Pub Date : 2024-10-15DOI: 10.1016/j.gr.2024.10.005
Anju Saxena , Christopher J. Cleal , Kamal Jeet Singh
The Glossopteridales was a distinctive order of gymnospermous seed-plants that occurred widely in the Permian of Gondwana. Some authors have suggested that they may also have occurred in the Triassic and so had survived the catastrophic Permian – Triassic extinction event. This suggestion was mainly based on records from peninsular India such as from the Panchet Formation, which traditionally was regarded as Triassic in age. This paper reviews the evidence for a Triassic age for these floras and it is argued that they are in fact late Permian. There is no clear evidence that the Glossopteridales survived the P/T biotic crisis in India and only unequivocal evidence is in China that they survived into the Triassic.
{"title":"The Permian – Triassic boundary in Peninsular India and the extinction of the Glossopteridales","authors":"Anju Saxena , Christopher J. Cleal , Kamal Jeet Singh","doi":"10.1016/j.gr.2024.10.005","DOIUrl":"10.1016/j.gr.2024.10.005","url":null,"abstract":"<div><div>The Glossopteridales was a distinctive order of gymnospermous seed-plants that occurred widely in the Permian of Gondwana. Some authors have suggested that they may also have occurred in the Triassic and so had survived the catastrophic Permian – Triassic extinction event. This suggestion was mainly based on records from peninsular India such as from the Panchet Formation, which traditionally was regarded as Triassic in age. This paper reviews the evidence for a Triassic age for these floras and it is argued that they are in fact late Permian. There is no clear evidence that the Glossopteridales survived the P/T biotic crisis in India and only unequivocal evidence is in China that they survived into the Triassic.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 318-330"},"PeriodicalIF":7.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1016/j.gr.2024.09.016
Donghwan Kim , Hyunwoo Lee , Mi Jung Lee , Changkun Park , Andrea Luca Rizzo
The Earth’s mantle is considered to be geochemically heterogeneous, which is reflected by the diverse compositions of oceanic island basalts (OIB). The mantle enrichment resulting in this is primarily attributed to the influx of recycled crustal materials into the mantle through subduction. Additionally, the sub-continental lithospheric mantle (SCLM) complicates the elucidation of mantle heterogeneity. From this perspective, Northeast Asia, where the Pacific stagnant slab in the mantle transition zone and the SCLM distribution are presented, is the suitable site for examining the upper mantle scale enrichment. Here we report He-Sr-Nd-Pb-O isotope compositions of Cenozoic basalts found around the Korean Peninsula to illustrate the source lithology and components that caused mantle heterogeneity. Our measured helium isotope ratios ranging from 5.7 to 7.3 Ra (3He/4He ratio of air, Ra = 1.39 x 10-6) are mostly within the SCLM range (6.1 ± 0.9 Ra) but lower than the mid-ocean ridge basalt range (MORB; 8 ± 1 Ra). The Sr-Nd-Pb isotope compositions of the basalts generally display a mixture of depleted MORB mantle (DMM), enriched mantle 1 (EM1), and enriched mantle 2 (EM2) components. In addition, the basalts have δ18Oolivine (vs. V-SMOW) values ranging from 4.7 to 5.7 ‰ that deviate from the DMM range (δ18Oolivine = 5.1 ± 0.2 ‰). Our isotopic analysis results highlight the role of a pyroxenite source in the metasomatized SCLM in the genesis of basalts, and the low 3He/4He ratios of the basalts indicates a significant contribution of SCLM. Moreover, the delaminated cratonic SCLM and asthenosphere-lithosphere interaction are scenarios for the low 3He/4He ratios. Therefore, we propose that mixing of DMM (high 3He/4He ratio; 7 to 9 Ra) and the metasomatized SCLM (low 3He/4He ratio; 5 to 7 Ra) allowed enrichment within the upper mantle scale for the Cenozoic intraplate magmatism in Northeast Asia.
{"title":"Upper mantle scale enrichment of Cenozoic intraplate magmatism in Northeast Asia: He-Sr-Nd-Pb-O isotope geochemistry of the basalts around the Korean peninsula","authors":"Donghwan Kim , Hyunwoo Lee , Mi Jung Lee , Changkun Park , Andrea Luca Rizzo","doi":"10.1016/j.gr.2024.09.016","DOIUrl":"10.1016/j.gr.2024.09.016","url":null,"abstract":"<div><div>The Earth’s mantle is considered to be geochemically heterogeneous, which is reflected by the diverse compositions of oceanic island basalts (OIB). The mantle enrichment resulting in this is primarily attributed to the influx of recycled crustal materials into the mantle through subduction. Additionally, the sub-continental lithospheric mantle (SCLM) complicates the elucidation of mantle heterogeneity. From this perspective, Northeast Asia, where the Pacific stagnant slab in the mantle transition zone and the SCLM distribution are presented, is the suitable site for examining the upper mantle scale enrichment. Here we report He-Sr-Nd-Pb-O isotope compositions of Cenozoic basalts found around the Korean Peninsula to illustrate the source lithology and components that caused mantle heterogeneity. Our measured helium isotope ratios ranging from 5.7 to 7.3 R<sub>a</sub> (<sup>3</sup>He/<sup>4</sup>He ratio of air, R<sub>a</sub> = 1.39 x 10<sup>-6</sup>) are mostly within the SCLM range (6.1 ± 0.9 R<sub>a</sub>) but lower than the mid-ocean ridge basalt range (MORB; 8 ± 1 R<sub>a</sub>). The Sr-Nd-Pb isotope compositions of the basalts generally display a mixture of depleted MORB mantle (DMM), enriched mantle 1 (EM1), and enriched mantle 2 (EM2) components. In addition, the basalts have δ<sup>18</sup>O<sub>olivine</sub> (vs. V-SMOW) values ranging from 4.7 to 5.7 ‰ that deviate from the DMM range (δ<sup>18</sup>O<sub>olivine</sub> = 5.1 ± 0.2 ‰). Our isotopic analysis results highlight the role of a pyroxenite source in the metasomatized SCLM in the genesis of basalts, and the low <sup>3</sup>He/<sup>4</sup>He ratios of the basalts indicates a significant contribution of SCLM. Moreover, the delaminated cratonic SCLM and asthenosphere-lithosphere interaction are scenarios for the low <sup>3</sup>He/<sup>4</sup>He ratios. Therefore, we propose that mixing of DMM (high <sup>3</sup>He/<sup>4</sup>He ratio; 7 to 9 R<sub>a</sub>) and the metasomatized SCLM (low <sup>3</sup>He/<sup>4</sup>He ratio; 5 to 7 R<sub>a</sub>) allowed enrichment within the upper mantle scale for the Cenozoic intraplate magmatism in Northeast Asia.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 349-364"},"PeriodicalIF":7.2,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-09DOI: 10.1016/j.gr.2024.10.002
