摘要
本区富钾火山岩中浅色矿物有碱性长石、白榴石和霞石。碱性长石主要为钠透长石、钙歪长石,少数为钙钠透长石和歪长石,其光性变化与长石的地质时代和长石内部的隐条纹结构有关。白榴石的成分及产出方式主要与岩石中的SiO_2含量有关,SiO_2不饱和程度大的白榴苦橄岩的白榴石贫SiO_2;而SiO_2不饱和程度低的白榴碧玄岩和白榴玄武岩中,白榴石富SiO_2而稍贫K_2O+Na_2O,仅见于过渡相,而中心相由于水压较高和近于平衡的结晶条件,白榴石不能晶出,或先晶出后又与熔体反应形成碱性长石。
The light - colored minerals of K -rich volcanic rocks in this area are alkaline feldspar, leucite and nepheline. Most of the alkaline feldspars are Ca - anorthoclasite and Na -sanidine, a few are anorthoclasite and Ca - Na - sanidine. Their various optical properties are resulted from that the degree of feldspar order increases with geological age, and is related to the cryptoperthite. The composition and occurence of leucite are related to the undersaturated degree of SiO2 .The leucite of leucite picrite which is more undersaturated in SiO2 is poor in SiO2 .In leucite basalt which is less undersaturated in SiO2 ,the leucite,which occurred only in transitional phase of lava in the form of phanerocrystal, is rich in SiO2 and poor in K2O + Na2O. In the central phase of lava where the PH2o being higher and the condi-tion of crystallization trending towards equilibrium ,leucite or can't crystallize or is crystallized early but can't maintain,for in this way it will react with lava to form alkaline feldspar.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
1990年第4期357-366,共10页
Earth Science-Journal of China University of Geosciences
关键词
富钾火山岩
浅色矿物
碱性长石
K-rich volcanics , alkaline feldspar , crytoperthite , leucite , Wudalianchi ,Heilongjiang Province .
