摘要
研究区奥陶纪花岗岩分布于乌兰布拉格 -哥舍深大断裂 (槽台断裂 )以北 ,岩石类型主要有闪长岩、石英闪长岩、斜长花岗岩和花岗闪长岩。岩石中 Si O2 质量分数为 5 6.76%～ 69.2 4 % ,Al2 O3较高 (多 >1 6% ) ,富 Na2 O贫 K2 O,A/ CNK均 <1 .1 ,为准铝质的钙碱性岩石系列。稀土总量普遍较低 ,为 (63 .4 1～ 1 4 0 .61 )× 1 0 - 6 ,轻重稀土分馏强烈 ,铕异常不明显 (δEu=0 .95～1 .2 2 6)。痕量元素特征与典型的火山弧花岗岩相似。结合区域地质背景 ,认为该套花岗岩类为与洋壳消减有关的岛弧型花岗岩 ,岩浆起源于加厚陆壳的底部。从花岗岩的分布及迁移规律推测 。
The Ordovician granites distributed in north side of the Wulanbulage-Geshe deep-seated fault, including diorite, quartz diorite, plagiogranite and granodiorite. These rocks belong to quasi-aluminous and calc-alkali series with the content of SiO 2 ranging from 56.76% to 69.24% and Al 2O 3 usually more than 16% and the A/CNK ratios less than 1.1.The total content of REE is usually low(ranging from 63.41×10 -6 to 140.61×10 -6) with obvious enrichment of LREE and weak Eu anomaly(δEu=0.95～1.226). The characteristics of trace elements are similar to that of island-arc granites (IAG). Based on analyses of regional geological setting, we believe that those granitois are ialand-arc type related to ocean plate subdution and the magma may be derived from the crust bottom. The distribution and transferred rule of granites in the studied area implicated that the early Paleozoic ocean plate between North China massif and its northern accretion belt might be subducted from southwest to northeast.
出处
《华南地质与矿产》
CAS
2003年第1期17-22,共6页
Geology and Mineral Resources of South China
关键词
岛弧型花岗岩
洋壳消减
奥陶纪
内蒙古达茂旗
island-arc type granite
ocean plate subduction
Ordovician
Damao in Inner Mongolia