Diana Moreno-Martín , Rubén Díez Fernández , Richard Albert , Sonia Sánchez Martínez , Esther Rojo-Pérez , Axel Gerdes , Ricardo Arenas
The Cadomian Orogeny formed as an accretionary orogen surrounding Gondwana. The structure resulting from the Cadomian Orogeny is pervasively reworked during the Paleozoic, within the frame of the Variscan Cycle. In SW Iberia (Mina Afortunada Massif), a tectonometamorphic and geochronological analysis revealed two Cadomian deformation phases. The first phase (DC1; 586 Ma, U-Pb dating in inherited metamorphic garnet from Mina Afortunada Gneiss) is associated with ophiolite accretion during the closure of a back-arc or intra-arc basin (Cuartel Ophiolite). A metamorphic fabric related to this phase is preserved as an internal foliation in Ediacaran (meta)sedimentary rocks. The second phase (DC2; 515–485 Ma) is constrained by the age of the igneous protolith of Mina Afortunada Gneiss (∼515 Ma), which is affected by a penetrative foliation formed during DC2, and by the unconformable deposit of Ordovician sediments, which are not affected. The telescoping of metamorphic isograds during DC2 and the geometry of detachment faults associated with this phase suggest extensional tectonics as the driving mechanism for the early exhumation of the Cadomian suture zone in Mina Afortunada Massif. The superimposition of Variscan folds and shear zones onto the Cadomian structures contributed to the subsequent exhumation of the Cadomian suture zone. The analysis and reconstruction of Cadomian and Variscan structures, plus the geochronological data, allow us to correlate the Cuartel Ophiolite with the Mérida Ophiolite, being two pieces of the same, yet dismembered, Cadomian suture zone. The number of Cadomian suture zones in Gondwana does not coincide with that of Cadomian suture zone exposures. Reworked orogens such as the Cadomian could be subjected to duplication of their suture zones. Assessments regarding the Cadomian paleogeography should consider the multiplier effect of the structural overprints after ophiolite accretion.
{"title":"Cuartel Ophiolite: Structure, timing and exhumation mechanisms for a Cadomian suture zone in the peri-Gondwanan Realm (SW Iberia)","authors":"Diana Moreno-Martín , Rubén Díez Fernández , Richard Albert , Sonia Sánchez Martínez , Esther Rojo-Pérez , Axel Gerdes , Ricardo Arenas","doi":"10.1016/j.gr.2024.10.002","DOIUrl":"10.1016/j.gr.2024.10.002","url":null,"abstract":"<div><div>The Cadomian Orogeny formed as an accretionary orogen surrounding Gondwana. The structure resulting from the Cadomian Orogeny is pervasively reworked during the Paleozoic, within the frame of the Variscan Cycle. In SW Iberia (Mina Afortunada Massif), a tectonometamorphic and geochronological analysis revealed two Cadomian deformation phases. The first phase (D<sub>C1</sub>; 586 Ma, U-Pb dating in inherited metamorphic garnet from Mina Afortunada Gneiss) is associated with ophiolite accretion during the closure of a back-arc or intra-arc basin (Cuartel Ophiolite). A metamorphic fabric related to this phase is preserved as an internal foliation in Ediacaran (meta)sedimentary rocks. The second phase (D<sub>C2</sub>; 515–485 Ma) is constrained by the age of the igneous protolith of Mina Afortunada Gneiss (∼515 Ma), which is affected by a penetrative foliation formed during D<sub>C2</sub>, and by the unconformable deposit of Ordovician sediments, which are not affected. The telescoping of metamorphic isograds during D<sub>C2</sub> and the geometry of detachment faults associated with this phase suggest extensional tectonics as the driving mechanism for the early exhumation of the Cadomian suture zone in Mina Afortunada Massif. The superimposition of Variscan folds and shear zones onto the Cadomian structures contributed to the subsequent exhumation of the Cadomian suture zone. The analysis and reconstruction of Cadomian and Variscan structures, plus the geochronological data, allow us to correlate the Cuartel Ophiolite with the Mérida Ophiolite, being two pieces of the same, yet dismembered, Cadomian suture zone. The number of Cadomian suture zones in Gondwana does not coincide with that of Cadomian suture zone exposures. Reworked orogens such as the Cadomian could be subjected to duplication of their suture zones. Assessments regarding the Cadomian paleogeography should consider the multiplier effect of the structural overprints after ophiolite accretion.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 255-273"},"PeriodicalIF":7.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents results of zircon U-Pb-Hf isotope analyses and whole-rock geochemistry applied to magmatic rocks of the Silet terrane in the Western Hoggar, forming a part of the Neoproterozoic arc exposed along the boundary between the LATEA metacraton and the Paleoproterozoic In Ouzzal terrane. According to zircon U-Pb geochronology four distinct pulses of Neoproterozoic granitoids magmatism are recognized in the Silet terrane: Tonian (c. 870–840 Ma), Late Tonian (c. 770 Ma), Latest Tonian (c. 730 Ma) and Late Cryogenian (c. 675 Ma).
