Petrogenesis of the Riacho do Icó Stock: evidence for Neoproterozoic slab melting during accretion tectonics in the Borborema Province?

Santos, Lauro Cézar Montefalco de Lira; Lima, Haroldo Monteiro; Lages, Geysson de Almeida; Caxito, Fabrício de Andrade; Araújo Neto, José Ferreira de; Guimarães, Ignez de Pinho

doi:10.1590/2317-4889202020190127

Lauro Cézar Montefalco de Lira Santos ^**Corresponding author.

Universidade Federal de Pernambuco - Recife (PE), Brazil. E-mails: lauromontefalco@gmail.com, araujoneto.geo@gmail.com, ignez@ufpe.br

https://orcid.org/0000-0001-6098-1873

Haroldo Monteiro Lima

Universidade Federal do Ceará - Fortaleza (CE), Brazil. E-mail: harolgogeologo@gmail.com

https://orcid.org/0000-0002-9744-7997

Geysson de Almeida Lages

Serviço Geológico do Brasil - Recife (PE), Brazil. E-mail: geysson.lages@cprm.gov.br

https://orcid.org/0000-0001-7041-4944

Fabrício de Andrade Caxito

Universidade Federal de Minas Gerais - Belo Horizonte (MG), Brazil. E-mail: facaxito@yahoo.com.br

https://orcid.org/0000-0002-0335-3667

José Ferreira de Araújo Neto

Universidade Federal de Pernambuco - Recife (PE), Brazil. E-mails: lauromontefalco@gmail.com, araujoneto.geo@gmail.com, ignez@ufpe.br

https://orcid.org/0000-0002-1780-9469

Ignez de Pinho Guimarães

Universidade Federal de Pernambuco - Recife (PE), Brazil. E-mails: lauromontefalco@gmail.com, araujoneto.geo@gmail.com, ignez@ufpe.br

Universidade Federal do Ceará - Fortaleza (CE), Brazil. E-mail: harolgogeologo@gmail.com

https://orcid.org/0000-0002-5037-3820

*Corresponding author.

L. C. M. L. S. wrote the first draft of the manuscript and worked on it until its final shape as well as on the conducting of major interpretations. H. M. L. worked during field trips, sample collecting and helped with petrographic description and geochemical interpretations. G. A. L. worked on the main text and provided advisorship regarding the geology of the Alto Pajeú Terrane as well as on the granites of the Borborema Province. F. A. C. helped with the regional geology aspects, including bibliographic updating, text reviewing and geochronological data interpretation. J. F. A. N. worked on tables, text editing and conducted all steps of sample preparation for geochemistry. I. P. G. obtained the geochronological data and strongly contributed to the text and interpretation reviewing.

Competing interests: The authors have no competing interests to declare.

