J. Gilotti, W. McClelland, S. Schorn, R. Compagnoni, M. Coble
Abstract. An eclogite-facies orthogneiss and host paragneiss from a quarry near Tavagnasco in the Lower Aosta Valley were studied in order to refine the protolith, provenance and metamorphic ages of the Eclogitic Micaschist Complex of the Sesia Zone. The orthogneiss contains jadeite with quartz + phengite + K-feldspar ± garnet + rutile + zircon, whereas the paragneiss hosts garnet + jadeite + phengite ± glaucophane + epidote + rutile + quartz. Phase diagram modeling of two representative samples yields minimum equilibration conditions of 550 ± 50 ∘C and 18 ± 2 kbar. Cathodoluminescence images of zircon from the orthogneiss show oscillatory-zoned cores that are embayed and overgrown by complex, oscillatory-zoned rims. Four concordant secondary ion mass spectrometry analyses from the cores give a weighted mean 206Pb / 238U age of 457 ± 5 Ma. The cores have Th/U = 0.1 and negative Eu anomalies indicative of an igneous protolith, which we interpret to have crystallized in the Ordovician at 780 ∘C, based on Ti-in-zircon measurements. Zircon rims yield a range of 206Pb / 238U dates from 74 to 86 Ma, and four concordant analyses define a weighted mean 206Pb / 238U age of 78 ± 2 Ma. The rims are interpreted to have grown in the eclogite facies based on their lower Th/U (0.01), less negative Eu anomalies and steeper heavy rare earth element (HREE) patterns at <600 ∘C. The paragneiss yielded a detrital zircon population with major peaks at 575–600, 655 and 765 Ma; minor older components; and a maximum depositional age of approximately 570 Ma. The prominent Neoproterozoic zircon population and Ediacaran depositional age suggest derivation from the Gondwana margin. The metamorphic zircon is consistent with the oldest eclogite-facies event in the Sesia Zone; it does not show evidence of multiple periods of rim growth or any pre-Alpine (e.g., Variscan) metamorphism.
{"title":"Provenance, protolith and metamorphic ages of jadeite-bearing orthogneiss and host paragneiss at Tavagnasco, the Sesia Zone, Lower Aosta Valley, Italy","authors":"J. Gilotti, W. McClelland, S. Schorn, R. Compagnoni, M. Coble","doi":"10.5194/ejm-35-645-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-645-2023","url":null,"abstract":"Abstract. An eclogite-facies orthogneiss and host paragneiss from a quarry\u0000near Tavagnasco in the Lower Aosta Valley were studied in order to refine\u0000the protolith, provenance and metamorphic ages of the Eclogitic Micaschist\u0000Complex of the Sesia Zone. The orthogneiss contains jadeite with quartz + phengite + K-feldspar ± garnet + rutile + zircon, whereas the\u0000paragneiss hosts garnet + jadeite + phengite ± glaucophane + epidote + rutile + quartz. Phase diagram modeling of two representative\u0000samples yields minimum equilibration conditions of 550 ± 50 ∘C and 18 ± 2 kbar. Cathodoluminescence images of zircon from the\u0000orthogneiss show oscillatory-zoned cores that are embayed and overgrown by\u0000complex, oscillatory-zoned rims. Four concordant secondary ion mass\u0000spectrometry analyses from the cores give a weighted mean\u0000206Pb / 238U age of 457 ± 5 Ma. The cores have Th/U = 0.1\u0000and negative Eu anomalies indicative of an igneous protolith, which we\u0000interpret to have crystallized in the Ordovician at 780 ∘C, based\u0000on Ti-in-zircon measurements. Zircon rims yield a range of\u0000206Pb / 238U dates from 74 to 86 Ma, and four concordant analyses\u0000define a weighted mean 206Pb / 238U age of 78 ± 2 Ma. The rims\u0000are interpreted to have grown in the eclogite facies based on their lower\u0000Th/U (0.01), less negative Eu anomalies and steeper heavy rare\u0000earth element (HREE) patterns at <600 ∘C. The paragneiss yielded a detrital zircon population with\u0000major peaks at 575–600, 655 and 765 Ma; minor older components; and a\u0000maximum depositional age of approximately 570 Ma. The prominent\u0000Neoproterozoic zircon population and Ediacaran depositional age suggest\u0000derivation from the Gondwana margin. The metamorphic zircon is consistent\u0000with the oldest eclogite-facies event in the Sesia Zone; it does not show\u0000evidence of multiple periods of rim growth or any pre-Alpine (e.g.,\u0000Variscan) metamorphism.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43364377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Grey, E. Keck, A. R. Kampf, C. MacRae, R. Gable, W. G. Mumme, N. Wilson, A. Glenn, C. Davidson
Abstract. Hochleitnerite, [K(H2O)]Mn2(Ti2Fe)(PO4)4O2(H2O)10 ⋅ 4H2O, is a new paulkerrite-group mineral from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with fluorapatite, rockbridgeite, columbite and sub-micrometre rods of uranophane. Hochleitnerite occurs as isolated and intergrown pale-yellow, diamond-shaped tablets with thicknesses reaching 50 µm and lengths of 120 µm. The crystals are flattened on {010}, slightly elongated on [001], and bounded by the {111} and {010} forms. The calculated density is 2.40 g cm−3. Optically, hochleitnerite crystals are biaxial (+), with α= 1.615(2), β= 1.621(2) and γ= 1.645(2) (measured in white light). The calculated 2V is 53.8∘. The empirical formula is [K(H2O)](Mn1.512+Fe0.492+)Σ2.00(Ti1.624+Fe0.193+Al0.15)Σ2.96(PO4)4.00[O1.50F0.23(OH)0.27]Σ2.00(H2O)10 ⋅ 4H2O. Hochleitnerite has space group Pbca and unit-cell parameters a= 10.5513(3) Å, b= 20.6855(17) Å, c= 12.4575(4) Å, V= 2718.96(15) Å3 and Z= 4. The crystal structure was refined using single-crystal data to wRobs= 0.082 for 2242 reflections with I > 3σ(I). The crystal structure contains corner-connected linear trimers of Ti-centred octahedra that share corners with PO4 tetrahedra to form 10-member rings parallel to (010). K+ cations and water molecules are located within the rings. Additional corner sharing of the PO4 tetrahedra with MnO2(H2O)4 octahedra occurs along [010] to complete the 3D framework structure.
