内蒙古索伦地区上二叠统林西组碎屑岩地球化学特征及其对物源的指示意义

内蒙古索伦地区上二叠统林西组沉积物源受控于晚古生代古亚洲洋的闭合事件。本文通过分析碎屑岩元素地球化学特征，对林西组母岩类型和古构造环境进行了探讨。常量元素分布特征表明，林西组早期属于风化程度较弱的第一次旋回沉积物，后期属于中等风化的第一次旋回沉积或再旋回沉积物，母岩类型以火成岩为主；微量元素和稀土元素分布特征表明，林西组母岩沉积环境为大陆岛弧背景下切割的岩浆弧，以上地壳碱性-中性火成岩为主，伴有钙质-泥质沉积岩，（Gd/Yb）_n表明早期沉积母岩为太古宙碱性火成岩。综合分析表明，林西组沉积同时接受南侧华北板块北缘和北侧苏尼特左旗-锡林浩特-西乌旗南岩浆弧的共同物源供给，早期沉积有华北板块北缘太古宙基底母岩的参与。

Geochemical Characteristics and Implication for Provenance of Upper Permian Linxi Formation Clastic Rocks in Solonker Area,Inner Mongolia

The provenanceof the Linxi Formation in Solonker area was greatly influenced by the closure of the Paleo-Asian Ocean occurred in the Late Paleozoic.A comprehensive analysis of the element geochemical characteristics of the clastic rock has been done to study the source rock types and
the tectonic setting of the Linxi Formation in the Solonker area.The maj or elements compositions indicated that the early sediments was of low weathering degree from the first depositional cycle and the latter sediments was of moderate weathering degree from the first depositional cycle or recycled deposition,and the igneous rock was the primary source rock.The trace elements and rare earth elements characteristics demonstrated a dissected magmatic arc dominated tectonic setting for the source rock of Linxi Formation.The intermediate and alkaline igneous rocks from the upper crust were the primary source rocks,with lower content of sedimentary rock.The indicator (Gd/Yb)n showed the early sediments was from the Archean alkaline igneous rocks.Comprehensive analysis showed that the provenances of the Linxi Formation were j ointly derived from the north margin of the North China plate in the south and the Sonid Zuoqi-Xilinhot-sourthern Xiwuqi magma arc in the north.