华北隆化地区七家南岩体中镁铁质微粒包体的发现与成因——岩相学和地球化学证据  

The Genesis of Mafic Microgranular Enclaves of the Qijianan Pluton in the Longhua Area in the North China Craton:An Integrated Petrographic and Geochemical Study

作　　者：邓江夏 英基丰[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院大学,北京100049

出　　处：《矿物岩石地球化学通报》2016年第2期328-343,共16页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(91214203)

摘　　要：华北北缘隆化地区的七家南岩体英云闪长岩中发育有大量镁铁质微粒包体,为探明其成因,开展了岩相学与地球化学研究。结果表明,塑性外形的包体具有典型的岩浆结构和矿物组合,可见冷凝边和反向脉;广泛出现矿物交换现象与不平衡结构:如"环斑"斜长石、榍石-斜长石眼斑、针状磷灰石、熔蚀状锆石等。镁铁质微粒包体较寄主英云闪长岩贫硅、高钙铝、富镁铁,更富集大离子亲石元素,高场强元素亏损程度稍低。在主微量元素协变图解上,二者往往呈良好线性关系的岩浆混合作用趋势;它们的Mg/(Mg+Fe)与Na/(Na+Ca)值也都表现出岩浆混合作用的特点。因此,七家南岩体中的镁铁质微粒包体是进入到寄主英云闪长质岩浆中的偏基性淬冷团块,即岩浆混合作用的产物。In this paper we present new data on marie microgranular enclaves（MMEs）occurred in the Qijia＇nan tonalite pluton in the Longhua area where is located in central part of the northern margin of the North China Croton. Petrographic and geochemical studies on these MMEs and their host tonalite have been carried out in order to probe the genesis of MMEs. Results show that round and elliptical MMEs have typical magmatic textures and mineral assembladges with quench boundary and back veins locally. Phenomenon of mineral exchange and various unbalanced textures including ＂rapakivi＂ plagioclase,acicular apatite,sphene-plagioclase oeelli,corroded zircon, are observed widely in these MMEs. Comparing to the host tonalite, the MMEs are depleted in SiOz ,but enriched in Al2O3, CoO, TFe2O3, and MgO in terms of major ele- ments, and highly enriched in LILE but slightly depleted in HFSE interms of trace elements. Quite good linear relationship shown in many covariance diagrams and ratios of Mg/（Mg＋Fe） and Na/（Na＋Ca） for MMEs and their host tonalite repre- sent the characteristics of magma mixing and/or mingling. Therefore, we believe that the MMEs of the Qijia＇nan pluton re- present quenched marie magma globules mixed into the tonalitic magma through magma mixing.

关 键 词：镁铁质微粒包体 岩浆混合 华北北缘 隆化 

分 类 号：P588.1[天文地球—岩石学]