{"title":"Hochleitnerite, [K(H2O)]Mn2(Ti2Fe)(PO4)4O2(H2O)10 ⋅ 4H2O, a new paulkerrite-group mineral, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany","authors":"I. Grey, E. Keck, A. R. Kampf, C. MacRae, R. Gable, W. G. Mumme, N. Wilson, A. Glenn, C. Davidson","doi":"10.5194/ejm-35-635-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-635-2023","url":null,"abstract":"Abstract. Hochleitnerite,\u0000[K(H2O)]Mn2(Ti2Fe)(PO4)4O2(H2O)10 ⋅ 4H2O, is a new paulkerrite-group mineral from the Hagendorf-Süd\u0000pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered\u0000zwieselite, in association with fluorapatite, rockbridgeite, columbite and\u0000sub-micrometre rods of uranophane. Hochleitnerite occurs as isolated and\u0000intergrown pale-yellow, diamond-shaped tablets with thicknesses reaching 50 µm and lengths of 120 µm. The crystals are flattened on\u0000{010}, slightly elongated on [001], and bounded\u0000by the {111} and {010} forms. The calculated density is\u00002.40 g cm−3. Optically, hochleitnerite crystals are biaxial\u0000(+), with α= 1.615(2), β= 1.621(2) and γ= 1.645(2) (measured in white light). The calculated 2V is 53.8∘.\u0000The empirical formula is\u0000[K(H2O)](Mn1.512+Fe0.492+)Σ2.00(Ti1.624+Fe0.193+Al0.15)Σ2.96(PO4)4.00[O1.50F0.23(OH)0.27]Σ2.00(H2O)10 ⋅ 4H2O. Hochleitnerite has space\u0000group Pbca and unit-cell parameters a= 10.5513(3) Å, b= 20.6855(17) Å,\u0000c= 12.4575(4) Å, V= 2718.96(15) Å3 and Z= 4. The crystal\u0000structure was refined using single-crystal data to wRobs= 0.082 for\u00002242 reflections with I > 3σ(I). The crystal structure\u0000contains corner-connected linear trimers of Ti-centred octahedra that share\u0000corners with PO4 tetrahedra to form 10-member rings parallel to (010).\u0000K+ cations and water molecules are located within the rings. Additional\u0000corner sharing of the PO4 tetrahedra with MnO2(H2O)4\u0000octahedra occurs along [010] to complete the 3D framework structure.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46729512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The high-pressure metagranite of La Picherais belongs to the Cellier Unit (part of the lower allochthon of the Champtoceaux Complex; Armorican Massif, western France), where it crops out as an undeformed body embedded within the orthogneisses of the Cellier Unit and is closely associated with numerous mafic eclogite lenses and seldom metahornfels. The petrographic observations of this metagranite reveal the presence of well-developed reaction textures: (1) pseudomorph after plagioclase, (2) garnet and phengite coronae at biotite–plagioclase interfaces, (3) garnet and phengite coronae at biotite–K-feldspar interfaces, and (4) garnet and rutile coronae at ilmenite–plagioclase interfaces, attesting that it underwent high-pressure and low-temperature conditions after the granite intrusion and its cooling. The analysis of the coronae and of a xenolith inclusion found in this granite points to pressure (P) and temperature (T) estimates of P>1.7 GPa and T=600–650 ∘C for the peak of metamorphism. P–T estimates performed on the mafic eclogite collected in the vicinity of the metagranite give values of 2.0–2.2 GPa and 640–680 ∘C, in good agreement with previous estimates made in other places within the Cellier Unit. The La Picherais metagranite is a key example of undeformed high-pressure metagranite allowing the study of the reactivity and degree of transformation of quartzofeldspathic rocks during subduction and constitutes a Variscan equivalent of the Alpine Monte Mucrone or Brossasco–Isasca metagranitoids.
