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Bruno Messiga - One of the best experts on this subject based on the ideXlab platform.
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prograde metamorphic evolution and development of Chloritoid bearing eclogitic assemblages in subcontinental metagabbro sesia lanzo zone italy
Lithos, 2007Co-Authors: Gisella Rebay, Bruno MessigaAbstract:Abstract In the coronitic metagabbroic rocks of the Corio and Monastero metagabbro bodies in the continental Sesia–Lanzo zone of the western Italian Alps, a variety of mineral reactions that testify to prograde conditions from greenschist to eclogite-facies can be recognised. A microstructural and microchemical study of a series of samples characterized by coronitic textures and pseudomorphic replacement of the original igneous minerals has allowed the prograde reactions undergone by the rocks to be established. In completely eclogitized coronitic samples, paragonite, blue amphibole, garnet, epidote, fine grained jadeite and Chloritoid occur in plagioclase microdomains (former igneous plagioclase). The mafic mineral microdomains consist of glaucophane and garnet. Complexly-zoned amphiboles constrain changing metamorphic conditions: cores of pre-Alpine brown hornblende and/or tremolite are preserved inside rims of a sodic–calcic amphibole that are in turn surrounded by a sodic amphibole. The main high-pressure mineral assemblage, as seen in mylonites, involves glaucophane, Chloritoid, epidote, garnet ± phengite, ± paragonite. Some layers within the gabbro contain garnet, omphacite, ± glaucophane, and acid dykes crosscutting the gabbro body contain jadeite, quartz, garnet, epidote and paragonite. The presence of Chloritoid-bearing high-pressure assemblages reflects hydration of the gabbros during their pre-Alpine exhumation prior to subduction, as well as the composition of the microdomains operating during subduction. The pressure and temperature conditions of gabbro transformation during subduction are inferred to be 450–550 °C at up to 2 GPa on the basis of the Chloritoid-bearing assemblages. The factors controlling the reaction pathway to form Chloritoid-bearing high-pressure assemblages in mafic rocks are inferred from these observations.
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Prograde metamorphic evolution and development of Chloritoid-bearing eclogitic assemblages in subcontinental metagabbro (Sesia–Lanzo zone, Italy)
Lithos, 2007Co-Authors: Gisella Rebay, Bruno MessigaAbstract:Abstract In the coronitic metagabbroic rocks of the Corio and Monastero metagabbro bodies in the continental Sesia–Lanzo zone of the western Italian Alps, a variety of mineral reactions that testify to prograde conditions from greenschist to eclogite-facies can be recognised. A microstructural and microchemical study of a series of samples characterized by coronitic textures and pseudomorphic replacement of the original igneous minerals has allowed the prograde reactions undergone by the rocks to be established. In completely eclogitized coronitic samples, paragonite, blue amphibole, garnet, epidote, fine grained jadeite and Chloritoid occur in plagioclase microdomains (former igneous plagioclase). The mafic mineral microdomains consist of glaucophane and garnet. Complexly-zoned amphiboles constrain changing metamorphic conditions: cores of pre-Alpine brown hornblende and/or tremolite are preserved inside rims of a sodic–calcic amphibole that are in turn surrounded by a sodic amphibole. The main high-pressure mineral assemblage, as seen in mylonites, involves glaucophane, Chloritoid, epidote, garnet ± phengite, ± paragonite. Some layers within the gabbro contain garnet, omphacite, ± glaucophane, and acid dykes crosscutting the gabbro body contain jadeite, quartz, garnet, epidote and paragonite. The presence of Chloritoid-bearing high-pressure assemblages reflects hydration of the gabbros during their pre-Alpine exhumation prior to subduction, as well as the composition of the microdomains operating during subduction. The pressure and temperature conditions of gabbro transformation during subduction are inferred to be 450–550 °C at up to 2 GPa on the basis of the Chloritoid-bearing assemblages. The factors controlling the reaction pathway to form Chloritoid-bearing high-pressure assemblages in mafic rocks are inferred from these observations.
