Groote Eylandt manganese norm: A new application of mineral normalization techniques on supergene alteration products

The method described assists in the quantification of oxidic manganese minerals and associated materials from the Groote Eylandt manganese deposits (Northern Territory, Australia) which have been influenced by supergene processes. These ores are commonly composed of very fine grained minerals, intergrown with lateritie components like kaolinitic clays and iron oxyhydroxides. Additionally, many manganese phases are poorly-ordered structures which are difficult to identify. Although Fourier transform infrared (FTIR) spectroscopy has produced dependable data for a limited range of processed ores, it failed with rocks that contained a mixture of ore minerals and various gangue phases, as was the case with other analytical techniques (microscopic studies, XRD, IR, etc.). The normalization is based on the same principles as other mineral norms (e.g. CIPW-Norm) and the norm minerals themselves were developed according to the mineralogical conditions in the supergene manganese deposits of Groote Eylandt in the Northern Territory of Australia. Nevertheless, the list of minerals can easily be extended and adjusted to slightly different environments (e.g. bauxites). The following minerals can be obtained from this normalization technique: romanechite, todorokite, cryptomelane, pyrolusite, anatase, quartz, kaolinite, gibbsite, goethite for hematite-free and hematite-containing samples, hematite, and excess water.