Characterization of quartz in some potential high purity quartz deposits in the Damara orogenic belt
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Date
2016
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Publisher
University of Namibia
Abstract
This research project was aimed at characterizing quartz from selected potential High Purity Quartz (HPQ) deposits in terms of trace element associations, associated trace element concentrations, and growth zones. Six quartz rock samples were collected from three different localities, with two samples collected from each locality. Concentrations of Na, K, Li, Al, Ca, Fe, Ti, B and P were analysed in situ by LA-ICP-MS. This analysis was aimed at finding out whether the total concentrations of these trace elements do not exceed 50 μg g-1 as required by the HPQ definition. The Lowest total concentrations obtained from analysed samples were found to be much higher than the required minimum of less than 50 μg g-1and are given as follows: sample DB2 from the farm Doornboom 316 yielded 2,144.6 μg g-1, sample ALT2 from the farm Alt-Seeis 133 yielded 726.3 μg g-1 and sample MA1 from SP14 pegmatite intrusion in the Cape cross – Uis Pegmatite belt yielded 1,753.5 μg g-1. Analytical results obtained from LA-ICP-MS showed very low Fe concentrations in all three deposits with all samples giving an average of <2μg g-1 and is the only trace element that met HPQ definition requirement of <3 μg g-1 Fe content. All three deposits showed very high average calcium concentration values varying between 450 and 750 μg g-1 and these high concentrations are likely to be associated with the chemistry of the fluids from which the hydrothermal quartz crystallized. Aluminium and alkali metals (Li, Na and K) concentrations were relatively high in all the deposits with fewer exceptions. Average values of lithium were noted as being between 170 and 230 μg g-1, those of sodium as being between 70 and 1600 μg g-1, and those of potassium as being between 65 and 120 μg g-1, while aluminium average values were found to be between 150 and 660 μg g-1. Exceptions were exhibited by sample ALT 2 from the hydrothermal vein deposit at the farm Alt Seeis 133, in which all the alkali metals and aluminium average values were found to be less than 63 μg g-1. Titanium content in all samples was found to be relatively low (averaging between 20 and 31 μg g-1). All the samples from deposits under this study do not meet the requirements of the HPQ definition and are thus not HPQ deposits. However a beneficiation study on these deposits is recommended to establish possible industrial applications that may be feasible. Scanning Electron Microscopy - Cathodoluminescence (SEM-CL) images of quartz grains were obtained from polished carbon coated samples. SEM-CL imaging was aimed at revealing replacements, fluid driven overprints and different quartz generations. The transformation of primary to secondary quartz through replacement was very limited in some samples and absent in others. This implies that metamorphic conditions did not have a major impact if any at all on the chemistry of trace elements in quartz. Statistical interpretation of analytical results from SP14 pegmatite intrusions and those from Doornboom indicate significant compositional similarities.
Description
A mini thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science (Applied Geology)
Keywords
Quartz, Damara orogenic belt