沂沭断裂带中生代青山群火山岩地球化学特征及其岩石成因  

Geochemistry and petrogenesis of the Mesozoic volcanic rocks from Qingshan Group in the Yishu fault zone

作　　者：张永清 凌文黎[2] 张军波[2] 段瑞春[3] 任邦方 杨红梅[3] 

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]中国地质大学(武汉)地球科学学院,湖北武汉430074 [3]中国地质调查局武汉地质调查中心,湖北武汉430074

出　　处：《地学前缘》2017年第6期110-118,共9页Earth Science Frontiers

基　　金：国家自然科学基金委员会创新研究群体科学基金项目(40521001)

摘　　要：以沂沭断裂带安丘地区中生代青山群火山岩为研究对象,在进行系统的元素-同位素分析的基础上,探讨其岩浆源区和岩石成因。安丘火山岩SiO2含量变化于56.5%~65.8%,主要为高钾钙碱性系列岩石,岩石组合为英安岩和粗面安山岩;安丘火山岩富集大离子亲石元素和轻稀土元素,亏损高场强元素,显示富集但变化范围较大的Sr-Nd同位素组成((^(87)Sr/^(86)Sr)t=0.708 7~0.710 7,εNd(t)=-13.7^-5.93)。综合分析表明,安丘火山岩为大陆下地壳物质经拆沉作用于地幔环境中发生部分熔融作用,与上地幔岩石发生交代作用后进入地表形成,且其源区中可能有软流圈物质的加入。In this paper, we report the elemental-isotopic geochemistry for the Mesozoic volcanic rocks from Qingshan Group in the Anqiu area in the Yishu fault zone, with the aim to constrain the magma source and to elucidate the petrogenesis. In lithology, these volcanic rocks are dominantly featured by calc-alkaline series. The Anqiu volcanic rocks comprise dacite and trachyandesite with the SiO2 content varied from 56. 5%- 65. 8%; All the Anqiu volcanic rocks are characterized by the enrichment in LILE, and depletion in HFSE. The volcanic rocks have enriched but varied Sr-Nd isotopic compositions with （87 Sr/86 Sr）t ratios of 0. 7087 - 0. 7107 and εNd （t） values of -13. 7 -5. 93. The petrogenesis accordingly is explained by the metasomatism of melts by partial melting of delaminated lower crustal rocks with surrounding mantle rocks of lithosphere, and the melts from the asthenosperic mantle played an important role to the formation of magmas parental to the Anqiu volcanic rocks.

关 键 词：沂沭断裂带 中生代 青山群火山岩 地球化学特征 岩石成因 

分 类 号：P588.14[天文地球—岩石学] P597[天文地球—地质学]