黑龙江嘉荫与俄罗斯远东Kundur地区黑龙江杂岩锆石U-Pb年代学、Hf同位素组成及其地质意义

Zircon U-Pb ages and Hf isotopic compositions of the Heilongjiang Complex from Jiayin, Heilongjiang Province and Kundur, Russian Far East and their geological implications

本文报道了黑龙江嘉荫和俄罗斯远东Kundur(昆杜尔)地区黑龙江杂岩锆石U-Pb年代学和Hf同位素分析结果,并结合前人研究成果,探讨了黑龙江杂岩的物质组成、形成时代、构造就位时间及物源。黑龙江嘉荫地区黑龙江杂岩中两个石榴石白云母石英片岩(13HYC28-1和13HYC29-1)原岩为流纹岩,其锆石U-Pb年龄分别为185±1Ma和183±1Ma,应代表黑龙江杂岩中存在的中酸性火山岩原岩的形成时代;俄罗斯远东Kundur(昆杜尔)地区石榴石二云母片岩(14RF4-1)和白云母石英片岩(14RF5-1)碎屑锆石年龄频谱主要存在两个年龄区间:183～286Ma和420～525Ma,另外还有少量前寒武纪年龄。这些碎屑锆石年龄组合与佳木斯地块和松嫩-张广才岭地块东缘发育的岩浆事件相对应,揭示其沉积物源应来自于这些火成岩。黑龙江杂岩碎屑锆石年龄数据中早侏罗世的最小峰期年龄(188Ma)代表了黑龙江杂岩原岩成岩时代的下限,结合区内177～165Ma的单矿物变质变形年龄,可以判定黑龙江杂岩的构造就位时间为早侏罗世晚期-中侏罗世。黑龙江杂岩的形成与就位过程揭示了东北亚陆缘早中生代的构造演化历史:中-晚三叠世(240～230Ma),牡丹江洋沿嘉荫-牡丹江断裂裂开并逐渐扩张,早侏罗世期间,古太平洋板块开始向欧亚大陆之下俯冲,受其影响,牡丹江洋俯冲并闭合于早侏罗世晚期-中侏罗世,最终导致佳木斯地块与松嫩-张广才岭地块碰撞拼合以及黑龙江杂岩的构造就位。

This paper presents zirc0n U-Pb dating and Hf isotopic compositions of the Heilongjiang Complex from Jiayin,Heilongjiang Province and Kundur,Russian Far East,with the aim of constraining the material components,provenance,formation and emplacement time of the Heilongjiang Complex by combining with the results of previous researches. Two garnet muscovite quartz schists（ Samples 13 HYC28-1 and 13 HYC29-1） from Jiayin area exhibit rhyolitic protolith characteristics with zircon U-Pb ages of 185± 1 Ma and 183 ± 1 Ma,respectively,i. e. the Early Jurassic. These ages represent the formation time of intermediate-acid volcanic protolith in the Heilongjiang Complex. The garnet two-mica schist（ Sample 14 RF4-1） and muscovite quartz schist（ Sample 14 RF5-1）from Kundur,Russian Far East yield two main ranges of zircon U-Pb ages,i. e.,183 - 286 Ma and 420 - 525 Ma,with less Precambrian ages. These age peaks are in accordance with those of the detrital zircon data that identified from the Heilongjiang Complex in Jiayin,Yilan and Mudanjiang areas. Whats more,all the detrital zircon age peaks from the Heilongjiang Complex correspond to the magmatic events widely occurred in the Jiamusi Massif and the eastern margin of the Songnen-Zhangguangcai Range Massif,revealing that the sediment source of the Heilongjiang Complex should come from the igneous rocks of said regions. The minimum peak age（ 188 Ma） of detrital zircons from the Heilongjiang Complex represents the lower limit of formation time for the Heilongjiang Complex protolith,i. e. the Early Jurassic. Combined with the voluminous reported metamorphic ages of 177 - 165 Ma from single minerals in the study region,it is concluded that the tectonic emplacement of the Heilongjiang Complex took place in the period from late Early Jurassic to Middle Jurassic. The Heilongjiang Complex is an important symbol for figuring out the tectonic evolution of the continental margin of Northeast Asia during the Early Mesozoic. The processes of formation and emplacement of the Heilongjiang Complex indicate that the Mudanjiang Ocean split and gradually expanded along the Jiayin-Mudanjiang fault during the Middle-Late Triassic（ 240 - 230 Ma）.The Mudanjiang Ocean existed between the Jiamusi and Songnen-Zhangguangcai Range massifs during the Middle-Late Triassic to the Early Jurassic. These two massifs have undergone different geological evolution histories in this period. The onset of the Paleo-Pacific plate subduction beneath the Eurasian continent occurred in the Early Jurassic. Under its influence,the Mudanjiang Ocean subducted and closed during the late Early Jurassic to the Middle Jurassic,and finally resulted in the collision of the Jiamusi and SongnenZhangguangcai Range massifs and the tectonic emplacement of the Heilongjiang Complex.