Strongly peraluminous leucogranite (Ebrahim-Attar granite) as evidence for extensional tectonic regime in the Cretaceous, Sanandaj Sirjan zone, northwest Iran

Azizi, Hossein; Mohammadi, Keivan; Asahara, Yoshihiro; Tsuboi, Motohiro; Daneshvar, Narges; Mehrabi, Behzad

doi:10.1016/j.chemer.2016.08.006

Cited by 30 publications

(25 citation statements)

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“…The Sanandaj-Sirjan zone (SaSZ) is a metamorphic-magmatic belt in western Iran and has a width of 50-150 km and a length of 1200 km [33][34][35]. In the northern SaSZ, the Ghorveh district consists of a Jurassic metamorphic complex, a suite of greenschist, marble, amphibolite, and quartzite with several stages of deformation [30], and some igneous rock, aplite, and pegmatite with ages of 180-140 Ma intruded into the Jurassic metamorphic complex [36][37][38][39] (Figure 2a). The largest pegmatite outcrop is found in the Ebrahim-Attar Mountains in southwest Ghorveh, west of Iran (Figure 2b).…”

Section: Geological Setting and Mineralogymentioning

confidence: 99%

“…This mountain is surrounded by the 157 Ma Moshir Abad granite [38] in the north and the 157.9 (±1.6) Ma Ghalaylan granite in the south [36] as determined by zircon U-Pb dating. Rb-Sr dating yielded an age of 102.5 ± 6.1 Ma for the Ebrahim-Attar pegmatite [30] (Figure 2b). The predominant signatures of this pluton are highly peraluminous leucogranite with megacrysts of K-feldspar.…”

Section: Geological Setting and Mineralogymentioning

confidence: 99%

“…Most LCT pegmatites have peraluminous signatures that are determined by the melting of pelitic rocks related to the thickness of the continental crust during collision [24] to a postcollisional tectonic regime [25]. Some beryl-bearing pegmatites have been reported in Iran, including Khajeh Morad in south Mashhad [26,27], Kamari-Zaman Abad-Dehno in south Hamedan [28,29], and Ebrahim-Attar in southwest Ghorveh [26,28,[30][31][32] (Figure 1). The Ebrahim-Attar granitic pegmatite of Ghorveh district in the Sanandaj-Sirjan zone (SaSZ) is one of the most important semigemstone sources in Iran (Figure 2a).…”

Section: Introductionmentioning

confidence: 99%

“…The granitic pegmatite is widely exposed in two nearby district areas called Ebrahim-Attar 1 and Ebrahim-Attar 2. It is an active feldspar mine and, to a lesser extent, mica and beryl [30].…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry and Genesis of Beryl Crystals in the LCT Pegmatite Type, Ebrahim-Attar Mountain, Western Iran

et al. 2021

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Ebrahim-Attar granitic pegmatite, which is distributed in southwest Ghorveh, western Iran, is strongly peraluminous and contains minor beryl crystals. Pale-green to white beryl grains are crystallized in the rim and central parts of the granite body. The beryl grains are characterized by low contents of alkali oxides (Na2O = 0.24–0.41 wt.%, K2O = 0.05–0.17 wt.%, Li2O = 0.03–0.04 wt.%, and Cs2O = 0.01–0.03 wt.%) and high contents of Be2O oxide (10.0 to 11.9 wt.%). The low contents of alkali elements (oxides), low Na/Li (apfu) ratios (2.94 to 5.75), and variations in iron oxide (FeO= 0.28–1.18 wt.%) reveal a poorly evolved magmatic source of the beryl grains. Low abundances of rare earth elements (ΣREE = 0.8–4.9 ppm) with high 87Sr/86Sr(i) ratios of 0.739 ±0.036 for the beryl grains and 0.7081 for the host granites infer that the primary magma was directly produced by partial melting of the upper continental crust (UCC). The crystallization temperature of the Ebrahim-Attar granitic pegmatite changes from 586 to 755 °C (average = 629 °C), as calculated based on the zircon saturation index. Furthermore, the quartz geobarometer calculation shows that crystallization occurred at pressures of approximately 233–246 MPa. This pressure range is a promising condition for saturation of Be in magma. During granitic magma crystallization, the melt was gradually saturated with Be, and then beryl crystallized in the assemblage of the main minerals such as quartz and feldspar. Likewise, the host granite is characterized by high ratios of Nb/Ta (4.79–16.3) and Zr/Hf (12.2–19.1), and peraluminous signatures are compatible with Be-bearing LCT (Li-Ce and Ta) pegmatites.

