Search Results (28)

Focusing on the West African Craton (WAC) as a test bed, this protocol-oriented scoping review synthesizes indicators for orogenic gold and translates them into an auditable, map-first checklist that separates Fertility and Preservation, while deliberately deferring any performance estimation to a blinded, out-of-sample evaluation. There is a need for a transparent, auditable, and field-ready framework that integrates geological, structural, geophysical, and geochemical evidence. We (i) synthesize the state of knowledge into a map-first, reproducible targeting checklist, (ii) formalize an indicator decision matrix that separates Fertility from Preservation factors, and (iii) specify a deferred, out-of-sample evaluation protocol to quantify performance. We conduct a Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR)-style scoping review (2010–2025) and codify commonly used indicators (e.g., transpressional jogs, lineament density, proximity to tonalite-trondhjemite-granodiorite (TTG)/tonalite contacts, Sr/Y proxies). Indicators are operationalized as auditable pass/fail rules and assembled into a decision matrix with explicit uncertainty handling and risk logging. We further define a deferred evaluation protocol using classification and ranking metrics (receiver operating characteristic (ROC) and precision–recall (PR) curves, odds ratios), ablation/sensitivity tests, and district-level threshold calibration. We deliver (1) a unified, auditable checklist with default (tunable) thresholds; (2) an indicator decision matrix that disentangles Fertility vs. Preservation signals; and (3) a deferred evaluation protocol enabling a reproducible, out-of-sample assessment without inflating apparent performance. All numerical thresholds reported here are explicit placeholders that facilitate transparency and auditability; they are not optimized. A properly blocked train/validation/test scheme, operating-point selection criteria, null models, and uncertainty procedures are prespecified for future evaluation. By publishing the checklist, data lineage, and audit-log schema now—without performance claims—we enable reproducible adoption and stress-test the framework ahead of calibration. Full article

The development of the continental crust during the Archean era is one of the key issues of geoscience. Determining the geological nature of the Archean terrane of the southern Liaoning Province (SLP) is fundamental to decipher the tectonic framework of the eastern North China Craton (NCC) from the late Neoarchean to Paleoproterozoic. The Archean assemblage of the SLP is composed of metabasalt, deformed diorite, TTG, and granite. Zircon U-Pb and Lu-Hf data constrain that the metabasalt formed at 2.52 Ga and was metamorphosed at 2.49 Ga. Dioritic rocks, TTG (tonalite-trondhjemite-granodiorite) and granite formed between 2.53 and 2.48 Ga. More than 85% of analyzed zircon grains yield ε_Hf(t) values intermediate between coeval CHUR and depleted mantle (DM). Their single-stage (T_DM) Hf model ages are dominantly between 2.90 and 2.58 Ga with a peak at 2.76–2.66 Ga, suggesting that the Archean assemblages of the SLP were derived from short-lived crustal sources with limited contributions from older materials. Geochemistry and zircon Lu-Hf systems indicate that these metamafic rocks have N-MORB and island arc-like tholeiitic affinities. Similar basaltic associations were identified from the Wutai greenstone belt. Intra-oceanic subduction and back arc basin extension can be ascribed to the generation of associated MORB-like and arc-related basalt. Along with the closure of the SLP back arc basin, an unknown terrane accreted to the south of the Longgang block at the end of the Neoarchean. Full article

