Pub Date : 2024-06-27DOI: 10.1007/s00410-024-02145-w
Laura J. Crisp, Andrew J Berry
{"title":"Correction to: A new model for zircon saturation in silicate melts","authors":"Laura J. Crisp, Andrew J Berry","doi":"10.1007/s00410-024-02145-w","DOIUrl":"https://doi.org/10.1007/s00410-024-02145-w","url":null,"abstract":"","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503543","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 : 2024-06-27DOI: 10.1007/s00410-024-02156-7
Marina Koreshkova, Hilary Downes, Maria Stifeeva, Ekaterina Salnikova, Yulia Plotkina, Ekaterina Akimova, Irena Peytcheva, Dimitrina Dimitrova, Lubomira Macheva, Aleksandr Larionov, Sergey Sergeev
Garnet granulite xenoliths from the Nurbinskaya diatreme in the central part of the Archean Anabar province in Siberia are fragments of the local lower crust that experienced multiple metamorphic events in the Paleoproterozoic and reheating events in the Mesoproterozoic and later. This study addresses the timing of metamorphic transformations, and constrains the cooling rate and the time of stabilization of the lower crust. The observed metamorphic mineral assemblage of garnet, clinopyroxene, plagioclase, amphibole, rutile and ilmenite was formed at ~ 800 °C, 1.1–1.2 GPa under water-undersaturated conditions at ~ 1.88 Ga. However, the mineral assemblage is not well equilibrated and retains evidence of earlier and subsequent metamorphic stages. Late titanite formed in response to hydrous fluid influx according to phase equilibria modeling. U-Pb dating shows two events of titanite formation at 1850 ± 5 Ma and at 1788 ± 2 Ma. After deformation, which led to the porphyroclastic rock textures, the granulites underwent near-isobaric cooling. The cooling rate was higher than ~ 6 °C/Myr, to retain the garnet compositional zoning. Rutile ages are discordant, with 207Pb/206Pb dates ranging from 1.43 to 1.53 Ga. However, rutile may have responded to earlier thermal pulses, and was also reset later, so it does not record the stabilization of the crust. Crustal stabilization after Paleoproterozoic orogenic events may have occurred shortly after titanite formation.
{"title":"Metamorphic history of the Precambrian lower cratonic crust from U-Pb dating of granulite xenoliths (Anabar province, Siberia)","authors":"Marina Koreshkova, Hilary Downes, Maria Stifeeva, Ekaterina Salnikova, Yulia Plotkina, Ekaterina Akimova, Irena Peytcheva, Dimitrina Dimitrova, Lubomira Macheva, Aleksandr Larionov, Sergey Sergeev","doi":"10.1007/s00410-024-02156-7","DOIUrl":"https://doi.org/10.1007/s00410-024-02156-7","url":null,"abstract":"<p>Garnet granulite xenoliths from the Nurbinskaya diatreme in the central part of the Archean Anabar province in Siberia are fragments of the local lower crust that experienced multiple metamorphic events in the Paleoproterozoic and reheating events in the Mesoproterozoic and later. This study addresses the timing of metamorphic transformations, and constrains the cooling rate and the time of stabilization of the lower crust. The observed metamorphic mineral assemblage of garnet, clinopyroxene, plagioclase, amphibole, rutile and ilmenite was formed at ~ 800 °C, 1.1–1.2 GPa under water-undersaturated conditions at ~ 1.88 Ga. However, the mineral assemblage is not well equilibrated and retains evidence of earlier and subsequent metamorphic stages. Late titanite formed in response to hydrous fluid influx according to phase equilibria modeling. U-Pb dating shows two events of titanite formation at 1850 ± 5 Ma and at 1788 ± 2 Ma. After deformation, which led to the porphyroclastic rock textures, the granulites underwent near-isobaric cooling. The cooling rate was higher than ~ 6 °C/Myr, to retain the garnet compositional zoning. Rutile ages are discordant, with <sup>207</sup>Pb/<sup>206</sup>Pb dates ranging from 1.43 to 1.53 Ga. However, rutile may have responded to earlier thermal pulses, and was also reset later, so it does not record the stabilization of the crust. Crustal stabilization after Paleoproterozoic orogenic events may have occurred shortly after titanite formation.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503542","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 : 2024-06-26DOI: 10.1007/s00410-024-02154-9
