松辽盆地西缘早白垩世伸展事件:流纹岩锆石U-Pb年龄、地球化学研究
发布时间：2018-07-20 21:02
【摘要】：为研究松辽盆地西缘大兴安岭早白垩世火山岩的构造属性,对研究区内流纹岩开展锆石U-Pb测年和地球化学测定。锆石U-Pb定年结果显示,流纹岩形成于131.6±0.6~123.9±1.7Ma,属早白垩世。主量元素分析表明,流纹岩具高硅(SiO_2=69.08%~79.58%)、富碱(K_2O+Na_2O=5.93%~9.76%,平均为8.14),富钾(K_2O/Na_2O大于1.0,平均为2.14)、贫钙镁(平均CaO为0.60、MgO为0.27)和高FeOT/MgO(平均为6.77)比值的特征,属过铝质(A/CNK=1.35~1.78)高钾钙碱性—钾玄武岩系列岩石。据微量元素地球化学特征将其划分为两组:Ⅰ组流纹岩稀土元素总量较高(∑REE介于149.04×10~(-6)~213.18×10~(-6)之间,平均为172.35×10~(-6)),轻稀土元素(LREE)富集、轻重稀土元素分馏较强[(La/Yb)_N=4.89~11.87,平均为7.75)],中等—弱负铕异常(δEu=0.54~0.88,平均为0.70),配分曲线右倾模式,强烈富集大离子亲石元素(LILE)Rb,Ba,Th,K和亏损高场强元素(HFSE)_Nb,Ta,P和Ti;Ⅱ组流纹岩以稀土总量(∑REE平均为142.60×10~(-6))相对较低,具相对较强的负铕异常(δEu=0.05~0.46,平均为0.27),配分曲线相对较平缓以及Ba,Sr,P,Ti元素的强烈亏损与Ⅰ组流纹岩相区别,两组流纹岩地球化学成分相关性较好,二者均有低的Sr(206×10~(-6))和高Yb(大于2)含量,具壳源和造山后花岗岩的特征。结合最新资料及本文研究成果,初步认为研究区流纹岩为地壳部分熔融的产物,之后经历强烈的矿物分离结晶作用,与蒙古—鄂霍次克造山后伸展作用有关。
[Abstract]:In order to study the tectonic properties of early Cretaceous volcanic rocks in Daxinganling, the western margin of Songliao Basin, zircon U-Pb dating and geochemical determination were carried out for rhyolite in the study area. The zircon U-Pb dating results show that the rhyolite formed in 131.6 卤0.6123.9 卤1.7 Ma, belonging to the early Cretaceous. Principal element analysis shows that rhyolite is characterized by high silicon (Sio _ 29.08 or 79.58%), alkali-rich (K _ 2O Na _ 2O _ 2O _ 2O _ 5.93 ~ (36) and average of 8.14), potassium rich (K _ 2O / Na _ 2O > 1.0, average 2.14), calcium and magnesium (average Cao = 0.60 mg _ O = 0.27) and high FeOT _ (-MgO) ratio (mean 6.77). It belongs to the peraluminous (A / CNK 1.35 ~ 1.78) high potassium calc alkaline-potassium basalt series. According to the geochemical characteristics of trace elements, they are divided into two groups: the REE of group 鈪，
本文编号：2134765
[Abstract]:In order to study the tectonic properties of early Cretaceous volcanic rocks in Daxinganling, the western margin of Songliao Basin, zircon U-Pb dating and geochemical determination were carried out for rhyolite in the study area. The zircon U-Pb dating results show that the rhyolite formed in 131.6 卤0.6123.9 卤1.7 Ma, belonging to the early Cretaceous. Principal element analysis shows that rhyolite is characterized by high silicon (Sio _ 29.08 or 79.58%), alkali-rich (K _ 2O Na _ 2O _ 2O _ 2O _ 5.93 ~ (36) and average of 8.14), potassium rich (K _ 2O / Na _ 2O > 1.0, average 2.14), calcium and magnesium (average Cao = 0.60 mg _ O = 0.27) and high FeOT _ (-MgO) ratio (mean 6.77). It belongs to the peraluminous (A / CNK 1.35 ~ 1.78) high potassium calc alkaline-potassium basalt series. According to the geochemical characteristics of trace elements, they are divided into two groups: the REE of group 鈪，
本文编号：2134765
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