The Xiuyan Jade samples were treated under thermal conditions. By polarizing microscope, the three kinds of jade were choosed. With DTA-TG analysis, three transition temperatures were obtained which were 600℃, 770℃ ...The Xiuyan Jade samples were treated under thermal conditions. By polarizing microscope, the three kinds of jade were choosed. With DTA-TG analysis, three transition temperatures were obtained which were 600℃, 770℃ and 840℃. The study interpreted the mechanism of Xiuyan Jade under thermal condition through XRD analysis results. The mechanism of antigorite thermal activation was as following: when the temperature reached 600℃, the hydroxyl in octahedral sheet began dehydrating, and the new mineral phase forsterite was found, but the layer structure was maintained; when the temperature reached 770℃, the layer structure of antigorite was destroyed; when the temperature reached 840℃, the crystallinity of forsterite was improved, then another new mineral phase enstatite appeard. For talc, it was likely turn to enstatite directly while the temperature rising, and the appearance of SiO2 was most likely due to the conversion of talc.展开更多
The water migration in subduction zones,primarily driven by the phase transition in hydrous minerals,can give rise to hydrated regions with reduced velocity.A fundamental element in comprehending and deciphering these...The water migration in subduction zones,primarily driven by the phase transition in hydrous minerals,can give rise to hydrated regions with reduced velocity.A fundamental element in comprehending and deciphering these low-velocity zones revolves around acquiring insights into the stability and elasticity of relevant hydrous minerals.As one of the main water carriers in shallow areas,antigorite can dehydrate to form talc,forsterite,and fluid(talc-bearing peridotites)in deep areas of subduction zones,and then the talc thus serves as one of the minerals that can bring water to the deep Earth.Here,the elasticity of talc up to 24 GPa and forsterite up to 12 GPa are calculated by using the first principles method.The result supposes that the talc structure transforming from talc I to talc II is at a pressure between 6 GPa and 8 GPa,impacting the trend of elastic wave velocity in response to pressure.Furthermore,the elastic wave velocity of forsterite can be significantly affected by iron concentration.Meanwhile,a variation velocity model with antigorite consumption and talc content is set up for talc-bearing serpentinized peridotite based on the elastic properties of talc and forsterite in this study,and antigorite in Wang et al.(2022).The results of our model demonstrate a decrease in the low-velocity anomaly in subduction zones,particularly in deep regions or areas with higher initial serpentinization degrees.The results also suggest that the mode of antigorite dehydration can diminish the estimation of water content transported to depths of subduction zones,such as the Mariana Trench and Northern Japan subduction zones.The mode of antigorite dehydration thus provides a useful tool for constraining the composition,seismic velocity structure,and water migration in subduction zones.展开更多
Serpentinized peridotites in the Yangkou(YK),Suoluoshu(SLS) and Hujialin(HJL) areas in the Sulu ultrahighpressure terrane represent the relic of ancient subcontinental lithospheric mantle below the North China Craton....Serpentinized peridotites in the Yangkou(YK),Suoluoshu(SLS) and Hujialin(HJL) areas in the Sulu ultrahighpressure terrane represent the relic of ancient subcontinental lithospheric mantle below the North China Craton.Their protoliths,harzburgite and dunite,were variably hydrated by aqueous fluids released from subducting Yangtze continent.The rocks are enriched in fluid-mobile elements(FME) including Sb(42–333 times the depleted mantle value) and Pb(30–476 times).The degrees of the FME enrichment are comparable to that of the Himalayan forearc serpentinites,and greater than forearc mantle serpentinites from Marianas,suggesting that the degrees of FME enrichment in the forearc serpentinites are greater in continental subduction zones than those in the oceanic subduction zones.Lizardite after olivine in the SLS serpentinite shows higher degrees of enrichment in Sb and As than those for antigorite after both olivine and orthopyroxene in the YK area.The antigorite has highly enriched in Pb,U,Cs,and LREE,but not for the lizardite.The abundance of FME in two different species of serpentine reflects the different temperature of hydration.At temperature lower than 300 ℃,formed lizardite at shallow depths of the mantle wedge incorporates elements that are fluid mobile at low temperatures,such as Sb and As.When the temperature greater than 300 ℃,formed antigorite at a relatively deep mantle wedge incorporate more FME from the subducting continental slab(or fragments),including Pb,U,Cs,LREE as well as Sb and As.The eventual breakdown of antigorite(600–700 ℃) in prograde metamorphism would discharge water as well as FME into the subducting channel and/or the overlying mantle.展开更多
In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile(which have the same general formula Mg3Si2O5(OH)4), and talc(Mg3Si4O10(OH)2) were reacted with KOH to prepare catal...In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile(which have the same general formula Mg3Si2O5(OH)4), and talc(Mg3Si4O10(OH)2) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20 wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K2MgSiO4 phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K2MgSiO4 formation. All the materials showed catalytic activity for the transesterification of soybean oil(1:6 of oil : methanol molar ratio, 5 wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K2MgSiO4.展开更多