Ville J. Virtanen, Henri M.A. Höytiä, Giada Iacono-Marziano, Shenghong Yang, Marko Moilanen, Tuomo Törmänen
Paleoproterozoic (2.05 Ga) komatiites are widespread in the Central Lapland Greenstone Belt (CLGB), northern Finland. Close association with sulfur (S)-rich country rocks and spatiotemporal connection with the Cu-Ni(-PGE) deposits of Kevitsa and Sakatti make these komatiites interesting targets for sulfide deposit exploration. We provide whole-rock geochemical data from Sattasvaara komatiites and combine it with literature data to form a geochemical database for the CLGB komatiites. We construct a model for the komatiites from adiabatic melting of the mantle source to fractional crystallization at crustal conditions. Using MELTS, we calculate three parental melts (MgO = 20.6–25.7 wt%) in equilibrium with Fo92, Fo93, and Fo94 olivine for the CLGB komatiites. Based on REEBOX PRO simulations, these parental melts can form from a single mantle source by different pressures and degrees of melting when the potential temperature is 1575–1700 °C. We calculate ranges of S contents for the parental melts based on the different mantle melting conditions and degrees of melting. We use Magma Chamber Simulator to fractionally crystallize the parental melt at crustal conditions. These simulations reproduce the major element oxide, Ni, Cu, and S contents from our komatiite database. Simulated Ni contents in olivine are compatible with literature data from Kevitsa and Sakatti, hence providing a baseline to identify Ni-depleted olivine in CLGB komatiites and related intrusive rocks. We show that fractional crystallization of the komatiitic parental melt can form either Ni-rich or Cu-rich sulfide melt, depending on the initial Ni and S content of the parental melt.
{"title":"From the mantle source to the crustal sink: magmatic differentiation and sulfide saturation of the Paleoproterozoic komatiites of the Central Lapland Greenstone Belt, Finland","authors":"Ville J. Virtanen, Henri M.A. Höytiä, Giada Iacono-Marziano, Shenghong Yang, Marko Moilanen, Tuomo Törmänen","doi":"10.1007/s00410-024-02154-9","DOIUrl":"https://doi.org/10.1007/s00410-024-02154-9","url":null,"abstract":"<p>Paleoproterozoic (2.05 Ga) komatiites are widespread in the Central Lapland Greenstone Belt (CLGB), northern Finland. Close association with sulfur (S)-rich country rocks and spatiotemporal connection with the Cu-Ni(-PGE) deposits of Kevitsa and Sakatti make these komatiites interesting targets for sulfide deposit exploration. We provide whole-rock geochemical data from Sattasvaara komatiites and combine it with literature data to form a geochemical database for the CLGB komatiites. We construct a model for the komatiites from adiabatic melting of the mantle source to fractional crystallization at crustal conditions. Using MELTS, we calculate three parental melts (MgO = 20.6–25.7 wt%) in equilibrium with Fo<sub>92</sub>, Fo<sub>93</sub>, and Fo<sub>94</sub> olivine for the CLGB komatiites. Based on REEBOX PRO simulations, these parental melts can form from a single mantle source by different pressures and degrees of melting when the potential temperature is 1575–1700 °C. We calculate ranges of S contents for the parental melts based on the different mantle melting conditions and degrees of melting. We use Magma Chamber Simulator to fractionally crystallize the parental melt at crustal conditions. These simulations reproduce the major element oxide, Ni, Cu, and S contents from our komatiite database. Simulated Ni contents in olivine are compatible with literature data from Kevitsa and Sakatti, hence providing a baseline to identify Ni-depleted olivine in CLGB komatiites and related intrusive rocks. We show that fractional crystallization of the komatiitic parental melt can form either Ni-rich or Cu-rich sulfide melt, depending on the initial Ni and S content of the parental melt.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503561","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 : 2024-06-24DOI: 10.1007/s00410-024-02155-8