{"title":"Petrological study of an eclogite-facies metagranite from the Champtoceaux Complex (La Picherais, Armorican Massif, France)","authors":"Thomas Gyomlai, P. Yamato, G. Godard","doi":"10.5194/ejm-35-589-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-589-2023","url":null,"abstract":"Abstract. The high-pressure metagranite of La Picherais\u0000belongs to the Cellier Unit (part of the lower allochthon of the\u0000Champtoceaux Complex; Armorican Massif, western France), where it crops out\u0000as an undeformed body embedded within the orthogneisses of the Cellier Unit\u0000and is closely associated with numerous mafic eclogite lenses and seldom\u0000metahornfels. The petrographic observations of this metagranite reveal the\u0000presence of well-developed reaction textures: (1) pseudomorph after\u0000plagioclase, (2) garnet and phengite coronae at biotite–plagioclase\u0000interfaces, (3) garnet and phengite coronae at biotite–K-feldspar interfaces,\u0000and (4) garnet and rutile coronae at ilmenite–plagioclase interfaces,\u0000attesting that it underwent high-pressure and low-temperature conditions\u0000after the granite intrusion and its cooling. The analysis of the coronae and\u0000of a xenolith inclusion found in this granite points to pressure (P) and\u0000temperature (T) estimates of P>1.7 GPa and T=600–650 ∘C for the peak of metamorphism. P–T estimates performed on\u0000the mafic eclogite collected in the vicinity of the metagranite give values\u0000of 2.0–2.2 GPa and 640–680 ∘C, in good agreement with previous\u0000estimates made in other places within the Cellier Unit. The La Picherais metagranite is a key example of undeformed high-pressure metagranite allowing the study of the reactivity and degree of transformation of\u0000quartzofeldspathic rocks during subduction and constitutes a Variscan\u0000equivalent of the Alpine Monte Mucrone or Brossasco–Isasca metagranitoids.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42484621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The injection of mafic magma into a hydrous felsic magma chamber is a potential trigger mechanism for bimodal explosive volcanism. As H2O is the most abundant volatile component in magmas, the interaction and the degassing behavior of mildly peralkaline hydrous rhyolitic melt in contact with hydrous basaltic melt were investigated by decompression experiments. Preparatory hydration experiments and bimodal magma decompression experiments, as well as reference experiments, were carried out in an internally heated argon pressure vessel. Pre-hydrated rhyolite and basalt cylinders were perfectly contacted together in a precious-metal capsule, heated to 1348 K at 210 MPa, and thermally equilibrated for 10 min. The initial sample properties were determined by a bimodal reference experiment, quenched immediately after equilibration. To simulate the magma ascent, three bimodal samples and a decompression experiment with two contacted rhyolite cylinders for testing the experimental setup were decompressed with 0.17 or 1.7 MPa s−1 to the final pressure of 100 MPa and then quenched. All decompression experiments resulted in vesiculated samples. The H2O vesicles observed in the decompressed sample of the monomodal rhyolite–rhyolite reference experiment are homogeneously distributed throughout the sample. The former interface between the contacted glass cylinders is invisible after decompression and quench. This reference experiment proves that the two-cylinder design does not influence the degassing behavior of the hydrous melt, e.g., an increased formation of vesicles at possible nucleation sites at the contact plane of the cylinders. The undecompressed bimodal rhyolite–basalt sample shows crystal-free rhyolitic glass, whereas 3 µm sized idiomorphic magnetite crystals coexist with glass in the basaltic part of the sample. Within the 10 min run time, a ∼ 300 µm wide hybrid composition zone developed between the hydrous rhyolitic and basaltic endmembers, caused by diffusion-induced mixing processes. Decompression and quenching of the bimodal melts resulted in vesiculated glass samples. A ∼ 100 µm wide zone of alkali-depleted rhyolitic glass as part of the ∼ 300–560 µm wide hybrid zone is covered with an enhanced number of H2O vesicles compared to the pristine rhyolitic and basaltic glass volumes. We suggest that this enhanced vesiculated zone forms by a rapid diffusional loss of alkalis from the mildly peralkaline rhyolitic melt into the basaltic melt of the sample. The reduced alkali concentration significantly reduces the H2O solubility of the rhyolitic melt. This process enhances the H2O supersaturation necessary for vesicle formation during decompression. In summary, the new findings imply that convective magma ascent driven by the injection of hot basaltic magma into a hydrous peralkaline rhyolitic melt reservoir leads to enhanced H2O vesicle formation near the melt interface and thus to efficient degassing. This in turn can accelerate buoyancy-
{"title":"H2O degassing triggered by alkali depletion in bimodal magma injection processes – a new experimental approach","authors":"Patricia Louisa Marks, A. Allabar, M. Nowak","doi":"10.5194/ejm-35-613-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-613-2023","url":null,"abstract":"Abstract. The injection of mafic magma into a hydrous felsic magma chamber is a\u0000potential trigger mechanism for bimodal explosive volcanism. As H2O is\u0000the most abundant volatile component in magmas, the interaction and the\u0000degassing behavior of mildly peralkaline hydrous rhyolitic melt in contact\u0000with hydrous basaltic melt were investigated by decompression experiments.\u0000Preparatory hydration experiments and bimodal magma decompression\u0000experiments, as well as reference experiments, were carried out in an\u0000internally heated argon pressure vessel. Pre-hydrated rhyolite and\u0000basalt cylinders were perfectly contacted together in a precious-metal\u0000capsule, heated to 1348 K at 210 MPa, and thermally equilibrated for 10 min.