Precambrian Research最新文献

{"title":"Deciphering late Neoarchean orogenesis through structural analysis of the Taishan Group, eastern North China Craton","authors":"Xiaodong Li ,&nbsp;Wei Wang ,&nbsp;Zhonghua Tian ,&nbsp;Du Jia ,&nbsp;Fei Wen ,&nbsp;Fulai Liu","doi":"10.1016/j.precamres.2025.107944","DOIUrl":"10.1016/j.precamres.2025.107944","url":null,"abstract":"<div><div>The scientific community is currently engaged in an ongoing debate and controversy regarding the dominant mechanisms of Archean rock deformation, specifically whether it primarily occurred through vertical processes associated with sinking or through horizontal deformation involving subduction. The Western Shandong Province in the North China Craton represents a key area for investigating this question. In this study, we conducted detailed cross-section mapping and micro/mesoscale structural analysis of the Taishan Group within the central part of the Western Shandong Province. The D_A-1 structure exhibited an early foliation (S₁), while the D_A-2 structure showed F₂ folding, parasitic folds, S₂ crenulation cleavage and spaced cleavage. Furthermore, we identified thrust faults within the D_A-2 structure. The D_A-3 structure was defined by a shear zone and subsequent formation of kink bands. By integrating our geochronological data with regional tectonic information, we found that the D_A-1 deformation predated 2550 Ma, the D_A-2 deformation occurred between 2550 Ma and 2525 Ma, while the D_A-3 deformation took place between 2525 Ma and 2501 Ma. Our study demonstrates that the observed deformation phases produced by Archean orogenesis in the Taishan Group exhibit characteristics consistent with those found in modern orogenic belts. Consequently, we can conclude that the observed NNW-SSE linear structures result from horizontal movements produced by the plate tectonic system rather than dome-and-basin deformation in the Western Shandong Province.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107944"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sedimentology, petrography, and carbon isotopes of the ∼2.2 Ga Randville Dolomite, Upper Peninsula of Michigan","authors":"Garrett D. Brown ,&nbsp;Maya L. Giannecchini ,&nbsp;Cory M. Redman ,&nbsp;Ian Z. Winkelstern ,&nbsp;Dylan T. Wilmeth","doi":"10.1016/j.precamres.2025.107916","DOIUrl":"10.1016/j.precamres.2025.107916","url":null,"abstract":"<div><div>The Lomagundi–Jatuli Event (LJE) was Earth’s longest (2.3–2.0 Ga) and largest (+5 to +30 ‰) positive δ¹³C excursion. The LJE’s exact causes remain uncertain, with various hypotheses involving increased organic carbon burial or restricted depositional facies. While many LJE carbonates have enriched δ¹³C signatures, several locations are closer to average values over Earth history (∼0‰), providing opportunities to test depositional models. For example, the ∼2.2 Ga Randville Dolomite in Michigan’s Upper Peninsula is less enriched in δ¹³C (0 to +3 ‰) compared to the neighboring Kona Dolomite (+5 to +10 ‰). Randville age constraints are broad but fall within the LJE (2.3–2.1 Ga), approximately coeval with Kona deposits (2.17 Ga). The Randville Dolomite contains extensive planar beds with minor scour-fill structures, slumps, and conglomerates, indicating a relatively calm depositional environment punctuated by storms and slope failures on an outer carbonate platform. Randville deposits contain a variety of microbialites including domal, inclined, nodular, and conical stromatolites, and potentially the oldest recorded dendrolites. The most likely explanation for δ¹³C differences between the Randville and Kona Dolomite involves depositional environments. Many enriched Kona deposits represent an evaporitic, marine basin, while Randville facies show little to no evidence for subaerial exposure or evaporation. Facies-dependent patterns between Randville and Kona Dolomites are mirrored in LJE carbonates across the Lake Superior region: formations with evaporites are consistently δ¹³C-enriched compared with other localities. These datasets support previous research indicating that at least during certain intervals, LJE excursions were not ubiquitous in all marine environments.