Late sodic metasomatism evidences in bimodal volcanic rocks of the Acampamento Velho Alloformation, Neoproterozoic III, southern Brazil
نویسندگان
چکیده
منابع مشابه
A study of different zoning types in clinopyroxenes of sodic and potassic alkaline volcanic rocks from North Lahrud, NW Iran
Clinopyroxene phenocrysts and microphenocrysts in potassic and sodic Eosen alkaline volcanic rocks from the northern Lahrud (NW Iran) record various stages in the crystallization and evolution history of the alkaline melt as well as its origin. The rock series hosting the clinopyroxene phenocrysts is phonolitic tephrite and tephritic phonolite composition. Theses rocks generally show porphyriti...
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Around The Karik village, east of Meiduk mine, Eocene volcanic rocks (andesitic basalt, andesite, dacite and rhyolite) and pyroclastic rocks (agglomerate and tuff) are exposed. These rocks are cut by several andesitic dikes. The major textures in the volcanic rocks are porphyritic and flow textures. The minerals such as plagioclase, alkali feldspar, quartz, pyroxene, amphibole, biotite and opaq...
متن کاملPetrology and Geochemistry of the Eocene Volcanic Rocks in the West of Sechangi, Lut Block
The Eocene volcanic rocks exposed in the NW Sechangi area of Lut block, include pyroclastic deposits and lavas. These volcanic rocks are basalt, basaltic andesite, andesite, andesite-trachyandesite, trachydacite, dacite and rhyolite-ignimbrite in composition. Based on our field observations, the volcanic rocks erupted in four stages in the aquous to subaerial environments. The volcanic rocks ar...
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Petrography and chemistry of minerals showing that Eocene alkaline volcanic rocks in southwestern of Germi (Talesh zone, NW Iran) mostly have basaltic composition. Mineralogically these rocks are composed of diopsidic clinopyroxene and labradoritic plagioclase phenocrysts. The microlithic and glassy groundmass composed of sanidine, clinopyroxene, biotite, pargasitic amphibole and magnetite asso...
متن کاملGeochemistry and petrogenesis of post-collisional ultrapotassic syenites and granites from southernmost Brazil: the Piquiri Syenite Massif.
The Piquiri Syenite Massif, southernmost Brazil, is part of the post-collisional magmatism related to the Neoproterozoic Brasiliano-Pan-African Orogenic Cycle. The massif is about 12 km in diameter and is composed of syenites, granites, monzonitic rocks and lamprophyres. Diopside-phlogopite, diopside-biotite-augite-calcic-amphibole, are the main ferro-magnesian paragenesis in the syenitic rocks...
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ژورنال
عنوان ژورنال: Anais da Academia Brasileira de Ciências
سال: 2007
ISSN: 0001-3765
DOI: 10.1590/s0001-37652007000400012