I. Memmi - One of the best experts on this subject based on the ideXlab platform.
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Zoning of Chloritoid from kyanite-facies metapsammites, Alpi Apuane, Italy
2015Co-Authors: M. Francesciii&apos, I. MemmiAbstract:Chloritoid with significant Mg-Fe zoning occurs as lath-shaped porphyroblasts and as clusters of subradiating crystals in the Triassic Verrucano metapsammite (quartz + muscovite ~ chlorite + Chloritoid-b kyanite) of the Massa Unit, Alpi Apuane. Two main types of Chloritoid zoning profiles were found. The first type is characterised by gradual increase in Mg from core to rim of the porphyroblasts. In the second type the Mg content is constant from the core to the inner rim, but sharply decreases in the outer im. Both types of zoning have been interpreted as the result of prograde growth during the Alpine metamorphism. The temperature, stimated using the chlorite-Chloritoid themlometer, anges from 467 to 560"C
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zoning of Chloritoid from kyanite facies metapsammites alpi apuane italy
Mineralogical Magazine, 1999Co-Authors: M. Franceschelli, I. MemmiAbstract:Chloritoid with significant Mg-Fe zoning occurs as lath-shaped porphyroblasts and as clusters of subradiating crystals in the Triassic Verrucano metapsammite (quartz+muscovite+chlorite+Chloritoid+ or -kyanite) of the Massa Unit, Alpi Apuane. Two main types of Chloritoid zoning profiles were found. The first type is characterised by gradual increase in Mg from core to rim of the porphyroblasts. In the second type the Mg content is constant from the core to the inner rim, but sharply decreases in the outer rim. Both types of zoning have been interpreted as the result of prograde growth during the Alpine metamorphism. The temperature, estimated using the chlorite-Chloritoid thermometer, ranges from 467 to 560 degrees C.
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Zoning of Chloritoid from kyanite-facies metapsammites, Alpi Apuane, Italy
Mineralogical Magazine, 1999Co-Authors: M. Franceschelli, I. MemmiAbstract:Abstract Chloritoid with significant Mg-Fe zoning occurs as lath-shaped porphyroblasts and as clusters of subradiating crystals in the Triassic Verrucano metapsammite (quartz + muscovite + chlorite + Chloritoid ± kyanite) of the Massa Unit, Alpi Apuane. Two main types of Chloritoid zoning profiles were found. The first type is characterised by gradual increase in Mg from core to rim of the porphyroblasts. In the second type the Mg content is constant from the core to the inner rim, but sharply decreases in the outer rim. Both types of zoning have been interpreted as the result of prograde growth during the Alpine metamorphism. The temperature, estimated using the chlorite-Chloritoid thermometer, ranges from 467 to 560°C.
Xu Chu - One of the best experts on this subject based on the ideXlab platform.
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lawsonite bearing Chloritoid glaucophane schist from sw tianshan china phase equilibria and p t path
Journal of Asian Earth Sciences, 2011Co-Authors: Lifei Zhang, Xu ChuAbstract:Abstract Lawsonite-bearing Chloritoid–glaucophane schist has been discovered firstly in the high to ultra-high pressure (HP–UHP) metamorphic belt in Southwestern Tianshan, China. It is characterized by the mineral assemblage of lawsonite + Chloritoid + glaucophane + phengite + paragonite + epidote/allanite + chlorite + quartz + dolomite/calcite + rutile + tourmaline. Lawsonite and Chloritoid exclusively occur as micro-inclusions in the cores and mantles of porphyroblastic glaucophane. The glaucophane is coarse-grained (about 1–20 mm long), and forms euhedral to subhedral crystals with distinct growth zonation. The X (gln) [=Fe2 + /(Fe 2+ + Mg)] increases outwards from 0.40 to 0.63, indicating growth under decreasing temperature and pressure. Phase equilibrium modeling in the system of NCKFMASHO (Na 2 O–CaO–K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O–O) by THERMOCALC 3.30 reveals that glaucophane was formed during retrograde metamorphism. Based on the compositional zonation of glaucophane and its mineral inclusions, the peak P – T conditions were 23.2–25.3 kbar and 499–519 °C, 17–20 kbar and 430–530 °C for the first retrograde stage (A) and 15–17 kbar and 470–530 °C for the second retrograde stage (B). The obtained retrograde P – T path indicates a rapid uplift involving an early isothermal decompressional stage similar to that of Alpine-type blueschists.
