【摘要】：為研究松遼盆地西緣大興安嶺早白堊世火山巖的構造屬性,對研究區(qū)內流紋巖開展鋯石U-Pb測年和地球化學測定。鋯石U-Pb定年結果顯示,流紋巖形成于131.6±0.6~123.9±1.7Ma,屬早白堊世。主量元素分析表明,流紋巖具高硅(SiO_2=69.08%~79.58%)、富堿(K_2O+Na_2O=5.93%~9.76%,平均為8.14),富鉀(K_2O/Na_2O大于1.0,平均為2.14)、貧鈣鎂(平均CaO為0.60、MgO為0.27)和高FeOT/MgO(平均為6.77)比值的特征,屬過鋁質(A/CNK=1.35~1.78)高鉀鈣堿性—鉀玄武巖系列巖石。據微量元素地球化學特征將其劃分為兩組:Ⅰ組流紋巖稀土元素總量較高(∑REE介于149.04×10~(-6)~213.18×10~(-6)之間,平均為172.35×10~(-6)),輕稀土元素(LREE)富集、輕重稀土元素分餾較強[(La/Yb)_N=4.89~11.87,平均為7.75)],中等—弱負銪異常(δEu=0.54~0.88,平均為0.70),配分曲線右傾模式,強烈富集大離子親石元素(LILE)Rb,Ba,Th,K和虧損高場強元素(HFSE)_Nb,Ta,P和Ti;Ⅱ組流紋巖以稀土總量(∑REE平均為142.60×10~(-6))相對較低,具相對較強的負銪異常(δEu=0.05~0.46,平均為0.27),配分曲線相對較平緩以及Ba,Sr,P,Ti元素的強烈虧損與Ⅰ組流紋巖相區(qū)別,兩組流紋巖地球化學成分相關性較好,二者均有低的Sr(206×10~(-6))和高Yb(大于2)含量,具殼源和造山后花崗巖的特征。結合最新資料及本文研究成果,初步認為研究區(qū)流紋巖為地殼部分熔融的產物,之后經歷強烈的礦物分離結晶作用,與蒙古—鄂霍次克造山后伸展作用有關。
[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 鹵0.6123.9 鹵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，

本文編號：2134765