\u0000The initial sample properties were determined by a bimodal reference\u0000experiment, quenched immediately after equilibration. To simulate the magma\u0000ascent, three bimodal samples and a decompression experiment with two\u0000contacted rhyolite cylinders for testing the experimental setup were\u0000decompressed with 0.17 or 1.7 MPa s−1 to the final pressure of 100 MPa and then quenched. All decompression experiments resulted in vesiculated samples. The H2O\u0000vesicles observed in the decompressed sample of the monomodal\u0000rhyolite–rhyolite reference experiment are homogeneously distributed\u0000throughout the sample. The former interface between the contacted glass\u0000cylinders is invisible after decompression and quench. This reference\u0000experiment proves that the two-cylinder design does not influence the\u0000degassing behavior of the hydrous melt, e.g., an increased formation of\u0000vesicles at possible nucleation sites at the contact plane of the cylinders. The undecompressed bimodal rhyolite–basalt sample shows crystal-free\u0000rhyolitic glass, whereas 3 µm sized idiomorphic magnetite crystals\u0000coexist with glass in the basaltic part of the sample. Within the 10 min run\u0000time, a ∼ 300 µm wide hybrid composition zone developed\u0000between the hydrous rhyolitic and basaltic endmembers, caused by\u0000diffusion-induced mixing processes. Decompression and quenching of the bimodal melts resulted in vesiculated\u0000glass samples. A ∼ 100 µm wide zone of alkali-depleted\u0000rhyolitic glass as part of the ∼ 300–560 µm wide\u0000hybrid zone is covered with an enhanced number of H2O vesicles\u0000compared to the pristine rhyolitic and basaltic glass volumes. We suggest\u0000that this enhanced vesiculated zone forms by a rapid diffusional loss of\u0000alkalis from the mildly peralkaline rhyolitic melt into the basaltic melt of\u0000the sample. The reduced alkali concentration significantly reduces the\u0000H2O solubility of the rhyolitic melt. This process enhances the\u0000H2O supersaturation necessary for vesicle formation during\u0000decompression. In summary, the new findings imply that convective magma ascent driven by\u0000the injection of hot basaltic magma into a hydrous peralkaline rhyolitic\u0000melt reservoir leads to enhanced H2O vesicle formation near the melt\u0000interface and thus to efficient degassing. This in turn can accelerate\u0000buoyancy-","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45979429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Corundum- and spinel-bearing symplectites after muscovite were found in ultrahigh-pressure (UHP) eclogites from the Dabie terrane, China. Three types of symplectites were recognized based on their mineral assemblages: (1) symplectitic intergrowths of corundum + plagioclase + biotite after phengite (CPB), (2) symplectitic intergrowths of spinel + plagioclase + biotite after phengite (SPB), and (3) symplectitic intergrowths of spinel + plagioclase after paragonite (SP). The microtextures and mineral assemblages of the symplectites, in combination with the results of thermodynamic modeling on local regions, indicate that these symplectites formed by the breakdown of phengite and paragonite during the granulite-facies metamorphic overprint (770–850 ∘C) of the eclogite at pressures of 0.8–0.9 GPa. Dehydration partial melting reactions occurred during the breakdown of muscovite, which leads to the formation of thin plagioclase films (silicate melts) along grain (garnet, rutile, quartz) boundaries. Mass balance calculations indicate that the development of CPB and SPB symplectites after phengite requires the introduction of Al, Ca, Na, and Fe and loss of Si, Mg, and K. However, the formation of SP symplectites after paragonite requires the input of Mg, Ca, and Fe and removal of Si, Al, and Na. By summarizing the occurrence and growth mechanism of corundum- and spinel-bearing symplectites in global UHP terranes, we find that such symplectites can form by both the subsolidus replacement of an Al-rich anhydrous mineral (kyanite) and the dehydration melting of an Al-rich hydrous phase during high-temperature metamorphism. This study reveals that muscovite-bearing eclogites may experience multiple episodes of partial melting during the slab exhumation, not only at the high-pressure (HP) exhumation stage but also at the lower-pressure metamorphic overprinting stage. Kyanite is a reaction product during the HP partial melting, whereas the low-pressure (LP) melting will consume kyanite. We propose that the occurrence of corundum- and spinel-bearing symplectites after muscovite in eclogites is a potential mineralogical indicator of LP melting in exhumed slabs.
{"title":"Corundum-bearing and spinel-bearing symplectites in ultrahigh-pressure eclogites record high-temperature overprint and partial melting during slab exhumation","authors":"Pan Tang, Shun Guo","doi":"10.5194/ejm-35-569-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-569-2023","url":null,"abstract":"Abstract. Corundum- and spinel-bearing symplectites after muscovite were found in\u0000ultrahigh-pressure (UHP) eclogites from the Dabie terrane, China. Three\u0000types of symplectites were recognized based on their mineral assemblages:\u0000(1) symplectitic intergrowths of corundum + plagioclase + biotite after\u0000phengite (CPB), (2) symplectitic intergrowths of spinel + plagioclase +\u0000biotite after phengite (SPB), and (3) symplectitic intergrowths of spinel\u0000+ plagioclase after paragonite (SP). The microtextures and mineral\u0000assemblages of the symplectites, in combination with the results of\u0000thermodynamic modeling on local regions, indicate that these symplectites\u0000formed by the breakdown of phengite and paragonite during the granulite-facies metamorphic overprint (770–850 ∘C) of the eclogite at pressures\u0000of 0.8–0.9 GPa. Dehydration partial melting reactions occurred during the\u0000breakdown of muscovite, which leads to the formation of thin plagioclase\u0000films (silicate melts) along grain (garnet, rutile, quartz) boundaries. Mass\u0000balance calculations indicate that the development of CPB and SPB\u0000symplectites after phengite requires the introduction of Al, Ca, Na, and Fe\u0000and loss of Si, Mg, and K. However, the formation of SP symplectites after\u0000paragonite requires the input of Mg, Ca, and Fe and removal of Si, Al, and\u0000Na. By summarizing the occurrence and growth mechanism of\u0000corundum- and spinel-bearing symplectites in global UHP terranes, we find that\u0000such symplectites can form by both the subsolidus replacement of an Al-rich\u0000anhydrous mineral (kyanite) and the dehydration melting of an Al-rich\u0000hydrous phase during high-temperature metamorphism. This study reveals that\u0000muscovite-bearing eclogites may experience multiple episodes of partial\u0000melting during the slab exhumation, not only at the high-pressure (HP)\u0000exhumation stage but also at the lower-pressure metamorphic overprinting stage.\u0000Kyanite is a reaction product during the HP partial melting, whereas the\u0000low-pressure (LP) melting will consume kyanite. We propose that the\u0000occurrence of corundum- and spinel-bearing symplectites after muscovite in\u0000eclogites is a potential mineralogical indicator of LP melting in exhumed\u0000slabs.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48391849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Bolfan-Casanova, L. Martinek, G. Manthilake, M. Verdier-Paoletti, P. Chauvigne
