论文部分内容阅读
琼河坝矿集区北塔山组火山岩是东准噶尔北缘泥盆纪火山岩的重要组成部分。从玄武岩到安山岩,其Mg~#值为38.74~55.31,暗示母岩浆是经过分异演化的玄武质岩浆。在w(MgO)-w(TiO_2)图解中从玄武岩到安山岩的演化趋势与玄武岩熔体演化趋势线相同。在哈克图解中,从玄武岩到安山岩SiO_2含量与Al_2O_3,MnO,MgO,CaO,Na_2O等主量元素之间,呈较明显的负相关,暗示岩浆在演化过程中,可能发生了Mg,Fe矿物的分离结晶。安山岩ΣREE值为72.50×10~(-6)~98.05×10~(-6),LREE/HREE的值为1.64~4.74;玄武安山岩ΣREE值为68.69×10~(-6)~116.04×10~(-6),LREE/HREE的值为1.51~3.50;玄武岩ΣREE值为65.19×10~(-6)~154.53×10~(-6),LREE/HREE的值为1.59~2.70;总体上表现为稀土含量较低,轻、重稀土分馏不明显,且轻稀土元素较重稀土元素富集。通过对北塔山组火山岩主、微量元素的地球化学特征研究,认为北塔山组形成于火山弧环境,玄武质母岩浆为卡拉麦里洋洋壳向北俯冲到地幔岩石圈区域,在俯冲流体的作用下楔形地幔中的石榴子石橄榄岩-尖晶石橄榄岩发生部分熔融而形成。
The Beitashan Formation volcanic rocks in Qiongheba ore district are an important part of Devonian volcanic rocks in the northern margin of East Junggar. From basalt to andesite, the Mg ~ #values range from 38.74 to 55.31, indicating that the parent magma is a differentiated basaltic magma. The evolution trend from basalt to andesite in the w (MgO) -w (TiO 2) scheme is the same as that of the basalt melt. In the Huck diagram, there is a clear negative correlation between SiO 2 content and basal elements such as Al 2 O 3, MnO, MgO, CaO and Na 2 O from basalt to andesite, suggesting that Mg and Fe minerals may occur during the evolution of magma The separation and crystallization. The ΣREE value of andesite ranged from 72.50 × 10 -6 to 98.05 × 10 -6, the LREE / HREE ranged from 1.64 to 4.74, and the ΣREE value ranged from 68.69 × 10 -6 to 116.04 × 10 -3, (-6), and the value of LREE / HREE is 1.51-3.50; the value of LREE / HREE is 65.19 × 10 -6 -645.53 × 10 -6, the value of LREE / HREE is 1.59-2.70; For the rare earth content is low, light, heavy rare earth fractional distillation is not obvious, and light rare earth elements heavier rare earth elements enrichment. Through the study on the geochemical characteristics of the main and trace elements of volcanic rocks in Beitashan Formation, it is considered that the Beatashan Formation is formed in the volcanic arc environment, and the basaltic magma is subducted northward from the Karamay Oceanic crust to the mantle lithosphere. The garnet peridotite-spinel peridotites in the lower wedge-shaped mantle are partially melted and formed.