西昆仑库地煌斑岩的年代学及地球化学特征

Age and geochemical features of lamprophyres in Kuda, western Kunlun.

在西昆仑库地发现的煌斑岩脉为钙碱性、钾质闪煌岩 ,侵位在加里东期的变质增生楔杂岩中 ,采用角闪石单矿物40 Ar/ 39Ar同位素年代学方法确定煌斑岩的侵位年龄为 40 4Ma。煌斑岩的稀土元素总量较高 ,配分图呈轻稀土富集的右倾型式 ;微量元素以相对富含大离子亲石元素、亏损高场强元素为特征 ;结合地球化学、同位素特征和大地构造背景分析 。

The field observation, petrology, geochemical features and age of the lamprophyres in Kuda, western Kunlun are presented in this paper. The lamprophyres occur as dikes emplaced in Caledonian metamorphic accretionary complex with the wall rocks of muscovitequartz schist and felsic gneiss. The emplacement age of lamprophyres is 404Ma determined by hornblende ^(40)Ar/^(39)Ar dating method. The lamprophyres are characteristed as calcalklic kalicamptonite. The total REE and the LREE/HREE ratio of lamprophyres are up to ca. 180 and 3.0, respectively. Also, it is relatively rich in LILE and depleted in HFSE. Based on the analysis of geochemical features, SmNd isotope and tectonic setting, it is concluded that the lamprophyres may occur from depleted mantle wedge which was metasomatosed due to the subduction of ProtoTethys.