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首页> 外文期刊>Journal of Asian earth sciences >Petrochemistry of the Siah-Kuh granitoid stock southwest of Kerman, Iran: Implications for initiation of Neotethys subduction
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Petrochemistry of the Siah-Kuh granitoid stock southwest of Kerman, Iran: Implications for initiation of Neotethys subduction

机译：伊朗克尔曼西南部Siah-Kuh花岗岩储层的石油化学：对新特提斯俯冲作用的启示

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The Upper Triassic Siah-Kuh granitoid stock is part of a series of Triassic-Cretaceous intrusions in the Phanerozoic Sanandaj-Sirjan zone in the Zagros orogenic belt, south-central Iran. The Siah-Kuh stock intrudes Lower Paleozoic amphibolites of the Abshur meta-morphic complex and Upper Devonian-Lower Carboniferous greenschists of the Sargaz metamorphic complex. The Siah-Kuh granitoid stock consists mainly of coarse to medium grained leucogranodiorite, leucomonzogranite and alkali granite with subordinate syenite. It also contains a number of mafic enclaves of different sizes and is intruded by alkali granite and granophyre dikes along with monzonitic and a few dioritic dikes. The Siah-Kuh granitoid rocks are characterized by enrichment in large ion lithophile elements (LILE) such as Rb, Ba, K, Ce and depletion in high field strength elements (HFSE) such as Y, Nb and Zr. The chondrite normalized REE patterns are characterized by moderate LREE enrichment [(La/Yb)_N = 1.31-4.82] and unfractionated HREE [(Gd/Yb)_N = 0.50 to 1.33]. Granodi-orites with the least fractionated HREE and a general absence of Eu anomalies suggest the involvement of plagioclase and absence of garnet during the melting processes. Alkali granites with the highest (La/Yb)_N values and pronounced negative Eu anomalies are more differentiated products. Nd isotope analyses of the Siah-Kuh granitoids yield an "errorchron" age of 199 ± 30 Ma (MSWD = 1.30), consistent with the field relationships and give Nd model ages (T_(DM)) from 0.81 to 1.64 Ga and εNd(T) values from +1.81 to +2.45 at 200 Ma. These geochemical data suggest that the Siah-Kuh granitoid stock has characterisitics of metaluminous to slightly peralumi-nous, calc-alkaline, Ⅰ-type granite formed in a volcanic arc setting. The onset of subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent in Triassic time could have accounted for the continental arc volcanism. Dehydration of subducted oceanic crust and partial melting of mantle wedge caused partial melting of subcontinental lithosphere, which resulted in the formation of metasomatised and enriched mafic arc magmas, at variable water fugacity and led to the formation of the Siah-kuh granitoid rocks.
机译：上三叠世Siah-Kuh花岗岩体是伊朗中南部Zagros造山带Phanerozoic Sanandaj-Sirjan地区三叠纪-白垩纪侵入岩系列的一部分。 Siah-Kuh储层侵入了Abshur变质复合体的下古生界闪石和Sargaz变质复合体的上泥盆纪-下石炭纪绿岩。 Siah-Kuh花岗岩类储层主要由粗粒至中粒状的白云母闪长岩，白云母花岗石和碱性花岗石以及次要的沸石组成。它也包含许多不同大小的镁铁质飞地，并被碱性花岗岩和花岗石堤以及单核和一些二色岩堤侵入。 Siah-Kuh花岗岩岩石的特征是富集了诸如Rb，Ba，K，Ce等大型离子亲石元素（LILE），而贫化了诸如Y，Nb和Zr等高场强元素（HFSE）。球粒陨石归一化REE模式的特征是中等程度的LREE富集[（La / Yb）_N = 1.31-4.82]和未分级的HREE [（Gd / Yb）_N = 0.50至1.33]。 HREE分级最少且Eu异常普遍不存在的花岗橄榄岩表明，在熔化过程中斜长石酶参与且石榴石不存在。 （La / Yb）_N值最高且Eu异常明显的碱花岗岩是差异较大的产物。 Siah-Kuh花岗岩的Nd同位素分析产生了199±30 Ma（MSWD = 1.30）的“错误时间”年龄，与场关系一致，并给出了0.81至1.64 Ga和εNd（N_（DM））的Nd模型年龄（T_（DM））。 T）值在200 Ma下从+1.81到+2.45。这些地球化学数据表明，Siah-Kuh花岗岩体具有在火山弧环境下形成的金属至轻度钙铝，钙碱性，I型花岗岩的特征。在三叠纪，新特提斯洋壳在伊朗中部微大陆之下俯冲的开始可能解释了大陆弧火山作用。俯冲洋壳的脱水和地幔楔的部分融化导致了次大陆岩石圈的部分融化，这导致交变富集的镁铁质弧状岩浆形成了可变的水逸度，并导致了Siah-kuh花岗岩的形成。

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