Silicon-rutile - an ultra-high pressure (UHP) mineral from an ophiolite  

作　　者：YANGJingsui BAIWenji FANGQingson YANBinggang SHINicheng MAZhesheng DAIMingquan XIONGMing 

机构地区：[1]InstituteofGeology,ChineseAcademyofGeologicalSciences,Beijing100037,China [2]GeologicalUniversityofChina,Beijing100083,China

出　　处：《Progress in Natural Science:Materials International》2003年第7期528-531,共4页自然科学进展·国际材料（英文版）

基　　金：the National Natural Science Foundation of China (Grant No.49972073)

摘　　要：Silicon(Si)-rutile separated from the Luobusa podiform chromitite in the Yarlung Zangbo ophiolite of southern Tibet is typically about 50 μm × 50 μm × 200 μm in size and consists mainly of SiO2 and TiO2- The average mineral formula is (Ti0. 82Si0.18)O2. Powder X-ray diffraction data show that it is tetragonal in form, and the unit cell dimensions and other parameters are: α= 4. 591(2) A , c = 2.946(2)A, v=62.09(5)A3, c/α=0.6415, with a molar volume about 5 % smaller than rutile (JCPDS, 21-1276). The Si4 + ions in silicon rutile are six-coordinated, and are substituted for Ti + in the rutile structural sites. The Si-rutile, along with other associated ultra-high minerals discovered in the chromitite, such as octahedral silicate, silicon-magnesium spinel (Si4+ ions are six-coordinated), diamond, and intergrown of SiO2 and FeO phases, probably originated from the transition zone or the lower mantle, and were brought to shallow levels beneath an oceanic spreading ridge by an upwelling superplurne.Silicon(Si)-rutile separated from the Luobusa podiform chromitite in the Yarlung Zangbo ophiolite of southern Tibet is typically about 50 μm×50 μm×200 μm in size and consists mainly of SiO2 and TiO2. The average mineral formula is (Ti0.82Si0.18)O2. Powder X-ray diffraction data show that it is tetragonal in form, and the unit cell dimensions and other parameters are: a=4.591(2), c=2.946(2), v=62.09(5)3, c/a=0.6415, with a molar volume about 5% smaller than rutile (JCPDS, 21-1276). The Si4+ ions in silicon rutile are six-coordinated, and are substituted for Ti4+ in the rutile structural sites. The Si-rutile, along with other associated ultra-high minerals discovered in the chromitite, such as octahedral silicate, silicon-magnesium spinel (Si4+ ions are six-coordinated), diamond, and intergrown of SiO2 and FeO phases, probably originated from the transition zone or the lower mantle, and were brought to shallow levels beneath an oceanic spreading ridge by an upwelling superplume.

关 键 词：Si-rutile UHP minerals OPHIOLITE lower mantle chromitite. 

分 类 号：P618.47[天文地球—矿床学] P619.226[天文地球—地质学]