Justine Magson, Frederick Roelofse, Grant Bybee, Robert Bolhar
The Merensky and Bastard reefs of the Bushveld Complex occur within what has been called a transitional macro-unit along the boundary of the Critical and Main zones. The transitional unit is characterised by a geochemical hiatus recording distinct inflections in mineral chemistry and isotopic compositions. Previously these inflections in mineral chemistry and changes in isotopic compositions were attributed mostly to the influx of a magma that was compositionally distinct from the resident magma and that was parental to the Main Zone of the complex. Sr-isotopic variations across this interval have been particularly well-studied, but despite this, little consensus exists regarding the petrogenesis and metallogenesis of this economically important interval. Here we report whole-rock Sr–Nd-isotopic, major- and trace element geochemical and mineral chemical data across the Merensky-Bastard interval as intersected by borehole BH8172 on the farm Hackney in the eastern Bushveld Complex. Variations in whole-rock Cr/MgO values and initial Sr isotopic ratios across the interval are consistent with the results of previous studies that argued for the co-accumulation of minerals from compositionally and isotopically distinct magmas, of Critical and Main Zone lineages, respectively. In our model, a magma of Critical Zone affinity enters the chamber causing erosion along the chamber floor. Orthopyroxene and plagioclase crystallise from the Critical Zone magma to form the Merensky Reef, as suggested by high whole-rock Cr/MgO ratios (> 80) and unradiogenic Sr-isotopic compositions (87Sr/86Sri < 0.7068). A plagioclase-laden magma of Main Zone affinity subsequently intruded the chamber as a basal flow, elevating the resident Critical Zone magma. Plagioclase within the former floated, forming a solid raft onto which the Bastard Reef was deposited, a model that is entirely consistent with density considerations and an upward increase in the An-content of plagioclase as observed in the anorthositic package between the Merensky and Bastard reefs. From a metallogenetic viewpoint, this would imply that the Main Zone could not have been the source of the PGEs within the Merensky Reef.
{"title":"The Merensky-Bastard interval at Hackney, eastern Bushveld Complex: results of a combined Sr–Nd-isotopic investigation","authors":"Justine Magson, Frederick Roelofse, Grant Bybee, Robert Bolhar","doi":"10.1007/s00410-024-02155-8","DOIUrl":"https://doi.org/10.1007/s00410-024-02155-8","url":null,"abstract":"<p>The Merensky and Bastard reefs of the Bushveld Complex occur within what has been called a transitional macro-unit along the boundary of the Critical and Main zones. The transitional unit is characterised by a geochemical hiatus recording distinct inflections in mineral chemistry and isotopic compositions. Previously these inflections in mineral chemistry and changes in isotopic compositions were attributed mostly to the influx of a magma that was compositionally distinct from the resident magma and that was parental to the Main Zone of the complex. Sr-isotopic variations across this interval have been particularly well-studied, but despite this, little consensus exists regarding the petrogenesis and metallogenesis of this economically important interval. Here we report whole-rock Sr–Nd-isotopic, major- and trace element geochemical and mineral chemical data across the Merensky-Bastard interval as intersected by borehole BH8172 on the farm Hackney in the eastern Bushveld Complex. Variations in whole-rock Cr/MgO values and initial Sr isotopic ratios across the interval are consistent with the results of previous studies that argued for the co-accumulation of minerals from compositionally and isotopically