Geochemical and Hf isotope data indicate a progressive shift in geotectonic settings. The c. 870–840 Ma Tonian TTG pulses (Tonalite-Trondhjemite-Granodiorite) in the North Silet batholith, with superchondritic εHf values (+5.8 to + 7.2), suggest formation in a subduction zone. The subsequent c. 770 Ma Late Tonian magmatism, characterized by mafic compositions, reflects a back-arc tectonic setting, as evidenced by high Ti/V ratios, low V contents, and εHf values of + 6.12 to + 8.95. The c. 730 Ma Latest Tonian magmatism, with more evolved acidic pulses, indicates hybrid mantle–crustal involvement (εHf + 6.53 to + 8.08). The Late Cryogenian intrusions (c. 675 Ma), featuring the lowest εHf values (+1.84 to + 4.09) and inherited c. 870 Ma zircons, suggest formation from the melting of Tonian TTGs during continental collision.
Integrating U-Pb dating with geochemical data provides a comprehensive view of the Silet terrane’s tectonic evolution, supporting a continental arc origin. Disparities in magmatism ages between the northern (c. 870–675 Ma) and southern (c. 740–640 Ma) segments of the Silet arc correlate with the diachronous collision/subduction of a V-shaped “Silet Ocean”, forming an introverted oceanic system (oceans that have formed by rifted continental blocks that were subsequently re‑joined in approximately the same position) within the broader West Gondwana context. Structural analysis indicates that the regional structures of the Silet arc were shaped in a WNW-ESE collisional transpressive regime during the Pan-African orogeny, offering new insights into the Neoproterozoic Silet arc’s geodynamic evolution and its paleogeographical location in the West Gondwana orogeny.
本研究介绍了对西霍加尔西莱特岩系岩浆岩进行锆石U-Pb-Hf同位素分析和全岩地球化学研究的结果，西莱特岩系是新元古代弧的一部分，沿LATEA metacraton和古元古代In Ouzzal岩系边界暴露。根据锆石U-Pb地质年代学，西莱特地层中新新生代花岗岩岩浆活动有四个不同的阶段：地球化学和 Hf 同位素数据表明，大地构造环境在逐渐发生变化。北锡勒特岩床中约 870-840 Ma 的托尼安 TTG 岩浆（托纳岩-特朗杰米岩-花岗闪长岩）具有超强εHf 值（+5.8 至 +7.2），表明其形成于俯冲带。随后的约 770 Ma 晚托尼安岩岩浆活动以黑云母成分为特征，反映了弧后构造环境，高 Ti/V 比值、低 V 含量以及 +6.12 至 +8.95 的 εHf 值就是证明。约 730 Ma 的最新托尼期岩浆活动，具有更多的酸性脉冲，表明地幔-地壳混合参与（εHf + 6.53 至 + 8.08）。晚冰元古代侵入体（约 675 Ma）的εHf 值最低（+1.84 至 +4.09），并继承了约 870 Ma 的锆石，这表明该侵入体是在大陆碰撞过程中由托尼安 TTGs 熔化形成的。西莱特弧北段（约 870-675 Ma）和南段（约 740-640 Ma）之间岩浆年龄的差异与 V 形 "西莱特洋 "的非同步碰撞/俯冲有关，在更广泛的西冈瓦纳背景下形成了一个内向海洋系统（由裂开的大陆块形成的海洋，随后在大致相同的位置重新接合）。结构分析表明，在泛非造山运动期间，西莱特弧的区域结构是在 WNW-ESE 碰撞转位机制中形成的，这为了解新近纪西莱特弧的地球动力演化及其在西冈瓦纳造山运动中的古地理位置提供了新的视角。
{"title":"Neoproterozoic arc-magmatism of the Silet Terrane, Western Hoggar (Algeria), new constraints from zircon U-Pb-Hf isotope analyses and whole rock geochemistry","authors":"Narimene Berrahmane , El-Hocine Fettous , Abderrahmane Bendaoud , Sid Ali Doukkari , Basem Zoheir , Armin Zeh","doi":"10.1016/j.gr.2024.10.003","DOIUrl":"10.1016/j.gr.2024.10.003","url":null,"abstract":"<div><div>This study presents results of zircon U-Pb-Hf isotope analyses and whole-rock geochemistry applied to magmatic rocks of the Silet terrane in the Western Hoggar, forming a part of the Neoproterozoic arc exposed along the boundary between the LATEA metacraton and the Paleoproterozoic In Ouzzal terrane. According to zircon U-Pb geochronology four distinct pulses of Neoproterozoic granitoids magmatism are recognized in the Silet terrane: Tonian (c. 870–840 Ma), Late Tonian (c. 770 Ma), Latest Tonian (c. 730 Ma) and Late Cryogenian (c. 675 Ma).</div><div>Geochemical and Hf isotope data indicate a progressive shift in geotectonic settings. The c. 870–840 Ma Tonian TTG pulses (Tonalite-Trondhjemite-Granodiorite) in the North Silet batholith, with superchondritic εHf values (+5.8 to + 7.2), suggest formation in a subduction zone. The subsequent c. 770 Ma Late Tonian magmatism, characterized by mafic compositions, reflects a back-arc tectonic setting, as evidenced by high Ti/V ratios, low V contents, and εHf values of + 6.12 to + 8.95. The c. 730 Ma Latest Tonian magmatism, with more evolved acidic pulses, indicates hybrid mantle–crustal involvement (εHf + 6.53 to + 8.08). The Late Cryogenian intrusions (c. 675 Ma), featuring the lowest εHf values (+1.84 to + 4.09) and inherited c. 870 Ma zircons, suggest formation from the melting of Tonian TTGs during continental collision.</div><div>Integrating U-Pb dating with geochemical data provides a comprehensive view of the Silet terrane’s tectonic evolution, supporting a continental arc origin. Disparities in magmatism ages between the northern (c. 870–675 Ma) and southern (c. 740–640 Ma) segments of the Silet arc correlate with the diachronous collision/subduction of a V-shaped “Silet Ocean”, forming an introverted oceanic system (oceans that have formed by rifted continental blocks that were subsequently re‑joined in approximately the same position) within the broader West Gondwana context. Structural analysis indicates that the regional structures of the Silet arc were shaped in a WNW-ESE collisional transpressive regime during the Pan-African orogeny, offering new insights into the Neoproterozoic Silet arc’s geodynamic evolution and its paleogeographical location in the West Gondwana orogeny.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 234-254"},"PeriodicalIF":7.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-05DOI: 10.1016/j.gr.2024.10.001
