Pub Date : 2025-01-01DOI: 10.1016/j.lithos.2024.107881
Maria Rosaria Renna , Federico Farina , Maria Ovtcharova
The Porto complex (western Corsica, France) is a post-Variscan, shallow-level intrusive system where mafic and felsic rocks are closely associated. To assess the timeframe and impact of successive injections of mantle-derived melts on a granite magma reservoir and gain a better understanding on the evolution of the complex, we performed high precision UPb dating combined with trace element and Hf isotope compositions of zircon separated from both mafic intrusives and associated granites.
Zircons from the granites have similar 206Pb/238U ages and initial Hf isotopic compositions. The saturation of zircon in the felsic magma occurred before emplacement and mingling with the mafic magma, between 282.55 ± 0.28 Ma and 281.65 ± 0.42 Ma, and at ∼800 °C. The initial ɛHf values of zircons (3.7 ± 2.0 to 5.3 ± 1.0) indicates that the felsic magma source experienced addition of crustal material to a mantle component. Interaction with late-hydrothermal fluids, most likely related to an event affecting the Porto complex after its emplacement, was responsible for the modification of LREE, Ti, Fe and Mn compositions in zircons affected by intense metamictization.
Zircons from the mafic rocks have slightly enriched initial ɛHf values (5.7 ± 1.6 to 6.9 ± 1.6) relative to depleted mantle composition. UPb zircon dating identified two chronologically distinct mafic melts injections, at 280.93 ± 0.21 Ma and 279.63 ± 0.15 Ma, which are representative of the time of mafic magma emplacement and mingling with the felsic magma.
To explain the long-time interval occurring between the saturation of zircon in the felsic magma and the time the granite emplaced, mingled and crossed its solidus, we propose that during cooling, the zircon-bearing granite magma reservoir was intruded, most likely at the base of the felsic mush, by injections of hotter, mafic magmas that caused at least two successive events of rejuvenation and remobilization, which promoted the shallow intrusion of variably differentiated felsic magmas.
{"title":"Rejuvenation of a granitic magma reservoir by mafic injections: Evidence from zircon UPb geochronology, Hf isotopes and trace element compositions (Porto complex, Western Corsica)","authors":"Maria Rosaria Renna , Federico Farina , Maria Ovtcharova","doi":"10.1016/j.lithos.2024.107881","DOIUrl":"10.1016/j.lithos.2024.107881","url":null,"abstract":"<div><div>The Porto complex (western Corsica, France) is a post-Variscan, shallow-level intrusive system where mafic and felsic rocks are closely associated. To assess the timeframe and impact of successive injections of mantle-derived melts on a granite magma reservoir and gain a better understanding on the evolution of the complex, we performed high precision U<img>Pb dating combined with trace element and Hf isotope compositions of zircon separated from both mafic intrusives and associated granites.</div><div>Zircons from the granites have similar <sup>206</sup>Pb/<sup>238</sup>U ages and initial Hf isotopic compositions. The saturation of zircon in the felsic magma occurred before emplacement and mingling with the mafic magma, between 282.55 ± 0.28 Ma and 281.65 ± 0.42 Ma, and at ∼800 °C. The initial ɛ<sub>Hf</sub> values of zircons (3.7 ± 2.0 to 5.3 ± 1.0) indicates that the felsic magma source experienced addition of crustal material to a mantle component. Interaction with late-hydrothermal fluids, most likely related to an event affecting the Porto complex after its emplacement, was responsible for the modification of LREE, Ti, Fe and Mn compositions in zircons affected by intense metamictization.</div><div>Zircons from the mafic rocks have slightly enriched initial ɛ<sub>Hf</sub> values (5.7 ± 1.6 to 6.9 ± 1.6) relative to depleted mantle composition. U<img>Pb zircon dating identified two chronologically distinct mafic melts injections, at 280.93 ± 0.21 Ma and 279.63 ± 0.15 Ma, which are representative of the time of mafic magma emplacement and mingling with the felsic magma.</div><div>To explain the long-time interval occurring between the saturation of zircon in the felsic magma and the time the granite emplaced, mingled and crossed its solidus, we propose that during cooling, the zircon-bearing granite magma reservoir was intruded, most likely at the base of the felsic mush, by injections of hotter, mafic magmas that caused at least two successive events of rejuvenation and remobilization, which promoted the shallow intrusion of variably differentiated felsic magmas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107881"},"PeriodicalIF":2.9,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138836","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 : 2025-01-01DOI: 10.1016/j.lithos.2024.107846
Baoliang Li , Huan Wang , Liqiang Wang , AaoRiGeLe Zhou , Teng Gao , Chenghao Ren
{"title":"Corrigendum to “Genesis and metallogenic potential of the ca.90 Ma Jiangcisha magmatic rocks in the western Shiquanhe suture zone, Xizang, China” [Lithos 472-473 (2024) 107556]","authors":"Baoliang Li , Huan Wang , Liqiang Wang , AaoRiGeLe Zhou , Teng Gao , Chenghao Ren","doi":"10.1016/j.lithos.2024.107846","DOIUrl":"10.1016/j.lithos.2024.107846","url":null,"abstract":"","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107846"},"PeriodicalIF":2.9,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143128074","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 : 2024-12-22DOI: 10.1016/j.lithos.2024.107929
Jörg Ostendorf , Robert Anczkiewicz , Milan Kohút
This contribution presents bulk-rock geochemical data with Sr-Nd-Hf isotopes and LA-ICP-MS U-Pb zircon geochronology for volcanic rocks from the Slanské Vrchy Mountains (E-Slovakia), a c. 50 km long volcanic chain located at the western flank of the Miocene Transcarpathian Basin System. The studied volcanics are represented by calc-alkaline andesites and dacites. More mafic composition was only found in a basaltic andesite enclave. Robust concordant U-Pb zircon ages for andesites (n = 6) and dacites (n = 3) range from 12.3 Ma to 11.8 Ma, indicating quasi-contemporaneous post-collisional volcanism. The basaltic andesite, andesites, and dacites have overlapping and correlated isotopic compositions (87Sr/86Sr(12Ma) = 0.7071 to 0.7104, εNd(12Ma) = −7.0 to −1.0, and εHf(12 Ma) = −6.2 to +2.8), which reflect mantle-crust interaction. A general lack of clear correlations between fractionation indicator SiO2 and isotope ratios as well as overlapping isotopic compositions of the andesites and dacites preclude simple coupled assimilation fractional crystallization (AFC) processes. Furthermore, the overall paucity of inherited zircons indicates limited assimilation at upper crustal levels. Pyroxene geothermobarometry points to a complex transcrustal volcanic system, which most likely involved processes of mixing, assimilation, storage, and homogenization (MASH) in the lower crust. Initial melt generation in the mantle was probably triggered by mantle upwelling in a generally extensional tectonic regime, but details on the nature of the mantle source remain enigmatic.
