Erick Ramanaidou

Mineralogy and crystal chemistry of “garnierites” in the Goro lateritic nickel deposit, New Caledonia

The mineralogy and crystal chemistry of “garnierites” in saprolitic ore from the Goro lateritic nickel deposit, New Caledonia, was investigated using optical and scanning electron microscopy, X-ray diffraction (XRD) and electron-microprobe analyses. These conspicuously, green-coloured phases occur either as sub-mm to cm-sized veins or as macroscopic (sub-cm sized) “booklets”. Veins comprised ~ 10 A (2:1) talc-like minerals identified as species of the Ni-kerolite/pimelite Ni for Mg solid solution series, with Ni contents ranging from 10 to 24 % NiO. Mineral nomenclature, defined by the inverse relationship between Ni and Mg content, varied continuously over the scale of several hundred micrometres. Pimelite, defined as containing > 1.5 Ni per formula unit (p.f.u.), was the main 10 A phase for one vein core whereas at the vein edges where the Ni content decreased to < 1.5 Ni p.f.u. (and Mg increased) kerolite was identified. “Booklets” comprised the ~ 7 A (1:1) serpentine-like phase, nepouite (Mg0.67Ni1.59Fe0.053+) (Si2.17Al0.22)O5(OH)4 with Ni contents averaging 30 % NiO and occurred as accordion-like structures supported in an undifferentiated matrix of mixed ~ 7 A and ~ 10 A phases.

Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil

Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtainingdirect reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capitao do MatoMine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drillcore and open pit samples.Hematite is the main component of the samples and occurs as granular crystals

A Synopsis of the Channel Iron Deposits of the Hamersley Province (Western Australia)

Abstract The channel iron deposit type or CID is one of the two major iron ore types mined in the Hamersley Province. Channel iron deposits provided around 40% of the total of 394 Mt of iron ore mined from the Hamersley Province in 2009, and the current CID resource is around 7 billion tonnes. Channel iron deposits occupy numerous meandering palaeochannels in a mature surface that includes Precambrian rocks and ferruginous Palaeogene valley fill. These palaeochannels are generally less than a kilometre but can range to several kilometres in width and from one metre to more than 100 m thick. There are two currently mined CID areas: the first in the western Hamersley Province in the Robe palaeochannel, and the second in the eastern Yandi palaeochannel. These two major CID channels extend over 100 to 150 km, with the Robe system up to 5 km wide. The granular ore facies typically contains ooids and lesser pisoids with hematite nuclei and goethite cortices, with abundant goethitised wood/charcoal fragments and goethitic peloids, minor clay, and generally minimal porous goethitic matrix. Post deposition weathering is common and produced secondary facies. Ooids and pisoids were mostly derived from the stripping of a well-vegetated, deep ferruginous surface. The peloids were derived intra-formationally from both fragmentation and reworking of desiccated goethite-rich mud. Minute wood/charcoal fragments in the soil were initially replaced by goethite and then dehydrated to hematite, forming nuclei for many ooids and pisoids. In addition, abundant, generally small (<10 mm) fragments of wood/charcoal were replaced in situ by goethite within the consolidating CID. This profusion of fossil wood, both as ooids and pisoids nuclei and as discrete fragments, as well as the local presence of kenomagnetite suggests major episodic wild fires in heavily vegetated catchments. The goethitic matrix was the result of chemically precipitated iron hydroxyoxides, resulting from leaching of iron-rich soils in an organic environment.

Hyperspectral Imaging of Iron Ores

Hyperspectral sensing is based on reflectance spectroscopy that studies light as a function of wavelength reflected or scattered from a solid surface. In reflectance spectroscopy, the most common iron oxides minerals in iron ores (hematite and goethite) have broad absorptions between 380 and 1000 nm whereas waste materials such as kaolinite, gibbsite, montmorillonite and riebeckite show narrow absorption features between 1000 and 2500 nm.

Mapping mineral chemistry of a lateritic outcrop in new Caledonia through generalized regression using Sentinel-2 and field reflectance spectra

Abstract Mining is fundamental for human development, yet it currently requires innovative spatial techniques as it faces diverse environmental and social pressures. With the free Sentinel-2 data of the Copernicus programme, new opportunities arise for studies related to nickel laterite, especially with its reported potential in mapping iron-oxide. This work utilizes samples from drill-holes extracted from Tiebaghi, New Caledonia. The chemical composition and the hyperspectral reflectance of each sample are obtained. The reflectance spectra are resampled to Sentinel-2s characteristics, and generalized linear regression was used to accurately predict Fe2O3, MgO, SiO2, Al2O3, and nickel content where three regression approaches were compared: Ridge, Elastic Net, and the Least Absolute Shrinkage and Selection Operator (LASSO). With the resulting regression models, mineral chemistry of an outcrop in the vicinity of the drill-holes is mapped by a scene of Sentinel-2. The work shows the great potential of free satellite imagery in mapping chemical characteristics of minerals and rocks. It opens up great opportunities for monitoring outcrops and for achieving more efficient mineral exploration.

Artworks and Cultural Heritage Materials: Using Multivariate Analysis to Answer Conservation Questions

The key concepts of data management systems that are applied to combinatorial and high-throughput chemical systems may also be applied to assist with answering questions involving conservation and cultural heritage materials. The chapter begins with an overview of conservation and explains what conservation is, why it is important, and how it is implemented for the preservation of cultural materials. The inherent value of most cultural materials imposes certain limitations on the types of analytical approaches that may be employed during analysis. An emphasis on noninvasive, nondestructive or microsampling is important to minimize the impact of analytical methodologies upon the artefact that is being studied, and multivariate approaches can maximize the information that may be derived from an analytical technique. In a review of nondestructive analysis and testing of museum objects, Adriaens (Spectrochimica Acta Part B: Atomic Spectroscopy 2005, 60 (12), 1503–1516) reiterates an important conservation principle, i.e. that we should aim for the maximization of information with a minimization of consumed volume of sample. Consistent with other applications in the fields of remote sensing, analysis of metadata and high-throughput or combinatorial approaches, methods for visualization of complex data, multivariate analysis and processing of high volumes of data, advanced data compression using data transformation and cluster analysis for data exploration and mining or pattern recognition are utilized. Cultural heritage studies are often directed at specific compositional and sample relational questions, due to the fact that little documentation about the specific preparation of the artefact exists. Also, because the analyst is dealing with natural materials with inherent sample variability, there is often little a priori knowledge of the sample set, so unsupervised approaches are useful for data exploration. This chapter presents a number of case studies that are used to illustrate the use of multivariate analysis (MVA) and chemometric approaches in studies of cultural artefacts and works of art. By deriving correlations, trends, clusters trajectory and anomalies or outliers in nonspatial and spatial data sets, a number of specific conservation issues are addressed. Firstly, in a multi-year study, the surface mineralogical profile of Australian Aboriginal Rock Art petroglyphs was examined using visible–near infrared reflectance spectroscopy and principal component analysis (PCA). A Cypriot pottery collection repaired with adhesives was studied using Fourier transform infrared (FTIR) spectroscopy and further historical information was revealed using PCA. The pigments and binding media used to decorate an Egyptian sarcophagus were examined with Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and X-ray absorption near-edge structure spectroscopy (XANES), and attribution studies of an Italian renaissance painting and imaging of ochre pigments using X-ray fluorescence (XRF) elemental imaging are presented.