@article{fdi:010069923,
  title = {{O}rigin of calcium in pedogenic carbonate nodules from silicate watersheds in the {F}ar {N}orth {R}egion of {C}ameroon : respective contribution of in situ weathering source and dust input},
  author = {{D}ietrich, {F}. and {D}iaz, {N}. and {D}eschamps, {P}ierre and {N}gounou {N}gatcha, {B}. and {S}ebag, {D}avid and {V}errecchia, {E}.{P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{S}ignificant amounts of pedogenic {C}a-carbonate nodules have been observed in the {F}ar {N}orth {R}egion of {C}ameroon in the carbonate-free watershed of the {M}ayo {T}sanaga, thus a priori not favourable for carbonate nodules accumulations. {T}hese nodules are associated with a {C}lay-{R}ich {P}arent {M}aterial ({CRPM}), covering either a granitic (upstream) or a greenstone bedrock (downstream). {I}n this peculiar context, the amount of pedogenic carbonate nodules represents large quantities of {C}a and {C}. {T}herefore, determining the {C}a sources for pedogenic carbonate nodules is a key point regarding the mechanisms leading to carbonate nodule precipitation and their role in the biogeochemical cycle of {C}a. {T}hree sites, two on granite and one on greenstone, were studied by combining {S}r et {N}d isotope systematics in order to assess the {C}a sources of carbonate nodules and the origin of the {CRPM} associated with nodules. {C}arbonate nodules have a distinct {S}r isotopic composition in each profile, pointing to the contribution of a local source for {C}a. {S}r isotopic compositions of plagioclases and carbonate nodules display a concomitant variation in each profile, indicating that plagioclases acted as a {S}r, and thus {C}a, source for the carbonate nodules. {N}evertheless, carbonate nodules have a higher {S}r isotopic signature than plagioclases, implying the contribution of another more radiogenic {S}r source. {S}r and {N}d isotope data from the {CRPM} show that it is a mixture of weathered bedrock compounds and {S}aharan dust. {T}his result highlights two other potential {S}r and {C}a sources: biotite and {S}aharan dust. {C}alculations of their respective contributions demonstrate that in situ weathering significantly adds to the {C}a source of nodules. {T}his result contrasts with many other studies from similar settings that highlight the importance of allochthonous - marine, aeolian - inputs. {T}his conclusion points out that a substantial part of {C}a is transferred from the local bedrock to the carbonate nodules. {T}his mechanism seems to have been possible as peculiar edaphic conditions preserved the primary {C}a sources, making in situ weathering a significant process for providing {C}a.},
  keywords = {{CAMEROUN} ; {MAYO} {TSANAGA}},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {460},
  numero = {},
  pages = {54--69},
  ISSN = {0009-2541},
  year = {2017},
  DOI = {10.1016/j.chemgeo.2017.04.015},
  URL = {https://www.documentation.ird.fr/hor/fdi:010069923},
}