Pub Date : 2024-09-21DOI: 10.1016/j.lithos.2024.107810
Qing Zhou , Heng-Ci Tian , Liyu Shan , Sen Hu , Wei Yang , Maoyong He , Lei Zhang , Yangting Lin , Xianhua Li
{"title":"Corrigendum to “Revisiting the formation of lunar anorthosites via the Rb-Sr isotope systematics” [Lithos, volume 486–487, (2024) 107780]","authors":"Qing Zhou , Heng-Ci Tian , Liyu Shan , Sen Hu , Wei Yang , Maoyong He , Lei Zhang , Yangting Lin , Xianhua Li","doi":"10.1016/j.lithos.2024.107810","DOIUrl":"10.1016/j.lithos.2024.107810","url":null,"abstract":"","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107810"},"PeriodicalIF":2.9,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656726","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}
Pub Date : 2024-09-19DOI: 10.1016/j.lithos.2024.107815
Qianling Zhou , Chenglong Yu , Yang-Yang Wang , Dongbo Tan , Erhao Shan , Dongyong Li , Xiaoxia Wang , Yigan Lu , Fengtai Tong , Yilin Xiao
Subduction of the paleo-Pacific Plate has transported volatiles from the surface to the interior of the Earth and significantly altered the chemical and physical properties of the Cenozoic mantle beneath eastern China. However, the characteristics of volatiles other than H2O in the Cenozoic mantle remain poorly constrained. To describe the spatiotemporal distribution of volatiles, including S, Cl, and H2O, in the Cenozoic mantle beneath eastern China, we performed reheating experiments and determined the composition of olivine-hosted melt inclusions from a large area (5.9 × 105 km2) of basalts. Calculations of the mantle-source compositions indicate that the Cenozoic mantle in North China is enriched in S but deficient in H2O and Cl, relative to that in South China. The distinctive features of volatiles likely arise from the different types of recycled materials in the mantle sources (such as Cl-containing sediments, carbonates, or sulfides in the altered oceanic crust) and their different proportions (from <1.7 % to 7 % of subducted sediments). Both the North China and South China mantles reached high volatile contents at 17.5–11.9 Ma, indicating that the activation of the South China mantle and the destruction of the North China Craton may have occurred simultaneously. These novel findings improve our understanding of mantle evolution beneath eastern China and will help in evaluating the contributions of slab subduction to the spatiotemporal heterogeneity of the lithospheric mantle during the Cenozoic.
{"title":"Spatial and temporal characteristics of volatiles in the Cenozoic mantle beneath eastern China","authors":"Qianling Zhou , Chenglong Yu , Yang-Yang Wang , Dongbo Tan , Erhao Shan , Dongyong Li , Xiaoxia Wang , Yigan Lu , Fengtai Tong , Yilin Xiao","doi":"10.1016/j.lithos.2024.107815","DOIUrl":"10.1016/j.lithos.2024.107815","url":null,"abstract":"<div><div>Subduction of the paleo-Pacific Plate has transported volatiles from the surface to the interior of the Earth and significantly altered the chemical and physical properties of the Cenozoic mantle beneath eastern China. However, the characteristics of volatiles other than H<sub>2</sub>O in the Cenozoic mantle remain poorly constrained. To describe the spatiotemporal distribution of volatiles, including S, Cl, and H<sub>2</sub>O, in the Cenozoic mantle beneath eastern China, we performed reheating experiments and determined the composition of olivine-hosted melt inclusions from a large area (5.9 × 10<sup>5</sup> km<sup>2</sup>) of basalts. Calculations of the mantle-source compositions indicate that the Cenozoic mantle in North China is enriched in S but deficient in H<sub>2</sub>O and Cl, relative to that in South China. The distinctive features of volatiles likely arise from the different types of recycled materials in the mantle sources (such as Cl-containing sediments, carbonates, or sulfides in the altered oceanic crust) and their different proportions (from <1.7 % to 7 % of subducted sediments). Both the North China and South China mantles reached high volatile contents at 17.5–11.9 Ma, indicating that the activation of the South China mantle and the destruction of the North China Craton may have occurred simultaneously. These novel findings improve our understanding of mantle evolution beneath eastern China and will help in evaluating the contributions of slab subduction to the spatiotemporal heterogeneity of the lithospheric mantle during the Cenozoic.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107815"},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312922","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}
Pub Date : 2024-09-19DOI: 10.1016/j.lithos.2024.107811
Rezvaneh Jamali Ashtiani , Axel K. Schmitt , Jamshid Hassanzadeh , Arash Sharifi , Christina Günter
Magma-rich passive margins are characterized by mafic intrusions and lavas, making their density comparable to that of the adjoining oceanic crust. As a result, these margins may sink along with the oceanic crust when subduction begins. This possibility warrants further investigation in the geologic record. A fitting example can be found in the Sanandaj-Sirjan Zone (SaSZ), north of the Neotethyan Zagros suture in Iran, where amphibolite to eclogite-facies metabasites are exposed in the Zayanderud high-pressure metamorphic complex. We present UPb zircon ages, whole rock elemental analyses, and Sr-Nd-Hf isotope data to constrain the ages, chemical and isotopic composition, as well as the tectonic setting of the metabasite protoliths. Ion microprobe UPb zircon geochronology on petrographic thin sections reveals Early–Middle Permian protolith ages for small (≤10 μm in diameter) zircon crystals that have been metamorphically overgrown in the eclogite. The elemental and Sr-Nd-Hf isotopic compositions of eclogites and amphibolites indicate a continental flood basalt affinity. Trace element and isotopic signatures closely resemble those of widespread Permian flood basalts erupted during breakup of Pangea and the opening of the Neotethys Ocean, with well-studied examples from Oman, the Himalayas, and the Asian Large Igneous Provinces in Tarim, Tianshan, and Emeishan. Earlier investigations suggested that the eclogitization occurred in the Early–Middle Jurassic. Our findings support a scenario where a magma-rich passive margin was established during the Permian and subsequently sank into the mantle at the onset of Jurassic subduction along this segment of the Neotethys. This studied example advocates a poorly explored possibility of the deep sinking of magma-rich passive margins at the beginning of subduction.