Abstract. This study aims to experimentally constrain the water storage capacities of olivine and wadsleyite at a depth near 410 km (12–14 GPa) under water-saturated conditions, as a function of temperature, oxygen fugacity, and the presence of carbon (molar H / C of 2). Experiments have been conducted in the multi-anvil press, with sealed double capsules to preserve fluids, at 1200 to 1400 ∘C and three different oxygen fugacities fixed at the rhenium–rhenium oxide buffer (RRO), nickel–nickel oxide buffer (NNO), and iron-wüstite (IW) for oxidizing, intermediate, and reducing conditions, respectively. The water contents of minerals were measured by Raman spectroscopy that allows a very small beam size to be used and were cross-checked on a few samples with NanoSIMS analyses. We observe an effect, although slight, of fO2 on the water storage capacity of both wadsleyite and olivine and also on their solidus temperatures. At 1200 ∘C, the storage capacity of the nominally anhydrous minerals (NAMS) increases with increasing oxygen fugacity (from the IW to the RRO buffer) from 1 wt % to 1.5 wt % H2O in wadsleyite and from 0.1 wt % to 0.2 wt % in olivine, owing to the increase in H2O / H2 speciation in the fluid, whereas at 1400 ∘C the storage capacity decreases from 1 wt % to 0.75 wt % H2O in wadsleyite and down to 0.03 wt % for olivine. At high temperature, the water storage capacity is lowered due to melting, and the more oxidized the conditions are the more the solidus is depressed. Still, at 1400 ∘C and IW, wadsleyite can store substantial amounts of water: 0.8 wt % to 1 wt % H2O. The effect of carbon is to decrease water storage capacity in both wadsleyite and olivine by an average factor 2 at 1300–1400 ∘C. The trends in water storage as a function of fO2 and C presence are confirmed by NanoSIMS measurements. The solidus at IW without C is located between 1300 and 1400 ∘C in the wadsleyite stability field and drops to temperatures below 1300 ∘C in the olivine stability field. With the addition of C, the solidus is found between 1200 and 1300 ∘C in both olivine and wadsleyite stability fields.
{"title":"Effect of oxygen fugacity on the storage of water in wadsleyite and olivine in H and H–C fluids and implications for melting atop the transition zone","authors":"N. Bolfan-Casanova, L. Martinek, G. Manthilake, M. Verdier-Paoletti, P. Chauvigne","doi":"10.5194/ejm-35-549-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-549-2023","url":null,"abstract":"Abstract. This study aims to experimentally constrain the water storage capacities of\u0000olivine and wadsleyite at a depth near 410 km (12–14 GPa) under\u0000water-saturated conditions, as a function of temperature, oxygen fugacity,\u0000and the presence of carbon (molar H / C of 2). Experiments have been conducted\u0000in the multi-anvil press, with sealed double capsules to preserve fluids, at\u00001200 to 1400 ∘C and three different oxygen fugacities fixed at the\u0000rhenium–rhenium oxide buffer (RRO), nickel–nickel oxide buffer (NNO), and\u0000iron-wüstite (IW) for oxidizing, intermediate, and reducing conditions,\u0000respectively. The water contents of minerals were measured by Raman\u0000spectroscopy that allows a very small beam size to be used and were\u0000cross-checked on a few samples with NanoSIMS analyses. We observe an effect, although slight, of fO2 on the water storage\u0000capacity of both wadsleyite and olivine and also on their solidus\u0000temperatures. At 1200 ∘C, the storage capacity of the nominally anhydrous\u0000minerals (NAMS)\u0000increases with increasing oxygen fugacity (from the IW to the RRO buffer)\u0000from 1 wt % to 1.5 wt % H2O in wadsleyite and from 0.1 wt % to 0.2 wt % in olivine, owing to the increase in H2O / H2 speciation in\u0000the fluid, whereas at 1400 ∘C the storage capacity decreases from\u00001 wt % to 0.75 wt % H2O in wadsleyite and down to 0.03 wt % for\u0000olivine. At high temperature, the water storage capacity is lowered due to\u0000melting, and the more oxidized the conditions are the more the solidus is\u0000depressed. Still, at 1400 ∘C and IW, wadsleyite can store\u0000substantial amounts of water: 0.8 wt % to 1 wt % H2O. The effect of carbon is\u0000to decrease water storage capacity in both wadsleyite and olivine by an\u0000average factor 2 at 1300–1400 ∘C. The trends in water storage as a\u0000function of fO2 and C presence are confirmed by NanoSIMS measurements.\u0000The solidus at IW without C is located between 1300 and 1400 ∘C in\u0000the wadsleyite stability field and drops to temperatures below 1300 ∘C in the olivine stability field. With the addition of C, the\u0000solidus is found between 1200 and 1300 ∘C in both olivine and\u0000wadsleyite stability fields.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47140868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The past 40 years have been a golden age for eclogite studies, supported by an ever wider range of instrumentation and enhanced computational capabilities, linked with ongoing developments in thermobarometry and geochronology. During this time, we have made robust estimates of pressure–temperature (P–T) conditions; determined ages related to the prograde, metamorphic peak and retrograde stages; and calculated time-integrated rates of cooling and exhumation for eclogites and related rocks, including blueschists, from orogenic belts worldwide. Improvements to single mineral thermometers and new developments in elastic barometry using inclusions of one mineral in another (e.g. quartz and/or zircon in garnet), coupled with ongoing innovations in petrochronology and diffusion modelling, presage a new age for eclogite studies in which detailed quantification of metamorphic conditions and timescales will be linked to an improved understanding of processes at all scales. Since the turn of the century, numerical modelling of subduction zone and rock exhumation processes has become increasingly important. As a result, subduction and exhumation are quite well understood, but the volume of continental crust subducted to and returned from mantle conditions and the amount lost to the mantle are largely unknown. We have generated sufficient data to investigate the spatiotemporal distribution of metamorphism and secular change but not without controversy in relation to the rare occurrence of orogenic eclogites and the absence of blueschists prior to the late Neoproterozoic and the emergence of plate tectonics on Earth. Since the turn of the century, the assumption that metamorphic pressure is lithostatic has come under increasing scrutiny. Whether local variations in stress extrapolate to the crustal scale and, if so, whether the magnitude of the calculated deviations from lithostatic pressure can be generated and sustained in mechanically heterogeneous rock units remains contentious. Could the paradigm of subduction of continental lithosphere to mantle depths be simply an artefact of the lithostatic assumption? Fluid cycling in subduction zones and understanding the role of fluids in the generation of intermediate-depth earthquakes remain important topics of current research. Dry (H2O-absent) conditions are unlikely around the peak of ultrahigh-pressure (UHP) metamorphism or during exhumation, due to dehydroxylation of nominally anhydrous minerals and breakdown of hydrous minerals at P–T conditions in the realm of supercritical fluid and hydrous melt. Indeed, the presence of melt may be necessary to facilitate the exhumation of HP and UHP tectonometamorphic rock units. Finally, our ability to interrogate inclusions in superdeep diamonds should lead to a better understanding of how the deep interior and surface are linked in the context of Earth as a fully coupled system.
