朝鲜半岛冠帽地块的基底属性：来自银德洞变质侵入杂岩的锆石U-Pb年代学和岩石地球化学证据

Basement affinity of the Kwanmo Massif, Korean Peninsula: Evidence from zircon U-Pb geochronology and petro-geochemistry of the Undokdong meta-intrusive complex

地体基底建造的甄别和表征是联结华北克拉通与朝鲜半岛早期演化历史的基本纽带。针对朝鲜半岛前寒武纪基底建造研究方面的薄弱环节,本文表征了冠帽地块清津地区银德洞出露的变质深成侵入杂岩。3个代表性样品的SIMS锆石U-Pb定年结果显示,早期中性片麻岩记录的岩浆侵入年龄为约2.53 Ga,晚期钾长花岗质片麻岩记录的岩浆侵入年龄为约2.51 Ga,表明银德洞变质杂岩形成于新太古代晚期。参考变质杂岩的岩石地球化学特征,其原岩组成可能包括石英闪长岩和钾长花岗岩,大体上可与全球典型的岩浆型紫苏花岗岩系列相类比。结合3个样品变化较大的锆石εH f(t)值(-1.7^+10.5),我们推测银德洞变质侵入杂岩可能形成于玄武质下地壳岩石的部分熔融及其后的结晶分异作用,代表了活动大陆边缘岩浆弧环境下的典型产物。银德洞变质杂岩归属于新太古代岩浆弧根部岩浆岩建造的研究认识,不仅为判定冠帽地块与华北克拉通东部的吉南和龙地块以及辽北清原地块之间的亲缘性提供了岩石学证据,而且暗示这些地块在新太古代共同处在一个类似于安第斯活动大陆边缘的构造环境。

Recognizing and characterizing the basement affinity of terranes presents a critical task for establishing the link between the Korean Peninsula（ KP） and the North China Craton（ NCC） since Archean on.This study aims to bridge the gap in the characterization of the Precambrian basement rocks in the KP by documenting the Undokdong meta-intrusive complex in the Chongjin region,the Kwanmo Massif.SIMS zircon U-Pb dating on three representative samples from the complex yielded magmatic crystallization ages from 2.53 to 2.51 Ga.In terms of their petrological and geochemical traits,the protoliths of these metamorphic rocks can be recognized as quartz diorite and potassic granite, and compare well with the classic magmatic charnockite suites in the world.Synthesizing these features with the variable zircon εH f（ t） values from-1.7 to ＋ 10.5 in the three samples,we infer that the Undokdong meta-intrusive complex might originate from the high-T and CO2-rich fluid-fluxed partial melting of basaltic lower crust and subsequent fractionation,thus representing typical products of magmatic arcs on an active continental margin.Given a possible tectonic link with a Neoarchean arc root,these rocks could present a spatial reference for defining the consistency in tectonic affinity between the Kwanmo Massif and the Helong/Qingyuan terrains in the eastern NCC,thus leading to the characterization of an Andean-type active continental margin across these terrains during Neoarchean.