Having beautiful colours and fine features, Xiuyan jade is famous in the world. Mineralogically, Xiuyan jade is serpentine jade. XRD, IR and TEM studies indicate that the jade consists mainly of antigorite (m{Mg3(1-1/...Having beautiful colours and fine features, Xiuyan jade is famous in the world. Mineralogically, Xiuyan jade is serpentine jade. XRD, IR and TEM studies indicate that the jade consists mainly of antigorite (m{Mg3(1-1/m)[Si2O5](OH)1+3(1-2/m}) with a minor amount of chrysotile. Two favourite samples (PxA, Px1-1), chosen for research on Fe Mossbauer spectra, are only antigorite. Studies indicate that: a. iron ion in antigorite enters the lattice as impurity; b. Fe2+ and Fe3+ substitute for Mg in the coordination octahedron; and c. the colour of jade is related to content of Fe, and Fe2+/Fe3+≤1 is favourite for colour-forming.展开更多
Covered by ultrabasic units for more than a third of its surface,the New Caledonia(South West Pacific)is one of the largest world producers of Ni-ore from lateritic deposits.Almost all outcrops of geological units and...Covered by ultrabasic units for more than a third of its surface,the New Caledonia(South West Pacific)is one of the largest world producers of Ni-ore from lateritic deposits.Almost all outcrops of geological units and open mines contain serpentine and amphibole,also as asbestos varieties.In this geological context,in which weathering processes had a great contribution in the production and dispersion of mineral fibres into the environment,the development of a routinely analytical strategy,able to discriminate an asbestiform fibre from a non-harmful particle,is a pivotal requisite.However,the acquisition of all these parameters is necessary for determining the risk associated to fibres exposition.A multidisciplinary routinely approach,based on the use of complementary simply-to-use but reliable analytical methods is the only possible strategy.In addition,the instrumental apparatus must be easily transportable on the field,directly on the mining site.The employment of specialized tools such as Polarized Light Microscopy associated to Dispersion Staining method(PLM/DS)and portable Raman spectroscopy for identification of environmental asbestos,are proved extremely effective in the improvement of the performance and rapidity of data acquisition and interpretation.Both PLM/DS and handheld Raman devices confirmed to be discriminant in the detection and characterization of asbestos fibres for both serpentine and amphibole.Furthermore,these techniques proved extremely effective even in the presence of strongly fibrous and altered samples.展开更多
基金Supported by National Natural Science Foundation (Grant No.:40872045 41172047)The Opening Project of Key Laboratory of Solid Waste Treatment and Resource Recycle (SWUST), Ministry of Education (12zxgk01)
文摘The Xiuyan Jade samples were treated under thermal conditions. By polarizing microscope, the three kinds of jade were choosed. With DTA-TG analysis, three transition temperatures were obtained which were 600℃, 770℃ and 840℃. The study interpreted the mechanism of Xiuyan Jade under thermal condition through XRD analysis results. The mechanism of antigorite thermal activation was as following: when the temperature reached 600℃, the hydroxyl in octahedral sheet began dehydrating, and the new mineral phase forsterite was found, but the layer structure was maintained; when the temperature reached 770℃, the layer structure of antigorite was destroyed; when the temperature reached 840℃, the crystallinity of forsterite was improved, then another new mineral phase enstatite appeard. For talc, it was likely turn to enstatite directly while the temperature rising, and the appearance of SiO2 was most likely due to the conversion of talc.
基金supported by the National Natural Science Foundation of China(Grant No.42174114,41674089).
文摘The water migration in subduction zones,primarily driven by the phase transition in hydrous minerals,can give rise to hydrated regions with reduced velocity.A fundamental element in comprehending and deciphering these low-velocity zones revolves around acquiring insights into the stability and elasticity of relevant hydrous minerals.As one of the main water carriers in shallow areas,antigorite can dehydrate to form talc,forsterite,and fluid(talc-bearing peridotites)in deep areas of subduction zones,and then the talc thus serves as one of the minerals that can bring water to the deep Earth.Here,the elasticity of talc up to 24 GPa and forsterite up to 12 GPa are calculated by using the first principles method.The result supposes that the talc structure transforming from talc I to talc II is at a pressure between 6 GPa and 8 GPa,impacting the trend of elastic wave velocity in response to pressure.Furthermore,the elastic wave velocity of forsterite can be significantly affected by iron concentration.Meanwhile,a variation velocity model with antigorite consumption and talc content is set up for talc-bearing serpentinized peridotite based on the elastic properties of talc and forsterite in this study,and antigorite in Wang et al.(2022).The results of our model demonstrate a decrease in the low-velocity anomaly in subduction zones,particularly in deep regions or areas with higher initial serpentinization degrees.The results also suggest that the mode of antigorite dehydration can diminish the estimation of water content transported to depths of subduction zones,such as the Mariana Trench and Northern Japan subduction zones.The mode of antigorite dehydration thus provides a useful tool for constraining the composition,seismic velocity structure,and water migration in subduction zones.
