کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9532106 | 1638794 | 2005 | 19 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Prolonged postcollisional shoshonitic magmatism in the southern Svecofennian domain - a case study of the Ã
va granite-lamprophyre ring complex
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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![عکس صفحه اول مقاله: Prolonged postcollisional shoshonitic magmatism in the southern Svecofennian domain - a case study of the Ã
va granite-lamprophyre ring complex Prolonged postcollisional shoshonitic magmatism in the southern Svecofennian domain - a case study of the Ã
va granite-lamprophyre ring complex](/preview/png/9532106.png)
چکیده انگلیسی
The Ã
va ring complex is one of four Paleoproterozoic postcollisional shoshonitic ring complexes in southwestern Finland. It is composed of ring dykes of K-feldspar megacryst-bearing granite, mingled in places with a shoshonitic monzonite, and lamprophyre dykes crosscutting all the rocks in a radial pattern. A survey was undertaken to trace the magma chamber beneath the ring complex to date it and measure some intensive parameters to clarify the crystallisation conditions at depth before the granite was emplaced in the upper crust. Mineral separates were extracted from the core zones of K-feldspar megacrysts in the granite, heavy mineral fractions (including zircons) from these separates were used for P-T assessment and age determinations, and the results were compared to data obtained from bulk rock samples. It appears that magma differentiation took place in a midcrustal magma chamber (at 4 to 7 kbar) possibly â¼30 Ma before the emplacement of the ring complex in the upper crust (deep assemblage â¼1790 Ma, shallow assemblage â¼1760 Ma). Relatively high activity of the alkalies and a low oxygen fugacity characterised the midcrustal chamber. The juvenile Svecofennian crust was invaded by shoshonitic magmas from an enriched lithospheric mantle over a long period of time. Some of these magmas were stored and differentiated in the middle crust before transportation to the upper crust. The results also show that coarse-grained granites may provide evidence for several magmatic evolutionary episodes, e.g., differentiation and crystallisation in different environments prior to final emplacement.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volume 80, Issues 1â4, March 2005, Pages 229-247
Journal: Lithos - Volume 80, Issues 1â4, March 2005, Pages 229-247
نویسندگان
Olav Eklund, Alexey Shebanov,