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Preliminary Report on the Paleoproterozoic metasediments Genesis and Features of the Banfora Belt Western Burkina Faso (West Africa Craton)

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International Journal of Geosciences 2025年第1期16卷 1-19页

作者： Hermann Ilboudo Bernadin Gnamou Wilfried Antoine Bassou Toe Marc Ephrem Allialy Laboratoire Gosciences et Environnement Dpartement des Sciences de la Terre Universit Joseph KI-ZERBO Ouaga Burkina Faso Laboratoire de Gologie du Socle et de Mtallognie UFR STRM Universit Flix Houphout-Boigny de Cocody Abidjan Abidjan Cte dIvoire

Metasedimentary rocks of the Banfora belt are examined for their petrography geochemistry and genesis. The main formations are pelite metapelites sandstone, and metagraywackes. The first ones show a fine interlocking layering with unclear graded bedding in the sandstone compared to the metapelites, while the metagraywackes show a clearly discordant graded bedding of light grey to light pink color. The low SiO2/Al2O3 ratios (3.67 to 6.60) suggest their low sedimentary maturity. The metapelites and sandstone-pelites show moderate Na2O/K2O values (10.13 - 22.69), indicating moderate chemical maturity;in contrast, the metagraywackes show low Na2O/K2O values (1.94 - 5.80) suggesting low chemical maturity. The metapelites, sandstone-pelites and metagraywackes have Rb/Sr ratios of 0.866 - 0.004 and 0.173 - 0.607 respectively, indicating a moderate to low degree of chemical alteration. The chemical alteration index (CIA = 58 - 83) and the plagioclase alteration index (PIA = 53 - 81) suggest weak to moderate alteration of the source rocks. This alteration is different from simple alteration as the sole control of chemical composition, but is associated with metasomatism. The metapelites sandstone shows a mixture of mafic and intermediate igneous sources, which indicates that the protoliths could be basalts and andesites, but the metagraywackes would be derived from the erosion of a mixture of andesitic to granitic rocks. The studied rocks were generated from young undifferentiated to differentiated arcs. They are of low to moderate sedimentary and chemical maturity.

关键词： metasediments Banfora Belt Source Alteration Geotectonic Environment

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Coesite in metasediments from the Muzhaerte valley, southwestern Tianshan

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Science Bulletin 2019年第2期64卷 78-80页

作者： Zeng Lü Lifei Zhang Ji Yue Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University

The sediments,including calcareous,siliciclastic and volcanoclastic,usually occupy>90%in volume of an accretionary complex and thus,if involved in subduction zones,their maximum return depths(i.e.,peak pressures)are fundamental to unravel the geodynamic processes during the convergence of plates[1].As a unique example of accreted complex returned from sub-arc depths(>90 km)worldwide.

关键词： UHP southwestern Tianshan Coesite in metasediments from the Muzhaerte valley

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New detrital zircon U-Pb ages from BIF-related metasediments in the Ntem Complex (Congo craton) of southern Cameroon, West Africa

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Natural Science 2013年第7期5卷 835-847页

作者： Nelson N. Chombong Emmanuel C. Suh Charles D. C. Ilouga Department of Earth Sciences University of Yaoundé I Yaoundé Cameroon Economic Geology Unit Department of Geology University of Buea Buea Cameroon

Banded Iron Formations (BIFs) were formed by contemporaneous events of active sediments supply and the venting of a hydrothermal fluid source at the Mid-Ocean-Ridge. BIFs within the Ntem Complex at the northern edge of the Congo Craton are intercalated with metasandstones and siltstones. SHRIMP U-Pb analysis on detrital zircons obtained from these metasediments gave variable ages from over 3000 Ma to 1000 Ma with the maximum age of deposition clustered around 1200 Ma and the peak of deposition at 1800 Ma. This age range suggested that the sub-basin was opened sometime in the Archean and remained active up till the Neoproterozoic. Zircons with Archean ages have a provenance linked to the charnockitic suite and the high-K granites within the Ntem Complex. The Paleoproterozoic ages are attributed to clastic inputs from the neigbouring Nyong Series west of the Ntem Complex. Also the peak of deposition in the Proterozoic could probably be explained by the globally recognized intense crust-forming processes in the Early Proterozoic time. The provenance of the younger Neoproterozoic ages is tied to various lithologies within the northern mobile belts of the Adamawa-Yade massifs and correlates with Neoproterozoic sedimentation ages in the Yaoundé, Lom and Poli series. The Neoproterozoic ages obtained are comparable to those obtained from metasediments of the Amazonian Craton and provide evidence of Pre-Gondwana assemblage of the Congo and the S?o Francisco Cratons.