{"title":"Timing and petrogenesis of late orogenic calc-alkaline volcanism in the Slovak Transcarpathians: Implications for the evolution of the Carpathian collisional process","authors":"Jörg Ostendorf , Robert Anczkiewicz , Milan Kohút","doi":"10.1016/j.lithos.2024.107929","DOIUrl":"10.1016/j.lithos.2024.107929","url":null,"abstract":"<div><div>This contribution presents bulk-rock geochemical data with Sr-Nd-Hf isotopes and LA-ICP-MS U-Pb zircon geochronology for volcanic rocks from the Slanské Vrchy Mountains (E-Slovakia), a c. 50 km long volcanic chain located at the western flank of the Miocene Transcarpathian Basin System. The studied volcanics are represented by calc-alkaline andesites and dacites. More mafic composition was only found in a basaltic andesite enclave. Robust concordant U-Pb zircon ages for andesites (<em>n</em> = 6) and dacites (<em>n</em> = 3) range from 12.3 Ma to 11.8 Ma, indicating quasi-contemporaneous post-collisional volcanism. The basaltic andesite, andesites, and dacites have overlapping and correlated isotopic compositions (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>(12Ma)</sub> = 0.7071 to 0.7104, εNd<sub>(12Ma)</sub> = −7.0 to −1.0, and εHf<sub>(12 Ma)</sub> = −6.2 to +2.8), which reflect mantle-crust interaction. A general lack of clear correlations between fractionation indicator SiO<sub>2</sub> and isotope ratios as well as overlapping isotopic compositions of the andesites and dacites preclude simple coupled assimilation fractional crystallization (AFC) processes. Furthermore, the overall paucity of inherited zircons indicates limited assimilation at upper crustal levels. Pyroxene geothermobarometry points to a complex transcrustal volcanic system, which most likely involved processes of mixing, assimilation, storage, and homogenization (MASH) in the lower crust. Initial melt generation in the mantle was probably triggered by mantle upwelling in a generally extensional tectonic regime, but details on the nature of the mantle source remain enigmatic.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107929"},"PeriodicalIF":2.9,"publicationDate":"2024-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143321016","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 : 2024-11-26DOI: 10.1016/j.lithos.2024.107876
Lei Yang , Calvin F. Miller , Jia-Min Wang , Xiao-Chi Liu , Fu-Yuan Wu
As the product of a collisional belt, Himalayan leucogranites provide insights into the geodynamic and thermal evolution of tectonically thickened crust. Nevertheless, the petrogenesis of these leucogranites is still a much-debated topic. They are typically interpreted as the primary melt formed by partial melting of the Greater Himalayan Crystalline Complex (GHC). There is, however, another view that they are the products of fractional crystallization of less evolved parent magmas. This study aims to explore these competing petrogenetic models. We collected biotite granite, two-mica granite, tourmaline granite, and garnet granite in the Nyalam region for mineralogical and geochemical studies. The granites occur as small laccoliths, sills, and dikes in the upper GHC and the South Tibet Detachment System (STDS). The plagioclase in biotite granite is oligoclase and andesine (An >20) but is more sodic (An <20) in other rocks. From biotite granite to two-mica granite to tourmaline granite, Mg and Ti in biotite and Zr/Hf in zircon gradually decrease, and AlVI and XFe in biotite and Hf in zircon increase correspondingly. Garnet is typically euhedral and spessartine-rich (spessartine >30 wt%), and it only appears in garnet granite, suggesting an increase of Mn/(Fe + Mg) in the melt. These variations suggest that biotite granite is the least evolved rock, and that two-mica granite, tourmaline granite, and garnet granite are increasingly fractionated. This fractionation trend is supported by trace element compositions. Rb-Sr-Ba trace element modeling suggests that the feldspars (plagioclase and k-feldspar) are the main fractionated minerals. ZrHf modeling indicates that the decrease of Zr/Hf ratio in the melt is related to the fraction of zircon fractionated, which is controlled by the change of temperature and melt composition. Additionally, very high Rb/Sr (>20), low Zr/Hf (<20), and strongly negative Eu anomaly (0.2) in garnet granite strongly suggest that the melt experienced extensive fractionation. Compiled Himalayan leucogranite geochemistry presents a similar pattern to our data and modeling result, suggesting that the variety of Himalayan leucogranites might relate to fractional crystallization. In addition, the composition of leucogranites in the Nyalam is a function of spatial position and age. The leucogranites that were produced during the activity of STDS and developed close to STDS have more evolved compositions, indicating that the development of STDS might have played an essential role in the differentiation of leucogranite in the Himalaya.
