河北寿王坟花岗闪长岩中暗色微粒岩石包体的成因

暗色微粒岩石包体可以提供花岗岩浆的起源和演化、壳—幔物质及能量交换、岩浆混合等重要信息。河北兴隆寿王坟闪长质暗色微粒岩石包体及其寄主花岗闪长岩的岩石学、岩石地球化学特征显示了岩浆的混合成因,并具有以下特征:(1)在基性岩浆中丰度大于酸性岩浆中的不相容元素在与SiO2的相关图中呈一向上凸的弧形型式;(2)在基性岩浆中丰度小于酸性岩浆中的不相容元素在与SiO2的相关图中呈正相关的线性趋势;(3)相容元素在与SiO2的相关图中呈一负相关的线性趋势;(4)在w(La) w(La)/w(Sm)图上微粒包体与其寄主花岗闪长岩为一下凹的型式。基性岩浆与酸性岩浆的两端元岩浆的简单混合模型不能解释以上特征,可以用三阶段混合模型来解释,即第一阶段为基性岩浆注入酸性岩浆中,第二阶段为基性岩浆演化并分离结晶形成微粒包体,第三阶段为演化了的基性岩浆与酸性岩浆混合,形成寄主花岗闪长岩。

GENESIS OF MICROGRANULAR ENCLAVES IN SHOUWANGFEN GRANODIORITES,HEBEI PROVINCE

Microgranular enclaves can provide some important information about the origin and evolution of the granitoid magma, crust mantle interaction of the material and energy, and magma mixing. The characteristics of petrology and petrochemistry of microgranular enclaves and host granodiorites in Shouwangfen, Hebei Province show the genesis of magma have following properties: (1)the incompatible elements whose mass fractions are higher in basic magma than in acid magma show a protrusive arc at the correlation diagram with SiO2; (2)the incompatible elements whose mass fractions are lower in basic magma than in acid magma show a positive correlative linear tendency at the correlation diagram with SiO2; (3)the compatible elements show negative correlative linear tendency with SiO2; (4)the pattern of La La/Sm shows one concave line. A simple mixture model of acid magma and basic magma cannot explain the characteristics,but the three stage mixture model can be used for the explanation: in stage 1, basic magma infused into acid magma; in stage 2, basic magma evolved and fractionalized and formed microgranular enclaves; in stage 3, evolved basic magma mixed with acid magma and formed host granodiorites. 