U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting of Gandab volcanic rocks, northeastern Iran

Azam Entezari Harsini; Seyed A Mazaheri; Saeed Saadat; José F Santos

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U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting of Gandab volcanic rocks, northeastern Iran

Azam Entezari Harsini

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| Nov 16, 2017

Volume 44 (2017): Issue 1 (January 2017)

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Page range: 269 - 286

Received: Oct 26, 2016

Accepted: Mar 17, 2017

DOI: https://doi.org/10.1515/geochr-2015-0061

Keywords
U-Pb geochronology, Sr-Nd geochemistry, post-collision, Gandab volcanic rocks, Northeastern Iran

© 2016 A. Entezari Harsini.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Simplified structural map of Iran (compiled from Ruttner and Stöcklin, 1967, Berberian and King, 1981, Alavi, 1991) and location of the Gandab prospecting area in the Northeast of Iran.

Geological map of the Gandab area (Entezari et al., 2016).

Microscopic images of thin sections of volcanic rocks in the studied area (Entezari et al., 2016): (a) Plagioclase and pyroxene phenocrysts in microlitic groundmass in the Hornblende pyroxene olivine basaltic andesite, XPL; (b) Plagioclase and olivine phenocrysts in medium grained groundmass and converting olivine to chlorite and iddingsite in the Olivine hornblende basaltic andesite; (c) K-feldspar, hornblendel, magnetite phenocrysts, and glomeroporphyritic texture in the Pyroxene hornbelend trachy andesite; (d) Poikilitic texture in the Hornbelend pyroxene trachy andesite; (e) Plagioclase and opacity hornblende phenocrysts in the Hornblende andesite; (f) Phenocryst of plagioclase in a matrix of fine grain to intersertal and amygdals of carbonate in the Andesite; (g) Plagioclase and hornblende phenocrysts and alteration of hornblende to carbonate in the Hornblende trachy andesite; (h) K-feldspar phenocryst and trachytic texture in the Trachy andesite; (i) Plagioclase, clinopyroxene, and magnetite phenocrysts in the Pyroxene andesite.

(a) Na2O + K2O vs. SiO2 diagram (Middlemost, 1994); (b) diagram for discriminate between subalkaline and alkaline fields (Irvine and Baragar,1971).

A/NK (molar) vs. A/CNK diagram of Shand (1943). The symbols are the same as in Fig. 4.

Selected major and trace elements vs. SiO2 contents for the Gandab volcanic rocks.

(a) primitive-mantle normalized diagrams (McDonough and Sun, 1995); (b) REE chondrite normalized diagrams (Boynton, 1984). The symbols are the same as in Fig. 6.

Cathodoluminescence images of analysed zircon grains from GCh-119 and GCh-171 samples, for the investigated volcanic rocks from the Gandab area, Iran. The red circles show the analyzed spots.

Concordia diagrams of 207Pb/207Pb vs. 238U/206Pb for calculating the age of zircons from Gandab volcanic rocks (Age is reported in Ma, GCh-119 = 5.47± 0.22, GCh-171 = 2.44± 0.79).

(a) TiO2 us. Al2O3 diagram, (Muller et al., 1992); (b) Nb*50-Zr*/3-Ce/P2O5 ternary diagram (Muller et al., 1992).

Diagrams showing fractional crystallization (FC) for Gandab volcanic rocks. (a) Th vs. SiO2 (Whalen et al, 1987); (b) Eu/Eu* vs. SiO2 (Irber, 1999); (c) Ba/Sr vs. SiO2 (Lopez-Moro et al., 2012); (d) Th/Yb vs. SiO2 (Taylor and McLennan, 1985); (e) La/Nb vs. SiO2 (Taylor and McLennan, 1985).

Plot of initial (87Sr/86Sr)i vs. εNd ratios (Entezari et al., 2016).

Geographic location, name, and symbol of the analyzed samples in the Gandab volcanic rocks.

