Systematic experimental studies on partial melting and subsolidus equilibration of three reconstituted spinel-peridotites have been carried out at temperatures ranging from 1000 to 1380℃ and pressures of 1.0 and 1.5 ...Systematic experimental studies on partial melting and subsolidus equilibration of three reconstituted spinel-peridotites have been carried out at temperatures ranging from 1000 to 1380℃ and pressures of 1.0 and 1.5 GPa. The results shows (1) during partial melting, Mg# [=Mg/(Mg+Fe)]and Cr# [=Cr/(Cr-Al)]of spinel increase with an increase in degrees of melting) (2) during subsolidus equilibration, with increasing temperatures, Mg# of spinel increases but Cr# of spinel remains almost unchanged in dunite and increases slightly in Iherzolite and harzburgite. The negative and quasi-linear Mg# -Cr# correlation of spinel represents an isotherm of total non-equilibrium. The same results have been obtained by means of mathematical modelling. It is also proved by Mg# -Cr# correlation of spinel in natural peridotites. As a result of the spinel subsolidus equilibration, only variation of Cr# of spinel is limited, and then Cr# of spinel can be used to estimate the relative degree of melting undergone by host rocks. The bigger Cr# of spinel is, the higher the degree of melting will be. By contrast, during crystallization magma, Mg# and Cr# of spinel decrease with decreasing temperatures. Likewise, Cr# of spinel in basalts may be used to indicate the feature of Cr2O3/Al2O3 of magma, and the compositional zoning of spinel may be used to study the evolution of magma (cooling rate and contamination).展开更多
The Beni Bousera ultramafic massif is a tectonically emplaced body of upper mantle material that is exposed over 72 km2at the base of the internal zones of the Alpine Rif belt of northern Morocco.The predominant litho...The Beni Bousera ultramafic massif is a tectonically emplaced body of upper mantle material that is exposed over 72 km2at the base of the internal zones of the Alpine Rif belt of northern Morocco.The predominant lithology in展开更多
Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens w...Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens were fired at 1600℃for 5 h,1700℃for 0 h and 1800℃for 7 h,respectively.The microstructure of the MgO-MgAl2O4-ZrO2 subsystem was studied by FESEM.The results show that(1)in the temperature range of 1600-1700℃,solid phase reactions happen in the MgO-MgAl2O4-ZrO2 subsystem,leaving three phases:periclase,spinel and ZrO2(solid dissolving with Mg2+)co-existing;spinellization affects the densification;(2)the specimen with 40%ZrO2 fired at 1800℃has heterogeneous melting microstructure;some areas form typical ternary eutectic MgO-MgAl2O4-ZrO2 with composition of MgO 35.2%-37.2%,Al2O324.2%-26.6%,and ZrO237.2%-39.8%.展开更多
The Damiao Fe-Ti-P deposit,located within the Damiao anorthosite complex in northeastern China,features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies,lenses,or veins with sh...The Damiao Fe-Ti-P deposit,located within the Damiao anorthosite complex in northeastern China,features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies,lenses,or veins with sharp contacts against anorthosite and gabbronorite.This deposit is characterized by abundant titanomagnetite that hosts diverse ilmenite exsolution textures,including blocky,lamellar,and cloth-like forms.In this study,we investigate the geochemistry and mineralogy of ilmenite exsolutions in titanomagnetite to understand their formation mechanisms and implications for the ore-forming process.Detailed petrographic observations and electron microprobe analyses reveal that the exsolution textures result from multiple mechanisms:oxy-exsolution due to titanomagnetite oxidation;subsolidus re-equilibration between magnetite and ilmenite involving elemental diffusion of Fe,Ti,Cr,Co,and Ni;and exsolution related to lattice defects caused by rapid cooling.Thermodynamic modeling using Gibbs free energy calculations,and the QUILF program indicates that blocky,lamellar,and cloth-textured ilmenite exsolutions formed at temperatures above and below the solid-solution solvus under decreasing oxygen fugacity.Additionally,our results indicate that the exsolution of zircon and pleonaste at ilmenite grain boundaries is attributed to the saturation and precipitation of elements like Zr and Al,due to the oxidation of titanomagnetite,rather than interactions between ilmenite and adjacent clinopyroxene.Reconstruction of the cooling history suggests that the oxygen fugacity of oxide-apatite gabbronorites was significantly higher than that of Fe-Ti-P ores.This confirms that increasing oxygen fugacity during magma evolution promoted immiscibility,leading to the formation of nelsonitic melts and ultimately the development of Fe-Ti-P ores.展开更多
The subsolidus phase relations were determined experimentally in the system MgO-ZnO-SiO2 at 1.0 GPa and 1 200℃, by use of the high-pressure apparatus "piston-cylinder". The results showed characteristics of...The subsolidus phase relations were determined experimentally in the system MgO-ZnO-SiO2 at 1.0 GPa and 1 200℃, by use of the high-pressure apparatus "piston-cylinder". The results showed characteristics of the phases assemblage different from that in similar ternary systems. It is impossible to form complete Mg2SiO4-Zn2SiO4 olivine and Mg2Si2O6-Zn2Si2O6 pyroxene solid solution. This is controlled by the properties of Zn2+ with an outer layer of electron (Ar)3d10, different from others transition metal ions, like Fe2+ , Ni2+ , Co2+ .展开更多
