西华山复式花岗岩株地球化学特征及构造环境探讨

Geochemistry Characteristics of Xihuashan Granite and Structural Environment Discussion

西华山复式花岗岩株位于南岭东段，在广泛分布于华南地区的与钨矿床有关的燕山期花岗岩中，西华山复式花岗岩株具有一定的典型意义。西华山复式花岗岩株第一期为斑状中粒黑云母花岗岩（γ5^2-1a）与斑状中细粒黑云母花岗岩（γ5^2-1b），第二期为中粒黑云母花岗岩（γ5^2-1a）与细粒石榴子石-二云母花岗岩（γ5^2-2b），第三期为花岗斑岩（γ5^2-3）。花岗岩均具有高硅，高碱，贫钛、铁、镁、钙、磷等特点，均属强过铝质高钾钙碱性岩系，ACNK值都大于1．1，显示出S型花岗岩的特征。花岗岩锆石u-Ph年龄为150～153Ma。各阶段花岗岩EREE平均值为237．15×10^-6，可以看出西华山地区花岗岩的稀土总量平均值要高于南岭花岗岩平均值229．68×10^-6。其中Y5^2-1a，Y5^2-1b，Y5^2-3属于轻稀土富集型岩石，Y5^2-1a，Y5^2-2b属于重稀土富集型岩石。各阶段花岗岩都表现出明显的Eu亏损。地球化学特征及区域构造演化背景等表明岩石形成于后造山陆内环境。

There are five granitic intrusions which are biotite monzogranite in the district of Xihuashan. They are divided into three phases, show high Si, alkaline, poor Ti, Fe, Mg, Ca, P , belong to strongly-peraluminous high-K calc-alkaline series, ACNK 〉 1.1. All this imply that the granites are S-type granite. Zircon U-Pb dating age is （ 150 - 153 ）Ma. The average of TREE is 237.15× 10- 6 higher than Naling granite （229.68 × 10-6） Y5^2-1a, Y5^2-1b Y5^2-3 represent a LREE-rich curve while Y5^2-2a ,Y5^2-1b snow a HREE-rich curv, but Eu negative anomaly are obvious in all granites. The granites geochemical characteristics and regional tectonic evolution background indicate that the rocks were formed in a post-orogenic extension environment, lithospherie thinning and extension tectonic background.