@article{fdi:010058865,
  title = {{P}otentially toxic metals in ultramafic mining materials : identification of the main bearing and reactive phases},
  author = {{R}aous, {S}. and {E}chevarria, {G}. and {S}terckeman, {T}. and {H}anna, {K}. and {T}homas, {F}. and {M}artins, {E}. {S}. and {B}ecquer, {T}hierry},
  editor = {},
  language = {{ENG}},
  abstract = {{M}odeling the geochemical behaviour of metals in spoil materials is prerequisite to the rehabilitation of lateritic nickel mining sites to avoid environmental contamination. {T}he global aim of this work was to assess the different parameters controlling the release of {N}i and other trace metals ({C}o, {C}u, {C}r and {M}n) from model materials generated by mining activities in nickeliferous laterites from {G}oals {S}tate ({B}razil). {T}his work was undertaken as a first part in a geochemical modeling project and consisted in the characterisation of the bearing phases and sources of such metals in representative materials from the mine. {O}res and spoils had similar mineralogical compositions: i) mainly smectites and talc in garnierites and ii) goethite and hematite in limonites; we therefore concentrated our analyses on the purest materials. {G}arnierite was richer in {N}i and poorer in {C}r than limonite. {I}n the first one, the richest phase in {N}i was smectite ({F}e: 8.8 at.%; {A}l: 3.3 at.%; {M}g: 1.8 at.%; {C}r: 0.5 at.%; {N}i: 1.2 at.%) whereas chromiferous spinels contained high concentrations of {C}r ({F}e: 9.6 at.%; {A}l: 17.6 at.%; {M}g: 4.1 at.%; {C}r: 17.6 at.%). {I}n {L}imonite, {N}i and {C}r were mainly borne by goethite ({F}e: 37.6 at.%; {A}l: 1.8 at.%; {C}r: 0.2 at.%; {N}i: 0.5 at.%) and chromiferous spinels for {C}r. {F}ine microscopy and spectroscopy allowed us to observe the structure of the minerals in both samples as well as the metal distribution in these different mineral phases. {W}e then focused on metal lability and partitioning in the different compartments revealed by the mineralogical study. {I}n the garnierite, exchangeable {N}i (10% of total {N}i) was mainly located between the layers of smectite as outer sphere complexes, and was thus easily available. {C}hromium, either located as octahedral or tetrahedral substitution in the smectites of the garnierite, or sequestered in chromiferous spinel lattices, was poorly available in both cases. {I}n the typical limonite, both {N}i and {C}r were part of the goethite lattice but most of the {C}r was associated with chromiferous spinel, which could be a primary source of {C}r({III}). {T}he mobility of the {N}i and {C}r found in goethite was low. {H}owever, limonite presented very high exchangeable {C}r({VI}) contents, (2% of total {C}r) in the form of inner-sphere complexes at the goethite surface. {C}r({VI}) is probably formed through {C}r({III}) oxidation by {M}n oxides. {N}ow that the reactive phases are identified and characterised, further work will model the reactivity of model bearing phases of {N}i and {C}r and compare the geochemical simulation with actual mobility data.},
  keywords = {{O}res ; {S}poils ; {M}etal-bearing smectite ; {M}etal bearing-goethite ; {N}ickel ; {C}hromium ; {BRESIL}},
  booktitle = {},
  journal = {{G}eoderma},
  volume = {192},
  numero = {},
  pages = {111--119},
  ISSN = {0016-7061},
  year = {2013},
  DOI = {10.1016/j.geoderma.2012.08.017},
  URL = {https://www.documentation.ird.fr/hor/fdi:010058865},
}