CAJ | 학술논문

永庆林场一十八站花岗岩体位于大兴安岭东北部的额尔古纳地块，主要由花岗闪长岩组成，二长花岗岩和石英闪长岩在岩体中零星出露。岩体中锆石呈自形晶，发育振荡生长环带，显示高Th／U比值（0．23～1．35），表明锆石岩浆成因。锆石的LA—ICP—MSU-Pb定年结果为443．5～447．5Ma，属于晚奥陶世岩浆活动的产物，而非前人所划分为的新元古代。锆石的Hf同位素研究显示，2件花岗岩样品的εHf（t）值分别为一1．1～＋2．4和一0．4～＋3．6，二阶段模式年龄为1．2～1．5Ga。结合额尔古纳地块已有的早古生代和中生代花岗岩锆石Hf同位素资料，笔者认为额尔古纳地块不同时代的花岗岩具有相似的模式年龄，其地壳增生的时间主要发生在中一新元古代。目前已有研究表明，兴安地块地壳增生发生在新元古代一显生宙，暗示它们具有不同的地壳演化过程。
영경림장일십팔참화강암체위우대흥안령동북부적액이고납지괴，주요유화강섬장암조성，이장화강암화석영섬장암재암체중령성출로。암체중고석정자형정，발육진탕생장배대，현시고Th／U비치（0．23～1．35），표명고석암장성인。고석적LA—ICP—MSU-Pb정년결과위443．5～447．5Ma，속우만오도세암장활동적산물，이비전인소화분위적신원고대。고석적Hf동위소연구현시，2건화강암양품적εHf（t）치분별위일1．1～＋2．4화일0．4～＋3．6，이계단모식년령위1．2～1．5Ga。결합액이고납지괴이유적조고생대화중생대화강암고석Hf동위소자료，필자인위액이고납지괴불동시대적화강암구유상사적모식년령，기지각증생적시간주요발생재중일신원고대。목전이유연구표명，흥안지괴지각증생발생재신원고대일현생주，암시타문구유불동적지각연화과정。
The Yongqinglinchang-Shibazhan granites are located in the Eerguna block in the northeastern Da Hinggan Mountains, and mainly consist of granodiorite, with minor adamellite and quartz diorite. The zircon grains separated from the granodiorite sample in the Yongqinglinchang-Shibazhan granites show generally euhe-dral form with fine oscillatory zoning on their CL images, and high Th/U ratios(0.23-1.35), which exhibit the fea- tures of magmatic zircons. LA-ICP-MS zircon U-Pb dating reveals that the Yongqinglinchang-Shibazhan granites emplaced at 443.5-447.5 Ma, belonging to the products of upper Ordovician magmatism, not to the Neoprotero-zoic recognized and categorized by predecessors. Zircon Hf isotope characteristics indicate that two granotoid samples have zircon sill(t) values ranging from-1.1 to +2.4 and -0.4 to +3.6, with model ages from 1.2 Ga to 1.5 Ga. Combined with previous zircon Hf isotope data obtained from Early Paleozoic and Mesozoic granites in the Eerguna block, the authors hold that the granites have the similar model ages although they were formed in differ- ent geological ages. Meanwhile it indicates that the crustal accretion event of Eerguna block occurred mainly in Middle and Neo-Proterozoic period. Previous studies indicate that the Xing' an block accreted in Neoproterozo-ic-Phanerozoic. It suggests that they have the different tectonic natures and evolvement history.