Sample	Longitude (E)	Latitude (N)	Rock type
GCh-171	58°44′25″	35°48′59″	Pyroxene andesite

GCh-92	58°44′27″	35°48′39″	Pyroxene andesite

GCh-119	58°43′39″	35°47′37″	Hornblende pyroxene olivine trachy andesite basalt

GCh-154	58°41′42″	35°50′53″	Hornblende pyroxene olivine trachy andesite basalt

GCh-131	58°42′08″	35°49′23″	Olivine hornblende trachy andesite basalt

GCh-179	58°41′24″	35°49′24″	Olivine hornblende trachy andesite basalt

GCh-60	58°42′49″	35°49′55″	Pyroxene hornblende trachy andesite

GCh-17	58°43′12″	35°49′49″	Pyroxene hornblende trachy andesite

GCh-140	58°42′34″	35°50′50″	Hornblende andesite

GCh-35	58°42′58″	35°50′02″	Hornblende andesite

GCh-160	58°41′38″	35°50′03″	Hornblende trachy andesite

GCh-183	58°43′12″	35°49′33″	Hornblende trachy andesite

GCh-16	58°43′27″	35°49′49″	Trachy andesite

GCh-71	58°43′14″	35°49′31″	Trachy andesite

GCh-40	58°43′09″	35°50′03″	Trachy andesite

GCh-31	58°43′02″	35°50′09″	Trachy andesite

GCh-57	58°42′44″	35°50′18″	Hornblende pyroxene trachy andesite

GCh-86	58°43′37″	35°49′14″	Hornblende pyroxene trachy andesite

GCh-27	58°43′16″	35°50′00″	Andesite

GCH-49	58°42′53″	35°50′14″	Andesite

Major element (in wt% by XRF) and trace element (in ppm by ICP-MS) compositions of samples from Gandab volcanic rocks (Entezari et al., 2016).

Sample	GCH-171	GCH-92	GCH-119	GCH-153	GCH-131	GCH-179	GCH-60	GCH-17	GCH-140	GCH-35	GCH-160	GCH-183	GCH-16	GCH-71	GCH-57	GCH-86	GCH-40	GCH-31	GCH-27	GCH-49
Sample	SiO₂	62.58	61.54	54.01	54.39	55.01	54.56	57.86	57.12	57.71	57.35	58.01	57.25	57.86	57.42	60.88	59.35	58.36	58.12	55.87	55.12

Al₂O₃	17.69	17.59	15.91	16.05	15.86	15.62	17.99	18.03	18.24	18.35	18.02	18.42	17.08	16.89	17.52	18.13	17.63	17.51	15.24	15.35

FeO	3.50	3.82	8.21	7.92	7.53	7.79	4.80	5.35	5.19	5.12	5.23	5.17	5.21	5.34	3.73	4.22	4.85	5.01	4.26	4.78

CaO	5.27	5.92	6.87	6.52	7.02	7.32	4.26	4.62	5.17	5.21	5.24	5.27	2.86	3.42	1.68	1.89	3.01	2.97	4.98	5.02

Na2O	4.48	4.53	3.56	3.45	3.29	3.35	4.34	4.12	3.94	4.25	3.59	3.75	4.75	4.35	4.26	4.12	3.87	3.67	2.98	2.87

K₂O	3.02	2.95	2.99	3.25	3.38	3.57	5.49	5.15	4.02	3.98	4.08	3.92	6.89	6.72	7.34	6.95	7.02	6.99	7.41	7.25

MgO	0.27	0.42	5.24	5.10	4.52	4.98	1.78	1.98	2.35	2.37	2.34	2.52	1.69	1.91	1.48	1.79	1.49	1.78	0.98	1.35

TiO₂	1.429	1.354	0.891	0.854	0.840	0.915	0.968	1.071	0.869	0.864	0.867	0.862	1.011	1.009	0.914	1.050	0.918	0.899	1.154	1.034