{"title":"Permian flood basalt protoliths for Jurassic amphibolites and eclogites in SW Iran: Implications for subduction of a magma-rich passive margin","authors":"Rezvaneh Jamali Ashtiani , Axel K. Schmitt , Jamshid Hassanzadeh , Arash Sharifi , Christina Günter","doi":"10.1016/j.lithos.2024.107811","DOIUrl":"10.1016/j.lithos.2024.107811","url":null,"abstract":"<div><div>Magma-rich passive margins are characterized by mafic intrusions and lavas, making their density comparable to that of the adjoining oceanic crust. As a result, these margins may sink along with the oceanic crust when subduction begins. This possibility warrants further investigation in the geologic record. A fitting example can be found in the Sanandaj-Sirjan Zone (SaSZ), north of the Neotethyan Zagros suture in Iran, where amphibolite to eclogite-facies metabasites are exposed in the Zayanderud high-pressure metamorphic complex. We present U<img>Pb zircon ages, whole rock elemental analyses, and Sr-Nd-Hf isotope data to constrain the ages, chemical and isotopic composition, as well as the tectonic setting of the metabasite protoliths. Ion microprobe U<img>Pb zircon geochronology on petrographic thin sections reveals Early–Middle Permian protolith ages for small (≤10 μm in diameter) zircon crystals that have been metamorphically overgrown in the eclogite. The elemental and Sr-Nd-Hf isotopic compositions of eclogites and amphibolites indicate a continental flood basalt affinity. Trace element and isotopic signatures closely resemble those of widespread Permian flood basalts erupted during breakup of Pangea and the opening of the Neotethys Ocean, with well-studied examples from Oman, the Himalayas, and the Asian Large Igneous Provinces in Tarim, Tianshan, and Emeishan. Earlier investigations suggested that the eclogitization occurred in the Early–Middle Jurassic. Our findings support a scenario where a magma-rich passive margin was established during the Permian and subsequently sank into the mantle at the onset of Jurassic subduction along this segment of the Neotethys. This studied example advocates a poorly explored possibility of the deep sinking of magma-rich passive margins at the beginning of subduction.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107811"},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142551924","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}
Pub Date : 2024-09-19DOI: 10.1016/j.lithos.2024.107816
Yu Chen , Yi-Xiang Chen , Fatma Gülmez , Ş. Can Genç , Guo-Chao Sun , Zi-Fu Zhao
The formation of orogenic ultrapotassic magmatism in a subduction setting is still unclear as it requires various co-processing mechanisms. To address this problem, especially to investigate the role of carbonate metasomatism in the mantle source, whole-rock Mg-Sr-Nd isotopic compositions have been measured for ultrapotassic magmatic rocks from the Central Pontides arc, northern Turkey, one of the rare examples of subduction-related ultrapotassic magmatism. These ultrapotassic rocks have relatively low (87Sr/86Sr)i (0.70461–0.70687) and εNd(t) (0.3 to 2.6) values and display much lower δ26Mg values (−0.73 ‰ to −0.19 ‰) than the normal mantle. The petrological and geochemical characteristics of the Pontide Ultrapotassic rocks (PUR) indicate that the low δ26Mg values do not result from surficial weathering, diffusion, or magmatic differentiation, but rather reflect the presence of distinct metasomatizing agent in their mantle source. The low Hf/Hf*, Ti/Ti*, Fe/Mn and Ti/Eu ratios, high Ca/Al and (Na2O + K2O)/TiO2 ratios, and lack of significant correlations between δ26Mg and Fe/Mn or (Gd/Yb)N suggest that the low δ26Mg values cannot be reconciled with the contribution of recycled carbonated eclogites, but are induced by the addition of carbonate-rich sediments to their mantle source. This interpretation is also supported by the significant (La/Yb)N vs. Ti/Eu and Hf/Sm vs. CaO/Al2O3 correlations for the ultrapotassic rocks. Using two end-member mixing calculations of MgSr isotopic compositions, the mantle source of PUR is constrained to contain varying proportions of carbonates, mostly of dolomite composition. The addition of carbonate-rich sediments to the mantle may have occurred at depths of 100–150 km as indicated by the trace element compositions of PUR. In this regard, the enrichment of K and other large ion lithophile elements in the ultrapotassic rocks can be induced by the contribution of silicic sediments. Meanwhile, carbonatitic melts can be formed through the partial melting of carbonate-rich sediments in the subducting oceanic slab, which then reacts with the overlying mantle to form carbonated peridotite that serves as the source of ultrapotassic rocks with low-δ26Mg, low-silica, and high LREEs. This study reports for the first time the Mg isotope data of ultrapotassic rocks formed in a continental arc setting and documents that carbonate-rich sediments play an important role in creating such rocks. Future work is needed to test whether this process is common in both oceanic arc and continental arc settings.
