 106Cd 111Cd double spike has been developed. • Mid-oceanic ridge basalts exhibit homogeneous cadmium isotope compositions. • Pristine komatiites have consistent Cd isotope compositions regardless of their age. • Earths' mantle has a δ 114Cd = 0.11 ± 0.10‰ (2SD, n = 28), heavier than previous estimations. [ABSTRACT FROM AUTHOR]

Bedrock geological mapping indicates that diverse granitoid intrusions occur closely in space and time in the Paleoproterozoic Lynn Lake greenstone belt of the Trans-Hudson Orogen, Manitoba, Canada. These intrusions display distinct geochemical characteristics of I-type, A-type and adakite-like granitoids as revealed by their respective alkalinity, alumina saturation state, and trace element concentrations and ratios. The ca. 1879 Ma I-type granitoid pluton intruded the 1892 to 1884 Ma supracrustal package of volcanic, volcaniclastic and minor sedimentary rocks that constitute the greenstone belt, which was cut by 1873 Ma A-type granite and then by 1854 Ma adakite-like quartz diorite intrusions. Why the geochemical affinities of these granitoids change so rapidly (within ∼25 Myr) in orogenic belts, however, is not as well understood. Here we propose using Sm Nd isotope data and trace element modeling that the compositional variety of the granitoid intrusions likely reflects the mineral assemblages of their source rocks rather than magmatic fractionation. They may have been formed by partial melting of the disparate sources at different depths to respond to the change in tectonic regimes. The timing of the granitoid intrusions tracks a rapid geodynamic transition from subduction to intra-arc extension and to slab break-off due to terrane accretion and collision. This records a crucial piece of history in geodynamic evolution of the Trans-Hudson Orogen, which to date has been overlooked largely in many other orogens. • I-type, A-type and adakite-like granitoids occur in the Lynn Lake greenstone belt. • The granitoids record a rapid transition in tectonic setting from arc, intra-arc extensional and slab break-off. • Their compositions are correlative to their source regions and geodynamic regimes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Seabee Gold Operation that hosts Santoy and Fisher yield a similar ore genesis. • Fisher and Santoy deposits host multi-stage system of orogenic gold mineralization. • Early gold mineralization overprinted by main-stage orogenic mineralization. • Mineral chemistry of alteration mineral assemblages similar for Fisher and Santoy. The Seabee Gold Operation, located in northern Saskatchewan, Canada, hosts the Santoy and Seabee gold deposits, as well as the Fisher property; the latter is an important exploration target. This gold mineralization is hosted in rocks of the Pine Lake greenstone belt that is within the Glennie domain of the larger Paleoproterozoic Trans-Hudson orogen. Mineralization is focused within shear zones, including the Santoy shear system that extends south onto the Fisher property. The role of ore-adjacent intrusions, systematics of gold mineralization, and relationship between the mineralization of the properties are largely undefined. In this study, hydrothermally-altered samples from locations along the Santoy shear system, namely the Santoy 7, Santoy Gap, and the Fisher property, were analyzed to identify and compare the mineralogical and geochemical characteristics related to sulfide-gold mineralization and associated alteration. The altered host rocks primarily comprise upper greenschist to lower amphibolite-grade sheared metabasalt to chlorite-hornblende-biotite ± garnet schist, and intrusive rocks dominated by granodiorite and tonalite. These lithologies are cut by similar quartz vein generations and are associated with similar alteration assemblages and mineralization, including (i) syn -late-D 3 "distal" (∼0.4 to 3 m wide) sericite-biotite-chlorite-clinozoisite ± albite, titanite to vein-adjacent coarse-grained diopside-K-feldspar-albite-actinolite ± apatite, titanite calc-silicate alteration, associated with main-stage Py 2a, 2b -Cpy 2 -Po 1 -Au (syn -late-D 3) mineralization; (ii) remobilized, fracture-filling Py 3 -Po 2- Cpy 3 -Au-BiTel (late-D 3) mineralization within the calc-silicate assemblage; and (iii) early colloform Py 1a (pre- syn -D 3) and intrusion-hosted, inclusion-rich Py 1b (pre-D 3). Microprobe analyses reveal similar mineralogical trends between Fisher and Santoy alteration minerals typical of orogenic gold systems. Empirical geothermobarometric calculations of gold-associated vein-adjacent and vein-hosted chlorite and biotite exhibit orogenic-style formation conditions (∼320–330 °C, 3 kbar, ∼9 km depth). As such, these analyses suggest that the Fisher property and Santoy Mine Complex underwent inter-connected, multi-stage hydrothermal processes. These stages comprise (i) a potential early introduction of gold into the system closer to the timing of plutonism (Py 1b magmatic-hydrothermal; pre-D 1) or during the onset of gold mineralization (Py 1a ; orogenic; late-D 2 to early- syn -D 3) during the evolution of the Reindeer zone; (ii) orogenic main-stage mineralization (syn -late-D 3) concurrent with late- to post- collisional deformation throughout the Reindeer zone; and (iii) remobilization during continuous deformation (late-D 3) where elevated cyclical fluid fluxes and higher fracture density at Santoy produced higher-grade mineralization. [ABSTRACT FROM AUTHOR]