Lihua Liu , Chuanchuan Lü , Tianyao Hao , Xunhua Zhang , Kwanghee Kim , Hanjoon Kim , Yonggang Guo
The South Yellow Sea and its environs are pivotal for unraveling the complexities of crustal dynamics and continental collision processes. A holistic assessment of deep structural variations from northern China to the Korean Peninsula is essential for a comprehensive and accurate determination of the tectonic affinity of the Korean Peninsula.Thus, we deployed a pioneering active-source seismic profile (Line2016) spanning the South Yellow Sea and the eastern onshore region of the Korean Peninsula, provides crucial insights into the collision dynamics between the Sino-Korean Block and the Yangtze Block. Our innovative approach, incorporating forward modeling, tomography, and finite-difference wavefield modeling, yielded a high-resolution crustal P-wave velocity model, addressing a significant knowledge gap in understanding the geological intricacies between northern China and the Korean Peninsula. The results confirmed and precisely located the West Marginal Fault of the Korean Peninsula, a significant crustal-scale tectonic structure, likely representing the eastern boundary between the Yangtze Block and the Sino-Korean Block. The study advocates for classifying the Korean Peninsula as part of the Sino-Korean Block, presenting evidence for the one-part affinity hypothesis. This collision resulted in the creation of two distinct suture zones—an orogenic belt in the northern part and a significant strike-slip fault zone in the eastern part of the South Yellow Sea. The study emphasizes the pivotal role of block morphology in regulating plate convergence, providing valuable insights for understanding similar phenomena in other collision zones.
南黄海及其周边地区对于揭示复杂的地壳动力学和大陆碰撞过程至关重要。因此，我们部署了一条横跨南黄海和朝鲜半岛东部陆上地区的开创性主动源地震剖面（Line2016），为了解中韩地块和长江地块之间的碰撞动力学提供了重要信息。我们的创新方法结合了前向建模、层析成像和有限差分波场建模，建立了高分辨率的地壳 P 波速度模型，解决了在了解中国北部和朝鲜半岛之间错综复杂的地质情况方面的重大知识空白。研究结果确认并精确定位了朝鲜半岛西缘断层，这是一个重要的地壳尺度构造，很可能代表了长江地块和中韩地块之间的东部边界。该研究主张将朝鲜半岛划为中韩地块的一部分，为 "一元亲缘假说 "提供了证据。这次碰撞产生了两个不同的缝合带--北部的造山带和南黄海东部的重要走向滑动断层带。该研究强调了块体形态在调节板块聚合中的关键作用，为理解其他碰撞带的类似现象提供了宝贵的启示。
{"title":"Crustal variations and tectonic implications across the South Yellow Sea based on active-source wide-angle seismic analyses","authors":"Lihua Liu , Chuanchuan Lü , Tianyao Hao , Xunhua Zhang , Kwanghee Kim , Hanjoon Kim , Yonggang Guo","doi":"10.1016/j.gr.2024.10.001","DOIUrl":"10.1016/j.gr.2024.10.001","url":null,"abstract":"<div><div>The South Yellow Sea and its environs are pivotal for unraveling the complexities of crustal dynamics and continental collision processes. A holistic assessment of deep structural variations from northern China to the Korean Peninsula is essential for a comprehensive and accurate determination of the tectonic affinity of the Korean Peninsula.Thus, we deployed a pioneering active-source seismic profile (Line2016) spanning the South Yellow Sea and the eastern onshore region of the Korean Peninsula, provides crucial insights into the collision dynamics between the Sino-Korean Block and the Yangtze Block. Our innovative approach, incorporating forward modeling, tomography, and finite-difference wavefield modeling, yielded a high-resolution crustal P-wave velocity model, addressing a significant knowledge gap in understanding the geological intricacies between northern China and the Korean Peninsula. The results confirmed and precisely located the West Marginal Fault of the Korean Peninsula, a significant crustal-scale tectonic structure, likely representing the eastern boundary between the Yangtze Block and the Sino-Korean Block. The study advocates for classifying the Korean Peninsula as part of the Sino-Korean Block, presenting evidence for the one-part affinity hypothesis. This collision resulted in the creation of two distinct suture zones—an orogenic belt in the northern part and a significant strike-slip fault zone in the eastern part of the South Yellow Sea. The study emphasizes the pivotal role of block morphology in regulating plate convergence, providing valuable insights for understanding similar phenomena in other collision zones.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 117-130"},"PeriodicalIF":7.2,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142424206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-04DOI: 10.1016/j.gr.2024.09.015
Thomas Bader , Lothar Ratschbacher , Leander Franz , Rolf L. Romer , Lifei Zhang , Christian de Capitani , Joseph Mullis , Marion Tichomirowa , Xiaowei Li
