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广西大瑶山隆起区中部的大村岩体,岩性主要为细粒花岗闪长岩。采用LA-(MC)-ICP-MS锆石U-Pb同位素定年技术,获得了该岩体的结晶年龄为451.5±1.3 Ma(MSWD=0.001 4),其形成时代为晚奥陶世,属于加里东晚期岩浆活动的产物。大村岩体岩石含角闪石5%~10%,具低Si O_2(60.74%~64.53%)和K_2O/Na_2O值(0.63~0.89),属准过铝质-弱过铝质钙碱性系列;Rb、Th、U、Pb等元素强烈富集,Ba、Nb、Ta及Ti等元素亏损;稀土总量较低,∑REE为(58.93~99.14)×10~(-6),δEu=0.75~0.83,具弱的负铕异常。综合判断属于I型花岗岩,应为陆内造山运动早期碰撞挤压背景下岩浆活动的产物。
The Ducun rock mass in the central part of Dayaoshan uplift in Guangxi province is mainly composed of fine-grained granodiorite. Using LA- (MC) -ICP-MS zircon U-Pb zircon dating, the crystallization age of this rock body is 451.5 ± 1.3 Ma (MSWD = 0.001 4). Its formation time is Late Ordovician, belonging to Gary Late magmatic activity of the product. The Omura rock mass contains amphiboles ranging from 5% to 10%, with low Si O_2 (60.74% -64.53%) and K_2O / Na_2O (0.63 ~ 0.89) ; Elements such as Rb, Th, U and Pb are strongly enriched and elements such as Ba, Nb, Ta and Ti are depleted; the total rare earth content is low, ΣREE is 58.93 ~ 99.14 × 10 -6, δEu is 0.75 ~ 0.83, with weak negative europium anomaly. The comprehensive judgment belongs to type I granite and should be the product of magmatism under the background of early collision and compression in intracontinental orogeny.