准噶尔盆地钻井岩芯火山碎屑岩锆石U-Pb定年、微量元素及Hf同位素研究

Zircon U-Pb,Trace Element and Hf Isotopes of Pyroclastic Rocks from the Drilling Cores in the Junggar Basin

采用LA-ICP-MS手段,对准噶尔盆地陆梁隆起中北部Db1井和Y1井巴塔玛依内山组火山碎屑岩中的锆石进行了U-Pb定年、微量元素以及Lu-Hf同位素分析。锆石内部结构、Th/U比值、稀土配分模式显示,所有锆石属岩浆成因。结果显示:①Db1井和Y1井锆石样品最小年龄分别为303Ma和306Ma,可代表巴塔玛依内山组的形成时代;②锆石U-Pb年龄显示有中、晚元古代的1447~1410Ma、885~559Ma的年龄记录,为准噶尔盆地中北部存在前寒武纪古老结晶基底提供了依据,以及古生代早中期536~420Ma、401~360Ma、359~303Ma的年龄记录,指示准噶尔盆地中北部前二叠纪基底经历了多阶段复杂陆壳演化过程;③锆石微量元素分析表明,盆地中北部前二叠纪基底主体属于由花岗岩、正长岩、玄武岩和辉绿岩组成的花岗岩和中基性岩侵入型活动陆壳基底;④锆石Hf同位素分析显示,锆石年龄都具有正的εHf(t)值(+4.6^+19.0),推测锆石母岩主要来源于软流圈地幔或亏损岩石圈地幔熔融作用,岩浆上升-侵位过程中混染了古老基底物质组分。

Simultaneous in-situ analyses of single zircon LA-ICP-MS U-Pb age and trace elements and Hf isotope systematic analysis from the Batamayineishan Formation. The volcanic rock was obtained from drill well Dbl and Y1 on the north-central Luliang uplift within the Junggar Basin. The internal structure of zircon, Th/U ratios, REE patterns show that all samples are magmatic zircon. The results showed that. ①the youngest age is interpreted as the formation age of the studied formation by measured the two zircon samples, that is Late Carboniferous②zircon U-Pb ages display Mid-Late Proterozoic 1447- 1410Ma, 885 -559Ma and the age record from early or middle Paleozoic 536-420Ma, 401-360Ma, 359-303Ma, indicating that the Junggar Basin experienced a complex of continental crust formation and evolution of the multi-stage process;③trace elements of zircon suggest that the basement of north-central Junggar basin in pre-Permian is composed of granite and mafic intrusive activity continental basement by granite, syenite, basalt and dolerite; ④zircon Hf isotope analysis showed that enf （t） values have a relatively great variation ranging from ＋4.6 to ＋19.0, demonstrating that at least two source materials have contributed to the zircon host rock generation, suggesting that magma rise and emplacement process was contaminated by ancient basement material components.