广西姑婆山里松花岗岩中闪长质包体的地球化学特征及其成因探讨

Geochemical Characteristics and Genesis of Dioritic Enclaves in Lisong Granite, NE Guangxi Province

广西姑婆山里松花岗岩中广泛发育有大量的闪长质包体，包体的野外地质特征、显微结构、矿物组合及化学组成等特征显示其岩浆快速结晶成因。它们的主量元素在相关图上呈不同程度的直线变异关系。在微量元素方面，包体和寄主花岗岩都富含大离子亲石元素和高场强元素。用锆石饱和温度和角闪石成分估算了包体和寄主花岗岩结晶的温度和压力表明，它们的结晶温度和压力条件相近，分别在793—824℃和（3．5—5．1）×10^8Pa范围内。岩石学和同位素地球化学特征也表明，里松包体和寄主花岗岩基本同时结晶，但壳幔比例和来源有所不同。这些特征总体上说明了里松闪长质包体可能是两种岩浆混合时不完全消化的产物。

The dioritic enclaves are widely distributed in the Lisong granite. An integrated field and laboratory study on the colours, shapes, textures, structures, compositions, mineralogy and petrology of the enclaves indicates that they are products of rapid crystallization from the silicate melt. The major elements analytical data show a trend characterized by a linear correlation between rock-forming elements. In trace elements, both the dioritic enclaves and hosting granite are enriched in LILEs and HFSEs. Based on the zircon saturation temperature and hornblende geobarometer estimation, the crystallization temperature and pressure of enclaves and hosting granite are very close, in the range of 793 - 824 ℃ and 3.5 - 5. 1 Kb, respectively. The petrological and isotopic features indicate that the Lisong enclaves and hosting granite were basically crystallized at the same time, but with different crust-mantle proportions and different sources. All these integrated data demonstrate that the Lisong enclaves are remnants of magma mingling.