Monazite Recovery by Magnetic and Gravity Separation of Medium Grade Zircon Concentrate from Senegalese Heavy Mineral Sands Deposit

Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zircon, medium grade zircon standard) from Senegal’s heavy mineral sands. During mining separation, monazite, which is a paramagnetic mineral, was found in a non-negligible concentration of 0.57 wt% on average in the medium grade zircon standard which also contains 37.96 wt% zircon and 44.46 wt% titanium oxides. Magnetic and gravity separation tests were carried out on the Medium grade zircon standard (MGZS) to produce a monazite concentrate at Eramet Ideas laboratory. Magnetic separation at 1.5 teslas intensity resulted in the recovery of 94.8% of the monazite from the MGZS. Gravity separation also recovered 76.6% of the monazite from the MGZS. The combination of these two treatment methods can thus produce three concentrates from MGZS (a monazite concentrate, a zircon concentrate, and a titanium oxide concentrate).

Mineralogical Characterization of Heavy Mineral Concentrates from Senegalese Great Cost by Using Qemscan and SEM

The heavy mineral sands of Senegal are exploited to extract titanium oxides and zircon. Mining is carried out first by means of a floating dredge and concentration plant which produces a heavy mineral concentrate (HMC) containing on average 78% titanium oxides, 11% zircon and a set of silicate and alumino-silicate minerals. This heavy mineral concentrate is then treated by gravity, magnetic and electrostatic separation to produce titanium oxide concentrates (ilmenite, leucoxene, rutile) and three varieties of zircon concentrates (Premium zircon, standard zircon and medium grade zircon standard). In this study, we describe the various mineral concentrates in terms of mineralogical assemblages, and textural variability within grains, using Qemscan and Scanning Electron Microscopy. The titanium oxide concentrates are differentiated by their TiO2 content and vary from ilmenite to rutile. The zircon concentrates are characterized by the presence of impurities in the zircons, which consist in numerous inclusions of titanium oxides and silicate minerals. The mineralogical characteristics determined by scanning electron microscopy and by Qemscan showed great variability within the grains themselves. Heavy minerals contain many mineral inclusions and show strong chemical zoning.

Availability of Residual and/or Applied Inorganic Phosphorus for Sugarcane Uptake and Growth in a Post-Mined Reconstituted Soil

Mineral sands mining is worldwide an environmental issue and also at the Hillendale mine in KwaZulu-Natal, South Africa. The post-mined soil is to be rehabilitated to sugarcane cropping. One of the concerns with the post-mined soil which is reconstituted with a 70:30 mixture of sand: slimes (silt-plus-clay fraction), is its low phosphorus (P) status, which could be limiting for optimum sugarcane production. A field experiment was conducted on a reconstituted soil at Hillendale to establish the availability of either residual or applied inorganic P to the plant and first ratoon sugarcane crop. Four treatments were evaluated including those where P fertilizer was omitted, applied at half the recommended rate or introduced equal to the recommended rate according to chemical analysis of the soil. In the fourth treatment, no fertilizer was applied at all, whereas nitrogen (N) and potassium (K) were added at recommended rates in the first three treatments. Phosphorus application had a significant effect on sugarcane fractional light interception and aboveground biomass yield of the plant and first ratoon crops, and stalk length and diameter of the first ratoon crop. Pol, brix, purity and fibre content and tiller number were not affected by P application. The application of P increased the foliar N, P, K, calcium (Ca), magnesium (Mg) and sulphur (S) contents of both crops. However, foliar N, P and K were deficient in the first ratoon crop even in the case where fertilizer was applied at the recommended rates, which could have been because of waterlogging. The possible effect of waterlogging on P uptake needs to be addressed in future studies in this reconstituted soil.

One size does not fit all: Refining zircon provenance interpretations via integrated grain shape, geochronology, and Hf isotope analysis

Sediment provenance studies commonly utilize isotopic signatures to resolve detrital mineral sources and routing.However,non-unique ages and geochemical characteristics across geographically distinct crystalline source regions can lead to significant ambiguities in mineral provenance interpretations.Such ambiguity is apparent in southern Australia’s Cenozoic Eucla Basin,which hosts world-class heavy mineral sand resources.Here,new Hf isotope data are provided from four heavy mineral prospects(N=8,n=844[N=samples,n=grains]).Zircon grain shape data are also presented for a suite of detrital Eucla Basin samples(N=22,n=35,604)and the basin’s underlying basement,the Coompana Province(N=13,n=824).The data are integrated with published detrital and non-detrital primary zircon data to investigate the efficacy of grain shape analysis to better resolve the basin’s mineral provenance.Zircon Hf isotope compositions indicate a primary Mesoproterozoic juvenile source for zircon melts(~1250-1000 Ma,-2.5<εHf>~+5)with additional contributions from a range of juvenile to evolved late Archean to Phanerozoic-aged zircon bearing magmas(-28.0<εHf>+11).U-Pb geochronology and Hf isotopes are incapable of differentiating Mesoproterozoic-aged source rocks bounding the region for the majority of heavy mineral deposits analyzed as potential sources express overlapping crystallization ages and similarities in Hf-isotope characteristics.However,distinct zircon grain shapes(i.e.,perimeter,major axis and circularity)facilitate improved differentiation across these Mesoproterozoic sources.Filtering of U-Pb age,Hf isotope and shape data implicate the underlying Madura and Coompana provinces as dominant sediment sources for Eucla Basin detritus aged~1400-1000 Ma.The lack of direct sediment pathways between the underlying basement provinces and placer sediments analyzed demonstrates the significance of zircon reworking from intermediate sedimentary basins in the formation of the economically significant Eucla Basin beach placers.Zircon grain shape represents a cheaply acquired and readily incorporated grain characteristic that can enhance provenance investigations.

Structural development of vegetation on rehabilitated North Stradbroke Island:Above/belowground feedback may facilitate alternative ecological outcomes

Introduction:This study depicts broad-scale revegetation patterns following sand mining on North Stradbroke Island,south-eastern Queensland,Australia.Methods:Based on an ecological timeline spanning 4–20 years post-rehabilitation,the structure of these ecosystems(n=146)was assessed by distinguishing between periods of‘older’(pre-1995)and‘younger’(post-1995)rehabilitation practices.Results:The general rehabilitation outlook appeared promising,whereby an adequate forest composition and suitable levels of native biodiversity(consisting of mixed-eucalypt communities)were achieved across the majority of rehabilitated sites over a relatively short time.Still,older sites(n=36)appeared to deviate relative to natural analogues as indicated by their lack of under-storey heath and simplified canopy composition now characterised by mono-dominant black sheoak(Allocasuarina littoralis)reaching up to 60%of the total tree density.These changes coincided with lower soil fertility parameters(e.g.,total carbon,total nitrogen,and nutrient holding capacity)leading us to believe that altered growth conditions associated with the initial mining disturbance could have facilitated an opportunistic colonisation by this species.Once established,it is suspected that the black sheoak’s above/belowground ecological behaviour(i.e.,relating to its leaf-litter allelopathy and potential for soil-nitrogen fixation)further exacerbated its mono-dominant distribution by inhibiting the development of other native species.Conclusions:Although rehabilitation techniques on-site have undergone refinements to improve site management,our findings support that putative changes in edaphic conditions in combination with the competitive characteristics of some plant species can facilitate conditions leading to alternative ecological outcomes among rehabilitated ecosystems.Based on these outcomes,future studies would benefit from in depth spatio-temporal analyses to verify these mechanisms at finer investigative scales.