Latest Oligocene adakitic rocks in western Iran: implications for early crustal thickening and tectonic evolution of the Iran Block
Latest Oligocene adakitic rocks in western Iran: implications for early crustal thickening and tectonic evolution of the Iran Block
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伊朗西部最新渐新世埃达克岩：对伊朗地块早期地壳增厚和构造演化的影响
DOI：
10.1144/jgs2022-020
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发表时间：
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影响因子：
2.7
通讯作者：
Xu JiFeng
中科院分区：
文献类型：
--
作者：
Liu Yixing;Chen JianLin;Yang TianNan;Hou ZengQian;Zhang HongRui;Yang ZhiMing;Yang ZhuSeng;Aghazadeh M;Xu JiFeng
埃达克质岩石产于各种构造环境中，是了解造山带构造演化和地球动力学的关键。研究了伊朗乌鲁木齐-多克塔岩浆带西段渐新世晚期（23.5- 22.5Ma）的石英二长岩和花岗岩，它们可能形成于阿拉伯-欧亚大陆碰撞的早期阶段。 岩石具有典型埃达克岩的地球化学特征，高SiO2（60.18- 68.82wt%）和Sr（499-793 ppm），低Y（8.90- 17.1ppm）和Yb（0.88- 1.58ppm），高Sr/Y（26.1 × 67.8）和（La/Yb）N（21.9 × 32.9）。 它们具有可变的K2 O（3.88- 5.09wt%）、MgO（0.44- 2.74wt%; Mg# = 33.7-52.5）、Cr（4.27- 40.59ppm）、Ni（4.28- 35.68ppm）和Th（9.56- 59.59ppm）含量和相对亏损的Sr-Nd同位素组成[（87 Sr/86 Sr）i= 0.70450-0.70516;Nd（t）= 2.1-2.7]。 这些特征表明，石英二长岩来自拆离下地壳的部分熔融，并与富含MgO、Cr、Ni和亏损Sr-Nd同位素组成的地幔橄榄岩相互作用，表明花岗岩是由石英二长岩浆分离结晶形成的。因此，所研究的埃达克质岩石的地球化学特征可能受到岩浆过程（例如分离结晶）的影响，这可能会误导对其岩石成因和相关构造环境的解释。研究岩石的地球化学特征表明，在渐新世末（约23.5Ma），由于阿拉伯-欧亚大陆碰撞作用，乌鲁木齐-多克塔尔岩浆带西段地壳增厚50 ± 4.43km。补充资料：全岩地球化学和Sr-Nd同位素组成，锆石U-Pb和Lu-Hf同位素数据可在https://doi.org/10.6084/m9.figshare.c.6188328上获得
Adakitic rocks occur in a variety of tectonic settings and are key to understanding the tectonic evolution and geodynamics of orogenic belts. We investigated latest Oligocene (23.5–22.5 Ma) quartz monzonites and granites from the western segment of the Urumieh–Dokhtar magmatic belt in Iran, which are likely to have formed in response to the early stages of Arabia–Eurasia collision. The studied rocks have the geochemical characteristics of typical adakites, such as high SiO2(60.18–68.82 wt%) and Sr (499–793 ppm) contents, low Y (8.90–17.1 ppm) and Yb (0.88–1.58 ppm) contents, and high Sr/Y (26.1‒67.8) and (La/Yb)N(21.9‒32.9) ratios. They have variable K2O (3.88–5.09 wt%), MgO (0.44–2.74 wt%; Mg# = 33.7–52.5), Cr (4.27–40.59 ppm), Ni (4.28–35.68 ppm) and Th (9.56–59.59 ppm) contents, and relatively depleted Sr–Nd isotopic compositions [(87Sr/86Sr)i= 0.70450–0.70516;Nd(t) = 2.1–2.7]. These characteristics indicate that the quartz monzonites were derived from the partial melting of delaminated lower crust that interacted with mantle peridotite with high MgO, Cr and Ni contents and depleted Sr–Nd isotopic compositions and suggest that the granites were formed by the fractional crystallization of quartz monzonitic magma. The geochemical features of the studied adakitic rocks could therefore have been affected by magmatic processes (e.g. fractional crystallization), which might be misleading in interpretations of their petrogenesis and related tectonic settings. The geochemical features of the studied rocks indicate that the crust of the western segment of the Urumieh–Dokhtar magmatic belt was thickened toc.50 ± 4.43 km during the latest Oligocene (c.23.5 Ma) as a result of Arabia–Eurasia collision.Supplementary material:Whole rock geochemical and Sr–Nd isotopic compositions, and zircon U–Pb and Lu–Hf isotopic data are available at https://doi.org/10.6084/m9.figshare.c.6188328