Precambrian Research最新文献

{"title":"Identification of the Shuanglongtan tectonic mélange (ca. 1.7–1.5 Ga) in the southwestern Yangtze Block and it’s tectonic implications","authors":"Jun-Ping Liu ,&nbsp;Zai-Bo Sun ,&nbsp;Xiao-Hu He ,&nbsp;Jiang-Tai Zhao ,&nbsp;Shi-Jun He ,&nbsp;Ling-Jing Bi ,&nbsp;Wei-Ke Li","doi":"10.1016/j.precamres.2024.107658","DOIUrl":"10.1016/j.precamres.2024.107658","url":null,"abstract":"<div><div>The Yangtze Block hosts large quantities of late Paleoproterozoic to early Mesoproterozoic mafic rocks, which are considered to be related to the breakup of the Nuna supercontinent. This study identified a tectonic mélange suite within the Shuanglongtan fault zone (also referred to as the Shuanglongtan tectonic mélange) in the southwestern Yangtze Block. Field observations and rock assemblages suggest there are five litho-tectonic units within the tectonic mélange: ultramafic rocks (pyroxene peridotites and picrites), mafic dikes (gabbros and diabases), <em>meta</em>-basalts and pelagic sediments, ocean-island basalts (OIBs) and seamount sediments (marbleized limestones), and exotic blocks (grayish-purple metasandstones and siltstones with hematite mineralization). These litho-tectonic units experienced greenschist to low amphibolite facies metamorphism, as revealed by the mylonitized and lineated structures. The zircon U-Pb dating indicates that these mafic volcanic rocks within the tectonic mélange were formed from the late Paleoproterozoic to the early Mesoproterozoic (1728 ± 27 to 1493 ± 12 Ma). These rocks, formed by the 5 %–15 % partial melting of a mantle source composed of spinel-garnet lherzolites, can be classified into enriched mid-ocean ridge basalt (E-MORB)-like and OIB-like <em>meta</em>-basalts based on their geochemical features. In combination with previous studies and current observations, this study proposes that the Shuanglongtan tectonic mélange emerges as the eastward extension of the Caiziyuan ophiolite mélange and that the Yangtze Block was divided into the eastern and western portions by an oceanic basin from the late Paleoproterozoic to the early Mesoproterozoic.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107658"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137426","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":"Spatio-temporal tectonic progression in the Dharwar Craton: Insights from volcanic records of Archean greenstone belts","authors":"G. Harshitha ,&nbsp;Jayant K Yadav ,&nbsp;C. Manikyamba ,&nbsp;M. Santosh ,&nbsp;Li Tang ,&nbsp;K.S.V. Subramanyam","doi":"10.1016/j.precamres.2024.107674","DOIUrl":"10.1016/j.precamres.2024.107674","url":null,"abstract":"<div><div>Volcanic episodes serve as precursors for the formation and evolution of continental crust and directly impact the mantle compositions. Here, we present elemental, zircon U-Pb and Sm-Nd isotopic datasets of published and newly generated data on the Archean volcanic sequences from the Dharwar Craton and constrain the thermal and chemical evolution of the Archean mantle, continental growth, geodynamic evolution and craton formation. The data reveal three phases of ultramafic volcanism at 3.4–3.25 Ga, 3.2–3.05 Ga and 2.7–2.6 Ga; two major phases of mafic volcanic activity at 3.35–3.15 Ga and 2.75–2.5 Ga, and three felsic volcanic episodes at 3.4–3.2 Ga, 2.9–2.7 Ga and 2.65–2.5 Ga, which are associated with granitoid formation at ca. 3.4–3.25 Ga, 3.1–3.0 Ga, 2.7–2.6 Ga and 2.56–2.54 Ga. The εNd(t) values of +2 to +6 and εHf(t) values of −5 to ∼10 of these suites depict heterogeneous mantle reservoirs. These temporal isotopic variations are further constrained spatially through elemental ratios, which suggest the origin of ultramafic melts from deeper, primitive to highly depleted mantle reservoirs, with traces of crustal contamination.