Lithogeochemistry and geochronology of the subalkaline felsic plutonism that marks the end of the Paleoproterozoic orogeny in the Salvador-Esplanada belt, São Francisco craton (Salvador, state of Bahia, Brazil)

Souza-Oliveira, Jailma Santos de; Peucat, Jean-Jacques; Barbosa, Johildo Salomão Figueiredo; Correa-Gomes, Luiz César; Cruz, Simone Cerqueira Pereira; Leal, Ângela Beatriz Menezes; Paquette, Jean-Louis

doi:10.5327/Z2317-4889201400020004

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Brazilian Journal of Geology

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Articles • Braz. J. Geol. 44 (2) • Apr-Jun 2014 • https://doi.org/10.5327/Z2317-4889201400020004 copy

Lithogeochemistry and geochronology of the subalkaline felsic plutonism that marks the end of the Paleoproterozoic orogeny in the Salvador-Esplanada belt, São Francisco craton (Salvador, state of Bahia, Brazil)

Litogeoquímica e geocronologia do plutonismo félsico subalcalino que marca o final da orogenia Paleoproterozoica no cinturão Salvador-Esplanada, Cráton São Francisco (Salvador, Bahia, Brasil)

Authorship SCIMAGO INSTITUTIONS RANKINGS

Studies conducted over the last decade concerning the rocks that underlie the municipality of Salvador have shown a complex geological history with a great diversity of medium- to high-grade metamorphic lithotypes, deformed in several phases and frequently cut by tabular mafic dykes and irregular granitic bodies. The latter, which were the subject of this study, frequently outcrop along the coastline of Salvador and are classified petrographically as monzo-syenogranites. They are classified as subalkaline and peraluminous according to their geochemical data, and stand out for being enriched in light rare earth elements and having a strong negative Europium (Eu) anomaly. These rocks are produced from anatectic melts or through the interaction of mantle-derived magmas with crustal materials. The negative values of ε_Nd(t) (-6.08) corroborate with the crustal character and in the diagrams of tectonic ambience, they are plotted in the field of post-tectonic granites. The Sm-Nd model age (T_DM) around 2.9 Ga indicates a neoarchean source for these lithotypes, whereas their U-Pb zircon age (LA-ICPMS) of 2,064 ± 36 Ma is similar to the U-Pb (SHRIMP) and Pb-Pb (evaporation) ages for late-tectonic granites of the Itabuna-Curaçá-Salvador belt. Considering the results of recent studies in the area of Salvador, the monzo-syenogranites can be interpreted as late-tectonic intrusions, since they are affected by dextral shear zones correlated with the last stage of deformation registered in the granulites of Salvador.

monzo-syenogranites; petrology; geochronology; Salvador; Bahia; Brazil

	SG-37D	SG-28A	SG-36	SG-39B	SG-86A	SG-08G	SG-88C	SG-23C	SG-24A	SG-08F
SiO₂	69.10	69.40	69.40	70.10	70.10	70.40	71.10	71.70	72.20	73.50
TiO₂	0.61	0.12	0.73	0.73	0.56	0.60	0.55	0.23	0.33	0.23
Al₂O₃	14.50	15.10	14.70	14.00	14.20	13.40	14.10	13.40	13.60	13.10
Fe₂O₃	0.91	2.10	0.92	0.26	1.70	0.81	1.70	2.00	0.96	0.01
FeO	4.20	0.86	3.50	4.60	2.00	3.00	2.27	2.20	2.60	1.70
MnO	0.04	.03	0.04	0.07	0.03	0.03	0.03	0.03	0.04	0.02
MgO	1.00	0.55	1.20	0.81	0.70	0.81	0.64	0.72	0.63	0.56
CaO	1.90	0.70	0.63	1.80	1.10	1.60	1.40	0.61	1.20	0.40
Na₂O	2.20	2.30	2.00	2.60	1.80	2.20	2.30	1.70	2.00	1.60
K₂O	6.10	8.00	6.50	6.00	7.10	6.30	7.10	8.00	6.00	7.80
P₂O₅	0.18	0.06	0.18	0.23	0.16	0.20	0.16	0.03	0.08	0.14
PF		0.18				0.19			0.14	0.59
Total	100.74	99.22	99.80	100.20	99.45	99.35	100.35	100.62	99.64	99.06
V	39	16	41	46	59	37	44	8	19	8
Rb	195	164	206	162	217	213	173	333	284	335
Ba	1.310	3.729	1.419	1.590	1.333	1.468	1.328	943	611	988
Sr	266	636	285	293	386	392	313	186	133	271
Nb	19	<5	11	13	15	58		18	38	25
Zr	820	323	829	859	979	786	853	211	407	417
Y	85	11	45	62	54	39	47	36	60	48
Th	< 5	< 5	< 5	< 5	6.3	29	7.6	113	68	55
La	134.79	22.48	50.95	49.91	66.10	178.90	83.50	221.00	140.27	209.20
Ce	229.31	30.01	115.88	97.81	120.00	324.50	157.00	378.50	273.40	394.30
Nd	50.36	7.78	40.45	39.18	57.60	103.90	68.80	159.00	106.80	131.90
Sm	6.90	1.21	6.77	7.68	9.40	17.57	10.90	18.37	18.33	20.52
Eu	0.18	1.29	0.63	1.05	1.93	2.33	2.23	2.14	1.40	1.83
Gd	3.94	0.98	4.58	6.07	8.54	10.04	8.90	11.50	13.13	11.22
Dy	1.51	0.47	1.46	2.47	5.24	5.31	5.06	5.09	7.07	4.92
Ho	0.29	0.10	0.26	0.01	0.98	1.08	1.02	0.96	1.19	0.88
Er	0.76	0.30	0.52	1.10	2.68	2.28	2.78	2.19	2.03	1.89
Yb	0.31	0.29	0.53	0.76	2.60	1.44	2.40	1.33	1.13	1.11
Lu	0.03	0.06	0.09	0.16	0.38	0.24	0.36	0.14	0.14	0.20