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107916"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of environmental pressures on stromatolite morphology: Insights from the Ediacaran Salitre Formation, Irecê Basin, Brazil","authors":"Jhon Willy Lopes Afonso ,&nbsp;Carolina Bedoya-Rueda ,&nbsp;Sergio Caetano-Filho ,&nbsp;Cristian Guacaneme ,&nbsp;Guilherme Raffaelli ,&nbsp;Mariane Candido ,&nbsp;Kamilla Borges Amorim ,&nbsp;Gustavo Macedo Paula-Santos ,&nbsp;Marly Babinski ,&nbsp;Ricardo Ivan Ferreira Trindade","doi":"10.1016/j.precamres.2025.107924","DOIUrl":"10.1016/j.precamres.2025.107924","url":null,"abstract":"<div><div>Stromatolites are laminated biosedimentary structures that record long-standing interaction between environmental conditions and coevolving microbial life. Although they are among the oldest and most persistent forms of life on Earth, the extent to which environmental parameters affect their morphology and distribution remains poorly understood. In this study, we investigated the well-exposed stromatolites of the Ediacaran Salitre Formation (Irecê Basin, Brazil) to assess how physical sedimentary processes and early lithification dynamics controlled stromatolite growth and form. Through integrated sedimentological and petrographic analyses, we documented a stratigraphic transition from stratiform to columnar morphologies, which closely correlates with variations in hydrodynamic energy, sediment influx, and local relief. Our results demonstrate that increased hydrodynamic energy and detrital input promoted the development of columnar, often inclined or branched forms, whereas low-energy conditions allowed for the development of stratiform structures, especially within protected scour depressions. The occurrence of inclined, yet unbroken stromatolite columns and their alignment with the paleoflow indicators suggest growth under dynamic, high-energy conditions with weak or incomplete synsedimentary lithification. Despite the high-energy setting, grains are concentrated only within the intercolumnar spaces and are almost absent from the stromatolite laminae, suggesting that lamination resulted primarily from microbial carbonate precipitation rather than sediment trapping. Additionally, the internal lamination patterns and detrital material distribution reflect episodic sedimentation and microbial mat disruption, further emphasizing the sensitivity of stromatolite morphology to environmental changes. Our findings highlight that the stromatolites in the Salitre Formation provide a valuable snapshot of the intricate interplay between physical parameters and biological activity during the terminal Neoproterozoic.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107924"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mesoproterozoic Pb loss in the 1.67 Ga Davis Dam Granite, northern Colorado River Extensional Corridor, USA","authors":"Elizabeth A. Bell","doi":"10.1016/j.precamres.2025.107917","DOIUrl":"10.1016/j.precamres.2025.107917","url":null,"abstract":"<div><div>Much of the Proterozoic crust in the Colorado River Extensional Corridor, southwestern USA has been extensively heated during Basin and Range extension. However, most thermochronology has been undertaken on the southern, most extended part of the corridor, with limited results suggesting less intense heating in the northern corridor, such that pre-Cenozoic medium-temperature Pb loss may be preserved in places. This study reports zircon and apatite U-Pb dating in the eastern region of the Paleoproterozoic Davis Dam Granite. This study searched for evidence of post-crystallization Pb loss in a region close to Miocene volcanic intrusions and faulting. Although zircon from three samples have average ages overall similar within error, with an overall average age 1665 ± 30 Ma, a small population of &gt; 1.7 Ga zircon in one sample may be xenocrystic. In all units, some 1.65–1.58 Ga Pb loss is suggested from a tail of younger concordant zircon ages, potentially reflecting metamorphic alteration during the Mazatzal orogeny. Variations among the three samples