We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossb...We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossbauer spectroscopy （up to 8 GPa）. Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mossbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mossbauer parameters and population inversion of Fe^2＋ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of - 12 GPa implied residual stress experienced due to shock impact. The presence of high pressure （monoclinic） phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.展开更多
1 Introduction Generally,we can observe varying degree of ophitic texture or sub-ophitic texture in unbrecciated basaltic eucrites.However,a few unbrecciated basaltic eucritespossess the special characteristic of crys...1 Introduction Generally,we can observe varying degree of ophitic texture or sub-ophitic texture in unbrecciated basaltic eucrites.However,a few unbrecciated basaltic eucritespossess the special characteristic of crystalloblastic texture by high metamorphism,which are called as granoblastic textured basaltic eucrites(Mayne et al.2009,展开更多
Grove Mountains （GRV） 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene （62.9 vol% ） and plagioclase （34.2 vol% ）, with less abundant opaque minerals （2.7 vol% ）, minor silica ...Grove Mountains （GRV） 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene （62.9 vol% ） and plagioclase （34.2 vol% ）, with less abundant opaque minerals （2.7 vol% ）, minor silica and tiny FeO-rich olivine （FaTs）. Coarse-grained pyroxenes show exsolution of augite lamellae in pigeonite or vice versa. Width of most exsolution lamellae in pyroxenes is 1-3 μm. Opaque minerals are mainly chromite, ilmenite and sulfides. The meteorite was heavily shocked, as indicated by breccias and melt veins. Coarse-grained pyroxenes commonly contain abundant tiny or needle-like chromite inclusions with orientation, probably due to heavy shock events. Pyroxenes in various petrographic occurrences exhibit highly homogeneous compositions, indicating that GRV 051523 experienced intense thermal metamorphism in the parent asteroid 4 Vesta. GRV 051523 is classified as Type 5-6. This new eucrite will have additional constraints on chemical composition, magmatic differentiation, multi-stage shock and thermal history of Vesta.展开更多
Grove Mountains (GRV) 99018 is a new eucrite (0.23 g), consisting mainly of pyroxene (50.5 vol%) and plagioclase (37.2 vol%) with minor silica minerals (7.0 Vol%) and opaque minerals (5.2 vol%). It was intensely shock...Grove Mountains (GRV) 99018 is a new eucrite (0.23 g), consisting mainly of pyroxene (50.5 vol%) and plagioclase (37.2 vol%) with minor silica minerals (7.0 Vol%) and opaque minerals (5.2 vol%). It was intensely shocked, leading to partial melting, formation of abundant tiny inclusions in pyroxenes and plagioclase, and heavy brecciation. Exsolution of most pyroxenes (1-3μm in width of the lamellae), recrystallization of the shpck-induced melt pockets and veins (5-20μm in size), and homogeneous compositions of pyroxenes of various occurrences suggest the intense thermal metamorphism of GRV 99018 in the asteroidal body Vesta. This new eucrite will bring additional constraints on the chemical composition and multi-stage thermal and shock history of Vesta.展开更多
基金Council of Scientific and Industrial Research(CSIR),PLANEX program of India Space Research Organization,Department of Space(Government of India),CSR-SHORE-PSC-02005 and ISRO projects(GP)for funding, CSIR for providing Emeritus Scientist Fellowship(UC)
文摘We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossbauer spectroscopy （up to 8 GPa）. Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mossbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mossbauer parameters and population inversion of Fe^2＋ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of - 12 GPa implied residual stress experienced due to shock impact. The presence of high pressure （monoclinic） phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.
基金supported by the National Natural Foundation of China (No. 41173077)
文摘1 Introduction Generally,we can observe varying degree of ophitic texture or sub-ophitic texture in unbrecciated basaltic eucrites.However,a few unbrecciated basaltic eucritespossess the special characteristic of crystalloblastic texture by high metamorphism,which are called as granoblastic textured basaltic eucrites(Mayne et al.2009,
基金supported by the Knowledge-Innovation Program(kzcx2-yw-110,KZCX2-YW-Q08)One-Hundred-Talent Program of the Chinese Academy of Sciences
文摘Grove Mountains （GRV） 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene （62.9 vol% ） and plagioclase （34.2 vol% ）, with less abundant opaque minerals （2.7 vol% ）, minor silica and tiny FeO-rich olivine （FaTs）. Coarse-grained pyroxenes show exsolution of augite lamellae in pigeonite or vice versa. Width of most exsolution lamellae in pyroxenes is 1-3 μm. Opaque minerals are mainly chromite, ilmenite and sulfides. The meteorite was heavily shocked, as indicated by breccias and melt veins. Coarse-grained pyroxenes commonly contain abundant tiny or needle-like chromite inclusions with orientation, probably due to heavy shock events. Pyroxenes in various petrographic occurrences exhibit highly homogeneous compositions, indicating that GRV 051523 experienced intense thermal metamorphism in the parent asteroid 4 Vesta. GRV 051523 is classified as Type 5-6. This new eucrite will have additional constraints on chemical composition, magmatic differentiation, multi-stage shock and thermal history of Vesta.
基金We are grateful to Drs Guan Yunbin and Xu Ping for their assistance in laboratories This study is supported by the National Natural Science Foundation of China(Grant No.40232026)the pilot project of knowledge-innovation program of the Chinese Academy of Sciences(Grant No.KZCX3-SW-l23).
文摘Grove Mountains (GRV) 99018 is a new eucrite (0.23 g), consisting mainly of pyroxene (50.5 vol%) and plagioclase (37.2 vol%) with minor silica minerals (7.0 Vol%) and opaque minerals (5.2 vol%). It was intensely shocked, leading to partial melting, formation of abundant tiny inclusions in pyroxenes and plagioclase, and heavy brecciation. Exsolution of most pyroxenes (1-3μm in width of the lamellae), recrystallization of the shpck-induced melt pockets and veins (5-20μm in size), and homogeneous compositions of pyroxenes of various occurrences suggest the intense thermal metamorphism of GRV 99018 in the asteroidal body Vesta. This new eucrite will bring additional constraints on the chemical composition and multi-stage thermal and shock history of Vesta.
