山东郗山碱性杂岩体地球化学特征及其意义

郗山碱性杂岩体与稀土矿床的成因关系密切。通过系统的岩石地球化学研究，全面认识了该区碱性岩浆活动的性质、物质来源及构造背景。经研究发现，SiO2含量为65．08％～69．41％，属于酸性岩，全碱值（K2O＋Na2O）为8．16％～12．92％；在TAS图上，岩石样品全部落在碱性趋势线之上；微量元素的组成以富集大离子亲石元素（LILE）Ba、Sr，亏损高场强元素P、Nb、Ta、Hf为特征；稀土总量（EREE）为189．11×10^-6～2144．52×10^-6轻稀土强烈富集，亏损重稀土，以弱负Eu异常为主。郗山碱性杂岩体岩石属于碱性岩系列，成岩物质来源较深，与EMI富集地幔有关，并受到了地壳物质的混染，形成于引张型构造背景，为造山期后岩浆活动的产物。

The Geochemical Characteristics and Geological Significance of Alkaline Complex in Chishan of Shandong Province

Alkaline complex in Chishan is closely related to the origin of rare earth elements （REE） deposits. A systematic study on geochemical characteristics of the complex was conducted to reveal its features of alkaline magma act!ivity, the mineral sources and tectonic settings. Results have shown that the SiO2 content accounts for 65.08%-69.41%, signifying that the alkaline complex is acidic rock, with total alkaline （K2O＋Na2O） value of 8.16%-12.92%, and all the samples fell above the alkaline trend line in the TAS chart~ As to the composition of trace element, the rock complex enriches in lithophile elements, such as Ba and Sr, but is relatively poor in high field strength elements, such as P, Nb, Ta and Hf; Total values of rare earth elements （EREE） are （189.11-2 144.52） ）K 10-6, where LREE is strongly enriched while HREE is deficient, dominated by a weak negative Eu anomaly. Based on the study and analysis, this paper suggests that the Chishan alkaline complex was formed in extensional tectonic background and was a post-orogenic magmatic product. Belonging to alkaline rock series, its mineral source is deep-seated magma, relating to EMI enriched mantle and being contaminated by crustal materials.