in zircon discordance behavior, overprinted/altered cathodoluminescence zoning, and the assemblages of secondary minerals filling cracks and void space in the zircon grains suggests geographic variation within the granite in post-crystallization alteration. Apatite have concordant ages ranging 1.7 to 1.2 Ga, with an average age of 1440 ± 132 Ma. The Davis Dam Granite preserves one or more post-Ivanpah and post-Mazatzal metamorphic events in the eastern Mojave province without overprinting by heating during Cenozoic Basin and Range extension in the northern Colorado River Extensional Corridor. Similar studies of older granitoids and their accessory minerals may better elucidate the Mesoproterozoic history of the northern Colorado River Extensional Corridor, its relationship with wider regional Mesoproterozoic tectonism, and the extent of Cenozoic overprinting.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107917"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of Marinoan-age glaciers in NW Tarim, China","authors":"Xiaoshuai Chen ,&nbsp;Hongwei Kuang ,&nbsp;Yongqing Liu ,&nbsp;Daniel Paul Le Heron ,&nbsp;Yuchong Wang ,&nbsp;Nan Peng ,&nbsp;Mingming Cui ,&nbsp;Kening Qi","doi":"10.1016/j.precamres.2025.107933","DOIUrl":"10.1016/j.precamres.2025.107933","url":null,"abstract":"<div><div>Glaciers were pivotal agents in shaping Cryogenian landscapes through erosional and depositional processes. Subglacial erosional forms serve as critical archives of glacial dynamics and thermal regimes, offering insights into paleoenvironmental interpretation and paleogeographic reconstruction. Cryogenian subglacial erosional forms are preserved on seven cratons globally, with China’s excellent example located in the Aksu-Wushi area of the northwestern Tarim Craton. A series of well-preserved erosional features of subglacial origin crop out, which until now have not been subject to systematic description or interpretation. This is redressed herein, and eight sites are surveyed in detail, enabling considerable insight into and unintegrated that have hindered research on Cryogenian glacial dynamics. In the Aksu-Wushi area, striations, grooves, p-forms, roches moutonnées, and glacial plucking morphologies, testify to both abrasion and meltwater processes at the ice-bedrock interface. A southwest-directed ice flow, with gradual southward deflection, is identified. Subglacial erosional forms and the overlying sedimentary successions documented in this study jointly reveal the depositional environmental evolution of the Yuermeinak Formation from subglacial to proglacial to post-glacial transgression, forming a complete record of continental ice sheet advance-retreat processes. The dynamic patterns and thermal regime of the Marinoan glacier further provide critical constraints for paleogeographic reconstruction. The consistent ice flow directions and sedimentary evolution observed in both the Yuermeinak Formation (Tarim) and Walsh Formation (Australia) collectively suggest that the Tarim was likely adjacent to the Australia during the Cryogenian period. The subglacial erosional forms and striated clasts at Aksu-Wushi area indicate a temperate glacial thermal regime during the latter stages of the snowball Earth event, compatible with a mid- to low-latitude paleogeographic setting. The massive gravel-bearing sandstone and siltstone with dropstones between the basal diamictite and overlying Ediacaran cap dolomite represents large-scale chemical weathering at the end of temperate glacier. Thus, paleo-glaciology can play a vital role in deep time paleogeographic reconstructions.