山东栖霞桃村地区中酸性火山-侵入杂岩岩石地球化学及其成因研究

Geochemical Characteristics and Genesis of Mesozoic Medium and Acid Volcanic-Intrusive Complex in Qixia Taocun,Shandong Province

山东栖霞桃村地区出露中生代中酸性火山-侵入杂岩,对采自桃村地区青山组下段的中酸性火山-侵入岩以进行了岩石学和地球化学研究。桃村地区的中酸性火成岩的地球化学特征为:高钾低钠,高铝低镁;Cr,Co,Ni含量较低,Sr/Y及(La/Yb)N比值很高;微量元素蛛网图显示富集不相容元素K,Rb,Ba和Th,以及不相容元素Ce,Hf和Ti,亏损高场强元素Ta,Nb以及P;轻重稀土元素分馏程度高,具有类似埃达克岩的性质。综合分析其地球化学特征显示,青山组下段中酸性杂岩为增厚的下地壳熔融,这种地壳的增厚作用可能由古太平洋板块俯冲作用引起,而在俯冲作用过程中青山组中酸性杂岩的源岩被俯冲沉积物混染。

There are Mesozoic medium and acid igneous rocks located in Qixia Taocun areas of Shandong province. The authors medium and acid volcanic-intrusive rocks sampled from lower segment of Qingshan Group in Taocun area. The geochemistry characteristic of Taocun medium and acid igneous rocks are. high potassium, low sodium, high-alumina low magnesium. Cr ,Co and Ni content is low and the ratios of Sr/Y and （La/Yb）x is high. Trace element spider diagram shows enrichment of incompatible elements K, Rb, Ba, and Th, as well as Ce,Hf and Ti loss HFS elements of Ta, Nb and P. The light and heavy REE show a high degree fraetionation. The geochemistry feature of this complex is analogous with adakite. Combine the geochemistry feature, the medium and acid complex evolved from melting of thicken lower crust. This thicken affect may arouse by the subduction of paleo-Pacific plate, and mother rock of this complex was contaminated by subducted deposit during this subduction.