胶东三佛山花岗岩的成因：成岩物理化学条件、锆石U-Pb年代学及Sr-Nd同位素约束  

Petrogenesis of Sanfoshan granite, Jiaodong:Diagenetic physical and chemical conditions, zircon U-Pb geochronology and Sr-Nd isotope constraints

作　　者：李增达[1] 于晓飞[2] 王全明 杜泽忠[2] 曹强 师明元 王然 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质调查局发展研究中心,北京100037 [3]D&S International Investment Limited,Hongkong 999077 [4]中国地质矿业有限公司,北京100029 [5]河北省地矿局第六地质大队,石家庄050085 [6]武警黄金第十一支队,拉萨850000

出　　处：《岩石学报》2018年第2期447-468,共22页Acta Petrologica Sinica

基　　金：本文受中国地质调查局整装勘查区找矿预测与技术应用示范项目(DD20160050)资助.致谢中国地质大学(北京)张秀宝老师在野外工作中给予了大力支持和帮助;初稿得到了李胜荣教授的指导;两位匿名审稿人及编辑对本文提出了建设性的意见;研究生赵富远也参与了部分研究工作;在此一并表示感谢.

摘　　要：三佛山花岗岩出露于华北克拉通东缘,其成岩物理化学条件、矿物学特征及准确的侵位年龄仍缺乏系统研究,暗色微粒包体与寄主岩石关系尚不明确,而这些问题的解决对于约束其成因至关重要。本文利用角闪石全Al压力计、黑云母Ti温度计,角闪石-黑云母矿物对温压计及全岩主、微量和锆石U-Pb年龄数据,限定了三佛山花岗岩岩石类型、侵位时代及成岩物理化学条件。此外,测试并收集了大量胶东地区早白垩世侵入体的Sr-Nd及锆石Hf-O同位素数据,综合此次矿物化学研究的新认识,探讨了三佛山花岗岩的岩浆源区和岩石成因。通过角闪石全Al压力计及角闪石-黑云母压力计得到其就位压力2.20kbar;采用角闪石全Al温度计、黑云母Ti温度计,得到的结晶温度为730~680℃。LA-ICP-MS U-Pb测试结果表明三佛山花岗岩侵位于119.6~114.2Ma。根据其地球化学特征,结合区域上年代学、Sr-Nd-Hf同位素研究成果,判定其为I型花岗岩,发育的暗色微粒包体及基性脉岩也应该是同时期的产物,并且局部可能存在岩浆混合作用。花岗岩属富钾-钙碱性花岗岩类(KCG),为挤压造山转变成伸展构造背景下的产物;其较高的初始Sr同位素比值和比较低的ε_(Nd)(t)值,全岩Nd两阶段模式年龄t_(2DM)(2447~2143Ma)等均指示源区主体为重熔的古元古代华南板块中下地壳。Sanfoshan granite is distributed in the eastern margin of North China Craton. There are no systematic investigations of diagenetic conditions, mineralogical characteristics and detailed emplacement age. In addition, the relationship between mafic microgranular enclaves and the host rocks is not clear, which are key to understand the petrogenesis of Sanfoshan granite. Here we present different mineral thermal-barometers, whole-rock elemental geochemistry and zircon U-Pb geochronology data of Sanfoshan granite in order to place constraints on the rock type, emplacement age and diagenetic conditions. Moreover, many Sr-Nd and zircon Hf-O isotopic compositions of Early Cretaceous intrusions in the Jiaodong Peninsula are also tested and collected. Combined with the new mineral chemistry data, we infer its magmatic source and petrogenesis. Our results show that Sanfoshan granite is approximately solidified at 2.20kbar by the barometers of Al-in-hornblende and hornblende-biotite. The solidified temperature calculated by the methods of Al-in-hornblende and biotite Ti thermometer varies in range of 730~680℃. LA-ICP-MS U-Pb dating suggests that these rocks intruded at 119.6~111.4Ma. Taking into account geochemical signatures, emplacement age and isotopic data in this area, it indicates that Sanfoshan granite is I type granite. Co-occurrence of the mafic dike and MMEs should also be the products formed in the same period. Locally there may occur magma mixing. Sanfoshan granite belongs to KCG type granite, suggesting further a tectonic setting transition from compressional to extensional. The higher initial Sr isotopic ratio, lower εNd（t） and t2DM （2447~2143Ma） of these rocks indicate that the main body of magmatic source is the middle-lower crust of South China Block.

关 键 词：三佛山 物理化学条件 年代学 地球化学 花岗岩成因 

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