地质学报2017，Vol.91Issue(1)：180-197,18.
浙江外北山铝质A1型花岗岩成因:矿物学、年代学、地球化学及Hf同位素制约
The Petrogenesis of Waibeishan Aluminous A1-type Granite in Zhejiang Province: Constraints from Mineralogy, Zircon U-Pb Dating, Geochemistry and Hf Isotope
摘要
Abstract
Waibeishan alkali-feldspar granite is mainly composed of perthite,albite,quartz,with minor amounts of iron biotite.There developed miarolitic structure,filled by quartz druse and potassium feldspar.In petrochemistry,the rock mass is rich in SiO2,K2 O,FeO,F,while poor in Al2 O3,MgO,CaO,P2 O5.Riching in REE [the variation range of REE is (107.4～330.71) × 10-6],with obviously stronger fractionation of light REE than that of heavy REE and conspicuous negative Eu anomalies.Besides,the "W"-type tetrad effect is present in the granites' REE distribution diagrams.In the aspect of trace element,the rock is rich in Rb,Th,Cs,U,Nb and poor in Sr,Ba,P,Eu and Ti,which displays the typical aluminous A-type granite characteristics.Zircon U-Pb LA-ICP-MS isotopic dating shows that the age of the rock mass is 96.2 ±0.8Ma.Compared with other Southeast Coastal Late Mesozoic A-type granite,Waibeishan alkali-feldspar granite bears significantly higher Nb/Ta and lower Y/Nb,which categorizes it as A1-type granite.Comprehensively,the analysis indicats that the strong extension and fracture activation of early Late Cretaceous lithosphere in the southeast coastal area of China caused partial melting of mafic lower crust in poor water under high temperature and low pressure,which generated granitic magma.The Waibeishan Nb-rich aluminous A-type granite was formed by the metasomatism of F-rich fluid during the fractional crystallization process of the granitic magma.关键词
岩石成因/A型花岗岩/晚白垩世/外北山岩体/浙江Key words
Petrogenesis/A-type granite/Late Cretaceous/Waibeishan pluton/Zhejiang引用本文复制引用
段政,邢光福,余明刚,赵希林,靳国栋..浙江外北山铝质A1型花岗岩成因:矿物学、年代学、地球化学及Hf同位素制约[J].地质学报,2017,91(1):180-197,18.基金项目
本文为中国地质调查局基础地质综合研究项目(编号1212011120134、1212011121136、1212011085446)、国家自然科学基金资助项目(批准号41002024)的成果. （编号1212011120134、1212011121136、1212011085446）