{"title":"Magnesium isotope constraints on the role of recycled carbonate-rich sediments in the formation of ultrapotassic magmatic rocks at a continental arc setting","authors":"Yu Chen , Yi-Xiang Chen , Fatma Gülmez , Ş. Can Genç , Guo-Chao Sun , Zi-Fu Zhao","doi":"10.1016/j.lithos.2024.107816","DOIUrl":"10.1016/j.lithos.2024.107816","url":null,"abstract":"<div><div>The formation of orogenic ultrapotassic magmatism in a subduction setting is still unclear as it requires various co-processing mechanisms. To address this problem, especially to investigate the role of carbonate metasomatism in the mantle source, whole-rock Mg-Sr-Nd isotopic compositions have been measured for ultrapotassic magmatic rocks from the Central Pontides arc, northern Turkey, one of the rare examples of subduction-related ultrapotassic magmatism. These ultrapotassic rocks have relatively low (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> (0.70461–0.70687) and ε<sub>Nd</sub>(t) (0.3 to 2.6) values and display much lower δ<sup>26</sup>Mg values (−0.73 ‰ to −0.19 ‰) than the normal mantle. The petrological and geochemical characteristics of the Pontide Ultrapotassic rocks (PUR) indicate that the low δ<sup>26</sup>Mg values do not result from surficial weathering, diffusion, or magmatic differentiation, but rather reflect the presence of distinct metasomatizing agent in their mantle source. The low Hf/Hf*, Ti/Ti*, Fe/Mn and Ti/Eu ratios, high Ca/Al and (Na<sub>2</sub>O + K<sub>2</sub>O)/TiO<sub>2</sub> ratios, and lack of significant correlations between δ<sup>26</sup>Mg and Fe/Mn or (Gd/Yb)<sub>N</sub> suggest that the low δ<sup>26</sup>Mg values cannot be reconciled with the contribution of recycled carbonated eclogites, but are induced by the addition of carbonate-rich sediments to their mantle source. This interpretation is also supported by the significant (La/Yb)<sub>N</sub> vs. Ti/Eu and Hf/Sm vs. CaO/Al<sub>2</sub>O<sub>3</sub> correlations for the ultrapotassic rocks. Using two end-member mixing calculations of Mg<img>Sr isotopic compositions, the mantle source of PUR is constrained to contain varying proportions of carbonates, mostly of dolomite composition. The addition of carbonate-rich sediments to the mantle may have occurred at depths of 100–150 km as indicated by the trace element compositions of PUR. In this regard, the enrichment of K and other large ion lithophile elements in the ultrapotassic rocks can be induced by the contribution of silicic sediments. Meanwhile, carbonatitic melts can be formed through the partial melting of carbonate-rich sediments in the subducting oceanic slab, which then reacts with the overlying mantle to form carbonated peridotite that serves as the source of ultrapotassic rocks with low-δ<sup>26</sup>Mg, low-silica, and high LREEs. This study reports for the first time the Mg isotope data of ultrapotassic rocks formed in a continental arc setting and documents that carbonate-rich sediments play an important role in creating such rocks. Future work is needed to test whether this process is common in both oceanic arc and continental arc settings.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107816"},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312809","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}
Identifying ultrahigh-temperature (UHT) metamorphism in granulite-facies metamorphic terrains and determining its pressure-temperature-time (P-T-t) paths are crucial steps toward elucidating the anomalously hot geodynamic evolution process. This study presents the inaugural identification of chloritized sapphirine-bearing granulites in the Helanshan Complex, located in the western segment of the Khondalite Belt, North China Craton. Three stages of metamorphic evolution were identified based on petrographic analyses, mineral chemistry, and phase equilibrium modelling: the pre-Tmax stage involves the presence of rutile-stable phase assemblage, wherein rutile is partially substituted by ilmenite; the Tmax stage involves the assemblage of garnet + plagioclase + K-feldspar + sillimanite + spinel ± sapphirine + quartz + ilmenite + melt, as evidenced by microscale (<5 μm) blebs of variably chloritized sapphirine within spinel; and the retrograde cooling stage features the solidus assemblage of garnet + plagioclase + biotite + K-feldspar + sillimanite + cordierite + quartz + ilmenite + melt. Phase equilibrium modelling indicates Tmax conditions of 958–1055 °C and 6.4–7.8 kbar, suggesting UHT conditions accompanied by a high geothermal gradient of approximately 150 °C/kbar. Furthermore, a clockwise P-T trajectory was established, involving pre-Tmax decompression and post-Tmax near-isobaric cooling. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon and monazite U-Pb dating of UHT pelitic granulites produced ages clustering around 1.91 Ga, marking the era of UHT metamorphism within the Helanshan Complex. This discovery broadens the scope of UHT metamorphism and indicates that the entire Khondalite Belt experienced a regional UHT metamorphic event during 1.93–1.91 Ga, which was likely induced by an initial radiogenic heating synergy followed by an augmented mantle heat flux.
