内蒙古浩尧尔忽洞高钾钙碱性花岗岩岩石成因及构造意义

浩尧尔忽洞金矿为低品位超大型中低温热液型金矿，矿区内华力西期花岗岩发育。SiO2含量为71．5％～73．07％，Na2O／K2O值为0．59～0．67，平均值为0．64，属于高钾钙碱性系列。哈克图解上各元素含量随SiO2变化成线性规律明显，具I型花岗岩特征。Mg^#为39～49，其平均值为43，与下地壳麻粒岩的平均值（45．36）相近。∑REE值变化范围为72．64×10^-6～132．6×10^-6总体上稀土含量较低。（La／Yb）Ⅳ值为12．99～34．13，显示轻重稀土有较大的分馏。在稀土元素蛛网图上表现为右倾。Ba／Th值为133．93～178．93，认为板片俯冲流体影响较小。OEu含量为0．52～0．96，平均值为0．75，具有中等到低的Eu亏损。根据其地球化学特征，认为该岩体为后碰撞期形成的高钾钙碱性I型花岗岩。

Petrogenesis and Tectonic Significance of High-K Calc-aikaline Granite in the Haoyao erhudong of Inner Mongolia

Hercynian granite is found developed in Haoyao＇ erhudong gold deposit, a low-intermediate hydrothermal deposit with low-grade ultra-large reserves. Analysis on the granite has shown that the ratio of SiO2 ranges from 71.5% to 73.07%, and the ratio of Na20/ KE O ranges from 0.59 to 0.67 with an average value of 0.64, thus the granite belongs to high-K calc-alkaline series. According to Hark diagram, the content of each element is obviously in line with the variation tendency of SiO2, to express the characteristics of I-type granite. The content of Mg^# ranges from 39 to 49, and its average of 43 is similar to the average value （45.36） of lower crust granulite. The value of ∑ REE from 72.64 X 10.6 to 132.6 X 10.6 signifies a low content of rare earth. The ratio of （La/Yb）N ranges from 12. 99 to 34. 13, revealing biggish frac- tionation between LREE and HREE. The distrJibution curve on REE spider chart goes right. The ratio of Ba/Th ranges from 133.93 to 178.93, indicating less influence on the underthrust plate. The content of 3Eu varies from 0.52 to 0.96, with an average of 0.75, indicating negative Eu anomaly from intermediate to a lower level. According to some other geochemical features, it is considered that the ore body is high-K Calc-alkaline I-type granite formed in post-collision envi- ronment.