{"title":"Some thoughts about eclogites and related rocks","authors":"Michael Brown","doi":"10.5194/ejm-35-523-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-523-2023","url":null,"abstract":"Abstract. The past 40 years have been a golden age for eclogite\u0000studies, supported by an ever wider range of instrumentation and enhanced\u0000computational capabilities, linked with ongoing developments in\u0000thermobarometry and geochronology. During this time, we have made robust\u0000estimates of pressure–temperature (P–T) conditions; determined ages related to\u0000the prograde, metamorphic peak and retrograde stages; and calculated time-integrated rates of cooling and exhumation for eclogites and related rocks,\u0000including blueschists, from orogenic belts worldwide. Improvements to single\u0000mineral thermometers and new developments in elastic barometry using\u0000inclusions of one mineral in another (e.g. quartz and/or zircon in garnet),\u0000coupled with ongoing innovations in petrochronology and diffusion modelling,\u0000presage a new age for eclogite studies in which detailed quantification of\u0000metamorphic conditions and timescales will be linked to an improved\u0000understanding of processes at all scales. Since the turn of the century,\u0000numerical modelling of subduction zone and rock exhumation processes has\u0000become increasingly important. As a result, subduction and exhumation are\u0000quite well understood, but the volume of continental crust subducted to and\u0000returned from mantle conditions and the amount lost to the mantle are\u0000largely unknown. We have generated sufficient data to investigate the\u0000spatiotemporal distribution of metamorphism and secular change but not\u0000without controversy in relation to the rare occurrence of orogenic eclogites\u0000and the absence of blueschists prior to the late Neoproterozoic and the\u0000emergence of plate tectonics on Earth. Since the turn of the century, the\u0000assumption that metamorphic pressure is lithostatic has come under\u0000increasing scrutiny. Whether local variations in stress extrapolate to the\u0000crustal scale and, if so, whether the magnitude of the calculated deviations\u0000from lithostatic pressure can be generated and sustained in mechanically\u0000heterogeneous rock units remains contentious. Could the paradigm of\u0000subduction of continental lithosphere to mantle depths be simply an artefact\u0000of the lithostatic assumption? Fluid cycling in subduction zones and\u0000understanding the role of fluids in the generation of intermediate-depth\u0000earthquakes remain important topics of current research. Dry (H2O-absent) conditions are unlikely around the peak of ultrahigh-pressure (UHP) metamorphism or\u0000during exhumation, due to dehydroxylation of nominally anhydrous minerals\u0000and breakdown of hydrous minerals at P–T conditions in the realm of\u0000supercritical fluid and hydrous melt. Indeed, the presence of melt may be\u0000necessary to facilitate the exhumation of HP and UHP tectonometamorphic\u0000rock units. Finally, our ability to interrogate inclusions in superdeep\u0000diamonds should lead to a better understanding of how the deep interior and\u0000surface are linked in the context of Earth as a fully coupled system.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45898429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Metamorphic pressure and temperature (P–T) paths in late-Archean high-grade rocks of the eastern Beartooth Mountains of Montana (USA), a portion of the Wyoming Province, are established by a combination of imaging, analytical, and modeling approaches. Garnet inclusion mechanical and chemical thermobarometry, applied to several granulite-facies migmatites and an iron formation, is particularly useful in constraining the prograde P–T conditions. Quartz-in-garnet (QuiG) elastic Raman barometry was used on quartz inclusions in garnet for all samples studied. For a smaller subset of four representative samples, QuiG constraints were used in conjunction with Ti-in-quartz (TitaniQ) and Ti-in-biotite (TiB) thermometry to establish unique prograde inclusion entrapment P–T conditions. Ti measurements of garnet hosts and cathodoluminescence (CL) imagery of inclusion and matrix quartz grains were employed to check for Ti loss/diffusion. Lastly, inclusion studies were supplemented with thermodynamic modeling and matrix chemical thermobarometry to examine garnet nucleation temperatures and peak metamorphic conditions. Disagreement between the volume strain and elastic tensor methods used to calculate quartz inclusion pressures implies that quartz inclusions studied are under strong differential strain. Prograde entrapment results from the two inclusion thermobarometry pairs used are distinct: 0.55–0.70 GPa and 475–580 ∘C (QuiG–TitaniQ) versus 0.85–1.10 GPa and 665–780 ∘C (QuiG–TiB). Garnet modal isopleth modeling indicates that the majority of garnet growth occurred at ∼ 450–600 ∘C, implying that P–T conditions of garnet growth are interpreted to be most reliably represented by QuiG–TitaniQ inclusion thermobarometry. Normal distributions of calculated QuiG inclusion pressures and the concentration of mineral inclusions in garnet cores suggest that the majority of garnet inclusions were entrapped during a single stage of porphyroblast growth. A general lack of evidence from CL imagery for post-entrapment mechanical or chemical modifications to quartz inclusions suggests that quartz inclusions used to calculate entrapment P–T largely preserve their initial entrapment conditions. Biotite inclusions preserve higher temperatures than quartz inclusions in the same garnets, likely due to Fe–Mg exchange with garnet hosts that allowed Ti content of biotite to change after entrapment. Pseudosection modeling and matrix chemical thermobarometry of multiple, independent lithologies examined during inclusion studies suggest a range of peak granulite facies conditions of ∼ 0.50–0.70 GPa and 730–800 ∘C. Peak metamorphic P–T modeling work from this study, together with evidence of regional amphibolite facies overprinting in immediately adjacent samples, indicates an overall clockwise metamorphic P–T path with nearly isobaric prograde heating to peak temperatures. Interpreted P–T path reconstructions are consistent with metamorphism developed in a more modern-style co