distinct magmas, of Critical and Main Zone lineages, respectively. In our model, a magma of Critical Zone affinity enters the chamber causing erosion along the chamber floor. Orthopyroxene and plagioclase crystallise from the Critical Zone magma to form the Merensky Reef, as suggested by high whole-rock Cr/MgO ratios (> 80) and unradiogenic Sr-isotopic compositions (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> < 0.7068). A plagioclase-laden magma of Main Zone affinity subsequently intruded the chamber as a basal flow, elevating the resident Critical Zone magma. Plagioclase within the former floated, forming a solid raft onto which the Bastard Reef was deposited, a model that is entirely consistent with density considerations and an upward increase in the An-content of plagioclase as observed in the anorthositic package between the Merensky and Bastard reefs. From a metallogenetic viewpoint, this would imply that the Main Zone could not have been the source of the PGEs within the Merensky Reef.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503559","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 : 2024-06-21DOI: 10.1007/s00410-024-02132-1
Antonio Acosta-Vigil, Jana Kotková, Renata Čopjaková, Richard Wirth, Jörg Hermann
This study tests experimentally the hypothesis that calculated bulk compositions of multiphase solid inclusions present in minerals of ultrahigh pressure rocks, can be equated to the composition of the former trapped fluids. We investigated samples from the ultrahigh pressure garnet peridotites of the Bohemian Massif, spatially associated with ultrahigh pressure crustal rocks and representing a former subduction interface environment. Inclusions present in garnets, composed of amphibole + Ba-mica kinoshitalite + carbonates (dolomite + magnesite + norsethite), were taken to their entrapment conditions of c. 4.5 GPa and 1075 ºC. They (re)crystallized into a garnet fringe at the boundary between inclusion and host garnet, kinoshitalite ± olivine, carbonatite melt, and a hydrous fluid. Although the latter may have exsolved from the carbonatite melt upon quenching, microstructures suggest it was present at trapped conditions, and mass balance indicates that it corresponds to a Na-K-Cl-F-rich saline aqueous fluid (brine). Experiments demonstrate the stability of kinoshitalite at 4.5 GPa and 1075 ºC, and suggest that Ba-rich mica + carbonatite melt + brine coexisted at near-peak conditions. Barium is compatible in the carbonatite melt and mica with respect to the brine, with a partition coefficient between carbonatite melt and mica of ≈ 2.5–3. The garnet fringe formed from incongruent reaction of the former inclusion assemblage due to reversing the fluid(s)-host garnet reaction that occurred upon natural cooling/decompression. Loss of H2 or H2O from the inclusions due to volume diffusion through garnet and/or decrepitation, during geological timeframes upon decompression/cooling, may have prevented rehomogenization to a single homogeneous fluid. Our study shows that great care is needed in the interpretation of multiphase solid inclusions present in ultrahigh pressure rocks.
{"title":"Experimental constraints on the nature of multiphase solid inclusions and their bearing on mantle wedge metasomatism, Bohemian Massif","authors":"Antonio Acosta-Vigil, Jana Kotková, Renata Čopjaková, Richard Wirth, Jörg Hermann","doi":"10.1007/s00410-024-02132-1","DOIUrl":"https://doi.org/10.1007/s00410-024-02132-1","url":null,"abstract":"<p>This study tests experimentally the hypothesis that calculated bulk compositions of multiphase solid inclusions present in minerals of ultrahigh pressure rocks, can be equated to the composition of the former trapped fluids. We investigated samples from the ultrahigh pressure garnet peridotites of the Bohemian Massif, spatially associated with ultrahigh pressure crustal rocks and representing a former subduction interface environment. Inclusions present in garnets, composed of amphibole + Ba-mica kinoshitalite + carbonates (dolomite + magnesite + norsethite), were taken to their entrapment conditions of c. 4.5 GPa and 1075 ºC. They (re)crystallized into a garnet fringe at the boundary between inclusion and host garnet, kinoshitalite ± olivine, carbonatite melt, and a hydrous fluid. Although the latter may have exsolved from the carbonatite melt upon quenching, microstructures suggest it was present at trapped conditions, and mass balance indicates that it corresponds to a Na-K-Cl-F-rich saline aqueous fluid (brine). Experiments demonstrate the stability of kinoshitalite at 4.5 GPa and 1075 ºC, and suggest that Ba-rich mica + carbonatite melt + brine coexisted at near-peak conditions. Barium is compatible in the carbonatite melt and mica with respect to the brine, with a partition coefficient between carbonatite melt and mica of ≈ 2.5–3. The garnet fringe formed from incongruent reaction of the former inclusion assemblage due to reversing the fluid(s)-host garnet reaction that occurred upon natural cooling/decompression. Loss of H<sub>2</sub> or H<sub>2</sub>O from the inclusions due to volume diffusion through garnet and/or decrepitation, during geological timeframes upon decompression/cooling, may have prevented rehomogenization to a single homogeneous fluid. Our study shows that great care is needed in the interpretation of multiphase solid inclusions present in ultrahigh pressure rocks.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503560","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 : 2024-06-05DOI: 10.1007/s00410-024-02148-7
Olgeir Sigmarsson, Guðrún Larsen, Garance Hervé
The size of deep-seated magma chambers is an important parameter for understanding pre-eruptive signals such as surface deformation. The constantly inflating Hekla volcano in Iceland has had relatively simple eruptive behaviour during the historical period. The eruptions start explosively with production of differentially evolved andesite magma to dacite, related to the length of the foregoing quiescence period, and ends with an emission of a basaltic andesite lava of uniform composition. The basaltic andesite is formed by fractional crystallisation from a deeper-seated basalt source in a steady-state manner. How fast such a differentiation mechanism operates is unknown. Measured Ra–Th radioactive disequilibrium in both the basalt and the basaltic andesite reveal a decrease from a 14% excess of 226Ra over 230Th to only 5% with magma differentiation. The decrease in 226Ra excess to 5% in the basaltic andesite of Hekla is shown to be controlled by plagioclase fractionation alone. Therefore, the magma differentiation time from basalt to intermediate magma beneath Mt. Hekla is significantly shorter than three centuries, the time needed to detect significant 226Ra-decay. Given the steady-state production of basaltic andesite magma and the estimated magma production rate, the volume of the basaltic andesite magma reservoir can be estimated as less than 2 km3.
{"title":"Rapid differentiation of mafic to intermediate magma constrained by Ra–Th disequilibrium and the size of magma chamber beneath Hekla volcano, Iceland","authors":"Olgeir Sigmarsson, Guðrún Larsen, Garance Hervé","doi":"10.1007/s00410-024-02148-7","DOIUrl":"https://doi.org/10.1007/s00410-024-02148-7","url":null,"abstract":"<p>The size of deep-seated magma chambers is an important parameter for understanding pre-eruptive signals such as surface deformation. The constantly inflating Hekla volcano in Iceland has had relatively simple eruptive behaviour during the historical period. The eruptions start explosively with production of differentially evolved andesite magma to dacite, related to the length of the foregoing quiescence period, and ends with an emission of a basaltic andesite lava of uniform composition. The basaltic andesite is formed by fractional crystallisation from a deeper-seated basalt source in a steady-state manner. How fast such a differentiation mechanism operates is unknown. Measured Ra–Th radioactive disequilibrium in both the basalt