Pub Date : 2023-12-14DOI: 10.1093/petrology/egad087
Daniel A Coulthard Jr, Raimundo Brahm, Charline Lormand, Georg F Zellmer, Naoya Sakamoto, Yoshiyuki Iizuka, Hisayoshi Yurimoto
The residence timescales of antecrystic minerals contribute a key piece of information regarding the petrologic evolution of transcrustal magmatic systems and may be inferred using a combination of observations derived from microanalytical chemistry and diffusion modelling. Here, we present state-of-the-art stacked CMOS-type active pixel sensor (SCAPS) isotopographic images of tephra-hosted plagioclase microantecrysts from Tongariro Volcanic Centre in the southern Taupo Volcanic Zone, New Zealand. These crystals exhibit high-frequency Sr and anorthite zonation at sub-micron spatial resolution. We also find that all crystals display high-frequency intracrystalline Sr chemical potential variations, indicating that they have not resided at magmatic temperature for diffusive relaxation to advance significantly. To quantify crystal residence times at the well-constrained magmatic temperatures of these tephras, we first forward-modeled intracrystalline Sr diffusion over time using numerical methods. Results were then analyzed using novel spatial Fourier-transform techniques developed to understand the systematics the diffusive decay of Sr disequilibria in the spatial frequency domain. This ultimately permitted the estimation of Sr concentration profiles at crystal formation, prior to uptake into the carrier melt at the onset of eruption. Our data imply residence times of days to weeks for the studied microantecrysts. This is inconsistent with long antecryst residence times in magmatic mushes at elevated temperatures, pointing instead to a cool plutonic nature of the magmatic plumbing system beneath the southern Taupo Volcanic Zone.
{"title":"Plutonic nature of a transcrustal magmatic system: evidence from ultrahigh resolution Sr-disequilibria in plagioclase microantecrysts from the southern Taupo Volcanic Zone, New Zealand","authors":"Daniel A Coulthard Jr, Raimundo Brahm, Charline Lormand, Georg F Zellmer, Naoya Sakamoto, Yoshiyuki Iizuka, Hisayoshi Yurimoto","doi":"10.1093/petrology/egad087","DOIUrl":"https://doi.org/10.1093/petrology/egad087","url":null,"abstract":"The residence timescales of antecrystic minerals contribute a key piece of information regarding the petrologic evolution of transcrustal magmatic systems and may be inferred using a combination of observations derived from microanalytical chemistry and diffusion modelling. Here, we present state-of-the-art stacked CMOS-type active pixel sensor (SCAPS) isotopographic images of tephra-hosted plagioclase microantecrysts from Tongariro Volcanic Centre in the southern Taupo Volcanic Zone, New Zealand. These crystals exhibit high-frequency Sr and anorthite zonation at sub-micron spatial resolution. We also find that all crystals display high-frequency intracrystalline Sr chemical potential variations, indicating that they have not resided at magmatic temperature for diffusive relaxation to advance significantly. To quantify crystal residence times at the well-constrained magmatic temperatures of these tephras, we first forward-modeled intracrystalline Sr diffusion over time using numerical methods. Results were then analyzed using novel spatial Fourier-transform techniques developed to understand the systematics the diffusive decay of Sr disequilibria in the spatial frequency domain. This ultimately permitted the estimation of Sr concentration profiles at crystal formation, prior to uptake into the carrier melt at the onset of eruption. Our data imply residence times of days to weeks for the studied microantecrysts. This is inconsistent with long antecryst residence times in magmatic mushes at elevated temperatures, pointing instead to a cool plutonic nature of the magmatic plumbing system beneath the southern Taupo Volcanic Zone.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"27 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138692374","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 : 2023-12-07DOI: 10.1093/petrology/egad088
Sander M Molendijk, Olivier Namur, Ephrem Kamate Kaleghetso, Paul R D Mason, Benoît Smets, Jacqueline Vander Auwera, David A Neave
The Nyiragongo volcano is one of the most alkali-rich volcanic centres on the planet (Na2O + K2O generally >10 wt.%, agpaitic index up to 1.34), characterized by a semi-permanently active lava lake which hosts silica-undersaturated (SiO2 <40 wt.%), low viscosity lavas. To improve our understanding of this unique magmatic system, we present a set of 291 samples, acquired during new field excursions between 2017 and 2021. The major and trace element composition of all samples was measured, revealing a lithological range extending from primitive picrites (Mg# 82) erupted from parasitic cones to a variety of highly evolved nephelinites, leucitites, and melilitites erupted from the main edifice as recently as 2002, 2016, and 2021. We measured major and trace element compositions from the full spectrum of minerals present in all sampled lithologies. From these we calculated that the main magma reservoirs feeding Nyiragongo are at approximately 9 – 15 and 21 – 33 km depth, in agreement with recent seismic observations. Fractional crystallization modelling using observed mineral compositions and proportions was performed to quantitatively link the lithologies to specific residual liquid fractions assuming evolution from an olivine-melilite parental melt. Our modelling indicates that fractionation cumulate formation in deep chambers reduces the melt fraction remaining to ~60%, after which melts are injected into upper, liquid dominated magma chambers where fractionation and accumulation of clinopyroxene, melilite, and feldspathoids dominate. Characterisation of mineral textures and geochemistry reveals high crystal mobility in a repeatedly recharging plumbing system split between liquid-dominated, evolved magma chambers and more solid-dominated, primitive mushes, decreasing in liquid fraction with depth.