The Qinling–Tongbai–Hong’an–Dabie–Sulu Orogen links two cratons, North China and South China, and records the reorganization and transfer of plates from Rodinia to Gondwana and Eurasia. The formation of North Qinling at the southern North China margin (524–378 Ma) by subduction–accretion processes and the collision between North and South China (270–190 Ma) are pivotal for this reorganization. We outline the geological processes that link both events by combining phase equilibria modeling, conventional thermobarometry, U–Pb (zircon, titanite, garnet–staurolite) and 40Ar/39Ar and Rb–Sr (amphibole, micas) geochronology. The North Qinling experienced transpressional reactivation of shear zones, local fluid percolation, and metamorphism up to the lowest amphibolite facies (≲ 550 °C) until 324 Ma; protracted uplift and erosion with slow cooling (1 °C/Myr) led to its peneplanation prior to 260 Ma. The southerly abutting Wuguan Complex underwent two consecutive metamorphic events: while the older was diverse (600–750 °C, 0.5–1.2 GPa), the younger had a regionally homogeneous peak (590 °C, 0.9 GPa) at c. 324 Ma. Subduction and early exhumation of the South China margin occurred at 299–250 Ma in East Qinling. During the exhumation, medium-grade blueschists (500 °C, 1.0–1.3 GPa) were imbricated with low-grade rocks (300 °C, 0.5–1.0 GPa). Subsequent extensional doming with percolation of a low-salinity, hydrous fluid and south-vergent thrusting brought these rocks to near-surface levels by 200 Ma. New and published data indicate that plate convergence governed geologic processes to the south of North China not only before 378 Ma but protractedly or episodically until 190 Ma. This prolonged history is inconsistent with the amalgamation of North China to Gondwana but substantiates paleogeographic reconstructions with North China as a Paleozoic island continent. Carboniferous–Triassic subduction in the Qinling ultimately led to the welding of North China and South China, completing their transfer from Rodinia to Eurasia.
{"title":"Carboniferous–Triassic subduction in the Qinling orogen","authors":"Thomas Bader , Lothar Ratschbacher , Leander Franz , Rolf L. Romer , Lifei Zhang , Christian de Capitani , Joseph Mullis , Marion Tichomirowa , Xiaowei Li","doi":"10.1016/j.gr.2024.09.015","DOIUrl":"10.1016/j.gr.2024.09.015","url":null,"abstract":"<div><div>The Qinling–Tongbai–Hong’an–Dabie–Sulu Orogen links two cratons, North China and South China, and records the reorganization and transfer of plates from Rodinia to Gondwana and Eurasia. The formation of North Qinling at the southern North China margin (524–378 Ma) by subduction–accretion processes and the collision between North and South China (270–190 Ma) are pivotal for this reorganization. We outline the geological processes that link both events by combining phase equilibria modeling, conventional thermobarometry, U–Pb (zircon, titanite, garnet–staurolite) and <sup>40</sup>Ar/<sup>39</sup>Ar and Rb–Sr (amphibole, micas) geochronology. The North Qinling experienced transpressional reactivation of shear zones, local fluid percolation, and metamorphism up to the lowest amphibolite facies (≲ 550 °C) until 324 Ma; protracted uplift and erosion with slow cooling (1 °C/Myr) led to its peneplanation prior to 260 Ma. The southerly abutting Wuguan Complex underwent two consecutive metamorphic events: while the older was diverse (600–750 °C, 0.5–1.2 GPa), the younger had a regionally homogeneous peak (590 °C, 0.9 GPa) at <em>c.</em> 324 Ma. Subduction and early exhumation of the South China margin occurred at 299–250 Ma in East Qinling. During the exhumation, medium-grade blueschists (500 °C, 1.0–1.3 GPa) were imbricated with low-grade rocks (300 °C, 0.5–1.0 GPa). Subsequent extensional doming with percolation of a low-salinity, hydrous fluid and south-vergent thrusting brought these rocks to near-surface levels by 200 Ma. New and published data indicate that plate convergence governed geologic processes to the south of North China not only before 378 Ma but protractedly or episodically until 190 Ma. This prolonged history is inconsistent with the amalgamation of North China to Gondwana but substantiates paleogeographic reconstructions with North China as a Paleozoic island continent. Carboniferous–Triassic subduction in the Qinling ultimately led to the welding of North China and South China, completing their transfer from Rodinia to Eurasia.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 171-208"},"PeriodicalIF":7.2,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142424297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-03DOI: 10.1016/j.gr.2024.09.010
Jintao Kong , Hongru Yu , Junyi Sun , Huan Zhang , Miaomiao Zhang , Zhi Xia
This study presented a novel, rapid, and accurate method for determining zircon origin via a comprehensive analysis of a dataset containing 27,818 zircon trace element sets. This method integrated back propagation neural networks with the AdaBoost algorithm. The optimal classifier characterized as a linear combination of a two-layer neural network model, comprised 100 base classifiers and 400 hidden neurons. It was rigorously trained over 1000 iterations, which resulted in an unbiased error rate of 8.31%. To facilitate practical application, the classifier was integrated into a macro-enabled Excel spreadsheet.