{"title":"Identification of fractionation processes in the Himalayan leucogranites-Case study from the Nyalam region","authors":"Lei Yang , Calvin F. Miller , Jia-Min Wang , Xiao-Chi Liu , Fu-Yuan Wu","doi":"10.1016/j.lithos.2024.107876","DOIUrl":"10.1016/j.lithos.2024.107876","url":null,"abstract":"<div><div>As the product of a collisional belt, Himalayan leucogranites provide insights into the geodynamic and thermal evolution of tectonically thickened crust. Nevertheless, the petrogenesis of these leucogranites is still a much-debated topic. They are typically interpreted as the primary melt formed by partial melting of the Greater Himalayan Crystalline Complex (GHC). There is, however, another view that they are the products of fractional crystallization of less evolved parent magmas. This study aims to explore these competing petrogenetic models. We collected biotite granite, two-mica granite, tourmaline granite, and garnet granite in the Nyalam region for mineralogical and geochemical studies. The granites occur as small laccoliths, sills, and dikes in the upper GHC and the South Tibet Detachment System (STDS). The plagioclase in biotite granite is oligoclase and andesine (An >20) but is more sodic (An <20) in other rocks. From biotite granite to two-mica granite to tourmaline granite, Mg and Ti in biotite and Zr/Hf in zircon gradually decrease, and Al<sup>VI</sup> and <em>X</em><sub><em>Fe</em></sub> in biotite and Hf in zircon increase correspondingly. Garnet is typically euhedral and spessartine-rich (spessartine >30 wt%), and it only appears in garnet granite, suggesting an increase of Mn/(Fe + Mg) in the melt. These variations suggest that biotite granite is the least evolved rock, and that two-mica granite, tourmaline granite, and garnet granite are increasingly fractionated. This fractionation trend is supported by trace element compositions. Rb-Sr-Ba trace element modeling suggests that the feldspars (plagioclase and k-feldspar) are the main fractionated minerals. Zr<img>Hf modeling indicates that the decrease of Zr/Hf ratio in the melt is related to the fraction of zircon fractionated, which is controlled by the change of temperature and melt composition. Additionally, very high Rb/Sr (>20), low Zr/Hf (<20), and strongly negative Eu anomaly (0.2) in garnet granite strongly suggest that the melt experienced extensive fractionation. Compiled Himalayan leucogranite geochemistry presents a similar pattern to our data and modeling result, suggesting that the variety of Himalayan leucogranites might relate to fractional crystallization. In addition, the composition of leucogranites in the Nyalam is a function of spatial position and age. The leucogranites that were produced during the activity of STDS and developed close to STDS have more evolved compositions, indicating that the development of STDS might have played an essential role in the differentiation of leucogranite in the Himalaya.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107876"},"PeriodicalIF":2.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746515","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 : 2024-11-26DOI: 10.1016/j.lithos.2024.107875
Yong-Jie Yu , Ren-Xu Chen , Qiong-Xia Xia , Zhi-Hui Mu , Zhuang-Zhuang Yin , Guo-Chao Sun
Mineral behavior during anatectic metamorphism is a direct factor controlling the chemical and isotopic compositions of melts and residues. However, the mechanism that causes disequilibrium melting remains poorly understood. A combined study of petrological, geochronological and geochemical analyses was carried out on a stromatic migmatite outcrop, the Luoerling migmatite in the North Dabie zone. The in-source leucosomes and leucocratic veins are products of in situ partial melting and later magmatic intrusion, respectively. The finding of Neoproterozoic, Late Triassic and Early Cretaceous zircons suggests that the migmatites have Neoproterozoic protoliths, and experienced eclogite-facies metamorphism during collisional orogeny and anatectic metamorphism in the post-collisional stage. The occurrence of peritectic amphibole suggests that anatectic metamorphism mainly occurs through biotite hydration melting. The occurrence of orthopyroxene and clinopyroxene indicates local dehydration melting under granulite-facies conditions. Leucosomes show considerably higher 87Sr/86Sri, but lower εNd(t) and εHf(t) values than the corresponding melanosomes. Such isotopic differences between leucosomes and melanosomes result mainly from the influx of external fluids derived from the surrounding eclogites and gneisses, indicating a coupled dehydration-hydration mechanism in the continental subduction zone. Peritectic and anatectic zircon, monazite, titanite and apatite that formed during anatectic metamorphism exhibit different petrological and geochemical characteristics. Peritectic and anatectic accessory minerals in the leucosomes and leucocratic veins exhibit smaller variations in Nd-Hf isotopes than those in the melanosomes, suggesting that the anatectic melts were homogenized during transport. Differential dissolution and growth of monazite, titanite and apatite affect the Sm-Nd isotopes of residues and melts during anatectic metamorphism. The dissolution of apatite plays a significant role in the hydration melting of metagranite. The continuous dissolution of relict zircon during cooling/transportation of melt results in decreased εHf(t) values in anatectic zircon, whereas the incomplete dissolution of relict zircon results in whole-rock Hf-Nd decoupling. The difference in Nd-Hf isotopes among whole-rock and different genetic minerals can distinguish between dehydration and hydration melting. Therefore, this study highlights that a combination of multiple isotope analyses on whole-rock and accessory minerals may be conducive to understanding not only the mechanism and process of disequilibrium melting but also the nature of anatectic metamorphism in collisional orogens.