</div><div>The origin of the Paleo- to Neoarchean (3.4–2.54 Ga) volcanism in the Dharwar Craton is explained through the evolving tectonics in the early Earth, where mantle plume activity initiated ultramafic volcanism. A decrease in temperature and pressure, an increase in the degree of partial melting, and a compositional change in the komatiites are consequences of the thermal evolution of the mantle within the Paleoarchean to Neoarchean timeframe. Among the arc basalts, the first two phases that are the melt products of enriched mantle, reflect the subduction of oceanic plateau-type proto-crust. The third phase, representing enriched to depleted mantle sources, supports the existence of an array of oceanic to continental arcs. The three phases can be correlated with tectonic stages involving predominant plume-subordinate arc (Stage I), subordinate plume-predominant arc (Stage II) and prevalent arc (Stage III) volcanism, followed by the accretion of arcs and craton formation spanning the Paleo- and Neoarchean timeframe. These studies reveal that the Dharwar Craton has formed through successive stages of greenstone volcanism and plutonism in a transient tectonic environment.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107674"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137577","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":"Latest Mesoproterozoic arc-related granitoid magmatism in the southwestern Yangtze Block, South China: Petrogenesis and geodynamic implications","authors":"Mingda Huang ,&nbsp;Xiaozhuang Cui ,&nbsp;Guangming Ren ,&nbsp;Qi Deng ,&nbsp;Fenglin Chen ,&nbsp;Junwei Yang ,&nbsp;Tao Li ,&nbsp;Zhiming Sun","doi":"10.1016/j.precamres.2024.107635","DOIUrl":"10.1016/j.precamres.2024.107635","url":null,"abstract":"<div><div>The geodynamic setting of the southwestern Yangtze Block in the latest Mesoproterozoic has been a controversial issue for decades, which confuses the relationship between the Yangtze Block and the assembly of Rodinia supercontinent. We here report an integrated dataset of petrology, whole-rock geochemistry, zircon U-Pb ages and Hf isotopes for the newly identified latest Mesoproterozoic granitoids from the Yonglang area, southwestern Yangtze Block. SHRIMP and LA-ICP-MS zircon U-Pb dating results suggest that these granitoids were mainly crystallized at ca. 1.02 Ga. These samples show typical geochemical signatures of I-type granite, such as negative correlation between P₂O₅ and SiO₂ contents, positive correlation between A/CNK ratios and SiO₂ contents, and zirconium saturation temperature (<em>T</em>_zr) of 748–818 °C. Their zircon ε_Hf(t) values range from −3.0 to 0.8, with two-stage model ages of 2.0–1.8 Ga. These ca. 1.02 Ga granitoids were likely generated by the partial melting of amphibolites under H₂O-rich conditions originated from hydrous fluids of the subduction components, reinforced a latest Mesoproterozoic arc-back-arc system in the southwestern Yangtze Block. Based on the spatial–temporal variations of the late Mesoproterozoic subduction-related magmatic records around the periphery of the Yangtze Block, it is suggested that this block may have started to drift towards the Rodinia supercontinent at least at ca. 1.02 Ga.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107635"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137506","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":"Depositional age and tectonic setting of the Dimunalike iron formation in southeast Tarim Craton: Implications for the resurgence of Neoproterozoic iron formations","authors":"Xiang Li ,&nbsp;Ru-Xiong Lei ,&nbsp;Matthew J. Brzozowski ,&nbsp;Hui Ye ,&nbsp;Xiu-Fang Wang ,&nbsp;Zhi-Hua Zhang ,&nbsp;Chang-Zhi Wu","doi":"10.1016/j.precamres.2024.107665","DOIUrl":"10.1016/j.precamres.2024.107665","url":null,"abstract":"<div><div>Proterozoic iron formations (IFs) largely formed during the Paleoproterozoic and Neoproterozoic eras. It remains unclear why IFs reappeared in Neoproterozoic successions globally after a depositional gap of more than one billion years. Tonian IFs can help clarify this ambiguity as they were deposited during a transitional period when IFs reemerged. In this study, we report new geochronological and geochemical data of metavolcanic rocks interbedded with a Tonian IF — the Dimunalike IF — in the southeast portion of the Tarim Craton to i) constrain the depositional age and tectonic setting of this IF, and ii) provide new insights into the resurgence of IF deposition in the Neoproterozoic. Zircons from metavolcanic rocks yield a U–Pb weighted mean age of 745.2 ± 1.6 Ma (MSWD = 0.81), indicating that the Dimunalike IF formed in the late Tonian. The metavolcanic rocks