Mineralogical and thermal characteristics of low-grade Jinlong bauxite sourced from Guangxi Province, China

Abstract

Characteristic samples from the No. 1 ore body of the Jinlong bauxite deposit in Guangxi Province, China, were assessed to determine their chemical composition using whole-rock geochemical analysis, their mineral components using X-ray diffraction, their thermal characteristics via differential thermal analysis, thermogravimetry and differential thermogravimetry, and their dissemination characteristics by scanning electron microscopy/energydispersive spectrometry. The results show that the average Al 2 O 3 content in the Jinlong bauxite deposit is 41 % and that the Al 2 O 3 /SiO 2 ratio is approximately 2.17, and thus, the ore may be defined as low-grade bauxite. The main minerals found in the ore were diaspore (20.3-43 %), gibbsite, clays and hematite. In differential thermal analysis results, the bauxite samples exhibit two distinct endothermic peaks, with the dehydration of gibbsite occurring in the 200-260°C range and the dehydration of diaspore occurring in the 524-550°C range. Thermogravimetry and differential thermogravimetry indicate four decomposition stages: evaporation of adsorbed water (50-160°C), gibbsite decomposition (190-280°C), goethite decomposition (190-280°C) and diaspore dehydroxylation (460-580°C). The diaspore belongs to the orthorhombic dipyramidal class and exists primarily in three dissemination forms-euhedral and subhedral grain, bean and oolitic shaped, and aphanitic and microcrystalline aggregates, and is always accompanied by kaolinite and pyrophyllite.

Co–Mn Mineralisations in the Ni Laterite Deposits of Loma Caribe (Dominican Republic) and Loma de Hierro (Venezuela)

“…This reaction (i.e., 2FeOOH → Fe 2 O 3 + H 2 O) occurs at temperatures between 300 and 344 • C [35] or 270 and 330 • C [36], and it is commonly associated with a mass loss of 10% or less if there are secondary phases. This mass loss coincides with an endothermic peak around 325 • C in the DTA curve (Figure 5b) that is considered as the result of the breakdown of goethite [34][35][36].…”

“…In Loma Caribe deposits, and according to XRPD (samples LC-6, LC-7 and LC-7_black), lithiophorite is ubiquitous with clear peaks at 9. Thermogravimetry showed that samples from Loma Caribe experience a mass loss of about 4% before 260-280 °C, probably due to the loss of adsorbed water for temperatures below 110-160 °C [33,34] and to the transformation of gibbsite to boehmite, which is reported to occur at temperatures between 150 and 260 °C [34] (Figure 5a). Between 260 and 320 °C, the mass loss is between 5 and 8%.…”

Mineral transformations and textural evolution during roasting of bog iron ores

“…Although the overall course of the processes is widely known, the effects of various crystal-chemical and chemical factors on the transformation mechanisms and properties of the products are still under vigorous debate [1,3]. This type of research focuses usually on monomineral synthetic samples [e.g., [4][5][6][7][8][9][10] and does not fully reflect the complexity of the processes during thermal transformations of natural Fe-oxide-rich materials [e.g., [10][11][12][13][14][15][16][17], archeological findings [18,19] and composite industrial products or wastes [20][21][22]. A good example of such a complex system are bog iron ores.…”

On long-baseline relative positioning with BDS-2/BDS-3/GPS data

“…Since the BDS was put into use, many scholars in China and abroad have done plenty of researches on its performance of BDS alone, or GPS + BDS combined [5][6][7][8]. Zhang et al [9] show that the accuracy of a static baseline (medium baseline, <100km) using the four-hour long BDS measurement data based on the broadcast ephemeris reached 4cm. Pu et al and Wu et al [10,11] analyzed the relative positioning performance using the combination of the GPS, BDS and Galileo systems with the short baseline hybrid double-difference and short baseline single epoch tight combination.…”