关键词： BIFs metasediments Ntem Complex SHRIMP U-Pb Age Detrital Zircons

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Tracing the Origin of Metasedimentary Rocks in the Tortiya Diamond Region (Northern Côte d’Ivoire)

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Open Journal of Geology 2023年第12期13卷 1271-1290页

作者： Tessia Miryam Adingra Martial Pohn Koffi Koffi Yao Augustin Houssou Nestor Allialy Marc Ephrem Kouassi Brice Roland Félix Houphouë t-Boigny University of Abidjan Abidjan C&#244te d’Ivoire Peleforo Gon Coulibaly University of Korhogo Korhogo C&#244te d’Ivoire

Metasedimentary rocks from the Tortiya diamondiferous region (northern Côte d’Ivoire), located in the Ivorian Paleoproterozoic domain, were analyzed with the aim of identifying their different petrographic facies, constraining their provenance and tectonic environment, and assessing the effects of sedimentary processes and weathering on the signature of their source rocks. These analyses were carried out with a view to helping trace the origin of Tortiya diamonds, which are generally hosted in these metasediments. Major and trace element geochemical data reveal that these samples are characterized by negative Eu anomaly values, low to moderate weathering index values and a high compositional variation index (ICV). These results led to the definition of these metasediments as immature sediments potentially originating from rapid erosion and sediment deposition from local sources. Chemical alteration index (CIA) values and Al2O3-(CaO* + Na2O)-K2O composition space suggest low to medium degrees of meteoric alteration of the parent rock. These rocks therefore show poorly differentiated compositions from the parent rock and poor sediment sorting. Geochemical data and ratios of immobile elements, e.g. Al2O3/TiO2, Cr/Th, Eu/Eu* and (La/Yb)n, indicate that the clastic materials derive mainly from felsic to intermediate sources. Sedimentary tectonic discrimination diagrams demonstrate that most of the samples from the Tortiya diamond-bearing region were deposited on an active continental margin or in a continental arc-island environment. Although this region has a long history of diamond mining, its petrogenesis remains unresolved, and this petrogeochemical work is a step towards initiating scientific research in the area.

关键词： Petrography Geochemistry metasediments Tortiya Ivory Coast

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Mineragraphic Study of Manganese Ore Deposits of Kandri, Mansar, Beldongri and Satak Mines, Nagpur District (Maharashtra) Central India

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International Journal of Geosciences 2014年第7期5卷 710-727页

作者： Talat Jawed F. N. Siddiquie Department of Geology Aligarh Muslim University Aligarh India

In Nagpur, M.P.-Maharashtra Manganese Belt is exposed which is part of Sausar Belt. In Nagpur, four manganese mines viz Mansar, Kandri, Beldongri and Satak are selected for the ore microscopic study. These mining areas are situated in that part of Central India which are highly deformed and metamorphosed and are characterised by high grade amphibolite facies to low grade greenschist facies. The Precambrian manganese ore deposits of Nagpur are formed by the metasediments of Sausar belt which is rich in manganese sediments. The manganese ores of the study area are co-folded with distinct rock types i.e. “gondites” and predominantly composed of a mixture of braunite, bixbyite, hausmannite, hollandite, jacobsite, vredenburgite, pyrolusite, cryptomelane and psilomelane. The dominant rocks are tirodi migmatitic gneiss, argillaceous and calcareous rock types. This paper discusses the mineralogy of the manganese ores of Kandri, Mansar, Satak and Beldongri. After the careful assessment of mineralogy, texture and paragenesis of the manganese ore of the study area, it has been concluded that the manganese ores of the study area are formed by the multiple processes i.e. metamorphism and supergene enrichment. These supergene enrichments are evidence of colloidal influx. Occurrence of free braunite, free hausmannite and free jacobsite indicates the high grade metamorphism. Pyrolusite, rhodonite, and psilomelane-cryptomelane are formed by supergene enrichment. The presence of lamellar twinning in braunite indicates about shear pressure. In this area the different manganese mineral assemblages and their textures suggest about the occurrence of different metamorphic activity and depositional environment. The texture and paragenesis of manganese ore of the study area are discussed here.

关键词： Sausar Belt Precambrian metasediments Manganese Mineralization Central India

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