The Huoqiu Group is located in the southern margin of the North China Craton and is considered an Archean geologic body. Its supracrustal rocks are divided into the Huayuan, Wuji, and Zhouji formations in ascending order. The Wuji and Zhouji formations contain large BIF-type iron deposits. The BIFs show geological and geochemical features of Paleoproterozoic Lake Superior-type rather than Archean Algoma-type. The study of the formation ages and evolutionary history of the Huoqiu Terrane will provide significant guidance for the mineralization and exploration of the Huoqiu iron deposits. In this paper, we collected all available isotopic ages and Hf isotopic compositions obtained from the Huoqiu Terrane and reassessed their accuracy and geological meanings. We conclude that the Wuji and Zhouji formations were not older than 2343 Ma. Therefore, the BIFs hosted in the Wuji and Zhouji formations must be of Paleoproterozoic age. The magmatic zircons from the TTG gneisses and granite yield U-Pb ages of Neoarchean Era, indicating that the Wuji and Zhouji formations of the Huoqiu Group were deposited on an Archean granitic basement that mainly comprises the trondhjemite-tonalite-granodiorite (TTG) gneisses and granites of the “Huayuan Formation”. The Early Precambrian crystalline basement in the Huoqiu area can be divided into the Huayuan Gneiss Complex and the Huoqiu Group, comprising the Wuji and Zhouji formations. The tectonic scenario of granitic complexes overlain by supracrustal rocks in the Huoqiu Terrane has been recognized in the Songshan, Zhongtiao, Xiaoshan, and Lushan Early Precambrian terranes in the southern margin of the North China Craton. As indicated by the zircon U-Pb ages and εHf(t) data, the crustal growth of the Huoqiu Terrane occurred mainly at ~2.9 Ga and ~2.7 Ga. Based on the sedimentary age, environment, and rhythm, the BIFs in the Huoqiu region are considered to be of Lake Superior type and of great potential for Fe ore exploration. Full article

The connection between crustal anatexis and magmatism is key to understanding the mechanisms that drive the evolution of the continental crust. Isotope geology and lithochemistry are important tools for reconstructing links between these processes, as field evidence of their connection is often obliterated by deformation in high-grade terrains. Thus, this study proposes new insights into the connection between the Mesoarchean regional metamorphism, crustal anatexis, and plutonism in the northern sector of the Carajás Province (i.e., Carajás Domain), in the Amazonian Craton, around 2.89 to 2.83 Ga. The widespread crustal anatexis in the Carajás Domain involved the water-fluxed melting of banded orthogneisses of the Xingu Complex and Xicrim-Cateté Orthogranulite (crystallization age at ca. 3.06–2.93 Ga), producing metatexites and diatexites with stromatic, net, schollen, and schlieren morphologies and coeval syntectonic leucosomes with composition similar to tonalites, trondhjemites, and granites. These leucosomes yielded crystallization ages of 2853 ± 5 Ma (MSWD: 0.61), 2862 ± 13 Ma (MSWD: 0.1), and 2867 ± 7 Ma (MSWD: 1.3). Their lithochemical data are similar to those of several diachronous Mesoarchean granitoids of the Carajás Domain in terms of major, minor, and trace elements and magmatic affinity. In addition, binary log–log vector diagrams (e.g., La vs. Yb; Rb vs. Yb), Sr/Y vs. Y, and Eu/Eu* vs. Yb plots indicate that plagioclase fractionation preceded melt extraction, establishing evolving source-to-sink trends between leucosomes and granites. These results show that the interplay between high-grade metamorphism, crustal anatexis, and magmatism may have shaped the evolution of the Mesoarchean continental crust in the Carajás Province, developing a petrotectonic assemblage associated with collisional orogens. The Mesoarchean geodynamic setting played a critical role in the development of coeval ca. 2.89 Ga magmatic–hydrothermal copper deposits in the Carajás Province, as well as Neoarchean world-class iron oxide–copper–gold deposits linked to post-orogenic extensional rebound. Full article

Although considered a crucial component of the Rodinia supercontinent, it remains uncertain how the Yangtze craton relates to the accretion and breakup of Rodinia. Here, the Huanglingmiao granitic complex (HGC), an intermediate-acid rock series that intruded on the southern Kongling terrane of the northern Yangtze craton margin, is investigated to help resolve this conundrum. Our analysis indicates that these rocks consist of tonalite, trondhjemite, granodiorite, oligoporphyritic granodiorite, porphyric biotite granodiorite, and fine- to medium-grained granodiorite dyke compositions. Collectively, this assemblage is further subdivided into two categories by their temporal, spatial, and geochemical features into early TTG-like and later granitic–dioritic units, which are composed of tonalite, trondhjemite, granodiorite, porphyritic granodiorite, and the fine- to medium-grained granodiorite dykes, respectively. Zircon U-Pb dating yields ages of 865~850 Ma for the TTG-like rocks, 844~825 Ma for the porphyritic granodiorites, and ~800 Ma for the granodiorite dykes. Combined with geochemical evidence, the data suggest that the early- and late-series rocks were formed by a partial melting of Mesoproterozoic and Paleoproterozoic crustal materials, respectively, suggesting that the vertical layering of the crust controlled the composition of the independent units. In addition, isotopic evidence points to different sources for the various rocks in the Kongling terrane and that mantle-derived materials influenced the early-series lithologies. Combined with previous studies on the northern margin of the Yangtze craton, it is inferred that the early-series rocks formed in an active continental margin environment, while the late-series rocks display within-plate boundary formation characteristics. The multiple magmatic activities revealed by this study record sequential partial melting with tectonic transition characteristics from an Andean-type to within-plate magmatism in the northern margin of the Yangtze craton. Taken together, these observations point to a strong association between these rocks, convergence, and incorporation of the northern Yangtze craton margin into the Rodinia supercontinent during the Tonian Period. Full article