{"title":"Metamorphic P–T paths of Archean granulite facies metasedimentary lithologies from the eastern Beartooth Mountains of the northern Wyoming Province, Montana, USA: constraints from quartz-in-garnet (QuiG) Raman elastic barometry, geothermobarometry, and thermodynamic modeling","authors":"L. Tuttle, D. Henry","doi":"10.5194/ejm-35-499-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-499-2023","url":null,"abstract":"Abstract. Metamorphic pressure and temperature (P–T) paths in late-Archean\u0000high-grade rocks of the eastern Beartooth Mountains of Montana (USA), a\u0000portion of the Wyoming Province, are established by a combination of\u0000imaging, analytical, and modeling approaches. Garnet inclusion mechanical\u0000and chemical thermobarometry, applied to several granulite-facies migmatites\u0000and an iron formation, is particularly useful in constraining the prograde\u0000P–T conditions. Quartz-in-garnet (QuiG) elastic Raman barometry was used on\u0000quartz inclusions in garnet for all samples studied. For a smaller subset of\u0000four representative samples, QuiG constraints were used in conjunction with\u0000Ti-in-quartz (TitaniQ) and Ti-in-biotite (TiB) thermometry to establish\u0000unique prograde inclusion entrapment P–T conditions. Ti measurements of\u0000garnet hosts and cathodoluminescence (CL) imagery of inclusion and matrix\u0000quartz grains were employed to check for Ti loss/diffusion. Lastly,\u0000inclusion studies were supplemented with thermodynamic modeling and matrix\u0000chemical thermobarometry to examine garnet nucleation temperatures and peak\u0000metamorphic conditions. Disagreement between the volume strain and elastic tensor methods used to\u0000calculate quartz inclusion pressures implies that quartz inclusions studied\u0000are under strong differential strain. Prograde entrapment results from the\u0000two inclusion thermobarometry pairs used are distinct: 0.55–0.70 GPa and\u0000475–580 ∘C (QuiG–TitaniQ) versus 0.85–1.10 GPa and 665–780 ∘C (QuiG–TiB). Garnet modal isopleth modeling indicates that the\u0000majority of garnet growth occurred at ∼ 450–600 ∘C,\u0000implying that P–T conditions of garnet growth are interpreted to be most\u0000reliably represented by QuiG–TitaniQ inclusion thermobarometry. Normal\u0000distributions of calculated QuiG inclusion pressures and the concentration\u0000of mineral inclusions in garnet cores suggest that the majority of garnet\u0000inclusions were entrapped during a single stage of porphyroblast growth. A\u0000general lack of evidence from CL imagery for post-entrapment mechanical or\u0000chemical modifications to quartz inclusions suggests that quartz inclusions\u0000used to calculate entrapment P–T largely preserve their initial entrapment\u0000conditions. Biotite inclusions preserve higher temperatures than quartz\u0000inclusions in the same garnets, likely due to Fe–Mg exchange with garnet\u0000hosts that allowed Ti content of biotite to change after entrapment.\u0000Pseudosection modeling and matrix chemical thermobarometry of multiple,\u0000independent lithologies examined during inclusion studies suggest a range of\u0000peak granulite facies conditions of ∼ 0.50–0.70 GPa and\u0000730–800 ∘C. Peak metamorphic P–T modeling work from this study,\u0000together with evidence of regional amphibolite facies overprinting in\u0000immediately adjacent samples, indicates an overall clockwise metamorphic P–T\u0000path with nearly isobaric prograde heating to peak temperatures. Interpreted\u0000P–T path reconstructions are consistent with metamorphism developed in a\u0000more modern-style co","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48880543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Schönig, Carsten Benner, G. Meinhold, H. von Eynatten, N. K. Lünsdorf
Abstract. Modern-style plate tectonics is characterised by the global operation of cold and deep subduction involving blueschist facies and ultrahigh-pressure metamorphism. This has been a common process since the Neoproterozoic, but a couple of studies indicate similar processes were active in the Paleoproterozoic, at least on the local scale. Particularly conspicuous are extreme ultrahigh-pressure conditions of ∼ 7 GPa at thermal gradients < 150 ∘C GPa−1 proposed for metamorphic rocks of the Nordre Strømfjord shear zone in the western part of the Paleoproterozoic Nagssugtoqidian Orogen of Greenland. By acquiring a large dataset of heavy minerals (n = 52 130) and garnet major-element composition integrated with mineral inclusion analysis (n=2669) from modern sands representing fresh and naturally mixed erosional material from the metamorphic rocks, we here intensely screened the area for potential occurrences of ultrahigh-pressure rocks and put constraints on the metamorphic evolution. Apart from the absence of any indications pointing to ultrahigh-pressure and low-temperature–high-pressure metamorphism, the results are well in accordance with a common Paleoproterozoic subduction–collision metamorphic evolution along a Barrovian-type intermediate temperature and pressure gradient with a pressure peak at the amphibolite–granulite–eclogite-facies transition and a temperature peak at medium- to high-pressure granulite-facies conditions. In addition, we discuss that all “evidence” for ultrahigh-pressure metamorphism proposed in the literature for rocks of this area is equivocal. Accordingly, the Nordre Strømfjord shear zone is not an example of modern-style plate tectonics in the Paleoproterozoic or of very low thermal gradients and extreme pressure conditions in general.
