CAJ | 학술논문

纳赤台群是东昆仑造山带中段出露的构造混杂岩的重要组成部分,对纳赤台群碎屑岩段的地层时代及物质来源进行限定,可以为恢复和反演东昆仑早古生代的构造格局提供依据.前人多认为纳赤台群的地层时代为奥陶纪或奥陶纪—志留纪,但是志留纪、二叠纪甚至新生代的观点也同时存在.通过对纳赤台群碎屑岩段进行碎屑锆石年龄研究,得到最年轻的锆石年龄538±10Ma,结合侵入其中的英云闪长岩体的年龄为427.7Ma,将纳赤台群碎屑岩的沉积时代限定于538~427Ma之间,另外由于纳赤台群特殊的演化意义,结合沙松乌拉组和赛什腾组的地层时代,将纳赤台群碎屑岩的地层时代确定为奥陶纪,并认为有可能延伸至早志留世.得到的碎屑锆石年龄谱显示约2450Ma、约1100Ma、约980Ma、约810Ma、约650Ma五个明显峰值,结合纳赤台群碎屑岩近源堆积的特征,将得到的锆石年龄与东昆仑及邻区出露的老地层和岩体时代进行比对,推测白沙河岩组、小庙群、万宝沟群及新元古代早期在东昆仑地区形成的中酸性岩体为其可能物源.将得到的锆石年龄与各期重大构造-岩浆事件在昆仑造山带留下的地质记录进行对比,推测认为,纳赤台群碎屑岩的源区存在太古宙结晶基底,并经历了古元古代早期构造-岩浆事件、中元古代晚期构造-岩浆事件(格林威尔运动)和新元古代早期构造-岩浆事件.
납적태군시동곤륜조산대중단출로적구조혼잡암적중요조성부분,대납적태군쇄설암단적지층시대급물질래원진행한정,가이위회복화반연동곤륜조고생대적구조격국제공의거.전인다인위납적태군적지층시대위오도기혹오도기—지류기,단시지류기、이첩기심지신생대적관점야동시존재.통과대납적태군쇄설암단진행쇄설고석년령연구,득도최년경적고석년령538±10Ma,결합침입기중적영운섬장암체적년령위427.7Ma,장납적태군쇄설암적침적시대한정우538~427Ma지간,령외유우납적태군특수적연화의의,결합사송오랍조화새십등조적지층시대,장납적태군쇄설암적지층시대학정위오도기,병인위유가능연신지조지류세.득도적쇄설고석년령보현시약2450Ma、약1100Ma、약980Ma、약810Ma、약650Ma오개명현봉치,결합납적태군쇄설암근원퇴적적특정,장득도적고석년령여동곤륜급린구출로적로지층화암체시대진행비대,추측백사하암조、소묘군、만보구군급신원고대조기재동곤륜지구형성적중산성암체위기가능물원.장득도적고석년령여각기중대구조-암장사건재곤륜조산대류하적지질기록진행대비,추측인위,납적태군쇄설암적원구존재태고주결정기저,병경력료고원고대조기구조-암장사건、중원고대만기구조-암장사건(격림위이운동)화신원고대조기구조-암장사건.
Naij Tal Group consists of a set of ophiolitic mélanges. Therefore, some evidence for restoring the structural pattern of east Kunlun in Early Palaeozoic can be obtained by studying Naij Tal Group's formation time and provenance. Most previous researchers hold the opinion that Naij Tal Group belongs to Ordovician or Ordovician-Silurian;nevertheless, other viewpoints arguing for Silu- rian, Permian or Cenozoic are also existent. The authors obtained the youngest age 538±10Ma by LA-ICP-MS U-Pb dating of the detrital zircons from Naij Tal Group's clastic rocks and thus confined its formation time to 538-427Ma in combination the intrusion age of 427.7Ma. Thus, the formation age of Naij Tal Group was assigned to Ordovician because of its special geological significance. Moreover, there are five age peaks existent in Naij Tal Group's detrital zircons, i.e.,~2450Ma,~1100Ma,~980Ma,~810Ma, and~650Ma. The authors thus suppose that Baishahe Group, Xiaomiao Group, Wanbaogou Group and magmatic rocks formed during ear-ly Neoproterpzoic were provenances of Naij Tal Group's clastic rocks because of the similar distributions of their zircon ages. It is al-so held that the source areas might have experienced early Paleoproterozoic, late Paleoproterozoic, late Mesoproterpzoic and early Neoproterpzoic tectono-magmatic events according to the characteristics of their zircon U-Pb ages.