{"title":"Plumbing system architecture and differentiation processes of the Nyiragongo volcano, DR Congo","authors":"Sander M Molendijk, Olivier Namur, Ephrem Kamate Kaleghetso, Paul R D Mason, Benoît Smets, Jacqueline Vander Auwera, David A Neave","doi":"10.1093/petrology/egad088","DOIUrl":"https://doi.org/10.1093/petrology/egad088","url":null,"abstract":"The Nyiragongo volcano is one of the most alkali-rich volcanic centres on the planet (Na2O + K2O generally &gt;10 wt.%, agpaitic index up to 1.34), characterized by a semi-permanently active lava lake which hosts silica-undersaturated (SiO2 &lt;40 wt.%), low viscosity lavas. To improve our understanding of this unique magmatic system, we present a set of 291 samples, acquired during new field excursions between 2017 and 2021. The major and trace element composition of all samples was measured, revealing a lithological range extending from primitive picrites (Mg# 82) erupted from parasitic cones to a variety of highly evolved nephelinites, leucitites, and melilitites erupted from the main edifice as recently as 2002, 2016, and 2021. We measured major and trace element compositions from the full spectrum of minerals present in all sampled lithologies. From these we calculated that the main magma reservoirs feeding Nyiragongo are at approximately 9 – 15 and 21 – 33 km depth, in agreement with recent seismic observations. Fractional crystallization modelling using observed mineral compositions and proportions was performed to quantitatively link the lithologies to specific residual liquid fractions assuming evolution from an olivine-melilite parental melt. Our modelling indicates that fractionation cumulate formation in deep chambers reduces the melt fraction remaining to ~60%, after which melts are injected into upper, liquid dominated magma chambers where fractionation and accumulation of clinopyroxene, melilite, and feldspathoids dominate. Characterisation of mineral textures and geochemistry reveals high crystal mobility in a repeatedly recharging plumbing system split between liquid-dominated, evolved magma chambers and more solid-dominated, primitive mushes, decreasing in liquid fraction with depth.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"165 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138555136","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 : 2023-12-01DOI: 10.1093/petrology/egad089
{"title":"Correction to: A Comparison of Oxygen Fugacities of Strongly Peraluminous Granites across the Archean-Proterozoic Boundary and Strongly Peraluminous Granites across the Archean-Proterozoic Transition","authors":"","doi":"10.1093/petrology/egad089","DOIUrl":"https://doi.org/10.1093/petrology/egad089","url":null,"abstract":"","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"87 ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139016638","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 : 2023-11-20DOI: 10.1093/petrology/egad083
Anindita Dey, Sirina Roy Choudhury, Pulak Sengupta
Corona texture is defined by the development of partial or complete rim of one or more minerals around a central reactant mineral depicting limited mass transport (local equilibration) in the length scale of the coronitic layers. The mineral assemblages forming corona texture in a metamorphic rock are commonly used to trace the P-T-X conditions through which the rock evolved during various tectonic processes. However, without a proper assessment of the changes in the equilibration volume (EV) and its effect on the mineralogy, any petrological interpretation deduced from the coronitic texture may be incorrect. In this study, we demonstrate that the double corona texture, observed in a suite of Mg-Al rich ortho-amphibole cordierite-bearing rock from the Cauvery Shear Systemin (Southern Granulite Terrane, India), developed in response to the continuously evolving EV. The studied rock contains aluminosilicate porphyroblasts that are set in a matrix of ortho-amphibole ± quartz. The aluminosilicate porphyroblasts are rimmed successively by an inner symplectic corona of sapphirine + cordierite, and an outer mono-mineralic corona of cordierite (near ortho-amphibole). Locally, patches of corundum with a rind of cordierite grow preferentially along the interface of aluminosilicate and the inner symplectic corona. Based on detailed petrography and mineral composition analyses, the corona textures are interpreted to have formed through a sequence of different chemical reactions that occurred in local micro-domains. We calculated quantitative P-T pseudosection in a NCFMASHT (Na2O-CaO-FeO-MgO-Al2O3-SiO2- H2O-TiO2) system and activity-adjusted P-T petrogenetic grid in a MASH (MgO-Al2O3-SiO2- H2O) system which, together, suggest that the coronitic assemblages were formed in response to a steeply decompressive retrograde P-T path from >8.8 kbar to <6 kbar, at a nearly constant temperature of ~700°C. Changes in EV in response to the limited transport of chemical components during the formation of corona texture were investigated through isothermal P-μMgO, P-μSiO2, and P-μMgO-μSiO2 MASH diagrams. Our results quantitatively model the continuously changing chemical potential landscape (P-μMgO- μSiO2 evolution path) around the central aluminosilicate porphyroblast within the corona-bearing micro-domain. The path demonstrates that a gradually shrinking EV around the central aluminosilicate during retrogression led to the sequential change of mineral reactions and equilibrium mineral assemblages, and resulted in the formation of multiple coronae. Unavailability of fluids and/or rapid exhumation is considered as the most dominant factors responsible for the decreasing elemental mobility and the consequent shrinking in EV in the studied rock.
