长乐—南澳构造带白垩纪“片麻状”浆混杂岩的成岩机制研究——以泉州肖厝岩体为例  

Petrogenetic process of Cretaceous‘gneissic'magma-mixed complex in the Changle-Nan′ao structure zone,Fujian Province:a case study on Xiaocuo intrusion

作　　者：邢光福[1] 李龙明[2] 姜杨[1] 冯艳芳[3] 卢清地 陈志洪[1] 余明刚[1] 段政[1] 

机构地区：[1]南京地质矿产研究所,南京210016 [2]滑铁卢大学地球与环境科学系 [3]中国地质调查局发展研究中心,北京100037 [4]福建省地质调查研究院,福州350011

出　　处：《资源调查与环境》2014年第2期79-94,共16页Resources Survey & Environment

基　　金：国家自然科学基金项目(批准号:41002024;40672041);中国地质调查局地质调查项目(项目编号:1212011120134)联合资助

摘　　要：闽东南长乐—南澳构造带沿线出露大面积白垩纪花岗岩岩基,普遍存在岩浆混合现象,肖厝侵入岩是其中的代表性岩体。野外观察和化学分析表明,肖厝侵入岩由二长花岗岩和辉长闪长岩、以及该两种混合端员岩浆混合形成的闪长质-花岗闪长质-花岗质过渡岩类组成;岩石总体富碱、富LREE和LILE、贫HFSE;A/CNK=0.82~1.05,属准铝质-微过铝质钙碱性系列,部分受流体交代的岩石A/CNK值可升高至1.69;岩浆混合过程中发生了元素的选择性富集/亏损和同位素组成的均一化,(87 Sr/86 Sr)i为0.7055~0.7061,εNd(t)为-1.9^-3.0。锆石年代学研究表明,肖厝侵入岩的岩浆混合开始于约136Ma,于121Ma时初始侵位于下地壳。结合区域地质特征,分析了肖厝侵入岩的成岩机制,提出岩体侵位早于长乐—南澳构造带的变质变形作用,两者不存在成因上的联系;118~100Ma时该构造带曾发生过深层次地壳逆冲推覆,使形成于中—下地壳的韧性剪切带和肖厝侵入岩共同快速上升至地表。There exists a large-scale Cretaceous granitoid batholith which underwent complex magmatic mixings along the Changle-Nan＇ao structure zone in southeastern Fujian Province, in where Xiaocuo intrusion is a typical example. According to field survey and chemical analyses, Xiaocuo intrusion is mainly consisted by monzogranitic and gabbro-dioritic end members, dioritic-granodioritic-granitic transitional rocks formed by their magmatic mixing. These rocks are enriched in alkali, LREE and LILE, and depleted in HFSE, belonging to the meta-aluminous to weak peraluminous calc-alkaline series （A/CNK values= 0.82～1.05, but increasing abruptly tol. 69 due to fluidmetasomatism）. Magma-mixing resulted inselec tive enrichment or depletion of some elements and homogenization of isotopes, the values of （87 Sr/ 86Sr）,andεNd（t） are 0. 7055～0. 7061 and -3. 0～-1. 9, respectively. Zircon LA ICP-MS U-Pb dating shows that Xiaocuo intrusion began its magmatic mixing in ～136Ma and initially emplaced in 121Ma in the lower crust. Combined with the characteristics of regional geology, it is proposed that the mixing and emplacing of this intrusion took place earlier than metamorphism and deformation of the structure zone, so there has no genetic relationship to the latter processes. The Changle-Nan＇ao structure zone occurred thrusting and napping of deep-seated crust during 118～100 Ma, which resulted in rapid rising and out cropping together of both ductile shear belts and Xiaocuo intrusion formed in middle lower crust.

关 键 词：成岩机制 岩浆混合 肖厝侵入岩 白垩纪 长乐-南澳构造带 

分 类 号：P588.121[天文地球—岩石学]