Mineral chemistry and oxygen isotope studies on Sn (±W) mineralization from Pedra Branca Granite Massif, Central Brazil

Santos, Ítalo Kevin Morais dos; Souza, Valmir da Silva; Botelho, Nilson Francisquini; Hoyer, Ingrid de Souza; Bonfim, Luis Antonio Raposo

doi:10.1590/2317-4889202320220041

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Brazilian Journal of Geology

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Article • Braz. J. Geol. 53 (1) • 2023 • https://doi.org/10.1590/2317-4889202320220041 copy

Mineral chemistry and oxygen isotope studies on Sn (±W) mineralization from Pedra Branca Granite Massif, Central Brazil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Central Brazil hosts Paleo-Mesoproterozoic A-type granitic suites related to the Goiás Tin Province (GTP) that contain Sn (±W, Nb-Ta, REE) mineralization associated with greisen, veins, and small pegmatite bodies. The Pedra Branca granite massif (1.77–1.74 Ga) is the main representative of GTP, marked by important cassiterite (±wolframite) contents. The cassiterite contains SnO₂ = 96–100 wt. %, with the sum FeO_total, TiO₂, WO₃, Ta₂O₅, Nb₂O₅, In₂O₃, and UO₂ content below 4 wt.%, while wolframite contains WO₃ = 71.5–74.5 wt.%, FeO_total = 14.3–17.4 wt.% and MnO = 6.3–9.9 wt.%, as well as Sn, Ca, Ti, Ta, Nb, Pb, In, and U as trace elements. The δ¹⁸O data on the quartz-cassiterite pair (quartz = 9.4–10.4‰, cassiterite = 2.6–2.9 ‰) from greisen reveal a magmatic-hydrothermal signature with calculated crystallization temperatures between 410 and 485°C. However, during the Neoproterozoic Brasiliano/Pan-African Orogeny (800–500 Ma), all lithologies and ore sites were subjected to flattening, fragmentation, and mylonitic deformation. Fluid inclusion data revealed the presence of low-salinity aqueous solutions with homogenization temperatures between 215 and 100°C related to Neoproterozoic deformation. Finally, during the Phanerozoic, prolonged erosive produced Sn (±W)-rich alluvium around the Pedra Branca granitic massif.

Keywords:
cassiterite; wolframite; Pedra Branca granite massif; Goiás Tin Province; mineral chemistry; oxygen isotope

Cassiterite
Spots	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
SnO₂	99.05	98.19	98.48	96.24	97.58	98.78	98.24	97.02	97.29	99.00	99.35	98.77	98.57	98.98	99.01	98.97	98.65	99.66	98.44	99.64
FeO_tot.	0.26	0.17	0.05	0.56	1.00	0.31	0.46	0.27	0.35	0.32	0.23	0.07	0.02	0.14	0.06	0.1	0.07	0.03	0.07	0.10
TiO₂	0.20	0.17	0.2	0.33	0.56	0.38	0.55	0.50	0.59	0.16	0.17	0.15	0.18	0.07	0.13	0.16	0.11	0.07	0.26	0.05
MnO	–	–	0.01	–	0.03	–	0.02	0.03	0.04	–	–	0.01	–	0.02	–	–	0.05	0.02	0.02	–
WO₃	0.02	0.26	0.64	0.6	–	–	–	0.90	0.94	–	–	0.62	0.63	0.75	0.3	0.5	0.7	–	0.27	0.04
Ta₂O₅	0.05	0.05	–	0.15	0.05	0.03	0.06	0.10	0.15	–	–	–	0.12	0.09	0.09	0.09	0.03	0.1	0.07	0.09
Nb₂O₅	0.02	0.53	0.12	2	0.06	0.09	–	0.63	0.60	–	–	–	–	0.11	0.01	–	–	0.17	0.20	0.09
PbO	0.01	–	0.01	–	0.06	–	–	–	0.01	–	0.02	–	0.01	0.07	0.01	0.05	–	–	–	–
In₂O₃	–	0.02	–	0.03	–	0.01	0.03	0.03	0.04	0.01	0.02	0.04	0.05	0.06	–	–	0.02	–	–	–
UO₂	0.02	0.01	–	0.04	0.04	–	–	–	–	–	0.03	–	–	–	–	–	–	–	0.01	–
Total	99.63	99.40	99.51	99.59	99.60	99.6	99.36	99.48	100.01	99.49	99.82	99.66	99.58	100.29	99.61	99.87	99.63	100.05	99.34	100.01
Sn	0.993	0.986	0.989	0.957	0.979	0.989	0.986	0.972	0.969	0.994	0.995	0.991	0.990	0.988	0.994	0.991	0.991	0.995	0.989	0.996
Fe	0.005	0.003	0.001	0.010	0.019	0.006	0.009	0,005	0.007	0.006	0.004	0.001	–	0.003	0.001	0.002	0.001	0.001	0.001	0.002
Ti	0.003	0.003	0.003	0.006	0.009	0.006	0.009	0.008	0.010	0.003	0.003	0.003	0.003	0.001	0.002	0.003	0.002	0.001	0.004	0.001
Mn	–	–	–	–	0.001	–	–	0.001	0.001	–	–	–	–	–	–	–	0.001	–	–	–
W	–	0.002	0.004	0.003	–	–	–	0.005	0.005	–	–	0.004	0.004	0.004	0.002	0.003	0.004	–	0.002	–
Ta	–	–	–	0.001	–	–	–	0.001	0.001	–	–	–	0.001	0.001	0.001	0.001	–	0.001	–	0.001
Nb	–	0.005	0.001	0.020	0.001	0.001	–	0.006	0.006	–	–	–	–	0.001	–	–	–	0.002	0.002	0.001
Pb	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
In	–	–	–	–	–	–	–	–	–	–	–	–	–	0.001	–	–	–	–	–	–
U	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
Total	1.001	0.999	0.998	0.998	1.010	1.003	1.004	0.999	0.999	1.003	1.002	0.999	0.998	0.999	1.000	0.999	0.999	1.000	0.999	1.000