exhibit geochemical signatures similar to within-plate alkalic basalts, being characterized by high Zr contents (233–254 ppm) and Zr/Y ratios (6.62–7.08). Considering the Hf isotope composition of zircons from the metavolcanic rocks, as well as igneous rocks throughout the Tarim Craton, it is suggested that the Dimunalike IF was deposited in a rift basin related to the breakup of the Rodinia supercontinent. With an age of approximately 745 Ma and no signs of glacial influence, the Dimunalike IF demonstrates that extensive IF deposition occurred prior to the Cryogenian. Our new data support the idea that, rather than glaciations, hydrothermal processes and mafic volcanism were crucial to the resurgence of Neoproterozoic IFs by enhancing ferruginous conditions in oceans.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107665"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137509","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":"Petrogenesis of 3.3–3.1 Ga granitoids in the Anshan continental nucleus, North China Craton: Implication for multi-stage magmas underplating processes","authors":"Yufei Xuan ,&nbsp;Jin Liu ,&nbsp;Zhenghong Liu ,&nbsp;Zhongyuan Xu ,&nbsp;Gang Li ,&nbsp;Xiaojie Dong ,&nbsp;Pengchuan Li ,&nbsp;Hongxiang Zhang","doi":"10.1016/j.precamres.2025.107712","DOIUrl":"10.1016/j.precamres.2025.107712","url":null,"abstract":"<div><div>Archean tonalite-trondhjemite-granodiorite (TTG) suite and K-rich granitoids provide direct evidence of the generation and differentiation of the Archean continental crust. Within the North China Craton (NCC), the Anshan area serves as an exceptional natural laboratory, preserving a geological record spanning from 3.8 to 2.5 Ga. Here, we conducted comprehensive geochemical, geochronological, and zircon Hf–O isotopic analyses for the Paleoarchean–Mesoarchean granitoids from the Anshan region. Zircon U–Pb dating suggest that these granitoids formed during 3.3–3.1 Ga. The <em>ca.</em> 3.3 Ga monzogranitic gneisses exhibit high SiO₂ and K₂O, low Mg# values, negative Eu anomalies, unradiogenic Hf isotopes (i.e., ε_Hf(<em>t</em>) values = -5.16–+0.08, T_DM² age = 4264–3729 Ma), and “mantle-like” δ¹⁸O values (up to + 5.64 ‰). Geochemical features divide them into two distinct groups, both are recycling products of pre-existing Eoarchean TTGs. Group 1 and Group 2 originated from 10 %–20 % and 20 %–30 % partial melting of pre-existing Eoarchean TTGs at depths of 1.25–1.75 GPa and 0.5–0.75 GPa, respectively. The <em>ca.</em> 3.3 Ga trondhjemite gneisses show high SiO₂, low Mg# values, low Sr/Y and (La/Yb)_N ratios. Their ε_Hf(<em>t</em>) values range from + 0.91 to + 1.10, with T_DM² ages of 3682–3665 Ma. In contrast, the <em>ca.</em> 3.3 Ga monzonitic gneisses have lower SiO₂ contents, higher Al₂O₃, total alkali (Na₂O + K₂O), and Sr/Y and (La/Yb)_N ratios. Their ε_Hf(<em>t</em>) values range from −2.69 to + 0.50, with T_DM² ages of 4040–3750 Ma. The <em>ca.</em> 3.1 Ga trondhjemite gneisses display higher Sr/Y and (La/Yb)_N ratios, enriched LREEs and depleted HREEs. Magmatic zircons yield δ¹⁸O values of 3.87–6.52 ‰ and ε_Hf(<em>t</em>) values of −2.39 to + 0.95, with T_DM² ages of 3881–3550 Ma. The geochemical and Hf-O isotope characteristics suggest that both the 3.3–3.1 Ga trondhjemite gneisses and the <em>ca.</em> 3.3 Ga monzonitic gneisses originated from partial melting of mafic rocks at variable depths. During 3.3–3.1 Ga, the NCC experienced intensive crustal growth and rework/recycling. Two magmatic events (<em>ca.</em> 3.3 Ga and <em>ca.</em> 3.1 Ga) and subsequent tectono-thermal events were induced by multi-stage magmatic underplating of mantle upwelling within a plume-related tectonic setting.