Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 19 (1958) no. 4, p. 774. "U. S. Geological Survey [preliminary] Open File Report." Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 132-134).

No description available.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1910. / The entire thesis text is included in file. Typescript. Illustrated by authors. Title from title screen of thesis/dissertation PDF file (viewed February 12, 2009)

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [73]-74).

No description available.

Ph.D. / The economically important sedimentary manganese deposits of the Paleoproterozoic Kalahari and Postmasburg manganese fields, are situated in close geographic vicinity to each other in the Griqualand West region of the Northern Cape Province, South Africa. This thesis describes aspects of mineralogy, petrography and geochemistry of the manganese ores with the purpose to establish genetic models for genesis and alteration of manganese ores of both manganese fields. The Kalahari manganese field, situated some 60 km northwest of Kuruman, is the largest known land-based manganese deposit. Manganese ores occur interbedded with iron-formations of the Hotazel Formation of the Voelwater Subgroup of the Late Archean-Paleoproterozoic Transvaal Supergroup. The sediments of the Voelwater Subgroup are preserved in five erosional relics, of which the Kalahari manganese deposit is by far the largest and the only one of economic importance. Two types of ore are mined, low-grade sedimentary Mamatwan-type ore and high-grade Wesselstype ore. Mamatwan-type ore is represented by microcrystalline laminated braunite-lutite composed of kutnahorite, Mn-calcite, braunite and hematite, modified by the occurrence of late diagenetic or metamorphic hausmannite, partridgeite, manganite and calcite. Mamatwan-type ore contains up to 38 mass % Mn and constitutes about 97 % of the ore reserves in the Kalahari manganese deposit. High-grade Wessels-type ore, with a manganese content of between 42 to 48 mass % Mn (on average), constitutes about 3 % of the ore reserves. It occurs only in the northwestern part of the main Kalahari deposit, and in small deposits at Hotazel and Langdon, in association with a system of north-south striking normal faults. The Wessels alteration event is thought to be related to the Kibaran orogenetic event (about 1.1 Ga). Fault zones are ferruginized and alongside faults sedimentary Mamatwan-type ore has been hydrothermally upgraded to Wessels-type ore. Metasomatic fronts are defined by changing mineral associations. These associations clearly illustrate that decreasing degrees of alteration relate to increasing distance from the fluid feeders. Areas of unaltered Mamatwan-type ore are preserved in the core of fault blocks. Wessels-type ore consists mostly of hausmannite, bixbyite, braunite II and manganite and subordinate gangue minerals such as clinochlore and andradite but the mineral assemblage associated with the Wessels alteration event is unusually diverse. More than 100 minerals have been identified, amongst them 8 new mineral species and an unusual, ferrimagnetic, Fe-rich variety of hausmannite. Mass balance calculations illustrate that the upgrading of the Wessels-type manganese ore is a consequence of leaching of CaO, MgO, CO 2, and Si02 from a low-grade Mamatwan-type precursor. This metasomatic process results in increasing secondary porosities, compaction of the orebody to two thirds of its original thickness and consequently residual enrichment of manganese in the ores. Three younger alteration events are observed in the Kalahari manganese deposit. These are only of minor economic importance. Wallrock alteration associated with the Mamatwan alteration event is characterized by reductive leaching of Fe and Mn around syntectonic veins and joints with pyritechalcopyrite- carbonate mineralization. The alteration is explained by infiltration of epithermal solutions that were introduced along veins or joints. The timing of the alteration event has tentatively been placed into the Pre-Karoo era. The Smartt alteration event is associated with intensive faulthosted brecciation and replacement of braunite and carbonates of the Mamatwan-type ore by todorokite and manganomelane, a process that causes considerable upgrading of the manganese ore next to a fault breccia at Mamatwan mine, and the formation of stratiform cross-fibre todorokite veins at Smartt mine. The Smartt alteration event postdates the Mamatwan alteration event and has tentatively been correlated with Pre-Kalahari groundwater circulation. Supergene alteration of the ores took place in Kalahari and Post-Kalahari times. It is characterized by the occurrence of cryptomelane, pyrolusite and other typically supergene manganese oxides along the suboutcrop of the Hotazel Formation beneath the Cenozoic Kalahari Formation. The Postmasburg manganese field is situated about 120 km to the south of the Kalahari manganese field on the Maremane dome. Two arcuate belts of deposits extend from Postmasburg in the south to Sishen in the north. Two major ore types are present. The ferruginous type of ore is composed mainly of braunite, partridgeite and bixbyite and occurs along the centre of the Gamagara Ridge, or Western belt. The siliceous type of ore consists of braunite, quartz and minor partridgeite and occurs in small deposits along the Klipfontein Hills (or Eastern belt) and the northern and southern extremities of the Gamagara Ridge. Geological and geochemical evidence suggest that the manganese ores represent weakly metamorphosed wad deposits that accumulated in karst depressions during a period of lateritic weathering and karstification in a supergene, terrestrial environment during the Late Paleoproterozoic. The dolomites of the Campbellrand Group of the Transvaal Supergroup are host and source for the wad accumulations. Contrasting geological settings are suggested for the accumulation of the siliceous and the ferruginous types of ore respectively. The former originated as small pods and lenses of wad in chert breccia that accumulated in a karst cave system capped by the hematitized Manganore iron-formation of the Transvaal Supergroup. The cave system finally collapsed and the hematitized iron-formation slumped into the sinkhole structures. The ferruginous type of ore accumulated as mixed wad-clay sediment trapped in surficial sinkhole depressions in the paleokarst surface. The orebodies are conformably overlain by the Doornfontein hematite pebble conglomerate or aluminous shales belonging to the Gamagara Formation of the Late Paleoproterozoic Olifantshoek Group. Well preserved karst laterite paleosol profiles, described from the basal section of the Gamagara Formation, provide a strong argument for the terrestrial, supergene origin of the manganese ores. The manganese ores in the Postmasburg manganese field were affected by diagenesis and lower greenschist facies metamorphism. Metamorphism resulted in recrystallization to braunite in the siliceous ores of the Eastern belt, and to massive or mosaic textured braunite and idioblastic partridgeite in the ferruginous environment of the Western belt. Secondary karstification and supergene weathering are evidence for renewed subaerial exposure of the manganese ore and their host rocks. The metamorphic mineral assemblage is replaced by abundant romanechite, lithiophorite and other supergene manganese oxides. Comparison between the Kalahari- and the Postmasburg manganese field shows that sedimentary manganese accumulation took place in entirely different depositional environments and owing to different mechanisms. Their close geographic relationship appears to be coincidental. Apparent similarities arise as a consequence of regional geological events that postdate the deposition of the manganese ores. These similarities include the lower greenschist facies metamorphic overprint, an event tentatively related to thrusting and crustal thickening during the Kheis orogenetic event, and syn- to Post-Kalahari supergene alteration. The correlation of structurally controlled hydrothermal alteration events in the Kalahari manganese field and the Postmasburg manganese field remains difficult due to the absence of the necessary geochronological constraints.