Whole-rock geochemistry yields better geological maps of the bedrock, since it allows, for example, visually similar lithologies to be distinguished. However, conventional laboratory geochemistry is not available in the field during a mapping campaign. Portable X-ray fluorescence (pXRF) analyzers can produce fit-for-purpose data rapidly, and constitute a useful complement to conventional geochemistry in a bedrock mapping project. The pXRF data can be employed (i) while still in the field, to orient the mapping campaign; (ii) to prepare a preliminary geological map back in the office; and (iii) to interpolate between conventional whole-rock analyses on the final map. The latter application requires a matrix-matched secondary calibration of the pXRF data to improve its accuracy. Attention must also be given to precision issues, as well as potential instrument drift and analytical interferences. This paper summarizes recent efforts to systematically integrate quantitative pXRF data in government mapping projects within the Province of Quebec (Canada). We first demonstrate how an Olympus Vanta series M pXRF analyzer was commissioned and calibrated. We then show how the pXRF data was systematically acquired and utilized during a 1:50,000 to 1:20,000 mapping campaign in a Precambrian greenstone belt setting (Abitibi Subprovince). Before the mapping began in 2021, volcanic rocks in the study area were supposed to consist of only two mafic tholeiitic formations, called Obatogamau and Bruneau. Integrating pXRF into this project meant that while still in the field and immediately afterwards during preparation of the preliminary map: (1) a marker horizon representing the top of the Obatogamau Formation was chemically identified and then traced laterally; (2) the felsic Waconichi Formation was recognized despite the high metamorphic grade and also traced laterally just above the marker horizon; (3) the Bruneau Formation was shown to be much more continuous than previously known and to have Mg-tholeiites at its base, like in the type locality; (4) the Blondeau Formation was shown to occur above the Bruneau Formation. Within the volumetrically dominant Obatogamau Formation, Fe-tholeiites were also distinguished from visually similar Mg-tholeiites, which allowed these subunits to be traced while still in the field, leading to a more detailed map. Later, after the conventional laboratory chemistry had been received, the final geological map was prepared, but it was very similar to the preliminary map, confirming the satisfactory performance of the pXRF method for this application. However, we do note some issues and limitations even with the latest generation of analyzers. • Portable X-ray fluorescence (pXRF) analyzers are very useful for bedrock mapping projects. • The pXRF data allows visually similar lithologies to be distinguished while in the field. • However a commissioning stage is required, and validation with conventional geochemistry. [ABSTRACT FROM AUTHOR]

We use offshore 2-3D seismic reflection and potential field data coupled with field work to investigate the control of lithospheric heterogeneity and shear zone rejuvenation on the mode of extension and the architectural segmentation of the southern Angola margins. The pre-rift basement is inherited from several Precambrian deformation events ended by the Pan-African/Brasiliano orogen that accreted four different age-dependent lithospheric domains with contrasted thickness, fabrics, thermal structure, and chemical composition. From north to south, the continental crust is composed of Neoproterozoic metapelites, Paleoproterozoic gneisses and migmatites and Archean greenstone belts pervasively intruded by TTG granitoids. The latter are compartmentalized by lithospheric-scale Archean – Paleoproterozoic shear zones with a general sub-vertical fabric. Upon extension, these pre-existing shear zones nucleated extensional deformation, focalized magmatism and accommodated different rates of extension and width of offshore rift domains. In the north, younger Neoproterozoic lithospheric domain deformed with a ductile behavior and multiple crustal detachments promoting lithospheric decoupling and a distributed extension, with late continental break-up. It favored the formation of a wide magma-poor margin where extension was accommodated by low-angle, seaward-dipping extensional faults and mantle-exhumation. To the south, Archean and Paleoproterozoic lithospheric domain with stronger and brittle strength profile promoted a more localized extensional deformation and favored an early lithospheric coupling and continental break-up. This ultimately led to the formation of a short margin with increased magmatic budget, where extension was accommodated by high-angle, landward-dipping extensional faults and mantle-exhumation. We demonstrate that the pre-rift heterogeneity of the lithosphere controlled the mode of extension during the rift and the along-strike variation of margin geometry. Moreover, the