花岗岩类特征对准噶尔盆地基底性质的示踪

1.西安科技大学 地质与环境学院,陕西 西安710054; 2.西北大学 大陆动力学国家重点实验室,陕西 西安710069; 3.中国石油长庆油田分公司 勘探开发研究院,陕西 西安 710018

花岗岩; 同位素定年; εNd(t)值; 基底; 准噶尔盆地

Features of granites and its implications on the property of basement of Junggar Basin
FAN Ting-ting1,2,LIU Yi-qun2,BAI Qing-hua3,ZHAO Wei-bo3

(1.College of Geology and Environment,Xi'an University of Science and Technology,Xi'an 710054,China; 2.State Key Laboratory of Continental Dynamics,Northwest University,Xi'an 710069,China; 3.Exploration and Development Research Institute,Petrochina Changqing Oilfield Company,Xi'an 710018,China)

granite; isotope dating; εNd(t)value; basement; Junggar Basin

DOI: 10.13800/j.cnki.xakjdxxb.2017.0513

备注

准噶尔盆地基底属性长期以来存在较大争议,其争议主要集中在基底的性质是陆壳还是洋壳,以及是否存在前寒武纪的古陆块结晶基底。展开盆地周缘造山带的花岗岩类研究能够反演地壳形成演化,示踪基底性质。在阅读大量国内外文献的基础上,通过分析比较准噶尔盆地周缘各地区的同位素定年和花岗岩εNd(t)值关系,研究各区不同时期花岗岩的形成源区,进而探讨准噶尔盆地的基底性质。研究得出古生代-早中生代花岗岩形成时期主要在425~230 Ma之间,其εNd (t)值变化范围在+10~-5之间。说明准噶尔盆地不同区块花岗岩的时代和εNd (t)值关系差异性显著,反映了不同区块构造活动性和地壳组成的差异性。整体上准噶尔盆地周缘露头区不同时期花岗岩形成源区复杂,主要为亏损幔源岩浆,其次为壳幔混源和壳源。表明准噶尔盆地基底存在一定规模古老地块,准噶尔盆地西部和准噶尔盆地北部可能为残留有陆壳残块的古生代新生地壳。

The debate on basement property of Junggar Basin has been exciting for a long time.The disputable property is mainly focused on oceanic or continental crust.And the existence of Precambrian crystalline basement in this area is also controversial.Investigation on granites from orogens around the basin can indicate the forming evolution of crust,and implicate the property of basement.On the basis of review on domestic and overseas citeratures,the distinct difference of isotopic dating and εNdvalue of granites from outcrops in different districts around the Junggar Basin indicates the diversity of tectonic activities and crustal component of different districts.Generally,the granites in Paleozoic and early Mesozoic formed between 425~230 Ma with εNd (t)values ranging from +10 to -5,which indicate that the origins of granites outcrops from different periods around the basin are complex,and mainly derived from decrease mantle,then followed by mixed crust and mantle,and crust.Above all,certain scales of old terrane exist in the basement of Junggar Basin.And Paleozoic continental crusts mixed with remaining pieces of a shattered progenitor possibly exist at the south and north Junggar Basin.