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Lawsonite-bearing Chloritoid–glaucophane schist from SW Tianshan, China: Phase equilibria and P–T path
Journal of Asian Earth Sciences, 2011Co-Authors: Lifei Zhang, Xu ChuAbstract:Abstract Lawsonite-bearing Chloritoid–glaucophane schist has been discovered firstly in the high to ultra-high pressure (HP–UHP) metamorphic belt in Southwestern Tianshan, China. It is characterized by the mineral assemblage of lawsonite + Chloritoid + glaucophane + phengite + paragonite + epidote/allanite + chlorite + quartz + dolomite/calcite + rutile + tourmaline. Lawsonite and Chloritoid exclusively occur as micro-inclusions in the cores and mantles of porphyroblastic glaucophane. The glaucophane is coarse-grained (about 1–20 mm long), and forms euhedral to subhedral crystals with distinct growth zonation. The X (gln) [=Fe2 + /(Fe 2+ + Mg)] increases outwards from 0.40 to 0.63, indicating growth under decreasing temperature and pressure. Phase equilibrium modeling in the system of NCKFMASHO (Na 2 O–CaO–K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O–O) by THERMOCALC 3.30 reveals that glaucophane was formed during retrograde metamorphism. Based on the compositional zonation of glaucophane and its mineral inclusions, the peak P – T conditions were 23.2–25.3 kbar and 499–519 °C, 17–20 kbar and 430–530 °C for the first retrograde stage (A) and 15–17 kbar and 470–530 °C for the second retrograde stage (B). The obtained retrograde P – T path indicates a rapid uplift involving an early isothermal decompressional stage similar to that of Alpine-type blueschists.
Gisella Rebay - One of the best experts on this subject based on the ideXlab platform.
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prograde metamorphic evolution and development of Chloritoid bearing eclogitic assemblages in subcontinental metagabbro sesia lanzo zone italy
Lithos, 2007Co-Authors: Gisella Rebay, Bruno MessigaAbstract:Abstract In the coronitic metagabbroic rocks of the Corio and Monastero metagabbro bodies in the continental Sesia–Lanzo zone of the western Italian Alps, a variety of mineral reactions that testify to prograde conditions from greenschist to eclogite-facies can be recognised. A microstructural and microchemical study of a series of samples characterized by coronitic textures and pseudomorphic replacement of the original igneous minerals has allowed the prograde reactions undergone by the rocks to be established. In completely eclogitized coronitic samples, paragonite, blue amphibole, garnet, epidote, fine grained jadeite and Chloritoid occur in plagioclase microdomains (former igneous plagioclase). The mafic mineral microdomains consist of glaucophane and garnet. Complexly-zoned amphiboles constrain changing metamorphic conditions: cores of pre-Alpine brown hornblende and/or tremolite are preserved inside rims of a sodic–calcic amphibole that are in turn surrounded by a sodic amphibole. The main high-pressure mineral assemblage, as seen in mylonites, involves glaucophane, Chloritoid, epidote, garnet ± phengite, ± paragonite. Some layers within the gabbro contain garnet, omphacite, ± glaucophane, and acid dykes crosscutting the gabbro body contain jadeite, quartz, garnet, epidote and paragonite. The presence of Chloritoid-bearing high-pressure assemblages reflects hydration of the gabbros during their pre-Alpine exhumation prior to subduction, as well as the composition of the microdomains operating during subduction. The pressure and temperature conditions of gabbro transformation during subduction are inferred to be 450–550 °C at up to 2 GPa on the basis of the Chloritoid-bearing assemblages. The factors controlling the reaction pathway to form Chloritoid-bearing high-pressure assemblages in mafic rocks are inferred from these observations.