{"title":"Paleoproterozoic ultrahigh-temperature metamorphism in the Helanshan Complex, North China Craton: New constraints from chloritized sapphirine-bearing pelitic granulites","authors":"Shangjing Wu , Changqing Yin , Jiahui Qian , Hengzhong Qiao , Xiaoman Wang , Yanfei Xia , Yanling Zhang","doi":"10.1016/j.lithos.2024.107814","DOIUrl":"10.1016/j.lithos.2024.107814","url":null,"abstract":"<div><p>Identifying ultrahigh-temperature (UHT) metamorphism in granulite-facies metamorphic terrains and determining its pressure-temperature-time (P-T-t) paths are crucial steps toward elucidating the anomalously hot geodynamic evolution process. This study presents the inaugural identification of chloritized sapphirine-bearing granulites in the Helanshan Complex, located in the western segment of the Khondalite Belt, North China Craton. Three stages of metamorphic evolution were identified based on petrographic analyses, mineral chemistry, and phase equilibrium modelling: the pre-T<sub>max</sub> stage involves the presence of rutile-stable phase assemblage, wherein rutile is partially substituted by ilmenite; the T<sub>max</sub> stage involves the assemblage of garnet + plagioclase + K-feldspar + sillimanite + spinel ± sapphirine + quartz + ilmenite + melt, as evidenced by microscale (<5 μm) blebs of variably chloritized sapphirine within spinel; and the retrograde cooling stage features the solidus assemblage of garnet + plagioclase + biotite + K-feldspar + sillimanite + cordierite + quartz + ilmenite + melt. Phase equilibrium modelling indicates T<sub>max</sub> conditions of 958–1055 °C and 6.4–7.8 kbar, suggesting UHT conditions accompanied by a high geothermal gradient of approximately 150 °C/kbar. Furthermore, a clockwise P-T trajectory was established, involving pre-T<sub>max</sub> decompression and post-T<sub>max</sub> near-isobaric cooling. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon and monazite U-Pb dating of UHT pelitic granulites produced ages clustering around 1.91 Ga, marking the era of UHT metamorphism within the Helanshan Complex. This discovery broadens the scope of UHT metamorphism and indicates that the entire Khondalite Belt experienced a regional UHT metamorphic event during 1.93–1.91 Ga, which was likely induced by an initial radiogenic heating synergy followed by an augmented mantle heat flux.</p></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107814"},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142274268","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}
The isothermal compression is a special prograde metamorphic P-T path in high-pressure rocks. However, the exact geodynamic processes and associated tectonic significance of this path remain unclear. The Mesozoic subduction and collision between the Sundaland Block and east Java-west Sulawesi (EJWS) generated various metamorphic rock assemblages, thus leading to the crucial need to understand the evolution of the Meso-Tethys. The Bantimala Complex is a key metamorphic basement in Western Sulawesi that preserves records of high-pressure (HP) to ultrahigh-pressure (UHP) metamorphism during Cretaceous subduction. This manuscript presents a detailed petrological, mineralogical, geochronological, phase equilibrium modelling, and Zr-in-rutile thermometry study of a garnet amphibolite from the Bantimala Complex. Petrographic observations indicate that the garnet amphibolite underwent three metamorphic stages that include prograde (M1), peak (M2), and retrograde (M3a and M3b) stages. Pseudosection modelling constrains the P-T conditions of these stages at 13–15.5 kbar/565–585 °C (M1), ∼23.5 kbar/588 °C (M2), 8–9.5 kbar/410–480 °C (M3a), and 8.3–8.8 kbar/415–440 °C (M3b), respectively. UPb dating utilizing magmatic zircon reveals a protolith formation age of 212 ± 3.1 Ma. 40Ar/39Ar dating results from sodic-calcic amphibole and phengite indicate the timing of HP metamorphism at 136–128 Ma (Early Cretaceous). In contrast to other HP metamorphic rocks in the Bantimala Complex (eclogite and blueschist), garnet amphibolite exhibits a unique counterclockwise P-T path that includes an isothermal compression stage. This implies that the rock likely detached from the upper plate and was transported to the lower plate within the subduction zone. Following peak metamorphism at a depth of approximately 75 km, it was exhumed along with other HP metamorphic rocks to a shallower crustal depth of approximately 25 km. Combined with the available data, this study also reveals the coexistence of diverse P-T trajectories within the Bantimala Complex, thus providing robust evidence for a Mesozoic subduction system between the Sundaland Block and Western Sulawesi (Indonesia).