MnO	0.080	0.069	0.112	0.131	0.098	0.082	0.069	0.059	0.045	0.048	0.042	0.046	0.124	0.105	0.040	0.051	0.078	0.087	0.063	0.087

P₂O₅	0.336	0.392	0.341	0.313	0.362	0.333	0.454	0.521	0.418	0.455	0.418	0.428	0.732	0.792	0.323	0.355	0.513	0.532	0.468	0.423

L.O.I	1.04	1.15	1.62	1.78	1.87	1.55	1.73	1.76	1.66	1.67	1.85	1.87	1.43	1.66	1.51	1.72	2.03	2.10	4.40	4.65

Total	99.72	99.86	99.82	99.83	99.80	99.71	99.77	99.81	99.64	99.52	99.71	99.53	99.71	99.72	99.74	99.71	99.87	99.76	99.51	99.76

Cu	0.02	0.02	0.01	0.01	0.01	0.01	0.02	0.02	0.01	0.01	0.01	0.01	0.05	0.07	0.05	0.06	0.10	0.06	1.69	1.81

S	0.009	0.008	0.054	0.057	0.009	0.008	0.012	0.013	0.012	0.015	0.008	0.009	0.018	0.035	0.011	0.019	0.008	0.009	0.017	0.017

Ba	287	294	383	367	376	381	515	552	482	475	451	453	551	525	485	435	570	552	497	505

Be	2	2	1	2	1	1	2	2	1	2	2	2	1	1	2	1	2	2	4	3

Co	4.3	5.6	27.4	28.2	28.7	29.1	9.8	10.1	12.1	12.8	12.7	13.1	8.0	9.1	4.8	5.2	7.4	6.9	6.1	5.8

Cs	1.1	1.5	1.9	2.4	2.2	2.6	2.9	3.1	1.9	1.5	1.3	1.2	3.3	2.8	3.6	3.2	3.3	2.9	3.0	2.8

Ga	19.6	18.3	16.1	15.9	15.6	16.2	15.1	15.6	18.2	18.8	17.2	16.8	15.5	16.1	16.0	15.5	15.0	14.3	13.7	14.1

Hf	7.5	7.4	2.9	2.8	2.9	2.9	3.7	3.6	3.3	3.5	3.5	3.4	3.6	3.7	4.1	4.2	3.7	3.8	3.4	3.3

Nb	27.9	26.2	9.9	10.4	11.5	10.8	15.2	15.8	14.5	14.1	14.3	14.6	16.5	16.2	19.2	18.8	15.8	15.6	15.3	15.7

Rb	68.0	73.1	70.8	72.4	74.4	79.1	135.4	142.1	97.0	110.2	96.1	82.2	160.4	155.2	182.2	173.1	158.7	148.9	144.9	145.5

Sn	3	2	2	1	1	2	1	1	1	2	1	1	1	1	1	2	2	1	1	1

Sr	453.9	438.2	614.8	580.3	559.8	592.2	608.6	595.1	726.7	717.3	728.7	731.2	504.7	491.2	239.1	251.2	454.3	432.1	347.2	371.1

Ta	1.8	1.6	0.6	0.7	0.7	0.8	0.9	0.8	0.8	0.9	1.0	0.8	1.1	1.0	1.2	1.1	0.9	1.0	1.0	0.9

Th	9.1	9.5	3.7	4.3	4.1	4.8	6.1	6.2	4.9	5.1	5.0	4.8	7.2	6.9	7.8	7.4	6.7	7.1	6.2	6.3

U	2.7	2.5	1.1	1.3	1.1	1.2	1.6	1.4	1.4	1.6	1.5	1.4	2.3	2.5	1.1	1.1	2.3	2.4	2.4	2.1

V	112	120	259	262	252	243	298	310	265	256	269	285	395	375	223	259	361	345	279	242

W	1.4	1.6	1.5	1.9	2.9	3.1	1.3	1.7	1.5	1.8	1.7	1.5	1.4	1.6	2.0	1.8	1.8	1.6	3.3	2.7

Zr	306.1	297.3	108.6	121.5	119.8	109.1	157.9	149.1	142.0	138.5	140.9	135.2	167.5	159.5	193.5	185.1	160.0	163.6	148.0	152.1