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107933"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rhyacian (2218–2066 Ma) subduction-related volcanosedimentary accretion in the Western Bahia Orogenic Domain (São Francisco Craton, Brazil), and tectonic implications","authors":"Michel Macedo Meira ,&nbsp;Simone Cerqueira Pereira Cruz ,&nbsp;Elson Paiva Oliveira ,&nbsp;Joseneusa Brilhante Rodrigues ,&nbsp;Angela Beatriz de Menezes Leal ,&nbsp;Cristiano Lana","doi":"10.1016/j.precamres.2025.107925","DOIUrl":"10.1016/j.precamres.2025.107925","url":null,"abstract":"<div><div>New evidence from the northwestern São Francisco Craton sheds light on Paleoproterozoic tectonic evolution in the Minas-Bahia Orogen. Two metavolcanosedimentary sequences—the Boqueirão de Baixo and Chapada Grande formations—record stages of a Rhyacian orogenic system, characterized through integrated stratigraphic, petrographic, geochemical, geochronological, and isotopic data. The metavolcanic rocks of the Boqueirão de Baixo Formation consist mainly of fine-grained tholeiitic amphibolites, with juvenile zircon Ɛ_Hf(t) values (+3.78 to + 5.6), which crystallized at 2218 ± 18 Ma and were metamorphosed at 2020 ± 7 Ma. The Chapada Grande Formation comprises metasedimentary rocks and calc-alkaline to ultrapotassic mafic to intermediate metavolcanics, with crystallization ages between 2096 ± 20 Ma and 2066 ± 6 Ma and evolved isotopic signatures (Ɛ_Hf(t) −18.5 to −8.84). These formations developed in a continental arc setting along the eastern margin of the Bom Jesus da Lapa Terrane, with the metasedimentary rocks recording forearc, intra-arc, and passive margin deposition. Post-collisional sinistral strike-slip shear zones subsequently generated a pull-apart basin, which favored sediment deposition and the emplacement of the Guanambi Syenite Suite. This study refines the tectonic evolution of the Minas–Bahia Orogenic System and provides new insights into Rhyacian–Orosirian orogenic belts and the early assembly of the Columbia Supercontinent.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107925"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temporal and magmatic evolution of the Neoproterozoic ultramafic and mafic Ougda arc complex and associated granitoids (Western Tuareg Shield, Algeria)","authors":"Chaouki Djallel Eddine Bendimerad ,&nbsp;Abderrahmane Bendaoud ,&nbsp;Julien Berger ,&nbsp;Renaud Caby ,&nbsp;Gaston Godard ,&nbsp;Karel Schulmann","doi":"10.1016/j.precamres.2025.107903","DOIUrl":"10.1016/j.precamres.2025.107903","url":null,"abstract":"<div><div>The Ougda area, located within the Tassendjanet terrane of the Western Tuareg Shield, hosts a large (ultra)mafic complex associated with granitoid intrusions. This magmatic complex represents a Neoproterozoic continental arc, active between 749 ± 2 Ma and 653 ± 4 Ma ago; during this time, various ultramafic and mafic (meta)cumulates (serpentinites, hornblendites, garnet amphibolites, amphibolites and leucogabbros) and non-cumulates (amphibole gabbros, quartz diorites, diorites) were emplaced. The latter exhibit a calc-alkaline affinity. Sr-Nd isotope data reveal a distinct contrast between North and South Ougda ultramafic and mafic units. The North Ougda units have a more juvenile signature (<em>ε_Nd</em> = +6.3 to +9.4, <em>ISr</em> = 0.70248–0.70377) than the South Ougda units (<em>ε_Nd</em> = +5.3 to +6.3, <em>ISr</em> = 0.70267–0.70400). Early arc construction is represented by the emplacement of the South Ougda units into a thinned juvenile crust at shallow crustal levels. In contrast, the younger and more juvenile North Ougda units were emplaced at deeper crustal levels, likely at the base of the arc crust.</div><div>Syn-collisional granitoids, dated at 626 ± 5 Ma and 627 ± 4 Ma, intruded the Tassendjanet terrane and show a hybrid juvenile-crustal signature (<em>ε_Nd</em> = +2.68 to −8.04, <em>ISr</em> = 0.70296–0.70743), interpreted as resulting from the partial melting of juvenile basaltic rocks in the lower crust of the Ougda arc, followed by the crustal contamination of primitive magmas. In addition, aplitic dykes crosscutting these granitoids display geochemical characteristics similar to those of the post-collisional granites that sealed the Panafrican orogeny in the Tuareg Shield. The Ougda continental arc complex is believed to have formed during the closure of an oceanic basin, leading to the amalgamation of West Gondwana and ultimately to the Pan-African orogeny observed across the Neoproterozoic NW African provinces.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"430 ","pages":"Article 107903"},"PeriodicalIF":3.