{"title":"Accessory minerals fingerprint post-collisional anatectic metamorphism in continental collision zones","authors":"Yong-Jie Yu , Ren-Xu Chen , Qiong-Xia Xia , Zhi-Hui Mu , Zhuang-Zhuang Yin , Guo-Chao Sun","doi":"10.1016/j.lithos.2024.107875","DOIUrl":"10.1016/j.lithos.2024.107875","url":null,"abstract":"<div><div>Mineral behavior during anatectic metamorphism is a direct factor controlling the chemical and isotopic compositions of melts and residues. However, the mechanism that causes disequilibrium melting remains poorly understood. A combined study of petrological, geochronological and geochemical analyses was carried out on a stromatic migmatite outcrop, the Luoerling migmatite in the North Dabie zone. The in-source leucosomes and leucocratic veins are products of in situ partial melting and later magmatic intrusion, respectively. The finding of Neoproterozoic, Late Triassic and Early Cretaceous zircons suggests that the migmatites have Neoproterozoic protoliths, and experienced eclogite-facies metamorphism during collisional orogeny and anatectic metamorphism in the post-collisional stage. The occurrence of peritectic amphibole suggests that anatectic metamorphism mainly occurs through biotite hydration melting. The occurrence of orthopyroxene and clinopyroxene indicates local dehydration melting under granulite-facies conditions. Leucosomes show considerably higher <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub>, but lower ε<sub>Nd</sub>(t) and ε<sub>Hf</sub>(t) values than the corresponding melanosomes. Such isotopic differences between leucosomes and melanosomes result mainly from the influx of external fluids derived from the surrounding eclogites and gneisses, indicating a coupled dehydration-hydration mechanism in the continental subduction zone. Peritectic and anatectic zircon, monazite, titanite and apatite that formed during anatectic metamorphism exhibit different petrological and geochemical characteristics. Peritectic and anatectic accessory minerals in the leucosomes and leucocratic veins exhibit smaller variations in Nd-Hf isotopes than those in the melanosomes, suggesting that the anatectic melts were homogenized during transport. Differential dissolution and growth of monazite, titanite and apatite affect the Sm-Nd isotopes of residues and melts during anatectic metamorphism. The dissolution of apatite plays a significant role in the hydration melting of metagranite. The continuous dissolution of relict zircon during cooling/transportation of melt results in decreased ε<sub>Hf</sub>(t) values in anatectic zircon, whereas the incomplete dissolution of relict zircon results in whole-rock Hf-Nd decoupling. The difference in Nd-Hf isotopes among whole-rock and different genetic minerals can distinguish between dehydration and hydration melting. Therefore, this study highlights that a combination of multiple isotope analyses on whole-rock and accessory minerals may be conducive to understanding not only the mechanism and process of disequilibrium melting but also the nature of anatectic metamorphism in collisional orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107875"},"PeriodicalIF":2.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746513","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 : 2024-11-26DOI: 10.1016/j.lithos.2024.107874
Tom Andersen , Marlina A. Elburg
Scandium (Sc) is a compatible element in mafic silicate minerals, in particular amphibole, garnet and clinopyroxene, and is enriched in ultramafic rocks. Nevertheless, its concentration is also sufficiently high in some evolved granites and granite pegmatites to form minerals with essential Sc. In some granitic occurrences, Sc-bearing minerals occur in miarolitic cavities, indicating the importance of late- to post-magmatic fluids. In contrast, some granite pegmatites have thortveitite (Sc2Si2O7) and other Sc-rich minerals, including Sc-enriched garnet as part of evolved magmatic mineral assemblages. The maximum Sc concentration in garnet in thortveitite-bearing, Mesoproterozoic granite pegmatites of probable anatectic origin in South Norway is ca. 2000 ppm, corresponding to ca. 100 ppm in a coexisting silicate melt. As for any trace element, the behaviour of Sc during crustal anatexis is controlled by the amount of melt formed and the mineralogy of the solid residue. The melting process can be modelled from thermodynamical data on solids and melts for given protolith compositions, temperature and pressure. Simulations in a range of mafic/ultramafic to felsic systems show that mafic protoliths will form Sc-depleted anatectic melts, and correspondingly Sc-enriched solid residues under relevant pressure and temperature conditions (2-10 kbar, 700-800 °C). Limited enrichment in melt relative to protolith is only seen in granodioritic-tonalitic bulk compositions, reaching maximum concentrations of 30–60 ppm. The effect of fluorine during melting and subsequent fractionation is to lower the solidus temperature, depolymerise the silicate melt, and lower partition coefficients for Sc between mafic silicate minerals and felsic melt. Contamination with mafic material has only limited effect, as it will eventually sequester Sc into hybrid mafic silicate mineral assemblages and lead to reduction of the Sc concentration of the remaining melt fraction. Further increase of the Sc concentration requires fractional crystallisation of minerals with low KD, i.e. mainly feldspar minerals and quartz, which may be facilitated by selective, local contamination by quartz and feldspar from granitic country rocks.
