Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History

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	Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History
	Wang Linyan 1; Hsu Weibiao 1,2; Ma Changqian 1
刊名	ACTA GEOLOGICA SINICA-ENGLISH EDITION
	2010
卷号	84 期号:3 页码:528-542
关键词	mesosiderite metal-silicate mixing thermal metamorphism formation history Antarctica
ISSN号	1000-9515
英文摘要	GRV 020175 is an Antarctic mesosiderite, containing about 43 vol% silicates and 57 vol% metal. Metal occurs in a variety of textures from irregular large masses, to veins penetrating silicates, and to matrix fine grains. The metallic portion contains kamacite, troilite and minor taenite. Terrestrial weathering is evident as partial replacement of the metal and troilite veins by Fe oxides. Silicate phases exhibit a porphyritic texture with pyroxene, plagioclase, minor silica and rare olivine phenocrysts embedded in a fine-grained groundmass. The matrix is ophitic and consists mainly of pyroxene and plagioclase grains. Some orthopyroxene phenocrysts occur as euhedral crystals with chemical zoning from a magnesian core to a ferroan overgrowth; others are characterized by many fine inclusions of plagioclase composition. Pigeonite has almost inverted to its orthopyroxene host with augite lamellae, enclosed by more magnesian rims. Olivine occurs as subhedral crystals, surrounded by a necklace of tiny chromite grains (about 2-3 mu m). Plagioclase has a heterogeneous composition without zoning. Pyroxene geothermometry of GRV 020175 gives a peak metamorphic temperature (similar to 1000 degrees C) and a closure temperature (similar to 875 degrees C). Molar Fe/Mn ratios (19-32) of pyroxenes are consistent with mesosiderite pyroxenes (16-35) and most plagioclase compositions (An(87.5-96.6)) are within the range of mesosiderite plagioclase grains (An(88-95)). Olivine composition (Fo(53.8)) is only slightly lower than the range of olivine compositions in mesosiderites (Fo(55-90)). All petrographic characteristics and chemical compositions of GRV 020175 are consistent with those of mesosiderite and based on its matrix texture and relatively abundant plagioclase, it can be further classified as a type 3A mesosiderite. Mineralogical, petrological, and geochemical studies of GRV 020175 imply a complex formation history starting as rapid crystallization from a magma in a lava flow on the surface or as a shallow intrusion. Following primary igneous crystallization, the silicate underwent varying degrees of reheating. It was reheated to 1000 degrees C, followed by rapid cooling to 875 degrees C. Subsequently, metal mixed with silicate, during or after which, reduction of silicates occurred; the reducing agent is likely to have been sulfur. After redox reaction, the sample underwent thermal metamorphism, which produced the corona on the olivine, rims on the inverted pigeonite phenocrysts and overgrowths on the orthopyroxene phenocrysts, and homogenized matrix pyroxenes. Nevertheless, metamorphism was not extensive enough to completely reequilibrate the GRV 020175 materials.
学科主题	Geology
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Geosciences, Multidisciplinary
研究领域[WOS]	Geology
关键词[WOS]	PARENT BODY ; METAMORPHIC HISTORY ; EUCRITE ; PETROGENESIS ; CHEMISTRY ; ORIGIN ; HOWARDITES ; PYROXENES ; TEXTURES ; CLASTS
收录类别	SCI
语种	英语
WOS记录号	WOS:000278516400008
公开日期	2011-11-23
内容类型	期刊论文
源URL	[http://159.226.72.40/handle/332002/1171]
专题	紫金山天文台_天体化学和行星科学实验室
作者单位	1.China Univ Geosci, Fac Earth Sci, Wuhan 430074, Peoples R China 2.Purple Mt Observ, Nanjing 210008, Peoples R China
推荐引用方式 GB/T 7714	Wang Linyan,Hsu Weibiao,Ma Changqian. Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History[J]. ACTA GEOLOGICA SINICA-ENGLISH EDITION,2010,84(3):528-542.
APA	Wang Linyan,Hsu Weibiao,&Ma Changqian.(2010).Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History.ACTA GEOLOGICA SINICA-ENGLISH EDITION,84(3),528-542.
MLA	Wang Linyan,et al."Petrology, Mineralogy and Geochemisty of Antarctic Mesosiderite GRV 020175: Implications for Its Complex Formation History".ACTA GEOLOGICA SINICA-ENGLISH EDITION 84.3(2010):528-542.