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145027881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"U–Pb zircon geochronology and geochemistry of Um Genud layered mafic intrusion in the northern tip of the Arabian-nubian shield: implications for the genesis of the plutonic crust of neoproterozoic immature intra-oceanic arc","authors":"Tarek H. Abu El-Kheir ,&nbsp;Keda Cai ,&nbsp;Ayman E. Maurice ,&nbsp;Kai Wang ,&nbsp;Hairuo Wang ,&nbsp;Maher Dawoud","doi":"10.1016/j.precamres.2025.107915","DOIUrl":"10.1016/j.precamres.2025.107915","url":null,"abstract":"<div><div>The Um Genud Neoproterozoic layered mafic intrusion, located in the South Eastern Desert of Egypt, represents the northwestern tip of the juvenile crust of the Arabian-Nubian Shield (ANS). This intrusion is composed of olivine gabbro, gabbro, noritic-gabbro and hornblende gabbro. Zircon U–Pb data constrain the emplacement age of the intrusion to 718 Ma, coinciding with the island arc stages of the ANS. The trace element patterns of pyroxenes, amphiboles, whole-rock samples and calculated melts in equilibrium with clinopyroxene and amphibole show marked Nb-Ta and Zr-Hf troughs and prominent peak of Pb. These features, along with the trace element abundances and ratios in zircon, suggest that the parental magma was generated in an intra-oceanic island arc setting from a depleted mantle source metasomatized by subducted slab-derived aqueous fluids. Textural features, mineral compositions of olivine, pyroxene and plagioclase, whole-rock geochemical characteristics, the calculated ƒO₂ values (FMQ + 1 – FMQ + 1.6), and the estimated water content (5.9 – 9.1 wt%) of melt indicate that the Um Genud gabbroic rocks represent cumulates differentiated from oxidized hydrous low-K tholeiitic magma, essentially by fractional crystallization. The estimated pressure of crystallization (∼3 to ∼ 3.5 kbar; ∼10 km depth), the low-K tholeiitic nature of parental magma and the relative abundance of the exposed gabbroic and granitic arc rocks in the study area are consistent with intrusion emplacement within the lower crust of an immature oceanic arc. This implies that even arcs with thin crust can develop considerable plutonic layers and contribute to continental crust growth through vertical accretion.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"429 ","pages":"Article 107915"},"PeriodicalIF":3.2,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kilometer-scale hook-shaped Type2/Type3 folds due to refolding and transpressional strike-slip reversal in the Egyptian Nubian Shield, east African orogenic belt","authors":"Mohamed A. Abd El‑Wahed ,&nbsp;Ahmed M. Eldosouky ,&nbsp;Osama M.K. Kassem ,&nbsp;Ahmed Abdelhady Abo-Rayan ,&nbsp;Mohamed Attia","doi":"10.1016/j.precamres.2025.107912","DOIUrl":"10.1016/j.precamres.2025.107912","url":null,"abstract":"<div><div>This study combines remote sensing, aeromagnetic data, and field investigations to provide the initial identification of hook-shaped Type 2/Type 3 folds within the Egyptian Nubian Shield. The Western Allaqi shear belt (WASB) exhibits remarkable refolded structures that are distinctly observable from space. This belt primarily comprises ophiolite slices, metavolcanics, and volcanoclastic metasediments, which have been intruded by syn- (729–635 Ma) and post-tectonic granites (610–543 Ma). The WASB region experienced significant compression during the N-S shortening (830–720 Ma), leading to the formation of east–west oriented folds and foliation and N-dipping thrust imbrications. The interference patterns of the folds predominantly display Type 2 and Type 3 refolds characterized by wavelengths on the order of kilometers. The geological observation reveals a complex history of deformation, with refolded folds linked to dextral shear zones, ductile and brittle fabrics, and opposing movement directions. The fold interference structures were formed through the reactivation of NW-trending sinistral strike-slip shear zones, combined with shear-related folding of the initial F₁ folds, and NE-SE compression (625–565 Ma). The subsequent development of NW-trending Haseierbah folds (F₂) was accompanied by a shift in stress