Mineralogical characterization of clay mineral assemblages from Rio de Janeiro pegmatites to identify kaolinite and/or halloysite deposits

Salgado-Campos, V. M. J.; Bertolino, L. C.; Silva, F. J. da; Mendes, J. C.

doi:10.1590/0366-69132020663802928

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Articles • Cerâmica 66 (380) • Oct-Dec 2020 • https://doi.org/10.1590/0366-69132020663802928 copy

Mineralogical characterization of clay mineral assemblages from Rio de Janeiro pegmatites to identify kaolinite and/or halloysite deposits

Caracterização mineralógica das associações de argilominerais em pegmatitos do estado do Rio de Janeiro com enfoque na identificação de depósitos de caulinita e/ou halloysita

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This study reports the mineralogical characterization of kaolin occurrences in the State of Rio de Janeiro, Brazil, to identify new kaolinite and halloysite deposits. Samples were collected in 10 pegmatites with varying sizes for X-ray diffractometry, chemical analysis by X-ray fluorescence, and scanning electron microscopy studies. The results indicated that the kaolin occurrences were of weathered origin, wherein some places there were occurrences of tubular halloysite. Concerning the regolith stratigraphy, samples located in the saprock zone were found to contain kaolinite and/or halloysite contents from 0 to 10.1%, while those located in the saprolite zone contained kaolinite and/or halloysite contents from 16.3% to 34.9%. Kaolinite and/or halloysite-7Å were formed from plagioclase weathering instead of K-feldspar or mica, and the halloysite-7Å occurrence was related to samples in regions with a higher degree of weathering.

Keywords:
kaolin; kaolinite; halloysite; Rietveld; Rio de Janeiro

Table I Sampling sites in the Cantagalo-São Fidélis and Niterói-Rio Bonito areas.

Pegmatite	Number of samples	Area	Municipality	Latitude	Longitude	Elevation (m)
Córrego do Ouro (CA-3)	2	Cantagalo-São Fidélis	Cantagalo	-21.842	-42.217	332
Boa Sorte Superior (CA-2)	0*	Cantagalo-São Fidélis	Cantagalo	-21.863	-42.233	370
Esmério (CA-4)	2	Cantagalo-São Fidélis	Cantagalo	-21.875	-42.251	426
RB-1	2	Niterói-Rio Bonito	Rio Bonito	-22.708	-42.607	74
RB-2	2	Niterói-Rio Bonito	Rio Bonito	-22.703	-42.593	71
RB-3	2	Niterói-Rio Bonito	Rio Bonito	-22.754	-42.593	97
RB-4	1	Niterói-Rio Bonito	Rio Bonito	-22.700	-42.598	74
RB-5	2	Niterói-Rio Bonito	Rio Bonito	-22.719	-42.622	75
RB-6	1	Niterói-Rio Bonito	Rio Bonito	-22.786	-42.554	71
RB-7	1	Niterói-Rio Bonito	Rio Bonito	-22.702	-42.589	59
Calaboca-Rebentão (MA-1)	0*	Niterói-Rio Bonito	Maricá	-22.895	-42.946	41
SG-1	1	Niterói-Rio Bonito	São Gonçalo	-22.863	-42.987	63
SG-2	0*	Niterói-Rio Bonito	São Gonçalo	-22.863	-42.987	76
SG-3	0*	Niterói-Rio Bonito	São Gonçalo	-22.870	-42.987	96
SG-4	0*	Niterói-Rio Bonito	São Gonçalo	-22.870	-42.984	85

Table II Chemical compositions (wt%) used in the conversion of results from quantitative mineral analysis to chemical analysis.

