鲁西费县中生代玄武岩及幔源捕掳晶的矿物化学:对岩石圈地幔性质的制约  

Mesozoic Basalt and Mineral Chemistry of the Mantle-Derived Xenocrysts in Feixian, Western Shandong, China: Constraints on Nature of Mesozoic Lithospheric Mantle

作　　者：裴福萍[1] 许文良[1] 王清海[1] 王冬艳[1] 林景仟[1] 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《高校地质学报》2004年第1期88-97,共10页Geological Journal of China Universities

基　　金：国家自然科学基金 (编号 :40 172 0 3 0 ;40 13 3 0 2 0 );高校博士学科点基金 (编号 :2 0 0 10 183 0 0 7)资助项目

摘　　要：鲁西费县中生代玄武岩形成于 119Ma ,为碱性玄武岩。该玄武岩中含有丰富的幔源橄榄石、斜方辉石和单斜辉石捕掳晶。橄榄石捕掳晶具有环状裂纹 ,其Mg# 值介于 90 .0～ 93.0之间 ,平均为 91.5;斜方辉石和单斜辉石捕掳晶具有特征的反应边 ,斜方辉石的Mg# 值介于 88.0～ 93.5之间 ,平均为 90 .4 ;单斜辉石的Mg# 值介于 86 .0～ 91.7之间 ,平均为 88.4。捕掳晶的矿物化学类似于中国东部新生代玄武岩中地幔橄榄岩的矿物成分特征 ,这暗示捕掳晶应为寄主岩浆上升过程中捕获的地幔橄榄岩物质 ,并且反映了新增生的岩石圈地幔特征。费县玄武岩的岩石地球化学显示其具有地幔原生岩浆的特征 ,其高Isr、低 εNd(t)和亏损高场强元素等特征应与断离的俯冲板片 (苏鲁造山带中的榴辉岩 )Mesozoic basalt in Feixian, western Shandong, is composed of alkaline basalt with K-Ar age of 119 Ma. Abundant mantle-derived xenocrysts such as olivine, orthopyroxene and clinopyroxene can be found in the basalt. The circle cracks occur in the olivine xenocrysts. The Mg~# values of the olivine xenocrysts range from 90.0 to 93.0 (ave. 91.5). The typical reaction rims can be found between pyroxene xenocrysts and host rock. The Mg~# values of the orthopyroxenes and clinopyroxenes are 88.0～93.5 (ave.90.4) and 86.0～91.7 (ave.88.4), respectively. The mineral compositions of the xenocrysts are similar to those of the mantle-derived peridotites in Cenozoic basalts of eastern China, which implies that they should be the fragments of the mantle peridotite carried by the host magma and represent a new accreted lithospheric mantle. Petro-geochemical data of Feixian basalt indicate that this is characteristic of mantle-derived primary magma. High Isr, low ε_(Nd(t)) and depletion of high field strength elements (HFSE) in the basalt could be related to the mixed melting of the broken-off subducted slab (the eclogites in the Su—Lu orogen) and the material from the asthenosphere.

关 键 词：鲁西 中生代 玄武岩 捕虏晶 岩石圈地幔 

分 类 号：P588[天文地球—岩石学] P575[天文地球—地质学]