Metamorphic rocks associated with ophiolitic rocks occur on the eroded surface of a NW–SE-trending anticline in the Allahyarlu area, NW Iran, between the Caucasus and Zagros orogenic belts. Metapelitic rocks consist mainly of quartz, muscovite chlorite, altered biotite and garnet. S1 is the pervasive schistosity, wrapping garnet, which is folded by the second schistosity (S2). The amphibolite records only one phase of deformation as the main lineation. The rocks experienced metamorphism up to the amphibolite facies, then overprinted by greenschist facies condition. Thermobarometry indicates an average pressure of c. 5 kbar and an average temperature of c. 600 °C for the amphibolite facies metamorphism, corresponding to a ∼33 °C km−1 geothermal gradient in response to a thick magmatic arc setting. Greenschist facies metamorphism shows re-equilibration of the rocks during exhumation. Amphibolites whole rock geochemistry shows trace elements patterns similar to both island arc and back-arc basin basalts, suggesting that the protolith-forming magma of the amphibolites was enriched at shallow to medium depth of a subduction system. Negative Nb anomaly and slight enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE) of the amphibolites indicate arc-related magmatism for their protolith and a back-arc sialic setting for their formation. 40Ar–39Ar dating on muscovite separated from two gneiss samples, and hornblende separated from three amphibolite samples, documents a Variscan (326–334 Ma) age. The magmatic and metamorphic rock association of the Allahyarlu area suggests the existence of an active continental margin arc during the Variscan orogeny, without clear evidence for a continental collision.

中文翻译：

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伊朗西北部 Allahyarlu 复合体的 Variscan 变质岩的原石性质和 P-T 演化

与蛇绿岩相关的变质岩出现在伊朗西北部 Allahyarlu 地区高加索和扎格罗斯造山带之间的 NW-SE 向背斜的侵蚀表面上。变泥质岩主要由石英、白云母绿泥石、蚀变黑云母和石榴石组成。小号1是普遍的片理，包裹石榴石，被第二个片理折叠（S2）。角闪岩仅记录一期变形为主线。岩石经历变质作用直至角闪岩相，然后被绿片岩相条件叠印。热气压法表明平均压力为C。5 kbar 和平均温度C。角闪岩相变质作用为 600 °C，对应于 ∼33 °C km-1响应厚岩浆弧设置的地温梯度。绿片岩相变质作用表明岩石在折返过程中重新平衡。角闪岩全岩地球化学显示出与岛弧和弧后盆地玄武岩相似的微量元素模式，表明角闪岩的原岩形成岩浆在俯冲系统的浅至中等深度富集。角闪岩的Nb负异常和轻稀土元素（LREE）和大离子亲石元素（LILE）的轻微富集表明它们的原岩与弧相关的岩浆作用和它们的形成为弧后唾液酸环境。40氩–39从两个片麻岩样品中分离出白云母的 Ar 测年，从三个角闪岩样品中分离出角闪石，记录了 Variscan (326-334 Ma) 年龄。Allahyarlu 地区的岩浆和变质岩组合表明在 Variscan 造山运动期间存在活跃的大陆边缘弧，但没有明确的大陆碰撞证据。