Content	Mo	Ms	Kln/Hly	Qtz	Kfs	Pl
SiO₂	43.77	45.21	43.22	100.00	64.76	67.39
Al₂O₃	18.57	38.36	42.82	0.00	18.32	20.35
CaO	1.02	0.00	0.00	0.00	0.00	1.07
Na₂O	1.13	0.00	0.00	0.00	0.00	11.19
K₂O	0.00	11.81	0.00	0.00	16.92	0.00
LOI	36.09	4.07	13.96	0.00	0.00	0.00
F	0.00	0.55	0.00	0.00	0.00	0.00
Sum	100.58	100.00	100.00	100.00	100.00	100.00

Table III Classification by Pearson correlation coefficients.

ρ value (+ or -)	Interpretation
0.00 to 0.19	Very weak correlation
0.20 to 0.39	Weak correlation
0.40 to 0.69	Moderate correlation
0.70 to 0.89	Strong correlation
0.90 to 1.00	Very strong correlation

Table IV Results of quantitative mineral analysis of the bulk fractions obtained by the Rietveld method and its figures of merit and chemical analysis by XRF in oxides and calculated indexes.

	CA-3A	CA-3B	CA-4A	CA-4B	RB-1A	RB-1B	RB-2A	RB-2B	RB-3A	RB-3B	RB-4	RB-5A	RB-5B	RB-6	RB-7	SG-1C
Mineralogy (wt%)
Sm	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	3.1	0.0	7.2	0.0	0.0	0.0	0.0
Mi+Ill	4.5	3.1	1.0	4.5	3.9	13.0	45.3	46.2	8.5	46.9	1.5	7.7	9.5	22.9	41.4	16.0
Kln+Hly	0.0	0.0	4.0	4.5	6.4	1.6	16.3	6.6	1.7	0.0	34.9	18.5	17.2	23.9	33.3	10.1
Qtz	31.9	27.8	13.6	44.8	9.2	35.5	38.4	47.2	31.8	50.0	27.1	44.3	48.5	36.4	25.4	43.3
Kfs	2.6	7.1	1.2	6.0	20.8	23.9	0.0	0.0	2.8	0.0	36.6	22.3	24.8	16.8	0.0	24.7
Pl	60.9	61.9	80.2	40.0	59.7	26.0	0.0	0.0	55.3	0.0	0.0	0.0	0.0	0.0	0.0	5.8
Sum	99.9	100.0	100.0	99.8	100.0	100.0	100.0	100.0	100.1	100.0	100.1	100.0	100.0	100.0	100.1	99.9
Rietveld (wt%)
SiO₂	76.7	75.6	70.6	79.8	67.4	75.1	66.1	71.1	75.4	72.7	66.5	73.4	76.3	68.0	58.6	74.9
Al₂O₃	14.6	15.1	18.6	12.9	20.2	15.4	24.4	20.6	15.7	18.6	22.2	16.3	15.6	22.1	30.2	16.2
CaO	0.7	0.7	0.9	0.4	0.7	0.3	0.0	0.0	0.6	0.0	0.0	0.1	0.0	0.0	0.0	0.1
Na₂O	6.8	6.9	9.0	4.5	6.7	2.9	0.0	0.0	6.2	0.0	0.0	0.1	0.0	0.0	0.0	0.7
K₂O	1.0	1.6	0.3	1.6	4.0	5.6	5.4	5.5	1.5	5.6	6.4	4.7	5.3	5.6	4.9	6.1
LOI	0.2	0.2	0.6	0.8	1.1	0.8	4.1	2.8	0.6	3.0	4.9	5.5	2.8	4.3	6.3	2.1
