Silicate facies iron-formation of the Egbe-Isanlu Palaeoproterozoic schist belt, southwest Nigeria

被引:8
作者
Annor, AE
Olobaniyi, SB
Mucke, A
机构
[1] FED UNIV TECHNOL,DEPT GEOL,MINNA,NIGERIA
[2] UNIV GOTTINGEN,MINERAL PETROL INST,D-37077 GOTTINGEN,GERMANY
来源
JOURNAL OF AFRICAN EARTH SCIENCES | 1997年 / 24卷 / 1-2期
关键词
D O I
10.1016/S0899-5362(97)00025-0
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Field, petrological, mineralogical and geochemical data on the Egbe-Isanlu Palaeoproterozoic schist belt are presented, high-lighting the main features of a silicate facies iron-formation, which hitherto had been described as a metamorphosed, impure sandstone. The iron-formation is relatively thin (max. 15 m) and concordantly interbedded with schistose, semi-pelitic, amphibolitic and talcose host rocks, with which it shares a common polyphase tectonometamorphic history. The last of these is the Pan-African overprint, during which time the iron-formation was locally silicified. The main constituent minerals are garnet (almandine-spessartine solid solution), amphibole (Mn and Ca bearing grunerite-cummingtonite solid solution), quartz and ilmenite. Magnetite was not observed. Geochemical data show that the iron-formation and metasediments are of different origins. The silicate facies iron-formation of Isanlu belongs to the Algoma-type and was derived by the metamorphism of a volcano-exhalative-sedimentary protolith, probably during Eburnian times. (C) 1997 Elsevier Science Limited.
引用
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页码:39 / 50
页数:12
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