高温高压下Mg_2SiO_4-MgAlO_4体系相变的实验研究  

EXPERIMENTAL STUDY ON THE PHASE RELATIONS OF THE SYSTEM Mg_2SiO_4-MgAl_2O_4 AT HIGH PRESSURE AND HIGH TEMPERATURE

作　　者：翟双猛[1] 陈汉林[1] 费英伟 杨树锋[1] 

机构地区：[1]浙江大学理学院地球科学系 [2]Geophysical Laboratory,Camegie Institution of Washington,Washington D.C.20015,USA

出　　处：《矿物学报》2003年第3期267-272,共6页Acta Mineralogica Sinica

基　　金：国家自然科学基金(批准号:49872073;40072096);教育部高等学校优秀青年教师教学和科研奖励计划;美国国家科学基金(EAR-9873577);美国Camegie Institution Washington资助项目

摘　　要：采用多顶砧高压实验装置研究了Mg_2SiO_4-MgAl_2O_4体系在压力为22 GPa,温度为1550～1750 ℃条件下的相变,并考查了Al_2O_3在γ相中的固溶度。结果表明,随着体系中MgAl_2O_4组分含量的增加,相组合发生了变化,依次为γ相+镁铝硅酸盐固溶体+方镁石→镁铝硅酸盐固溶体+方镁石→镁铝硅酸盐固溶体+方镁石+刚玉固溶体;镁铝硅酸盐固溶体具有石榴子石结构,其化学成分随着体系中共存相的改变而有所变化;Al_2O_3在γ相中的固溶度很低(其重量百分比<0.8％),因此,在Mg_2SiO_4-MgAl_2O_4体系中Al_2O_3可能对γ相超尖晶石分解转变的压力不会有很大的影响。High-pressure and high-temperature experiments were conducted on the system Mg2SiO4-MgAl2O4 over a temperature range from 1550 to 1750℃ at 22 GPa with a multi-anvil apparatus. Analyses of quenched run products revealed that in the present system, with the MgAl2O4 component increasing, the phase assemblages change from y phase to 7 phase + majorite + MgO, and to majorite + MgO, and to majorite + MgO + corundum solid solution, and finally to MgO + Al2O3 oxide mixture in the MgAl2O4 end-member. The majorite solid solution has the garnet structure and its composition varies, depending on the coexisting phases. The Al2O3 content of the γ phase is very low (-0.8wt%), so the Al2O3 content of the Mg2SiO4-MgAl2O4 system may not significantly affect the phase boundary of the post-spinel transformation because of very limited Al2O3 solubility in Mg2SiO4-spinel.

关 键 词：高温高压 相变 镁铝硅酸盐固溶体 γ相超尖晶石转变 Mg2SiO4-MgAl2O4体系 固溶度 地球物理实验 

分 类 号：P578.94[天文地球—矿物学] O521[天文地球—地质学]