 | | Journal (article/letter/editorial) | | GARNET FROM A BARITE-RICH ROCK, OTJOSONDU FERROMANGANESE DEPOSIT, NAMIBIA: THE FINGERPRINT OF OXIC SEA WATER...Geological Society of South Africa ABSTRACT Otjosondu, a Neoproterozoic ferromanganese deposit located...located about 130 km north-east of Okahandja, Namibia, has a garnetbraunite-barite rock containing ~32 weight...formed in oxic sea water. The REE patterns of the Otjosondu garnet drastically differ from those found in...absence of cerium anomalies in the latter. The Otjosondu garnet is thought to be metamorphosed hydrothermally |  | | Report (issue) | | Ia3d: a = 11.81 Z=8 X-ray Powder Pattern: Otjosondu, Namibia. 2.62 (100), 1.574 (100), 2.92 (90), 2.39...Total 100.75 101.3 31.4 29.0 8.5 (1) Otjosondu, Namibia; by electron microprobe; corresponds to (Mn1:96...deposit (Otjosondu, Namibia); in an iron formation (Wabush district, Canada). Association: Pyrolusite, aegirine...Balaghat district, Madhya Pradesh, India. At Otjosondu, Namibia. In the Wabush district, near Labrador City...Vermaas, F.H.S. (1952) Manganese-iron garnet from Otjosondu, South-West Africa. Mineral. Mag., 29, 946{951 |  | Amthauer, Georg, Katz-Lehnert, Kerstin, Lattard, Dominique, Okrusch, Martin, Woermann, Eduard (1989) Crystal chemistry of natural Μn3+-bearing calderite-andradite garnets from Otjosondu, SWA/Namibia. Zeitschrift für Kristallographie - Crystalline Materials, 189 (14) 43 doi:10.1524/zkri.1989.189.14.43 | Journal (article/letter/editorial) | | Mn3 + -bearing calderite-andradite garnets from Otjosondu, SW A/N amibia 1, Kerstin Katz-Lehnert 4 and Eduard...Abstract. Five calderite-andradite garnets from Otjosondu, Namibia, were studied chemically and by optical absorption...this work) of calderite-rich garnets from Otjosondu (SWA/Namibia) consistently yielded a sum of Al + Fe~o{...In this work the calderite-rich garnets from Otjosondu have been analyzed and investigated by optical...garnets The metamorphic manganese deposit of Otjosondu is situated about 165 km NE of Windhoek (at 21°15'S |  | Amthauer, Georg, Katz-Lehnert, Kerstin, Lattard, Dominique, Okrusch, Martin, Woermann, Eduard (1989) Crystal chemistry of natural Mn3+-bearing calderite-andradite garnets from Otjosondu, SWA/Namibia. Zeitschrift für Kristallographie - Crystalline Materials, 189 (1) 43-56 doi:10.1524/zkri.1989.189.1-2.43 | Journal (article/letter/editorial) | | Mn3 + -bearing calderite-andradite garnets from Otjosondu, SW A/N amibia 1, Kerstin Katz-Lehnert 4 and Eduard...Abstract. Five calderite-andradite garnets from Otjosondu, Namibia, were studied chemically and by optical absorption...this work) of calderite-rich garnets from Otjosondu (SWA/Namibia) consistently yielded a sum of Al + Fe~o{...In this work the calderite-rich garnets from Otjosondu have been analyzed and investigated by optical...garnets The metamorphic manganese deposit of Otjosondu is situated about 165 km NE of Windhoek (at 21°15'S |  | | Journal (article/letter/editorial) | | stability of both minerals is constrained in the region of low f CO2 . The paper reports data on the Fe–Si–O...assemblage in the Mn–Si–O system. Minerals: Pr—pyrolusite, Bx—bixbyite, Hu—haus2 mannite, Mn—manganosite...system comprises the following pure minerals: pyrolusite (Pr) MnO2, bixbyite (Bx) Mn2O3, hausmannite (Hu)...lines in the region of high oxygen fugacity corresponding to the reactions (1) 7 pyrolusite + quartz =...braunite + 2 O2 at the highest f O2 and (2) 4 pyrolusite = 2 bixbyite + O2 at lower f O2. In previous |  | | Journal (article/letter/editorial) | | depositsof Madhya Pradesh-Maharashtrabelt, India, Otjosondu, S.W. Africa and Mount Brandnuten,S. Norway are...MANGANESE FORMATION OF OTJOSONDU, S.W. AFRICA The manganese ore deposits of Otjosondu,S.W. Africa havebeenshown...SoremandCameron(50), however, described cryptomelane, pyrolusite, goethite,lithiophorite and Nsuta-MnO2from these...sediments. The manganese oxidemineralspresentare pyrolusite, cryptomelane and manganite,whichare all considered...Precambrian--Siberia, Sagan-Zaba(near Lake Baikal), Baikal region, Ukraine. Cambrian-•Qussinsk, W. Siberia,Kazakhstan(Cambrianto |  | | Journal (article/letter/editorial) | | the uppermostparts, by psilomelane,cryptomelane,pyrolusite,corohaditc, etc. (mainly Mn4+) in which psilomelaneis...carbonates(rhodochrosite), or higher oxides (pyrolusite, cryptomelane,manganite, psilomelaneetc.), the...COMPOSITION OF THE IMPORTANTMANGANESE MINERALS. PYROLUSITE -- Mn02 RAMSDELLITE -- MnO2 CRYPTOMELANE...onlymineralfromGila, Graham,GreenleeandPinal melane,pyrolusite,coronadire)are formed. When MINERALOGY OF MANGANESE...such as cryptomelane,psilomelane,coronadite,and pyrolusite. The formation of these higher oxides of manganesemay |  | | Journal (issue) | | ........................pg. 3 Actinolite from Namibia by Justin Zzyzx .................................we bring you eleven articles about locations in Namibia that do not receive much publicity. It is easy...legendary deposits such as Tsumeb, the Brandberg region and the Erongo Mountains. Alpine clefts, huge soda...Mountains, located in the southwestern part of central Namibia. The Gamsberg Mountain is the most important landmark...Fluorapatite Fluorapatite is quite rare from the region but can be found as complex, colorless crystals |  | | Journal (article/letter/editorial) | | todorokite-rich ore.Supergene alteration of manganite to pyrolusite takes placealong grainboundaries andcleavage...Mn4+oxihydroxides described byRoyet al. (1990;Fig.8), pyrolusite (Fig.5D), • I0 Microoidal kutnahorite, I94-53...hematite braunite bixbyite (lowFe) rnanganite pyrolusite • tødørøkite • birnessite cryptomelane r0manechite...limestone hostis amongthe knownNeoproterozoic deposit,Namibia(Biihnet al., 1992), fairlyuniformat -7 per mil...mil but spansa ratherlargerange suchasthe Otjosondu of -4.94 to -8.46 permilin themanganese formation (Table |  | B HN, B., OKRUSCH, M., WOERMANN, E., LEHNERT, K., HOERNES, S. (1995) Metamorphic Evolution of Neoproterozoic Manganese Formations and their Country Rocks at Otjosondu, Namibia. Journal of Petrology, 36 (2) 463-496 doi:10.1093/petrology/36.2.463 | Journal (article/letter/editorial) | | depending on their paragenesis. They indicate very Namibia were subjected to high-^T-low-P metamorphism dur-...WORD& manganiferous sediments; Damara Orogeny; Namibia; formations. They are correlated with peak pressure...Manganese Formations and their Country Rocks at Otjosondu, Namibia JOURNAL OF PETROLOGY VOLUME :t(i NUMBER...and Miller (1983a) tentatively correlated the Otjosondu ores with the Chuos Formation, which bears glaciomarine...metallogenetic model (Buhn et al., 1992, 1993*). The Otjosondu Mn ore-bearing unit consists of at least two manganese |  | | Journal (article/letter/editorial) | | the low-grade ore as braunite, psilomelane, and pyrolusite. The ore is of a sedimentary origin with supergeneenrichment...braunite, bixbyite, cryptomelane, hematite, and pyrolusite. J. E. de Villiers (1945) obtained his braunite-Il...cryptomelane (Fig. 3). J. E. de Villiers (1945)reported pyrolusite as an impurity but our X-ray photographs of his...rimmed and replaced by cryptomelane. The large black region is opal, 225X. in Table 1 and at this stagewe...reasonableto supposethat even the braunite from Otjosondu with 23.6 weight percent FezOaand the braunite |  | Arlt, T., Armbruster, T., Miletich, R., Ulmer, P., Peters, T. (1998) High pressure single-crystal synthesis, structure and compressibility of the garnet Mn 2+ 3 Mn 3+ 2 [SiO 4 ] 3. Physics and Chemistry of Minerals, 26 (2) 100-106 doi:10.1007/s002690050165 | Journal (article/letter/editorial) | | The system Mn-Si-O with excess SiO2 phases. Py, pyrolusite; Brn, braunite; Rdn, rhodonite; Pxm, pyroxmangite;...the reactions between rhodonite, braunite and pyrolusite under metamorphic conditions (Abs-Wurmbach et...Mn3+-bearing calderite-andradite garnets from Otjosondu, SWA/Namibia. Z Kristallogr 189:43±56 Angel RJ, Allan...manganese formations and their country rocks at Otjosondu, Namibia. J Petrol 36:463±496 Enraf-Nonius (1983) |  | | Report (issue) | | Geological Survey of Namibia) MINISTRY OF MINES AND ENERGY GEOLOGICAL SURVEY OF NAMIBIA Director: B.G. Ho...Ho al BULLETIN 1 Type mineralogy of Namibia by Vaughan C. Daltry Editor: Clare Kennedy Galloway Obtainable...the Geological Survey P.O. Box 2168, Windhoek, Namibia Price Local (+GST) Abroad (Post Free) R20.00 R25... ______ ........ Abstract The type mineralogy of Namibia is reviewed. One hundred and thirty-nine (139)...Twenty-three (23) unnamed phases are also listed. Namibia ranks second to Zaire as the most productive African |  | | Book | | Mountainland The Central Northern to Northwest Region including Damaraland The Central Namib Desertand...Copper Deposits The South The Pegmatitesin Central Namibia Luderitz and the Diamonds 44 49 241 254 272 275... Encyclopedia of the Mineralsof Namibia 443 Meteorites in Namibia Bibliography Index Photo credits...__ Republic of Namibia The President State House W°Ntdhoek FOREWORD Namibia is endowed with an...from near and far. Fine mineral specimen from Namibia are displayed in all the famous natural science |  | Santos, Felipe Holanda dos, Amaral, Wagner da Silva, Konhauser, Kurt, Martins, Douglas Teixeira, Castro, Marco Paulo de, Queiroga, Glaucia Nascimento, Chi Fru, Ernest, Andersen, Morten B. (2021) Unraveling sedimentary precursors and metal enrichment of high-grade metamorphosed manganese-rich rocks from the Borborema Province, northeastern Brazil. Ore Geology Reviews, 137. 104283pp. doi:10.1016/j.oregeorev.2021.104283 | Journal (article/letter/editorial) | | The oxidized manganese ore consists mainly of pyrolusite, manganese-oxyhydroxide and spessartine. The...ganese oxides cryptomelane (K[Mn4+, Mn2+]8O16) and pyrolusite (Mn4+O2) (Dasgupta, 1997; Johnson et al., 2016)...layers is recorded by massive crystallization with pyrolusite, manganite (Mn3+O[OH]), cryptomelane, and todorokite...mm- to cmthick, well-developed, grayish black, pyrolusite-graphite bands inter leaved with pale-brownish...bands (resemble a S0 relict banding). Most of the pyrolusite is in close contact with mm-sized graphite (Fig |  | Dasgupta, Somnath, Sengupta, Pulak, Bhattacharya, P. K., Mukherjee, M., Fukuoka, M., Banerjee, H., Roy, Supriya (1989) Mineral reactions in manganese oxide rocks; P-T-X phase relations. Economic Geology, 84 (2) 434-443 doi:10.2113/gsecongeo.84.2.434 | Journal (article/letter/editorial) | | braunitc,hausmannite, jacobsite,bixbyite,hematite,pyrolusite,quartz, andrhodochrosite in the systemMn-Fe-Si-C-Oandthe...zone,660øC,6 kbars + Hs + Qz Urandi, Brazil Otjosondu, (iv) Br01q-Py q-Qz Chloritezone (v) Br0y q-Jbq-Hm...de Villiers (1983) Bhattacharyaet al. (1988) Namibia India California, (ix) Br + Rdh q-Hs ___ Qz ...individually includedin the grid. They are representedby pyrolusite. Dependingon the presenceor absenceof quartzand...phismof Mn carbonatesediments. With the exceptionof pyrolusite,which is stable estimatedphysicalconditionsof |  | | Journal (article/letter/editorial) | | Manganese minerals are present as coarse-grained pyrolusite and fine-grained aggregates of greyish minerals...indicate that they do not replace silicate minerals. Pyrolusite generally postdates cryptomelane. The compositions...minerals Cryptomelane Pyrolusite Roman6chite Goethite Lepidocrocite Cryptomelane Pyrolusite Goethite General...categories of feldspars from the Otjosondu manganese deposit, Namibia (Viswanathan and Kielhorn, 1983)...hydroxides. Tetravalent manganese oxides include pyrolusite (13-MnO2) and m i n e r a l s of the m a n g |  | | Journal (article/letter/editorial) | | produced by conversion of todorokite-birnessite. Pyrolusite and cryptomelane, conventionallyconsidered as...deposited in deep water at a continental margin in a region of oceanic upwelling. Hein and Koski (1987) stressed...and Stribrny, 1986) and the Damara Supergroup, Namibia (Roper, 1956), interstratified Mn-oxide-chert occurrences...association with Mn4+-bearing oxides such as pyrolusite and/or cryptomelane stabilized by late diagenesis...of these primary oxides but are dominated by pyrolusite, cryptomelane and/ or psilomelane (roman~chite) |  | | Book (edition) | | orangebrown distinctive brown to blue grey Mineral Pyrolusite Rasvumite Rickardite light yellow, brown, brilliant...Madenköy Mine, Çayeli, Rize Province, Black Sea Region, Turkey (sample: Halbach); XPL If marked in description... Taymyrskiy Autonomous Okrug, Eastern-Siberian