The thermal expansion coefficients of kyanite at ambient pressure have been investigated by an X-ray powder diffraction technique with temperatures up to 1000 ℃. No phase transition was observed in the experimental t...The thermal expansion coefficients of kyanite at ambient pressure have been investigated by an X-ray powder diffraction technique with temperatures up to 1000 ℃. No phase transition was observed in the experimental temperature range. Data for the unit-cell parameters and temperatures were fitted empirically resulting in the following thermal expansion coefficients： αa = 5.8（3） × 10^-5, αb = 5.8 （1）× 10^-5, αc = 5.2（1）× 10^-5, and αv = 7.4（1） × 10^-3 ℃ 1 in good agreement with a recent neutron powder diffraction study. On the other hand, the variation of the unit-cell angles α, β and γ of kyanite with increase in temperature is very complicated, and the agreement among all studies is poor. The thermal expansion data at ambient pressure reported here and the compression data at ambient temperature from the literature suggest that, for the kyanite lattice, the most and least thermally expandable directions correspond to the most and least compressible directions, respectively.展开更多
Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF3·3H20. The as-prepared whiskers have been characterized systematically in terms of phase composition, mor...Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF3·3H20. The as-prepared whiskers have been characterized systematically in terms of phase composition, morphology, and structure. Results showed that the morphology and size of mullite whiskers were strongly depended on the content of AlF3·3H20 and sintering temperature. At temperatures in the range of 1 100 to 1 500 ℃ with 4 wt% addition of AlF3·3H20, the well-shaped mullite whiskers were obtained. For an instance, the mullite whiskers with 5-10 μm in length and 0.1-0.2 μm in cross-section could be formed at 1 400 ℃, with 4 wt% addition of A1F3·3H20. Moreover, results showed that the addition of mullite whiskers into ceramic matrix enhanced its fracture toughness significantly.展开更多
Coesite inclusions are found in kyanite from the Lanshantou eclogite in the Sulu ultrahigh-pressure (UHP) metamorphic belt. This discovery extends the stable region of kyanite to over 2.4 GPa. As an important UHP meta...Coesite inclusions are found in kyanite from the Lanshantou eclogite in the Sulu ultrahigh-pressure (UHP) metamorphic belt. This discovery extends the stable region of kyanite to over 2.4 GPa. As an important UHP metamorphic belt in China, the Sulu eclogite belt is the product of A-subduction induced by strong compression of the Yellow Sea terrane to the Jiaodong-northereastern Jiangsu terrane during the interaction of the Eurasian plate and Palaeo-Pacific plate in the Indosinian. It stretches about 350 km and contains over 1000 eclogite bodies. Most eclogites in this belt belong to Groups B and C in the classification of Coleman et al., and commonly contain kyanite, while the Lanshantou eclogite belongs to Group A and contains coesite. The MgO, CaO and FeO contents in garnet and pyroxene show regular variation from the core to the rim, which reveals the PTt paths of progressive metamorphism during the Early Mesozoic (240-200 Ma) and retrogressive metamorphism during the Late Mesozoic and Cenozoic exhumation.展开更多
Sillimanite, kyanite and andalusite are advantageous natural refractory raw materials for aluminosilicate refractories to attain improved key properties. This paper are divided into two parts to introduce their resour...Sillimanite, kyanite and andalusite are advantageous natural refractory raw materials for aluminosilicate refractories to attain improved key properties. This paper are divided into two parts to introduce their resource and technical characteristic in the first part, and their applications in refractories in the second part to be succeeded . In this part, based on authors ' knowledge and sources , information on their reserve, distribution, composition and characteristic is provided , to bring it to light that China is rich in the reserve of them , in particular andalusite. The sillimanite group minerals are characterized by their phase transformation to form primary mullite and secondary mullite when added in high alumina system , accompanied by volume expansion , which can be taken use to improve creep resistances and thermal shock resistance of the related refractories.展开更多
