西秦岭礼县新生代钾霞橄黄长岩系中的含钛透辉石

对西秦岭礼县新生代钾霞橄黄长岩系中的基质相含钛透辉石进行了矿物化学研究，根据透辉石中Ti和Al的含量划分出低Ti—透辉石和高Ti—铝透辉石两种基本类型，它们作为同源岩浆演化结晶的产物，结晶顺序前者先于后者。火山岩系的透辉石[Ca(Mg，Fe)Si2O6]结晶过程中广泛存在着CaTiAl2O6(钛辉石)分子替代，晚期熔体富Ti、Al贫Si、Mg。百草山岩筒是演化岩浆结晶的产物，熔体向富Ti、Al、Fe^3 、Na，贫Mg、Si趋势演化；在透辉石成分上表现为CaTiAl2O6和NaFe^3 Si2O6(锥辉石)端元分子对Ca(Mg，Fe)Si2O6的替代。本地区基质相透辉石与世界上典型地区的钾霞橄黄长岩系的透辉石具有不同程度的可比性，反映了这种特殊的岩浆熔体成分在一定程度上控制着透辉石的结晶过程和阳离子在矿物晶格中的占位。

Ti-BEARING DIOPSIDES FROM CENOZOIC KAMAFUGITES IN WESTERN QINLING,LIXIAN COUNTY

This paper deals with the chemical composition of groundmass diopsides in the kamafugitic series from the area of Lixian County, western Qinling. The groundmass diopsides-pyroxenes are grouped into two pyroxene types: high Ti-aluminian diopside and low Ti-diopside, which crystallized from comagmatic melts. The substitution of Ca(Mg, Fe)Si 2O 6 by CaTiAl 2O 6 is common during the crystallization of diopsides with the late melt rich in Ti and Al, but poor in Si and Mg. The Baicaoshan volcanic pipe is the product of an evolved magma with an evolutionary trend of enriching Ti, Al, Fe 3+, Na, and depleting Mg and Si, which can be expressed by the the substitution of Ca(Mg, Fe)Si 2O 6 by CaTiAl 2O 6 and NaFe 3+Si 2O 6 during the crystallization process of diopsides. The compositions of diopsides in kamafugitic series from typical areas of the world can be compared in certain degrees, showing that the bulk composition of kamafugitic rocks provides constraints on mineralogical composition and crystal lattice features.