{"title":"Classifying zircon: A machine-learning approach using zircon geochemistry","authors":"Jintao Kong , Hongru Yu , Junyi Sun , Huan Zhang , Miaomiao Zhang , Zhi Xia","doi":"10.1016/j.gr.2024.09.010","DOIUrl":"10.1016/j.gr.2024.09.010","url":null,"abstract":"<div><div>This study presented a novel, rapid, and accurate method for determining zircon origin via a comprehensive analysis of a dataset containing 27,818 zircon trace element sets. This method integrated back propagation neural networks with the AdaBoost algorithm. The optimal classifier characterized as a linear combination of a two-layer neural network model, comprised 100 base classifiers and 400 hidden neurons. It was rigorously trained over 1000 iterations, which resulted in an unbiased error rate of 8.31%. To facilitate practical application, the classifier was integrated into a macro-enabled Excel spreadsheet.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 227-233"},"PeriodicalIF":7.2,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-02DOI: 10.1016/j.gr.2024.09.011
H.B. Huang , K.Y. Wan , E.Y. He , H. Jiang , J. Guo , X.L. Qiu
<div><div>This study investigates the role of crustal structures and anisotropy in southeastern China regarding intraplate earthquakes within the context of concentrated and perturbed tectonic stresses. The region is characterized by a complex multiphase tectonic history,including the ongoing collision between the Philippine Plate and the South China Sea margin. Utilizing the teleseismic receiver function method, we offer a comprehensive depiction of the crustal structures and layered anisotropy in Guangdong and Fujian, two earthquake-prone areas. Our results reveal that the crustal anisotropy is stratified into two layers, with a slow axis perpendicular to the orogenic belt in the upper-middle crust, whereas the fast axis aligns perpendicularly at lower crust levels. The lateral heterogeneity and anisotropy of the crustal structure emphasize both the boundary delineation and differential movement between continental blocks. The observed increase in density and intensity of intraplate earthquakes across this boundary supports our conclusion regarding a connection between decoupled crustal deformation and seismicity. Specifically, the foliation of metamorphic rocks during the Mesozoic collision generated orogen-parallel fabrics in the upper-middle crust, while ductile shearing resulted in orogen-perpendicular fast directions at lower crust levels. In contrast, mismatch evolution between continental blocks reactivated by present collision provides stress conditions conducive to earthquake occurrence in southeastern China. Our findings provide valuable insights into mechanisms behind intraplate earthquakes as well as tectonic evolution within continental collision zones.</div><div>Plain Language Summary</div><div>The mechanism of intraplate earthquakes is a topic of great interest in the study of continental collision and regional tectonic evolution. The controlling factors behind these earthquakes are highly complex and uncertain. In this study, we aim to investigate the role of crustal structures and anisotropy in southeastern China within the context of intraplate seismic activity. This region, which is currently experiencing a collision between the Philippine Plate and the South China Sea Margin, has a multiphase tectonic history that includes remnants of paleo-Pacific subduction. By utilizing the receiver function method, we provide a detailed picture of crustal structures and layered anisotropy in Guangdong and Fujian, two earthquake-prone regions in southeastern China. Our findings reveal that anisotropy in the crust can be stratified into two layers: an upper-middle crust and a lower crust with a slow axis and a fast axis, both perpendicular to the orogeny, respectively. The lateral heterogeneity and anisotropy of the crustal structure highlight the boundary and differential movement between the continental blocks. The enhanced density and intensity of the intraplate earthquakes across this boundary provide evidence for a connection between
{"title":"Crustal structures and anisotropy in southeastern China: Continental collision and intraplate earthquakes","authors":"H.B. Huang , K.Y. Wan , E.Y. He , H. Jiang , J. Guo , X.L. Qiu","doi":"10.1016/j.gr.2024.09.011","DOIUrl":"10.1016/j.gr.2024.09.011","url":null,"abstract":"<div><div>This study investigates the role of crustal structures and anisotropy in southeastern China regarding intraplate earthquakes within the context of concentrated and perturbed tectonic stresses. The region is characterized by a complex multiphase tectonic history,including the ongoing collision between the Philippine Plate and the South China Sea margin. Utilizing the teleseismic receiver function method, we offer a comprehensive depiction of the crustal structures and layered anisotropy in Guangdong and Fujian, two earthquake-prone areas. Our results reveal that the crustal anisotropy is stratified into two layers, with a slow axis perpendicular to the orogenic belt in the upper-middle crust, whereas the fast axis aligns perpendicularly at lower crust levels. The lateral heterogeneity and anisotropy of the crustal structure emphasize both the boundary delineation and differential movement between continental blocks. The observed increase in density and intensity of intraplate earthquakes across this boundary supports our conclusion regarding a connection between decoupled crustal deformation and seismicity. Specifically, the foliation of metamorphic rocks during the Mesozoic collision generated orogen-parallel fabrics in the upper-middle crust, while ductile shearing resulted in orogen-perpendicular fast directions at lower crust levels. In contrast, mismatch evolution between continental blocks reactivated by present collision provides stress conditions conducive to earthquake occurrence in southeastern China. Our findings provide valuable insights into mechanisms behind intraplate earthquakes as well as tectonic evolution within continental collision zones.