The Bulfat Igneous Complex comprises the Bulfat and Walash groups and is situated in the Zagros Suture Zone, in the junction of Arabian and Eurasian plates. Zircon U-Pb data indicat an age of 63.7 ± 1.5 Ma for the trondhjemite rocks within the Bulfat group. Walash group is primarily composed of basalt to andesite rocks, interbedded with sedimentary rocks. Zircon U-Pb dating yields an age of 69.7 ± 2.7 Ma for the Walash group. Whole rocks chemistry shows that the Bulfat rocks have affinity to MORB and calc alkaline series but Walsh are mainly plot in the calc alkaline field. Whole rocks Sr-Nd isotope ratios show that the ¹⁴³Nd/¹⁴⁴Nd (i) changes from 0.51243 to 0.52189 and 87Sr/86Sr(i) ratios vary from 0.70345 to 0.7086. The calculated εNd(t) values, based on the CHUR, yield predominantly high positive values ranging from +6 to +8 for most samples. However, a few samples exhibit lower values (+2 to +3). Our data suggest that the interaction between lithospheric (depleted mantle, MORB-Like) and asthenospheric mantle (OIB-like) melts significantly controlled the magmatic evolution of the Bulfat group. The strong positive εNd(t) values (ranging from +6 to +8) align more consistently with a highly depleted lithospheric mantle source for the Walsh group. Therefore, the gradual transition from an arc signature at 70 Ma to a MORB signature around 63 Ma, occurred over a relatively short period of about 10 million years, and indicates the presence of an arc and back-arc system in the Neotethys ocean before the collision of the Arabian and Iran plates during the Cenozoic. Full article

The Alxa Block is an important component of the North China Craton, but its metamorphic basement has been poorly studied, which hampers the understanding of the Alxa Block and the North China Craton. In this study, we conducted geochronological and geochemical studies on three TTG (tonalite–trondhjemite–granodiorite) gneisses and one granitic gneiss exposed in the Langshan area of the eastern Alxa Block to investigate their crustal evolution. The zircon U-Pb dating results revealed that the protoliths of the TTG and granitic gneisses were formed at 2836 ± 20 Ma, 2491 ± 18 Ma, 2540 ± 38 Ma, and 2763 ± 42 Ma, respectively, and were overprinted by middle–late Paleoproterozoic metamorphism (1962–1721 Ma). All gneiss samples had high Sr/Y ratios (41–274) and intermediate Mg^# values (44.97–55.78), with negative Nb, Ta, and Ti anomalies and moderately to strongly fractionated REE patterns ((La/Yb)_N = 10.6–107.1), slight Sr enrichment, and positive Eu anomalies, displaying features of typical high-SiO₂ adakites and Archean TTGs. The magmatic zircons from the 2.84 Ga and 2.49 Ga TTG rocks had low ε_Hf(t) values of −1.9–1.7, and −3.83–2.12 with two-stage model ages (T_DMC) of 3.24–3.11 Ga and 3.10–3.01 Ga, respectively, whereas those from the 2.54 Ga TTG rock exhibited ε_Hf(t) values ranging from −1.1 to 3.46 and T_DMC from 3.0 Ga to 2.83 Ga, suggesting that the crustal materials of the basement rocks in the eastern Alxa Block were initially extracted from the depleted mantle during the late Paleoarchean to Mesoarchean era and were reworked in the late Mesoarchean and late Neoarchean era. By contrast, the Alxa Block probably had a relative younger crustal evolutionary history (<3.24 Ga) than the main North China (<3.88 Ga), Tarim (<3.9 Ga), and Yangtze (<3.8 Ga) Cratons and likely had a unique crustal evolutionary history before the early Paleoproterozoic era. Full article

