新疆库鲁克塔格地区晚泥盆世火山岩40Ar/39Ar年代学及其地质意义

泥盆纪火山岩在辛格尔断裂以北广泛分布,且以中酸性火山岩为主。笔者在库鲁克塔格地区辛格尔断裂南侧识别出泥盆纪英安岩,⁴⁰Ar/³⁹Ar坪年龄为374.7±5.9Ma,属晚泥盆世。该火山岩样品为钙碱性系列,岩石富铝,富轻稀土(∑LREE/∑HREE=9.43),K、Rb、Sr、Ba、Th等不相容大离子亲石元素相对富集。Eu具弱负异常,Nb、Ti亏损。火山岩形成于活动大陆边缘,可能经历了大陆壳物质的混染。库鲁克塔格火山岩从时代及岩性上与辛格尔断裂北侧泥盆纪火山岩对应,说明泥盆纪火山岩不仅分布于辛格尔断裂以北地区,也见于辛格尔断裂南部。

40Ar/39Ar dating on the Late Devonian volcanic rocks from Kuruktag and its implications for regional geology, Xinjiang

Devonian volcanic rocks widely distributed north to the Qinggir fault. In this investigation, Devonian dacite was recognized south to the Qinggir fault in Kuruktag, northeast of Tarim basin. ~(40)Ar/~(39)Ar plateau age of 374.7±5.9Ma is obtained for the dacite which corresponding to Late Devonian. The volcanic rock is characterized as calc-alkalic series, rich in AI, LREE (∑LREE/∑ HREE =9.43) and LILE (e. g. K, R.b, Sr, Ba and Th), weak negative anomaly in Eu, but lack in Nb and Ti. The volcanic rock formed in active continental margin and may be contaminated by continental crust. From lithologic characteristics and geological age, the volcanic rocks south to the Qinggir fault, Kuruktag area, can compare with the Devonian volcanic rocks north to the Qinggir fault. It indicates that volcanic rocks in Devonian distributenot only north to but also south to the Qinggir fault.