{"title":"Isothermal compression record in the high-pressure Bantimala garnet amphibolite: Implications on the Mesozoic subduction system between the Sundaland and Western Sulawesi (Indonesia)","authors":"Juiyen Hsia , Jian Zhang , Jiahui Qian , Jin Liu , Minjie Guo , Chenying Yu , Welson Weisheng Xian , Changqing Yin , Yuntao Tian","doi":"10.1016/j.lithos.2024.107813","DOIUrl":"10.1016/j.lithos.2024.107813","url":null,"abstract":"<div><div>The isothermal compression is a special prograde metamorphic P-T path in high-pressure rocks. However, the exact geodynamic processes and associated tectonic significance of this path remain unclear. The Mesozoic subduction and collision between the Sundaland Block and east Java-west Sulawesi (EJWS) generated various metamorphic rock assemblages, thus leading to the crucial need to understand the evolution of the Meso-Tethys. The Bantimala Complex is a key metamorphic basement in Western Sulawesi that preserves records of high-pressure (HP) to ultrahigh-pressure (UHP) metamorphism during Cretaceous subduction. This manuscript presents a detailed petrological, mineralogical, geochronological, phase equilibrium modelling, and Zr-in-rutile thermometry study of a garnet amphibolite from the Bantimala Complex. Petrographic observations indicate that the garnet amphibolite underwent three metamorphic stages that include prograde (M<sub>1</sub>), peak (M<sub>2</sub>), and retrograde (M<sub>3a</sub> and M<sub>3b</sub>) stages. Pseudosection modelling constrains the P-T conditions of these stages at 13–15.5 kbar/565–585 °C (M<sub>1</sub>), ∼23.5 kbar/588 °C (M<sub>2</sub>), 8–9.5 kbar/410–480 °C (M<sub>3a</sub>), and 8.3–8.8 kbar/415–440 °C <em>(</em>M<sub>3b</sub>), respectively. U<img>Pb dating utilizing magmatic zircon reveals a protolith formation age of 212 ± 3.1 Ma. <sup>40</sup>Ar/<sup>39</sup>Ar dating results from sodic-calcic amphibole and phengite indicate the timing of HP metamorphism at 136–128 Ma (Early Cretaceous). In contrast to other HP metamorphic rocks in the Bantimala Complex (eclogite and blueschist), garnet amphibolite exhibits a unique counterclockwise P-T path that includes an isothermal compression stage. This implies that the rock likely detached from the upper plate and was transported to the lower plate within the subduction zone. Following peak metamorphism at a depth of approximately 75 km, it was exhumed along with other HP metamorphic rocks to a shallower crustal depth of approximately 25 km. Combined with the available data, this study also reveals the coexistence of diverse P-T trajectories within the Bantimala Complex, thus providing robust evidence for a Mesozoic subduction system between the Sundaland Block and Western Sulawesi (Indonesia).</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107813"},"PeriodicalIF":2.9,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312923","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}
Pub Date : 2024-09-15DOI: 10.1016/j.lithos.2024.107805
Rongsong Tian , Zhangqing Yan , Guoai Xie
The final subduction-closure process of the Paleo-Asian Ocean (PAO) in the middle segments of the southern Central Asian Orogenic Belt (CAOB) is widely debated. Linear arc-related pyroclastic sedimentary rocks and subsequent mafic-alkaline intrusive rocks parallel to the orogenic belt provide valuable constraints on ocean closure. Linearly distributed volcanic samples from the northern margin of the Alxa Block have zircon UPb ages ranging from 272 to 271 Ma, displaying arc geochemical signatures and large ranges of variation (−14.4 to +6.4) of zircon Hf isotopic composition. The Honggueryulin mafic dikes in the Nuoergong–Langshan Belt (NLB) with zircon and apatite UPb dating of 232–231 Ma show a clear geochemical imprint of subduction components with enrichment of light rare earth elements and large-ion lithophile elements (e.g., K, Rb, and Ba) and depletion of high-field-strength elements (e.g., Nb, Ta). The whole-rock major and trace elements and Sr–Nd–Hf isotopic compositions suggest that the Late Triassic mafic dikes mainly originated from a lithospheric mantle that had been metasomatized by subduction-related fluids. Coupled with published data, our geochronological and geochemical data support an east–west-trending Late Triassic alkaline–mafic intrusive rock belt distributed along the northern margin of the Alxa Block–North China Craton, which was formed in a post-orogenic intraplate extensional setting. These pyroclastic sediments and mafic dikes in the NLB document the tectonic transition from the Permian subduction to the Late Triassic post-orogenic extension. Therefore, the final closure of the PAO in the middle segments of the southern CAOB is constrained to between the Early and Middle Triassic.
{"title":"Final subduction-closure process of the Paleo-Asian Ocean in the middle segments of the southern Central Asian Orogenic Belt: Constraints from Permian volcanic rocks and late Triassic mafic dike swarms","authors":"Rongsong Tian , Zhangqing Yan , Guoai Xie","doi":"10.1016/j.lithos.2024.107805","DOIUrl":"10.1016/j.lithos.2024.107805","url":null,"abstract":"<div><p>The final subduction-closure process of the Paleo-Asian Ocean (PAO) in the middle segments of the southern Central Asian Orogenic Belt (CAOB) is widely debated. Linear arc-related pyroclastic sedimentary rocks and subsequent mafic-alkaline intrusive rocks parallel to the orogenic belt provide valuable constraints on ocean closure. Linearly distributed volcanic samples from the northern margin of the Alxa Block have zircon U<img>Pb ages ranging from 272 to 271 Ma, displaying arc geochemical signatures and large ranges of variation (−14.4 to +6.4) of zircon Hf isotopic composition. The Honggueryulin mafic dikes in the Nuoergong–Langshan Belt (NLB) with zircon and apatite U<img>Pb dating of 232–231 Ma show a clear geochemical imprint of subduction components with enrichment of light rare earth elements and large-ion lithophile elements (e.g., K, Rb, and Ba) and depletion of high-field-strength elements (e.g., Nb, Ta). The whole-rock major and trace elements and Sr–Nd–Hf isotopic compositions suggest that the Late Triassic mafic dikes mainly originated from a lithospheric mantle that had been metasomatized by subduction-related fluids. Coupled with published data, our geochronological and geochemical data support an east–west-trending Late Triassic alkaline–mafic intrusive rock belt distributed along the northern margin of the Alxa Block–North China Craton, which was formed in a post-orogenic intraplate extensional setting. These pyroclastic sediments and mafic dikes in the NLB document the tectonic transition from the Permian subduction to the Late Triassic post-orogenic extension. Therefore, the final closure of the PAO in the middle segments of the southern CAOB is constrained to between the Early and Middle Triassic.