文摘Systematic experimental studies on partial melting and subsolidus equilibration of three reconstituted spinel-peridotites have been carried out at temperatures ranging from 1000 to 1380℃ and pressures of 1.0 and 1.5 GPa. The results shows (1) during partial melting, Mg# [=Mg/(Mg+Fe)]and Cr# [=Cr/(Cr-Al)]of spinel increase with an increase in degrees of melting) (2) during subsolidus equilibration, with increasing temperatures, Mg# of spinel increases but Cr# of spinel remains almost unchanged in dunite and increases slightly in Iherzolite and harzburgite. The negative and quasi-linear Mg# -Cr# correlation of spinel represents an isotherm of total non-equilibrium. The same results have been obtained by means of mathematical modelling. It is also proved by Mg# -Cr# correlation of spinel in natural peridotites. As a result of the spinel subsolidus equilibration, only variation of Cr# of spinel is limited, and then Cr# of spinel can be used to estimate the relative degree of melting undergone by host rocks. The bigger Cr# of spinel is, the higher the degree of melting will be. By contrast, during crystallization magma, Mg# and Cr# of spinel decrease with decreasing temperatures. Likewise, Cr# of spinel in basalts may be used to indicate the feature of Cr2O3/Al2O3 of magma, and the compositional zoning of spinel may be used to study the evolution of magma (cooling rate and contamination).
文摘The Beni Bousera ultramafic massif is a tectonically emplaced body of upper mantle material that is exposed over 72 km2at the base of the internal zones of the Alpine Rif belt of northern Morocco.The predominant lithology in
基金The author would like to thank Fu Qiuhua,Zhang Wei and Fan Qingsong for their surport to this work.
文摘Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens were fired at 1600℃for 5 h,1700℃for 0 h and 1800℃for 7 h,respectively.The microstructure of the MgO-MgAl2O4-ZrO2 subsystem was studied by FESEM.The results show that(1)in the temperature range of 1600-1700℃,solid phase reactions happen in the MgO-MgAl2O4-ZrO2 subsystem,leaving three phases:periclase,spinel and ZrO2(solid dissolving with Mg2+)co-existing;spinellization affects the densification;(2)the specimen with 40%ZrO2 fired at 1800℃has heterogeneous melting microstructure;some areas form typical ternary eutectic MgO-MgAl2O4-ZrO2 with composition of MgO 35.2%-37.2%,Al2O324.2%-26.6%,and ZrO237.2%-39.8%.
基金funded by the National Natural Science Foundation of China(grant 42102094)Natural Science Foundation of Hebei(Grant D2022402028).
文摘The Damiao Fe-Ti-P deposit,located within the Damiao anorthosite complex in northeastern China,features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies,lenses,or veins with sharp contacts against anorthosite and gabbronorite.This deposit is characterized by abundant titanomagnetite that hosts diverse ilmenite exsolution textures,including blocky,lamellar,and cloth-like forms.In this study,we investigate the geochemistry and mineralogy of ilmenite exsolutions in titanomagnetite to understand their formation mechanisms and implications for the ore-forming process.Detailed petrographic observations and electron microprobe analyses reveal that the exsolution textures result from multiple mechanisms:oxy-exsolution due to titanomagnetite oxidation;subsolidus re-equilibration between magnetite and ilmenite involving elemental diffusion of Fe,Ti,Cr,Co,and Ni;and exsolution related to lattice defects caused by rapid cooling.Thermodynamic modeling using Gibbs free energy calculations,and the QUILF program indicates that blocky,lamellar,and cloth-textured ilmenite exsolutions formed at temperatures above and below the solid-solution solvus under decreasing oxygen fugacity.Additionally,our results indicate that the exsolution of zircon and pleonaste at ilmenite grain boundaries is attributed to the saturation and precipitation of elements like Zr and Al,due to the oxidation of titanomagnetite,rather than interactions between ilmenite and adjacent clinopyroxene.Reconstruction of the cooling history suggests that the oxygen fugacity of oxide-apatite gabbronorites was significantly higher than that of Fe-Ti-P ores.This confirms that increasing oxygen fugacity during magma evolution promoted immiscibility,leading to the formation of nelsonitic melts and ultimately the development of Fe-Ti-P ores.
文摘The subsolidus phase relations were determined experimentally in the system MgO-ZnO-SiO2 at 1.0 GPa and 1 200℃, by use of the high-pressure apparatus "piston-cylinder". The results showed characteristics of the phases assemblage different from that in similar ternary systems. It is impossible to form complete Mg2SiO4-Zn2SiO4 olivine and Mg2Si2O6-Zn2Si2O6 pyroxene solid solution. This is controlled by the properties of Zn2+ with an outer layer of electron (Ar)3d10, different from others transition metal ions, like Fe2+ , Ni2+ , Co2+ .
