摘要
根据 X射线衍射分析结果 ,对东太平洋地区始新世末—渐新世初的地层进行了矿物学研究。始新世末的含金属粘土层 ,矿物组合比较复杂 ,含有蒙脱石、磷灰石、针铁矿、重晶石、方英石、伊利石、斜长石、石英、斜发沸石、钙十字沸石等多种矿物 ,且该粘土层 (顶、底部除外 )不含方解石 ,说明它的沉积环境处在方解石补偿深度以下 ,突变的海洋沉积环境和含金属粘土层中有微玻璃陨石以及富含指示地外成因的 Ni、Co、Ir等亲铁元素的存在 ,推测该含金属粘土层的成因与陨击作用有关。
We studied mineral charateristics around the bound between Eocene and Oligocene according to examples from site 573 provided by ODP.There are 6 layers(1,2,3,4,5 and 6)from up to down.About 30% of black angular glassy matters are contained in layer 2(the nanno chalk containing glass).Its chemical compositions are like those of alkaline basalt,but the Ir is quite high(0 49～0 85%)according to EPMA.Whether they are formed by a volcano or by a meteorite impact needs to be researched further. Layer 4,the boundary layer of Eocene and Oligocene is a layer of metalliferous claystone about 3 4 m thick.It has a complexed mineral combination and 10 or more types of minerals such as quartz,cristobalite,barite,illite,apatite,clinoptilolite,phillipsite,montmorillonite,geothite and homblendite,and calcite is contained only at top and bottom.Abundant Fe element and Fe group elements such as Ni,Co and Ir are contained in the layer.Microtektites are also found in the layer,especially in the bottom of it.These characteristics show that the formation of the metalliferous claystone may have some relationship with meteorite impact. According to the mineral charateristics of the strata between late Eocene and early Oligocene,the distribution of microtektites,the extinction of many organisms,the fluctutions of the calcite compensation depth and so on,we infer that a catastrophic event from a meteorite impact might occur at the end of Eocene.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2000年第1期15-22,共8页
Marine Geology & Quaternary Geology
基金
国家自然科学基金资助项目!( 4 97762 94)