Sum	99.99	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Chemistry (wt%)
SiO₂	70.80	69.70	63.80	75.10	64.50	73.60	60.40	70.80	72.30	71.20	63.00	67.40	70.90	67.70	57.00	71.50
Al₂O₃	18.20	18.70	24.10	16.60	22.20	15.60	26.40	16.00	17.30	18.10	25.90	23.30	20.50	21.90	30.10	19.40
Fe₂O₃	0.47	0.60	0.27	0.26	0.74	1.00	2.60	3.30	0.46	1.60	0.48	0.68	0.80	1.00	1.10	0.91
MnO	0.00	0.00	0.00	0.00	0.00	0.00	0.15	0.05	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
MgO	0.17	0.15	0.00	0.00	0.27	0.50	0.46	0.81	0.56	0.83	0.28	0.40	0.17	0.58	0.53	0.24
CaO	1.40	1.50	2.50	1.40	0.15	0.51	0.00	0.00	0.27	0.05	0.00	0.00	0.00	0.00	0.00	0.20
Na₂O	7.10	7.30	7.40	4.20	6.20	3.20	0.00	0.00	4.50	0.19	0.31	0.17	0.22	0.23	0.00	1.10
K₂O	1.00	1.20	0.51	1.10	3.40	4.10	2.20	2.30	1.40	2.60	4.70	2.60	4.00	2.70	2.00	3.50
TiO₂	0.00	0.00	0.00	0.00	0.05	0.15	0.15	0.83	0.05	0.51	0.00	0.19	0.05	0.10	0.43	0.00
P₂O₅	0.00	0.00	0.00	0.00	0.11	0.05	0.11	0.05	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
ZrO₂	0.00	0.00	0.00	0.00	0.00	0.00	0.13	0.05	0.00	0.00	0.00	0.00	0.00	0.00	0.17	0.00
LOI	0.65	0.74	1.20	1.20	2.40	1.20	7.20	6.00	3.20	5.10	5.40	5.20	3.40	5.70	8.80	2.80
Sum	99.79	99.89	99.78	99.86	100.02	99.91	99.80	100.19	100.04	100.18	100.07	99.94	100.04	99.91	100.13	99.65
Index
CIA	54.32	53.84	58.25	60.93	61.07	59.48	91.73	86.54	64.77	84.91	82.23	88.28	81.38	86.90	93.29	76.49
RE	0.0	0.1	4.6	8.2	7.0	2.5	26.5	12.5	2.5	6.2	47.8	46.1	33.4	37.6	44.6	17.8
Parameter
ρ	0.998	0.998	0.994	0.998	0.999	1.000	0.995	0.995	0.999	0.999	0.997	0.993	0.997	0.999	0.998	0.998
R²	0.995	0.995	0.988	0.996	0.998	0.999	0.990	0.990	0.997	0.997	0.994	0.985	0.993	0.998	0.996	0.996
Figure of merit*
GOF	2.32	2.44	2.23	1.96	2.06	2.20	2.63	2.62	2.31	2.95	2.44	3.07	2.33	2.13	3.82	2.85
Rexp	4.55	4.32	4.83	4.78	4.59	4.47	3.68	3.56	4.44	4.13	4.73	4.31	4.41	4.22	4.02	4.41
Rwp	10.57	10.55	10.75	9.36	9.44	9.82	9.67	9.34	10.27	12.19	11.56	13.24	10.25	9.01	15.36	12.54