rejuvenation of Precambrian shear zones as extensional transverse fault zones also promoted the activation of lithospheric-scale thermal drains facilitating the emplacement of mantle-related melts into the upper crust. • The Precambrian lithosphere of South Angola is heterogeneous in terms of structural fabrics and rheology. • Limits between basement domains consist of large sub-vertical structures referred to lithospheric-scale shear zones. • Onshore inherited shear zones extend in the rifted margin domain and are rejuvenated, both by tectonics and magmatism. • Patterns of shear zone rejuvenation are change in fault trends, margin orientation, polarity, width and magmatic budget. • Brazil – Angola pre-rift basement reconstruction responsible for rift segmentation and magmatic budged upon extension. [ABSTRACT FROM AUTHOR]

• Metabolic diversity in the lower platform facies of the Buck Reef Chert. • Exceptional preservation of Paleoarchean carbonaceous matter also on molecular level. • Different carbonaceous matter appearance (e.g., clots, laminae, blocky aggregates). • Rapid silicification supported carbonaceous matter preservation. Microbial life on Earth was well established in the Paleoarchean, but insight into early ecosystem diversity and thus, the complexity of the early biological carbon cycle is limited. Here we investigated four carbonaceous chert samples from the lower platform facies of the ca. 3.42-billion-year-old Buck Reef Chert, Barberton greenstone belt. The analysis on multiple scales revealed exceptionally well-preserved carbonaceous matter, even on molecular level (aliphatic and aromatic hydrocarbons), resulting from rapid silicification. Geochemical evidence from stable carbon and multiple sulfur isotopes supports the presence of different microbial metabolisms in the Paleoarchean ecosystem. The local biological carbon cycle was dominated by photoautotrophs, but autotrophic sulfate reducers and methane- or acetate-producing microbes were also present. In areas of microbial methane or acetate release, methanotrophs or acetotrophs contributed to the overall biomass. These results highlight the metabolic diversity in the lower platform environment of the Buck Reef Chert, and underline that an advanced biological carbon cycle already existed in the early Archean. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fractal and multifractal analyses were used to study four orogenic gold provinces. • Case study conducted on a key deposit at the local and micro scales. • Fractal dimension maps showed good correlation with known mineral occurrences. • Orogenic gold deposits showed multifractal behavior. • Multifractal indices help obtain information on gold deposits in multiple scales. Understanding the controls on the spatial distribution of mineral deposits is crucial for prospecting new occurrences. Various geological processes operate together at microscopic to macroscopic scales, generating mineral systems responsible for significant accumulations of economic minerals. This characteristic of functioning at various scales, accompanied by repetition of features over space during mineralization, indicates that these processes are self-similar, meaning they exhibit fractal geometry. Previous research has demonstrated that the combined action of processes involved in mineralization in such critical, nonlinear systems, produces objects with multifractal characteristics. Therefore, the spatial distribution of mineral deposits should be studied using appropriate methods for better understanding of their controls. In this context, this study investigated the multiscale geometric characteristics of worldclass orogenic gold systems in Archean greenstone belts using fractal and multifractal analyses. First, at the macroscopic-scale, regional-scale features were considered in the major greenstone belt provinces with orogenic gold deposits worldwide, namely: Abitibi (Canada), Norseman–Wiluna (Australia), Rio das Velhas (Brazil), and Central Lapland (Finland). Next, at an intermediate scale, local-scale features were examined in detail within the context of the Córrego do Sítio Lineament. Finally, at the microscopic scale, the focus was on the Córrego do Sítio orogenic gold deposit—a key deposit in the Rio das Velhas greenstone belt. Fractal dimensions of the spatial distributions of mineral deposits, magnetic lineaments, and their intersections were investigated at the macroscopic to local scales, as well as the spatial distribution of ore minerals at the microscopic scale, using the box-counting method. Maps of fractal dimensions of magnetic lineaments were generated and compared with the spatial distribution and tonnage of orogenic gold deposits at the regional scale. The same features were analyzed using the method of multifractal moments. The results at the three scales were analyzed and synthesized to identify meaningful patterns for understanding these orogenic gold systems. With regard to fractality, the orogenic gold deposits in all the investigated provinces exhibited unique spatial distributions at different scales, namely: less than 2–4 km, from 2 to 4 km to 10–30 km, and more than 10–30 km. The analysis of magnetic lineaments yielded