کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4724692 | 1639736 | 2006 | 25 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Growth of Archaean crust in the Kuhmo district, eastern Finland: U-Pb and Sm-Nd isotope constraints on plutonic rocks
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Neoarchaean plutonism in the Kuhmo district in eastern Finland, Karelia, includes tonalites, sanukitoids, leucocratic granodiorites, and leucogranites. A U-Pb (SIMS and TIMS) study of zircons and titanites places age constraints on this plutonic activity, and whole-rock Sm-Nd isotopes are used to characterise source variation. U-Pb results indicate that the tonalites were emplaced during at least three separate periods; >2.81, â¼2.78, and 2.76-2.74Â Ga. The initial ÉNd values vary from +0.3 to +2.2, and suggest no major involvement of significantly older crust in the genesis of tonalites. The tonalites were followed by 2.74-2.70Â Ga (possibly also 2.68Â Ga) sanukitoids with initial ÉNd values of â0.7 to 1.2. Close temporal relations between the â¼2.74Â Ga tonalites and sanukitoids indicate that their genesis may be linked. Subsequent leucocratic granodiorites and leucogranites were emplaced at 2.70-2.68Â Ga and commonly contain inherited zircons. The initial ÉNd values of these granodiorites and granites vary from +1.1 to â3.4, indicative of multiple magma sources. The general decrease in initial ÉNd values with decreasing age demonstrate progressive recycling of pre-existing crust, thus stressing the importance of crustal recycling as a process in forming the leucocratic granitoid rocks. Overall, the Archaean plutonic rocks of the Kuhmo district are temporally similar to those in the adjacent Russian Karelia, suggesting that 2.83-2.68Â Ga was one of the most extensive periods of crustal growth throughout the Karelia craton.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Precambrian Research - Volume 146, Issues 3â4, 10 May 2006, Pages 95-119
Journal: Precambrian Research - Volume 146, Issues 3â4, 10 May 2006, Pages 95-119
نویسندگان
Asko Käpyaho, Irmeli Mänttäri, Hannu Huhma,