Y	30.8	31.2	19.3	18.9	19.4	18.8	16.9	17.1	17.1	16.8	17.9	17.2	18.6	18.3	18.0	18.5	17.4	17.1	16.7	17.2

La	36.3	35.2	15.4	15.8	17.1	16.8	22.6	21.7	21.3	21.5	20.9	21.2	24.7	24.1	24.1	23.2	24.1	23.8	23.3	23.9

Ce	76.9	75.2	32.0	33.2	36.0	35.2	42.6	43.2	43.6	41.9	41.6	42.3	48.3	47.9	45.6	44.9	45.7	45.2	45.8	44.9

Pr	8.96	8.52	4.35	4.71	4.62	4.44	5.25	5.37	5.24	5.01	5.14	4.93	5.71	5.54	5.36	5.59	5.72	5.45	5.51	4.89

Nd	35.8	36.4	17.7	18.1	18.6	18.4	19.9	20.2	19.2	18.8	20.2	20.4	22.3	22.6	20.6	19.9	21.4	22.3	22.3	22.5

Sm	7.14	7.01	4.12	3.93	3.88	4.07	3.75	3.83	4.11	3.95	3.99	4.05	4.39	4.09	3.71	3.91	3.86	4.01	4.00	3.89

Eu	1.69	1.58	1.22	1.17	1.15	1.11	1.05	0.98	1.15	1.19	1.15	1.13	1.11	1.15	0.91	1.08	1.18	1.21	1.09	1.12

Gd	6.69	6.35	4.12	3.93	4.22	4.17	3.53	3.61	3.73	3.68	3.80	3.75	3.67	3.86	3.33	3.52	3.49	3.62	3.57	3.49

Tb	1.04	1.11	0.61	0.56	0.65	0.61	0.57	0.59	0.58	0.58	0.59	0.60	0.60	0.63	0.51	0.56	0.58	0.57	0.54	0.55

Dy	5.64	5.23	3.44	3.61	3.74	3.54	2.91	3.11	3.36	3.21	3.23	3.39	3.51	3.33	2.97	3.08	3.32	3.45	3.01	2.96

Ho	1.10	1.05	0.74	0.72	0.75	0.73	0.60	0.62	0.73	0.68	0.69	0.72	0.65	0.63	0.65	0.69	0.63	0.66	0.61	0.67

Er	3.20	3.11	1.81	1.87	1.99	1.92	1.78	1.81	1.90	1.94	1.92	1.95	1.88	1.83	1.90	1.94	2.06	1.98	1.79	1.85

Tm	0.44	0.41	0.30	0.29	0.30	0.30	0.27	0.28	0.27	0.28	0.29	0.29	0.29	0.29	0.29	0.28	0.28	0.27	0.30	0.30

Yb	2.91	2.76	1.95	1.91	1.92	1.89	1.70	1.72	1.84	1.86	1.73	1.87	1.87	1.92	1.91	1.88	1.84	1.87	1.71	1.73

Lu	0.46	0.48	0.31	0.30	0.31	0.31	0.27	0.28	0.29	0.27	0.28	0.29	0.32	0.30	0.31	0.30	0.31	0.31	0.28	0.29

Nb/Th	3.07	2.757	2.68	2.42	2.80	2.25	2.49	2.54	2.96	2.76	2.86	3.04	2.29	2.35	2.46	2.54	2.36	2.2	2.47	2.49

Ba/Sr	0.63	0.67	0.62	0.63	0.67	0.64	0.85	0.93	0.66	0.66	0.62	0.62	1.09	1.06	2.02	1.73	1.25	1.27	1.43	1.36

