The Late Jurassic Panjeh submarine volcano in the northern Sanandaj-Sirjan Zone, northwest Iran: Mantle plume or active margin?
The Late Jurassic Panjeh submarine volcano in the northern Sanandaj-Sirjan Zone, northwest Iran: Mantle plume or active margin?
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DOI：
10.1016/j.lithos.2018.03.019
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发表时间：
2018-05
期刊：
影响因子：
3.5
通讯作者：
H. Azizi;F. Lucci;R. Stern;Shima Hasannejad;Y. Asahara
中科院分区：
文献类型：
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作者：
H. Azizi;F. Lucci;R. Stern;Shima Hasannejad;Y. Asahara
伊朗萨南达吉-锡尔詹地区侏罗纪火成岩形成的构造背景一直存在争议。SaSZ火成岩主要为侵入早、中侏罗世变质基底的花岗闪长岩至辉长岩，侏罗系火山岩较少。在这里，我们报告的火山岩的年龄和岩石学从Panjeh玄武安山岩复杂的北方SaSZ，Ghorveh市西南。Panjeh岩浆杂岩由枕状和块状玄武岩、安山岩和微闪长岩脉组成，并与侵入辉长岩有关;整体序列和与周围沉积物的关系表明，这是一个保存异常完好的海底火山杂岩。火成岩属于偏铝质亚碱性、中钾至高钾钙碱性镁铁质岩组，其特征为中等Al 2 O3（13.7- 17.6wt%）和可变Fe 2 O3（6.0- 12.6wt%）和MgO（0.9- 11.1wt%）含量。锆石U-Pb年龄（145-149 Ma）确定了岩浆结晶侵位的晚侏罗世（提顿期）年龄。全岩成分富集Th、U和轻稀土元素，Nb、Ta和Ti略有亏损。87 Sr/86 Sr（0.7039-0.7076）和εNd（t）值（-1.8 ~+4.3）的初始值沿着地幔序列分布于洋岛玄武岩和陆下交代地幔区。不动微量元素（Ti、V、Zr、Y、Nb、Yb、Th和Co）的行为表明，地幔源区是由俯冲板片释放的流体富集的（即深地壳再循环），对于安山岩，陆壳也有一定贡献。根据Panjeh镁铁质岩和中间岩的化学成分，结合Ghorveh地区其他辉长岩-闪长岩体的数据，我们对这些岩体提出了两种解释。（和SaSZ的其他侏罗纪火成岩）反映了a）在新特提斯俯冲带之上的俯冲-修改的OIB型源或B）涉及上涌交代地幔的羽流或裂谷构造的熔体（主要反映~550 Ma的Cadomian成壳事件）。
The tectonic setting in which Jurassic igneous rocks of the Sanandaj-Sirjan Zone (SaSZ) of Iran formed is controversial. SaSZ igneous rocks are mainly intrusive granodiorite to gabbroic bodies, which intrude Early to Middle Jurassic metamorphic basement; Jurassic volcanic rocks are rare. Here, we report the age and petrology of volcanic rocks from the Panjeh basaltic-andesitic rocks complex in the northern SaSZ, southwest of Ghorveh city. The Panjeh magmatic complex consists of pillowed and massive basalts, andesites and microdioritic dykes and is associated with intrusive gabbros; the overall sequence and relations with surrounding sediments indicate that this is an unusually well preserved submarine volcanic complex. Igneous rocks belong to a metaluminous sub-alkaline, medium-K to high-K calc-alkaline mafic suite characterized by moderate Al2O3(13.7–17.6 wt%) and variable Fe2O3(6.0–12.6 wt%) and MgO (0.9–11.1 wt%) contents. Zircon U-Pb ages (145–149 Ma) define a Late Jurassic (Tithonian) age for magma crystallization and emplacement. Whole rock compositions are enriched in Th, U and light rare earth elements (LREEs) and are slightly depleted in Nb, Ta and Ti. The initial ratios of87Sr/86Sr (0.7039–0.7076) and εNd(t) values (−1.8 to +4.3) lie along the mantle array in the field of ocean island basalts and subcontinental metasomatized mantle. Immobile trace element (Ti, V, Zr, Y, Nb, Yb, Th and Co) behavior suggests that the mantle source was enriched by fluids released from a subducting slab (i.e. deep-crustal recycling) with some contribution from continental crust for andesitic rocks. Based the chemical composition of Panjeh mafic and intermediate rocks in combination with data for other gabbroic to dioritic bodies in the Ghorveh area we offer two interpretations for these (and other Jurassic igneous rocks of the SaSZ) as reflecting melts from a) subduction-modified OIB-type source above a Neo-Tethys subduction zone or b) plume or rift tectonics involving upwelling metasomatized mantle (mostly reflecting the ~550 Ma Cadomian crust-forming event).