{"title":"Competing roles of evolving P-T conditions, equilibration volume and chemical potential landscape in the formation of corona texture: a case study from the Southern Granulite Terrane, India","authors":"Anindita Dey, Sirina Roy Choudhury, Pulak Sengupta","doi":"10.1093/petrology/egad083","DOIUrl":"https://doi.org/10.1093/petrology/egad083","url":null,"abstract":"Corona texture is defined by the development of partial or complete rim of one or more minerals around a central reactant mineral depicting limited mass transport (local equilibration) in the length scale of the coronitic layers. The mineral assemblages forming corona texture in a metamorphic rock are commonly used to trace the P-T-X conditions through which the rock evolved during various tectonic processes. However, without a proper assessment of the changes in the equilibration volume (EV) and its effect on the mineralogy, any petrological interpretation deduced from the coronitic texture may be incorrect. In this study, we demonstrate that the double corona texture, observed in a suite of Mg-Al rich ortho-amphibole cordierite-bearing rock from the Cauvery Shear Systemin (Southern Granulite Terrane, India), developed in response to the continuously evolving EV. The studied rock contains aluminosilicate porphyroblasts that are set in a matrix of ortho-amphibole ± quartz. The aluminosilicate porphyroblasts are rimmed successively by an inner symplectic corona of sapphirine + cordierite, and an outer mono-mineralic corona of cordierite (near ortho-amphibole). Locally, patches of corundum with a rind of cordierite grow preferentially along the interface of aluminosilicate and the inner symplectic corona. Based on detailed petrography and mineral composition analyses, the corona textures are interpreted to have formed through a sequence of different chemical reactions that occurred in local micro-domains. We calculated quantitative P-T pseudosection in a NCFMASHT (Na2O-CaO-FeO-MgO-Al2O3-SiO2- H2O-TiO2) system and activity-adjusted P-T petrogenetic grid in a MASH (MgO-Al2O3-SiO2- H2O) system which, together, suggest that the coronitic assemblages were formed in response to a steeply decompressive retrograde P-T path from &gt;8.8 kbar to &lt;6 kbar, at a nearly constant temperature of ~700°C. Changes in EV in response to the limited transport of chemical components during the formation of corona texture were investigated through isothermal P-μMgO, P-μSiO2, and P-μMgO-μSiO2 MASH diagrams. Our results quantitatively model the continuously changing chemical potential landscape (P-μMgO- μSiO2 evolution path) around the central aluminosilicate porphyroblast within the corona-bearing micro-domain. The path demonstrates that a gradually shrinking EV around the central aluminosilicate during retrogression led to the sequential change of mineral reactions and equilibrium mineral assemblages, and resulted in the formation of multiple coronae. Unavailability of fluids and/or rapid exhumation is considered as the most dominant factors responsible for the decreasing elemental mobility and the consequent shrinking in EV in the studied rock.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"25 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138516843","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 : 2023-11-13DOI: 10.1093/petrology/egad082
Karoline Brückel, Craig Campbell Lundstrom, Michael Ackerson, Christopher Campe
How silicic magmas are stored in the upper crust before they erupt to form 100-1000s km3 ash-sheets remains a fundamental, but unanswered question in volcanology. While some studies posit storage in an eruptible state at low viscosity (<50% crystals) and high temperatures (>760-740°C) (warm storage), others suggest storage in a rigid state (>50% crystals) at lower, near-solidus temperatures (cold storage). Storage temperature and time spent near the solidus are typically constrained by mineral thermometry and diffusional relaxation modelling (at a given temperature), respectively. Since quartz is abundant over a range of temperatures and compositions and can incorporate titanium (Ti) at magmatic temperatures, a Ti-in-Quartz thermometer has been calibrated and Ti diffusion coefficients (DTi) have been measured. However, simply applying this thermometer or diffusion coefficient to volcanic quartz is burdened by an ongoing debate regarding their experimental calibration. This debate centers around three recent Ti-in-Quartz thermometers by Huang & Audétat (2012), Zhang et al. (2020), Osborne et al. (2022) and three DTi by Cherniak et al. (2007), Jollands et al. (2020), Audétat et al. (2021), each of which when applied to igneous systems favors either warm or cold storage. To determine their applicability for estimating the pre-eruptive thermal history of silicic magmatic systems, we apply the different Ti-in-Quartz thermometers and DTi to quartz from the Fish Canyon Tuff (USA). This tuff is an optimal location for such a study because it is a prime example of cold storage with multiple previous studies providing constraints on its storage conditions. We find that a temperature of 737 ± 16°C using the Zhang et al. (2020) thermometer is the most consistent with other temperature estimates for the Fish Canyon Tuff. Temperatures calculated using Huang & Audétat (2012) are acceptable, while those using Osborne et al. (2022) are unrealistic. Applying each of the DTi to quartz in the Fish Canyon Tuff and comparing these timescales to timescales from Ba-in-Sanidine diffusion and the total storage time of the mush (derived from the range in zircon U-Pb ages and the local eruption history), three different scenarios for pre-eruptive storage are possible. At a temperature of 737°C, timescales using DTi by Audétat et al. (2021) exceed the total storage time of the Fish Canyon system by ~2 Myr. These DTi are only consistent if storage temperatures were significantly higher, implying warm storage. Such a scenario is inconsistent with cold storage of the Fish Canyon system. Timescales derived from DTi by Jollands et al. (2020) and Cherniak et al. (2007) are consistent with cold storage of the Fish Canyon system. While DTi by Jollands et al. (2020) suggest long-term storage near 737°C and an extended period of pre-eruptive reheating, DTi by Cherniak et al. (2007) suggests storage below 737°C and rapid reheating.
