Manganese Rocks Research Articles

Testing of Electrical Properties and Synthesis of MnO2-Graphene Composites from Leaching Results of Manganese Rocks

This study aims to synthesize and test the electrical properties of the MnO2-graphene composite from the leaching of manganese rock. The test method is carried out by testing the electrical properties with the parameters, namely capacitance (C), current (I), voltage (V), resistance (R), and conductometer. Each tested three concentration variations, 0.25: 0.75, 0.5: 0.05, and 0.75: 0.5. Supporting parameters for testing use X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR). The results showed that the effect of varying the mass ratio of the MnO2-Graphene composite on the capacitance value was 192.3ꙡF in the variation of 0.25 gr: 0.75, meaning that the higher the concentration of the graphene carbon ratio, the higher the absorption capacity to store charge and electrical energy. For the variation of the voltage obtained by 353 mV at 0.25 gr: 0.75 variations, the current testing variation obtained a value of 13.6 mA at 0.25 gr: 0.75 variations, the variation on resistance obtained the lowest resistance value of 1.6 kΩ in the 0.25 gr variation: 0.75. The X-Ray Diffraction (XRD) test produces α manganese and graphene ranging from 6.8% to 93.2%. The Fourier Transform Infrared (FTIR) test produces Mn-O, CO, and OH bonds. Mn-O with wave numbers 479.44 cm-1, 1.618.35 cm-1, 1.877.47 cm-1, and 992.07 cm-1. CO with wave numbers 1104.27 cm-1, 1190.69 cm-1, and 1384.21 cm-1. OH with wave numbers 1438.44 cm-1 and 1627.70 cm-1 electrical storage medium.

The Effect of Physical and Electrical Properties on the Synthesis of Manganese Oxide Carbon from Leaching Rocks as Supercapacitor Electrodes

Manganese rocks are classified into manganese oxide, silicate, and carbonate. The research was carried out to synthesize carbon manganese oxide from the leaching of manganese rock and how to influence the physical and electrical properties of carbon manganese oxide from the leaching of manganese rock as the primary material for supercapacitor electrodes. The highest capacitance value produced was 65.3 µF in the composite ratio MnO2 : Carbon 0.25 g : 0.75. In the resistance test, the lowest resistance value was obtained in comparing the composite MnO2 : Carbon 0.25 g : 0.75 g with a resistance value of 1.92 kW.The highest inductance value obtained was 126.7mHon the composite ratio MnO2 : Carbon 0.75 g : 0.25 g. In the conductivity test, the highest value was obtained at 60.4 µS cm-1 in the composite ratio MnO2 : carbon 0.75 g : 0.25 g.

Testing of Electrical Properties and Synthesis of MnO2-Graphene Composites from Leaching Results of Manganese Rocks

This study aims to synthesize and test the electrical properties of the MnO2-graphene composite from the leaching of manganese rock. The test method is carried out by testing the electrical properties with the parameters, namely capacitance (C), current (I), voltage (V), resistance (R), and conductometer. Each tested three concentration variations, 0.25: 0.75, 0.5: 0.05, and 0.75: 0.5. Supporting parameters for testing use X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR). The results showed that the effect of varying the mass ratio of the MnO2-Graphene composite on the capacitance value was 192.3ꙡF in the variation of 0.25 gr: 0.75, meaning that the higher the concentration of the graphene carbon ratio, the higher the absorption capacity to store charge and electrical energy. For the variation of the voltage obtained by 353 mV at 0.25 gr: 0.75 variations, the current testing variation obtained a value of 13.6 mA at 0.25 gr: 0.75 variations, the variation on resistance obtained the lowest resistance value of 1.6 kΩ in the 0.25 gr variation: 0.75. The X-Ray Diffraction (XRD) test produces α manganese and graphene ranging from 6.8% to 93.2%. The Fourier Transform Infrared (FTIR) test produces Mn-O, CO, and OH bonds. Mn-O with wave numbers 479.44 cm-1, 1.618.35 cm-1, 1.877.47 cm-1, and 992.07 cm-1. CO with wave numbers 1104.27 cm-1, 1190.69 cm-1, and 1384.21 cm-1. OH with wave numbers 1438.44 cm-1 and 1627.70 cm-1 electrical storage medium.