and the basaltic andesite reveal a decrease from a 14% excess of <sup>226</sup>Ra over <sup>230</sup>Th to only 5% with magma differentiation. The decrease in <sup>226</sup>Ra excess to 5% in the basaltic andesite of Hekla is shown to be controlled by plagioclase fractionation alone. Therefore, the magma differentiation time from basalt to intermediate magma beneath Mt. Hekla is significantly shorter than three centuries, the time needed to detect significant <sup>226</sup>Ra-decay. Given the steady-state production of basaltic andesite magma and the estimated magma production rate, the volume of the basaltic andesite magma reservoir can be estimated as less than 2 km<sup>3</sup>.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141259629","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 : 2024-06-03DOI: 10.1007/s00410-024-02149-6
Omar Bartoli, Bruna B. Carvalho, Federico Farina
Metabasites are important constituents of deep crustal sections and are the favored rock type for studying lower crustal amphibolite to granulite transitions. However, metapelites may develop a larger number of temperature-sensitive mineral assemblages and are particular useful when extreme ultrahigh temperature (UHT) conditions are envisaged. A recent calibration of the Ti-in-amphibole thermometer by Liao et al. (2021) was supposed to make thermometry on metabasites quick and easy to apply. However, their calibration is based on experiments which were not originally designed to investigate in detail the temperature dependence of Ti in amphibole. In addition, a possible effect of aTiO2 and/or pressure on the Ti content of amphibole was not fully taken into account. This resulted in a calibration uncertainty of ± 70 °C (2σ), much higher than that of other single-mineral thermometers. In this study we firstly test the newly calibrated Ti-in-amphibole thermometer across the mid to lower crustal section of the Ivrea–Verbano Zone (IVZ; NW Italy) and compare the performance of different thermometric techniques across the sequence. Ti-in-amphibole thermometry records increasing peak temperatures from amphibolite (600–700 °C), transition (750–800 °C) and granulite (850–950 °C) zones. Titanium content of amphibole may be modified by retrograde fluid influx returning temperatures c. 200–300 °C lower than in non-altered domains. The comparison reveals that Zr-in-rutile thermometer in pelitic granulites seems to be more prone to post-peak resetting than the Ti-in-amphibole thermometry in nearby mafic rocks. This behavior is also confirmed by amphibole analyses from other UHT localities, where the performance of Ti-in-amphibole thermometry is comparable with that of Al-in-orthopyroxene in pelitic granulites. However, Ti-in-amphibole temperatures are underestimated in rutile-bearing samples and this limitation is not solely restricted to rocks containing high H2O contents as previously thought. Derived constraints on the diffusivity of Ti through amphibole demonstrate the robustness of the Ti-in-amphibole thermometer to later thermal disturbances. However, ad-hoc experiments are still necessary to improve the accuracy and precision of calibration and to extend its applicability. This advance will make mafic granulites routine targets for studies devoted to understanding the regional extent of UHT metamorphism.
玄武岩是深地壳剖面的重要组成部分,也是研究下地壳闪长岩向花岗岩转变的首选岩石类型。然而,偏闪长岩可能形成更多对温度敏感的矿物组合,在极端超高温(UHT)条件下尤其有用。Liao 等人(2021 年)最近对闪石中的钛温度计进行了校准,这本应使偏长岩的温度测量快速、简便地得到应用。然而,他们的校准是基于一些实验,而这些实验最初并不是为了详细研究闪石中 Ti 的温度依赖性而设计的。此外,也没有充分考虑到二氧化钛和/或压力对闪石中 Ti 含量可能产生的影响。这导致了 ± 70 °C (2σ) 的校准不确定性,远高于其他单矿物温度计。在这项研究中,我们首先在伊夫雷亚-韦尔巴诺区(IVZ;意大利西北部)的地壳中下部测试了新校准的钛合闪石温度计,并比较了不同测温技术在整个序列中的性能。闪石中的钛测温记录了闪长岩(600-700 °C)、过渡带(750-800 °C)和花岗闪长岩(850-950 °C)区不断升高的峰值温度。闪长岩中的钛含量可能因逆行流体流入而发生变化,返回温度比未发生变化的区域低约 200-300 ℃。比较结果表明,与附近黑云母岩中的闪石钛含量测温法相比,球粒花岗岩中的金红石锆含量测温法似乎更容易发生峰后重置。来自其他超高温炉地点的闪石分析也证实了这一行为,在这些地方,辉绿岩中的钛-闪石测温仪的性能与球粒花岗岩中的铝-正辉石测温仪的性能相当。然而,在含金红石的样品中,钛辉石内温度被低估了,而且这种局限性并不像以前认为的那样仅限于含高浓度 H2O 的岩石。推导出的钛在闪石中的扩散约束条件证明了钛在闪石中温度计对后期热扰动的稳健性。然而,为了提高校准的准确性和精确性并扩大其适用范围,仍有必要进行临时实验。这一进展将使黑云母花岗岩成为了解超高温变质作用区域范围的常规研究目标。
