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首页> 外文期刊>Contributions to Mineralogy and Petrology >Quaternary high-Mg ultrapotassic rocks from the Qal'eh Hasan Ali maars, southeastern Iran: petrogenesis and geodynamic implications
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Quaternary high-Mg ultrapotassic rocks from the Qal'eh Hasan Ali maars, southeastern Iran: petrogenesis and geodynamic implications

机译：来自伊朗东南部Qal'eh Hasan Ali maars的第四纪高镁超钾盐岩：岩石成因和地球动力学意义

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A set of rare, high-Mg ultrapotassic rocks from the Qal'eh Hasan Ali maars, southeastern Iran, was investigated using phlogopite Ar-40/Ar-39 geochronology, olivine chemistry, and bulk-rock elemental and Sr-Nd-Hf isotopic geochemistry to decipher their petrogenesis and regional tectonic implications. Phlogopite separates yield inverse isochron Ar-40/Ar-39 ages from ca. 112 to 119 ka, indicating that magma genesis postdated the onset of the Arabia Eurasia collision at the Late Eocene-Early Oligocene. The studied rocks are characterized by kamafugitic affinity with relatively low SiO2 and Al2O3 and high CaO and Sr. They contain relatively primitive olivine (Fo(85-92)) that, on the basis of olivine liquid Fe/Mg exchange equilibrium, suggests the primary melt to be ultrapotassic with similar to 13 wt% MgO. Other key geochemical features include extreme enrichment in most incompatible trace elements, depletions in Nb, Ta, P and Ti and enrichment in Pb relative to elements of similar incompatibilities. The Sr-Nd-Hf isotopic ratios of the rocks do not deviate significantly from the bulk silicate Earth (Sr-87/Sr-86 = 0.7055-0.7059, Nd-143/Nd-144 = 0.5125-0.5126 and Hf-176/Hf-177 = 0.2827-0.2829). Relatively high Zn/Fe, Gd/Yb, Rb, Rb/Sr and P2O5 and low Yb and P/P* for the rocks are consistent with derivation from a mantle source containing clinopyroxene, phlogopite, apatite and garnet that formed in response to modal metasomatism in the lithospheric mantle. Relatively low Hf/Nd and high Sr/Hf of the rocks indicate that the metasomatized lithologies from which the studied rocks formed were derived dominantly from subducted marly sediments. The Qat'eh Hasan Ali magmatism is best explained by small-scale destruction of the continental mantle in a post-collisional setting, presumably driven by localized convective instability as a result of the Arabia Eurasia collision.
机译：使用金云母Ar-40 / Ar-39年代学，橄榄石化学以及块状岩石元素和Sr-Nd-Hf同位素研究了伊朗东南部Qal'eh Hasan Ali maars的一组罕见的高镁超钾盐岩地球化学来解释其成因和区域构造意义。金云母将产率逆等时Ar-40 / Ar-39年龄从ca. 112至119 ka，表明岩浆成因是晚始新世-早渐新世阿拉伯阿拉伯欧亚大陆碰撞发生的开始。所研究的岩石的特征是具有卡马伏特亲和力，具有较低的SiO2和Al2O3以及较高的CaO和Sr.它们包含相对原始的橄榄石（Fo（85-92）），在橄榄石液态Fe / Mg交换平衡的基础上，表明其主要熔化成超钾盐，MgO含量接近13 wt％。其他关键的地球化学特征包括与大多数不相容元素的极度富集，Nb，Ta，P和Ti的耗竭以及相对于相似不相容元素的Pb富集。岩石的Sr-Nd-Hf同位素比与整体硅酸盐地球没有显着偏离（Sr-87 / Sr-86 = 0.7055-0.7059，Nd-143 / Nd-144 = 0.5125-0.5126和Hf-176 / Hf -177 = 0.2827-0.2829）。岩石中较高的Zn / Fe，Gd / Yb，Rb，Rb / Sr和P2O5以及较低的Yb和P / P *与来自含金藤辉石，金云母，磷灰石和石榴石的地幔来源的衍生相一致岩石圈地幔中的交代作用。岩石相对较低的Hf / Nd和较高的Sr / Hf表明，形成研究岩石的交代岩性主要来自俯冲的马来沉积物。卡塔尔哈桑·阿里岩浆的最好解释是在碰撞后环境中对大陆幔的小规模破坏，这可能是由于阿拉伯亚欧亚大陆碰撞造成的局部对流不稳定所致。

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