【摘要】 两江口火山岩 Rb-Sr年龄为 1 5 4Ma,以高 K2 O/ Na2 O,K2 O+Na2 O>6%为特征 ,属于亚碱性高钾钙碱性系列岩石 ;岩石稀土元素及大离子亲石元素富集 ,有较明显的铕负异常 ( δEu=0 .5 0～ 0 .70 ) ;Nb,Ta,Ti和 P亏损 ,具有岛弧型岩石的微量元素配分模式 ,属板内钾质岩石 ;较高的 Si O2 、较低的εNd( t) ( -7.7～ -7.6)和相对低的 t DM(平均为 1 499Ma)表明岩浆主要来源于地壳 ,但有少量地幔物质参与 ;其形成与该区中生代软流圈上升、岩石圈伸展 -减薄有关。更多还原

【Abstract】 The Liangjiangkou volcanic rocks with the Rb-Sr isochron age of 154 Ma are characterized by high K 2O/Na 2O ratios and K 2O+Na 2O>6%, belonging to subalkalic high-K calc-alkaline series. Their chondrite-normalized REE patterns are characterized by enrichment of LREE with relatively obvious negative Eu anomalies(δEu=0.50～0.70). Geochemically, the volcanic rocks are rich in LILE and poor in Nb,Ta,Ti and P, showing the characteristics of island arc volcanic rocks. High contents of SiO 2 and low ε Nd(t) values(-7.7～-7.6)and relatively lowt DM values(averaging 1499 Ma)show that the magma was dominantly derived from the crust. Based on the geological characteristics and regional tectonic evolution history, it is concluded that forming of the Liangjiangkou volcanic rocks might be related to the aesthenospheric upwelling and lithospheric extension and thinning during the Yanshanian Period.更多还原