Epidote is a typical hydrous mineral in subduction zones.Here,we report a synchrotron-based single-crystal X-ray diffraction(XRD)study of natural epidote[Ca1.97Al2.15Fe0.84(SiO4)(Si2O7)O(OH)]under simultaneously high ...Epidote is a typical hydrous mineral in subduction zones.Here,we report a synchrotron-based single-crystal X-ray diffraction(XRD)study of natural epidote[Ca1.97Al2.15Fe0.84(SiO4)(Si2O7)O(OH)]under simultaneously high pressure-temperature(high P-T)conditions to~17.7 GPa and 700 K.No phase transition occurs over this P-T range.Using the third-order Birch-Murnaghan equation of state(EoS),we fitted the pressure-volume-temperature(P-V-T)data and obtained the zero-pressure bulk modulus K_(0)=138(2)GPa,its pressure derivative K'_(0)=3.0(3),the temperature derivative of the bulk modulus((∂K/∂T)P=-0.004(1)GPa/K),and the thermal expansion coefficient at 300 K(α_(0)=3.8(5)×10^(-5)K^(-1)),as the zero-pressure unit-cell volume V_(0)was fixed at 465.2(2)Å^(3)(obtained by a single-crystal XRD experiment at ambient conditions).This study reveals that the bulk moduli of epidote show nonlinear compositional dependence.By discussing the stabilization of epidote and comparing its density with those of other hydrous minerals,we find that epidote,as a significant water transporter in subduction zones,may maintain a metastable state to~14 GPa along the coldest subducting slab geotherm and promote slab subduction into the upper mantle while favoring slab stagnation above the 410 km discontinuity.Furthermore,the water released from epidote near 410 km may potentially affect the properties of the 410 km seismic discontinuity.展开更多
The rock types of the alkaline dyke from Anta Gorda region, in the township of Doutor Ulysses (State of Paraná), encompass three lithological groups that have been individualized for their distinct textural, stru...The rock types of the alkaline dyke from Anta Gorda region, in the township of Doutor Ulysses (State of Paraná), encompass three lithological groups that have been individualized for their distinct textural, structural, mineralogical and/or geochemical characteristics: phonolites s.s., amygdaloidal phonolites and trachyphonolites. These are rocks with magmatic derivation, in which the most important differentiation processes interpreted were immiscibility and fractional crystallization from the ultrabasic mantellic source with primary magma. Fenite epidotes were also classified in the study area, probably product of fenitization of the granitic wall rock. Due to the geographical proximity, some similarities between the phonolites and the rocks from the Barra do Teixeira alkaline plug or the Banhadão Alkaline Complex were expected. However, the results of the petrographic and geochemical analysis point to major resemblance between the phonolites and the lithotypes of the Mato Preto Alkaline Complex. The studied rocks contain concentrations of economic interest of important chemicals elements, mainly Rare Earth Elements—REE, trace elements and mineral substances, such as zeolites and fluorites.展开更多
The \%P_T\% paths of the Xiaoqinling metamorphic core complex (XMCC) have been investigated with the Gibbs method by researching the compositional changing of zoned epidotes which formed during syn_deformation metamor...The \%P_T\% paths of the Xiaoqinling metamorphic core complex (XMCC) have been investigated with the Gibbs method by researching the compositional changing of zoned epidotes which formed during syn_deformation metamorphism. These \%P_T\% paths indicate that the XMCC had experienced the following thermodynamics processes: firstly, near isobaric falling slightly in temperature in lower crust; secondly, fast decompression and rising in temperature during extensional uplifting to middle crust level; and finally, isobaric falling in temperature in middle crust. The upwelling and emplacement of the deep magma may be a major factor during the uplifting processes of the metamorphic core complex.展开更多
基金the National Natural Science Foundation of China(Grant Nos.41772043 and 41802043)the CAS"Light of West China"Program(2017 and 2019),the Youth Innovation Promotion Association CAS(Dawei Fan,2018434)+4 种基金the Innovation and Entrepreneurship Funding of High-Level Overseas Talents of Guizhou Province(Dawei Fan,[2019]10)GeoSoilEnviroCARS(The University of Chicago,Sector 13)Advanced Photon Source(APS),Argonne National Laboratory.GeoSoilEnviroCARS is supported by the National Science Foundation(EAR-0622171)the Department of Energy(DE-FG02-94ER14466)under Contract No.DE-AC02-06CH11357the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.
文摘Epidote is a typical hydrous mineral in subduction zones.Here,we report a synchrotron-based single-crystal X-ray diffraction(XRD)study of natural epidote[Ca1.97Al2.15Fe0.84(SiO4)(Si2O7)O(OH)]under simultaneously high pressure-temperature(high P-T)conditions to~17.7 GPa and 700 K.No phase transition occurs over this P-T range.Using the third-order Birch-Murnaghan equation of state(EoS),we fitted the pressure-volume-temperature(P-V-T)data and obtained the zero-pressure bulk modulus K_(0)=138(2)GPa,its pressure derivative K'_(0)=3.0(3),the temperature derivative of the bulk modulus((∂K/∂T)P=-0.004(1)GPa/K),and the thermal expansion coefficient at 300 K(α_(0)=3.8(5)×10^(-5)K^(-1)),as the zero-pressure unit-cell volume V_(0)was fixed at 465.2(2)Å^(3)(obtained by a single-crystal XRD experiment at ambient conditions).This study reveals that the bulk moduli of epidote show nonlinear compositional dependence.By discussing the stabilization of epidote and comparing its density with those of other hydrous minerals,we find that epidote,as a significant water transporter in subduction zones,may maintain a metastable state to~14 GPa along the coldest subducting slab geotherm and promote slab subduction into the upper mantle while favoring slab stagnation above the 410 km discontinuity.Furthermore,the water released from epidote near 410 km may potentially affect the properties of the 410 km seismic discontinuity.
文摘The rock types of the alkaline dyke from Anta Gorda region, in the township of Doutor Ulysses (State of Paraná), encompass three lithological groups that have been individualized for their distinct textural, structural, mineralogical and/or geochemical characteristics: phonolites s.s., amygdaloidal phonolites and trachyphonolites. These are rocks with magmatic derivation, in which the most important differentiation processes interpreted were immiscibility and fractional crystallization from the ultrabasic mantellic source with primary magma. Fenite epidotes were also classified in the study area, probably product of fenitization of the granitic wall rock. Due to the geographical proximity, some similarities between the phonolites and the rocks from the Barra do Teixeira alkaline plug or the Banhadão Alkaline Complex were expected. However, the results of the petrographic and geochemical analysis point to major resemblance between the phonolites and the lithotypes of the Mato Preto Alkaline Complex. The studied rocks contain concentrations of economic interest of important chemicals elements, mainly Rare Earth Elements—REE, trace elements and mineral substances, such as zeolites and fluorites.
文摘The \%P_T\% paths of the Xiaoqinling metamorphic core complex (XMCC) have been investigated with the Gibbs method by researching the compositional changing of zoned epidotes which formed during syn_deformation metamorphism. These \%P_T\% paths indicate that the XMCC had experienced the following thermodynamics processes: firstly, near isobaric falling slightly in temperature in lower crust; secondly, fast decompression and rising in temperature during extensional uplifting to middle crust level; and finally, isobaric falling in temperature in middle crust. The upwelling and emplacement of the deep magma may be a major factor during the uplifting processes of the metamorphic core complex.