Геохимия марганценосных отложений палеовулканогенных комплексов Южного Урала

Research subject . This article is devoted to the geochemistry of manganese deposits referred to the Devonian paleovolcanic complexes of the Magnitogorsk belt in the Southern Urals. Materials and methods . A series of studies was conducted using materials collected from the Kyzyl-Tash, Kazgan-Tash, Kozhayevskoye, Bikkulovskoye and Southern Fayzuinskoye deposits. The content of main elements and rare-earth elements was determined using the X-ray spectral fluorescent and ICP-MS methods, respectively. Results. It is shown that the values of indicator lithochemical modules in the manganese rocks under study are comparable to those in the modern metal- and ore-bearing sediments. The manganese rocks are characterized by low concentrations of rare-earth elements, as well as by a negative Ce anomaly (Ce/Ce* = 0.20-0.85) in their spectrum and an insignificant prevalence of heavy lanthanides over light ones. In terms of the REE spectrum configuration, the rocks under study are close to modern ferromanganese deposits of a hydrothermal genesis. Conclusion. The most probable source of Li, Be, Sc, Cr, Rb, Zr, Nb, Hf and Th in the manganese deposits was the detrital material of background sediments. Co, Ni, Ge, As, Mo and Sb, which concentration in the studied rocks is higher compared to that in the detrital component, are most likely to have been produced by hydrothermal solutions. Other rare elements could have been brought into the sediments through different routes. In general, according to the distribution of main, rare and rare-earth elements, the manganese rocks in the Southern Urals are comparable to the deposits of low-temperature hydrothermal sources, which developed within the arc system of the modern ocean. Our findings agree well with the concept of the hydrothermal-sedimentary origin of manganese deposits in the Southern Urals, thus supplementing this hypothesis by the data obtained using independent sources.

The Nadeiyakha Ore occurrence (Pai-Khoi, Russia): an example of ferromanganese metasediments in carbonaceous dolomitic shales

The paper presents the results of study of metalliferous (ferromanganese and manganese) rocks at the Nadeiyakha ore occurrence (Pai-Khoi) discovered in 2010. The metalliferous deposit represents a stratiform body lying conformably in the Upper Devonian carbonaceous siliceous and clayey–carbonate–siliceous shales. The ore bed occurs 180 m below the regional Famennian manganiferous rock association in Pai-Khoi. Discovery of the Nadeiyakha ore occurrence suggests the existence of an additional age interval of Mn accumulation within the Devonian sequence of this region. The studied metalliferous rocks display structures and textures typical of the metasedimentary rocks. In terms of composition, they are divided into two varieties: (i) ferromanganese (quartz–carbonate) rocks composed of quartz, dolomite, kutnahorite, rhodochrosite, siderite, and calcite; (ii) manganiferous (quartz–rhodochrosite–silicate) rocks composed of quartz, rhodochrosite, tephroite, sonolite, and pyroxmangite. The Nadeiyakha ore occurrence is marked by the abundance of dolomite in the ferromanganese rocks and host shales. In terms of the relationship of indicator elements (Al, Ti, Fe, and Mn), ferromanganese and manganese rocks are comparable with the recent metalliferous and ore-bearing sediments. The carbon isotope composition in carbonates (δ13C from –16.4 to –7.8‰ PDB) corresponds to authigenic carbonates related to the involvement of carbon dioxide produced during the microbial decomposition of organic matter at the stage of dia- and/or catagenesis. Geological and petrographic observations show that the ferruginous and manganiferous sediments were deposited synchronously with the terrigenous–carbonate–siliceous sediments. Fe and Mn could be sourced from hydrothermal solutions or interstitial diagenetic waters. The latter version seems to be more probable. Metals were accumulated in a depression-trap characterized by a periodic stagnation of bottom waters. Such sedimentation setting promoted the formation of paragenetic association of ferruginous and manganiferous sediments with the carbonaceous sediments and fostered reductive conditions during the postsedimentary mineral formation. Calcium carbonates contained in the primary rocks were subjected to dolomitization during the dia- or catagenesis. This process was promoted by the mobilization of Mg released during the transformation of clay minerals owing to the montmorillonite–illite transition. Iron and manganese carbonates were formed during the later replacement of oxides of Mn3+, Mn4+, and Fe3+. Crystallization of manganese silicates also started at early stages of lithogenesis and terminated during the regional metamorphism of metalliferous rocks.