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107712"},"PeriodicalIF":3.2,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096740","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":"Concentration of cobalt in IOCG systems: Exemplified by the Proterozoic Kangdian IOCG metallogenic province, SW China","authors":"Lei Liu ,&nbsp;Wei Terry Chen ,&nbsp;Chao Wang","doi":"10.1016/j.precamres.2025.107699","DOIUrl":"10.1016/j.precamres.2025.107699","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Cobalt was defined as an important strategic metal by major industrial countries. The clan of iron oxide copper–gold (IOCG) deposits has been documented to be a potentially important Co provider (predicted to be accounting for &gt; 10 % of continental Co resources), but the mechanism for Co concentration in IOCG systems is still poorly constrained. In this study, we conducted a combined geological, mineralogical and geochemical investigation on the Co enrichments/mineralization in the Lala, Dahongshan and Yinachang deposits from the Proterozoic Kangdian IOCG metallogenic province, SW China (with an estimated total Co resource of &gt; 70,000 t). These deposits have a similar paragenesis consisting of early Fe-oxides and late Cu-sulfides mineralization stages. This study revealed that Co in these deposits is mainly hosted in pyrite, with the way by substituting for Fe&lt;sup&gt;2+&lt;/sup&gt;. The Co-rich pyrite grains in the Lala deposit have formed in two generations. The early generation (Py I; 5432 to 27,883 ppm Co), clearly predating the Fe-Cu mineralization, is characterized by massive pyrite bands concordant with the hosting strata, and thus were suggested to be &lt;em&gt;syn&lt;/em&gt;-sedimentary in origin. These grains were commonly overprinted by late Fe-Cu mineralization through a fluid-aided dissolution-reprecipitation process during which the primary Co in Py I were leached. The second generation of Co-rich pyrite (Py II; 2152 to 8329 ppm Co) was closely associated with Cu-sulfides of the Cu mineralization. On the other hand, only one generation of Co-rich pyrite was present in the Dahongshan and Yinachang deposits, and are synchronous with the Cu mineralization.&lt;/div&gt;&lt;div&gt;Chemical and S isotopic compositions show that all the Co-rich pyrite grains from the Lala (both Py I and Py II), Yinachang and Dahongshan deposits have a notable S isotopic peak value around at ∼ 3 ‰ with similar high Co/Ni (mostly &gt; 1), but low Mo/Ni (mostly &lt; 0.001) ratios, indicating strong affinities of mafic provenances for the Co metals. The Co in the sedimentary Py I grains of Lala was constrained to be likely related to the coeval mafic volcanic activities (as potential Co sources). On the other hand, the Co of the Cu stage in the Lala (i.e. Py II), Dahongshan, and Yinachang deposits were suggested to be sourced from coeval mafic magmas or hosting mafic rocks through fluid-rock interaction. However, the former source could be insignificant, as the potential Co contents of the mafic magma-derived fluids were estimated to be lower than 12.0 ppm. In contrast, our mass balance calculation strongly confirmed that large amounts of Co in the mafic hosting rocks were mobilized or leached during fluid-rock interaction. Considering that such kind of Fe or Cu mineralizing fluids are comparable in various IOCG deposits (e.g., high salinity, NaCl-rich), we further proposed that the Co budgets of hosting rocks would be the first key factor controlling variable Co enrichments/min","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107699"},"PeriodicalIF":3.2,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140510","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":"Spatiotemporal fluctuations of pyrite sulfur isotope with pyrite morphology during the Ediacaran-Cambrian transition","authors":"Shengxian Zhu ,&nbsp;Mingshi Feng ,&nbsp;Kun Zhao ,&nbsp;Songzhuo Li ,&nbsp;Jiaxu Hou ,&nbsp;Kaiyun Ye ,&nbsp;Wanbin Meng ,&nbsp;Xianguo Lang","doi":"10.1016/j.precamres.2025.107704","DOIUrl":"10.1016/j.precamres.2025.107704","url":null,"abstract":"<div><div>The rapid fluctuations in the bulk-sample sulfur isotope of sedimentary pyrite (δ³⁴S_py) serve as a crucial indicator of marine redox changes during the Ediacaran-Cambrian transition (E-C). However, these bulk δ³⁴S_py values are susceptible to diagenetic alterations, which can alter the ratio of euhedral to framboidal crystals, thereby inducing fluctuations in δ³⁴S_py values. To assess the impact of diagenesis on δ³⁴S_py variability across the E-C transition, we conducted a comprehensive analysis of spatiotemporal variations in δ³⁴S_py across five E-C sections in South China, encompassing diverse environmental settings. Additionally, we characterized pyrite morphologies, distinguishing between framboidal and