Figure 11. Plots of samples from the Riacho do Icó Suite: (A) Sr/Y diagram with fields of adakites and “normal” calc-alkaline rocks from Defant & Drummond (1990Defant M.J., Drummond M.S. 1990. Derivation of some modern arc magmas by melting of young subducted lithosphere. Nature, 347:662-665. https://doi.org/10.1038/347662a0
https://doi.org/https://doi.org/10.1038/... ). (B) MgO vs. SiO₂ diagram discriminating high-silica groups (has) and low-silica (LSA) from **Martin et al. (2005Martin H., Smithies R.H., Rapp R., Moyen J.F., Champion D. 2005. An overview of adakite, TTG and sanukitoid: relationships and some implications for crustal evolution. Lithos, 79(1-2):1-24. https://doi.org/10.1016/j.lithos.2004.04.048
https://doi.org/https://doi.org/10.1016/... ). (C) MgO. vs. SiO₂ diagram discriminating sources for adakitic magmas with fields/data compiled from Rapp et al. (1999Rapp R.P., Shimizu N., Norman M.D., Applegate G.S. 1999. Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa. Chemical Geology, 160(4):335-356. https://doi.org/10.1016/S0009-2541(99)00106-0
https://doi.org/https://doi.org/10.1016/... , 2002Rapp R.P., Xiao L., Shimuzu N. 2002. Experimental constraints on the origin of potassium-rich adakite in east China. Acta Petrologica Sinica, 18(3):293-302. ), Sen & Dunn (1994Sen C., Dunn T. 1994. Dehydration melting of a basaltic composition amphibolite at 1.5 GPa and 2.0 GPa: implication for the origin of adakites. Contributions to Mineralogy and Petrology, 117:394-409. https://doi.org/10.1007/BF00307273
https://doi.org/https://doi.org/10.1007/... ), Rapp & Watson (1995Rapp R.P., Watson E.B. 1995. Dehydration melting of metabasalt at 8-32 kbar, implications for continental growth and crust-mantle recycling. Journal of Petrology, 36(4):891-931. https://doi.org/10.1093/petrology/36.4.891
https://doi.org/https://doi.org/10.1093/... ), Skjerlie & Patiño Douce (2002Skjerlie K.P., Patiño Douce A.E. 2002. The fluid-absent partial melting of a zoisite-bearing quartz eclogite from 1.0 to 3.2 Gpa: implications for melting in thickened continental crust and for subduction-zone processes. Journal of Petrology, 43(2):291-314. https://doi.org/10.1093/petrology/43.2.291
https://doi.org/https://doi.org/10.1093/... ), and Wang et al. (2006**Wang Q., Xu J.-F., Jian P., Bao Z.-W., Zhao Z.-H., Li C.-F., Xiong X.-L., Ma J.-L. 2006. Petrogenesis of Adakitic Porphyries in an Extensional Tectonic Setting, Dexing, South China: Implications for the Genesis of Porphyry Copper Mineralization. Journal of Petrology, 47(1):119-144. https://doi.org/10.1093/petrology/egi070
https://doi.org/https://doi.org/10.1093/... ).

Grain Spot	% ²⁰⁶ Pb _c	Ppm U	Ppm Th	²³² Th /²³⁸U	Ppm ²⁰⁶ Pb*	(1) ²⁰⁶ Pb /²³⁸U Age	(1) ²⁰⁷ Pb /²⁰⁶Pb Age	% Discordant	(1) ²⁰⁷ Pb* /²⁰⁶Pb*	±%	(1) ²⁰⁷ Pb* /²³⁵U	±%	(1) ²⁰⁶ Pb* /²³⁸U	±%	errcorr
1.3	0.03	540	29	0.06	46.1	610.6	616	1	0.06034	0.7	0.827	1.4	0.0994	1.2	.872
4.2	0.00	329	314	0.99	28.2	613.4	631	3	0.06078	1.1	0.837	1.6	0.0998	1.1	.695
5.2	0.77	621	482	0.80	52.6	600.8	621	3	0.0605	2.5	0.814	2.7	0.0977	1	.386
6.2	0.26	154	86	0.58	17.9	817.5	943	13	0.07049	1.4	1.314	1.8	0.1352	1.2	.648
6.3	0.00	554	19	0.04	54.2	694.2	695	0	0.06262	0.7	0.982	1.3	0.1137	1.1	.836
7.2	0.51	538	14	0.03	43.6	577.5	598	3	0.05984	1.4	0.773	1.8	0.09372	1	.597
8.2	2.61	771	1,045	1.40	64	579.6	591	2	0.0596	4.7	0.774	4.9	0.0941	1.1	.220
13.2	--	190	103	0.56	23.1	854	996	14	0.07237	1.1	1.414	1.6	0.1417	1.1	.726
13.3	2.73	1,049	44	0.04	83.1	553.7	564	2	0.0589	4.8	0.729	5	0.08969	1.1	.214
14.2	0.13	387	35	0.09	32.5	600.5	630	5	0.06073	0.94	0.817	1.4	0.0976	1.1	.749
15.2	0.19	337	34	0.10	29.1	615.8	631	2	0.06078	1.1	0.84	1.6	0.1002	1.1	.686
17.1	--	123	47	0.40	17.4	983	991	1	0.07218	1.1	1.639	1.7	0.1647	1.2	.725
18.1	0.00	49	1	0.01	4.05	586.6	598	2	0.0598	2.3	0.786	2.8	0.0953	1.6	.557
19.1	0.00	246	10	0.04	21.1	614.7	618	1	0.06041	1	0.833	1.5	0.1	1.1	.731
19.2	0.21	617	27	0.05	51.8	600.2	608	1	0.06011	1.2	0.809	1.6	0.0976	1	.654
20.1	0.27	858	42	0.05	72.9	606.6	607	0	0.06008	0.92	0.817	1.4	0.0987	1	.744