</p></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107805"},"PeriodicalIF":2.9,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142241390","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}
Pub Date : 2024-09-14DOI: 10.1016/j.lithos.2024.107804
Jiankang Tang , Yonghong Shi , Nanfei Cheng , Genshan Yang , Junjie Li , Guoxing Tang
The Dabie orogenic belt (DOB) has been a classical hot spot for the study of deep continental subduction. However, research on the characteristics of the shallow subduction of the belt is lacking, which limits the full interpretation of the subduction and exhumation processes in the DOB. The Foziling Group, located at the northernmost edge of the DOB, has been considered the best carrier for studying the shallow subduction. Unfortunately, there has been a considerable amount of controversy regarding the metamorphic grade and tectonic affinity of the Foziling Group. For this reason, detailed studies involving geological surveys, petrography, mineral chemistry, geothermobarometry, and detrital zircon geochronology were conducted on the group. The Foziling Group is mainly composed of mica schist, garnet-mica schist, mica-quartz schist, and a small amount of quartzite and marble. Based on the evaluation of the peak metamorphic P-T conditions for 45 samples and previously reported six peak metamorphic P-T values, the Foziling Group can be divided into Zone I and Zone II, whose peak metamorphic conditions are T = 467–519 °C and P = 0.39–0.57 GPa and T = 535–645 °C and P = 0.59–0.96 GPa, respectively. Both P-T estimates fall within the amphibolite facies, and a ∼ 26 °C/km geothermal gradient line was constructed in the field, indicating that the Foziling Group experienced Barrovian metamorphism. Moreover, UPb dating of 465 detrital zircon grains from 5 samples of the group revealed five age peaks at 2.48, 0.94, 0.82, 0.63, and 0.44 Ga and two sub-peaks around ∼2.0–1.85 and ∼ 1.4 Ga. Among them, the youngest six detrital zircon ages range from 412 ± 12 Ma to 389 ± 14 Ma, which indicates that the Foziling Group formed during the Late Devonian. Combining the provenance analysis of detrital zircons, all zircons from the Foziling Group are derived from the DOB, suggesting that the Foziling Group belongs to the Yangtze Block. Compared with the peak metamorphic conditions, the timing of protolith formation, and the ∼ 17 °C/km geothermal gradient line of the Susong Complex at the southern margin of the DOB, both units are interpreted as Late Paleozoic passive continental margin sediments at the northern edge of the Yangtze Block, having both experienced shallow crustal-level subduction during the Indosinian period of the Dabie orogeny. This subduction was of the warm type, terminating near the Moho discontinuity. In contrast, the deep continental subduction of the belt reached the lithospheric mantle and asthenospheric depths, representing a cold subduction type. The transition between these subduction types is speculated to be due to the change in the subduction angle of the tectonic plate.
{"title":"Tectonic affinity and evolution of the Foziling Group: A window into the Dabie orogenic belt's shallow subduction process","authors":"Jiankang Tang , Yonghong Shi , Nanfei Cheng , Genshan Yang , Junjie Li , Guoxing Tang","doi":"10.1016/j.lithos.2024.107804","DOIUrl":"10.1016/j.lithos.2024.107804","url":null,"abstract":"<div><p>The Dabie orogenic belt (DOB) has been a classical hot spot for the study of deep continental subduction. However, research on the characteristics of the shallow subduction of the belt is lacking, which limits the full interpretation of the subduction and exhumation processes in the DOB. The Foziling Group, located at the northernmost edge of the DOB, has been considered the best carrier for studying the shallow subduction. Unfortunately, there has been a considerable amount of controversy regarding the metamorphic grade and tectonic affinity of the Foziling Group. For this reason, detailed studies involving geological surveys, petrography, mineral chemistry, geothermobarometry, and detrital zircon geochronology were conducted on the group. The Foziling Group is mainly composed of mica schist, garnet-mica schist, mica-quartz schist, and a small amount of quartzite and marble. Based on the evaluation of the peak metamorphic <em>P-T</em> conditions for 45 samples and previously reported six peak metamorphic <em>P-T</em> values, the Foziling Group can be divided into Zone I and Zone II, whose peak metamorphic conditions are <em>T</em> = 467–519 °C and <em>P</em> = 0.39–0.57 GPa and <em>T</em> = 535–645 °C and <em>P</em> = 0.59–0.96 GPa, respectively. Both <em>P-T</em> estimates fall within the amphibolite facies, and a ∼ 26 °C/km geothermal gradient line was constructed in the field, indicating that the Foziling Group experienced Barrovian metamorphism. Moreover, U<img>Pb dating of 465 detrital zircon grains from 5 samples of the group revealed five age peaks at 2.48, 0.94, 0.82, 0.63, and 0.44 Ga and two sub-peaks around ∼2.0–1.85 and ∼ 1.4 Ga. Among them, the youngest six detrital