在火山学中，硅质岩浆在喷发形成100-1000立方千米的火山灰层之前是如何储存在地壳上层的，这仍然是一个基本的、但没有答案的问题。虽然一些研究认为在低粘度(50%晶体)和高温(>760-740°C)(温暖储存)下以可爆发状态储存，但其他研究建议在较低的接近固体温度(冷藏)下以刚性状态(>50%晶体)储存。在固体附近的储存温度和时间通常分别受到矿物测温和扩散松弛模型(在给定温度下)的限制。由于石英在一定的温度和成分范围内都很丰富，并且可以在岩浆温度下结合钛(Ti)，因此校准了石英中钛温度计并测量了钛扩散系数(DTi)。然而，简单地将这种温度计或扩散系数应用于火山石英，就其实验校准存在持续的争论。这场争论集中在Huang &audsamat (2012)， Zhang et al. (2020)， Osborne et al.(2022)以及Cherniak et al. (2007)， Jollands et al. (2020)， audsamat et al.(2021)的三个DTi，当应用于火成系统时，每个DTi都有利于加热或冷藏。为了确定它们在估计硅质岩浆系统喷发前热史方面的适用性，我们将不同的ti -in-石英温度计和DTi应用于美国Fish Canyon凝灰岩中的石英。这种凝灰岩是进行此类研究的最佳地点，因为它是冷藏的主要例子，先前的多项研究对其储存条件提供了限制。我们发现，使用Zhang等人(2020)的温度计得出的737±16°C的温度与鱼峡谷凝灰岩的其他温度估计最一致。使用Huang &计算温度aud(2012)是可以接受的，而那些使用Osborne等人(2022)是不现实的。将每种DTi应用于鱼谷凝灰岩中的石英，并将这些时间尺度与Ba-in-Sanidine扩散的时间尺度和糊状的总储存时间(由锆石U-Pb年龄范围和当地喷发历史得出)进行比较，可以得出喷发前储存的三种不同情景。在737°C的温度下，audsamdat等人(2021)使用DTi的时间尺度超过了Fish Canyon系统的总储存时间约2 Myr。这些DTi只有在储存温度明显较高时才一致，这意味着温度较高。这种情况与鱼峡谷系统的冷库不一致。Jollands等人(2020)和Cherniak等人(2007)从DTi得到的时间尺度与Fish Canyon系统的冷库一致。Jollands等人(2020)的DTi建议在737°C附近长期储存并延长喷发前的再加热时间，而Cherniak等人(2007)的DTi建议在737°C以下储存并快速再加热。
{"title":"Testing the limits of Ti-in-Quartz thermometry and diffusion modelling to determine the thermal history of the Fish Canyon Tuff","authors":"Karoline Brückel, Craig Campbell Lundstrom, Michael Ackerson, Christopher Campe","doi":"10.1093/petrology/egad082","DOIUrl":"https://doi.org/10.1093/petrology/egad082","url":null,"abstract":"How silicic magmas are stored in the upper crust before they erupt to form 100-1000s km3 ash-sheets remains a fundamental, but unanswered question in volcanology. While some studies posit storage in an eruptible state at low viscosity (&lt;50% crystals) and high temperatures (&gt;760-740°C) (warm storage), others suggest storage in a rigid state (&gt;50% crystals) at lower, near-solidus temperatures (cold storage). Storage temperature and time spent near the solidus are typically constrained by mineral thermometry and diffusional relaxation modelling (at a given temperature), respectively. Since quartz is abundant over a range of temperatures and compositions and can incorporate titanium (Ti) at magmatic temperatures, a Ti-in-Quartz thermometer has been calibrated and Ti diffusion coefficients (DTi) have been measured. However, simply applying this thermometer or diffusion coefficient to volcanic quartz is burdened by an ongoing debate regarding their experimental calibration. This debate centers around three recent Ti-in-Quartz thermometers by Huang & Audétat (2012), Zhang et al. (2020), Osborne et al. (2022) and three DTi by Cherniak et al. (2007), Jollands et al. (2020), Audétat et al. (2021), each of which when applied to igneous systems favors either warm or cold storage. To determine their applicability for estimating the pre-eruptive thermal history of silicic magmatic systems, we apply the different Ti-in-Quartz thermometers and DTi to quartz from the Fish Canyon Tuff (USA). This tuff is an optimal location for such a study because it is a prime example of cold storage with multiple previous studies providing constraints on its storage conditions. We find that a temperature of 737 ± 16°C using the Zhang et al. (2020) thermometer is the most consistent with other temperature estimates for the Fish Canyon Tuff. Temperatures calculated using Huang & Audétat (2012) are acceptable, while those using Osborne et al. (2022) are unrealistic. Applying each of the DTi to quartz in the Fish Canyon Tuff and comparing these timescales to timescales from Ba-in-Sanidine diffusion and the total storage time of the mush (derived from the range in zircon U-Pb ages and the local eruption history), three different scenarios for pre-eruptive storage are possible. At a temperature of 737°C, timescales using DTi by Audétat et al. (2021) exceed the total storage time of the Fish Canyon system by ~2 Myr. These DTi are only consistent if storage temperatures were significantly higher, implying warm storage. Such a scenario is inconsistent with cold storage of the Fish Canyon system. Timescales derived from DTi by Jollands et al. (2020) and Cherniak et al. (2007) are consistent with cold storage of the Fish Canyon system. While DTi by Jollands et al. (2020) suggest long-term storage near 737°C and an extended period of pre-eruptive reheating, DTi by Cherniak et al. (2007) suggests storage below 737°C and rapid reheating.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"53 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503738","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 : 2023-11-07DOI: 10.1093/petrology/egad081
Hadi Shafaii Moghadam, Kaj A Hoernle, Folkmar Hauff, Massimo Chiaradia, Dieter Garbe-Schönberg, Teresa Orozco-Esquivel, Ilya N Bindeman, Orhan Karsli, Ghasem Ghorbani, Naeim Mousavi, Federico Lucci
Abstract Post-collisional volcanism contains important clues for understanding the processes that prevail in orogenic belts, including those in the mantle and the uplift and collapse of continents. Here we report new geochronological and geochemical data for a suite of post-collisional Miocene to Pleistocene volcanic rocks from northwest Iran. Four groups of volcanic rocks can be distinguished according to their geochemical and isotopic signatures, including: (1) Miocene depleted lavas with high Nd and Hf but low Pb and Sr isotopic ratios, (2) less depleted lavas with quite variable Pb isotopic composition, (3) lavas with non-radiogenic Nd and Hf isotopic values, but highly radiogenic Sr and Pb isotopic composition, and (4) Pleistocene adakitic rocks with depleted isotopic signatures. The isotopic data reveal that the Miocene rocks are derived from asthenospheric and highly heterogeneous sub-continental lithospheric mantle sources. Evidence suggests that the lithospheric mantle contains recycled upper continental material and is isotopically similar to the enriched mantle two (EMII) endmember. Analysis of Sr-Nd-Pb-Hf-O isotopes in both mineral and rock groundmass, in conjunction with energy-constrained assimilation and fractional crystallization (EC-AFC) numerical modeling, demonstrates that the incorporation of continental crust during magma fractionation via AFC had an insignificant impact on the isotopic composition of the Miocene lavas. Moreover, adakites are the youngest rocks and show a geochemical signature consistent with the partial melting of a young and mafic continental lower crust. Both seismological data and geochemical signatures on these Miocene to Pleistocene volcanic rocks indicate the initiation of asthenospheric upwelling and orogen uplift in the Arabia-Eurasia collision zone, which occurred after slab break-off, following the Neotethyan closure.