a correlation between gradients of fractal dimensions and gold tonnages in the orogenic gold deposits. The multifractal analyses indicate multifractal geometries extending from the microscopic to the macroscopic scale. The calculated multifractal indices of Δα (singularity variation), τ"(1) (multifractality index), and Δf(α) (multifractal spectrum variation) showed direct relationships with endowment of orogenic gold in the studied provinces, as well as with differences in mineralization styles in thin sections. The findings demonstrate the effectiveness of the analyses used for improved characterization of the studied mineral systems; they also allow comparing similar systems at different scales and locations and they can be used to study other mineral systems with similar geological controls. [ABSTRACT FROM AUTHOR]

The Itareru tonalite is one of the Paleoproterozoic plutonic rock units that intruded the Serrinha block, an Archean-Paleoproterozoic crustal fragment of the São Francisco Craton (Bahia, Brazil). It is characterized by a ca. 80 km long, NW-SE elongated leaf-shaped body, mainly comprised of tonalite-diorite to granodiorite rocks with numerous dioritic enclaves. Magnetic studies were performed on 26 sites of the Itareru pluton (including country rocks). Anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM) are coaxial, indicating that all minerals have the same orientation, partially controlled by regional strain. Rock-magnetism measurements reveal that paramagnetic–matrix minerals contributed significantly to the magnetic susceptibility and AMS while magnetite grains in the range of 2–5 μm are responsible for AARM. Magnetic fabrics in the central region of the pluton are probably primary (magmatic), which was acquired when the rocks were crystallized, reflecting magma flow linked to a magma feeder zone (magma chamber). The moderated magnetic lineation plunges in the northern part of the pluton suggest that this region was close to the feeder zone. In contrast, the southern region should be far from it, since the magnetic lineations are horizontal to sub-horizontal. The Itareru tonalite emplacement was also controlled by regional strains related to the collision of the Paleoproterozoic Rio Itapicuru greenstone Belt with the Archean basement. • AMS and AARM are coaxial indicating that all minerals have the same orientation. • Magnetic fabrics in the central region of the pluton are probably magmatic acquired when the rocks were crystallized. • Magnetic fabrics in the central region of the pluton are related to magma flow. • The emplacement of the pluton was controlled by regional strains. • Itareru emplacement is related to the collision of the RIGB with the Archean basement. [ABSTRACT FROM AUTHOR]

• Zircon petrochronological (U/Pb-O-Hf) constraints for the far-east Yilgarn Craton. • Relatively old (2840 – 2775 Ma) crustal block at the eastern edge of the craton. • Identification of the newly defined Dorothy Hills Block and Yamarna Rift. • Re-assessment of the nomenclature in the Eastern Goldfields Terrane (EGT). • The EGT formed via sustained, autochthonous crustal growth. The Archean Yilgarn Craton in Western Australia represents one of the key areas for investigating the mechanisms of crustal growth during Earth's infancy. The far-eastern margin of the Yilgarn Craton has, however, received limited scientific scrutiny. In this study, in-situ zircon petrochronology (U-Pb, O, and Lu-Hf isotopes) is used to constrain the formation and evolution of the easternmost Yamarna and Burtville regions as well as the encompassing Eastern Goldfields (Super)Terrane (EGT) of the Yilgarn Craton. The new data highlight the unequivocal existence of relatively old (ca. 2840 – 2775 Ma), compared to the EGT, and isotopically juvenile (εHf: +2.1 to +3.5) and mantle-like (δ18O: 5.2 to 5.9‰) crust at the eastern edge of the exposed craton. We refer to this crust as the 'Dorothy Hills Block'. The Dorothy Hills Block shows geochronological and isotopic similarities with the adjacent 'Burtville Block' and the Youanmi Terrane (>400 km further west), which suggests a shared history up to ca. 2720 Ma. In addition, linear greenstone belts characterised by younger magmatism (ca. 2720 – 2660 Ma) with a constant, mildly supra-chondritic Hf isotope composition (εHf: 0.0 to +3.5) are identified between the Burtville and Dorothy Hills Blocks. We refer to this region as the 'Yamarna Rift', by analogy to the better-understood 'Kalgoorlie-Kurnalpi Rift'. It is inferred that the Burtville and Dorothy Hills Blocks formed via peri-cratonic magmatism (ca. <2970 Ma), associated with mantle upwelling focused along the eastern edge of the ca. >3300 Ma Yilgarn proto-craton. The Yamarna and Kalgoorlie-Kurnalpi Rifts (ca. 2720 – 2660 Ma) overlie this extended older substrate and formed via intra-cratonic rifting broadly coeval with a major mantle upwelling event. The revised Meso- to Neoarchean crustal evolution model for the EGT, including new nomenclature, suggests a sustained (>200 Myr) and autochthonous geological development of the eastern Yilgarn Craton resulting from mantle upwelling events, potentially within a back-arc tectonic setting. Comparable crustal evolutionary trends are recorded in other Archean cratons (e.g., Superior Craton), which suggests that similar geodynamic regimes operated on a global scale in the Archean. [ABSTRACT FROM AUTHOR]