zircon ages range from 412 ± 12 Ma to 389 ± 14 Ma, which indicates that the Foziling Group formed during the Late Devonian. Combining the provenance analysis of detrital zircons, all zircons from the Foziling Group are derived from the DOB, suggesting that the Foziling Group belongs to the Yangtze Block. Compared with the peak metamorphic conditions, the timing of protolith formation, and the ∼ 17 °C/km geothermal gradient line of the Susong Complex at the southern margin of the DOB, both units are interpreted as Late Paleozoic passive continental margin sediments at the northern edge of the Yangtze Block, having both experienced shallow crustal-level subduction during the Indosinian period of the Dabie orogeny. This subduction was of the warm type, terminating near the Moho discontinuity. In contrast, the deep continental subduction of the belt reached the lithospheric mantle and asthenospheric depths, representing a cold subduction type. The transition between these subduction types is speculated to be due to the change in the subduction angle of the tectonic plate.</p></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107804"},"PeriodicalIF":2.9,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142241391","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}
Pub Date : 2024-09-14DOI: 10.1016/j.lithos.2024.107807
B. Vikram Raju , Ajay Dev Asokan , Xiao-Ping Xia , Zexian Cui , Arathi G. Panicker , M. Ram Mohan
In the present study, we integrate bulk rock chemistry and in-situ zircon U-Pb-Hf isotopes of high-K Neoarchean granitoids from the northeastern part of the Eastern Dharwar Craton (EDC) to investigate their source, petrogenesis, and plausible tectonic setting. Based on the mineral assemblage, in coherence with their geochemical characteristics, these granitoids are classified as Hornblende-biotite granite (HBG) with Microgranular enclaves (ME), Biotite granite (BTG) and Monzogranite (MG). Field observations and zircon U-Pb ages reveal coeval emplacement of these granitoids between 2.53 and 2.50 Ga. The HBG, including ME, has low silica, metaluminous affinity, and high ferromagnesian element content, consistent with their derivation from a mafic source. Some of the HBG and ME samples are strongly enriched in incompatible elements, similar to the sanukitoids. The geochemical attributes and strongly evolved zircon Hf isotopic compositions (ɛHf(t) = −4.3 to +1.8 and −7.3 to +0.2) of the HBG and ME suggest their derivation from a mantle source metasomatized by subducted sediments. The BTG and MG are compositionally similar, with high silica, low ferromagnesian element content, and moderate peraluminous affinity, suggesting the involvement of felsic crustal sources. The sub-chondritic to chondritic zircon Hf isotopic compositions (ɛHf(t) = −2.7 to +1.4 and −6.9 to +1.9) of these granitoids support the involvement of heterogeneous ancient crustal sources. While all granitoids exhibit similar zircon Hf isotopic compositions, their geochemical attributes suggest distinct sources. The HBG reflects juvenile crustal additions, whereas BTG and MG are products of the crustal reworking. We propose that these granitoids formed during the continent-continent collision between Western and Eastern Dharwar cratons, that took place after the break-off of the eastward subducting slab. The asthenospheric upwelling induced by slab break-off and/or lithospheric delamination of thickened crust led to the genesis of metasomatized mantle derived magma, which drove the crustal reworking. The observed zircon Hf isotopic composition of the EDC granitoids are similar to the present day Phanerozoic Alpine-Himalayan type orogenies supporting subduction followed by continental collision model for the stabilisation of Archean cratons. Evidence for the existence of Paleo- Mesoarchean felsic crust from this part of the EDC warrants further studies to test the three-terrane model for the Dharwar Craton.
{"title":"Zircon U-Pb-Hf isotopes constraints on the petrogenesis of Neoarchean granitic rocks from the Northeastern part of the Eastern Dharwar Craton, Southern India","authors":"B. Vikram Raju , Ajay Dev Asokan , Xiao-Ping Xia , Zexian Cui , Arathi G. Panicker , M. Ram Mohan","doi":"10.1016/j.lithos.2024.107807","DOIUrl":"10.1016/j.lithos.2024.107807","url":null,"abstract":"<div><div>In the present study, we integrate bulk rock chemistry and in-situ zircon U-Pb-Hf isotopes of high-K Neoarchean granitoids from the northeastern part of the Eastern Dharwar Craton (EDC) to investigate their source, petrogenesis, and plausible tectonic setting. Based on the mineral assemblage, in coherence with their geochemical characteristics, these granitoids are classified as Hornblende-biotite granite (HBG) with Microgranular enclaves (ME), Biotite granite (BTG) and Monzogranite (MG). Field observations and zircon U-Pb ages reveal coeval emplacement of these granitoids between 2.53 and 2.50 Ga. The HBG, including ME, has low silica, metaluminous affinity, and high ferromagnesian element content, consistent with their derivation from a mafic source. Some of the HBG and ME samples are strongly enriched in incompatible elements, similar to the sanukitoids. The geochemical attributes and strongly evolved zircon Hf isotopic compositions (ɛHf<sub>(t)</sub> = −4.3 to +1.8 and −7.3 to +0.2) of the HBG and ME suggest their derivation from a mantle source metasomatized by subducted sediments. The BTG and MG are compositionally similar, with high silica, low ferromagnesian element content, and moderate peraluminous affinity, suggesting the involvement of felsic crustal sources. The sub-chondritic to chondritic zircon Hf isotopic compositions (ɛHf<sub>(t)</sub> = −2.7 to +1.4 and −6.9 to +1.9) of these granitoids support the involvement of heterogeneous ancient crustal sources. While all granitoids exhibit similar zircon Hf isotopic compositions, their geochemical attributes suggest distinct sources. The HBG reflects juvenile crustal additions, whereas BTG and MG are products of the crustal reworking. We propose that these granitoids formed during the continent-continent collision between Western and Eastern Dharwar cratons, that took place after the break-off of the eastward subducting slab. The asthenospheric upwelling induced by slab break-off and/or lithospheric delamination of thickened crust led to the genesis of metasomatized mantle derived magma, which drove the crustal reworking. The observed zircon Hf isotopic composition of the EDC granitoids are similar to the present day Phanerozoic Alpine-Himalayan type orogenies supporting subduction followed by continental collision model for the stabilisation of Archean cratons. Evidence for the existence of Paleo- Mesoarchean felsic crust from this part of the EDC warrants further studies to test the three-terrane model for the Dharwar Craton.