新疆洪古勒楞蛇绿岩套中辉石化学成分研究  

STUDY ON THE CHEMICAL COMPOSITIONS OF PYROXENES IN THE HONGGULELENG OPHIOLITE,XINJIANG

作　　者：白文吉[1] 周美付[1] 

机构地区：[1]中国地质科学院地质研究所

出　　处：《地质论评》1989年第2期107-118,共12页Geological Review

摘　　要：洪古勒楞蛇绿岩层序出露较齐全,在岩石中保存了比较新鲜的造岩矿物。本文以电子探针分析数据为基础,讨论了其中辉石的化学成分特征,证明辉石化学成分受寄主岩石类型的制约:但在同一寄主岩石中,单斜辉石比斜方辉石富含较多的TiO_2、MnO和Cr_2O_3。统计分析表明,从蛇绿岩的底部到顶部,二种辉石的化学成分有相同的变化趋势:从富Cr_2O→MgO→Na_2O、K_2O→NiO→FeO→TiO_2、MnO。根据辉石的化学成分特征提出堆积岩可能为岩浆堆积成因的观点。Pyroxenes in the Hongguleleng ophiolite have been weakly altered. This paper deals with their chemical compositions. Orthopyroxene in the chromite ore and harzburgite is rich in 'En', but that in the cumulative complexes is rich in 'Fs', so the chemical composition of the orthopyroxene is related to its host rock. The chemical composition of the clinopyroxene shows a wide variation, but it is rich in 'Fs' in the volcanic rocks or diabase. In the same host rock, the clinopyroxene contains more TiO_2, MnO and Cr_2O_3 than the orthopyroxene. Statistic analysis indicates that the order of chemical composition variation of the pyroxenes is Cr_2O_3→MgO→Na_2O→K_2O→NiO→FeO→TiO_2 and MnO from the bottom to the top of the ophiolite. In the clinopyroxene, the negtive correlation of Al and Si content indicates that part of Al have replace Si and come into the tetrahedral site, but in the orthopyroxene Al into the octahadral site. Fe/Mg variations of the coexisting pyroxene pair are in positive correlation. The K_D value is 1.26—1.61, coincident with magmatic origin of pyroxenes. The characteristics of chemical compositions of the pyroxenes provide evidence for the origin of magma cumulation of the cumulate.

关 键 词：蛇绿岩套 辉石 矿物化学成分 

分 类 号：P578.954[天文地球—矿物学]