کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4728641 1640198 2015 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Geochemistry and geochronology of orthogneisses in Bode Saadu area, southwestern Nigeria and their implications for the Palaeoproterozoic evolution of the area
ترجمه فارسی عنوان
ژئوشیمی و ژئوشنگولوژی اوروگنسیس در منطقه بید سعدو، جنوب غربی نیجریه و پیامدهای آن برای تکامل پالئئو پروتزوئیک منطقه
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات زمین شناسی
چکیده انگلیسی


• The three suites of orthogneisses in Bode Saadu area carry metasedimentary xenoliths.
• Their protoliths are granodioritic, calc-alkaline and have magmatic arc affinity.
• LA-ICP-MS data give 2236 ± 29 Ma, 2228 ± 32 Ma and 2179 ± 28 Ma as ages of these gneisses.
• These indicate their emplacement during the early and later stages of the Eburnean orogeny.
• These data also suggest that the metasediments are at least Palaeoproterozoic in age.

Bode Saadu area, southwestern Nigeria is underlain by metasedimentary and metaigneous rocks including orthogneisses which have been intruded by largely undeformed granitic rocks of probable Pan-African (ca. 600 Ma) age. The metamorphic rocks have been subjected to several phases of both ductile and brittle deformation. Three suites of orthogneisses of granodioritic composition have been identified in the area, locally they contain xenoliths of metasediments. Geochemical analyses show that they are calc-alkaline, magnesian, metaluminous and possess the characteristics of granitoids emplaced in magmatic arcs.LA-ICP-MS in-situ dating of zircons in these orthogneisses has yielded upper Concordia intercept Palaeoproterozoic ages of 2236 ± 29 Ma, 2228 ± 32 Ma and 2179 ± 28 Ma. These indicate the times of crystallization of these rocks and attest to a long period of magmatism associated with the Eburnean orogeny in this part of Nigeria. The gneisses bear the imprints of several deformation events in the form of foliations, folds and shear zones. The geochronological data enable constraints to be placed on the timing of the development of some of these structures and also indicate that some of the metasedimentary units are at least of Palaeoproterozoic age.Similar Palaeoproterozoic orthogneisses have been documented in some other parts of southwestern Nigeria, in Central Hoggar area of the Tuareg Shield and in the Borborema Province of Brazil and support their correlation as part of West Gondwana.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of African Earth Sciences - Volume 109, September 2015, Pages 131–142
نویسندگان
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