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107807"},"PeriodicalIF":2.9,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142427793","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}
Pub Date : 2024-09-14DOI: 10.1016/j.lithos.2024.107806
Stéphany Rodrigues Lopes , Leonardo Gonçalves , Cristiane Castro Gonçalves , Hugo Moreira , Syro Lacerda , Pedro Vieira Armond
The early Paleoproterozoic Era has been largely recognized as a period of global magmatic slowdown (∼2.3–2.2 Ga). The Lagoa Dourada Suite, located in the Mineiro Belt – southern São Francisco Craton - Brazil, is a juvenile high‑aluminum 2350 Ma TTG suite and spatially associated with a network of dykes that received little attention in the literature. Based on field features, petrography, whole-rock geochemistry, U-Th-Pb, and Hf isotopes in zircons, we propose that these dykes represent three different magmatic pulses produced via intracrustal melting of oceanic crust. Pulse 1 (<2347 Ma) is syn-plutonic with low-SiO2, high-Mg# and HREE, moderate [La/Yb]N, and low Ba+Sr contents. Pulse 2 (ca. <2330 Ma) shows high-SiO2, low-Mg# and HREE, moderate [La/Yb]N, and high Ba+Sr. Pulse 3 (ca. <2325 Ma) has intermediate-SiO2, low-Mg#, high HREE, moderate to high [La/Yb]N, and high Ba+Sr values. Their Hf compositions are broadly similar to those of the host rock, with positive εHf(t) values and the Hf-TDM model ages ranging from 2.65 to 2.46 Ga, attesting to their juvenile nature. These characteristics, coupled with their homogeneous Hf signature (176Hf/177Hf = 0.281382 to 0.281481), suggest that all these magmatic pulses came from a similar source. However, the whole-rock chemical diversity of the dykes and host rock suggests chemical heterogeneities within this source rock and/or the different magmatic pulses were generated by variable degrees of partial melting of a tholeiitic metabasaltic source throughout approximately 25 Ma. These findings reveal a wide compositional diversity of magmas that gave rise to a network of dykes crosscutting the Lagoa Dourada Suite and, consequently, to the framework of a juvenile continental crust on the southern margin of the São Francisco Craton. Furthermore, these rocks constitute a singular example of juvenile magmatism and contribute to a better understanding of the tectono-magmatic lull and potential petrological processes during this period.
{"title":"Diversity of Siderian magmatic pulses revealed by intracrustal melting of oceanic crust in the Mineiro Belt, southern São Francisco Craton","authors":"Stéphany Rodrigues Lopes , Leonardo Gonçalves , Cristiane Castro Gonçalves , Hugo Moreira , Syro Lacerda , Pedro Vieira Armond","doi":"10.1016/j.lithos.2024.107806","DOIUrl":"10.1016/j.lithos.2024.107806","url":null,"abstract":"<div><div>The early Paleoproterozoic Era has been largely recognized as a period of global magmatic slowdown (∼2.3–2.2 Ga). The Lagoa Dourada Suite, located in the Mineiro Belt – southern São Francisco Craton - Brazil, is a juvenile high‑aluminum 2350 Ma TTG suite and spatially associated with a network of dykes that received little attention in the literature. Based on field features, petrography, whole-rock geochemistry, U-Th-Pb, and Hf isotopes in zircons, we propose that these dykes represent three different magmatic pulses produced via intracrustal melting of oceanic crust. Pulse 1 (<2347 Ma) is <em>syn</em>-plutonic with low-SiO<sub>2</sub>, high-Mg# and HREE, moderate [La/Yb]<sub>N</sub>, and low Ba+Sr contents. Pulse 2 (ca. <2330 Ma) shows high-SiO<sub>2</sub>, low-Mg# and HREE, moderate [La/Yb]<sub>N</sub>, and high Ba+Sr. Pulse 3 (ca. <2325 Ma) has intermediate-SiO<sub>2</sub>, low-Mg#, high HREE, moderate to high [La/Yb]<sub>N</sub>, and high Ba+Sr values. Their Hf compositions are broadly similar to those of the host rock, with positive εHf<sub>(t)</sub> values and the Hf-T<sub>DM</sub> model ages ranging from 2.65 to 2.46 Ga, attesting to their juvenile nature. These characteristics, coupled with their homogeneous Hf signature (<sup>176</sup>Hf/<sup>177</sup>Hf = 0.281382 to 0.281481), suggest that all these magmatic pulses came from a similar source. However, the whole-rock chemical diversity of the dykes and host rock suggests chemical heterogeneities within this source rock and/or the different magmatic pulses were generated by variable degrees of partial melting of a tholeiitic metabasaltic source throughout approximately 25 Ma. These findings reveal a wide compositional diversity of magmas that gave rise to a network of dykes crosscutting the Lagoa Dourada Suite and, consequently, to the framework of a juvenile continental crust on the southern margin of the São Francisco Craton. Furthermore, these rocks constitute a singular example of juvenile magmatism and contribute to a better understanding of the tectono-magmatic lull and potential petrological processes during this period.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107806"},"PeriodicalIF":2.9,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312924","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}
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