摘要
我国金伯利岩中的云母主要为金云母。镁黑云母和铁黑云母较少见。根据金伯利岩中云母的光学性质,将其分为正吸收和反吸收云母。一般反吸收云母沿正吸收云母的解理面及边缘进行交代。反吸收金云母在四面体位置中,有相当多的Fe^(3+)。环带状云母的成分,从中心向边部不规则变化。富含金刚石的金伯利岩的基质云母含FeO,TiO_2低。云母加热至1100℃时,则变化为橄榄石和石榴石。
The micas are common in kimberlites with the contents ranging from 2—50％, often 5—20％. The main occurrences of micas are as follows: (A) Megacryst (>1cm); (B)Macrocryst (generally 2—5mm); (c) microphenocryst and groundmass micas (0.5—1mm) (D)Reaction and replacement product micas; (E)Micas intergrowths with Cr-spinel, ilmenite and magnetite; (F) Epigenetic inclusion in diamonds; (G) Micas in deep-seated xenoliths of kimberlites.
The micas in kimberlites from China mainly are recognized as phlogopites and Mg-biotite, Fe-biotite are. Based on the optical, micas in kimberlites can be divided into two groups: normal and reversed pleochroism. Generally the normal pleochroism micas have been replaced by reversed pleochroism micas along cleavage planes and margins. The reversed pleochroism phlogopites have substantial Fe^(3+) in tetrahedral sites. The disorderly compositional variation is found from core to rim in zonation micas. Groundmass micas of diamond-rich kimberlitas are lower in FeO, TiO_2 than that of diamond-poor kimberlites. The micas will transfer to olivimes and leucites at the temperature of 1 100℃.
The micas in lamproites and minettes are typically richer in TiO_2 and FeO than kimberlite micas.
出处
《矿物岩石》
CAS
CSCD
1991年第4期33-43,共11页
Mineralogy and Petrology
关键词
金伯利岩
云母
深源
包体
金刚石
kimberlite, mica, deep-seated xenolith, diamond
