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,Geological Journal

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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
Geological Journal ( IF 1.4 ) Pub Date : 2022-09-06 , DOI: 10.1002/gj.4580
Zhong‐Mei Wang ₁ , Chun‐Ming Han _{2,

3} , Wen‐Jiao Xiao _{3,

4} , Zhi‐Yong Zhang ₄

Affiliation

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 ε_Nd(t) values and relatively high T_DM1 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 ε_Nd and ε_Hf(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.

中文翻译：

Ghorveh 混合花岗岩岩体的锆石 U-Pb 和钛矿 U-Th-Pb 年龄：对伊朗 Sanandaj-Sirjan 带晚侏罗世超俯冲延伸的意义

Ghorveh 岩基位于伊朗 Sanandaj-Sirjan 地带 (SSZ) 的中部，保存着数个中生代深成岩和火山岩序列。本研究对 Ghorveh 深成岩体南部的钙碱性花岗岩和二长闪长岩进行了系统分析。花岗岩为偏铝质至轻微过铝质，A/CNK 比率为 0.97–1.02，表明 A 型花岗岩亲和力。高 Rb、Th 和 K 以及低 Sr、P 和 Ti 浓度表明涉及地壳物质。全岩负ε _Nd ( t ) 值和相对较高的 T _DM1模型年龄支持大陆地壳来源。因此，花岗岩在成分上属于分馏的 A 型，由地壳物质的部分熔融产生。相对于重稀土元素和高场强元素，二长闪长岩具有不相容的微量元素模式，轻稀土元素 (LREE) 和大离子亲石元素 (LILE) 富集。这与高 Mg# 值和正的ε _Nd和ε _Hf ( t) 值，表明起源于地幔。测年结果表明，花岗岩和二长闪长岩具有约 150 Ma 的均匀结晶年龄。先前的结果和我们的新数据表明，欧亚大陆下新特提斯洋地壳的侏罗纪俯冲之后是板块回滚，导致弧后伸展。来自弧形岩浆的热传递增加了变薄岩石圈中减压熔化的程度。假定均质地壳的熔化与中间成分岩浆的侵位同时发生。因此，我们提出中部 SSZ 的 Ghorveh 地区在晚侏罗世期间在超俯冲伸展阶段发育。

更新日期：2022-09-06

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