朱晓青, 侯方辉, 刘洪滨, 郭兴伟, 孙天本, 秦亚超, 安郁辉, 李凤春. 山东即墨马山粗面英安岩年代学与地球化学特征及其地质意义[J]. 海洋地质与第四纪地质, 2021, 41(6): 138-150. DOI: 10.16562/j.cnki.0256-1492.2021011801
引用本文: 朱晓青, 侯方辉, 刘洪滨, 郭兴伟, 孙天本, 秦亚超, 安郁辉, 李凤春. 山东即墨马山粗面英安岩年代学与地球化学特征及其地质意义[J]. 海洋地质与第四纪地质, 2021, 41(6): 138-150. DOI: 10.16562/j.cnki.0256-1492.2021011801
ZHU Xiaoqing, HOU Fanghui, LIU Hongbin, GUO Xingwei, SUN Tianben, QIN Yachao, AN Yuhui, LI Fengchun. Geochronology and geochemistry of Mashan trachydacite, JiMo District, Shandong Province and their geological implications[J]. Marine Geology & Quaternary Geology, 2021, 41(6): 138-150. DOI: 10.16562/j.cnki.0256-1492.2021011801
Citation: ZHU Xiaoqing, HOU Fanghui, LIU Hongbin, GUO Xingwei, SUN Tianben, QIN Yachao, AN Yuhui, LI Fengchun. Geochronology and geochemistry of Mashan trachydacite, JiMo District, Shandong Province and their geological implications[J]. Marine Geology & Quaternary Geology, 2021, 41(6): 138-150. DOI: 10.16562/j.cnki.0256-1492.2021011801

山东即墨马山粗面英安岩年代学与地球化学特征及其地质意义

Geochronology and geochemistry of Mashan trachydacite, JiMo District, Shandong Province and their geological implications

  • 摘要: 山东即墨马山地区出露罕见的发育柱状节理的中酸性火山岩,对于其年代学及形成的大地构造背景鲜有讨论。岩石薄片与主量元素分析结果证明马山柱状节理火山岩属于粗面英安岩。利用LA-ICP-MS对马山柱状节理火山岩中的锆石进行U-Pb测年,确定其形成时间为113.2±1.3 Ma,属于早白垩世晚期。原位Lu-Hf分析获得锆石εHf(t)值范围为−19.5~−0.4,对应的二阶段模式年龄范围约为1.97~3.26 Ga,暗示其源区岩浆成生于古老地壳的熔融。马山粗面英安岩具有SiO2和Al2O3含量较高,MgO含量低及富含碱的主量元素的特征。其稀土元素总量较低,配分模式呈轻稀土富集、重稀土亏损的右倾模式,Eu轻微负异常,Sr含量高而Y和Yb含量低。马山粗面英安岩的主微量元素显示其具有埃达克岩特征,推测其来源岩浆可能形成于燕山期华北东部区域性地壳增厚后下部老地壳的熔融。

     

    Abstract: Intermediate-acid volcanic rocks with columnar joints expose in the Mashan area, Jimo, Shandong Province. The geochronology and tectonic setting of the volcanic rocks had been rarely studied. The petrographic characteristics and major element results show that the volcanic rocks at Mashan are trachydacite. Zircon LA-ICP-MS U-Pb dating of the trachydacite shows that the volcanic rocks erupted at 113.2 ± 1.3 Ma, that is, in the late Early Cretaceous. In-situ Lu-Hf analysis suggests that the zircon εHf (t) values range from −19.5 to −0.4 and two-stage model ages of zircons range from 1.97 Ga to 3.26 Ga, indicating that the magma was sourced from the melting of ancient crust. The Mashan trachyandesite is characterized by high content of SiO2 and Al2O3, low content of MgO, enriched Na2O and K2O. Moreover, all samples are featured by lower total contents of rare earth elements, enriched light rare earth elements, deficit heavy rare earth elements, slightly negative Eu anomaly, high Sr content, low Y and Yb contents. The major and trace elements of the trachydacite in Mashan are quite similar to adakite, and the adakitic magma could have been formed by the melting of the lower old crust after the regional crust thickening in Eastern Norch China Block during the Yanshanian.

     

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