赣东北婺源—德兴地区新元古代浅变质火山岩的地球化学和锆石U-Pb年龄  

LA-ICPMS zircon U-Pb ages and geochemistry of Neoproterozoic low-grade metavolcanic rocks in Wuyuan-Dexing area of northeastern Jianxi Province.

作　　者：刘树文[1] 杨朋涛[1] 王宗起[2] 罗平 王永庆 罗国辉 王伟[1] 郭博然[1] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871 [2]中国地质科学院矿产资源研究所,北京100037 [3]赣东北地质大队,上饶334008

出　　处：《岩石学报》2013年第2期581-593,共13页Acta Petrologica Sinica

基　　金：国家地调局项目(201111020)

摘　　要：赣东北婺源——德兴地区新元古代地层中浅变质火山岩主要由变质玄武岩、英安岩和流纹岩组成。全岩地球化学分析表明浅变质玄武岩具有拉斑玄武岩的地球化学特征,起源于尖晶石辉橄岩低度部分熔融,英安岩岩浆起源于壳源杂砂岩部分熔融,流纹岩可能为英安质岩浆结晶分异的产物。LA-ICP-MS锆石U-Pb同位素定年揭示婺源浅变质英安岩形成于861±8Ma,德兴张村西浅变质流纹岩形成于860±3Ma,铜厂铜矿矿区凝灰质板岩形成于860±6Ma,均为早新元古代Tonian期。同时这些定年样品中保存了2.8～2.5Ga、2.0～1.7Ga和～1.0Ga的继承或捕获锆石记录。结合浅变质玄武岩和英安质火山岩的地球化学特征和成因,这套岩石最有可能形成于新元古代早期安第斯型活动大陆边缘弧后盆地构造背景。Low-grade metamorphosed volcanic rocks consist mainly of metamorphic basalt, dacite and rhyolite in the Wuyuan to Dexing region of the northeastern Jiangxi Province. Whole-rock geochemical analyses reveal that the metabasalt has chemical features of the tholeiite, and the basaltic magma originated from low-degreed partial melting of a spinel lhezolite in disturbed deleted mantle. However, the dacitic magma was derived from a partial melting of a meta-greywacke, and the rhyolite was produced by the fractionation of the dacitic magma. LA-ICP-MS zircon U-Pb isotope dating indicates low-grade meta-dacite from the Wuyuan area was formed at 861±8Ma, and meta-rhyolite and tuffaceous slate from the Dexing area at 860±3Ma and 860±6Ma, respectively, which indicate that these metamorphic volcanic rocks erupted at Neoproterozoic Tonian era. Meanwhile, these samples also preserved some signatures of Neoarchean （2.8～2.5Ga）, Middle-Late Paleoproterozoic （2.0～1.7Ga） and Mesoproterozoic （～1.0 Ga） inherited and/or captured zircon ages. Integrated the whole-rock geochemistry, petrogenesis and zircon ages, we suggest that these metamorphic volcanic rocks formed under an Early Neoproterozoic tectonic background of back-arc basin in Andes-type actively continental margin.

关 键 词：浅变质火山 岩石地球化学 LA-ICP-MS锆石U-PB年龄 岩石成因 构造背景 赣东北地区 

分 类 号：P597[天文地球—地球化学]