New Computerized Method for the Geochemical Classification of Precambrian Carbonate Rocks: Case of a Set of African Cap Carbonates

Hélène Miche, Roland Simler, Pascal Affaton, Olivia Mickala, Florent Boudzoumou, Michel Mbina

Aix-Marseille Université, CNRS, IRD, CEREGE UM 34, Aix en Provence, France.
Département de Géologie, Faculté des Sciences et Techniques, Université Marien Ngouabi de Brazzaville, Brazzaville, République du Congo.
Département de Géologie, Université des Sciences et Techniques de Masuku, Franceville, Gabon.
Université d’Avignon et des pays du Vaucluse, INRA, EMMAH, UMR 1114, LHA, Avignon, France.

DOI: 10.4236/ijg.2013.410A005                

Abstract

Post-sedimentary transformations have masked or completely obliterated the structures and textures of Precambrian carbonate rocks. Therefore, methods of classification of the carbonate rocks founded on the observation of primary structures or textural characteristics are ill-adapted. Consequently, only certain geochemical classification methods allow us to distinguish the various rock-types in the case of Neoproterozoic carbonates. After presenting the most suitable geochemical classifications, we propose a new classification into 14 groups based on a regular ternary diagram with computerized data input. For each sample of carbonate rock, analysis of calcium and magnesium contents allows us to calculate the input data for our diagram i.e. the percentages of Calcite, Dolomite and Insoluble Residue. To automate the application of this diagram, input parameters are created in a descriptive file “Roches.ternaires.txt” using an option called “Ternaires” in the “Diagrammes” software developed by Roland Simler. Thirty cap carbonates of Africa are used to validate this new method.

Keywords

Carbonate Rock; Cap Carbonate; Ternary Diagram; Software; Calcite; Dolomite

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. J. Dunham, “Classification of Carbonate Rocks According to Their Depositional Texture,” In: W. E. Ham, Ed., Classification of Carbonate Rocks: Tulsa, OK, American Association of Petroleum Geologist Memoirs, 1962, pp. 108-121.
[2]	A. F. Embry and J. E. Klovan, “A Late Devonian reef tract on northeastern Banks Island,” Bulletin of Canadian Petroleum Geology, Vol. 19, No. 4, 1971, pp. 730-781.
[3]	R. L. Folk, “Practical Petrographic Classification of Limestones,” American Association of Petroleum Geologist Bulletin, Vol. 43, No. 1, 1959, pp. 1-38.
[4]	R. L. Folk, “Spectral Subdivision of Limestones Types,” In: W. E. Ham, Ed., Classification of Carbonates Rocks. A Symposium, Tulsa, OK, American Association of Petroleum Geologist Memoirs, 1962, pp. 62-84.
[5]	V. P. Wright, “A Revised Classification of Limestones,” Sedimentary Geology, Vol. 76, No. 3-4, 1992, pp. 177-185. http://dx.doi.org/10.1016/0037-0738(92)90082-3
[6]	G. V. Chilingar, “Use of Ca/Mg ratio of Limestones and Dolomites as a Geological Tool,” Ph.D. Dissertation, Univ. Southern California, 1956.
[7]	G. V. Chilingar, “Classification of Limestones and Dolomites on Basis of Ca/Mg Ratio,” Journal of Sedimentary Petrology, Vol. 27, No. 2, 1957, pp. 187-189.
[8]	A. Carrozi, “Petrographie des Roches Sédimentaires,” F. Rouge et cie, Lausanne, 1953, 250 p.
[9]	R. W. Fairbridge, “The Dolomite Question,” In: R. J. Le Blanc and J. G. Breeding, Eds., Regional Aspects of Carbonate Deposition, Tulsa Society of Economic Paleontologists and Mineralogists, Special Publications, 1957, p. 128. http://dx.doi.org/10.2110/pec.57.01.0125
[10]	J. Rodgers, “Terminology of Limestone and Related Rocks: An Interim Report,” Journal of Sedimentary Petrology, Vol. 24, No. 4, 1954, pp. 225-234.
[11]	B. Martinet and J. Sougy, “Utilisation Pratique des Classifications Chimiques des Roches Carbonatées,” C. R. Somm. Soc. Géol. Fr., 1957, p 367 (résumé), Annales de la Faculté des Sciences de Dakar, 1957[1961], pp. 81-92.
[12]	K. E. Chave, “Aspects of the Biochemistry of Magnesium,” Journal of Geology, Vol. 62, 1954, pp. 266-283.
[13]	B. Martinet, M. Deynoux and R. Trompette, “Méthode de Dosage de CaO et MgO dans les Roches Carbonatées,” Travaux des Laboratoires des Sciences de la Terre, Série B, No. 2, St Jérome, Marseille, 1969.
[14]	W. E. Dean, “Determination of Carbonate and Organic Matter in Calcareous Sediments and Sedimentary Rocks by Loss on Ignition: Comparison with Other Methods,” Journal of Sedimentary Petrology, Vol. 44, No. 1, 1974, pp. 242-248.
[15]	R. W. Murray, D. J. Miller and K. A. Kryc, “Analysis of Major and Trace Elements in Rocks, Sediments, and Interstitial Waters by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES),” ODP Technical Note, Vol. 29, 2000. http://dx.doi.org/10.2973/odp.tn.29.2000
[16]	J. Sougy, “Les Formations Paléozoiques du Zemmour noir (Mauritanie septentrionale): Etude Stratigraphique, Pétrographique et Paléontologique,” Thèse d’Etat, Université de Nancy, 1964, 695 p.
[17]	V. Caron, E. Ekomane, G. Mahieux, P. Moussango and E. Ndjeng, “The Mintom Formation (New): Sedimentology and Geochemistry of a Neoproterozoic, Paralic Succession in South-East Cameroon,” Journal of African Earth Sciences, Vol. 57, No. 4, 2010, pp. 367-385. http://dx.doi.org/10.1016/j.jafrearsci.2009.11.006
[18]	H. E. Frimmel, L. Tack, M. S. Basei, A. P. Nutman and A. Boven, “Provenance and Chemostratigraphy of the Neoproterozoic West Congolian Group in the Democratic Republic of Congo,” Journal of African Earth Sciences, Vol. 46, No. 3, 2006, pp. 221-239. http://dx.doi.org/10.1016/j.jafrearsci.2006.04.010
[19]	A. Nédélec, P. Affaton, C. France-Lanord, A. Charrière and J. Alvaro, “Sedimentology and Chemostratigraphy of the Bwipe Neoproterozoic cap Dolostones (Ghana, Volta Basin): A Record of Microbial Activity in a Peritidal Environment,” Comptes Rendus Geoscience, Vol. 339, No. 3-4, 2007, pp. 223-239. http://dx.doi.org/10.1016/j.crte.2005.06.002
[20]	R. Simler, Software “Diagrammes,” Laboratoire d’Hydrologie d’Avignon, Université d’Avignon et pays du Vaucluse, France. http://www.lha.univ-avignon.fr
[21]	J. Delgado Rodrigues, “Proposed Geotechnical Classification of Carbonate Rocks Based on Portuguese and Algerian Examples,” Engineering Geology, Vol. 25, No. 1, 1988, pp. 33-43. http://dx.doi.org/10.1016/0013-7952(88)90017-8