We present results of field studies for magmatic processes of 2.57-2.52 Ga calc-alkaline plutonic bodies from three corridors in the eastern Dharwar craton(EDC)corresponding to different crustal levels.At deeper level...We present results of field studies for magmatic processes of 2.57-2.52 Ga calc-alkaline plutonic bodies from three corridors in the eastern Dharwar craton(EDC)corresponding to different crustal levels.At deeper levels plutons are bounded by thick zone of migmatites with numerous melt filled shear bands which often overprinted by incipient charnockite.On the other hand in the mid-to-upper crustal levels plutons show relatively sharp contacts and truncates the adjoining basement.The plutons are composite which comprises voluminous intrusive monzodiorite,quartz-monzonite and porphyritic monzogranite in the central part and minor anatectic granites or diatexite at periphery.Numerous xenoliths,Mafic Magmatic Enclaves(MME),disrupted trains of synplutonic mafic dykes are found in both intrusive and anatectic facies.The plutons show magmatic as well as solid-state plastic fabrics defined by magmatic flow banding and C-S fabrics respectively.Crustal scale shear zone network comprising early melt filled NE trending hot ductile dextral shear bands and slightly later colder NW trending sinistral shear bands defined by rotation of mafic boudins,phenocrysts and C-S fabrics.The internal architecture of plutons is attributed to the crustal scale magma chamber processes where voluminous intrusive magmas emplaced into the crust caused reworking of surrounding basement resulting in production of anatectic magmas.Crystallization of voluminous intrusive magmas in the deep crust probably caused development of fractures to mantle depth causing decompression melting of mantle and resultant mafic magmas penetrated the crystallizing host in magma chambers.Field evidences together with published ages and Nd isotope data reveal a spatial link between late Archaean magmatic accretion,reworking and cratonization.展开更多
A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented fo...A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories： （i） Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H20 or pressure or composition of the crystallizing melt; and （ii） morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma （convection, turbulence, degassing, etc.）. Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self- mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics.展开更多
A water model and a high-speed video camera were utilized in the 300-t RH equipment to study the effect of steel flow patterns in a vacuum chamber on fast decarburization and a superior flow-pattern map was obtained d...A water model and a high-speed video camera were utilized in the 300-t RH equipment to study the effect of steel flow patterns in a vacuum chamber on fast decarburization and a superior flow-pattern map was obtained during the practical RH process. There are three flow patterns with different bubbling characteristics and steel surface states in the vacuum chamber： boiling pattern（BP）, transition pattern（TP）, and wave pattern（WP）. The effect of the liquid-steel level and the residence time of the steel in the chamber on flow patterns and decarburization reaction were investigated, respectively. The liquid-steel level significantly affected the flow-pattern transition from BP to WP, and the residence time and reaction area were crucial to evaluate the whole decarburization process rather than the circulation flow rate and mixing time. A superior flow-pattern map during the practical RH process showed that the steel flow pattern changed from BP to TP quickly, and then remained as TP until the end of decarburization.展开更多
基金funded by Department of Science and Technology(DST),Govt.of India funded project ESS/16/297/2007.
文摘We present results of field studies for magmatic processes of 2.57-2.52 Ga calc-alkaline plutonic bodies from three corridors in the eastern Dharwar craton(EDC)corresponding to different crustal levels.At deeper levels plutons are bounded by thick zone of migmatites with numerous melt filled shear bands which often overprinted by incipient charnockite.On the other hand in the mid-to-upper crustal levels plutons show relatively sharp contacts and truncates the adjoining basement.The plutons are composite which comprises voluminous intrusive monzodiorite,quartz-monzonite and porphyritic monzogranite in the central part and minor anatectic granites or diatexite at periphery.Numerous xenoliths,Mafic Magmatic Enclaves(MME),disrupted trains of synplutonic mafic dykes are found in both intrusive and anatectic facies.The plutons show magmatic as well as solid-state plastic fabrics defined by magmatic flow banding and C-S fabrics respectively.Crustal scale shear zone network comprising early melt filled NE trending hot ductile dextral shear bands and slightly later colder NW trending sinistral shear bands defined by rotation of mafic boudins,phenocrysts and C-S fabrics.The internal architecture of plutons is attributed to the crustal scale magma chamber processes where voluminous intrusive magmas emplaced into the crust caused reworking of surrounding basement resulting in production of anatectic magmas.Crystallization of voluminous intrusive magmas in the deep crust probably caused development of fractures to mantle depth causing decompression melting of mantle and resultant mafic magmas penetrated the crystallizing host in magma chambers.Field evidences together with published ages and Nd isotope data reveal a spatial link between late Archaean magmatic accretion,reworking and cratonization.
文摘A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories： （i） Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H20 or pressure or composition of the crystallizing melt; and （ii） morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma （convection, turbulence, degassing, etc.）. Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self- mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics.
基金financially supported by the National Natural Science Foundation of China (No.51704203)the PhD Early Development Program of Taiyuan University of Science and Technology (Nos. 20152008, 20152013, and 20152018)+2 种基金Shanxi Province Science Foundation for Youths (No. 201601D202027)Key Project of Research and Development Plan of Shanxi Province (Nos. 201603D111004 and 201603D121010)NSFC-Shanxi Coal Based Low Carbon Joint Fund (No. U1510131)
文摘A water model and a high-speed video camera were utilized in the 300-t RH equipment to study the effect of steel flow patterns in a vacuum chamber on fast decarburization and a superior flow-pattern map was obtained during the practical RH process. There are three flow patterns with different bubbling characteristics and steel surface states in the vacuum chamber： boiling pattern（BP）, transition pattern（TP）, and wave pattern（WP）. The effect of the liquid-steel level and the residence time of the steel in the chamber on flow patterns and decarburization reaction were investigated, respectively. The liquid-steel level significantly affected the flow-pattern transition from BP to WP, and the residence time and reaction area were crucial to evaluate the whole decarburization process rather than the circulation flow rate and mixing time. A superior flow-pattern map during the practical RH process showed that the steel flow pattern changed from BP to TP quickly, and then remained as TP until the end of decarburization.
