The Belterra Clay on the bauxite deposits of Rondon do Pará, Eastern Amazon

Negrão, Leonardo Boiadeiro Ayres; Costa, Marcondes Lima da; Pöllmann, Herbert

doi:10.1590/2317-4889201820180128

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Brazilian Journal of Geology

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ARTICLE • Braz. J. Geol. 48 (03) • Jul-Sep 2018 • https://doi.org/10.1590/2317-4889201820180128 copy

The Belterra Clay on the bauxite deposits of Rondon do Pará, Eastern Amazon

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

Bauxite deposits in the Amazon region are commonly covered by yellowish clays which can reach up to 25m thick, known as Belterra Clay (BTC). In Rondon do Pará, Eastern Amazon, BTC is 13m thick and covers world-class bauxite reserves. Three pilot bauxite mines were investigated in Rondon do Pará for an initial characterization of the local BTC. In discordant contact with the lateritic profile, the BTC has reddish brown colors at its base to ocher tones towards the top. It has a massive structure with silt-clayey texture and nodular bauxitic fragments at its base. Rietveld mineral quantification of the material attests that it is dominated by kaolinite, with goethite, gibbsite, hematite, anatase and residual quartz. The thermal behavior of the material also confirms its mineralogical composition. Kaolinite is of low structural order, which was considered the main difficulty in the application of the Rietveld method. Goethite has up to 33 mol% of Al. As observed by scanning electron microscopy (SEM), the minerals represent pseudo-hexagonal crystals measuring from 150 to 700 nm. The BTC in the studied area is correlated to BTC on others bauxitic deposits of the Amazon region, suggesting this material experienced the same genesis and geological evolution, probably during the Pliocene.

Keywords:
Bauxite; Mineralogy, Kaolinite, Al-Goethite, Rietveld, Chemistry

Mineral	Crystal system	Authors	ICSD code
Kaolinite	Triclinic C1	Bish & Von Dreele (1989Bish D.L., Von Dreele R.B. 1989. Rietveld refinement of non-hydrogen atomic positions in kaolinite. Clays and Clay Minerals, 37(4): 289-296.)	63192
Goethite	Orthorhombic Pbnm	Li Deyu et al. (2006Li D., O’ Connor B.H., Low I.M., van Riessen A., Toby B.H. 2006. Mineralogy of Al-substituted goethites. Powder Diffraction, 21:289-299. https://dx.doi.org/10.1154/1.2358358 https://dx.doi.org/10.1154/1.2358358... )	109411
Gibbsite	Monoclinic P 1 21/n 1	Saalfeld & Wedde (1974Saalfeld H., Wedde M. 1974. Refinement of the crystal structure of gibbsite, Al(OH)3. Zeitschrift Fur Kristallographie, 139:129-135. http://dx.doi.org/10.1524/zkri.1974.139.1-2.129 http://dx.doi.org/10.1524/zkri.1974.139.... )	6162
Hematite	Trigonal R -3 c H	Sadykov et al. (1996Sadykov V.A., Isupova L.A., Tsybulya S.V., Cherepanova S.V., Litvak G.S., Burgina E.B., Kustova G.N., Kolomiichuk V.N., Ivanov V.P., Paukshtis E.A., Golovin A.V., Avvakumov E.G. 1996. Effect of mechanical activation on the real structure and reactivity of iron (III) oxide with corundum-type structure, Journal of Solid State Chemistry, 123:191-202. https://doi.org/10.1006/jssc.1996.0168 https://doi.org/10.1006/jssc.1996.0168... )	82137
Anatase	Tetragonal I 41/a m d Z	Weirich et al. (2000Weirich T.E., Winterer M., Seifried S., Hahn H., Fuess H. 2000. Rietveld analysis of electron powder diffraction data from nanocrystalline anatase, TiO2. Ultramicroscopy, 81:263-270.)	92363
Quartz	Trigonal P 32 2 1	d’Amour et al. (1979D’Amour H., Denner W., Schulz H. 1979. Structure determination of alpha-quartz up to 68*108 Pa. Acta Crystallographica B, B35:550-555. https://doi.org/10.1107/S056774087900412X https://doi.org/10.1107/S056774087900412... )	16331

Pilot mine	Depth (m)	Kaolinite		Al-Goethite		Gibbsite		Hematite		Anatase		Quartz
Pilot mine	Depth (m)	R	S	R	S	R	S	R	S	R	S	R	S
Branco	0.8	70.2	72.3	17.5	17.5	4.2	2.2	0.5	0.5	2.4	2.4	1.5	1.5
	5.5	72.8	75.1	16.1	15.8	3.1	1.7	1.6	1.6	2.7	2.5	-	-
	10.5	73.0	73.6	15.0	15.9	4.6	1.8	2.1	2.1	2.4	2.6	0.3	0.3
Ciríaco	1.0	60.6	61.4	14.9	16.6	13.4	13.5	-	-	2.9	2.6	2.5	2.5
	2.5	61.9	64.0	14.9	14.8	14.1	13.2	1.1	1.1	3.0	2.7	0.7	0.7
	5.0	61.1	62.9	13.9	15.5	14.4	13.9	1.4	1.4	2.9	2.7	0.5	0.5
	7.5	64.6	62.5	14.8	15.8	15.2	15.1	1.3	1.3	2.7	2.7	-	-
	10	58.2	58.9	13.6	14.5	20.7	18.4	2.0	2.0	2.3	2.8	0.5	0.5
	12	55.9	58.6	13.8	13.5	19.2	19.4	2.8	2.8	2.5	2.7	-	-
Décio	0.8	75.3	70.1	15.7	16.2	2.3	3.8	-	-	2.9	2.5	1.6	1.6
	4.5	72.2	72.8	13.4	13.4	4.4	4.3	2.2	2.2	2.4	2.5	0.6	0.6
	7.2	75.3	72.9	14.5	13	1.3	4.9	2.6	2.6	2.6	2.5	-	-
	10	74.7	72.2	15.1	11.4	2.4	5.3	3.7	3.7	2.4	2.6	-	-

Pilot mine	Depth (m)	c Al-goethite cell parameter	Al (mole%)
Branco	0.5	2.966213	33.3
	5.5	2.967304	32.7
	10	2.964874	34.1
Ciríaco	1	2.969160	31.6
	2.5	2.969180	31.6
	5.0	2.968970	31.7
	7.5	2.968692	31.9
	10	2.967798	32.4
	12	2.968117	32.2
Décio	0.8	2.970317	31.0
	4.5	2.967872	32.4
	7.2	2.968450	32.0
	10	2.968293	32.1

Pilot mine	Depth	amorphous SiO₂	amorphous Fe₂O₃	SiO₂ + Fe₂O₃ (amorphous)	X-ray amorphous (Rietveld)
Branco	0.8	0.75	0.71	1.46	3.7
	5.5	0.83	0.40	1.23	3.8
	10.5	0.62	0.26	0.88	2.6
Ciríaco	1.0	0.53	0.86	1.39	5.7
	2.5	0.43	0.60	1.03	4.9
	5.0	0.43	0.49	0.91	5.9
	7.5	0.51	0.43	0.94	1.2
	10	0.39	0.74	1.13	2.8
	12	0.43	0.89	1.31	5.8
Décio	0.8	0.82	0.71	1.53	3.1
	4.5	0.73	0.83	1.56	4.8
	7.2	0.71	0.63	1.34	3.8
	10	0.73	1.57	2.30	0.8

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