{"title":"The behaviour of scandium during crustal anatexis: Implications for the petrogenesis of Sc-enriched granitic magma","authors":"Tom Andersen , Marlina A. Elburg","doi":"10.1016/j.lithos.2024.107874","DOIUrl":"10.1016/j.lithos.2024.107874","url":null,"abstract":"<div><div>Scandium (Sc) is a compatible element in mafic silicate minerals, in particular amphibole, garnet and clinopyroxene, and is enriched in ultramafic rocks. Nevertheless, its concentration is also sufficiently high in some evolved granites and granite pegmatites to form minerals with essential Sc. In some granitic occurrences, Sc-bearing minerals occur in miarolitic cavities, indicating the importance of late- to post-magmatic fluids. In contrast, some granite pegmatites have thortveitite (Sc<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>) and other Sc-rich minerals, including Sc-enriched garnet as part of evolved <em>magmatic</em> mineral assemblages. The maximum Sc concentration in garnet in thortveitite-bearing, Mesoproterozoic granite pegmatites of probable anatectic origin in South Norway is ca. 2000 ppm, corresponding to ca. 100 ppm in a coexisting silicate melt. As for any trace element, the behaviour of Sc during crustal anatexis is controlled by the amount of melt formed and the mineralogy of the solid residue. The melting process can be modelled from thermodynamical data on solids and melts for given protolith compositions, temperature and pressure. Simulations in a range of mafic/ultramafic to felsic systems show that mafic protoliths will form Sc-depleted anatectic melts, and correspondingly Sc-enriched solid residues under relevant pressure and temperature conditions (2-10 kbar, 700-800 °C). Limited enrichment in melt relative to protolith is only seen in granodioritic-tonalitic bulk compositions, reaching maximum concentrations of 30–60 ppm. The effect of fluorine during melting and subsequent fractionation is to lower the solidus temperature, depolymerise the silicate melt, and lower partition coefficients for Sc between mafic silicate minerals and felsic melt. Contamination with mafic material has only limited effect, as it will eventually sequester Sc into hybrid mafic silicate mineral assemblages and lead to reduction of the Sc concentration of the remaining melt fraction. Further increase of the Sc concentration requires fractional crystallisation of minerals with low <em>K</em><sub>D</sub>, i.e. mainly feldspar minerals and quartz, which may be facilitated by selective, local contamination by quartz and feldspar from granitic country rocks.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107874"},"PeriodicalIF":2.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746514","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 : 2024-11-26DOI: 10.1016/j.lithos.2024.107877
Şafak Altunkaynak , Ercan Aldanmaz , Stefan Velev , Margaret Forster , Jin-Hui Yang
The magmatic products exposed across Livingston Island comprise a part of the South Shetland magmatic arc built on an active continental margin. The main magmatic phases of Livingston Island include the Early to Late Cretaceous plutonic and volcanic rock associations, the Eocene plutons, and some sporadically distributed intrusions of Paleocene to Eocene dykes. The intrusions were emplaced into the strongly deformed turbiditic sedimentary rocks of the Miers Bluff Formation. 40Ar39Ar and zircon UPb geochronologic data presented here define four distinct episodes of intrusive activity represented by the emplacement of the Hesperides (125 Ma), the Cerro Mirador (104–97 Ma), the Siddons Point (80 Ma) and the Barnard Point suites (42 Ma), in addition to some dyke intrusions with emplacement ages of 105 to 40 Ma. The intrusions are represented by mafic to intermediate compositions characterized by middle potassic, calc-alkaline affinities, with only a few samples from the Eocene activity exhibiting tholeiitic character. Trace element, Sr-Nd-Pb isotope and zircon Hf isotope variations indicate magma generation in a subduction setting with extensive involvement of continental crust-derived melts for the Early to Late Cretaceous activity. The effects of crustal input on melt chemistry appear to have diminished in time, especially from the Paleocene onwards, leading to magma generation with typical oceanic island arc geochemical signatures. This change in melt chemistry is likely partly related to the roll-back induced overriding plate extension which resulted in a time-integrated increase in the rate of melt movement and a decrease in the residence time in crustal levels. Slab steepening caused by the systematic decrease in plate convergence rate led to an enhanced involvement of isotopically depleted mantle component, producing a heterogeneous source with variable subduction signature.
{"title":"Early Cretaceous to Eocene magmatic evolution of Livingston Island, South Shetland Archipelago: Geochronological and isotope geochemical constraints from intrusive suites","authors":"Şafak Altunkaynak , Ercan Aldanmaz , Stefan Velev , Margaret Forster , Jin-Hui Yang","doi":"10.1016/j.lithos.2024.107877","DOIUrl":"10.1016/j.lithos.2024.107877","url":null,"abstract":"<div><div>The magmatic products exposed across Livingston Island comprise a part of the South Shetland magmatic arc built on an active continental margin. The main magmatic phases of Livingston Island include the Early to Late Cretaceous plutonic and volcanic rock associations, the Eocene plutons, and some sporadically distributed intrusions of Paleocene to Eocene dykes. The intrusions were emplaced into the strongly deformed turbiditic sedimentary rocks of the Miers Bluff Formation. <sup>40</sup>Ar<img><sup>39</sup>Ar and zircon U<img>Pb geochronologic data presented here define four distinct episodes of intrusive activity represented by the emplacement of the Hesperides (125 Ma), the Cerro Mirador (104–97 Ma), the Siddons Point (80 Ma) and the Barnard Point suites (42 Ma), in addition to some dyke intrusions with emplacement ages of 105 to 40 Ma. The intrusions are represented by mafic to intermediate compositions characterized by middle potassic, calc-alkaline affinities, with only a few samples from the Eocene activity exhibiting tholeiitic character. Trace element, Sr-Nd-Pb isotope and zircon Hf isotope variations indicate magma generation in a subduction setting with extensive involvement of continental crust-derived melts for the Early to Late Cretaceous activity. The effects of crustal input on melt chemistry appear to have diminished in time, especially from the Paleocene onwards, leading to magma generation with typical oceanic island arc geochemical signatures. This change in melt chemistry is likely partly related to the roll-back induced overriding plate extension which resulted in a time-integrated increase in the rate of melt movement and a decrease in the residence time in crustal levels. Slab steepening caused by the systematic decrease in plate convergence rate led to an enhanced involvement of isotopically depleted mantle component, producing a heterogeneous source with variable subduction signature.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107877"},"PeriodicalIF":2.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746511","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 : 2024-11-26DOI: 10.1016/j.lithos.2024.107878
Yang Wang , Hongrui Zhang , Zengqian Hou
Large-scale Eocene–Oligocene potassic adakite-like granites predominantly occur between 25° N and 27° N, north of the Ailaoshan suture in western Yunnan, eastern Tibetan Plateau. However, limited interpretations of their spatial characteristics hinder our understanding of the tectonic evolution in this region. Herein, we present new petrographic analyses, zircon UPb ages, whole-rock major and trace element compositions, SrNd isotopic data and zircon Hf isotopic mapping for these granites. Zircon UPb ages indicate that the adakite-like granites were emplaced at approximately 37.1–33.6 Ma. These granites exhibit high-K calc-alkaline compositions, enriched light rare earth elements and significant depletion in heavy rare earth elements, characterised by high Sr contents (667–1795 ppm), Sr/Y ratios (35–158) and La/Yb ratios (13–62), alongside low Y (8.2–23.3 ppm) and Yb (0.71–1.13 ppm) contents. The adakite-like granites possess high initial 87Sr/86Sr ratios (0.70596–0.70687) and low εNd(t) values (−5.73 to −0.65), with two-stage depleted mantle model ages (TDM2) ranging from 1.3 to 0.9 Ga. Their zircon εHf(t) values range from −5.1 to +0.7, with Neoproterozoic TDM2 ages of 1.4–1.1 Ga. Notably, these adakite-like rocks in western Yunnan exhibit an eastward decrease in zircon εHf(t) and whole-rock εNd(t) values. By integrating these findings with the Hf isotopic mapping results, we suggest spatial heterogeneity in lower crustal composition in western Yunnan. The lower crust in the western Yangtze block comprises Neoproterozoic arc roots, while the lower crust of the Simao block represents a superposition of Neoproterozoic and Permian–Triassic arc roots. Based on the abrupt changes in angle and depth of the eastward-subducting Indian slab, along with the spatial characteristics of the Eocene–Oligocene magmatism, we propose that east–west-trending tearing of the subducted Indian slab occurs along approximately 26° N beneath the eastern Tibetan Plateau.