Wolframite
Spots	1	2	3	4	5	6	7	8	9	10
SnO₂	0.07	0.23	–	–	–	–	–	0.04	0.72	0.02
CaO	0.08	0.06	0.04	0.01	0.02	0.02	0.05	0.05	0.07	0.03
FeO	17.44	14.43	15.47	14.99	15.27	16.91	14.91	14.41	15.31	15.63
TiO₂	0.05	0.04	0.02	0.01	0.05	0	0.02	0	0.05	0.07
MnO	6.30	9.43	9.06	9.21	8.73	7.43	9.18	9.87	8.94	9.21
WO₃	72.81	71.55	74.24	73.21	73.73	73.62	73.76	71.8	71.85	73.67
Ta₂O₅	0.10	0.11	0.06	0.07	0	0.06	0.05	0.17	0.18	0.11
Nb₂O₅	1.13	2.28	0.29	0.78	0.45	0.78	0.57	1.71	1.83	1.02
PbO	0.02	0.02	–	–	–	–	0.02	–	–	–
In₂O₃	0.04	0.06	0.03	–	–	–	0.03	0.01	0.03	0.02
UO₂	0.03	0.05	–	0.07	–	–	–	–	0.06	0.05
Total	98.06	98.26	99.21	98.35	98.25	98.82	98.59	98.06	99.04	99.83
Sn	0.001	0.005	–	–	–	–	–	–	0.014	–
Ca	0.004	0.003	–	–	0.002	0.001	0.003	0.003	0.003	0.002
Fe	0.745	0.613	0.657	0.641	0.654	0.719	0.636	0.615	0.647	0.657
Ti	0.002	0.001	–	–	0.002	–	–	–	0.002	0.003
Mn	0.273	0.406	0.39	0.401	0.378	0.32	0.397	0.427	0.382	0.392
W	0.966	0.942	0.977	0.97	0.979	0.971	0.976	0.95	0.94	0.96
Ta	0.001	0.001	0.01	0.001	–	0.001	0.001	0.002	0.002	0.001
Nb	0.026	0.052	0.007	0.018	0.01	0.018	0.013	0.04	0.042	0.023
Pb	–	–	–	–	–	–	–	–	–	–
In	–	–	–	–	–	–	–	–	–	–
U	–	–	–	–	–	–	–	–	–	–
Total	2.018	2.023	2.041	2.031	2.025	2.03	2.026	2.037	2.032	2.038
Fe³⁺	0.034	0.057	0.023	0.03	0.021	0.023	0.024	0.051	0.06	0.04
Fe²⁺	0.696	0.527	0.622	0.596	0.622	0.675	0.599	0.537	0.557	0.597

Sample	Mineral	δ¹⁸O (‰)	Mineral Pair	Temperature (°C)
G-1202111	Cassiterite	2.7	Cassiterite + quartz	413–484
G-1202112	Cassiterite	2.9	Cassiterite + quartz	413–484
G-1202113	Cassiterite	2.6	Cassiterite + quartz	427–498
G-1202114	Quartz	9.4	Cassiterite + quartz	427–498
G-1202115	Quartz	9.7	Cassiterite + quartz	406–477
G-1202116	Quartz	10.4	Cassiterite + quartz	406–477

Host mineral	Eutectic temperature (°C)	Ice melting temperature (°C)	Total homogenization temperature (°C)	Salinity (%wt. NaCl eq)	Density (g/cm³)
Cassiterite	-22.3 to -36.4	-8.2 to -10.4	255.1–268.9	11.9–14.4	0.87–0.92
Quartz	-21.6 to -26.4	-5.1 to -6.8	107.8–213.9	7.9–10.2	0.92–1.0

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