{"title":"Middle-Late Miocene to Pleistocene post-collisional magmatism in the Arabia-Eurasia collision zone, an example from northwest Iran","authors":"Hadi Shafaii Moghadam, Kaj A Hoernle, Folkmar Hauff, Massimo Chiaradia, Dieter Garbe-Schönberg, Teresa Orozco-Esquivel, Ilya N Bindeman, Orhan Karsli, Ghasem Ghorbani, Naeim Mousavi, Federico Lucci","doi":"10.1093/petrology/egad081","DOIUrl":"https://doi.org/10.1093/petrology/egad081","url":null,"abstract":"Abstract Post-collisional volcanism contains important clues for understanding the processes that prevail in orogenic belts, including those in the mantle and the uplift and collapse of continents. Here we report new geochronological and geochemical data for a suite of post-collisional Miocene to Pleistocene volcanic rocks from northwest Iran. Four groups of volcanic rocks can be distinguished according to their geochemical and isotopic signatures, including: (1) Miocene depleted lavas with high Nd and Hf but low Pb and Sr isotopic ratios, (2) less depleted lavas with quite variable Pb isotopic composition, (3) lavas with non-radiogenic Nd and Hf isotopic values, but highly radiogenic Sr and Pb isotopic composition, and (4) Pleistocene adakitic rocks with depleted isotopic signatures. The isotopic data reveal that the Miocene rocks are derived from asthenospheric and highly heterogeneous sub-continental lithospheric mantle sources. Evidence suggests that the lithospheric mantle contains recycled upper continental material and is isotopically similar to the enriched mantle two (EMII) endmember. Analysis of Sr-Nd-Pb-Hf-O isotopes in both mineral and rock groundmass, in conjunction with energy-constrained assimilation and fractional crystallization (EC-AFC) numerical modeling, demonstrates that the incorporation of continental crust during magma fractionation via AFC had an insignificant impact on the isotopic composition of the Miocene lavas. Moreover, adakites are the youngest rocks and show a geochemical signature consistent with the partial melting of a young and mafic continental lower crust. Both seismological data and geochemical signatures on these Miocene to Pleistocene volcanic rocks indicate the initiation of asthenospheric upwelling and orogen uplift in the Arabia-Eurasia collision zone, which occurred after slab break-off, following the Neotethyan closure.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"110 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135545743","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 : 2023-10-31DOI: 10.1093/petrology/egad080
Valerie A Finlayson, Mitchell Haller, James M D Day, Stephen Ginley, Brian O’Driscoll, Asko Kontinen, Eero Hanski, Richard J Walker
Abstract The ca. 1.95 Ga Jormua Ophiolite Complex (JOC), Finland, is a rare Paleoproterozoic ophiolite that preserves a record of diverse upper mantle materials and melting processes. Meter-scale grid sampling of four JOC outcrops, as well as non-grid samples, permits evaluation of meter- to kilometer-scale mantle heterogeneity within the JOC. Significant heterogeneity is observed between the four grids, and also among a number of the non-grid samples examined. Variations in the concentrations of fluid-mobile elements are particularly large among different samples and locations. New whole-rock major, lithophile trace, and highly siderophile element data (HSE: Os, Ir, Ru, Pt, Pd, Re), including 187Re-187Os isotopic data, for serpentinized harzburgites indicate the presence of two distinct compositional types and probable modes of origin within the JOC. This is consistent with prior findings. Type 1 is similar to modern refractory abyssal-type mantle. Type 2 is more highly refractory than Type 1, and most likely represents samples from sub-continental lithospheric mantle (SCLM). Type 1 mantle is moderately heterogeneous with respect to major and trace element and Os isotopic compositions at both the meter and kilometer scales. By contrast, Type 2 mantle is considerably more homogeneous than Type 1 grids at the meter scale, but is more heterogeneous at the kilometer scale. The median initial γOs value for Type 1 mantle, calculated for 1.95 Ga, is ~-2.0 (where γOs is the % deviation in 187Os/188Os relative to a chondritic reference calculated for a specified time). This isotopic composition is consistent with a moderate, long-term decrease in Re/Os relative to the estimate for Primitive Mantle, prior to JOC formation. The similarity in this γOs value to the value for the modern abyssal mantle, as well as the initial values for several Phanerozoic ophiolites suggests that the upper mantle achieved a Re/Os ratio similar to the chondritic reference by ~2 Ga, then evolved along a subparallel trajectory to the chondritic reference since then. For this to occur, only limited Re could have been permanently removed from the upper mantle since at least the time the JOC formed. A localized secondary metasomatic event at ~2 Ga, concurrent with the estimated obduction age for the JOC and subsequent Svecofennian Orogeny, affected the HSE systematics of some Type 1 samples. By contrast, late Archean Os TRD model ages for Type 2 rocks indicate a depletion event superimposed upon the long-term Re depletion of the abyssal mantle. This event was established no later than ~2.6 Ga and may have occurred during a period of significant, well-documented crustal production in the Karelia craton at ~2.7 Ga.
{"title":"Oceanic and continental lithospheric mantle in the 1.95 Ga Jormua Ophiolite Complex, Finland: implications for mantle and crustal evolution","authors":"Valerie A Finlayson, Mitchell Haller, James M D Day, Stephen Ginley, Brian O’Driscoll, Asko Kontinen, Eero Hanski, Richard J Walker","doi":"10.1093/petrology/egad080","DOIUrl":"https://doi.org/10.1093/petrology/egad080","url":null,"abstract":"Abstract The ca. 1.95 Ga Jormua Ophiolite Complex (JOC), Finland, is a rare Paleoproterozoic ophiolite that preserves a record of diverse upper mantle materials and melting processes. Meter-scale grid sampling of four JOC outcrops, as well as non-grid samples, permits evaluation of meter- to kilometer-scale mantle heterogeneity within the JOC. Significant heterogeneity is observed between the four grids, and also among a number of the non-grid samples examined. Variations in the concentrations of fluid-mobile elements are particularly large among different samples and locations. New whole-rock major, lithophile trace, and highly siderophile element data (HSE: Os, Ir, Ru, Pt, Pd, Re), including 187Re-187Os isotopic data, for serpentinized harzburgites indicate the presence of two distinct compositional types and probable modes of origin within the JOC. This is consistent with prior findings. Type 1 is similar to modern refractory abyssal-type mantle. Type 2 is more highly refractory than Type 1, and most likely represents samples from sub-continental lithospheric mantle (SCLM). Type 1 