Intrusive rocks are well-exposed in the south Birjand around the Koudakan is herein compared to previously studied outcrops along the middle Eocene to late Oligocene Eastern Iran Magmatic Belt. This pluton is composed mainly of monzonite, quartz-monzonite, and granite with high-K calc-alkaline to shoshonitic affinities. The U-Pb zircon geochronology from monzonite and quartz-monzonite reveals the crystallization ages of 40.96 ± 0.48 to 38.78 ± 0.78 Ma (Bartonian). The monzonite, quartz-monzonite, and granite rocks show similar REEs and trace element patterns, as well as limited variations in εNd_(i) and ⁸⁷Sr/⁸⁶Sr_(i) ratio, suggesting that they are a comagmatic intrusive suite. The chondrite and primitive mantle normalized rare earth and trace element patterns show enrichment in the light rare earth elements, K, Rb, Cs, Pb, Th, and U and depletion in heavy rare earth elements, Nb, Zr, and Ti. The εNd_(i) and ⁸⁷Sr/⁸⁶Sr_(i) values range from +1.32 to +1.68 and 0.7044 to 0.7047, respectively, identical to island-arc basalt composition. The whole-rock Nd model age (T_DM) for the intrusive rocks range between 0.69 and 0.73 Ga. These geochemical and isotopic signatures indicate a subduction-related sub-continental lithospheric mantle source for these rocks. Our new geochemical, isotopic, and geochronological studies integrated with previously published data indicate that the middle Eocene to late Oligocene magmatism in eastern Iran was formed in a post-collisional tectonic environment. We suggest the northeastward subduction of the Neo-Tethys ocean beneath the Lut block and the eastward subduction of the Sistan ocean beneath the Afghan block caused mantle wedge to be metasomatized by slab components. At a later stage, a collision between the Lut and Afghan blocks was accompanied by the lithospheric delamination, and the subsequent asthenospheric upwelling led to the melting of the metasomatized sub-continental lithospheric mantle and the generation of middle Eocene to late Oligocene magmatism in the Eastern Iran Magmatic Belt.

与先前研究的沿中始新世至渐新世晚期伊朗东部岩浆带的露头相比，侵入岩在Koudakan附近的南部Birjand暴露得很好。该岩体主要由锰铁矿，石英-锰铁矿和对钾铁矿具有亲和力的高K钙碱性花岗岩组成。蒙脱石和石英蒙脱石的U-Pb锆石年代学揭示了40.96±0.48至38.78±0.78 Ma（巴顿式）的结晶年龄。蒙脱石，石英蒙脱石和花岗岩岩石显示出相似的稀土元素和痕量元素模式，并且εNd _（i）和⁸⁷ Sr / ⁸⁶ Sr _（i）的变化有限。比率，表明它们是一个令人着迷的侵入套件。球粒陨石和原始地幔归一化稀土元素和痕量元素模式显示出轻稀土元素K，Rb，Cs，Pb，Th和U中的富集，而重稀土元素Nb，Zr和Ti中的贫化。εNd _（i）和⁸⁷ Sr / ⁸⁶ Sr _（i）值的范围分别为+1.32至+1.68和0.7044至0.7047，与岛弧玄武岩组成相同。全岩Nd模型时代（T _DM）范围为0.69至0.73 Ga。这些地球化学和同位素特征表明这些岩石具有俯冲作用相关的亚大陆岩石圈地幔源。我们的新地球化学，同位素和地球年代学研究与先前发表的数据相结合，表明伊朗东部的中始新世至晚渐新世岩浆作用是在碰撞后的构造环境中形成的。我们建议将新特提斯洋向北俯冲到卢特地块之下，将锡斯坦海向东俯冲到阿富汗地块之下，使地幔楔被板状成分交代。在稍后的阶段，卢特（Lut）和阿富汗（阿富汗）地块之间发生碰撞，并伴有岩石圈剥落，