Th/Yb	3.13	3.44	1.90	2.25	2.14	2.54	3.59	3.6	2.66	2.74	2.89	2.57	3.85	3.59	4.08	3.94	3.64	3.8	3.63	3.64

La/Nb	1.30	1.34	1.56	1.52	1.49	1.56	1.49	1.37	1.47	1.52	1.46	1.45	1.50	1.49	1.25	1.23	1.53	1.53	1.52	1.52

(La/Sm)_N	3.20	3.16	2.35	2.53	2.77	2.60	3.79	3.56	3.26	3.42	3.29	3.29	3.54	3.71	4.09	3.73	3.93	3.73	3.66	3.86

Eu/Eu*	0.75	0.72	0.91	0.91	0.87	0.82	0.88	0.81	0.90	0.95	0.90	0.89	0.85	0.88	0.79	0.89	0.98	0.97	0.88	0.93

(Gd/Yb)_N	1.85	1.86	1.70	1.66	1.77	1.78	1.68	1.69	1.64	1.60	1.77	1.62	1.58	1.62	1.41	1.51	1.53	1.56	1.64	1.63

Rb–Sr and Sm–Nd isotopic data of the Gandab volcanic rocks (Entezari et al., 2016). 2σ shows the precision of measurement and calculations (standard error).

Sample	Latitude (N)	Longitude (E)	Rb (ppm)	Sr (ppm)	⁸⁷Rb/⁸⁶Sr	⁸⁷Sr/⁸⁶Sr	Uncertainty (2σa)	Sm (ppm)	Nd (ppm)	¹⁴⁷Sm/¹⁴⁴Nd	¹⁴³Nd/¹⁴⁴Nd	Uncertainty (2σ)	εNd
Sample	Latitude (N)	Longitude (E)	GCh-16	35°49′49″	⁸⁷Rb/⁸⁶Sr	⁸⁷Sr/⁸⁶Sr	58°43′14″	106	505	¹⁴⁷Sm/¹⁴⁴Nd	¹⁴³Nd/¹⁴⁴Nd	0.609	εNd	0.705047	0.000020	4.39	22.3	0.119	0.512833	0.000017	+3.8
GCh-57	35°50′18″	58°42′44″	182	239	2.205	0.705931	0.000020	3.71	20.6	0.109	0.512807	0.000015	+3.3
GCh-171	35°48′59″	58°44′25″	68.0	454	0.433	0.704082	0.000021	7.14	35.8	0.121	0.512893	0.000015	+5.0
GCh-119	35°47′37″	58°43′39″	70.8	615	0.333	0.704614	0.000016	4.12	17.7	0.141	0.512843	0.000017	+4.0

Zircon U–Pb isotopic data for the Gandab volcanic rocks.

Sample No.	U²³⁸ (ppm)	Th²³²/U²³⁸	²⁰⁷Pb/²⁰⁶Pb	²³⁸U/²⁰⁶pb	²⁰⁶Pb/²³⁸U	Age (Ma)	± (Ma)
GCh-119-1	343	0.730	0.0424	1234.01	0.0008	5.2	0.1

