碧溪岭石榴石橄榄岩的橄榄石中针状磁铁矿出溶体成分的不均匀性  

The compositional inhomogeneity of the needle-exsolution magnetites in olivine from Bixiling garnet peridotite

作　　者：赵文霞[1] 胡育贤[1] 李雪梅[1] 廖成竹[1] 杜金菊[1] 江丹[1] 

机构地区：[1]中山大学测试中心电镜室,广东广州510275

出　　处：《岩石矿物学杂志》2006年第1期40-44,共5页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目(49602035);中山大学青年教师启动基金

摘　　要：运用电子探针Map图分析技术在碧溪岭石榴石橄榄岩的橄榄石中发现了磁铁矿针状出溶体成分不均匀的现象,即同一岩石样品的橄榄石中针状出溶体既有前人发现的含钛铬磁铁矿,也有本文发现的含铬钛磁铁矿和磁铁矿两种针状出溶体。研究认为,针状出溶体成分出现的差异可能是由于Ti和Cr在原始的β_橄榄石相中分布不均匀所致,这种出溶体的出现暗示这些橄榄石可能是由地幔特有的尖晶石结构相转变而成,为确定这些橄榄岩的来源深度和大陆俯冲过程提供了有意义的信息。Compositional inhomogeneity of the needle-exsolution magnetites in olivine from Bixiling garnet peridotite was recognized by means of map analysis using electron probe microanalysis （EPMA）. Some needle-exsolution magnetites have relatively high Cr concentration, whereas others have relatively high Ti concentration. It is suggested that the distribution of titanium and chromium might have been inhomogenous in the original β- olivine-phase, resulting in the compositional difference observed in the needle-exsolution magnetites. This implies that the olivine originally existed as spinel-phase which was stable in the mantle. The present study therefore provides valuable information for determining the formation depth of the garnet peridotite and for understanding the mechanism of continental subduction.

关 键 词：针状磁铁矿出溶体 橄榄石 电子探针Map图 碧溪岭 石榴石橄榄岩 

分 类 号：P578.4[天文地球—矿物学] P588.125[天文地球—地质学]