Studies of lithotectonic formations within the Keivy domain of the NE Baltic Shield have shown that the domain was tectonically overlapped by adjacent microcontinents during regional collision processes in the Late Archean. As a consequence, the continental crust of the Keivy domain was submerged, relative to other blocks of the continental crust, and the described domain acquired the features of a classical median massif. Surrounded on all sides by collision systems, the Keivy median massif entered the cratonization regime. This led to intensive processes of denudation of the surrounding domains of the crust and the accumulation of a thick sedimentary cover on the surface. The described processes occurred during the formation of the first supercontinent (Monogea) in the history of the Earth and the manifestation of the Early Precambrian Huronian glaciation, which left its traces on most domains of the Earth’s continental crust. Thus, the processes of peneplain formation within the Keivy massif occurred under the cold weather conditions, high volcanic activity in the peripheral zones, and sedimentary cover saturation with the products of the physical and chemical mineral transformation of tonalite–trondhjemite and greenstone rock assemblages. The unique combination of certain geodynamic and climatic cycles on the Baltic Shield in the Late Archean led to the accumulation of extensive stratiform deposits of alumina raw materials within the Keivy median massif. Full article

Large-scale Mesozoic granitoids are exposed in the Greater Khingan Mountains. Their relationship with the Mongolia–Okhotsk and the Paleo-Pacific Ocean is still under discussion and a matter of debate. In this study, field observations were made and a total of 18 granitoids exposed in the vicinity of the Heihe–Baishilazi area in the northern part of the Greater Khingan Mountains were sampled for petrological, geochronological, and geochemical research. In addition, to complement this study, 90 granitic samples from the Xinghua, Dajinshan, Yili, Chabaqi, and Sankuanggou areas in the Greater Khingan Mountains were compiled in order to reveal rock assemblages, magma sources, and then inquire into the tectonic background. Zircon LA–ICP–MS U–Pb dating indicates that two samples from the Heihe area were formed in the Early Jurassic period (194.2 ± 1.4 Ma and 183.1 ± 1.3 Ma), and the εHf(t) values and TDM₂ of the zircons were mainly +5.8 to +10.7 and 528 Ma to 834 Ma, respectively, with a large variation range. The intrusive rocks from the Greater Khingan Mountains (108 in total) belonging to the T₁T₂G₁G₂ assemblage contained tonalites (T₁), trondhjemites (T₂), granodiorites (G₁), and granites (G₂). These granitoids are presented as subalkaline series in a plot of total alkali versus SiO₂ (TAS diagram), medium-K calc-alkaline and high-K calc-alkaline series on SiO₂ versus K₂O diagram, with metaluminous to peraluminous characteristics on an A/CNK versus A/NK diagram. These are shown as a MA (magnesium andesite) series and LMA (lower (or non) magnesium andesite) series on a SiO₂ versus MgO diagram, which can be further divided into the higher-pressure TTG subtype of the MA (corresponding to high-SiO₂ adakite (HSA)) series and the lower-pressure TTG subtype of LMA (corresponding to typical calc-alkaline suprasubduction zone rocks). In addition, granitoids were enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high-field-strength elements (HFSEs), corroborating a suprasubduction zone environment. Regional correlations as well as geochemical characteristics indicate that the rocks from the Greater Khingan Mountains formed in a subduction zone environment during the Early Jurassic; primary magma had presumably originated from the melting of young and hot oceanic crust under eclogite to amphibolite facies conditions. According to the spatial variation in rock assemblages (T₁T₂G₁ to G₁G₂ and G₂), we speculate that the northeastern Heihe, Baishilazi, and Xinghua areas as well as the westward Dajinshan area were adjacent to the ocean and formed an outer subduction zone, whereas the southwestward Sankuanggou, Yili, and Chabaqi areas were adjacent to the continent, forming an inner subduction zone. The distribution sites of the inner and outer subduction zones indicate southward and southwestward ocean subduction. Therefore, we propose a direct connection with southward subduction of the Mongolia–Okhotsk Ocean. Full article

