桂东北里松花岗岩中暗色包体的岩浆混合成因  

Magma mixing origin of the mafic enclaves in Lisong Granite,NE Guangxi,western Nanling Mountains

作　　者：朱金初[1] 张佩华[1] 谢才富[1] 张辉[2] 杨策[1] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室,江苏南京210093 [2]中国科学院地球化学研究所,贵州贵阳550002

出　　处：《地球化学》2006年第5期506-516,共11页Geochimica

基　　金：国家自然科学基金(40373014;40132010;40073008)

摘　　要：在桂东北姑婆山地区的里松花岗岩中,暗色包体广泛分布,包体的形貌、结构构造和矿物学特征表明,它们是岩浆快速冷凝结晶产物;主元素和微量元素组成说明它们属钾玄岩系列,其源岩具OIB型微量元素特征;包体与寄主花岗岩中锆石U-Pb年龄的相同性,排除了来源于深部固体岩石熔融残留体或浅部围岩捕虏体的可能性,而两种岩石化学成分、岩石结构暗色包体和寄主花岗岩在岩石结构和全岩Sr-Nd同位素组成方面的明显差别性,又排除了同源包体或析离体、堆积体的可能性。里松花岗岩在很多地质-地球化学特征上都介于里松暗色包体和姑婆山主体花岗岩之间,里松暗色包体的总体特征显示了岩浆混合成因,是里松暗色包体岩浆与姑婆山主体花岗岩岩浆发生混合时不完全混合的残留物。The mafic enclaves are widespread in the Lisong granite, NE Guangxi, western Nanling Mountains. Their morphological, structural, textural and mineralogical characteristics indicate that these enclaves are products of rapid quenching and crystallization of the intermediate-basic magmatic melts. Their compositions of rock-forming elements and trace elements demonstrate that they belong to the shoshonitic series. Their parent rocks possess OIB-type trace element characteristics. Their synchronous zircon U-Pb age with the Lisong hosting granite excludes the possibility of restite from the melted metamorphic rocks at greater depth and xenolith from the country rocks at shallower depth. The obvious difference in chemistry, petrographic texture and whole rock Sr-Nd compositions excludes the possibility of co-magmatic segregations and/or cumulate of the earlier stage crystallization. The Lisong granite is in many geologo-geochemical aspects intermediate between the Lisong enclaves and the synchronous Guposhan major boby granite. The integrated geologo-geochemical features of the mafic enclaves in Lisong granite demonstrate a magma mixing origin. They are remnants of incomplete mingling from the marie magma.

关 键 词：花岗岩 暗色包体 岩浆混合 岩石成因论 里松 南岭 

分 类 号：P597[天文地球—地球化学] P581[天文地球—地质学]