As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep ear...As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep earth. Here we present a detailed investigation of water concentrations of kyanite, and for reference, of garnet and omphacite from four Maobei eclogites in the Sulu orogenic belt, eastern China. Fourier transform infrared （FTIR） measurements show that kyanites, garnets, and omphacites all have distinct hydroxyl absorption bands due to OH groups bound in their crystal struc- ture. The FTIR profile analyses on ten grains from different samples reveal a homogeneous distribution of water across kyanite, suggesting insignificant water loss during exhumation. The calculated water concentrations in kyanite （21 wt ppm-41 wt ppm） are comparable to those reported previously for kyanite from various geological occurrences when using the most recent calibration. They are however much lower compared with those in garnet （46 wt ppm-83 wt ppm） and omphacite （302 wt ppm-548 wt ppm） from the Maobei eclogites. This implies that kyanite is not a major water carrier in eclogites con- sidering its low volume fraction and contributes negligibly to transport water into the deep mantle ac- companying subducted oceanic crust until its possible transformation to AISiO3OH.展开更多
Corundum(ruby-sapphire) is known to have formed in situ within Archean metamorphic rocks at several localities in the North Atlantic Craton of Greenland. Here we present two case studies for such occurrences:(1) Manii...Corundum(ruby-sapphire) is known to have formed in situ within Archean metamorphic rocks at several localities in the North Atlantic Craton of Greenland. Here we present two case studies for such occurrences:(1) Maniitsoq region(Kangerdluarssuk), where kyanite paragneiss hosts ruby corundum, and(2)Nuuk region(Stor?), where sillimanite gneiss hosts ruby corundum. At both occurrences, ultramafic rocks(amphibole-peridotite) are in direct contact with the ruby-bearing zones, which have been transformed to mica schist by metasomatic reactions. The bulk-rock geochemistry of the ruby-bearing rocks is consistent with significant depletion of SiO_2 in combination with addition of Al_2O_3, MgO, K_2O,Th and Sr relative to an assumed aluminous precursor metapelite. Phase equilibria modelling supports ruby genesis from the breakdown of sillimanite and kyanite at elevated temperatures due to the removal of SiO_2. The juxtaposition of relatively silica-and aluminum-rich metasedimentary rocks with low silica ultramafic rocks established a chemical potential gradient that leached/mobilized SiO_2 allowing corundum to stabilize in the former rocks. Furthermore, addition of Al_2O_3 via a metasomatic reaction is required, because Al/Ti is fractionated between the aluminous precursor metapelites and the resulting corundum-bearing mica schist. We propose that Al was mobilized either by complexation with hydroxide at alkaline conditions, or that Al was transported as K-Al-Si-O polymers at deep crustal levels.The three main exploration vectors for corundum within Archean greenstone belts are:(1) amphiboliteto granulite-facies metamorphic conditions,(2) the juxtaposition of ultramafic rocks and aluminous metapelite, and(3) mica-rich reactions zones at their interface.展开更多
基金financially supported by the Natural Science Foundation of China(Grant 40872033)the Fundamental Research Funds for the Central Universities(to XL)the Natural Sciences and Engineering Research Council of Canada(to MF)
文摘The thermal expansion coefficients of kyanite at ambient pressure have been investigated by an X-ray powder diffraction technique with temperatures up to 1000 ℃. No phase transition was observed in the experimental temperature range. Data for the unit-cell parameters and temperatures were fitted empirically resulting in the following thermal expansion coefficients： αa = 5.8（3） × 10^-5, αb = 5.8 （1）× 10^-5, αc = 5.2（1）× 10^-5, and αv = 7.4（1） × 10^-3 ℃ 1 in good agreement with a recent neutron powder diffraction study. On the other hand, the variation of the unit-cell angles α, β and γ of kyanite with increase in temperature is very complicated, and the agreement among all studies is poor. The thermal expansion data at ambient pressure reported here and the compression data at ambient temperature from the literature suggest that, for the kyanite lattice, the most and least thermally expandable directions correspond to the most and least compressible directions, respectively.
文摘Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF3·3H20. The as-prepared whiskers have been characterized systematically in terms of phase composition, morphology, and structure. Results showed that the morphology and size of mullite whiskers were strongly depended on the content of AlF3·3H20 and sintering temperature. At temperatures in the range of 1 100 to 1 500 ℃ with 4 wt% addition of AlF3·3H20, the well-shaped mullite whiskers were obtained. For an instance, the mullite whiskers with 5-10 μm in length and 0.1-0.2 μm in cross-section could be formed at 1 400 ℃, with 4 wt% addition of A1F3·3H20. Moreover, results showed that the addition of mullite whiskers into ceramic matrix enhanced its fracture toughness significantly.
