东准噶尔卡姆斯特北海相火山-沉积岩碎屑锆石LA-ICP-MS U-Pb年龄及地质意义

摘要

There has been a controversy in zircon U-Pb ages of marine volcanic-sedimentary detrital rock, which occurred in 10 km away from the northern Kamste in Eastern Junggar. Thus, the zircon U-Pb ages of detrital rock were measured by the LA-ICP-MS method. And 100 detrital zircons had been tested totally, of which 90 ages of these zircons are useful. The dating results have shown that: (1) the formation age of this rock stratum may be Early Carboniferous, because the deposition time was later than 333. 2 Ma which has been limited by the youngest age of detrital zircon. (2) There are multiple provenances for this rock stratum, which are proved by the contrast results between detrital zircon dating results and regional magmatic events as follows;Early Cambrian (523. 1 Ma, 535. 1 Ma)detrital zircons might source from Precambrian crystalline basement of Junggar, but need further research;Middle-Late Ordovician (440. 0 Ma, 460. 9 Ma) detrital zircons came from pyroclastic rocks of Huangcaopo Group;Early Silurian(429. 3 Ma)detrital zircon might originate from the Lower Silurian stratum, which was deposited in the surrounding of this study area;Middle Devonian ((371.5±2. 5) Ma) detrital zircons derived from the strata of Zhuomubasitao Formation and Wulusubasitao Formation;and Early Carboniferous ((336.4 ±0. 8) - (353. 5 ±0. 7) Ma)detrital zircons stemmed from the stratum of Nanmingshui Formation. (3) In addition, there is a zircon aged 2,676.2 Ma having the harmonic degree of 99% , which has provided some basis for the possible existence of Precambrian ancient crystallization basement, but needs further evidence.%运用LA-ICP-MS U-Pb法,对位于东准噶尔卡姆斯特北部10 km处有争议的海相碎屑岩样品进行了U-Pb年龄测定,共测试碎屑锆石100颗,其中有效年龄数据点共90个.测试结果表明:(1)该套岩层的形成年龄可能为早石炭世.因为最年轻的谐和年龄为333.2 Ma,限定了该岩层的沉积下限.(2)该套岩层有多个物源区.碎屑锆石定年结果与区域岩浆热事件对比结果表明:早寒武世碎屑锆石(523.1 Ma、535.1Ma)可能来自前人所述的准噶尔前寒武纪结晶基底,但有待进一步研究；中一晚奥陶世碎屑锆石(440.0 Ma、460.9 Ma)来自荒草坡群火山碎屑岩；早志留世碎屑锆石(429.3 Ma)可能来源于周边地区沉积的下志留统；中泥盆世碎屑锆石 《371.5±2.5)Ma)来自卓木巴斯套组和乌鲁苏巴斯套组地层；早石炭世碎屑锆石 《336.4±0.8) ～(353.5±0.7)Ma)来自南明水组.(3)在测试的碎屑锆石中,有一颗锆石年龄为2 676.2 Ma,谐和度为99％,为可能存在前寒武纪古老结晶基底提供了一定的依据,但有待更进一步的证据.