Geochemistry and formation model of manganiferous rocks in jaspers of the South Urals

Specific features of the geochemistry of manganiferous siliceous rocks confined to Devonian volcanogenic complexes of the Magnitogorsk belt in the South Urals are discussed. It is shown that with respect to the distribution of the major petrogenic and rare earth elements, as well as base and rare metals, manganese rocks are comparable with rocks of the low-temperature hydrothermal sources in active volcanic zones of the World Ocean. Our results agree well with the existing concepts about the hydrothermal-sedimentary origin of manganese deposits in the South Urals and corroborate this hypothesis with new independently obtained data.

Mineralogy of low grade metamorphosed manganese sediments of the Urals: Petrological and geological applications

The paper describes mineralogy of the low grade metamorphosed manganese sediments, which occur in sedimentary complexes of the Pai Khoi Ridge and the Polar Urals and volcanosedimentary complexes of the Central and South Urals. The degree of metamorphism of the rocks studied corresponds to PT conditions of the prehnite–pumpellyite (deposits of Pai Khoi and Polar and South Urals) and green schist (deposits of the Central Urals) facies. One hundred and nine minerals were identified in the manganese-bearing rocks on the basis of optical and electron microscopy, X-ray diffraction, and microprobe analysis. According to the variations in the amount of major minerals of the manganese rocks of the Urals, they are subdivided on carbonate (I), oxide–carbonate–silicate (II), and oxide–silicate (III) types. Carbonates, various Mn2+-bearing silicates associated with oxides and carbonates, and braunite (Mn3+-bearing silicate) are the major Mn hosts in types I, II, and III, respectively. Because of the different oxidation state of Mn, the rocks of types I and II are termed as “reduced” and the rocks of type III, as “oxidized”. The formation of a certain mineralogical type of metamorphic assemblage is controlled by the content of organic matter in the primary sediments. The sequence type I→type II→type III reflects the decrease in the amount of organic matter in metalliferous sediments. Mineralogical data indicate that manganese in the primary sediments accumulated in a silicate form (MnSi gel, glass, etc). During diagenesis, the Mn–Si phase was transformed to neotokite with subsequent formation of caryopilite and further crystallization of pyroxmangite, rhodonite, tephroite, and other silicates due to reactions involving caryopilite. The hydrated Mn-silicates (caryopilite and/or friedelite) and the spatially associated parsettensite, stilpnomelane, and other minerals are the index minerals of the low grade metamorphism. Under PT conditions of prehnite–pumpellyite facies, nearly 70% of silicate minerals are hydrous. The metamorphosed Mn-bearing sediments are characterized by the low-temperature caryopilite (or tephroite-caryopilite-pyroxmangite±rhodonite) and the high-temperature caryopilite-free (or tephroite-pyroxmangite±rhodonite) facies. Their PT conditions correspond to zeolite and prehnite-pumpellyite (the low-temperature) and green schist and higher grade (the high-temperature) facies.

