摘要
在幔源矿物的流体组分中含有一定数量的H_2,这些H_2在地球演化过程及地幔动力体系中起着十分重要的作用,其在幔源矿物中的赋存状态具重要的研究价值。本文用真空分步加热质谱法测定了河北大麻坪幔源二辉橄榄岩捕虏体中橄榄石、斜方辉石和单斜辉石中H_2的释放量,根据其与样品破碎粒度、加热温度及挥发份总量间的关系,辅以红外吸收光谱,认为幔源矿物中H_2的赋存状态以气液包裹体(特别是早期气液包裹体)为主,矿物结构中OH的比例相对较少。
Fluids in mantle-derived minerals contain a certain amount of H2, which played a very important role in the evolution of the Earth and the mantle dynamic system and whose mode of occurrence in the mantle-derived min-erals is of great value in the study of mantle fluids. In this paper the H2 content released from olivine, orthopy-roxene and clinopyroxene of mantle xenoliths in Damaping, Hebei Province, has been determined by the vacu-um stepwise-heating mass spectrometry and the results indicate that the released H2 content changes syn-chronously with the total amount of volatile released from the sample with increasing temperature and that both of them show gas-released peaks at the same heating temperature intervals (300~400℃ and 700~900℃ ) In-frared absorption spectrometry suggests that after gases are released at 600℃ and 900℃, the OH absorption peak (3400 cm-1) shows no obvious reduction. The amount of H2 released from olivine increases rapidly with decreasing grain size of the crushed sample and orthopyroxene and clinopyroxene show the optimal grain size for H2 release with decreasing grain size of the crushed sample. Based on the relationships between the H2 amount released from samples and the grain size of the sample, heating temperatures, the total amount of volatiles and infrared absorption spectra, it is considered that H2 in mantle-derived minerals occurs mainly in gas-liquid inclu-sions (especially in early-stage gas-liquid inclusions with better closure) and secondarily in the form of structural hydroxyl (OH) in mantle-derived minerals.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2002年第1期39-44,共6页
Acta Geologica Sinica
基金
国家自然科学基金资助项目(编号49233060
49133090)
