新发现的沂蒙矿类质同象系列矿物──K(Ti_5Fe_3Cr_2Mg_2)_(12)O_(19)及Ba(Ti_5Fe_4Mg_2Cr)_(12)O_(19)  

NEWLY DISCOVERED MEMBERS OF YIMENGITE ISOMORPHOUS SERIES K (Ti_5Fe_3Ca_2Mg_2)_(12)O_(19) AND Ba (Ti_5Fe_4Mg_2Cr)_(12)O_(19)

作　　者：陆琦[1] 周湖云[1] 

机构地区：[1]中国地质大学,武汉430074

出　　处：《矿物学报》1994年第3期228-233,T001,共6页Acta Mineralogica Sinica

基　　金：国家自然科学基金

摘　　要：在山东蒙阴金伯利岩中，首次发现了沂蒙矿类质同象系列新的富Ti矿物（变）种。理想的晶体化学式可表达为：K（Ti5Fe3Cr2Mg2）12O19（简称K－Ti沂蒙矿）（Ba，K）（Ti5Fe4Mg2Cr）12O19（简称Ba－Ti沂蒙矿）从而与原来确定的沂蒙矿K（Cr5Ti3Fe2Mg2）12O19和钡钛铁铝矿（Ba，K）（Cr4Fe4Ti3Mg）12O19一起构成了金伯利岩中AM12O19磁铁铅矿型矿物的K-Cr、Ba－Cr、K-Ti、Ba-Ti四种端元类型的复杂类质同象系列。新发现的两个矿物（变）种均产出于具叶片状尖晶石出溶体的镁钛铁矿中。根据结构已知的沂蒙矿中原子的占位和配位多面体情况，分析了K－Ti，Ba－Ti沂蒙矿中各原子的占位和配位多面体，认为新发现的两个（变）种在成分上与沂蒙矿和钡钛铁铬矿有明显的区别。根据镁钛铁矿、尖晶石、沂蒙矿新（变）种、钙钛矿之间的相互关系，探讨了它们的形成环境，从而为这类矿物的地幔成因提供了直接证据。New Ti-rich members of yimengite isomorphous series have been found in the Mongyin kimberlite, Shandong Province. The ideal compositional formulae are:K (Ti5Fe3Cr2Mg2)12O19 (K-Ti yimengite)(Ba, K) (Ti5Fe4Mg2Cr)12O19 (Ba-Ti yimengite)Together with yimengite K (Cr5Ti3Fe2Mg2)12O19 and hawthorneite Ba (Cr4Fe4Ti3Mg)12O19 discovered previously, all the four members make up a complex isomorphous series of magnetplumbite-type minerals. Two new Ti-varieties all occur in picroilmenite which contains crystallographically oriented spinel exsolution lamellae. Depending upon the relationships between picroilmenite, spinel, yimengite and perovskite, the formation conditions of them were discussed.According to the known structure parameters, we analyzed the atomic coordinates and polyhedra for the new Ti-varieties- Because K-Ti and Ba-Ti yimengites and hawthorneite are significantly different from yimengitt and hawthorneite in chemical composition, it is considered that the two minerals should be named after the structure data developed.

关 键 词：沂蒙矿 新矿物变种 镁钛铁矿 

分 类 号：P578[天文地球—矿物学]