Manganese deposits in northeastern European Russia and the Urals: Isotope geochemistry, genesis, and evolution of ore formation

Based on new data on the lithology, mineralogy, chemistry, and isotopic composition of manganese carbonate ores and rocks at the deposits and occurrences in the Novaya Zemlya Archipelago, the Pai-Khoi, and the Urals, as well as using data from the literature, the main Phanerozoic basins of manganese deposition have been established in the geological history of Laurasia, Pangea, and Siberian paleocontinents. The formation conditions of manganese ore gradually changed from hydrothermal-sedimentary in the Middle Paleozoic to sedimentary-diagenetic in Mesozoic and Cenozoic. The ore was also formed under catagenetic conditions. Carbon of oxidized organic matter plays a substantial role in the formation of manganese carbonates.

Geochemistry and genetic model of the ore-bearing sediments of the Parnok ferromanganese deposit, Polar Urals

The Parnok ferromanganese deposit is confined to the black shales of the western slope of the Polar Urals. The deposit area is made up of weakly metamorphosed terrigenous-carbonate rocks formed in a marine basin at a passive continental margin. Ore-bearing sequence is composed of coaliferous clayey-siliceous-calcareous shales comprising beds and lenses of pelitomorphic limestones, and iron and manganese ores. The iron ores practically completely consist of micrograined massive magnetite. The manganese ores are represented by lenticular-bedded rocks consisting of hausmannite, rhodochrosite, and diverse manganese silicates. With respect to relations between indicator elements (Fe, Mn, Al, Ti), the shales are ascribed to pelagic sediments with normal concentrations of Fe and Mn, the limestones correspond to metalliferous sediments, ferruginous sediments are ore-bearing sediments, while manganese rocks occupy an intermediate position. It was found that the concentrations of trace elements typical of submarine hydrothermal solutions (As, Ge, Ni, Pb, Sb, Zn, etc.) in both the ore types are in excess of those in lithogenic component. At the same time, the indicator elements of terrigenous material (Al, Ti, Hf, Nb, Th, Zr, and others) in the ores are several times lower than those in the host shales (background sediments). REE distribution patterns in iron ores show the positive Eu anomaly, while those in manganese ores, the positive Ce anomaly. In general, the chemical composition of the ores indicates their formation in the hydrothermal discharge zone. The peculiar feature of the studied object is the manifestation of hydrothermal vents in sedimentary basin without evident signs of volcanic activity. Hydrothermal solutions were formed in terrigenous-carbonate sequence mainly at the expense of buried sedimentation waters. The hydrothermal system was likely activated by rejuvenation of tectonic and magmatic processes at the basement of sedimentary sequences. Solutions leached iron, manganese, and other elements from sedimentary rocks and transported them to the seafloor. Their discharge occurred in relatively closed marine basin under intermittent anaerobic conditions. Eh-pH variations led to the differentiation of Fe and Mn and accumulation of chemically contrasting ore-bearing sediments.

Evolution of manganese ore genesis in the earth’s geological history and the role of the biosphere

The formation of manganese rocks and ores occurred during the whole geological history of the Earth. Five metallogenic epochs (Early to Middle Proterozoic, Late Proterozoic, Early to Middle Paleozoic, Late Paleozoic, and Meso-Cenozoic) and 7 very important phases (Early, Middle, and Late Proterozoic, Early to Middle Paleozoic, Late Paleozoic, Late Mesozoic, and Meso-Cenozoic) can be distinguished. The phases of manganese ore genesis at many stratigraphic levels are closely related to the global climatic and tectonic reconstructions (the breakup of the continent of Gondwana and periods of glaciations and aridization) and biotic events (mass extinction of organisms). Based on carbon isotopic composition in manganese carbonates, participation of oxidized organic carbon is established.

