福州闽侯地区长安山闪长岩和流纹岩的成因及地质意义  

Petrogenesis and geological implications of the Changanshan diorite and rhyolite in Minhou area,Fuzhou

作　　者：王力圆[1] 彭向东[1] 黄亮亮[2] 林木森[1] 张文慧[1] WANG LiYuan;PENG XiangDong;HUANG LiangLiang;LIN MuSen;ZHANG WenHui(Zijin Mining College of Fuzhou University,Fuzhou 350116,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]福州大学紫金矿业学院,福州350116 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石学报》2020年第6期1833-1849,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41903007、41873012);福建省科技厅项目(2018J01472);教育厅项目(JT180063)联合资助。

摘　　要：福建沿海广泛发育的白垩纪岩浆岩壳幔相互作用强烈,但对其构造-岩浆事件的细节过程仍存争议。本文对福州闽侯地区福州大学校园内的长安山闪长岩和流纹岩进行了岩石学、同位素年代学和地球化学研究。LA-ICP-MS锆石U-Pb定年结果表明长安山闪长岩年龄为107.2±0.3Ma,形成于早白垩世晚期;流纹岩的形成年龄为98.6Ma左右,属晚白垩世早期的产物。闪长岩和流纹岩的锆石εHf(t)值分别为-2.1^+0.5和-2.7^+1.1。流纹岩具有富硅、富碱、贫钙镁、高分异指数等特点,属弱过铝质岩石。轻稀土富集而重稀土亏损,具有明显的负Eu异常,部分样品具有A型流纹岩的亲缘性特点。流纹岩的岩浆源区来源于软流圈地幔来源熔体和受俯冲影响的富集地幔楔的相互作用的结果,并经历一定程度的分离结晶而成。闪长岩的成因可能为富水的幔源岩浆与受幔源岩浆底侵产生的长英质壳源岩浆混合而成。结合区域构造背景,认为二者为古太平洋板块俯冲体系中弧后伸展环境下的产物。The Cretaceous igneous rocks experienced a strong crust-mantle interaction and widely developed along the coast of Fujian Province,but the details of this tectonic-magmatic event are still controversial.We report detailed petrography,geochronology,and geochemistry of the Changanshan diorite and rhyolite in Fuzhou University,which provided new evidence for the correlation between crust-mantle interaction.Zircon U-Pb geochronology of diorites and rhyolites yield ages of 107.2±0.3Ma and ca 98.6Ma,respectively.It indicated that they were formed in the late Early Cretaceous to early Late Cretaceous.The zirconεHf(t)values in the diorites and rhyolites are-2.1^+0.5 and-2.7^+1.1,respectively.The rhyolites are characterized by rich silicon and alkali,poor calcium and magnesium,high fractionation indexes,and thus belonging to weakly peraluminous rocks.The rhyolites samples show prominent pattern of relative enrichment in LREE,and strong negative Eu anomalies,similar chemically to typical A-type rhyolite.The magma source of the rhyolites was likely produced by interaction of asthenosphere melts with subduction-influenced enriched mantle wedge,and experienced fractional crystallization in the crust.The petrogenesis of diorite may be the mixing of water rich mantle magma and felsic crust magma produced by mantle magma underplating.In combination with the regional tectonic setting,these rocks were probablely formed in continental arc setting related to the subduction of oceanic crust.

关 键 词：流纹岩 闪长岩 岩石成因 HF同位素 福州 

分 类 号：P588.122[天文地球—岩石学] P588.141[天文地球—地质学]