文摘Coesite inclusions are found in kyanite from the Lanshantou eclogite in the Sulu ultrahigh-pressure (UHP) metamorphic belt. This discovery extends the stable region of kyanite to over 2.4 GPa. As an important UHP metamorphic belt in China, the Sulu eclogite belt is the product of A-subduction induced by strong compression of the Yellow Sea terrane to the Jiaodong-northereastern Jiangsu terrane during the interaction of the Eurasian plate and Palaeo-Pacific plate in the Indosinian. It stretches about 350 km and contains over 1000 eclogite bodies. Most eclogites in this belt belong to Groups B and C in the classification of Coleman et al., and commonly contain kyanite, while the Lanshantou eclogite belongs to Group A and contains coesite. The MgO, CaO and FeO contents in garnet and pyroxene show regular variation from the core to the rim, which reveals the PTt paths of progressive metamorphism during the Early Mesozoic (240-200 Ma) and retrogressive metamorphism during the Late Mesozoic and Cenozoic exhumation.
文摘Sillimanite, kyanite and andalusite are advantageous natural refractory raw materials for aluminosilicate refractories to attain improved key properties. This paper are divided into two parts to introduce their resource and technical characteristic in the first part, and their applications in refractories in the second part to be succeeded . In this part, based on authors ' knowledge and sources , information on their reserve, distribution, composition and characteristic is provided , to bring it to light that China is rich in the reserve of them , in particular andalusite. The sillimanite group minerals are characterized by their phase transformation to form primary mullite and secondary mullite when added in high alumina system , accompanied by volume expansion , which can be taken use to improve creep resistances and thermal shock resistance of the related refractories.
基金supported by the National Natural Science Foundation of China (Nos. 41372224 and 41590623)
文摘As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep earth. Here we present a detailed investigation of water concentrations of kyanite, and for reference, of garnet and omphacite from four Maobei eclogites in the Sulu orogenic belt, eastern China. Fourier transform infrared （FTIR） measurements show that kyanites, garnets, and omphacites all have distinct hydroxyl absorption bands due to OH groups bound in their crystal struc- ture. The FTIR profile analyses on ten grains from different samples reveal a homogeneous distribution of water across kyanite, suggesting insignificant water loss during exhumation. The calculated water concentrations in kyanite （21 wt ppm-41 wt ppm） are comparable to those reported previously for kyanite from various geological occurrences when using the most recent calibration. They are however much lower compared with those in garnet （46 wt ppm-83 wt ppm） and omphacite （302 wt ppm-548 wt ppm） from the Maobei eclogites. This implies that kyanite is not a major water carrier in eclogites con- sidering its low volume fraction and contributes negligibly to transport water into the deep mantle ac- companying subducted oceanic crust until its possible transformation to AISiO3OH.
基金the CARLSBERG FOUNDATION for support to carry out this work via grant CF16-0059
文摘Corundum(ruby-sapphire) is known to have formed in situ within Archean metamorphic rocks at several localities in the North Atlantic Craton of Greenland. Here we present two case studies for such occurrences:(1) Maniitsoq region(Kangerdluarssuk), where kyanite paragneiss hosts ruby corundum, and(2)Nuuk region(Stor?), where sillimanite gneiss hosts ruby corundum. At both occurrences, ultramafic rocks(amphibole-peridotite) are in direct contact with the ruby-bearing zones, which have been transformed to mica schist by metasomatic reactions. The bulk-rock geochemistry of the ruby-bearing rocks is consistent with significant depletion of SiO_2 in combination with addition of Al_2O_3, MgO, K_2O,Th and Sr relative to an assumed aluminous precursor metapelite. Phase equilibria modelling supports ruby genesis from the breakdown of sillimanite and kyanite at elevated temperatures due to the removal of SiO_2. The juxtaposition of relatively silica-and aluminum-rich metasedimentary rocks with low silica ultramafic rocks established a chemical potential gradient that leached/mobilized SiO_2 allowing corundum to stabilize in the former rocks. Furthermore, addition of Al_2O_3 via a metasomatic reaction is required, because Al/Ti is fractionated between the aluminous precursor metapelites and the resulting corundum-bearing mica schist. We propose that Al was mobilized either by complexation with hydroxide at alkaline conditions, or that Al was transported as K-Al-Si-O polymers at deep crustal levels.The three main exploration vectors for corundum within Archean greenstone belts are:(1) amphiboliteto granulite-facies metamorphic conditions,(2) the juxtaposition of ultramafic rocks and aluminous metapelite, and(3) mica-rich reactions zones at their interface.