{"title":"Effectiveness of Ti-in-amphibole thermometry and performance of different thermometers across lower continental crust up to UHT metamorphism","authors":"Omar Bartoli, Bruna B. Carvalho, Federico Farina","doi":"10.1007/s00410-024-02149-6","DOIUrl":"https://doi.org/10.1007/s00410-024-02149-6","url":null,"abstract":"<p>Metabasites are important constituents of deep crustal sections and are the favored rock type for studying lower crustal amphibolite to granulite transitions. However, metapelites may develop a larger number of temperature-sensitive mineral assemblages and are particular useful when extreme ultrahigh temperature (UHT) conditions are envisaged. A recent calibration of the Ti-in-amphibole thermometer by Liao et al. (2021) was supposed to make thermometry on metabasites quick and easy to apply. However, their calibration is based on experiments which were not originally designed to investigate in detail the temperature dependence of Ti in amphibole. In addition, a possible effect of <i>a</i><sub>TiO2</sub> and/or pressure on the Ti content of amphibole was not fully taken into account. This resulted in a calibration uncertainty of ± 70 °C (2σ), much higher than that of other single-mineral thermometers. In this study we firstly test the newly calibrated Ti-in-amphibole thermometer across the mid to lower crustal section of the Ivrea–Verbano Zone (IVZ; NW Italy) and compare the performance of different thermometric techniques across the sequence. Ti-in-amphibole thermometry records increasing peak temperatures from amphibolite (600–700 °C), transition (750–800 °C) and granulite (850–950 °C) zones. Titanium content of amphibole may be modified by retrograde fluid influx returning temperatures c. 200–300 °C lower than in non-altered domains. The comparison reveals that Zr-in-rutile thermometer in pelitic granulites seems to be more prone to post-peak resetting than the Ti-in-amphibole thermometry in nearby mafic rocks. This behavior is also confirmed by amphibole analyses from other UHT localities, where the performance of Ti-in-amphibole thermometry is comparable with that of Al-in-orthopyroxene in pelitic granulites. However, Ti-in-amphibole temperatures are underestimated in rutile-bearing samples and this limitation is not solely restricted to rocks containing high H<sub>2</sub>O contents as previously thought. Derived constraints on the diffusivity of Ti through amphibole demonstrate the robustness of the Ti-in-amphibole thermometer to later thermal disturbances. However, ad-hoc experiments are still necessary to improve the accuracy and precision of calibration and to extend its applicability. This advance will make mafic granulites routine targets for studies devoted to understanding the regional extent of UHT metamorphism.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141256964","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 : 2024-06-01DOI: 10.1007/s00410-024-02144-x
D. Neave, Alexander G. Stewart, Margaret E. Hartley, O. Namur
{"title":"Iron valence systematics in clinopyroxene crystals from ocean island basalts","authors":"D. Neave, Alexander G. Stewart, Margaret E. Hartley, O. Namur","doi":"10.1007/s00410-024-02144-x","DOIUrl":"https://doi.org/10.1007/s00410-024-02144-x","url":null,"abstract":"","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141408639","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 : 2024-06-01DOI: 10.1007/s00410-024-02150-z
D. Heuser, R. Dubosq, E. Petrishcheva, G. Bian, C. Rentenberger, C. L. Lengauer, B. Gault, G. Habler, R. Abart
{"title":"Coherent solvus of disordered alkali feldspar: experiment, atom probe tomography and thermodynamic model","authors":"D. Heuser, R. Dubosq, E. Petrishcheva, G. Bian, C. Rentenberger, C. L. Lengauer, B. Gault, G. Habler, R. Abart","doi":"10.1007/s00410-024-02150-z","DOIUrl":"https://doi.org/10.1007/s00410-024-02150-z","url":null,"abstract":"","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141390475","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 : 2024-05-29DOI: 10.1007/s00410-024-02130-3
