Zircon U-Pb geochronology and geochemistry of Late Devonian–Carboniferous granitoids in NW Iran: implications for the opening of Paleo-Tethys

We present zircon U-Pb crystallization ages combined with bulk rock major and trace element geochemistry and Sr-Nd-Pb and zircon <i>in-situ</i> Hf isotopic compositions of the Amand and Moro granitoid intrusions in northwest Iran. The Amand and Moro plutons include granite and syeno-diorite with LA-ICP-MS U-Pb zircon ages of 367 ± 6.8 Ma and 351 ± 1.3 Ma, respectively, representative of Late Devonian-Early Carboniferous magmatic activity in NW Iran. Geochemical characteristics such as typical enrichments in alkalis, Nb, Zr, Ga and Y, depletion in P and Sr and fractionated REE patterns with high Ga/Al ratios and Eu negative anomalies are consistent with A-type magmatic signatures. The granitoids are classified as A₂-type and within-plate granitoids. The bulk rock geochemistry (enrichments in Th, Nb and, high Th/Yb, Zr/Y ratios) along with low variation of ¹⁴³Nd/¹⁴⁴Nd_(i) and ⁸⁷Sr/⁸⁶Sr_(i) ratios and positive zircon εHf_(t) support the role of a mantle plume component for the evolution of the Amand and Moro A-type granitoids in an extensional tectonic environment. In fitting with wider regional knowledge, this magmatism occurred during Paleo-Tethys opening in northern Gondwana.

本数据集收录伊朗西北部阿曼德（Amand）与莫罗（Moro）花岗岩类侵入体的锆石U-Pb结晶年龄，配套全岩主量与微量元素地球化学数据、Sr-Nd-Pb同位素组成及锆石原位Hf同位素组成数据。阿曼德与莫罗岩体包含花岗岩与正长闪长岩，其LA-ICP-MS锆石U-Pb年龄分别为367±6.8 Ma与351±1.3 Ma，代表伊朗西北部晚泥盆世-早石炭世的岩浆活动。该花岗岩类的地球化学特征——如碱质、铌（Nb）、锆（Zr）、镓（Ga）与钇（Y）显著富集，磷（P）与锶（Sr）亏损，稀土配分呈分馏模式且具备高Ga/Al比值与铕负异常——均符合A型花岗岩的岩浆标识。此类花岗岩被归为A₂型板内花岗岩类。全岩地球化学特征（钍（Th）、铌（Nb）富集，高Th/Yb、Zr/Y比值），加之初始¹⁴³Nd/¹⁴⁴Nd与初始⁸⁷Sr/⁸⁶Sr比值的低变化幅度，以及锆石εHf(t)正值，均支持地幔柱组分在阿曼德与莫罗A型花岗岩演化过程中的作用，其形成背景为伸展构造环境。结合更广范围的区域地质认知，该岩浆活动发生在冈瓦纳大陆北部古特提斯洋张开时期。