新疆阿拉尔重熔型花岗岩的地球化学特征及构造意义

西天山地区广泛分布地壳重熔型的花岗岩,年龄多集中于300Ma左右,在时代上属于晚石炭世,阿拉尔花岗岩具有高硅低铝、富钾贫钠、准铝质,A/CNK介于0.79～1.05之间,σ在1.55～1.83之间。明显富集Rb、Th、K等大离子不相容元素,亏损Ba、Sr、P、Ti等元素,并具有弱Nb亏损,稀土元素分布曲线呈明显的＂海鸥＂型。由早侵入次到晚侵入次,有向酸碱性增强方向演化,显示重熔型花岗岩特征,形成于挤压向拉张过渡构造背景下。

GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL SIGNIFICANCE OF GRANITES IN THE ALAER,XINGJIANG

In the west Tianshan Mountains area are extended widely crustal remelted granite,most of determined age are around 300Ma,late Carboniferous.it is characterized by high-silica and low aluminum,potassium-rich and sodium-poor,weakly peraluminous,the values of A/CNK 0.79～1.05,and σ 1.55~1.83.The geochemical analysis of trace elements show that the granite significantly enriched with Rb,Th,K and other large ion,obviously depleting Ba,Sr,P,Ti,and has a weak negative anomaly of Nb.The REE pattern is characterized by rightward declined ＂Seagull＂ type.From early to late invasive alien times,there were the trend of the evolution to acidity and alkalinity,indicating the features of remelted granite formed in a tectonic transition from compression to extension setting.