| 西藏丁青地区与玻镁安山岩类有关的蛇绿岩的矿物学特征 |
| |
| 引用本文： | 李达周,张旗,张魁武.西藏丁青地区与玻镁安山岩类有关的蛇绿岩的矿物学特征[J].岩石矿物学杂志,1988,7(3):235-243. |
| |
| 作者姓名： | 李达周 张旗 张魁武 |
| |
| 作者单位： | 中国科学院地质研究所
(李达周，张旗)，中国科学院地质研究所(张魁武) |
| |
| 摘 要： | 西藏丁青蛇绿岩的东杂岩体是一种与玻镁安山岩(Boninite)有关的特殊的蛇绿岩类型。其 堆晶斜方辉石岩、辉长岩和辉绿岩的岩石化学、微量元素以及稀土元素的地球化学特征均与西太平洋诸岛(伊豆—马利亚纳、巴布亚新几内亚、新喀里多尼亚等)的玻镁安山岩相似。此外,超镁铁质构造岩中的橄榄石和顽火辉石富镁,指示残余地幔具强烈亏损的性质。尖晶石的Cr含量中等至较高,与深海橄榄岩及大洋中脊玄武岩中的尖晶石不同。堆晶岩和辉长岩中的古铜辉石富镁,斜长石富钙,也明显不同于典型大洋中脊环境的特征,表明丁青东蛇绿岩形成的环境不像大洋中脊或弧后盆地,而可能是在洋内俯冲带之上的岛弧底部。
|
| 关 键 词： | 玻镁安山岩 超镁铁质构造岩 正堆晶结构 补堆晶结构 异堆晶结构 |
Mineralogical Characteristics of Ophiolite Related to Boninite rocks in Dengqen Area, Tibet |
| |
| Li Dazhou,Zhang Qi,Zhang Kuiwu.Mineralogical Characteristics of Ophiolite Related to Boninite rocks in Dengqen Area, Tibet[J].Acta Petrologica Et Mineralogica,1988,7(3):235-243. |
| |
| Authors: | Li Dazhou Zhang Qi Zhang Kuiwu |
| |
| Abstract: | Olivine and enstatite collected from harzburgite at the bottom of ophiolite in eastern Dngqn are rich in Mg (Fo= 91.3- 92.2, ave. 91.9; En= 87.9- 92.4, ave. 90.5). MgO content of both ol and opx is similar to that of most ophiolites in the world, but is higher than that of the abyssal peridotite, indicating that the source materials are likely to be very refractory. The Cr/(Cr+Al) ratios of spinel from harzburgite range from 0.56 to 0.66, which are also higher than those of abyssal peridotite (lower than 0.6), suggesting higher degree of partial melting for harzburgite from Dngqn. In cumulate ultramafic rocks, olivine is absent, whereas orthopyroxene (bronzite) is dominant. Bronzite has higher MgO content in comparison with other types of ophiolite and is associated with both Ca-rich plagioclase and quartz, implying that the primary magma might be boninitic magma rich in SiO_2, MgO and poor in TiO_2, Na_2O as compared with MORB. Experiments show that the associations of both Opx+ Pl and Opx + Cpx + Pl seen to have features of high pressure reaction relative to those of plutonic rocks (cumulate or non-cumulate) beneath mid-oceanic ridge. Mineralogical study suggests that ophiolite and boninite in Dngqn are genetically related to each other. The Dngqn ophiolite represents part of plutonic rocks related to boninite and occurs probably on the bottom of intraoceanic island arc, similar to things in the island arcs of western pacific ocean. |
| |
| Keywords: | Dengqen area boninite rocks ophiolite ultramafic tectonite orthocumulate texture adcumulate texture heteradcumulate texture |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《岩石矿物学杂志》浏览原始摘要信息 |
| 点击此处可从《岩石矿物学杂志》下载免费的PDF全文 |
|