{"title":"Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland","authors":"J. Schönig, Carsten Benner, G. Meinhold, H. von Eynatten, N. K. Lünsdorf","doi":"10.5194/ejm-35-479-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-479-2023","url":null,"abstract":"Abstract. Modern-style plate tectonics is characterised by the\u0000global operation of cold and deep subduction involving blueschist facies and\u0000ultrahigh-pressure metamorphism. This has been a common process since the\u0000Neoproterozoic, but a couple of studies indicate similar processes were\u0000active in the Paleoproterozoic, at least on the local scale. Particularly\u0000conspicuous are extreme ultrahigh-pressure conditions of ∼ 7 GPa at thermal gradients < 150 ∘C GPa−1 proposed for\u0000metamorphic rocks of the Nordre Strømfjord shear zone in the western part\u0000of the Paleoproterozoic Nagssugtoqidian Orogen of Greenland. By acquiring a\u0000large dataset of heavy minerals (n = 52 130) and garnet major-element\u0000composition integrated with mineral inclusion analysis (n=2669) from\u0000modern sands representing fresh and naturally mixed erosional material from\u0000the metamorphic rocks, we here intensely screened the area for potential\u0000occurrences of ultrahigh-pressure rocks and put constraints on the\u0000metamorphic evolution. Apart from the absence of any indications pointing to\u0000ultrahigh-pressure and low-temperature–high-pressure metamorphism, the\u0000results are well in accordance with a common Paleoproterozoic\u0000subduction–collision metamorphic evolution along a Barrovian-type\u0000intermediate temperature and pressure gradient with a pressure peak at the\u0000amphibolite–granulite–eclogite-facies transition and a temperature peak\u0000at medium- to high-pressure granulite-facies conditions. In addition, we\u0000discuss that all “evidence” for ultrahigh-pressure metamorphism proposed\u0000in the literature for rocks of this area is equivocal. Accordingly, the\u0000Nordre Strømfjord shear zone is not an example of modern-style plate\u0000tectonics in the Paleoproterozoic or of very low thermal gradients and\u0000extreme pressure conditions in general.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46988300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ross J. Angel, M. Mazzucchelli, K. Musiyachenko, F. Nestola, M. Alvaro
Abstract. Elastic thermobarometry (or piezobarometry) is the process of determining the P (pressure) and T (temperature) of entrapment of inclusions from their pressure, stress or strain measured when their host mineral is at room conditions. The methods and software used for piezobarometry are currently restricted to inclusions consisting of single phases. In this contribution we describe the theory of the elasticity of mixtures of different phases and combine it with the existing isotropic analysis of the elastic interactions between single-phase inclusions and their hosts to calculate the inclusion pressures of mixed-phase inclusions. The analysis shows that the reliability of calculated entrapment conditions for mixed-phase inclusions, including those containing fluid plus minerals, depends in a complex way upon the contrasts between the elastic properties of the host and the phases in the inclusion. The methods to calculate the entrapment conditions of mixed-phase inclusions have been incorporated into the EosFit7c program (version 7.6) that is available as freeware from http://www.rossangel.net.
{"title":"Elasticity of mixtures and implications for piezobarometry of mixed-phase inclusions","authors":"Ross J. Angel, M. Mazzucchelli, K. Musiyachenko, F. Nestola, M. Alvaro","doi":"10.5194/ejm-35-461-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-461-2023","url":null,"abstract":"Abstract. Elastic thermobarometry (or piezobarometry) is the process of determining\u0000the P (pressure) and T (temperature) of entrapment of inclusions from their pressure, stress or strain\u0000measured when their host mineral is at room conditions. The methods and\u0000software used for piezobarometry are currently restricted to inclusions\u0000consisting of single phases. In this contribution we describe the theory of\u0000the elasticity of mixtures of different phases and combine it with the\u0000existing isotropic analysis of the elastic interactions between single-phase\u0000inclusions and their hosts to calculate the inclusion pressures of\u0000mixed-phase inclusions. The analysis shows that the reliability of\u0000calculated entrapment conditions for mixed-phase inclusions, including those\u0000containing fluid plus minerals, depends in a complex way upon the contrasts\u0000between the elastic properties of the host and the phases in the inclusion.\u0000The methods to calculate the entrapment conditions of mixed-phase inclusions\u0000have been incorporated into the EosFit7c program (version 7.6) that is available as\u0000freeware from http://www.rossangel.net.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41355338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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