The potential field (gravity & magnetic) data, along with results of available seismic and magnetotelluric studies over the Southern India Shield comprising the Dharwar craton (DC), Southern Granulite Terrane (SGT) and southern part of the Eastern Granulite Mobile Belt (EGMB), were synthesized. The study attempts to elucidate the geometry and continuity of greenstone belts/shear zones, isostatic condition and deeper crustal architecture. We observed a characteristic elevation-gravity relationship for each of the tectonic domains. The greenstone belts of the DC are characterized by N-S to NW-SE trending positive residual gravity anomalies and continue beneath the Cuddapah sediments. The basement of the Cuddapah basin is characterized by NW-SE trending greenstone belts with low-density intrusive rocks. The gravity anomaly suggests occurrence of a high-density rock unit occurs at mid-crustal depth beneath the 'Closepet granite' and 'Chitradurga schist belt'. The potential field signatures of the DC and SGT are distinctly different. The Cauvery Shear Zone is characterized by positive residual gravity and magnetic anomalies with ∼E-W to ENE-WSW trend that continues further east under sediment covers of the east coast. The residual gravity signatures and horizontal gravity gradient signatures suggest that the orogenic systems encompassing the Cauvery Shear Zone and the eastern part of the EGMB may be a part of a common structural belt or tectonic regime associated with the assembly of the Gondwana supercontinent. The potential field modelling reveals the presence of a thick, high-density material resting over the base of the crust in the entire stretch of the east-coast of India. (a) Gravity anomaly map, (b) magnetic (reduced to pole) anomaly map, (c) residual gravity map, (d) Isostatic anomaly map and (e) gravity-magnetic modelling. The residual gravity and horizontal gravity gradient signatures suggest that the orogenic systems encompassing the Cauvery Shear Zone and eastern part of the Eastern Granulite Mobile Belt may be a part of a common structural belt or tectonic regime associated with the assembly of the Gondwana supercontinent. The study also reveals magmatic under plating along east coast of India. [Display omitted] • Comprehensive potential field analysis of parts of Southern Indian Shield (SIS). • Outlines continuation and disposition of the greenstone belt and shear zones. • Continuation of structural belt from across different tectonic domains of the SIS. • The study reveals magmatic under plating along east coast of India. • Each geo-tectonic unit shows characteristic gravity-elevation relationship. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070152 [ABSTRACT FROM AUTHOR]

• The study proposes tools to improve environmental assessment of a mineral deposit. • XRF, mineral spectrometer, carbonate staining compose the preliminary protocol. • Application on two mining projects: a developed mine and an exploration project. • Protocol compared with traditional environmental assessment. Environmental assessment is generally performed when a mining project is at an advanced development stage, such as the prefeasibility study. It involves several laboratory tests such as detailed characterisation and geochemical mobility prediction tests, which require many samples considered representative of the deposit. Having early characterisation information could be useful to select the most relevant samples for the overall environmental assessment. The present study proposes a selection of non destructive and portable tools for improving the early environmental assessment of a mineral deposit. Three tools (x-ray fluorescence (XRF), mineral spectrometer, carbonate staining) were identified to form a preliminary environmental assessment methodology that can be performed directly on the exploration site. This methodology was applied to two different mining projects: i) a well developed mine, LaRonde zone 5, with available geochemical data in a volcanic-associated massive sulfide (VMS) context, and ii) an exploration project, O'Brien, with ongoing geochemical acquisition in an Au-quartz vein context. Both mine sites are in the south of the Blake River Group within the Abitibi greenstone belt, Quebec, Canada. The first site was used to validate the developed methodology, whereas the second acted as a test site to apply the methodology as a preliminary environmental assessment. The results on the first site confirmed that the selected tools provide geochemical and mineralogical data sets comparable to those of traditional testing methods. The developed methodology then enabled the classification of preliminary geo-environmental domains for the second site. Standard static and kinetic tests were performed on the second site samples to confront the preliminary assessment protocol. The proposed preliminary protocol made it possible to discriminate low-risk samples versus those with a potentially higher risk for the selection of subsequent environmental assessments. [ABSTRACT FROM AUTHOR]