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罗东岩体是新疆北山地区沿北山裂谷带的一个典型镁铁质—超镁铁质岩体,研究表明坡北杂岩带与东天山杂岩带的产出时代具有时间上的耦合性,并且其大地构造产出背景与东天山镁铁质—超镁铁质杂岩也具有一定的关系,可能与碰撞背景下幔源物质的上侵有关,并且受到俯冲板片的影响。该岩体具有较完整的岩相分异,包括橄榄岩、辉石岩、辉长岩。镁橄榄石指数Fo值为81～88,属于贵橄榄石,橄榄石具有环带结构,从橄榄石边缘到中心,Mg逐渐升高,说明橄榄石在岩浆演化过程中发生了与残余岩浆的交换反应。通过主量元素反演,得到原始岩浆中w(MgO)=8%、w(FeO)=6%,属于拉斑玄武岩。通过橄榄石的定量模拟计算,显示罗东岩体的橄榄石为正常岩浆演化的产物,橄榄石中Ni的质量分数没有发生明显亏损,这些证据表明岩浆可能没有经历过显著的硫化物熔离作用。
The Luodong pluton is a typical mafic-ultramafic rock along the Beishan rift zone in the Beishan area, Xinjiang. Studies have shown that the Poupi complex is temporally coupled with the East Tianshan complex belt and Its geotectonic output background also has some relation with the eastern Tianshan mafic-ultramafic complex, which may be related to the uplifting of the mantle-derived materials in the collision background and is influenced by the subducted slab. The rock body has more complete lithofacies differentiation, including peridotite, pyroxene rock, gabbro. The forsoidite fof value is 81-88, which belongs to the peridot and the olivine has a zonal structure. From the edge of the olivine to the center, Mg gradually increases, indicating that the olivine has exchanged with the residual magma during the magmatic evolution reaction. Through the inversion of the main elements, the original magma w (MgO) = 8%, w (FeO) = 6%, which belongs to tholeiitic basalt. Quantitative simulation of olivine shows that the olivine in the Luodong granite is the product of normal magmatic evolution, and no significant loss of mass fraction of Ni in the olivine occurs. These evidences indicate that the magma may not have undergone significant sulfide ionization.