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Section: Geological Setting and Mineralogymentioning

confidence: 99%

Section: Geological Setting and Mineralogymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geochemistry and Genesis of Beryl Crystals in the LCT Pegmatite Type, Ebrahim-Attar Mountain, Western Iran

et al. 2021

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“…Dur ing Oligocene-Mio cene times, the end of the Neotethys subduction might have oc curred be neath Cen tral Iran in the north west ern part of Iran (Molinaro et al, 2005;Vergés et al, 2011;Shafiei Bafti and Mohajjel, 2015;Azizi et al, 2016;Hassanzadeh and Wernicke, 2016;Fig. 7).…”

Section: Discussion Tectonic Implicationsmentioning

confidence: 99%

Geochemical and tectonic significance of Arbat alkali gabbro-monzonite-syenite intrusions, Urumieh–Dokhtar Magmatic Arc, Iran

Fazlnia

2019

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As so ci ate ed i tor: Tomasz Bajda The Oligocene Arbat al kali in tru sions of the East ern Miandoab are lo cated in the northwest ern part of Iran and be long to the Urumieh-Dokhtar Mag matic Arc (UDMA). The in tru sions show a ring struc ture with gab bro-monzogabbro-monzodiorite (mafic units) on the edges, with monzonite-monzosyenite-syenite (fel sic units) grad u ally go ing to wards the cen tral parts. The tex tures in dif fer ent rock types are cu mu late, gran u lar and lam i nated. The high val ues of (La/Sm) n and (La/Yb) n, con tents of K, Rb and Cs (pos i tive anom a lies nor mal ized on the ba sis of the prim i tive man tle), low con cen tra tions of Hf, Nb, Zr and Ta (neg a tive anom a lies), and the changes in Th/Nb, Th/Ta, La/Nb and Ce/Pb ra tios along with the geo chem i cal and tec tonic set ting ev i dence ex hibit a subduction-mod i fied man tle or i gin for the for ma tion of these rocks. Ac cord ingly, the in tru sions were formed be tween the Cen tral Iran and the Ara bian plates as a re sult of the par tial melt ing of a man tle wedge at a syn-colli sion or post-col li sion arc-re lated en vi ron ment. Our data sug gested that, af ter the end of the oblique Neotethys subduction and dur ing/af ter the con ti nen tal col li sion, the break-off or roll back of the Neotethys slab be neath west ern Iran, in the Oligocene, might have oc curred. Such a pro cess led to the change in the geo ther mal gra di ent of the man tle wedge be cause of the subduction flu ids, transtension, pres sure re duc tion along the SE-trending lat eral depth strike-slip fault zones in the upper part of the man tle wedge, de com pres sion par tial melt ing at the man tle, and the re sult ing for ma tion of a mafic po tassium-rich melt. The mafic magma was in jected into crustal magma cham bers; prob a bly, the frac tional crys tal li za tion and par tial con tam i na tion oc curred with crustal com po nents, form ing the in ter me di ate and fel sic rocks in the in tru sions. Geochem i cal ev i dence re lated to the vari a tions in the ra tios of Th/Yb, Ta/Yb, Rb/Y, and Nb/Y and Harker vari a tion di a grams along with the spi der di a grams con firmed frac tional crys tal li za tion and par tial FC (frac tional crys tal li za tion) and AFC (as sim ila tion and frac tional crys tal li za tion) in the in tru sions.

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Zircon U–Pb and titanite U–Th–Pb ages of the Ghorveh mixed granitoid pluton: Implications for the Late Jurassic supra‐subduction extension of the Sanandaj–Sirjan Zone, Iran

et al. 2022

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The Ghorveh batholith, located in the central part of the Sanandaj–Sirjan Zone (SSZ), Iran, preserves several sequences of Mesozoic plutonic and volcanic rocks. This study presents systematic analyses of the calc‐alkaline granites and monzodiorites from the southern part of the Ghorveh pluton. The granites are metaluminous to slightly peraluminous with A/CNK ratios of 0.97–1.02, indicating an A‐type granitic affinity. High Rb, Th, and K and low Sr, P, and Ti concentrations indicate an involvement of crustal materials. Whole‐rock negative εNd(t) values and relatively high TDM1 model ages support a continental crustal source. Thus, the granites are of fractionated A‐type in composition produced by partial melting of crustal materials. The monzodiorites have incompatible trace element patterns with enrichment in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) relative to heavy rare earth elements and high‐field strength elements. This combined with the high Mg# values and the positive εNd and εHf(t) values, indicate a mantle‐derived origin. Dating results show that the granites and monzodiorites have uniform crystallization ages of ~150 Ma. Previous results and our new data suggest that the Jurassic subduction of Neo‐Tethyan Oceanic crust under the Eurasian continent was followed by slab rollback that induced back‐arc extension. Heat transfer from arc magmas increased the degree of decompressional melting in the thinned lithosphere. Melting of the presumably homogeneous crust was concurrent with emplacement of the intermediate composition magmas. Consequently, we propose that the Ghorveh area of the central SSZ developed in a supra‐subduction extensional phase during the Late Jurassic.

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Strongly peraluminous leucogranite (Ebrahim-Attar granite) as evidence for extensional tectonic regime in the Cretaceous, Sanandaj Sirjan zone, northwest Iran

Cited by 30 publications

References 53 publications

Geochemistry and Genesis of Beryl Crystals in the LCT Pegmatite Type, Ebrahim-Attar Mountain, Western Iran

Geochemistry and Genesis of Beryl Crystals in the LCT Pegmatite Type, Ebrahim-Attar Mountain, Western Iran

Geochemical and tectonic significance of Arbat alkali gabbro-monzonite-syenite intrusions, Urumieh–Dokhtar Magmatic Arc, Iran

Zircon U–Pb and titanite U–Th–Pb ages of the Ghorveh mixed granitoid pluton: Implications for the Late Jurassic supra‐subduction extension of the Sanandaj–Sirjan Zone, Iran

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