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在t=1100-1500℃和P=0-2.88GPa条件下,实验确定了与金属Cr平衡的SiO_2-Cr-O及MgO-SiO_2-Cr-O体系中的亚固相相关系。结果显示,在SiO_2-Cr-O体系中,只发现绿铬矿-金属铬-石英(或鳞石英)组合;而在含MgO体系中,出现Mg-Cr~(2+)橄榄石、辉石及尖晶石固溶体。Cr~(3+)在橄榄石和辉石中的含量在可测定限度之下。当X_(Cr~(2+))=[Cr~(2+)/(Mg+Cr~(2+))]>0.2时,辉石的结构由斜方晶系转为单斜晶系;尖晶石的结构由立方变为四方。对实验数据进行热力学模拟,求得Mg-Cr~(2+)在橄榄石,辉石及尖晶石固溶体中的混合参数(W),以及铬橄榄石(Cr_2SiO_4)、铬辉石(Cr_2Si_2O_6)和铬尖晶石(Cr_3O_4)的形成自由能(△G°)与温度的关系。
Under the conditions of t = 1100-1500 ℃ and P = 0-2.88GPa, the relationship between the subsolidus phases in SiO_2-Cr-O and MgO-SiO_2-Cr-O systems with the equilibrium of metal Cr was experimentally determined. The results show that in the SiO_2-Cr-O system, only the green chrome-chrome-quartz (or tridymite) assemblage is found. In MgO-containing systems, Mg-Cr 2+ olivine and pyroxene And spinel solid solution. The content of Cr 3+ in olivine and pyroxene is below the limit of determination. The structure of pyroxene changed from orthorhombic to monoclinic when X Cr Cr 2 + / Cr + 2 + Spinel structure from cubic to Quartet. The thermodynamic simulation of the experimental data obtained Mg - Cr ~ (2) in the olivine, pyroxene and spinel solid solution of the mixing parameters (W), and chrome olivine (Cr 2 SiO 4), chrome pyroxene (Cr 2 Si 2 O 6) And the formation of chromium spinel (Cr_3O_4) free energy (△ G °) and temperature.