Geochemical study of Cretaceous-Teratiary (K-T) boundary layers in Turkey

在这项研究中，我们总结了土耳其Medetli和其他部分K-T边界层的元素和Sr同位素剖面。结合1999年和2000年的研究成果，对Medetli剖面进行了元素和Sr同位素剖面的研究。Medetli剖面由A、B、C层组成：A层为最晚白垩纪，C层为最早第三纪，B层为K-T界线。在B层中含有较薄的针铁矿富集层，Fe、Mn、Cr、Ni、V、Cu、Co等金属元素在针铁矿富集层中富集。此外，As、Sb和Zn的浓度在层中是高的。Medetli富针铁矿层的这些元素特征与世界著名的K-T界线剖面十分相似。我们还试图测量富针铁矿层中的Ir浓度，但没有测定出高浓度的Ir。浓度为0.07-0.08 ppb。这一结果与该层为K-T复层的结论不一致。然而，它也可能是铱在沉积后的成岩作用期间被稀释。Sr同位素结果表明，A层Sr比值较高（0.710-0.711），而B层Sr比值降低（0.7078 ~ 0.7080）。针铁矿富集层的Sr同位素比值与B层相同（0.7078-0.7080）。这些值与白垩纪末海水Sr同位素值接近。这说明海水Sr在B层和针铁矿富集层中沉淀较多。在本研究中，没有获得铱富集的有力证据，但铱可能在沉积后的成岩作用中被稀释或消失。我们必须对这个问题作进一步的研究。在Haymana剖面和Devrekani剖面，金属元素富集于K-T界面。作为相关研究，我们对日本西南部冲岛的镁铁质火成岩和蒙古中部晚古生代花岗岩进行了地球化学研究。我们在已发表的论文中报告了结果。

In this study, we summarize the element and Sr isotope profiling of K-T boundary layers in Medetli and other sectins in Turkey. Combining the results of 1999 and 2000 researches, we made element and Sr isotope profiles in Medetli section. Medetli section is composed of A, B and C layers : A is latest, Cretaceous and C is earliest Tertiary, and B is K-T boundary. In layer B thin goethite-rich layers are included and metal elements such as Fe, Mn, Cr, Ni, V, Cu, Co are enriched in goethite-rich layer. Also As, Sb and Zn concentrations are high in the layers. These element characteristics in goethite-rich layers in Medetli is very similar to famous K-T boundary sections in the world. We also tried to measure the Ir concentration in the goethite-rich layers, but no high concentrations of Ir was not determined. The concentrations are 0.07-0.08 ppb. This result is not consistent that this layer is just K-T bundary layer. However, it is also probable that Ir was diluted during diagenesis after sedimentation. Sr isotope results show that the ratios in layer A is high(0.710-0.711), but decrease 0.7078 to 0.7080 in layer B. The Sr isotope ratios in goethite-rich layers are the same in layer B(0.7078-0.7080). These values are close to sea water Sr isotope value of end of Cretaceous. This means that sea water Sr was much precipitated particular in layer B and goethite-rich layer. In this study strong evidence as enrichment of Ir was not obtained, but it is possible that Ir was diluted or disapeared during the diagenesis after sedimentation. We have to have further research in this problem. In Haymana and Devrekani sections metal elements are concentrated in the K-T boundaries.As related studies, we have studied geochemical studies for the mafic igneous rocks in Oki Dogo Island, SW Japan and late Paleozoic granitoids in central Mongolia. We reported the results in the published paper.