福建紫金山复式岩体的地球化学特征和成因  

Petrogenesis and geochemical characteristics of the Zijinshan granitic complex from Fujian Province,South China

作　　者：李斌[1] 赵葵东[1,2] 张倩[3] 徐耀明[2] 朱志勇[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,地球科学与工程学院,南京210093 [2]中国地质大学地质过程与矿产资源国家重点实验室,资源学院和紧缺矿产资源勘查协同创新中心,武汉430074 [3]江苏华东基础地质勘查有限公司,江苏省有色金属华东地质勘查局,南京210007

出　　处：《岩石学报》2015年第3期811-828,共18页Acta Petrologica Sinica

基　　金：国家科技部973项目(2012CB416706);国家自然科学基金项目(U1405232;41422203)联合资助

摘　　要：紫金山复式岩体位于福建紫金山大型-超大型铜金矿田中,包含迳美、五龙寺以及金龙桥三个岩体,其形成年龄分别为164Ma、163Ma及155Ma,为中晚侏罗世时期岩浆活动的产物。岩石地球化学研究表明,其属过铝质花岗岩,稀土元素总量偏低,属LREE富集型。微量元素Ba、Nb、La、Ce、Sr、P、Ti都表现出较明显的负异常,不同岩体表现出的负异常程度不同;而Rb、Th、U、Pb则呈现正异常。紫金山复式杂岩的锶同位素初始比值ISr的变化范围较大,而εNd(t)变化范围在-10.3^-6.8之间,tDM2值为1.5~1.78Ga。锆石的Hf同位素εHf(t=155Ma)为-19.0^-7.1,两阶段Hf模式年龄(tDM2)为1.62~2.37Ga。紫金山复式花岗岩体的形成可能与大规模的上地壳(包括华夏元古代正变质岩与副变质岩)的部分熔融有关,并经历印支期花岗岩的同化混染。紫金山复式岩体属低温S型花岗岩,主要发生长石、褐帘石和磷灰石的分离结晶作用,其形成的构造环境可能为受古太平洋板块俯冲所导致的活动大陆边缘环境。The Zijinshan granitic complex,including Jingmei,Wulongsi and Jinlongqiao plutons,located in the giant Zijinshan CuAu ore field in Fujian Province,was emplaced in the Late Jurassic（ 164 ~ 155Ma）. This complex is composed of peraluminous granites,which are characterized by low REE,depleted in Ba,Nb,La,Ce,Sr,P,Ti,and enriched in Rb,Th,U,Pb. This complex shows various initial87 Sr /86 Sr ratios and negative εNd（ t） values（- 10. 3 to- 6. 8） of the whole rocks,and negative εHf（ t）values（- 19. 0 to- 7. 1） of the zircons. Interpretation of the elemental and isotopic data suggests that the Zijinshan granitic complex was most likely derived from partial melting of the crust materials including Proterozoic orthometamorphic and parametamorphic rocks,and suffered assimilation and contamination by Indosinian granitoids. The initial magmas may have generated the Zijinshan complex through fractionation of feldspar,allanite,and apatite at a relatively low magmatic temperature. We suggest that a continental arc related to the paleo-Pacific plate subduction was the most likely geodynamic force for formation of the Jurassic Zijinshan complex in the Cathaysia Block.

关 键 词：紫金山复式岩体 地球化学 SR-ND-HF同位素 岩石成因 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]