{"title":"East–west-trending tearing of the Indian slab beneath the eastern Tibetan Plateau: Insights from Eocene–Oligocene potassic adakite-like granites in western Yunnan","authors":"Yang Wang , Hongrui Zhang , Zengqian Hou","doi":"10.1016/j.lithos.2024.107878","DOIUrl":"10.1016/j.lithos.2024.107878","url":null,"abstract":"<div><div>Large-scale Eocene–Oligocene potassic adakite-like granites predominantly occur between 25° N and 27° N, north of the Ailaoshan suture in western Yunnan, eastern Tibetan Plateau. However, limited interpretations of their spatial characteristics hinder our understanding of the tectonic evolution in this region. Herein, we present new petrographic analyses, zircon U<img>Pb ages, whole-rock major and trace element compositions, Sr<img>Nd isotopic data and zircon Hf isotopic mapping for these granites. Zircon U<img>Pb ages indicate that the adakite-like granites were emplaced at approximately 37.1–33.6 Ma. These granites exhibit high-K calc-alkaline compositions, enriched light rare earth elements and significant depletion in heavy rare earth elements, characterised by high Sr contents (667–1795 ppm), Sr/Y ratios (35–158) and La/Yb ratios (13–62), alongside low Y (8.2–23.3 ppm) and Yb (0.71–1.13 ppm) contents. The adakite-like granites possess high initial <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.70596–0.70687) and low ε<sub>Nd</sub>(t) values (−5.73 to −0.65), with two-stage depleted mantle model ages (T<sub>DM</sub><sup>2</sup>) ranging from 1.3 to 0.9 Ga. Their zircon ε<sub>Hf</sub>(t) values range from −5.1 to +0.7, with Neoproterozoic T<sub>DM</sub><sup>2</sup> ages of 1.4–1.1 Ga. Notably, these adakite-like rocks in western Yunnan exhibit an eastward decrease in zircon ε<sub>Hf</sub>(t) and whole-rock ε<sub>Nd</sub>(t) values. By integrating these findings with the Hf isotopic mapping results, we suggest spatial heterogeneity in lower crustal composition in western Yunnan. The lower crust in the western Yangtze block comprises Neoproterozoic arc roots, while the lower crust of the Simao block represents a superposition of Neoproterozoic and Permian–Triassic arc roots. Based on the abrupt changes in angle and depth of the eastward-subducting Indian slab, along with the spatial characteristics of the Eocene–Oligocene magmatism, we propose that east–west-trending tearing of the subducted Indian slab occurs along approximately 26° N beneath the eastern Tibetan Plateau.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107878"},"PeriodicalIF":2.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720897","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 : 2024-11-25DOI: 10.1016/j.lithos.2024.107879
Lining Cheng , Chao Zhang
<div><div>The interaction between boron-rich (B-rich) fluid and metamorphic rocks, along with the induced tourmalinization, has been widely observed in metamorphic and magmatic-hydrothermal processes. This interaction may significantly influence the formation of ore deposits and petrophysical properties of crustal rocks. However, chemical exchange and element transformation during the boron-metasomatism process are still not clear. In this study, we present a detailed textural and geochemical study of tourmalines and other minerals from tourmaline-rich veins and their host rocks in the Lhozhag area, Eastern Himalaya. Two zones with different mineral assemblages were recognized in the tourmaline-rich veins: the Pl-Qtz zone in the core and the Tur-Ms zone in the rim. Petrographic evidence shows that the tourmaline-rich veins were produced by reactions between the host rocks (i.e. biotite schist) and B-rich fluids. Tourmaline grains show compositional zonation, and the core, mantle, and rim have distinctive major and trace elemental, and boron isotopic compositions. The core of tourmaline (Tur-C) is characterized by the highest Mg/(Mg + Fe) ratio and Sc, V, and Cr concentrations, as well as the lowest Ca, Ti, Mn, Li, Be, and Zn concentrations. The mantle of tourmaline (Tur-M) shows a continuous transition from Tur-C in both colour and composition, which might result from the metasomatic system evolving from wall-rock-controlled to fluid-controlled. The high Li, Zn, and Mn concentrations in Tur-M indicate that the involved fluids (first-stage fluid) were likely magmatic in origin. The rim of tourmaline (Tur-R) is texturally and compositionally homogeneous, generally with intermediate Mg/(Mg + Fe) ratios and Ca, Ti, Li, Sc, V, and Zn concentrations, as well as the lowest Sc, Cr, Sn, and Ba concentrations relative to both Tur-C and Tur-M. The sharp compositional contrast between Tur-M and Tur-R at their boundary suggests an injection of external metamorphic fluid (second-stage fluid). Ti-in-quartz thermometry results show that the temperature of fluid-rock interaction decreases from 700 °C for the formation of Tur-C to 500 °C for the formation of Tur-R. Based on fluid-tourmaline trace element partitioning coefficients at the above temperatures and measured tourmaline compositions, we reconstructed the compositions of both the first-stage magmatic and the second-stage metamorphic fluids. The extremely high Li concentrations (up to 1700 ppm) in the first-stage magmatic fluids reflect the enrichment of Li in the Lhozhag leucogranite magma, which is consistent with the occurrence of spodumene-bearing pegmatite in the Lhozhag area. The relatively high Li concentrations in both the second-stage metamorphic fluid (up to 1000 ppm) and biotite (ca. 2000 ppm) from wall rocks suggest that the biotite-rich metapelite could supply abundant Li to fluid during fluid-rock interaction. The boron isotopic composition of tourmaline also shows a systematic change, with th
