کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4728359 1640189 2016 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Mineralogy and geochemistry of laterites developed on chlorite schists in Tchollire region, North Cameroon
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات زمین شناسی
پیش نمایش صفحه اول مقاله
Mineralogy and geochemistry of laterites developed on chlorite schists in Tchollire region, North Cameroon
چکیده انگلیسی


• Tchollire chlorite schists are felsic in Doudja site and mafic in Fimbe site.
• Soils on mafic chlorite schists are thicker than those on felsic chlorite schists.
• Chlorite decreases from chlorite schist parent rocks towards the surface horizons.
• MgO and CaO is higher in Fimbe soils than in Doudja soils.
• Cr, V, Cu, Ba, Zn, Ni, Sr have high contents and low REE in Tchollire materials.

Laterites developed from the weathering of chlorite schists have been studied in Tchollire region, North Cameroon. They include two profiles: a 5.5 m depth profile in Doudja site and a 12.3 m profile in Fimbe site.The chlorite schists have a lepidoblastic to lepidogranoblastic texture and are mainly composed of chlorite, muscovite, biotite, feldspars and quartz but that of Fimbe is marked by the presence of amphibole. It is felsic with a high SiO2 content (67%) and low Fe2O3 (5.8%) and MgO (2.4%) contents in Doudja site but has a lower content of SiO2 (46%) in the Fimbe site where it is mafic with higher contents in Fe2O3 (12.4%) and MgO (6.3%). The chlorite schists of Doudja show high contents in Zr, Sr, Ta, with moderate contents in Cr, V, U and Zn. That of Fimbe is particularly rich in Cr, V, Ni, Sr and Zn with a moderate Zr content. All chlorite schists have high barium contents (270–393 ppm) with LREE-enrichment.The soils are yellowish and, from bottom to top, are composed of a coarse saprolite, fine saprolite, loose clayey horizon and an organo mineral horizon. The main minerals are chlorite, muscovite, biotite, feldspars, quartz, smectites, vermiculite, kaolinite, hematite and goethite. In Doudja, SiO2 mainly decreases from the bottom to the top of the profile while, Al2O3 and Fe2O3 generally increase; in Fimbe, SiO2 and Al2O3 increase up the profile but Fe2O3 decreases; the general high Fe and corresponding decrease in Mg contents in the soils show that the smectite formed is nontronite. Chromium, V, Cu, Ba and Sr show high contents in the two studied profiles but Zr, U and Ta is higher in Doudja than in Fimbe. Copper generally has high contents in the loose clayey and organo mineral horizons. Nickel is higher in the Fimbe profile and probably issued from the Ni-rich mafic protolith. SiO2 has positive correlations with K2O, Zr, Li and Rb. Correlations of SiO2 with CaO, TiO2 and Cr are negative. Al2O3 and Fe2O3 have a positive correlation with Pb. Doudja soil samples mostly show positive Ce and Eu anomalies. The (La/Yb)N ratio is low in Tchollire soils and indicative of the low degree of lanthanide fractionation.Mass balance assessment reveals that most of the elements in Doudja have accumulated while those from Fimbe have been mostly leached. Calcium in particular has accumulated in both profiles indicating that the smectites formed may have incorporated the Ca primarily on the exchange sites.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of African Earth Sciences - Volume 119, July 2016, Pages 264–278
نویسندگان
, , , , ,