Manganese deposits: Communication 1. Genetic models of manganese ore formation

Major regularities in the formation of manganese rocks and ores have been established on the basis of available published and original data. The proposed genetic classification of main manganese deposits (with model examples) is as follows: sedimentary-diagenetic (Nikopol, Bol’she-Tokmak; Ukraine), (volcanogenic) hydrothermal-sedimentary (deposits of the Atasui area, Kazakhstan; Magnitogorsk Trough, South Urals), epigenetic (catagenetic) (deposits of the Kalahari manganese ore field, South Africa; Usinsk deposit, Kuznetsk Alatau), and supergene (residual, infiltrational, cavern filling, and pisolitic deposits in India, Brazil, South Africa, and Australia). The results suggest the following conclusions: (1) all primary manganese rocks and ores at the known deposits are hydrothermal- and diagenetic-sedimentary formations of marine environments; (2) manganese concentrations achieve the size of deposits at postsedimentary stages of the initial manganiferous sediment and manganese rock transformation (diagenesis, catagenesis, and retrograde diagenesis); (3) indispensable participation of the isotopically light carbon dioxide related to the destruction of organic matter (OM) is a characteristic feature of manganese carbonate formation during diagenesis; and (4) the role of organic carbon in manganese ore formation becomes notable since early stages of Mn accumulation in the Precambrian sedimentary basins (terminal Archean-initial Early Proterozoic).

Mineralogy of metamorphosed manganese deposits of the South Urals

A mineralogical investigation of metamorphosed manganese rocks was carried out at ore deposits related to the Devonian volcanic complexes of the Magnitogorsk paleovolcanic belt of the South Urals. The mineralogical appearance of these rocks is determined by three consecutively formed groups of mineral assemblages: (1) assemblages occupying the main volume of orebodies and formed during low-grade regional metamorphism (T = 200−250°C, P = 2–3 kbar); (2) assemblages of segregated and metasomatic veinlets that fill the systems of late tectonic fractures; and (3) assemblages of near-surface supergene minerals. Sixty-one minerals have been identified in orebodies and crosscutting hydrothermal veinlets. The major minerals are quartz, hematite, hausmannite, braunite, tephroite, andradite, epidote, rhodonite, caryopilite, calcite, and rhodochrosite. The mineral assemblages of metamorphosed manganese rocks (metamanganolites) are characterized. Chemical compositions of braunite, epidote-group minerals, piemontite, pyroxenes, rhodonite, pyroxmangite, and winchite are considered. The bibliography on geology and mineralogy of the South Ural manganese deposits is given.

Tausonite and aluminum-fluorine titanite from the metamorphosed metalliferous sediments of the Triassic chert formation of the Sikhote Alin

Rare strontium mineral tausonite and a peculiar Al- and F-rich titanite variety were found in the metamorphosed metalliferous sediments of the Triassic chert formation of the Sikhote Alin, which are distinguished by the abundance of native elements, intermetallic compounds, and metal solid solutions, as well as the presence of diverse Au, Ag, and PGE minerals. Tausonite was documented in the manganese (metamorphosed siliceous-rhodochrosite) rocks of the Ol’ga mining district and in the “brown cherts” (siliceous rocks with manganese garnet and spessartine) of the Dal’nerechensk district, Primorye. It forms rather numerous grains 2–10 μm across usually occurring as inclusions in quartz or rhodonite. According to the electron microprobe analysis, in addition to Sr, Ti, and O, the mineral contains only Fe3+ (up to 0.20 a.f.u.). Aluminum-fluorine titanite was found in the “brown cherts” of the Dal’nerechensk district of Primorye (upper reaches of the Gornaya River). Its crystals are up to 200 × 200 μm in size. The recalculation of the microprobe analyses to crystal chemical formulas indicated that up to half of the Ti sites in the structure of this mineral may be occupied by Al. The decrease of the total positive charge owing to the Al3+ substitution for tetravalent Ti4+ is compensated for by a decrease in the total negative charge owing to F− substitution for O2− via the scheme Al3+F− → Ti4+O2−. The occurrence of considerable amounts of F substituting for oxygen in the titanite structure and, as a consequence (owing to the crystal chemical features of the mineral), the high Al content were related to the reduced character of the metamorphism of the metalliferous deposits.