{"title":"Boron-metasomatism and fluid evolution revealed by the chemical and boron isotopic compositions of tourmalines from the Lhozhag area, Eastern Himalaya","authors":"Lining Cheng , Chao Zhang","doi":"10.1016/j.lithos.2024.107879","DOIUrl":"10.1016/j.lithos.2024.107879","url":null,"abstract":"<div><div>The interaction between boron-rich (B-rich) fluid and metamorphic rocks, along with the induced tourmalinization, has been widely observed in metamorphic and magmatic-hydrothermal processes. This interaction may significantly influence the formation of ore deposits and petrophysical properties of crustal rocks. However, chemical exchange and element transformation during the boron-metasomatism process are still not clear. In this study, we present a detailed textural and geochemical study of tourmalines and other minerals from tourmaline-rich veins and their host rocks in the Lhozhag area, Eastern Himalaya. Two zones with different mineral assemblages were recognized in the tourmaline-rich veins: the Pl-Qtz zone in the core and the Tur-Ms zone in the rim. Petrographic evidence shows that the tourmaline-rich veins were produced by reactions between the host rocks (i.e. biotite schist) and B-rich fluids. Tourmaline grains show compositional zonation, and the core, mantle, and rim have distinctive major and trace elemental, and boron isotopic compositions. The core of tourmaline (Tur-C) is characterized by the highest Mg/(Mg + Fe) ratio and Sc, V, and Cr concentrations, as well as the lowest Ca, Ti, Mn, Li, Be, and Zn concentrations. The mantle of tourmaline (Tur-M) shows a continuous transition from Tur-C in both colour and composition, which might result from the metasomatic system evolving from wall-rock-controlled to fluid-controlled. The high Li, Zn, and Mn concentrations in Tur-M indicate that the involved fluids (first-stage fluid) were likely magmatic in origin. The rim of tourmaline (Tur-R) is texturally and compositionally homogeneous, generally with intermediate Mg/(Mg + Fe) ratios and Ca, Ti, Li, Sc, V, and Zn concentrations, as well as the lowest Sc, Cr, Sn, and Ba concentrations relative to both Tur-C and Tur-M. The sharp compositional contrast between Tur-M and Tur-R at their boundary suggests an injection of external metamorphic fluid (second-stage fluid). Ti-in-quartz thermometry results show that the temperature of fluid-rock interaction decreases from 700 °C for the formation of Tur-C to 500 °C for the formation of Tur-R. Based on fluid-tourmaline trace element partitioning coefficients at the above temperatures and measured tourmaline compositions, we reconstructed the compositions of both the first-stage magmatic and the second-stage metamorphic fluids. The extremely high Li concentrations (up to 1700 ppm) in the first-stage magmatic fluids reflect the enrichment of Li in the Lhozhag leucogranite magma, which is consistent with the occurrence of spodumene-bearing pegmatite in the Lhozhag area. The relatively high Li concentrations in both the second-stage metamorphic fluid (up to 1000 ppm) and biotite (ca. 2000 ppm) from wall rocks suggest that the biotite-rich metapelite could supply abundant Li to fluid during fluid-rock interaction. The boron isotopic composition of tourmaline also shows a systematic change, with th","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107879"},"PeriodicalIF":2.9,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746512","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 : 2024-11-22DOI: 10.1016/j.lithos.2024.107873
Bao-Quan Zhou , Jin-Hui Yang , Jin-Feng Sun , Hao Wang , Yu-Sheng Zhu , Ya-Dong Wu , Qing-Feng Mei , Lei Xu , Jing Ran
Geological and geochemical observations show that magma mixing and fractional crystallization are fundamental processes in the origin of A-type granites, with the dominant process determining their specific genesis. However, it is difficult to evidently distinguish such two processes using whole-rock geochemistry. Apatite has a long crystallization history and can precipitate from the melt during the whole magmatic evolution process, and its geochemical and Sr isotopic data would constrain the magma mixing and crystal fractionation processes. Here we present the integrated geochemical data and Sr isotopic compositions of apatite from mafic microgranular enclaves (MMEs) and their host A-type granites in the early Cretaceous Qianshan pluton to fingerprint apatite geochemical indicators for tracing magma mixing and fractional crystallization. The variable Sr isotopic compositions of apatites in the mafic microgranular enclaves (0.7097 to 0.7211) and the host biotite granite (0.7131 to 0.7171) suggest a magma mixing process, which cannot be revealed by consistent whole-rock Sr isotopic compositions. The trend between Eu/Eu* and rare earth elements + yttrium (REE + Y) contents and Sr contents in apatite among different samples mimics the magma mixing trend observed in whole-rock, suggesting that the broad range of Sr contents and abrupt increases in REE + Y contents can record the mixing process. However, the effect of fractional crystallization on the apatite composition depends on the partition behavior of elements in different minerals. Specifically, the continuous decreases in Eu/Eu* and Sr contents of apatites effectively indicate progressive feldspar crystallization, and the decreases in the (La/Sm)N and (La/Yb)N ratios of apatites suggest the crystallization of feldspar, biotite and apatite, while the increases of these ratios may trace the crystallization of minerals rich in MREE and/or HREE such as hornblende, zircon, and titanite. These observations confirm the sensitivity of apatite Sr isotopes and trace elements content, as well as REE patterns to magma mixing and fractional crystallization, thus providing valuable insights into the complicated magma evolution processes and petrogenesis of A-type granites. Furthermore, the universality of apatite in granitic rocks and the commonality of magmatic mixing and fractional crystallization in granite origin highlight the broader applicability of our study, offering a valuable perspective for understanding the origin of other granitoids.