orientation from NE-SW to E-W (620–580), resulting in a reversal of shear sense and the reactivation of NW-trending shear zones into dextral strike-slip shear zones, which in turn formed the N-trending El-Quleib fold (F₃) and the NE-trending Haimur and Shilman folds (F₄). This reversal in shear sense contributes to the formation of Type 2 and Type 3 fold interference patterns and the distinctive hook-shaped fold structures observed within the WASB. This study provides a detailed description of refolding and transpressional strike-slip reversal in the WASB, highlighting the innovative tectonic evolution and urging a reassessment of the entire Allaqi-Heinai suture and the major shear zones in the Egyptian Nubian Shield.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"429 ","pages":"Article 107912"},"PeriodicalIF":3.2,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145005224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paired metamorphic belts in the Usagaran Orogen of Tanzania: evidence for one-sided oceanic subduction in the Palaeoproterozoic","authors":"V. Schenk ,&nbsp;T. Sarkar ,&nbsp;D. Wiemer","doi":"10.1016/j.precamres.2025.107891","DOIUrl":"10.1016/j.precamres.2025.107891","url":null,"abstract":"<div><div>Paired metamorphic belts (PMB) are the tectono-metamorphic expression of the one-sided subduction of oceanic lithosphere beneath continental margins and island arcs, which represents a key characteristic of terrestrial plate tectonics. PMB that are spatially and timely paired are mainly known from Phanerozoic orogenic belts, although the metamorphic rock record points to a duality of thermal regimes since the Palaeoproterozoic. Here we describe the tectono-metamorphic evolution of the Usagaran Orogen at the SE-margin of the Tanzania Craton, which includes PMB of Palaeoproterozoic age. The orogen’s lithological inventory reflects a Wilson cycle: (1) The passive margin sequence (Konse Group) was deposited during the Lomagundi carbon isotope excursion (2.22–2.06 Ga) and metamorphosed at 2.03 Ga during the Usagaran orogeny. (2) The precursors of most eclogites were ocean-floor basalts, but those of the Ky- and Opx-eclogites of boninite chemistry were related to subduction-initiation. Peak eclogite metamorphism at mantle depths (850–880 °C/18–19 kbar) was followed by transient granulite-facies conditions during exhumation (750–800 °C/6–10 kbar). High-<em>T-P</em> shear zones in Opx-eclogites and felsic mylonites formed at P &lt; 15 &gt; 10 kbar are related to exhumation. (3) High-P amphibolite-facies metamorphism of metasediments enveloping the eclogite belt (770 °C/13.2 kbar at 2.0 Ga) is attributed to an accretionary wedge setting. The concurrent evolutions and the preserved growth zonations in garnet of both units point to a shared short-lived metamorphism. (4) Low-P Grt-Crd-Sil-granulites, which overlie the accretionary wedge metasediments as a nappe, experienced a counter-clockwise <em>P-T</em> path at ca. 2.06 Ga (peak 820 °C/7.2 kbar) in an arc setting that predates the orogeny for 50–60 Myr. We attribute their protomylonitic texture to post-peak NW-thrusting towards the orogenic foreland during collision. Late-stage <em>P-T</em> paths of all units in the nappe stack (isobaric cooling at 20 km depth) are interrelated. Other Palaeoproterozoic PMB in orogens around the Congo Craton and in the Yangtze Craton, in addition to subduction-related eclogites in the Trans-North China Orogen, indicate that subduction of oceanic lithosphere and its partial exhumation after slab breakoff at mantle depths were already viable tectonic processes. Pre-Neoproterozoic eclogites representing exhumed oceanic crust are dominantly known from a short time interval (2.1–1.8 Ga), during which warm (12–14 °C/km) and cold (&lt;11 °C/km) subduction zones existed, which both show the tectono-metamorphic characteristics akin to modern asymmetric one-sided oceanic subduction.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"429 ","pages":"Article 107891"},"PeriodicalIF":3.2,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145020962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}