摘要
本文对贺根山、鲸鱼、东巧、罗布莎、玉石沟等地超镁铁岩中(L-C)蛇纹岩标本的氢、氧同位素组成进行了分析,其变化范围为:δD=-101—-146,δ^(18)O=1.0—7.5。产生蛇纹石化作用时平衡计算水的氢、氧同位素为:330℃时δD=-77—-122,δ^(18)O=1.4—7.9;200℃时δD=-67—-112,δ^(18)O=-1.3—5.2。根据大洋型(L-C)蛇纹岩和大陆蛇绿岩杂岩型(L-C)蛇纹岩的氢、氧同位素组成特征来看,本文所研究的蛇纹岩明显地属于大陆蛇绿岩杂岩型蛇纹岩。蛇纹石化时平衡计算水的氢、氧同位素特征表明水的成因类型为大气降水型地下水,而非大洋水。本文中超镁铁岩的蛇纹石化作用发生在超镁铁岩侵位于大陆壳之后,即超镁铁岩的蛇纹石化作用发生于大陆环境,而非大洋环境,而且超镁铁岩在侵位于陆壳之后的最初阶段应为新鲜的地幔岩石。
Hydrogen and oxygen isotopic compositions were measured on some(L-C) serpentinite samples of ultramafic rocks from Hegenshan, Jingyu, Dong-qiao, Tuobusha in China: δD= -101--146, δ~18O = 1.0--7.5. Estimatesof the isotopic compositions of waters, that produced the serpentinizationof ultramafic rocks in the present work range: δD= -77--122, δ~18O= 1.4-4.9 at 330℃. According to difference of isotopic compositions (Wenner, D. B. andTaylor, H. P., 1973) between oceanic (L-C) serpentines (δD_R= -35--68,δ~18O_R= +0.8--6.7; δD_w= +5--30, δ~18O_w= -2-- +3) and (L-C) serpenti-nes of continental ophiolite complexes (δD_R= -80--149, δ~18O_R= 6.3--9; δD_w= -35--115, δ~18O_w= -7-- +18) serpentines ullustrated in this paperevidently belong to the latter. The characteristics of isotopic compositions of waters involved in suchserpentinization suggest, that waters in (L-C) serpentinites ullustrated in thispaper probably formed from hot meteoric ground waters. The peridotitesmay only become heavily serpentinised after their emplacement in acontinental environment.
出处
《岩石矿物学杂志》
CAS
CSCD
1992年第2期111-119,T001,共10页
Acta Petrologica et Mineralogica
基金
国家自然科学基金委员会资助项目
关键词
超镁铁岩
蛇纹石
水
非大洋型
成因
δD
δ^(18)O
serpetinization
continental ophiolite complexes
oceanic environments
ultramafic rocks
