南阿尔金木纳布拉克地区巴什库尔干岩群变质岩的锆石U-Pb定年和Lu-Hf同位素特征及其地质意义  

The property of the metamorphic strata from Bashkurgan Group in the Munabulake area in South Altyn Tagh,northwestern China:Constraints from zircon U-Pb dating and Lu-Hf isotopic composition

作　　者：解添合 曹玉亭 刘良[2] 马拓 王超[2] 康磊[2] 盖永升 宋里豪 XIE TianHe;CAO YuTing;LIU Liang;MA Tuo;WANG Chao;KANG Lei;GAI YongSheng;SONG LiHao(Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Minerals,College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China)

机构地区：[1]山东省沉积成矿作用与沉积矿产重点实验室,山东科技大学地球科学与工程学院,青岛266590 [2]大陆动力学国家重点实验室,西北大学地质学系,西安710069

出　　处：《岩石学报》2025年第1期198-214,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42172067);山东科技大学“菁英计划”人才项目联合资助.

摘　　要：南阿尔金木纳布拉克地区原划为长城纪巴什库尔干岩群中陆续识别出多类型高压变质岩,以及新元古代和古生代的原岩年龄信息。本文在前人研究的基础上,对木纳布拉克地区巴什库尔干岩群的中-低压浅变质岩进行详细的野外调查,并对三个不同岩组的6个样品进行了岩相学、锆石U-Pb定年和Hf同位素组成研究,以期对区内长城纪地层的构造归属划分提供更多的年代学证据。LA-ICP-MS锆石U-Pb定年测得红柳泉组钾长片麻岩和角闪片岩的原岩形成年龄分别为1459~1577Ma和<1493Ma、贝壳滩组钙质白云母片岩的原岩年龄为<956Ma,均为中-新元古代;此外钙质白云母片岩还获得499Ma的变质年龄,总体反映了以上3个样品具有阿尔金杂岩的锆石年龄信息。这3个样品的核部残留碎屑锆石的ε_(Hf)(t)值与阿尔金杂岩中各类变质岩的ε_(Hf)(t)值范围一致,且具有相似的二阶段模式年龄,代表了其原岩具有相似的物源。因此,综合年代学和Hf同位素组成分析可以推断,以上3个样品所属的地层不应再归为长城纪巴什库尔干岩群,而归到阿尔金杂岩更为合适。LA-ICP-MS锆石U-Pb定年获得扎斯勘赛河组长英质片麻岩、红柳泉组长英质糜棱岩和贝壳滩组斜长角闪岩的原岩年龄介于454~460Ma以及多期变质年龄分别为429~432Ma、400~402Ma和~376Ma。这3个样品的原岩年龄和变质年龄与中阿尔金南缘志留纪中-高压变质岩带内变质岩石原岩和变质年龄具有一致性,且构造位置上均位于木纳布拉克地区西南缘,与阿尔金杂岩以断裂相隔,由此初步推断其与中阿尔金南缘志留纪中-高压变质岩带有关。综上,本文认为南阿尔金木纳布拉克地区原划为长城纪巴什库尔干岩群中南部的贝壳滩组和红柳泉组样品为南阿尔金高压-超高压变质带的西延部分,北部的扎斯勘赛河组和红柳泉组样品为中阿尔金南缘志留纪中压-高压变质作�The Neoproterozoic and Paleozoic components were continuously discovered from the pre-“Bashkurgan Group”in the Munabulake area,South Altyn Tagh.To determine their tectonic attribution,this study conducted detailed field investigations,petrography analyses,zircon U-Pb dating,and Hf isotope analysis on the metamorphic strata of the pre-“Bashkurgan Group”.LA-ICP-MS zircon U-Pb dating revealed protolith ages of 1459~1577 Ma and<1493Ma for the K-feldspar gneiss and amphibole schist in Hongliuquan Formation respectively,as well as<956Ma for the calcareous muscovite schist in Beiketan Formation.All three samples exhibited Neoproterozoic or Mesoproterozoic protolith ages;they also yielded a consistent metamorphic age of~499Ma.Therefore,these samples provide similar age information to that of the Altyn complex.In addition,zircon cores from all three samples displayed comparableε_(Hf)(t)values and t DM2 characteristics to those found in metamorphic rocks from the Altyn complex,indicating similar provenance for their protoliths.Consequently,based on comprehensive age data and Hf isotopic signatures,it can be concluded that the strata including these three samples should be classified under the Altyn complex instead of being assigned to the Bashikuergan Group.The felsic mylonite in the Hongliuquan Formation,amphibolite in the Beiketan Formation,and felsic gneiss in the Zhasikansaihe Formation yielded protolith ages of 454~460 Ma based on zircon U-Pb dating.Additionally,multi-metamorphic ages of approximately 429~432Ma,400~402Ma and~376Ma were obtained.These protolith ages are similar to those of third stage magmatic rocks during the Early Palaeozoic period in the South Altyn Tagh.The protolith ages and metamorphic ages align with those observed in Silurian middle-high pressure metamorphic belt,which suggesting that the formation processes of these three samples are connected to the Silurian MP-HP metamorphic zone within the southern margin of central Altyn Tagh.In summary,this paper considered that the samples from

关 键 词：南阿尔金 木纳布拉克 阿尔金杂岩 锆石U-PB定年 锆石HF同位素 

分 类 号：P588.34[天文地球—岩石学] P597.3[天文地球—地质学]