</div><div>Plain Language Summary</div><div>The mechanism of intraplate earthquakes is a topic of great interest in the study of continental collision and regional tectonic evolution. The controlling factors behind these earthquakes are highly complex and uncertain. In this study, we aim to investigate the role of crustal structures and anisotropy in southeastern China within the context of intraplate seismic activity. This region, which is currently experiencing a collision between the Philippine Plate and the South China Sea Margin, has a multiphase tectonic history that includes remnants of paleo-Pacific subduction. By utilizing the receiver function method, we provide a detailed picture of crustal structures and layered anisotropy in Guangdong and Fujian, two earthquake-prone regions in southeastern China. Our findings reveal that anisotropy in the crust can be stratified into two layers: an upper-middle crust and a lower crust with a slow axis and a fast axis, both perpendicular to the orogeny, respectively. The lateral heterogeneity and anisotropy of the crustal structure highlight the boundary and differential movement between the continental blocks. The enhanced density and intensity of the intraplate earthquakes across this boundary provide evidence for a connection between ","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 1-12"},"PeriodicalIF":7.2,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142424197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-02DOI: 10.1016/j.gr.2024.09.006
Emő Márton , János Haas , Gábor Imre , Máté Velki , László Fodor
Mesozoic paleomagnetic data from the Transdanubian Range Unit (TRU) of the Pannonian Basin has been revised and updated to enable its paleogeographic evolution within SE Europe to be evaluated. After a 30° declination correction, the TRU data are fully consistent with those for Adria which has an almost identical stratigraphic history. This enabled a revised Apparent Polar Wander Path (APWP) to be constructed for the combined data. Comparing this with the corresponding African and European APWP shows that Adria separated from Europe around 190 Ma, then moved independently southwards between 170–120 Ma (a 30° clockwise rotation changing to counter-clockwise around 155–145 Ma). After 155 Ma, there was a northward movement that brought Adria close to the stable European margin by 115 Ma. This latter may have been with or independently of Africa. After 100 Ma, Africa and Adria moved in coordination until the end of the Cretaceous. This sequence of events correlated well with geologically established tectonic events. These include the major extensional phases in the Alpine Tethys during the southward shift and large clockwise rotation (170–155/145 Ma). This was followed by ophiolite obduction in the Neotethys (West and East Vardar) around 155–145 Ma as a result of the dramatic reversal in the displacement of Adria. Finally, around 115 Ma, the TRU was emplaced over Austroalpine units as a thick nappe associated with the general uplift in the Adriatic realm.
对潘诺尼亚盆地外多瑙河山脉单元（TRU）的中生代古地磁数据进行了修订和更新，以便对其在欧洲东南部的古地理演变进行评估。经过 30° 偏角校正后，TRU 的数据与地层历史几乎完全相同的阿德里亚的数据完全一致。这样，就可以为合并数据构建一个修正的表观极地漫游路径（APWP）。将其与相应的非洲和欧洲 APWP 相比较，可以发现阿德里亚在 190 Ma 左右与欧洲分离，然后在 170-120 Ma 之间独立向南移动（顺时针旋转 30° 在 155-145 Ma 左右变为逆时针旋转）。155Ma之后，阿德里亚发生了北移，到115Ma时接近稳定的欧洲边缘。后者可能与非洲一起或独立于非洲之外。100Ma之后，非洲和阿德里亚协调移动，直到白垩纪末。这一系列事件与地质构造事件密切相关。这些事件包括阿尔卑斯特提斯山在南移和大顺时针旋转（170-155/145 Ma）期间的主要扩展阶段。随后，由于阿德里亚位移的急剧逆转，新特提斯（西瓦尔达尔和东瓦尔达尔）在 155-145 Ma 左右发生了蛇绿岩俯冲。最后，在公元前115年左右，TRU作为与亚得里亚海地区总体隆起相关的厚岩层，隆起于奥陶纪单位之上。
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Pub Date : 2024-10-02DOI: 10.1016/j.gr.2024.09.014
Jack E. Stirling , Anthony I.S. Kemp , Malcolm T. McCulloch , Steven W. Denyszyn
Cordilleran granitic batholiths represent significant episodes of crustal growth and differentiation, and commonly display lateral isotopic and chemical variations. Establishing the tectono-magmatic processes responsible for generating this compositional asymmetry is important for understanding crustal evolutionary processes throughout the Phanerozoic. The Bega Batholith, an example of a ‘Cordilleran style’ granite batholith, is the largest I-type Siluro-Devonian granite complex in the Lachlan Fold Belt (LFB) of southeastern Australia and comprises seven granite supersuites that display systematic lateral isotopic and chemical asymmetry. From west to east towards the present-day continental margin, an increase in the content of Na2O, Sr, Al2O3, and P2O5, with concomitant decreases in CaO, Sc, Rb, and V are observed. In the same direction, whole-rock initial 87Sr/86Sr decreases from 0.7098 to 0.7039, εNd values increase from −8.3 to +4.4, and δ18O decreases from 10.2 ‰ to 7.9 ‰. Depleted-mantle model ages also decrease from ca. 1800 Ma in the west to 600 Ma in the east. Here, we address whether these chemical and isotopic variations were generated by interaction between two distinct components (mantle-derived magmas and supracrustal sources) or were alternatively produced by partial melting of infracrustal source rocks formed sequentially by much earlier episodes of crustal underplating. Combined whole-rock Nd-Sr-O isotopic and geochemical analyses indicate that several I-type supersuites exhibit chemical and isotopic correlations consistent with two-component magma mixing. This new evidence challenges the long-held view that I-type granites derive exclusively from the melting of infracrustal sources, and that granite terranes represent wholesale crustal reworking rather than new crustal growth. Our results show that the compositional zoning within the Bega Batholith is multifaceted. Firstly, the presence of two discrete mantle sources endows chemically and isotopically distinct eastern and western segments in the batholith. Secondly, within these compositionally distinct regions the lateral compositional changes across supersuites derives from mixing between mantle-derived and supracrustal sources. Finally, progressive extension within a developing back-arc environment regulates the ratio of crust-mantle contributions and compositional architecture of each I-type supersuite.