M.Sc. / This investigation is a mineralogical study of the reduction products formed during the reduction of Mamatwan manganese ore, as well as presentation of a possible reduction mechanism for this ore type. Cubes, 20 millimeter in dimensions, of Mamatwan manganese ore were reduced in a vertical tube resistance furnace at temperatures varying from 1200 to 1500°C with various reductants and retention times...

Thesis (Ph.D.) - University of Queensland, 2005. / Title reads superscript Ar/superscript Ar. Includes bibliography.

D. Phil. / The Kalahari Manganese Deposit (KMD) is the largest of five erosional relics of the Hotazel Formation that are located near Kuruman in the Northern Cape Province of South Africa. Manganese ores are exploited from the lowermost of three manganiferous beds that are interbedded with banded iron-formation (BIF) and hematite lutite, that together constitute the Hotazel Formation. Two major ore types have been delineated previously, viz. low grade braunite lutite of the Mamatwan-type, and high grade oxidic ores of the Wessels-type, with the latter spatially restricted to the northern KMD. Genesis of the ores was temporally distinct, with the Mamatwan-type ore considered as a sedimentary-diagenetic precursor to the hydrothermally altered Wessels-type ore. Drill core samples from the Nchwaning-Gloria area of the northern KMD were analysed, with the aim to better characterise ore genesis, with emphasis on ore alteration. A second part of the study aimed at the application of mineralogical and geochemical information to aspects of ore smelting for the production of Mn alloy for use in the steel industry. Methods employed were drill core logging, X-ray diffraction (XRD), petrography, electron probe microanalysis (EPMA), major and trace element (including REE) analysis (employing artificial neural networks for evaluation of elemental trends), and stable isotope (C and O) analysis. Significant effort was invested in method development for quantitative mineralogical modal analysis using Rietveld refinement of XRD data. The study shows that a number of ore types can be differentiated in the northern KMD on the basis of mineral assemblage, grade, texture and geochemical characteristics. The ores are broadly classified into least altered (LA), partially altered (PA) and advanced altered (AA) types. The LA ores are low grade (<40 wt%Mn) Mn lutites, with dolomite-group carbonate a significant component in addition to braunite. Serpentine is a ubiquitous trace mineral, and boron is a characteristic trace element hosted predominantly by braunite in these ores. Ores of the PA type comprise either braunite-hausmannite-calcite or hausmannite-calcite assemblages, are fine to coarse grained, and display intermediate Mn grades (40-45 wt%Mn). They exhibit a transitional trace element signature. Advanced altered ores may be classified into five different types, based on mineral assemblages that contain hausmannite and/or braunite as significant minerals. Carbonates occur predominantly in the form of calcite, present in minor to trace proportions. Textures vary from fine to very coarse grained, and high Mn grades (typically >45 wt%Mn), are recorded. Trace elements of significance include Zn, associated with hausmannite, B, associated with massive braunite and a number of trace minerals, and P, typically present in trace quantities of apatite. In terms of ore genesis, mineralogical, geochemical and geological considerations suggest that Mn (and Fe) originated from submarine hydrothermal vents, from which it travelled in hydrothermal plumes, prior to rapid deposition ~2.2 Ga ago. Diagenesis followed soon after deposition, through redox reactions involving organic matter and higher oxides of Mn to produce the braunite-carbonate assemblage primarily observed in LA ores. The carbonate:oxide ratio and nature of the carbonates varied slightly depending on fluctuations in organic matter flux to the sediment, as well as marine bicarbonate concentrations. Metamorphism, in relation to diagenesis and metasomatism, is poorly understood, but is perceived to have resulted in serpentine formation, as observed in LA and PA ores.

No description available.