GCh-119-2	363	0.889	0.0514	1185.23	0.0008	5.4	0.2

GCh-119-3	347	0.579	0.0622	1197.66	0.0008	5.3	0.2

GCh-119-4	348	0.621	0.1039	1247.21	0.0008	4.9	0.1

GCh-119-5	389	1.113	0.0750	1173.23	0.0008	5.3	0.2

GCh-119-6	401	1.314	0.0922	1125.15	0.0009	5.5	0.1

GCh-119-7	456	0.967	0.0561	1192.12	0.0008	5.3	0.1

GCh-119-8	372	0.871	0.0748	1134.21	0.0009	5.5	0.2

GCh-119-9	339	0.690	0.0621	1179.10	0.0008	5.3	0.2

GCh-119-10	375	0.821	0.0940	1211.12	0.0008	5.1	0.1

GCh-119-11	332	1.101	0.1175	1045.23	0.0009	5.8	0.2

GCh-119-12	431	0.821	0.0920	1119.12	0.0009	5.6	0.2

GCh-119-13	369	1.451	0.0831	1131.57	0.0009	5.5	0.2

GCh-119-14	367	0.781	0.1751	980.56	0.0010	6.1	0.1

GCh-119-15	383	0.983	0.1669	960.13	0.0010	6.3	0.2

GChH-171-1	973	0.865	0.0798	2886.14	0.0003	2.1	0.1

GCh-171-2	613	0.550	0.0533	2819.62	0.0004	2.3	0.1

GCh-171-3	797	0.943	0.0904	2690.01	0.0004	2.4	0.1

GCh-171-4	765	0.595	0.0983	2911.14	0.0003	2.1	0.1

GCh-171-5	821	1.123	0.1289	2248.87	0.0004	2.7	0.1

GCh-171-6	678	0.871	0.1634	2321.22	0.0004	2.5	0.1

GCh-171-7	587	0.781	0.0879	2430.76	0.0004	2.5	0.1

GCh-171-8	801	1.121	0.0973	2869.36	0.0003	2.1	0.1

GCh-171-9	745	0.891	0.0611	2856.00	0.0004	2.2	0.1

GCh-171-10	956	1.153	0.1298	2678.87	0.0004	2.4	0.1

GCh-171-11	1005	1.151	0.0518	2488.76	0.0004	2.7	0.1

GCh-171-12	567	0.701	0.0741	2780.20	0.0003	2.3	0.1

GCh-171-13	710	1.151	0.0588	2130.45	0.0005	3.1	0.2

GCh-171-14	834	0.871	0.0741	2414.67	0.0004	2.7	0.1

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U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting of Gandab volcanic rocks, northeastern Iran

Published Online: Nov 16, 2017

Page range: 269 - 286

Received: Oct 26, 2016

Accepted: Mar 17, 2017

DOI: https://doi.org/10.1515/geochr-2015-0061

Keywords
U-Pb geochronology, Sr-Nd geochemistry, post-collision, Gandab volcanic rocks, Northeastern Iran

© 2016 A. Entezari Harsini.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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Geographic location, name, and symbol of the analyzed samples in the Gandab volcanic rocks.

Major element (in wt% by XRF) and trace element (in ppm by ICP-MS) compositions of samples from Gandab volcanic rocks (Entezari et al., 2016).

Rb–Sr and Sm–Nd isotopic data of the Gandab volcanic rocks (Entezari et al., 2016). 2σ shows the precision of measurement and calculations (standard error).

Zircon U–Pb isotopic data for the Gandab volcanic rocks.

U-Pb geochronology, Sr-Nd geochemistry, petrogenesis and tectonic setting of Gandab volcanic rocks, northeastern Iran

Published Online: Nov 16, 2017

Page range: 269 - 286

Received: Oct 26, 2016

Accepted: Mar 17, 2017

DOI: https://doi.org/10.1515/geochr-2015-0061

KeywordsU-Pb geochronology, Sr-Nd geochemistry, post-collision, Gandab volcanic rocks, Northeastern Iran

© 2016 A. Entezari Harsini.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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Geographic location, name, and symbol of the analyzed samples in the Gandab volcanic rocks.

Major element (in wt% by XRF) and trace element (in ppm by ICP-MS) compositions of samples from Gandab volcanic rocks (Entezari et al., 2016).

Rb–Sr and Sm–Nd isotopic data of the Gandab volcanic rocks (Entezari et al., 2016). 2σ shows the precision of measurement and calculations (standard error).

Zircon U–Pb isotopic data for the Gandab volcanic rocks.

Keywords
U-Pb geochronology, Sr-Nd geochemistry, post-collision, Gandab volcanic rocks, Northeastern Iran