non-framboidal forms. The results demonstrate a consistent decrease in δ³⁴S_py values with increasing water depth, accompanied by an increase in the proportion of framboids. Specifically, in shallow water platform settings, the mean δ³⁴S_py value is + 34.0 ‰, with a mean framboid proportion of 6 %. Conversely, in the deep water basin environment, the mean δ³⁴S_py value drops to + 5.6 ‰, with a mean framboid proportion of 45 %. A positive δ³⁴S_py excursion, ranging from + 5.1 ‰ to + 51.0 ‰, is observed in the platform at the base of the E-C transition, while a negative excursion, spanning from + 13.0 ‰ to −28.2 ‰ (and from + 14.9 ‰ to −19.5 ‰ in another section), is evident in the basin. Crucially, a consistent negative correlation is observed between framboid proportions and bulk δ³⁴S_py values. This relationship underscores the significance of both the timing of pyrite formation and its local redox condition. Our findings reveal that marine oxidation occurred in uneven pulses during the E-C transition. Furthermore, we emphasize the necessity of considering pyrite morphologies when interpreting δ³⁴S_py records, as framboids may offer a more reliable signal of seawater conditions. Overall, this study provides new insights into the complex interplay between diagenetic alterations, pyrite morphology, and marine redox variations during the E-C transition, underscoring the dynamic nature of marine oxidation during this critical period in Earth’s history.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107704"},"PeriodicalIF":3.2,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140549","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":"Tectonometamorphic history across the Chesterfield Fault Zone: Implications for tectonic evolution of the Rae Craton, Nunavut, Canada","authors":"Derek Drayson ,&nbsp;Sally Pehrsson ,&nbsp;Alfredo Camacho ,&nbsp;Kyle Larson ,&nbsp;Robert G. Berman ,&nbsp;Jamie Cutts","doi":"10.1016/j.precamres.2025.107679","DOIUrl":"10.1016/j.precamres.2025.107679","url":null,"abstract":"<div><div>Extensive debate has focussed on the nature and location of the Snowbird Tectonic Zone (STZ), the suture between the Rae and Hearne cratons. Geological mapping in the Baker Lake area revealed a ∼7 km wide deformation zone associated with the Chesterfield Fault Zone (CFZ), a south-dipping, dextral strike-slip structure previously interpreted to represent the northern segment of the STZ. New geochronology across the CFZ indicates both the footwall and hangingwall are dominated by <em>ca.</em> 2.72 Ga tonalite gneisses and <em>ca.</em> 2.6 Ga porphyritic monzogranite, effectively ruling out the CFZ as the northern segment of the STZ. Geochronology, thermobarometry, and thermodynamic modelling from the hangingwall indicate three Paleoproterozoic metamorphic events (M1-M3) that outline a clockwise P-T-t path. Prograde metamorphism (M1) reaching peak conditions of 0.75 GPa and 700 °C is dated by early titanite growth at <em>ca.</em> 1.92 Ga, consistent with burial during southeast-verging folding and thrusting associated with collision of the Rae-Chesterfield and Hearne cratons. Peak conditions of ∼1.0 GPa and 740 °C at <em>ca.</em> 1.87 Ga (M2; garnet Lu-Hf) are coeval with northwest-vergent folding and thrusting during early, intra-oceanic accretionary episodes associated with the Trans-Hudson Orogeny. Dextral strike-slip kinematics argue against the CFZ as the structure responsible for exhumation of <em>ca.</em> 1.9 Ga high-pressure rocks to the south. Instead, exhumation may have been accommodated along discrete, reverse-sense shear zones associated with the CFZ, or an alternate structure to the south. Together, these data highlight that crustal-scale shear zones can preserve tectonometamorphic information, critical for tectonic reconstructions and understanding orogenic processes, that is not recorded in the surrounding lithotectonic blocks.