Gold and platinum group metals in skarns of the Ol’ginsk and Dal’negorsk ore districts of Primorye and some issues of metallogeny of the southern Sikhote Alin region

The Triassic‐Jurassic carbonaceous sequence of Sikhote Alin includes metalliferous sediments represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues [3, 4], siliceous rocks with pyrophanite (“brown cherts”), tin‐iron ores, “ilmenite‐ biotite‐feldspar” (metamorphosed clayey) rocks, and “itabirites.” They are characterized by high contents of Au, Ag, Pt, and Pd [2] and the ubiquitous presence of minerals of these elements. Hydrothermally altered sandstones, as well as siliceous‐clayey and siliceous rocks, which are associated with syngenetic metalliferous rocks, contain grains of gold, silver, argentite, platinum, Pd-platinum, itenbohaardite, and other minerals of noble metals. It should be mentioned that identifications of all minerals mentioned in this paper have been confirmed by microprobe analyses. Another type of hydrothermal ores is represented by Mn-rich amphibole‐pyroxene rocks that contain native gold, silver, Pdplatinum, and other minerals of gold, silver, and platinum group metals (PGM). Hydrothermal ores are products of the regeneration of metalliferous rocks due to the evolution of Late Cretaceous granitoid massifs. The amphibole‐pyroxene rocks formed after calcareous sandstones, which are probably of Late Triassic age [3]. The southern Sikhote Alin region incorporates numerous Late Cretaceous skarn and vein (cavity-filling) deposits of lead, zinc, silver, tin, tungsten, and iron. Skarns are characterized by high concentrations of Mn derived from manganese rocks [1]. Similarly as other metalliferous rocks, the manganese rocks are enriched in Pb, Zn, Ag, Sn, W, and Fe. Hydrothermal deposits of these metals define the metallogenic profile of the southern Sikhote Alin region. Manganese and other metals mentioned above were probably derived from metalliferous rocks of the Triassic‐Jurassic carbonaceous sequence. The metalliferous rocks and associated hydrothermal rocks contain Au and PGM. For example, these metals are concentrated in amphibole‐pyroxene rocks of the Shirokaya Pad area of the Ol’ginsk district. These rocks are analogues of the adjacent manganiferous

Metalliferous sediments of the Triassic cherty formation in the Ol’ga ore district of primorye: Tin-noble metal ores of a new genetic type

The Triassic cherty formation of Sikhote Alin [1] hosts metalliferous deposits. They are commonly represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues (primarily, consisting of Mn-silicates and aluminosilicates) with high concentrations of Ga, Au, Pt, Pd, and other metals [3]. In the Ol’ga district, the metalliferous deposits are also represented by chocolate-brown siliceous rocks (hereafter, brown cherts) and tin‐iron ores. The metalliferous deposits occur in the Middle‐ Late Triassic siliceous‐clayey sequence. They make up at least one ore-bearing unit (thickness of 5 m or more) represented by brown cherts with a manganese rock bed near the upper contact. The overlying tin‐iron ore bed varies from tens of centimeters to a few meters in thickness. Judging from locations of native exposures, talus, and alluvial fragments, the ore-bearing unit is developed over an area of no less than 20 km 2 (Fig. 1). The manganese rocks are composed of rhodonite, pyroxmangite, and spessartine with a maximum V 2 O 3 content of 0.20 wt % [2, 4]. The rocks contain kanoite, tephroite, manganactinolite, dannemorite, tirodite, pyrosmalite, pyrophanite, hubnerite, scheelite, native silver, native gold, minerals of the cobaltite‐ gersdorffite series, pentlandite, millerite, violarite, tetradymite, tellurobismuthite, and other minerals. The manganese rocks also include Au (up to 35 g/t), Pt (0.08‐ 0.33 g/t), Zn (up to 5.97 wt %), Cu (up to 0.64 wt %), Ni (up to 0.14 wt %), and Co (up to 0.10 wt %) [3]. Nearly all polished samples contain native silver dissemination up to 20 µ m in diameter. Gold grains ( n mm in size) extracted by the acid treatment of manganese rocks are characterized by a high grade of fineness

