山东省日照市岚山头片麻状碱性花岗岩的岩石地球化学、年代学和成因研究
Dating and genesis study of the gneissic alkali granite in Lanshantou area,Shandong Province

黄强太 ¹ 夏斌 ¹ 张玉泉 ¹ 蔡周荣 ² 夏连泽 ² 胡西冲 ²

文摘	岚山头片麻状碱性花岗岩是由古生代的沉积岩变质而成,其主量元素具高硅(SiO_2=75% ~77%)、富碱(Na_2O+K_2O=8.38% ~8.60%)、低铝(Al_2O_3=11.72% ~12.05%)、贫钙(CaO=0.09% ~0.53%)等特征,其微量元素特征显示为,富集Rb、Ba、Th、U等大离子亲石元素和Pb,贫Nb、Ta、Zr、Hf、Ti 等高场强元素,以及富集轻稀土(LREE/HREE=6.32~9.86)和铕负异常明显到中等(δ_(Eu)=-0.03~0.51)等,在研究锆石"CL"图像基础上,对具核—幔—壳3层结构的变质复合锆石的幔(第一次变质作用的产物),获得年龄为245 Ma和235 Ma,反映第一次超高压变质时间,也就是它的成岩时间,相当于早-中三叠世,变质复合锆石的新壳,年龄为222~198 Ma,第二次变质时间,也就是退变质作用的时间,相当于晚三叠世,对变质复合锆石老核“继承锆石”定年显示:既含有大量的属于元古代不同年龄段的岩浆碎屑锆石(864 Ma~781 Ma~701 Ma~688 Ma~631 Ma~598 Ma~592 Ma),又含有比较多的属于古生代不同年龄段的岩浆碎屑锆石等(544 Ma~500 Ma~447 Ma~339 Ma~306 Ma),表明其寄主岩的时代不可能为元古代,只能是古生代。
其他语种文摘	The field and indoor results show that the gneissic alkali granite from Lanshantou was converted from paleozoic sedimentary rock.Its chemical composition presents high Si (SiO_2=75% ~77%), alkali-rich (Na_2O+K_2O=8.38% ~8.60%), low Al (Al_2O_3=11.72% ~12.05%), and poor in Ca (CaO=0.09% ~0.53%).It was rich in the large-ion lithophile elements such as Rb, Ba, Th, U, Pb and poor in the high field strength elements such as Nb, Ta, Zr, Hf and Ti.The gneissic alkali granite presents relatively high LREE (LREE/HREE=6.32~9.86) elements and obviously Eu (δ_(Eu)=0.42~0.64) negative abnormality.Based on the base of studying the zircons CL images, The age of mantle of zircon with three-tier structure (core, mantle, shell) is 245 Ma or 235 Ma which reflects the first ultra-high pressure metamorphic time and also is the time of forming of the gneissic alkali granite and equivalent to the Early-Middle Triassic.The age of new shell of metamorphic composite zircon is 222~198 Ma which reflected the second metamorphic time and equivalent to Late Triassic.The U-Pb dating results of old nuclear of metamorphic composite zircon reveal that the ages of magmatic and detrital zircons have both proterozoic era (864 Ma~781 Ma~701 Ma~688 Ma~631 Ma~598 Ma~592 Ma) and paleozoic era (544 Ma~500 Ma~447 Ma~339 Ma~306 Ma).In summary, the ear of protolith of host rock can not be proterozoic and may be palaeozoic.
来源	地质科学 ,2013,48(3):773-786 【核心库】
DOI	10.3969/j.issn.0563-5020.2013.03.015
关键词	片麻状碱性花岗岩 ; 地球化学和锆石年龄 ; 山东日照岚山头
地址	1. 中国科学院广州地球化学研究所, 广州, 510640 2. 中山大学, 广州, 510275
语种	中文
文献类型	研究性论文
ISSN	0563-5020
学科	地质学
基金	国家973计划 ; 国家自然科学青年基金项目
文献收藏号	CSCD:4876406