Exploration status for oxide and sulphide zinc ores at Skorpion Zinc Mine, Namibia
- Authors: Sitoka, Stefanus
- Date: 2015
- Subjects: Scorpion Zinc Mine (Namibia) , Zinc ores , Oxide minerals , Sulfide minerals , Zinc mines and mining -- Namibia , Prospecting -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5087 , http://hdl.handle.net/10962/d1018204
- Description: The thesis is inspired by recent interests in oxide zinc ores caused by new developments in the technology of hydrometallurgy. The improved techniques turned the non-sulphide zinc ores in to attractive exploration targets due to a number of advantages such as low metal recovery costs and favorable environmental aspects such as the obvious absence of sulfur (Large, 2001). Historically extraction of zinc metal from oxide ores was not possible until recently. The metallurgical complexity resulted in a lack of interest and hence some economic oxide zinc ores might have been missed by conventional exploration techniques. The study presents a review of exploration status at Skorpion mine based on different exploration techniques and their application to sulphide and oxide zinc ore exploration. The challenge facing the mineral exploration industry today is the inability to detect mineral deposits under cover. Therefore a key to successful exploration program lies in the selection of the right exploration technique. Important parameters that should be highlighted in the exploration methodology are the geological situation of an area, equipment applicability and effectiveness, survey limitation, equipment mobilization and the safety aspects involved. The aim of this thesis is to provide a general guideline for sulphide and non-sulphide zinc ore exploration on the Skorpion area and other similar geological environments. Geochemical surveys appears to be more complimentary in exploration of non-sulphide zinc exploration. Although geochemical techniques are preferred, it is equally important to choose the right soil horizon. Furthermore, sample media may mean the difference between success and failure in geochemical exploration of non-sulphide zinc mineralization, due to high mobility of zinc in the surficial environment. On cost comparison, surface geochemical surveys programs are more cost effective except for litho-geochemical sampling which are commonly carried out through subsurface drilling. Geophysical techniques have limited application in exploration of non-sulphide zinc mineralization due to a lack of major physical properties (e.g., magnetic and electrical properties) in non-sulphides unlike their sulphide counterparts. However geophysical methods are commendable in delineating massive and disseminated sulphides mainly if they are associated with major Fe minerals (pyrrhotite or magnetite). In addition, geophysical techniques may be effective in mapping of subsurface primary and secondary structures such as basin faults which might have acted as pathways for metal-rich fluids. Terms non-sulphide and oxide zinc mineralization are used interchangeably throughout the thesis. Recommendations on regional and local target generation are presented in the thesis to give some basic guide lines on target generation strategies. The most important conclusion reached in this study is that, success in exploration for non-sulphide or sulphide zinc mineralization might be enhanced through the integrated exploration methodology.
- Full Text:
- Date Issued: 2015
The cryopreservation potential and ultrastructure of Agulhas sole Austroglossus pectoralis spermatozoa
- Authors: Markovina, Michael Zeljan
- Date: 2008
- Subjects: Spermatozoa , Spermatozoa -- Cryopreservation , Aquaculture , Fishes -- Breeding , Soleidae , Flatfishes , Agulhas Current (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5251 , http://hdl.handle.net/10962/d1005094 , Spermatozoa , Spermatozoa -- Cryopreservation , Aquaculture , Fishes -- Breeding , Soleidae , Flatfishes , Agulhas Current (South Africa)
- Description: As the estimated market demand for the Agulhas sole Austroglossus pectoralis exceeds the annual catch from trawlers, this species is a potential aquaculture candidate. Broodstock conditioning and gamete preservation is part of research and development aiming at establishing a breeding protocol for a new aquaculture species. Based on a literature review of the morphology of pleuronectiform spermatozoa, this study was designed firstly, to contribute to the field of spermatozoan morphology by describing the ultrastructure of A. pectoralis spermatozoa. This was followed by an experiment to cryopreserve mature spermatozoa to provide baseline data for future studies on this and related species. The testis of A. pectoralis was a paired structure encased in a membrane, the