Sample	Major elements (wt. %)
Sample	Rl01	Rl02	Rl03	Rl04	Rl05	Rl06	Rl07	Rl08	Rl09	Rl10	Rl11	ES15
SiO₂	71.9	65.86	65.7	68.8	68.2	71.2	67.26	69.93	70.3	67.25	71.3	71.3
TiO₂	0.32	0.61	0.54	0.52	0.34	0.41	0.47	0.38	0.45	0.47	0.41	0.33
Al₂O₃	13.8	14.85	15.9	14.7	14.86	15.1	14.68	14.49	15.3	14.94	14.7	14.1
Fe₂O₃(total)	2.10	3.45	3.17	2.90	1.98	2.50	2.77	2.19	2.68	2.92	2.58	2.17
Cr₂O₃	0.03	0.04	0.03	0.02	0.02	0.03	0.04	0.03	0.03	0.03	0.02	0.02
MnO	0.01	0.03	0.03	0.02	0.02	0.02	0.03	0.03	0.02	0.03	0.02	0.01
MgO	0.69	1.16	1.07	1.14	0.62	0.90	0.84	0.67	0.96	0.92	0.90	0.76
CaO	1.86	2.56	2.55	2.50	2.02	2.51	2.31	1.91	2.44	2.36	2.31	2.03
Na₂O	4.09	4.74	4.72	4.32	4.29	4.37	4.36	4.35	4.53	4.58	4.48	4.29
K₂O	3.91	3.93	3.75	3.96	4.38	4.00	4.13	3.91	4.38	3.97	3.91	4.05
P₂O₅	0.16	0.17	0.15	0.17	0.1	0.16	0.15	0.1	0.16	0.15	0.17	0.12
LOI	0.64	1.54	1.24	0.61	1.07	0.68	1.42	0.62	0.75	0.70	0.73	0.53
Total	99.5	98.9	98.85	99.7	99.0	101.8	98.5	98.6	102.0	98.3	101.5	99.7
Trace elements (ppm)
V	24	39	63	45	16	38	42	43	37	41	48	36
Co	6.2	9.5	7.4	9	5.2	7.7	8.1	6	8.7	8.2	7.9	6.1
Ni	12	17	14	16	10	13	15	13	14	15	17	19
Cu	5	11	9	10	< 5*	12	10	< 5*	14	12	10	< 5*
Tl	3.1	2	1.2	1.1	0.9	0.7	0.7	0.7	0.6	< 0.5*	< 0.5*	< 0.5*
Zn	96	95	95	103	79	96	86	84	87	89	94	103
Ga	26.1	26.3	23.4	28.5	28.1	24.5	24	25.6	25.7	25.1	25.5	27.3
Rb	166.5	153	126.5	162.7	172.1	118.8	121.4	157.7	127.5	117.4	120.3	170
Sn	2.4	2.5	2	2.9	1.7	1.8	1.6	1.4	1.8	1.7	1.8	2.1
Sr	421	604	677	626	487	648	650	435	649	630	631	429
W	11.6	11.7	8	6.5	8.3	9.6	14.5	10.3	11.8	10.2	9.8	8.6
Zr	157	198	188	181	136	156	158	154	173	149	147	152
Nb	10.6	13.79	7.99	10.4	6.67	7.59	8.57	6.59	8.24	7.94	7.51	6.83
Cs	6.82	6.99	5.80	7.59	5.45	3.49	3.39	3.59	3.59	6.31	6.46	2.34
Ba	749	1184	1218	1292	873	1257	1320	727	1248	1086	1127	741
