川西里伍岩群中石榴子石矿物化学特征及其对变质温度的限定

    Mineral Chemical Characteristics and Constraint on Metamorphic Temperature of Garnet from the Liwu Group, Western Sichuan, China

    • 摘要: 这是一篇地球科学领域的论文。为揭示江浪穹隆核部里伍岩群中石榴子石的矿物化学特征及其变质温度,本文选择了发育在不同位置的石榴子石矿物开展了主量、微量和稀土元素分析测试。结果表明,江浪穹隆片岩中的石榴子石端元组成主要为铁铝榴石(Alm),利用ICP-MS(平均含量85.82%)和LA-ICP-MS(平均含量83.51%)获得的铁铝榴石(Alm)含量在误差范围内基本一致;稀土元素(REE)总量较高,分配模式呈现明显的轻稀土亏损(LREE)、重稀土(HREE)富集的左倾分配模式,Eu异常不明显,负Ce异常显著;相对富集高场强元素(如U、Ta、Hf),亏损大离子亲石元素(如K、Sr、Ba)。另外,江浪穹隆片岩中利用石榴子石矿物获得的变质温度为512~583 ℃,形成的变质压力较低,且变质温度与至新火山花岗岩的距离呈负相关关系。综上,江浪穹隆经历了高绿片岩相的巴罗式变质作用。

       

      Abstract: This is an article in the field of earth sciences. To reveal the mineral chemistry characteristics and metamorphic temperature of garnet in the Liwu Group due to core of Jianglang dome, the major, trace and rare earth elements of garnet were analyzed at different locations in this paper. The results show that the major-element composition of garnet in schist from the Jianglang dome is mainly Alm. ICP-MS (average content 85.82%) and LA-ICP-MS (average content 83.51%) is basically consistent within the error range of the Alm content obtained.The total content of rare earth elements (REE) is high, and show obvious LREE-depleted and HREE-enriched left-declined REE distribution patterns, with unobvious Eu anomalies and negative Ce anomalies, Enriched in large ionic strength elements (U, Ta, Hf)and depleted high field lithophile elements (K, Sr, Ba). In addition, the formation temperature of garnet in schist from the Jianglang dome is 512~583 ℃, and the formed metamorphic pressure is relatively low. It is a negative correlation between the metamorphic temperature and the distance to the Xinhuoshan granite. In conclusion, the Jianglang dome experienced “Barrovian-type” metamorphism of high greenschist facies.

       

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