Region, Russia (sample: Melcher/Oberthür); PPL D Fine-grained... Karabash, Chelyabinsk Oblast’, Southern Urals Region, Russia Au-Cu alloys, native Copper, native Gold...Potaro River, Kangaruma District, Potaro-Siparuni Region, Guyana Chalcopyrite, native Gold, Hematite, Millerite |  | Armbruster, Thomas, Kohler, Thomas, Libowitzky, Eugen, Friedrich, Alexandra, Miletich, Ronald, Kunz, Martin, Medenbach, Olaf, Gutzmer, Jens (2001) Structure, compressibility, hydrogen bonding, and dehydration of the tetragonal Mn3+hydrogarnet, henritermierite. American Mineralogist, 86 (1) 147-158 doi:10.2138/am-2001-0116 | Journal (article/letter/editorial) | | hydrogen do not show any absorption bands in this region, even in much thicker slabs (e.g., Bell and Rossman...above 600 K a topotactic transformation to MnO2, pyrolusite. Recently Li et al. (1998) reported dehydration...Mn3+-bearing calderite-andradite garnets from Otjosondu, SWA/Namibia. Zeitschrift für Kristallographie, 189...manganese formations and their country rocks at Otjosondu, Namibia. Journal of Petrology, 36, 463–496. Burnham...relation to the manganese dioxides ramsdellite and pyrolusite. Journal of Solid State Chemistry, 133, 486–500 |  | | Journal (article/letter/editorial) | | relativelyshallow)shows that the manganese peroxideminerals(pyrolusite, cryptomelane,etc.) are found only to a depth...the Postdepositedby hypogenesolutions. masburg region and is a major constituentof the Kalahari ores...present Namibia (25.59%Fe•Os) found that at 100øC manganiteand cryptomelane in braunitefrom Otjosondu, form...the Postmasburg area and not from the Ka- be pyrolusite,cryptomelane,psilomelane, hollandite, todorokite...indicated,and this suchlocalities asOtjosondu, Namibia(J.E. de Villiers, zoningwould be superimposed on |  | | Report (chapter) | | et al. 1989) Spain (Milland & Velilla 1994) Namibia (Bfihn et al. 1995) Sierra Nevada, California...and IIA manganese silicate rocks from India and Namibia respectively. These authors have not attempted...clinopyroxenes from types IIIA and IIA rocks from India and Namibia respectively. Compositionally these are manganoan...parts of the system Mn-Fe-Si-O at 1 kbar. Py, pyrolusite; others as in Figs 1 and 2. will not form. Although...parameters are available for bixbyite, hausmannite, pyrolusite, Downloaded from http://sp.lyellcollection |  | | Journal (article/letter/editorial) | | jacobsite,hausmannite,vredenburgitc, manganite, pyrolusite, cryptomelene, coronadite, hematite and goethite...the colloidallow-temperatureores, manganite, pyrolusite,cryptomelane,coronaditeand goethitewere identified;...metamorphic derivationjacobsite,hollandite, manganite, pyrolusite andcryptomelane werefound. IndividualX-ray data...cleavageplanes (Fig. 9). The alterationof hollanditeto pyrolusite,cryptomelane andpossibly psilomelane(thoughundetected...irregularveins)of pyrolusite andcryptomelane in brauniteandjacobsite, was marked. Pyrolusite formsoccasionally |  | | Report (chapter) | | associated with metamorphosed Damara Sequence of Namibia based mainly on lithofacies and tectonic setting...of manganite, braunite, bixbyite, Psilomelane, pyrolusite and cryptomelane (see Roy et al. 1990 for details)...deposits in the Neoproterozoic Damara Sequence of Namibia formed under pelagic conditions in the outer shelf...outer shelf manganese and iron deposits at Otjosondu (Namibia) related to the Damara Oceanic opening. Economic...Late Proterozoic manganese and ironformations (Namibia) through upper amphibolite facies metamorphism: |  | | Journal (article/letter/editorial) | | deoxidation of pyrolusite in presence of quartz. Bixbyite could appear later from the reacting pyrolusite-braunite-quartz...in jacobsite. Initially braunit%~ along with pyrolusite or hollandite were formed from appropriate precursors...the following assemblages: (IV) braunit%) + pyrolusite (chlorite grade) (V) braunite(i ) + bixbyite...chlorite grade condition through deoxidation of pyrolusite in the presence of quartz. Bixbyite appeared...assemblages at the complete disappearance of pyrolusite. Further, braunite once stabilized never oxidized |
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