La	32.5	29.5	22.5	42.1	22.1	18.5	20.4	51	33.1	31.6	31.4	46.1
Ce	56	70	50.3	77.5	40.5	40.9	42.3	55.1	61.9	57.8	55.5	55.3
Pr	7.3	7.18	5.71	9.78	4.79	4.41	4.71	9.46	7.26	6.71	6.5	8.26
Nd	25.9	27.2	21.7	36.3	18.1	16.7	18.7	34.8	27.7	25.2	24.3	30.2
Sm	4.2	5.1	4.1	6.5	3.4	3.7	3.9	5.2	4.8	4.3	4.4	4.8
Eu	0.89	1.31	1.01	1.48	0.79	0.94	1.02	1.11	1.16	1.07	1.07	1.01
Gd	2.45	3.88	2.91	4.58	2.46	2.84	2.87	3.29	3.36	3.24	3.2	3.11
Tb	0.26	0.47	0.36	0.52	0.24	0.34	0.35	0.31	0.41	0.36	0.36	0.3
Dy	1.08	2.32	1.61	2.34	0.95	1.51	1.53	1.11	1.74	1.57	1.42	1.12
Ho	0.17	0.37	0.25	0.35	0.15	0.21	0.24	0.17	0.25	0.26	0.24	0.16
Er	0.45	0.97	0.64	0.87	0.33	0.58	0.63	0.40	0.63	0.65	0.57	0.38
Tm	0.07	0.13	0.08	0.11	< 0.05*	0.08	0.07	< 0.05*	0.08	0.08	0.07	< 0.05*
Yb	0.4	0.8	0.5	0.7	0.3	0.4	0.5	0.3	0.5	0.5	0.4	0.3
Lu	0.05	0.11	0.06	0.10	0.05	0.06	0.07	0.05	0.05	0.07	0.07	0.05
Y	4.2	9.27	6.42	9.36	3.8	6.14	6.43	4.79	7.08	6.72	6.26	4.54
Hf	5.55	6.06	4.33	5.69	4.75	4.59	4.62	4.88	5.36	4.71	4.6	5.1
Ta	3.03	2.36	1.66	1.53	0.98	0.97	0.97	0.74	0.95	0.8	0.79	0.51
Th	9.3	11.1	7.7	10.5	7.2	7.8	8.1	7.9	9.4	8.4	7.6	7.3
U	2.28	2.63	2.04	2.62	2.02	1.49	1.61	2.32	1.78	1.65	1.61	2.19
SREE	131.72	149.34	111.73	183.23	94.11	91.17	97.29	162.25	142.96	133.41	129.48	151.04
Eu_N /Eu*	0.85	0.91	0.90	0.83	0.84	0.89	0.94	0.82	0.89	0.88	0.88	0.80
(La/Yb)_N	54.1	24.5	30.0	40.1	49.1	30.8	27.2	113.3	44.1	42.1	52.3	102.4
(La/Sm)_N	4.76	3.56	3.38	3.98	4.00	3.08	3.22	6.03	4.24	4.52	4.39	5.91
(Gd/Yb)_N	4.8	3.86	4.64	5.22	6.55	5.65	4.58	8.76	5.36	5.17	6.37	8.29

[1] *Corresponding author.

Brasil

Brasil

Petrogenesis of the Riacho do Icó Stock: evidence for Neoproterozoic slab melting during accretion tectonics in the Borborema Province?

Abstract