Intra-oceanic subduction is a fundamental process on Earth, the study of which can improve the understanding of plate tectonic processes and the history of continental growth. Here, we report on newly recognized trondhjemite in the north of Diyanmiao ophiolite belt in North China. The trondhjemite was found along the Erenhot-Hegenshan suture zone. U-Pb zircon dating revealed that the trondhjemite crystallized at 309 ± 2.1 Ma. The trondhjemite had a high amount of SiO₂ (68.94–76.45 wt %), Al₂O₃ (13.37–15.90 wt %), and Sr (232–601 ppm); and a low amount of K₂O (1.57–2.70 wt %), Y (6.91–9.39 ppm), Ni (1.10–4.19 ppm), and Cr (1.55–13.50 ppm). The Na₂O/K₂O ratios were 1.90–4.37. There was a lack of negative Eu anomalies. It was relatively enriched in large-ion lithophile elements (LILEs) such as Rb, Ba, K, and Sr; was depleted in high-field-strength elements (HFSEs) such as Nb, Ta, Ti, and P; and had low total rare-earth element (REE) contents (27.73–49.63 ppm) with distinct REE fractionation (chondrite-normalized (La/Yb)_N of 5.76–10.52), which was similar to adakitic rocks formed by partial melting of subducted oceanic crust. The trondhjemite, together with Diyanmiao ophiolite (335.6 Ma), may have formed during the stages of intra-oceanic subduction, suggesting that in the Early Carboniferous–Late Carboniferous, the southern Paleo-Asian Ocean was in its subduction stage. Full article

Liuhe gold orefield is being newly explored in the southeast part of the Jiapigou gold ore belt, and occurs in the Neoarchean basement composed of trondhjemite–tonalite–granodiorite (TTG). Zircon U–Pb data suggest that the ore-hosting magma emplacement in the Liuhe orefield mainly took place in two epochs: late Neoarchean to early Paleoproterozoic (ca. 2500 Ma) and early Jurassic of the Mesozoic era (ca. 170 Ma). The TTG rocks show higher A1₂O₃ (12.58 to 15.71%) and Na₂O/K₂O ratios (1.16 to 2.9), and lower MgO (0.93 to 2.73%) and Mg# values, with positive Eu anomaly and low Y and Yb content, and high Sr/Y (22.3–79.6), and the plot in the adakite field in the Sr/Y-Y discriminant diagram belongs to the modern island-arc adakite rocks. Samples in this study are plotted in the pre-plate collision area in the R1-R2 discrimination diagram, and fall into the VAG and VAG + Syn-COLG field in the Rb-Y + Nb and Nb-Y diagram, respectively, indicating that the magmatism is related to plate subduction. The ore-bearing TTGs of the late Neoarchean to early Paleoproterozoic deposits were derived from the partial melting of mafic lower crustal caused by the underplating of basaltic magma on the island-arc or active continental margin before plate collision. The magmatism of the Dajiagou deposit occurred in active continental margin setting associated with the westward subduction of the paleo-Pacific plate beneath Eurasian Plate during the early Jurassic of Mesozoic period. Full article

Archean supracrustal rocks from the Qingyuan area of the northern Liaoning terrane, the North China Craton, occur as enclaves or rafts of various scales within tonalite–trondhjemite–granodiorite (TTG) domes. They were normally subjected to metamorphism at amphibolite facies with locally granulite facies. We collected biotite two-feldspar gneiss from the Hongtoushan of the Qingyuan area and conducted petrography, mineral chemistry, phase equilibrium modeling and monazite dating to reveal its metamorphic evolution. The peak condition was constrained to be 750–775 °C at ~7 kbar based on the stability of the inferred peak mineral assemblage and mineral compositions including the pyrite and grossular contents in the garnet core, and X_Mg in biotite. The final condition was constrained to be ~700 °C at ~6 kbar on the solidus based on the presence of muscovite in the final assemblage. The post-peak near-isobaric cooling process was consistent with the core→rim decreasing pyrite content in garnet. Monazite dating yielded a metamorphic age of ~2.50 Ga for the sample, coeval with the final magmatism of TTGs in the terrane. By combining other geological features, we suggest a vertical sagduction process to be responsible for the metamorphic evolution of the Qingyuan area. This process may be correlated with Archean mantle plume. Full article