mantle is moderately heterogeneous with respect to major and trace element and Os isotopic compositions at both the meter and kilometer scales. By contrast, Type 2 mantle is considerably more homogeneous than Type 1 grids at the meter scale, but is more heterogeneous at the kilometer scale. The median initial γOs value for Type 1 mantle, calculated for 1.95 Ga, is ~-2.0 (where γOs is the % deviation in 187Os/188Os relative to a chondritic reference calculated for a specified time). This isotopic composition is consistent with a moderate, long-term decrease in Re/Os relative to the estimate for Primitive Mantle, prior to JOC formation. The similarity in this γOs value to the value for the modern abyssal mantle, as well as the initial values for several Phanerozoic ophiolites suggests that the upper mantle achieved a Re/Os ratio similar to the chondritic reference by ~2 Ga, then evolved along a subparallel trajectory to the chondritic reference since then. For this to occur, only limited Re could have been permanently removed from the upper mantle since at least the time the JOC formed. A localized secondary metasomatic event at ~2 Ga, concurrent with the estimated obduction age for the JOC and subsequent Svecofennian Orogeny, affected the HSE systematics of some Type 1 samples. By contrast, late Archean Os TRD model ages for Type 2 rocks indicate a depletion event superimposed upon the long-term Re depletion of the abyssal mantle. This event was established no later than ~2.6 Ga and may have occurred during a period of significant, well-documented crustal production in the Karelia craton at ~2.7 Ga.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135976655","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 : 2023-10-25DOI: 10.1093/petrology/egad079
Adam Andreas Garde, Leif Johansson, Nynke Keulen, Anja Schreiber, Richard Wirth
Abstract Extraterrestrial cratering was a critical component in the evolution of the early Earth, but discovery of very ancient and deeply exhumed impact structures remains elusive, as identification tools are in short supply. The recognition of such structures is hindered by post-cratering geological processes, whereby impact-induced features common in younger, upper-crustal craters may be lost. In this study we make a detailed analysis of planar microstructures in zircons from four large, confirmed impact structures (Manicouagan, Rochechouart, Sudbury, Vredefort) preserved at different crustal levels, from two previously described non-impact seismites in SW Norway and northern Italy, and from the 3.0 Ga Maniitsoq structure in West Greenland. A total of ~3400 zircon grains were studied using exterior and interior scanning and transmission electron microscopy. We show for the first time that shocked zircons contain two successive, principally different types of planar microstructures, only one of which is diagnostic of impact. Closely spaced, contiguous microplanes (CP) are formed first, presumably by the shock wave. In Manicouagan and Rochechouart zircons the exterior CPs have ultrathin interior counterparts of straight dislocation arrays, as identified in Manicouagan zircon using transmission electron microscopy. They have the same close spacing and orientations as the exterior CPs and are abundantly decorated with tiny pores down to less than 50 nm across. These interior CPs are identical to shock-induced decorated, partly annealed amorphous planar microstructures in quartz (planar deformation features, PDFs) and are interpreted as such. The second type is open planar fractures (PF). They are widely and irregularly spaced and texturally younger than the CPs. They re-use and displace the CP orientations, which they cut in stepwise fashion. We interpret these PFs as formed by impact-induced seismic shaking in the wake of the shock wave. We confirm two previous reports of isolated planar fractures in zircons from non-impact seismites, showing that PFs per se are not impact-diagnostic. There are no CPs in any of these zircons. Zircons from different parts of the Maniitsoq structure contain CPs in various states of preservation besides PFs, corroborating that this very large and very deeply exhumed structure resulted from an extraterrestrial impact.
{"title":"Zircon Microstructures in Large, Deeply Eroded Impact Structures and Terrestrial Seismites","authors":"Adam Andreas Garde, Leif Johansson, Nynke Keulen, Anja Schreiber, Richard Wirth","doi":"10.1093/petrology/egad079","DOIUrl":"https://doi.org/10.1093/petrology/egad079","url":null,"abstract":"Abstract Extraterrestrial cratering was a critical component in the evolution of the early Earth, but discovery of very ancient and deeply exhumed impact structures remains elusive, as identification tools are in short supply. The recognition of such structures is hindered by post-cratering geological processes, whereby impact-induced features common in younger, upper-crustal craters may be lost. In this study we make a detailed analysis of planar microstructures in zircons from four large, confirmed impact structures (Manicouagan, Rochechouart, Sudbury, Vredefort) preserved at different crustal levels, from two previously described non-impact seismites in SW Norway and northern Italy, and from the 3.0 Ga Maniitsoq structure in West Greenland. A total of ~3400 zircon grains were studied using exterior and interior scanning and transmission electron microscopy. We show for the first time that shocked zircons contain two successive, principally different types of planar microstructures, only one of which is diagnostic of impact. Closely spaced, contiguous microplanes (CP) are formed first, presumably by the shock wave. In Manicouagan and Rochechouart zircons the exterior CPs have ultrathin interior counterparts of straight dislocation arrays, as identified in Manicouagan zircon using transmission electron microscopy. They have the same close spacing and orientations as the exterior CPs and are abundantly decorated with tiny pores down to less than 50 nm across. These interior CPs are identical to shock-induced decorated, partly annealed amorphous planar microstructures in quartz (planar deformation features, PDFs) and are interpreted as such. The second type is open planar fractures (PF). They are widely and irregularly spaced and texturally younger than the CPs. They re-use and displace the CP orientations, which they cut in stepwise fashion. We interpret these PFs as formed by impact-induced seismic shaking in the wake of the shock wave. We confirm two previous reports of isolated planar fractures in zircons from non-impact seismites, showing that PFs per se are not impact-diagnostic. There are no CPs in any of these zircons. Zircons from different parts of the Maniitsoq structure contain CPs in various states of preservation besides PFs, corroborating that this very large and very deeply exhumed structure resulted from an extraterrestrial impact.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135218959","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}
