江西大湖塘矿区九岭花岗闪长岩的成因及其构造意义

发布时间：2018-07-29 15:25

【摘要】：江南造山带东段发育了一系列新元古代花岗岩类侵入体,其中以江西九岭岩体最为显著。锆石U-Pb定年结果表明九岭岩体形成于819Ma。富云母暗色包体在九岭花岗闪长岩体内部广泛出现,典型的岩浆结构及针状磷灰石表明包体为岩浆成因。花岗闪长岩及暗色包体的Mg~#(42~50)均大于玄武质岩石熔融实验结果(大多数40)。暗色包体具有更高的MgO、CaO、Fe_2O_3~T、TiO2及更高的Ni、Co、Sc、V。全岩Sm-Nd同位素结果显示暗色包体的ε_(Nd)(t)为-3.4~-2.1,花岗闪长岩ε_(Nd)(t)为-4.0~-3.5。花岗闪长岩锆石的ε_(Hf)(t)为(-1.4~6.4),多数为正值。Nd-Hf同位素分析表明双桥山群很可能是花岗闪长岩的源区。暗色岩浆包体的普遍发育暗示九岭岩体形成于壳幔岩浆混合过程,除双桥山群外,地幔也贡献了一定的物质。暗色富云包体不是岩石熔融的残渣,而是幔源基性岩浆与富钾下地壳相互作用的产物。结合区域上变质岩、地层学、基性岩研究结果,我们认为扬子板块与华夏板块碰撞的时间很可能在825Ma左右,九岭岩体形成于造山带碰撞挤压向伸展转变的过渡阶段,是壳幔岩浆混合的产物。
[Abstract]:A series of Neoproterozoic granitic intrusions were developed in the eastern part of the Jiangnan orogenic belt. The zircon U-Pb dating results show that the Jiuling rock body was formed in 819 Ma. The mica-rich dark inclusion appears widely in the interior of the Jiuling granodiorite. The typical magmatic structure and acicular apatite indicate that the xenoliths are magmatic. The Mg~# (42 ~ (50) of granodiorite and dark inclusion is larger than that of Black Tortoise (40%). The dark inclusion has a higher MgO _ 2O _ 2O _ 3T _ 2O _ 2 and a higher NiCoC _ 2O _ 2 V _ (V). The Sm-Nd isotopic results of the whole rock show that the 蔚 _ (Nd) (t) of the dark inclusion is -3.4 ~ 2.1and the 蔚 _ (Nd) (t) of the granodiorite is -4.0 ~ 3.5. The 蔚 _ (Hf) (t) of the granodiorite zircon is (-1.4 ~ (6.4), most of which are positive. Nd-Hf isotopic analysis indicates that the Shuangqiaoshan Group is probably the source of the granodiorite. The general development of dark magmatic inclusions suggests that the Jiuling pluton was formed in the process of crust and mantle magma mixing, and the mantle also contributed some material except Shuangqiao Mountain Group. The dark cloud-rich inclusions are not the residue of rock melting, but the product of the interaction between mantle derived basic magma and the lower crust rich in potassium. Combined with the results of regional metamorphic rocks, stratigraphy and basic rock studies, we believe that the time of collision between Yangtze plate and Huaxia plate is probably around 825Ma, and that the Jiuling rock body was formed in the transitional stage of the collision compression to extensional transition of the orogenic belt. It is a mixture of crust and mantle magma.
【作者单位】：造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院;合肥工业大学资源与环境工程学院;国土资源部中央地质勘查基金管理中心;江西省地质矿产勘查开发局九一六大队;
【基金】：合肥工业大学高层次人才引进项目国家自然科学基金项目(41272067) 中国地质调查局整装勘查关键基础地质研究项目(201404025024)联合资助
【分类号】：P588.122

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