摘要
利用穆斯堡尔谱仪对辽宁宽甸地幔岩包体中的矿物进行了三价铁的测定,测试结果与国内外已发表的数据接近。Fe3+/∑Fe比值分别为:斜方辉石0066~0196,单斜辉石0216~0344,尖晶石0283~0299,石榴石0057~0223。依据电价平衡原理计算的Fe3+含量受Si4+、Al3+和Cr3+的电子探针分析误差影响很大。根据地幔矿物的电子探针分析结果计算平衡温度、压力和氧逸度时,二辉石En、Ca转移反应温度计和石榴石斜方辉石Al压力计的计算结果不超过温压计的一般误差范围,而石榴石单斜辉石Fe2+Mg交换反应温度计在忽略Fe3+时计算的温度值可偏高100℃以上;采用橄榄石/斜方辉石/尖晶石组合氧压力计计算的氧逸度值,误差一般约在±07个对数单位。
erric iron contents of coexisting minerals from four mantle xenoliths, collected from Kuandian, Liaoning Province, were measured by Mssbauer spectroscopy and found to be similar to the published data from domestic and overseas. The ratios of Fe 3+ /∑Fe are 0066~0196 in orthopyroxenes, and 0216~0344, 0283~0299 and 0057~0223 in clinopyroxenes, spinels and garnets respectively. Comparison of Mssbauer and microprobe analytical results shows that Fe 3+ values calculated from microprobe data are significantly effected by analytical uncertainty of Si 4+ ,Al 3+ and Cr 3+ . In terms of equilibrium temperature, pressure and oxygen fugacity calculated from electron microprobe analyses of mineral compositions, the results estimated from orthopyroxene clinopyroxene En and Ca transfer reaction geothermometers and garnet orthopyroxene Al geobarometers are reliable with uncertaines less than 30℃ for temperature and 01~04GPa for pressure. Garnet clinopyroxene Fe 2+ -Mg exchange reaction geothermometers usually overestimate temperatures as higher as 89~166℃. The comparatively reliable oxygen fugacity values can be obtained from olivine orthopyroxene spinel oxybarometers with uncertainties around±07 log units.
出处
《现代地质》
CAS
CSCD
北大核心
1998年第2期197-203,共7页
Geoscience
基金
国家教委"跨世纪优秀人才计划"基金
关键词
地幔岩包体
穆斯堡尔谱
电子探针
矿物
三阶铁
mantle xenolith, Mssbauer spectroscopy, electron microprobe, geothermobaro meter, oxybarometer