Tectonic Unit	Rock	Magmatic zircon age (inheritage)	Metamorphic age in Ma	Methodology	Reference
Southern Itabuna–Salvador–Curaçá block	Shoshonite	2,075 ± 16 Ma	-	TIMS evap.	Ledru et al. (1994)
	Syenite of Sao Felix	2,098 ± 1	-	TIMS evap.	Rosa et al. (2001)
	Charno-enderbite (TT1)	2,092 ± 6	-	SHRIMP	Silva et al. (2002)
	Enderbite (TT1)	2,109 ± 19	2,081 ± 16	LA-ICPMS	Peucat et al. (2011)
	Tonalite	2,124 ± 10	-	SHRIMP	Silva et al. (2002)
	Enderbite (TT1)	2,131 ± 5	2,069 ± 19	SHRIMP	Silva et al. (2002)
	TT1	ca. 2.18 Ga	2,078 ± 13	LA-ICPMS	Peucat et al. (2011)
	TT1	2,191 ± 10	2,109 ± 17	SHRIMP	Peucat et al.(2011)
	Charno-enderbite	ca. 2.5 Ga	2,086 ± 36	TIMS evap.	Ledru et al. (1994)
	Enderbite of Ipiaú	2,634 ± 14	-	TIMS evap.	Ledru et al. (1994)
	Enderbite (TT2)	2,675 ± 11	2,080 ± 21	LA-ICPMS	Peucat et al. (2011)
	Enderbite (TT2-TT5)	2,719 ± 10	-	SHRIMP	Silva et al. (2002)
	Charno-enderbite	ca. 2.85 Ga	2,078 ± 20	SHRIMP	Silva et al. (2002)
	TT5	ca. 2.7 and 2.9 Ga	2,098 ± 11	SHRIMP	Peucat et al. (2011)
Central Itabuna–Salvador–Curaçá block	Granite (Bravo)	2,063 ± 6		SHRIMP	Barbosa et al. (2008)
	Charnockite (Tanquinho)	2,096 ± 3	-	TIMS evap.	Barbosa et al. (2008)
	Enderbite (Bravo)	2,070 ± 3	-	SHRIMP	Barbosa et al. (2008)
	Charnockite (Jacuípe/C. Nova)	2,126 ± 19	2,082 ± 7	SHRIMP	Silva et al. (1997)
	Leucogabbro (Jacuípe)	2,584 ± 8	2,082 ± 17	SHRIMP	Oliveira et al. (2010)
	Charnockite (Jacuípe)	2,634 ± 19 Ma (3.3 Ga)	2,072 ± 22	SHRIMP	Silva et al. 1997
	Opx tonalite (Jacuípe)	2,695 ± 12 Ma	2,072 ± 15	SHRIMP	Silva et al. 1997
	Enderbite (Riachão de Jacuípe)	ca. 2.2 (ca. 2.8 Ga)	2,028 ± 13	SHRIMP	Silva et al. (2002)
Northern Itabuna–Salvador–Curaçá block	Itiuba syenite	2,084 ± 9		SHRIMP	Oliveira et al. (2004)
	Itiuba syenite	2,095 ± 5		TIMS evap.	Conceição et al. (2003)
	Gabbro-norite (Medrado)	2,085 ± 5		SHRIMP	Oliveira et al. (2004)
	Norite (Caraíba)	2,580 ± 10	2,103 ± 23	SHRIMP	Oliveira et al. (2004)
	Amphibolite (Caraíba)	2,577 ± 110	2,083 ± 4	TIMS	D’el-Rey Silva et al. (2007)
	Tonalite	2,574 ± 6	2,074 ± 14	SHRIMP	Oliveira et al. (2010)
Salvador–Esplanada belt	Orthogneiss (Conde)	2,169 ± 48 (discordant)	-	SHRIMP	Silva et al. (2002)
	Granodiorite (Aporá)	2,954 ± 25	-	SHRIMP	Silva et al. (2002)
	Enderbite (Salvador)	2,561 ± 7	2,089 ± 11	SHRIMP	Silva et al. (1997)
	Granite (Salvador)	2,064 ± 36	-	LA-ICPMS	This work

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