Granitoid gneisses dominated by tonalitic–trondhjemitic–granodioritic (TTG) compositions, with metamorphic supracrustal rocks consisting of sedimentary and volcanic rocks, are widely exposed in the Eastern Hebei terrane, North China Craton (NCC). This study presents systematic zircon U–Pb geochronological and whole-rock geochemical data of the Neoarchean granitoid gneisses and supracrustal rocks in Eastern Hebei. Zircon U–Pb isotopic dating for the representative samples reveals that magmatic precursors of granitoid gneisses were emplaced between 2524 ± 7 and 2503 ± 12 Ma, and the protoliths of the pelitic granulites were deposited in the Late Neoarchean era. Both of them have been subjected to granulite facies metamorphism during 2508 ± 10 to 2468 ± 33 Ma, coeval with the intrusion of syenogranitic pegmatite (2488 ± 5 Ma). Zircon ages of 2.45–2.01 Ga obtained from the analyzed samples were considered mixed data from 2.53–2.48 Ga and 1.9–1.8 Ga and were chronologically meaningless. Paleoproterozoic metamorphic zircon ages of 1.9–1.8 Ga were usually neglected because of hardly being obtained from TTG gneisses and supracrustal rocks. The tectonic regime during the Neoarchean era was considered to be dominated by vertical tectonism in the Eastern Hebei terrane. Full article

We report the first radiogenic Nd-Sr isotope data in the magmatic rocks island-arc ophiolite assemblage from the middle branch of the East Sayan ophiolite complexes to better constrain geodynamic processes in this segment of the CAOB in southern central Siberia. The magmatic rocks belong to the following geochemical types: (1) Ensimatic island-arc boninites; (2) island-arc assemblage; (3) enriched basalts of mid-ocean ridges; and (4) oceanic island-like basalts. The boninites have a positive value εNd (T), which is generated from a depleted mantle source (N-MORB). The island-arc assemblage has negative or slightly positive εNd (T) and was formed from an enriched mantle source due to the subduction of terrigenous rocks. The source of the terrigenous material was most likely the rocks of the Archean TTG (Trondhjemite Tonalite Granodiorite) complex of the Gargan block. Isotopic ratios for E-MOR and OIB-like basalts are characterized by positive or slightly negative values of εNd (T). The mafic dike, which crosscut ophiolite rocks, corresponds to OIB-like basalts. The values of εNd (T), measured ⁸⁷Sr/⁸⁶Sr and I (Sr), in the mafic dike correspond to the EM I mantle source. The E-MOR and OIB-like basalts appear to be formed in late-stage asthenospheric mantle melting via the decompression melting processes. The obtained isotope geochemical data for the E-MOR and OIB-like basalts probably indicate the mixing of island-arc melts with asthenospheric melts. We undertook ⁴⁰Ar/³⁹Ar dating of the mafic dike, which crosscut the ophiolite unit. The mafic dike has a whole-rock ⁴⁰Ar/³⁹Ar weighted mean plateau age of 799 ± 11 Ma. The dating constrains the minimum age of the ophiolite and island-arc magmatism in the region. Full article

The Corno Alto–Monte Ospedale magmatic complex crops out at the eastern border of the Adamello batholith, west of the South Giudicarie Fault (NE Italy). This complex includes tonalites, trondhjemites, granodiorites, granites and diorites exhibiting an unfoliated structure suggesting passive intrusion under extensional-to-transtensional conditions. Major, minor elements, REE and isotopic analyses and geochemical and thermodynamic modelling have been performed to reconstruct the genesis of this complex. Geochemical analyses unravel a marked heterogeneity with a lack of intermediate terms. Samples from different crust sections were considered as possible contaminants of a parental melt, with the European crust of the Serre basement delivering the best fit. The results of the thermodynamic modelling show that crustal melts were produced in the lower crust. Results of the geochemical modelling display how Corno Alto felsic rocks are not reproduced by fractional crystallization nor by partial melting alone: their compositions are intermediate between anatectic melts and melts produced by fractional crystallization. The tectonic scenario which favored the intrusion of this complex was characterized by extensional faults, active in the Southalpine domain during Eocene. This extensional scenario is related to the subduction of the Alpine Tethys in the Eastern Alps starting at Late Cretaceous time. Full article