宿州八山花岗岩地球化学特征及地质意义

Geochemical Characteristics and Geological Significance of Bashan Granite in Suzhou

为探讨宿州八山花岗岩的岩石类型及构造演化背景,对宿州八山花岗岩体进行地球化学研究。结果表明,八山花岗岩具有高硅(SiO_(2)含量为74.58%~76.01%)、富铝(Al_(2)O_(3)含量为13.3%~13.93%)、富碱(Na_(2)O+K_(2)O含量为8.29%~8.62%)和低钛(TiO_(2)含量为0.07%~0.08%)的特征,属于高钾钙碱性铝质岩石。八山花岗岩元素Rb、Hf、Th及轻稀土元素富集,元素Ba、Nb、Sr及重稀土元素亏损,元素Eu强烈负异常。八山花岗岩微量元素Ga含量为21.3×10^(-6)~22.8×10^(-6),10000×Ga/Al值大于2.6,Rb/Nb值为6.29~6.8,Nb/Ta值为13.18~14.22,其岩石成因类型为A型花岗岩,源自地壳变质杂砂岩的部分熔融。八山花岗岩体形成于造山期后的伸展构造环境。

In order to study the rock type and tectonic evolution background of Bashan granite in Suzhou,the geochemistry of it are studied.The results show that the Bashan granite is characterized by high silicon(SiO_(2) content is 74.58%~76.01%),rich aluminum(Al_(2)O_(3) content is 13.3%~13.93%),rich alkali(Na_(2)O+K_(2)O content is 8.29%~8.62%),low titanium(TiO_(2) content is 0.07%~0.08%),and belongs to high potassium calc alkaline aluminum rock.Bashan granite is rich in Rb,Hf and Th,and deficient in Ba,Nb and Sr and heavy rare earth elements.Element Eu is strongly negative anomaly.The trace element Ga content of Bashan granite is 21.3×10^(-6)~22.8×10^(-6),and 10000×Ga/Al value is more than 2.6.Rb/Nb value is 6.29~6.8,and Nb/Ta value is 13.18~14.22.The genetic type of the rock is A-type granite,which is derived from partial melting of metamorphic greywacke in the crust.The Bashan granite was formed in the post orogenic extensional tectonic environment.