S. Stumpf, E. Skrzypek, K. Stüwe
We use U–Pb dating of allanite and REE-rich epidote in three polymetamorphosed units from the Eastern Alps to constrain the timing of prograde metamorphism. All three units (Ennstal, Wölz and Rappold Complex) record several metamorphic cycles (Variscan, Permian and Eoalpine) and presently define an Eoalpine (Cretaceous) metamorphic field gradient from lower greenschist to amphibolite facies. For U–Pb data, a method is introduced to test the magnitude of 230Th disequilibrium and potentially approximate the Th/U ratio of the reservoir out of which allanite and REE-rich epidote grew. We also show that the modelled stability of epidote-group minerals in the REE-free MnNCKFMASH and MnNCKFMASHTO systems and REE-bearing systems is nearly identical. By combining the stability fields of (clino-)zoisite and epidote modelled in REE-free systems with known geothermal gradients for the region, REE-rich epidote growth is constrained to 200–450 °C and 0.2–0.8 GPa during prograde metamorphism. In the Rappold Complex, allanite cores yield a Variscan age of ca. 327 Ma. In the Ennstal and Wölz Complex, allanite growth during the Permian event occurred at ca. 279–286 Ma. Importantly, recrystallized allanite laths and REE-rich epidote overgrowths in samples from all three units yield prograde Eoalpine ages of ca. 100 Ma, even though these units subsequently reached different peak conditions, most likely at different times. This suggests that all units were buried roughly at the same time during the onset of Eoalpine continental subduction. This interpretation leaves room for the model proposing that diachronous peak metamorphic conditions reported for the field gradient may be related to the inertia of thermal equilibration rather than tectonic processes.
{"title":"Dating prograde metamorphism: U–Pb geochronology of allanite and REE-rich epidote in the Eastern Alps","authors":"S. Stumpf, E. Skrzypek, K. Stüwe","doi":"10.1007/s00410-024-02130-3","DOIUrl":"https://doi.org/10.1007/s00410-024-02130-3","url":null,"abstract":"<p>We use U–Pb dating of allanite and REE-rich epidote in three polymetamorphosed units from the Eastern Alps to constrain the timing of prograde metamorphism. All three units (Ennstal, Wölz and Rappold Complex) record several metamorphic cycles (Variscan, Permian and Eoalpine) and presently define an Eoalpine (Cretaceous) metamorphic field gradient from lower greenschist to amphibolite facies. For U–Pb data, a method is introduced to test the magnitude of <sup>230</sup>Th disequilibrium and potentially approximate the Th/U ratio of the reservoir out of which allanite and REE-rich epidote grew. We also show that the modelled stability of epidote-group minerals in the REE-free MnNCKFMASH and MnNCKFMASHTO systems and REE-bearing systems is nearly identical. By combining the stability fields of (clino-)zoisite and epidote modelled in REE-free systems with known geothermal gradients for the region, REE-rich epidote growth is constrained to 200–450 °C and 0.2–0.8 GPa during prograde metamorphism. In the Rappold Complex, allanite cores yield a Variscan age of ca. 327 Ma. In the Ennstal and Wölz Complex, allanite growth during the Permian event occurred at ca. 279–286 Ma. Importantly, recrystallized allanite laths and REE-rich epidote overgrowths in samples from all three units yield prograde Eoalpine ages of ca. 100 Ma, even though these units subsequently reached different peak conditions, most likely at different times. This suggests that all units were buried roughly at the same time during the onset of Eoalpine continental subduction. This interpretation leaves room for the model proposing that diachronous peak metamorphic conditions reported for the field gradient may be related to the inertia of thermal equilibration rather than tectonic processes.</p>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141168392","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}