Abstract We report new experimental data from ultrabasic basanite and ultrabasic tephrite as starting material compositions in the 1350°C to 1000°C temperature range. Crystallization experiments under low- to high-pressure (0.5–2.0 GPa) were carried out under reduced conditions (≈CCO buffer), while one-atmosphere, anhydrous, experiments were performed ranging from reduced to oxidized conditions (−2 ≤ ∆QFM ≤ +2). The results highlight the ƒO2 role on the silica saturation of the alkali liquids differentiated from these primary ultrabasic magmas, on the mineral assemblage, and its composition. The liquid lines of descent (LLDs) from basanite are sodic and strongly SiO2 undersaturated, whereas from tephrite, the LLDs are sodic-potassic/potassic for both weakly SiO2-undersaturated and SiO2-saturated compositions, being more silica saturated under oxidized conditions. At the lowest temperature experiments, the percentage of liquid remaining is significantly higher in the basanite-derived products (ca. 35 wt.%) than in tephrite, indicating that the equivalent magmas are more prone to produce larger quantities of evolved melts. The best obtained Fe–Mg olivine/melt and clinopyroxene/melt exchange coefficients for these alkali compositions considering the new and available data are ${K_D}_{Fe^{2+}- Mg}^{Ol- Alkali melt}=0.285pm 0.014$ and ${K_D}_{Fe^{2+}- Mg}^{Cpx- Alkali melt}=0.245pm 0.008$, slightly lower than those observed in tholeiitic melts. Clinopyroxene compositions are Ti–Al-rich and Si-poor as compared with common clinopyroxenes in subalkali systems. We suggest that Ti should be allocated in the tetrahedral sites substituting for Si and that its contents are inversely correlated with pressure. Our results allow a simple new barometer based on clinopyroxene-only compositions, as follows:$$ Pleft(pm 0.16 GPa,1sigma right)=16.028left(pm 1.042right) Na-6.715left(pm 0.727right)frac{Ti}{Ti+ Al(t)}+0.494left(pm 0.441right) Si+0.144left(pm 0.079right) $$where Na, Ti, Al(t), and Si are molar proportions relative to 6O. This formulation accounts for the jadeite (NaAlSi2O6) component, herein computed from the Na contents, corrected for the Ti-diopside (CaMgTi2O6) component in clinopyroxene and also considers the evolutionary trend from Mg-augite to ferroan diopside. It applies to alkali ultrabasic to intermediate compositions in the examined P–T–ƒO2 range, resulting in more accurate estimates than the available calibrations. The MgO-in-melt thermometer was optimized for the studied compositions at one-atmosphere pressure and anhydrous conditions, as follows:$$ T left(pm 5{}^{circ}C,1sigma right)=27.35left(pm 0.65right) big({MgO}^{liq}big)+984left(pm 4right) $$which provides much more reliable liquidus temperatures for these alkali systems. Given data restriction, this formulation may be expanded to include the pressure effects for relatively low-H2O (< 3 wt.%) systems as:$$ T left(pm 20{}^{circ}C,1sigma right)=27.35left(pm 0.65right)big({MgO}^{liq}
摘要在1350 ～ 1000℃的温度范围内，我们报道了超基性玄武岩和超基性翡翠作为起始材料组成的新实验数据。低至高压(0.5-2.0 GPa)的结晶实验在还原条件下(≈CCO缓冲液)进行，而一气无水的实验在还原至氧化条件下(−2≤∆QFM≤+2)进行。研究结果强调了ƒO2在这些原生超基性岩浆中区分的碱液体的硅饱和度、矿物组合及其组成方面的作用。玄武岩的液态下降线(LLDs)为钠质和强SiO2欠饱和，而软玉的液态下降线(LLDs)为弱SiO2欠饱和和SiO2饱和成分的钠质钾/钾质，在氧化条件下更饱和二氧化硅。在最低温度实验中，玄武岩衍生产品中剩余液体的百分比明显更高(约35 wt)。%) than in tephrite, indicating that the equivalent magmas are more prone to produce larger quantities of evolved melts. The best obtained Fe–Mg olivine/melt and clinopyroxene/melt exchange coefficients for these alkali compositions considering the new and available data are ${K_D}_{Fe^{2+}- Mg}^{Ol- Alkali melt}=0.285pm 0.014$ and ${K_D}_{Fe^{2+}- Mg}^{Cpx- Alkali melt}=0.245pm 0.008$, slightly lower than those observed in tholeiitic melts. Clinopyroxene compositions are Ti–Al-rich and Si-poor as compared with common clinopyroxenes in subalkali systems. We suggest that Ti should be allocated in the tetrahedral sites substituting for Si and that its contents are inversely correlated with pressure. Our results allow a simple new barometer based on clinopyroxene-only compositions, as follows:$$ Pleft(pm 0.16 GPa,1sigma right)=16.028left(pm 1.042right) Na-6.715left(pm 0.727right)frac{Ti}{Ti+ Al(t)}+0.494left(pm 0.441right) Si+0.144left(pm 0.079right) $$where Na, Ti, Al(t), and Si are molar proportions relative to 6O. This formulation accounts for the jadeite (NaAlSi2O6) component, herein computed from the Na contents, corrected for the Ti-diopside (CaMgTi2O6) component in clinopyroxene and also considers the evolutionary trend from Mg-augite to ferroan diopside. It applies to alkali ultrabasic to intermediate compositions in the examined P–T–ƒO2 range, resulting in more accurate estimates than the available calibrations. The MgO-in-melt thermometer was optimized for the studied compositions at one-atmosphere pressure and anhydrous conditions, as follows:$$ T left(pm 5{}^{circ}C,1sigma right)=27.35left(pm 0.65right) big({MgO}^{liq}big)+984left(pm 4right) $$which provides much more reliable liquidus temperatures for these alkali systems. Given data restriction, this formulation may be expanded to include the pressure effects for relatively low-H2O (< 3 wt.%) systems as:$$ T left(pm 20{}^{circ}C,1sigma right)=27.35left(pm 0.65right)big({MgO}^{liq}big)+80.20left(pm 5.50right)P(GPa)+981left(pm 4right) $$
{"title":"New experimental constraints for the evolution and thermobarometry of alkali ultrabasic to intermediate igneous rocks","authors":"Andrés Fabián Salazar-Naranjo, Silvio Roberto Farias Vlach","doi":"10.1093/petrology/egad078","DOIUrl":"https://doi.org/10.1093/petrology/egad078","url":null,"abstract":"Abstract We report new experimental data from ultrabasic basanite and ultrabasic tephrite as starting material compositions in the 1350°C to 1000°C temperature range. Crystallization experiments under low- to high-pressure (0.5–2.0 GPa) were carried out under reduced conditions (≈CCO buffer), while one-atmosphere, anhydrous, experiments were performed ranging from reduced to oxidized conditions (−2 ≤ ∆QFM ≤ +2). The results highlight the ƒO2 role on the silica saturation of the alkali liquids differentiated from these primary ultrabasic magmas, on the mineral assemblage, and its composition. The liquid lines of descent (LLDs) from basanite are sodic and strongly SiO2 undersaturated, whereas from tephrite, the LLDs are sodic-potassic/potassic for both weakly SiO2-undersaturated and SiO2-saturated compositions, being more silica saturated under oxidized conditions. At the lowest temperature experiments, the percentage of liquid remaining is significantly higher in the basanite-derived products (ca. 35 wt.