Gallium, gold, and platinum group metals in manganese rocks of Southern Sikhote Alin

Gallium, gold, and platinum group metals in manganese rocks of Southern Sikhote Alin

Sodic metasomatism in the Palaeoproterozoic Hotazel iron‐formation, Transvaal Supergroup, South Africa: implications for fluid–rock interaction in the Kalahari manganese field

AbstractPetrological and geochemical evidence is presented on the occurrence of aegirine in the Palaeoproterozoic Hotazel iron‐formation, which hosts the giant manganese deposits of the Kalahari manganese field, South Africa. The mineral has an essentially pure Na end‐member composition and occurs sporadically in iron‐formation immediately bordering the manganese ore beds. The development of aegirine appears to have taken place due to the action of late‐infiltrating, saline hydrothermal fluids at the expense of a pre‐existing, binary quartz–hematite assemblage. It is proposed that such a process would have overprinted (and therefore post‐dated) a spatially more extensive, low‐temperature alteration event which brought about thorough carbonate leaching, oxidation and residual enrichment of metals in the Hotazel iron–manganese rocks.

The mineralogy and petrography of the ferruginous manganese rocks at Mankwadzi, Ghana

Outcrops of a banded ferruginous manganiferous rock occur at Mankwadzi village 8 km west of Winneba, Ghana. The rock has variously been referred to as gondite and banded iron formation. The very fine-grained texture and the intense alteration of the rock make the resolution of its petrographic nature by ordinary transmitted and reflected light microscopy rather difficult. The present investigations provide petrologic and chemical data from microprobe analyses of the minerals within the manganiferous horizons and whole rock analyses of the country rocks. Mineral compositions were calculated and rock classifications determined from the data so obtained. The host rocks appear to have been deposited in a sub-aqueous environment during Birimian times. They include erosion products made up of siliceous material from terrigenous sources and mafic material probably of submarine volcanic origin. Chemically, the rock compositions suggest andesitic and tholeiitic basaltic parentage. The Mn/Fe ratio of 3:1 of the Mn horizons lies within the range (0.1 < Mn/Fe < 10), which is typical of “Sedex” deposits. Also, the contents of transitional metals (notably Co, Ni, and Zn) in the Mn horizons are high and point to probable derivation from marine sources. The Cu content is, however, low. The Fe content is constant in both the host rocks and the Mn horizons, whilst the Mn/Fe ratio rises from an average of less than 0.02 in the host rocks to over 3.00 in the manganiferous horizons indicating that while the Fe may be indigenous, the Mn appears foreign and was probably introduced from external source(s). Although regional metamorphism is up to garnet-amphibolite facies, the effects of retrograde metamorphism are recognised in all the rocks. The presence of pyroxene and pyroxmangite/rhodonite in the manganiferous rocks is enigmatic since these minerals could be either primary igneous precursor minerals or products of a higher temperature metamorphic event distinct from the pervasive regional amphibolite facies conditions. The field relationship between the manganiferous horizons in the quartzites and an adjacent mafic intrusion (now metamorphosed to hornblendite) is intriguing and the arguments for and against possible genetic links between the Mn mineralization and intrusion are discussed. The study thus shows that the mineral occurrence at Mankwadzi is Mn rather than Fe mineralization. This Mn mineralization is of limited area extent and is restricted to the contact between the late mafic intrusion and the quartzites. It also shows that this contact is a probable locus for similar manganese occurrences and should be the target for manganese exploration within the Birimian, especially within the Winneba–Kibi volcanogenic greenstone belt of Ghana.