地质和地球化学观测表明，岩浆混合和分块结晶是 A 型花岗岩成因的基本过程，其中占主导地位的过程决定了其具体成因。然而，利用全岩地球化学很难明显区分这两个过程。磷灰石的结晶历史较长，可在整个岩浆演化过程中从熔体中析出，其地球化学和锶同位素数据可对岩浆混合和晶体分馏过程进行约束。在此，我们介绍了早白垩世千山柱岩中岩浆微晶飞地及其寄主A型花岗岩中磷灰石的综合地球化学数据和Sr同位素组成，为追踪岩浆混合和分晶过程提供了磷灰石地球化学指标。岩浆微晶粒飞地（0.7097-0.7211）和寄主生物花岗岩（0.7131-0.7171）中磷灰石不同的Sr同位素组成表明存在岩浆混合过程，而一致的全岩Sr同位素组成无法揭示这一过程。不同样品中Eu/Eu*和稀土元素+钇（REE+Y）含量与磷灰石中Sr含量之间的变化趋势模拟了在全岩中观察到的岩浆混合趋势，表明Sr含量的宽范围和REE+Y含量的突然增加可以记录混合过程。然而，部分结晶对磷灰石成分的影响取决于元素在不同矿物中的分配行为。具体地说，磷灰石中 Eu/Eu* 和 Sr 含量的持续降低有效地表明了长石的逐步结晶，磷灰石中 (La/Sm)N 和 (La/Yb)N 比率的降低表明了长石、斜长石和磷灰石的结晶，而这些比率的增加可能追溯到角闪石、锆石和榍石等富含 MREE 和/或 HREE 的矿物的结晶。这些观察结果证实了磷灰石Sr同位素和微量元素含量以及REE模式对岩浆混合和分块结晶的敏感性，从而为了解A型花岗岩复杂的岩浆演化过程和岩石成因提供了宝贵的信息。此外，花岗岩石中磷灰石的普遍性以及花岗岩成因中岩浆混合和分块结晶的共性突出了我们研究的广泛适用性，为了解其他花岗岩的成因提供了宝贵的视角。
{"title":"Apatite geochemical indicators for magma mixing and fractional crystallization in the origin of A-type granite","authors":"Bao-Quan Zhou , Jin-Hui Yang , Jin-Feng Sun , Hao Wang , Yu-Sheng Zhu , Ya-Dong Wu , Qing-Feng Mei , Lei Xu , Jing Ran","doi":"10.1016/j.lithos.2024.107873","DOIUrl":"10.1016/j.lithos.2024.107873","url":null,"abstract":"<div><div>Geological and geochemical observations show that magma mixing and fractional crystallization are fundamental processes in the origin of A-type granites, with the dominant process determining their specific genesis. However, it is difficult to evidently distinguish such two processes using whole-rock geochemistry. Apatite has a long crystallization history and can precipitate from the melt during the whole magmatic evolution process, and its geochemical and Sr isotopic data would constrain the magma mixing and crystal fractionation processes. Here we present the integrated geochemical data and Sr isotopic compositions of apatite from mafic microgranular enclaves (MMEs) and their host A-type granites in the early Cretaceous Qianshan pluton to fingerprint apatite geochemical indicators for tracing magma mixing and fractional crystallization. The variable Sr isotopic compositions of apatites in the mafic microgranular enclaves (0.7097 to 0.7211) and the host biotite granite (0.7131 to 0.7171) suggest a magma mixing process, which cannot be revealed by consistent whole-rock Sr isotopic compositions. The trend between Eu/Eu* and rare earth elements + yttrium (REE + Y) contents and Sr contents in apatite among different samples mimics the magma mixing trend observed in whole-rock, suggesting that the broad range of Sr contents and abrupt increases in REE + Y contents can record the mixing process. However, the effect of fractional crystallization on the apatite composition depends on the partition behavior of elements in different minerals. Specifically, the continuous decreases in Eu/Eu* and Sr contents of apatites effectively indicate progressive feldspar crystallization, and the decreases in the (La/Sm)<sub>N</sub> and (La/Yb)<sub>N</sub> ratios of apatites suggest the crystallization of feldspar, biotite and apatite, while the increases of these ratios may trace the crystallization of minerals rich in MREE and/or HREE such as hornblende, zircon, and titanite. These observations confirm the sensitivity of apatite Sr isotopes and trace elements content, as well as REE patterns to magma mixing and fractional crystallization, thus providing valuable insights into the complicated magma evolution processes and petrogenesis of A-type granites. Furthermore, the universality of apatite in granitic rocks and the commonality of magmatic mixing and fractional crystallization in granite origin highlight the broader applicability of our study, offering a valuable perspective for understanding the origin of other granitoids.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"492 ","pages":"Article 107873"},"PeriodicalIF":2.9,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720898","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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