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Geochemistry and Petrogenesis of Basic and Ultrabasic Rocks Elogo Complex in Ivindo Archean Block (Congo Craton): Geodynamic Implications

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Open Journal of Geology 2023年第2期13卷 107-135页

作者： Nelson Lekeba Makamba Vicky Tendresse Télange Bouenitela Ulrich Verne Matiaba-Bazika Florent Boudzoumou Geodynamics Laboratory Faculty of Science and Technology Marien Ngouabi University Brazzaville Republic of the Congo Department of Geosciences National Institute for Research in Exact and Natural Sciences Brazzaville Republic of the Congo

The Elogo complex is a greenstone belt portion located on the Eastern edge of the Archean Congo craton at the junction with the Paleoproterozoic to Neoproterozoic Sembe Ouesso basin. This study was carried out on this complex to determine the context of the placement of basaltic rocks. Metaluminous tholeiitic basalts (basic and ultrabasic), calc-alkaline basalts, andesitic basalts, and peraluminous calc-alkaline dacites represent greenstones. tholeiitic and calc-alkaline basalts come from deep enriched and depleted mantle sources, including garnet in fusion residues [Al2O3/TiO2 > 16 (16.5 to 35.12) and in some samples between 12.45 to 14.48;CaO/Al2O3 1 (1.04 to 1.35) in ten samples and (Gb/Yb)PM > 1]. The calc-alkaline dacites come from a shallow depleted mantle source [Al2O3/TiO2 > 16;CaO/Al2O3 1]. tholeiitic and calc-alkaline basalts have a negative Rb, Ba, Ce, and Nb anomaly without negative Ti anomaly, positive Ta, Pb anomalies, and a lack of significant REE [(La/Yb)n = 0.36 to 0.97 and 1 to 2.15;(Ce/Yb)n = 0.27 to 0.96 and 1.04 to 1.72, respectively] fractionation. High Nb/Th (2 to 10) and Nb/U (1.82 to 26) ratios and low La/Ta (5 to 27) ratios are characteristic of divergent margin magmatic sources. tholeiitic and calc-alkaline basalts correspond to an extensive back-arc basin-type tectonic setting. Calc-alkaline andesitic basalts and dacites show positive Ba, U, Th, K, La, Ce, Pb, and Li anomalies and negative Nb, Ta, and Ti anomalies reflecting crustal contamination and hydrothermal alteration in a compressive tectonic context as a volcanic arc in a subduction regime marking the interruption of the meso-neoarchean Elogo’s opening. Elogo’s opening and closing are probably associated with the emplacement of the greenstone of the meso-neoarchean Gabon Belinga group and the relics of the Mesoarchean greenstones of the Cameroun Ntem complex.

关键词： Elogo Greenstone Archean tholeiitic Andesitic Basalts Dacites Magma Source

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Petrochemical Characterization of Two Distinct Types of Dolerites from Bafoussam Area, West Cameroon

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International Journal of Geosciences 2013年第8期4卷 1131-1144页

作者： Gus Djibril Kouankap Nono Pierre Wotchoko Sylvestre Ganno Divine Ngong Njinchuki Jean Paul Nzenti 1Department of Geology HTTC University of Bamenda Bamenda Cameroon 2Laboratory of Petrology and Structural Geology Faculty of Science University of Yaoundé I Yaoundé Cameroon Department of Geology HTTC University of Bamenda Bamenda Cameroon Economic Geology Unit Department of Geology University of Buea Buea Cameroon Laboratory of Petrology and Structural Geology Faculty of Science University of Yaoundé I Yaoundé Cameroon

Two petrochemical types of doleritic dykes have been distinguished in Bafoussam area: 1) the olivine-bearing dolerites which are the most representative are dark green, showing characteristics of alkaline basalts and, 2) the calcite-bearing dolerites are grayish green, showing characteristics of tholeiitic basalts. The studied dolerites are less differentiated (1 FeOt/MgO 2);they present the evolution of a subalkaline magma following a calc-alkaline series (alkaline dolerites) and the tholeiitic series (tholeitiic dolerite). The chondrite normalized multielement spider diagrams of all the dolerites show a pronounced depletion in Ba, Th, and enrichment in Rb. Their geotectonic context is inferred to be intraplate and the contrast between the two types is probably due to a diverse source: crustal source for calcite-bearing dolerites and mantle source for olivine-bearing dolerites.

关键词： Doleritic Dyke Petrochemical Alkaline tholeiitic Intraplaque Bafoussam

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Ediacarian Volcanic Rocks and Basic Dikes from the Lac Ifni Sector of the Central High Atlas Mountains:Petrographic Studies and Clinopyroxene Chemical Composition

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地学前缘 2009年第S1期16卷 198-198页

作者： Sad Belkacim M.Ikenne S.Arai H.Gahlan A Ahmed Hassan Y.Ishida Laboratoire de Géologie Appliquée Et Géo-environnement Faculte Des SciencesUniversité Ibn Zohr Department of Earth Sciences Kanazawa University Department of Geology Faculty of ScienceAssiut University Department of Geology Helwan University

The Ediacarian volcanic series from the Lac Ifni sector are composed of a large variety of rocks from basalts and rhyolites to intermediates facies such as andesites,rhyodacites and *** these rocks are intruded by dol... 详细信息

关键词： High Atlas Mountains Anti Atlas Mountains volcanism Ediacarian clinopyroxene ICP-MS Laser orogenic calc-alcaline tholeiitic

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