tunica albuginea. The primary testis was located on the dorsal surface of the rib cage and the secondary testis on the ventral side. The testis was of an unrestricted spermatogonial type, based upon observations of spermatogonia along the entire length of the lobule. Mature spermatozoa of A. pectoralis had an acrosome-free ovoid head 1.68 ± 1.6μm in length and 1.7 ± 1.6μm in diameter, a short mid-piece of 0.5 ± 0.1μm in length, containing 7 irregularly shaped mitochondria forming a ring-like structure at the base of the nucleus. The flagellae were 47.4 ± 4.8μm in length, most with two plasma membrane lateral fin-like projections. However, some flagellae had either zero or three lateral fin projections. Cross-sections of the flagellae showed an axenome with a 9+2 microtubule configuration. The proximal and distal centriols were coaxal, situated deep within the nuclear fossa. The structure of A. pectoralis spermatozoa conformed to the type 1 ect-aquasperm, also found in externally fertilizing species. This type has been suggested to be the plesiomorphic form in Neopterigians. Finally, this study contributed to a cryopreservation protocol for A. pectoralis spermatozoa by testing the two cryoprotectants dimethyl sulphoxide (DMSO) and glycerol. Glycerol, at a concentration of 10%, offered better cryoprotection than DMSO. This was established using flow cytometry analysis of post-thaw nuclear membrane integrity after 64 days of storage in liquid nitrogen. The toxicity of DMSO to isolated cellular proteins may have resulted in DMSO-treated sperm having the highest percent (35.2% ± 3.2%) of non-viable cells compared with 23.0% ± 2.5% and 27.8% ± 3.4% for glycerol and the control, respectively. The presence of sucrose in the Modified Mounib Medium extender solution may explain why 45.5% ± 5% of the sperm cells were potentially viable in the control treatment. Initially, the white margined sole Dagatichthys marginatus (Soleidae) was selected as the most suitable candidate for flatfish aquaculture in South Africa. Thus, the aim of this study was to investigate the cryogenic potential and ultrastructure of D. marginatus spermatozoa. However, due to a skewed sex ratio, there were not enough males available to study this species. A skewed sex ratio is common amongst soleids, thus, the need to develop effective cryopreservation methods and to develop an understanding of sperm morphology so that the best time for cryopreservation can be chosen. In conclusion, this first description of spermatozan morphology of A. pectoralis contributed to our understanding of soleid sperm ultrastructure. In addition, a comparison of testis appearance between fish sampled just prior to spawning season and fish with mature sperm provided information on the spawning season of this species. The findings from the cryopreservation experiment suggested that glycerol was a feasible cryoprotectant for this species when sperm was prepared under field conditions.
- Full Text:
- Date Issued: 2008
The motivating force of moral beliefs
- Authors: Vos, James Antony
- Date: 2005 , 2013-06-14
- Subjects: Hume, David, 1711-1776 -- Ethics , Ethics , Motivation , Practical reason , Rationalism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2729 , http://hdl.handle.net/10962/d1003804 , Hume, David, 1711-1776 -- Ethics , Ethics , Motivation , Practical reason , Rationalism
- Description: I investigate the issue of whether or not one's holding a moral belief is sufficient to motivate one to act as that belief prescribes. I argue that rational persons who hold a moral belief that is also a 'self-referential belief' will form a desire to act as that belief prescribes and thereby be motivated to act on the moral belief. I argue for this claim by, firstly, showing that the demand that moral judgements must be intrinsically motivating, Internalism, should only apply to rational persons, that is, the link between moral judgement and motivation can be broken in cases of irrationality. Secondly, I argue against the Humean claim that one cannot rationally form a desire simply because one believes that one ought to have that desire. This claim requires an investigation into a variety of views of Practical Reason and an argument concluding that Practical Reason is broader in scope than the Instrumentalist or Humean allows. I undertake this task in chapter 2. Thirdly, I argue that believing that I ought to perform a certain action will give me an internal commitment to perform that action, insofar as I am rational. I argue that an internal commitment is a form of desire. Once I recognise that I have a moral belief and an internal commitment, I will be motivated to act as that belief and commitment prescribe. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2005