我国东南部地区深源包体矿物中Mg同位素比值的离子探针研究

SIMS STUDY ON Mg ISOTOPIC RATIOS IN MINERALS OF DEEP-SEATED XENOLITHS FROM EASTERN AND SOUTHERN CHINA

本文对产于我国东、南部地区新生代碱性玄武岩中尖晶石橄榄二辉岩和尖晶石二辉橄榄岩包体矿物,应用离子探针(SIMS)线性分析和深度分析方法,测定Mg同位素比值。从SIMS所揭示的深源包体矿物Mg同位素组成异常现象来看,可以为进一步探讨地幔矿物的物质来源与演化提供信息。

Mg isotopic ratios in the minerals of spinel-olivine websterite and spinel-lherzolite senoliths from Fujian, Hebei and Yunnan provinces were determined by secondary ion mass spectrometer (SIMS), revealing anomalous 28Mg/24Mg ratios. In comparison with the average value for the standard sample of terrestrial forsterite, the determined ratios are depleted by about 20-40%.SIMS linear analysis suggests a correlation between 26Mg anomaly and Al/Mg ra-tio, whereas SIMS depth analysis shows a homogeneous distribution of 26Mg within the mineral crystals.