科迪勒拉花岗岩浴成岩代表了地壳生长和分化的重要阶段，通常表现出横向同位素和化学变化。确定产生这种成分不对称的构造-岩浆过程对于了解整个新生代的地壳演化过程非常重要。贝加浴成岩是 "科迪勒拉风格 "花岗岩浴成岩的典范，是澳大利亚东南部拉克兰褶皱带（LFB）中最大的 I 型西鲁-德文花岗岩群，由七个花岗岩超基岩组成，显示出系统的横向同位素和化学不对称。从西向东走向今天的大陆边缘，观察到 Na2O、Sr、Al2O3 和 P2O5 的含量增加，CaO、Sc、Rb 和 V 的含量同时减少。在同一方向上，全岩初始 87Sr/86Sr 值从 0.7098 降至 0.7039，εNd 值从 -8.3 升至 +4.4，δ18O 值从 10.2 ‰ 降至 7.9 ‰。贫幔模型年龄也从西部的约 1800 Ma 下降到东部的 600 Ma。在此，我们探讨了这些化学和同位素变化是由两种不同成分（地幔岩浆和上地壳源）之间的相互作用产生的，还是由更早的地壳下沉事件连续形成的地壳下源岩的部分熔融产生的。综合全岩 Nd-Sr-O 同位素和地球化学分析表明，几个 I 型超岩体显示出与双组分岩浆混合相一致的化学和同位素相关性。这一新证据挑战了长期以来的观点，即 I 型花岗岩完全来自于地壳下源的熔融，花岗岩岩体代表了地壳的整体再加工，而不是新的地壳生长。我们的研究结果表明，贝加浴成岩内部的成分分带是多方面的。首先，由于存在两个不同的地幔源，浴成岩的东西两段在化学和同位素上截然不同。其次，在这些成分截然不同的区域内，不同超岩体之间的横向成分变化源于地幔源与超岩体源之间的混合。最后，在发展中的后弧环境中的逐渐延伸调节了地壳-地幔贡献的比例和每个I型超岩体的成分结构。
{"title":"Chemical and isotopic investigation of the I-type Bega Batholith, southeastern Australia: Implications for batholith compositional zoning and crustal evolution in accretionary orogens","authors":"Jack E. Stirling , Anthony I.S. Kemp , Malcolm T. McCulloch , Steven W. Denyszyn","doi":"10.1016/j.gr.2024.09.014","DOIUrl":"10.1016/j.gr.2024.09.014","url":null,"abstract":"<div><div>Cordilleran granitic batholiths represent significant episodes of crustal growth and differentiation, and commonly display lateral isotopic and chemical variations. Establishing the tectono-magmatic processes responsible for generating this compositional asymmetry is important for understanding crustal evolutionary processes throughout the Phanerozoic. The Bega Batholith, an example of a ‘Cordilleran style’ granite batholith, is the largest I-type Siluro-Devonian granite complex in the Lachlan Fold Belt (LFB) of southeastern Australia and comprises seven granite supersuites that display systematic lateral isotopic and chemical asymmetry. From west to east towards the present-day continental margin, an increase in the content of Na<sub>2</sub>O, Sr, Al<sub>2</sub>O<sub>3</sub>, and P<sub>2</sub>O<sub>5</sub>, with concomitant decreases in CaO, Sc, Rb, and V are observed. In the same direction, whole-rock initial <sup>87</sup>Sr/<sup>86</sup>Sr decreases from 0.7098 to 0.7039, ε<sub>Nd</sub> values increase from −8.3 to +4.4, and δ<sup>18</sup>O decreases from 10.2 ‰ to 7.9 ‰. Depleted-mantle model ages also decrease from ca. 1800 Ma in the west to 600 Ma in the east. Here, we address whether these chemical and isotopic variations were generated by interaction between two distinct components (mantle-derived magmas and supracrustal sources) or were alternatively produced by partial melting of infracrustal source rocks formed sequentially by much earlier episodes of crustal underplating. Combined whole-rock Nd-Sr-O isotopic and geochemical analyses indicate that several I-type supersuites exhibit chemical and isotopic correlations consistent with two-component magma mixing. This new evidence challenges the long-held view that I-type granites derive exclusively from the melting of infracrustal sources, and that granite terranes represent wholesale crustal reworking rather than new crustal growth. Our results show that the compositional zoning within the Bega Batholith is multifaceted. Firstly, the presence of two discrete mantle sources endows chemically and isotopically distinct eastern and western segments in the batholith. Secondly, within these compositionally distinct regions the lateral compositional changes across supersuites derives from mixing between mantle-derived and supracrustal sources. Finally, progressive extension within a developing back-arc environment regulates the ratio of crust-mantle contributions and compositional architecture of each I-type supersuite.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"137 ","pages":"Pages 79-98"},"PeriodicalIF":7.2,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142424202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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