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"418 ","pages":"Article 107679"},"PeriodicalIF":3.2,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The influence of mafic and felsic crust on the seawater chemistry ca. 3.0 billion years ago: Evidence from Nd isotopes in banded iron formations from the Murchison Greenstone Belt","authors":"J. Krayer ,&nbsp;J. Jodder ,&nbsp;A. Hofmann ,&nbsp;S. Weyer ,&nbsp;M. Willbold ,&nbsp;T. Schulz ,&nbsp;C. Koeberl ,&nbsp;S. Viehmann","doi":"10.1016/j.precamres.2025.107701","DOIUrl":"10.1016/j.precamres.2025.107701","url":null,"abstract":"<div><div>Banded iron formations (BIFs) are marine chemical sedimentary rocks that serve as prime archives for Precambrian paleo-environmental reconstructions. However, due to the scarcity of well-preserved Archean rocks, the aquatic environments of early Earth remain poorly constrained. In particular, fluxes derived from continents and submarine hydrothermal systems that affected Archean seawater chemistry are crucial for the understanding of the evolution of marine environments.</div><div>To fill this gap, we present major- and trace element data in combination with Sm-Nd isotopes of individual BIF layers from the ca. 3.0 Ga old Murchison Greenstone Belt (MGB) of South Africa. BIF layers with low immobile element concentrations show seawater-like shale-normalized (subscript SN) rare earth and yttrium (REY_SN) patterns with heavy over light REY_SN enrichment and positive La_SN, Eu_SN, Gd_SN, and Y_SN anomalies, implying an anoxic marine depositional setting with contributions from high-temperature, hydrothermal systems. These BIF samples yield a Sm-Nd age of 2993 ± 97 Ma that overlaps with the proposed depositional age suggesting negligible post-depositional alteration. In contrast, BIF layers with non-seawater-like REY_SN patterns yield a Sm-Nd age of 2504 ± 161 Ma, which can be linked to post-depositional alteration during the ca. 2.7 Ga Limpopo orogeny. The range of initial εNd values from −1.74 to + 0.15 in pristine BIF samples suggests that elements of mixed juvenile and evolved material from emerged continents and/or hydrothermal systems affected Murchison seawater and indicates potential oceanic water mixing in the Murchison region with water masses derived from the northern Pietersburg and the southern Kaapvaal regions.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"418 ","pages":"Article 107701"},"PeriodicalIF":3.2,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry","authors":"K.G. Nymoen ,&nbsp;D.R. Mole ,&nbsp;P.C. Thurston ,&nbsp;D.K. Tinkham ,&nbsp;J.H. Marsh ,&nbsp;R.A. Stern","doi":"10.1016/j.precamres.2025.107705","DOIUrl":"10.1016/j.precamres.2025.107705","url":null,"abstract":"<div><div>The tectono-magmatic processes driving the evolution of Archean continental crust in the early-Earth are highly debated topics. To contribute to a better understanding of crustal evolution in the Meso- to Neoarchean, the Wawa subprovince of the Superior Province, comprising ∼ 2.9–2.6 Ga crustal rocks, represents an ideal location, located along-strike of the well-studied and mineralised Abitibi Subprovince. Here, we integrate whole-rock geochemistry and in-situ zircon U-Pb geochronology, Hf-O isotopes and trace element data from new and compiled magmatic samples across, and proximal to, the Wawa subprovince. Geochronology is used to identify four major volcano-magmatic stages at 2900–2750 Ma (I), 2750–2710 Ma (II), 2710–2680 Ma (III) and 2680–2670 Ma (IV), generally correlating with previous studies from the Michipicoten greenstone belt within the Wawa subprovince. Zircon Hf-isotopic data indicate TTG and felsic volcanic rocks follow two distinct crustal evolution lines from ∼ 3.2 Ga (mafic crust) and ∼ 2.9 Ga (felsic crust). We suggest at least two different sources are responsible for generating crust in the southwestern part of the SE Superior Province in the Archean; the older source is less juvenile and relatively dry, and the younger source is more juvenile and hydrous. Integration of isotopic data with whole-rock Sr/Y, La/Yb_N and Nb, indicates that the depth of magma generation from Source 1 is shallower than that from Source 2, indicating an increase in crustal thickness from Stage I through Stage IV. The comparable Hf-isotopic signatures of the Wawa subprovince, Eastern Wabigoon subprovince and Winnipeg River Terrane samples suggest these areas may have a long-lived, shared crustal evolution.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"418 ","pages":"Article 107705"},"PeriodicalIF":3.2,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}