新疆东准噶尔萨北富碱花岗岩SHRIMP锆石U-Pb测年及其地质意义

Zircon SHRIMP U-Pb Dating and geological implication of the Sabei alkali-rich granite from Eastern Junggar of Xinjiang,NW China.

萨北锡矿赋矿的富碱(A 型)花岗岩隶属于新疆东准噶尔地区卡拉麦里富碱花岗岩带,其中的萨北超单元可以划分为细粒钠铁闪石花岗岩、中细粒钠铁闪石花岗岩、中粗粒钠铁闪石花岗岩和斑状钠铁闪石花岗岩等四个单元。本次工作选择萨北超单元中的中细粒钠铁闪石花岗岩和中粗粒钠铁闪石花岗岩进行 SHRIMP 锆石 U—Pb 定年,所获得的两个样品加权平均年龄分别为313±2Ma 和314±5Ma,谐和年龄分别为310±7Ma 和314±10Ma。结合对中亚造山带东准噶尔晚古生代构造环境和萨北富碱花岗岩带花岗岩的地球化学特征,作者认为:该岩体侵位于晚石炭世(约310Ma),为晚古生代后碰撞岩浆活动的产物,与东准噶尔后碰撞深成岩浆活动的两个峰期(330～310Ma 和305～280Ma)中的前一个峰期相一致。

Abstract The Sabei superunite is located in the Kelameili alkali-rich granites belt in the eastern Junggar of Xinjinang, NW China. The superunite, classified as A-type granite, is further subdivided as four units including fine-granied, midium-fine grained, medium- coares, and porphyritic sodahornblende granite. This paper presents the weighted average age （313 ± 2Ma and 314 ± 5Ma） and the concordant age （310 ± 7Ma and 314±lOMa） of the midium-fine grained and the midium-coares sodahornblende granite, respectively. The U-Pb age determination of zircons using SHRIMP shows that granites of the Sabei superuite were intruded at about 310Ma of late Carboniferous. Combining the late Paleozoic tectonic setting of Eastern Junggar in Central Asian Orogenic Belt （ CAOB ） and the geochemical characteristics of the granites in the Sabei alkali-rich A-type granite belt suggests that the Sabei superunite is of typical post-collisional plunton, and is related to the first peak of the two late Paleozoic post-collisional plutonism peaks （330～3lOMa and 305～280Ma） in Eastern Junggar of CAOB.