不同大地构造背景橄榄岩结构水特征

名义无水矿物(NAMs)中的结构水在地球内部演化中扮演了重要角色.应用红外光谱对产自5个构造背景下的13个二辉橄榄岩进行了详细的结构水测定,探讨不同构造背景下橄榄岩结构水的含量和赋存机制.研究显示,全岩和橄榄石结构水含量按构造背景从高到低排序,依次为超高压地体、地幔柱、稳定克拉通、俯冲带和活化克拉通,反映了橄榄岩的水含量与构造环境具有显著相关性.在相同构造背景下,石榴石二辉橄榄岩比尖晶石二辉橄榄岩含更多结构水,表明上地幔水分布可能具有分层性.超高压地体和稳定克拉通样品中橄榄石具有Si]空位导致的吸收峰3 611~3 613 cm-1,而缺乏由Fe3+]引起的吸收峰3 325 cm-1和3 355 cm-1,表明地幔的还原性随深度增强. 

Characteristics of Hydroxyl in Lherzolite from Different Geological Setting

Hydroxyl in minerals from upper mantle peridotite plays an important role in the evolution of the earth's interior. In order to understand the correlation between geological setting and hydroxyl incorporation in lherzolite,OH contents of 13 garnet/spinel lherzolite samples from different geological settings (i.e. stable craton,reactivated craton,mantle plume,subduction zone and UHP terrane) were investigated by fourier transform infrared (FTIR) spectroscopy analysis. The results demonstrate: (1) water contents in olivine and bulk rock follow the trend of UHP terrain >mantle plumb>stable craton >subduction zone >activated craton; (2) garnet lherzolite contains more water than that of spinel lherzolite for samples from the same geological setting,indicating that the upper mantle should be stratified with depth in terms of water distribution; (3) the presence of Si] deficiency-caused IR peaks at 3 611-3 613 cm-1 together with the absence of Fe3+] caused peaks at 3 325 cm-1 and 3 355 cm-1 indicates the upper mantle is more reduced with increasing pressure.