Table V Results of quantitative mineral analysis (wt%) of the clay minerals based on the X-ray diffractograms of ethylene glycol-solvated, oriented slides (Biscaye’s method) 38.

Sample	Re	Mo	Ill	Kln/Hly
CA-3A	0	67	24	10
CA-3B	0	47	22	31
CA-4A	0	0	23	77
CA-4B	0	0	17	82
RB-1A	0	91	1	7
RB-1B	0	94	3	3
RB-2A	7	0	86	6
RB-2B	0	0	99	1
RB-3A	0	93	6	1
RB-3B	20	1	60	19
RB-4	0	0	12	88
RB-5A	0	93	3	3
RB-5B	0	1	40	59
RB-6	0	69	0	31
RB-7	0	0	74	26
SG-1C	0	8	22	70

Table VI Pearson correlation matrix between the chemical index of alteration (CIA) and the results of quantitative mineral and chemical analyses.

	CIA	Sm	Mi+Ill	Kln+Hly	Qtz	Kfs	Pl	Fs	SiO₂	Al₂O₃	Fe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	TiO₂	P₂O₅	ZrO₂
CIA
Sm	0.32
Mi+Ill	0.70	0.04
Kln+Hly	0.70	0.05	0.16
Qtz	0.45	0.34	0.42	-0.05
Kfs	0.05	0.11	-0.49	0.40	-0.01
Pl	-0.91	-0.29	-0.62	-0.63	-0.65	-0.28
Fs	-0.92	-0.30	-0.83	-0.49	-0.68	0.12	0.92
SiO₂	-0.45	0.03	-0.26	-0.67	0.53	0.07	0.17	0.20
Al₂O₃	0.51	0.07	0.15	0.78	-0.42	0.07	-0.26	-0.24	-0.95
Fe₂O₃	0.57	-0.03	0.85	0.03	0.40	-0.35	-0.53	-0.68	-0.14	-0.03
MnO	0.39	-0.12	0.56	0.08	0.17	-0.34	-0.28	-0.42	-0.35	0.24	0.72
MgO	0.59	0.22	0.78	0.09	0.37	-0.23	-0.56	-0.67	-0.03	-0.09	0.69	0.24
CaO	-0.76	-0.22	-0.51	-0.51	-0.39	-0.34	0.81	0.70	0.16	-0.19	-0.47	-0.22	-0.67
Na₂O	-0.94	-0.29	-0.64	-0.64	-0.62	-0.23	0.98	0.93	0.20	-0.29	-0.53	-0.30	-0.59	0.82
K₂O	0.37	0.04	0.02	0.45	0.17	0.83	-0.60	-0.27	-0.03	0.09	0.11	-0.06	0.22	-0.69	-0.56
TiO₂	0.54	0.19	0.81	0.04	0.38	-0.41	-0.49	-0.67	-0.07	-0.07	0.79	0.24	0.79	-0.41	-0.51	0.02
P₂O₅	0.05	-0.19	0.28	-0.10	-0.25	-0.04	0.00	-0.01	-0.28	0.10	0.52	0.66	0.18	-0.26	0.00	0.21	0.15
ZrO₂	0.55	-0.15	0.67	0.46	-0.05	-0.44	-0.37	-0.55	-0.70	0.62	0.51	0.58	0.30	-0.29	-0.39	-0.12	0.43	0.32
LOI	0.94	0.20	0.74	0.73	0.22	-0.10	-0.77	-0.84	-0.62	0.62	0.57	0.43	0.64	-0.72	-0.82	0.24	0.58	0.14	0.72

Table VII Comparison between the results of quantitative mineral analyses of the three most interesting kaolin occurrences from Rio de Janeiro, two giant sedimentary kaolin deposits at the North Brazilian region, and the Campo Alegre kaolin deposit in Santa Catarina, Brazil.

Mineralogy	Sedimentary deposits ²⁸28 I.R. Wilson, H. Souza Santos, P. Souza Santos, Clay Miner. 41, 3 (2006) 697.			Campo Alegre ²⁷27 M.T.G. De Oliveira, S.M.A. Furtado, M.L.L. Formoso, R.A. Eggleton, N. Dani, An. Acad. Bras. Ciênc. 79, 4 (2007) 665.			This study
Mineralogy	Capim River	Jari River	Ox1	Inc2a	Ce2m	RB-4	RB-6	RB-7
Mica+illite	0.0	0.0	6.4	20.9	48.0	1.5	22.9	41.4
Kaolinite+halloysite	100.0	100.0	35.0	65.8	44.3	34.9	23.9	33.3
Gibbsite	0.0	0.0	1.5	0.0	0.0	0.0	0.0	0.0
Quartz	0.0	0.0	4.5	13.2	7.7	27.1	36.4	25.4
K-feldspar	0.0	0.0	52.5	0.0	0.0	36.6	16.8	0.0
Sum	100.0	100.0	99.9	99.9	100.0	100.1	100.0	100.1

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