基金by the National Natural Science Foundation of China(Grant Nos.41603032,41472051,41802215 and 4176201)Applied Basic Research Foundation of Yunnan Province(Grant No.2017FB075)to ZPX,JW and YPD.
文摘Serpentinized peridotites in the Yangkou(YK),Suoluoshu(SLS) and Hujialin(HJL) areas in the Sulu ultrahighpressure terrane represent the relic of ancient subcontinental lithospheric mantle below the North China Craton.Their protoliths,harzburgite and dunite,were variably hydrated by aqueous fluids released from subducting Yangtze continent.The rocks are enriched in fluid-mobile elements(FME) including Sb(42–333 times the depleted mantle value) and Pb(30–476 times).The degrees of the FME enrichment are comparable to that of the Himalayan forearc serpentinites,and greater than forearc mantle serpentinites from Marianas,suggesting that the degrees of FME enrichment in the forearc serpentinites are greater in continental subduction zones than those in the oceanic subduction zones.Lizardite after olivine in the SLS serpentinite shows higher degrees of enrichment in Sb and As than those for antigorite after both olivine and orthopyroxene in the YK area.The antigorite has highly enriched in Pb,U,Cs,and LREE,but not for the lizardite.The abundance of FME in two different species of serpentine reflects the different temperature of hydration.At temperature lower than 300 ℃,formed lizardite at shallow depths of the mantle wedge incorporates elements that are fluid mobile at low temperatures,such as Sb and As.When the temperature greater than 300 ℃,formed antigorite at a relatively deep mantle wedge incorporate more FME from the subducting continental slab(or fragments),including Pb,U,Cs,LREE as well as Sb and As.The eventual breakdown of antigorite(600–700 ℃) in prograde metamorphism would discharge water as well as FME into the subducting channel and/or the overlying mantle.
文摘In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile(which have the same general formula Mg3Si2O5(OH)4), and talc(Mg3Si4O10(OH)2) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20 wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K2MgSiO4 phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K2MgSiO4 formation. All the materials showed catalytic activity for the transesterification of soybean oil(1:6 of oil : methanol molar ratio, 5 wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K2MgSiO4.
文摘Having beautiful colours and fine features, Xiuyan jade is famous in the world. Mineralogically, Xiuyan jade is serpentine jade. XRD, IR and TEM studies indicate that the jade consists mainly of antigorite (m{Mg3(1-1/m)[Si2O5](OH)1+3(1-2/m}) with a minor amount of chrysotile. Two favourite samples (PxA, Px1-1), chosen for research on Fe Mossbauer spectra, are only antigorite. Studies indicate that: a. iron ion in antigorite enters the lattice as impurity; b. Fe2+ and Fe3+ substitute for Mg in the coordination octahedron; and c. the colour of jade is related to content of Fe, and Fe2+/Fe3+≤1 is favourite for colour-forming.
基金supported by the CNRT "Nickel and its environment" of New Caledonia
文摘Covered by ultrabasic units for more than a third of its surface,the New Caledonia(South West Pacific)is one of the largest world producers of Ni-ore from lateritic deposits.Almost all outcrops of geological units and open mines contain serpentine and amphibole,also as asbestos varieties.In this geological context,in which weathering processes had a great contribution in the production and dispersion of mineral fibres into the environment,the development of a routinely analytical strategy,able to discriminate an asbestiform fibre from a non-harmful particle,is a pivotal requisite.However,the acquisition of all these parameters is necessary for determining the risk associated to fibres exposition.A multidisciplinary routinely approach,based on the use of complementary simply-to-use but reliable analytical methods is the only possible strategy.In addition,the instrumental apparatus must be easily transportable on the field,directly on the mining site.The employment of specialized tools such as Polarized Light Microscopy associated to Dispersion Staining method(PLM/DS)and portable Raman spectroscopy for identification of environmental asbestos,are proved extremely effective in the improvement of the performance and rapidity of data acquisition and interpretation.Both PLM/DS and handheld Raman devices confirmed to be discriminant in the detection and characterization of asbestos fibres for both serpentine and amphibole.Furthermore,these techniques proved extremely effective even in the presence of strongly fibrous and altered samples.