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Prograde metamorphic evolution and development of Chloritoid-bearing eclogitic assemblages in subcontinental metagabbro (Sesia–Lanzo zone, Italy)
Lithos, 2007Co-Authors: Gisella Rebay, Bruno MessigaAbstract:Abstract In the coronitic metagabbroic rocks of the Corio and Monastero metagabbro bodies in the continental Sesia–Lanzo zone of the western Italian Alps, a variety of mineral reactions that testify to prograde conditions from greenschist to eclogite-facies can be recognised. A microstructural and microchemical study of a series of samples characterized by coronitic textures and pseudomorphic replacement of the original igneous minerals has allowed the prograde reactions undergone by the rocks to be established. In completely eclogitized coronitic samples, paragonite, blue amphibole, garnet, epidote, fine grained jadeite and Chloritoid occur in plagioclase microdomains (former igneous plagioclase). The mafic mineral microdomains consist of glaucophane and garnet. Complexly-zoned amphiboles constrain changing metamorphic conditions: cores of pre-Alpine brown hornblende and/or tremolite are preserved inside rims of a sodic–calcic amphibole that are in turn surrounded by a sodic amphibole. The main high-pressure mineral assemblage, as seen in mylonites, involves glaucophane, Chloritoid, epidote, garnet ± phengite, ± paragonite. Some layers within the gabbro contain garnet, omphacite, ± glaucophane, and acid dykes crosscutting the gabbro body contain jadeite, quartz, garnet, epidote and paragonite. The presence of Chloritoid-bearing high-pressure assemblages reflects hydration of the gabbros during their pre-Alpine exhumation prior to subduction, as well as the composition of the microdomains operating during subduction. The pressure and temperature conditions of gabbro transformation during subduction are inferred to be 450–550 °C at up to 2 GPa on the basis of the Chloritoid-bearing assemblages. The factors controlling the reaction pathway to form Chloritoid-bearing high-pressure assemblages in mafic rocks are inferred from these observations.
Lifei Zhang - One of the best experts on this subject based on the ideXlab platform.
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lawsonite bearing Chloritoid glaucophane schist from sw tianshan china phase equilibria and p t path
Journal of Asian Earth Sciences, 2011Co-Authors: Lifei Zhang, Xu ChuAbstract:Abstract Lawsonite-bearing Chloritoid–glaucophane schist has been discovered firstly in the high to ultra-high pressure (HP–UHP) metamorphic belt in Southwestern Tianshan, China. It is characterized by the mineral assemblage of lawsonite + Chloritoid + glaucophane + phengite + paragonite + epidote/allanite + chlorite + quartz + dolomite/calcite + rutile + tourmaline. Lawsonite and Chloritoid exclusively occur as micro-inclusions in the cores and mantles of porphyroblastic glaucophane. The glaucophane is coarse-grained (about 1–20 mm long), and forms euhedral to subhedral crystals with distinct growth zonation. The X (gln) [=Fe2 + /(Fe 2+ + Mg)] increases outwards from 0.40 to 0.63, indicating growth under decreasing temperature and pressure. Phase equilibrium modeling in the system of NCKFMASHO (Na 2 O–CaO–K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O–O) by THERMOCALC 3.30 reveals that glaucophane was formed during retrograde metamorphism. Based on the compositional zonation of glaucophane and its mineral inclusions, the peak P – T conditions were 23.2–25.3 kbar and 499–519 °C, 17–20 kbar and 430–530 °C for the first retrograde stage (A) and 15–17 kbar and 470–530 °C for the second retrograde stage (B). The obtained retrograde P – T path indicates a rapid uplift involving an early isothermal decompressional stage similar to that of Alpine-type blueschists.
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Lawsonite-bearing Chloritoid–glaucophane schist from SW Tianshan, China: Phase equilibria and P–T path
Journal of Asian Earth Sciences, 2011Co-Authors: Lifei Zhang, Xu ChuAbstract:Abstract Lawsonite-bearing Chloritoid–glaucophane schist has been discovered firstly in the high to ultra-high pressure (HP–UHP) metamorphic belt in Southwestern Tianshan, China. It is characterized by the mineral assemblage of lawsonite + Chloritoid + glaucophane + phengite + paragonite + epidote/allanite + chlorite + quartz + dolomite/calcite + rutile + tourmaline. Lawsonite and Chloritoid exclusively occur as micro-inclusions in the cores and mantles of porphyroblastic glaucophane. The glaucophane is coarse-grained (about 1–20 mm long), and forms euhedral to subhedral crystals with distinct growth zonation. The X (gln) [=Fe2 + /(Fe 2+ + Mg)] increases outwards from 0.40 to 0.63, indicating growth under decreasing temperature and pressure. Phase equilibrium modeling in the system of NCKFMASHO (Na 2 O–CaO–K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O–O) by THERMOCALC 3.30 reveals that glaucophane was formed during retrograde metamorphism. Based on the compositional zonation of glaucophane and its mineral inclusions, the peak P – T conditions were 23.2–25.3 kbar and 499–519 °C, 17–20 kbar and 430–530 °C for the first retrograde stage (A) and 15–17 kbar and 470–530 °C for the second retrograde stage (B). The obtained retrograde P – T path indicates a rapid uplift involving an early isothermal decompressional stage similar to that of Alpine-type blueschists.