%) than in tephrite, indicating that the equivalent magmas are more prone to produce larger quantities of evolved melts. The best obtained Fe–Mg olivine/melt and clinopyroxene/melt exchange coefficients for these alkali compositions considering the new and available data are ${K_D}_{Fe^{2+}- Mg}^{Ol- Alkali melt}=0.285pm 0.014$ and ${K_D}_{Fe^{2+}- Mg}^{Cpx- Alkali melt}=0.245pm 0.008$, slightly lower than those observed in tholeiitic melts. Clinopyroxene compositions are Ti–Al-rich and Si-poor as compared with common clinopyroxenes in subalkali systems. We suggest that Ti should be allocated in the tetrahedral sites substituting for Si and that its contents are inversely correlated with pressure. Our results allow a simple new barometer based on clinopyroxene-only compositions, as follows:$$ Pleft(pm 0.16 GPa,1sigma right)=16.028left(pm 1.042right) Na-6.715left(pm 0.727right)frac{Ti}{Ti+ Al(t)}+0.494left(pm 0.441right) Si+0.144left(pm 0.079right) $$where Na, Ti, Al(t), and Si are molar proportions relative to 6O. This formulation accounts for the jadeite (NaAlSi2O6) component, herein computed from the Na contents, corrected for the Ti-diopside (CaMgTi2O6) component in clinopyroxene and also considers the evolutionary trend from Mg-augite to ferroan diopside. It applies to alkali ultrabasic to intermediate compositions in the examined P–T–ƒO2 range, resulting in more accurate estimates than the available calibrations. The MgO-in-melt thermometer was optimized for the studied compositions at one-atmosphere pressure and anhydrous conditions, as follows:$$ T left(pm 5{}^{circ}C,1sigma right)=27.35left(pm 0.65right) big({MgO}^{liq}big)+984left(pm 4right) $$which provides much more reliable liquidus temperatures for these alkali systems. Given data restriction, this formulation may be expanded to include the pressure effects for relatively low-H2O (&lt; 3 wt.%) systems as:$$ T left(pm 20{}^{circ}C,1sigma right)=27.35left(pm 0.65right)big({MgO}^{liq}","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136034738","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 : 2023-10-11DOI: 10.1093/petrology/egad077
Yishen Zhang, Olivier Namur, Weiran Li, Oliver Shorttle, Esteban Gazel, Eleanor Jennings, Peter Thy, Timothy L Grove, Bernard Charlier
Abstract The application of the olivine–spinel aluminum exchange thermometer to natural samples is limited by the restricted experimental dataset on which it was calibrated. Here, we present a new dataset of 46 high-temperature crystallization experiments and 21 reanalyzed published experiments, which we used to extend the calibration to higher and lower temperatures. The final calibration dataset spans a range of conditions relevant to crustal and upper mantle processes: 1174–1606 °C, 0.1–1350 MPa, QFM−2.5 to QFM+7.2 (oxygen fugacity, fO2, reported in log units relative to the quartz–fayalite–magnetite buffer, QFM), and 0–7.4 wt.% H2Omelt. We propose three new models. The first is thermodynamically self-consistent, based on spinel Fe, Mg, Al, and Cr compositions and Al exchange between olivine and spinel. The second and third are empirical models that consider fewer elemental exchanges: the second uses only Al exchange and spinel compositions, whereas the third considers olivine–spinel Al and Cr exchange. All models include the modest effect of pressure on olivine-spinel equilibrium chemistry, whereas fO2 and water content have negligible effects. In general, as fewer elements are considered in the olivine–spinel exchange, the fit to experimental data worsens. Conversely, the associated decrease in model complexity improves their robustness against systematic errors when applied to natural crystal pairs: the thermodynamic model may underestimate crystallization temperatures in natural samples due to spinel subsolidus re-equilibration, whereas the empirical models (independent of Fe and Mg in spinel) are less sensitive to re-equilibration but yield temperatures with larger uncertainties. We applied a statistical test to select the most appropriate model for application to natural samples. When applied to lavas from mid-ocean ridges, Iceland, Skye, Emeishan, Etendeka, and Tortugal, our new temperature estimates are 30–100 °C lower than previously proposed. The lower temperature estimates cause a lower mantle melting temperature and significant impacts on the mantle lithology constraints.
{"title":"An extended calibration of the olivine–spinel aluminum exchange thermometer: Application to the melting conditions and mantle lithologies of large igneous provinces","authors":"Yishen Zhang, Olivier Namur, Weiran Li, Oliver Shorttle, Esteban Gazel, Eleanor Jennings, Peter Thy, Timothy L Grove, Bernard Charlier","doi":"10.1093/petrology/egad077","DOIUrl":"https://doi.org/10.1093/petrology/egad077","url":null,"abstract":"Abstract The application of the olivine–spinel aluminum exchange thermometer to natural samples is limited by the restricted experimental dataset on which it was calibrated. Here, we present a new dataset of 46 high-temperature crystallization experiments and 21 reanalyzed published experiments, which we used to extend the calibration to higher and lower temperatures. The final calibration dataset spans a range of conditions relevant to crustal and upper mantle processes: 1174–1606 °C, 0.1–1350 MPa, QFM−2.5 to QFM+7.2 (oxygen fugacity, fO2, reported in log units relative to the quartz–fayalite–magnetite buffer, QFM), and 0–7.4 wt.% H2Omelt. We propose three new models. The first is thermodynamically self-consistent, based on spinel Fe, Mg, Al, and Cr compositions and Al exchange between olivine and spinel. The second and third are empirical models that consider fewer elemental exchanges: the second uses only Al exchange and spinel compositions, whereas the third considers olivine–spinel Al and Cr exchange. All models include the modest effect of pressure on olivine-spinel equilibrium chemistry, whereas fO2 and water content have negligible effects. In general, as fewer elements are considered in the olivine–spinel exchange, the fit to experimental data worsens. Conversely, the associated decrease in model complexity improves their robustness against systematic errors when applied to natural crystal pairs: the thermodynamic model may underestimate crystallization temperatures in natural samples due to spinel subsolidus re-equilibration, whereas the empirical models (independent of Fe and Mg in spinel) are less sensitive to re-equilibration but yield temperatures with larger uncertainties. We applied a statistical test to select the most appropriate model for application to natural samples. When applied to lavas from mid-ocean ridges, Iceland, Skye, Emeishan, Etendeka, and Tortugal, our new temperature estimates are 30–100 °C lower than previously proposed. The lower temperature estimates cause a lower mantle melting temperature and significant impacts on the mantle lithology constraints.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136063359","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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