内蒙古阿拉善右旗杭嘎勒晚二叠世二长花岗岩地球化学特征和LA-ICP-MS锆石U-Pb定年
Geochemical characteristics and LA-ICP-MS zircon U-Pb dating of the Late Permian monzogranite in Hanggale, Alax Right Banner, Inner Mongolia
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摘要: 杭嘎勒晚二叠世二长花岗岩富碱，贫MgO、TFeO、CaO，轻稀土元素明显富集，具弱负Eu异常，显示I型花岗岩的特点。Nb、Sr 、P、Ti元素亏损，显示出与俯冲有关的侵入岩特征。在R1-R2图解上，大部分样品集中在碰撞前与碰撞后花岗岩区的分界处，以碰撞前为主；在Nb-Y图解上，样品落在火山弧-同碰撞花岗岩区；在Rb-（Y+Nb）图解上，样品点落在火山弧花岗岩区；在Rb-Hf-Ta图解上，样品全部落在弧系统岩石区。主体岩石中锆石Th/U值高，显示出岩浆锆石的特征，稀土元素总量高，重稀土元素富集明显，球粒陨石标准化图解曲线左倾，与岩浆锆石稀土元素配分曲线总体特征趋于一致。LA-ICP-MS锆石U-Pb定年表明其年龄为（253.5±7.9）Ma。杭嘎勒晚二叠世二长花岗岩为碰撞前火山弧花岗岩，研究区在晚二叠世时属于活动大陆边缘的火山弧。
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关键词:
- 地球化学特征 /
- LA-ICP-MS锆石U-Pb定年 /
- 二长花岗岩 /
- 晚二叠世 /
- 杭嘎勒
Abstract: Late Permian monzogranite of Hanggale is characterized by rich alkali metals, poor MgO, TFeO and CaO, enrichment of LREE, and weak negative Eu anomalies, implying an I-type granite. The depletion of Nb, Sr, P, Ti elements shows that such an arc granite has features of intrusive rocks related to subduction. In the R1-R2 diagram, most of the samples are concentrated along the boundary between the pre-collision granite area and the post-collision granite area. In the Nb-Y diagram, the samples fall into the area of the volcanic arc-syncollisional granite. In the Rb-(Y+Nb)diagram, the samples lie in the area of volcanic arc granite. In the Rb-Hf-Ta diagram, the samples all fall into the arc system. High Th/U ratios in zircon of main rocks show characteristics of magmatic zircons; high total REE, heavy REE enrichment and left-oblique curves in the chondrite-normalized diagram are consistent with general characteristics of magmatic zircon distribution. LA-ICP-MS zircon U-Pb dating shows that its age is 253.5±7.9Ma. The Late Permian monzogranite of Hanggale was a pre-collisional volcanic arc granite, and Hanggale area was a volcanic arc that belonged to active continental margin in Late Permian.-
Keywords:
- geochemical characteristics /
- LA-ICP-MS zircon U-Pb dating /
- monzogranite /
- Late Permian /
- Hanggale
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