摘要
河北涞源、阜平一带煌斑岩的地球化学特征表明其来源于地幔,非花岗岩演化成因,有的脉保持原生岩浆的特点,有的脉发生了一定程度的分离结晶,分离结晶对轻稀土影响较大,而对重稀土影响较小,分离结晶作用还导致了Cr,Ni,Sr的逐渐贫化,Ba和Co等元素的逐渐富集。
:
The distribution patterns of rare earth elements for lamprophyres in Laiyuan-Fuping area of LREE-rich type, normalized to chondritic meteorite. The abundance of LREE in alkali lamprophyres is bigger than that in calc-alkaline lamprophyres. These characteristics suggest that the lamprophyres probably came from the upper mantle. The distribution patterns of transitional elements normalized to both chondritic meteorite and the mantle source all show W - shape. The dyke XII -7 which is Grand Ni-rich with the Mg/ (Mg+Fe) of 0. 75 can be considered as the primitive magma directly derived from the upper mantle. According to the above - mentioned characteristics the lamprophyres in the area interested cannot be derived from granitic magma. Moreover, the abundances of Cr, Ni and Sr in lamprophyres show a reductive tendency with respect to crystal differentiation, implying that fractionation of megacrysts such as Cr-bearing diopside, anorthoclase and olivine took place during the evolution of lamprophyre magma. In general, the geochemical features of the lamprophyres in the area studied suggest that they were likely mantle-derived rocks formed from either primary lamprophyre magma or its derivitive magmas that underwent fractional crystallization.
出处
《现代地质》
CAS
CSCD
1991年第3期330-337,共8页
Geoscience
关键词
煌斑岩
碱性
地球化学
成因
河北
: alkali lamprophres, Calc- alkaline lamprophyres, Laiyuan - Fuping, Hebeiprovince
