کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9524460 1635186 2005 17 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Kamafugitic diatremes: their textures and field relationships with examples from the Goiás alkaline province, Brazil
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
Kamafugitic diatremes: their textures and field relationships with examples from the Goiás alkaline province, Brazil
چکیده انگلیسی
Kamafugitic rocks intruded the Precambrian basement and Phanerozoic sediments at the northeast border of the Paraná basin as part of the Late Cretaceous Goiás alkaline province (GAP). Plutonic complexes dominate the north of the province, whereas lavas and pyroclastic rocks prevail in the south. The central GAP is characterized by kamafugitic diatremes, which may crop out continuously for up to 850 m and consist of a central breccia body, surrounded and overlain by lava flows and crosscut by dykes. The breccias contain some special spheroidal juvenile fragments-namely, accretionary and armored lapilli, frozen droplets, spinning droplets, and wrapped fragments-whose textural and mineralogical aspects are described in detail. Irregularly shaped tuff pockets that occur within the breccias contain textures and structures similar to those of subaerial surge deposits and formed in confined, high gas to solid+liquid ratio domains in the conduit. Diatreme emplacement affected the country rock through thermal metamorphism, development of columnar jointing, and formation of peperite-like mixtures. There is no evidence of phreatomagmatic activity in the diatremes, and CO2, rather than H2O, seems to have been the major volatile component of the kamafugitic magmas. This finding implies that features such as accretionary lapilli and peperites are not exclusively associated with H2O-dominated processes.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of South American Earth Sciences - Volume 18, Issues 3–4, March 2005, Pages 337-353
نویسندگان
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