Geochemistry of Cretaceous black shales from the Atlantic Pcean (DSDP Legs 11, 14, 36 and 41)☆
Geochemistry of Cretaceous black shales from the Atlantic Pcean (DSDP Legs 11, 14, 36 and 41)☆
复制标题
大西洋白垩纪黑色页岩地球化学（DSDP Legs 11、14、36 和 41）☆
DOI：
10.1016/0009-2541(80)90064-9
复制
发表时间：
1980
期刊：
影响因子：
3.9
通讯作者：
H. Brumsack
中科院分区：
文献类型：
--
作者：
H. Brumsack
来自大西洋的88个白垩纪沉积物样品其中有机碳含量大于1%的黑色页岩样品38个，主要采用光谱法分析（相对标准偏差2-15%）的元素Fe，Mn，S，Zn，Cu，Cr，Pb，Ni，Co，Mo，V，Ba和Sr，以及在选定的样品中的Ag，Cd，Tl，Bi和B.重金属相对于平均页岩的高积累（因子高达330）不能用以下过程来解释：（1）受大陆径流控制的边缘盆地水组成;（2）与洋脊火山作用有关的热液;（3）海洋生物的代谢作用。（Pb < Co < Cr < Ni < Cu < V < Zn < Mo < Ag）与正常海水中这些元素浓度的增加有很好的对应关系（Ag除外）。硫的δ 34 S分析表明硫的细菌来源。黄铁矿与其它重金属硫化物不处于同位素平衡状态。这表明重金属硫化物在水柱中形成，黄铁矿在沉积物中形成。白垩纪的原始大西洋可以与现在的黑海的纯质阶段相比较。模型计算表明，正常的生产率是足够的解释相对较高的有机碳含量（高达35%）。在相对较短的停滞期（1-10 Ma）内，大量的有机碳（7.1013 t）、硫（2.1013 t）和重金属（9.1.1011 − 5.109 t）被固定在黑色页岩中。
Eighty-eight samples of Cretaceous sediments from the Atlantic Ocean (DSDP Sites 105, 135, 137, 138, 144, 330, 367, 368 and 370), including 38 black shale samples with organic C contents of more than 1% were analysed mostly by spectrometric methods (relative standard deviation 2–15%) for the elements Fe, Mn, S, Zn, Cu, Cr, Pb, Ni, Co, Mo, V, Ba and Sr, and in selected samples for Ag, Cd, Tl, Bi and B.The high accumulation of heavy metals relative to average shale (factors up to 330) cannot be explained by the following processes: (1) water composition of marginal basins controlled by continental runoff, (2) hydrothermal solutions connected with ridge volcanism, or (3) metabolism of marine organisms.The order of heavy-metal enrichment relative to average shale (Pb < Co < Cr < Ni < Cu < V < Zn < Mo < Ag) corresponds well (except Ag) with the increasing concentration of these elements in normal seawater.The presence of pyrite, sphalerite and Cu-sulfides could be demonstrated by microprobe scanning. The bacteriogenic origin of sulfur could be recognized by δ34S analysis. Pyrite and the other heavy-metal sulfides were not in isotopic equilibrium. This is an indication of the heavy-metal sulfides being formed in the water column and pyrite in the sediments.The Cretaceous Proto-Atlantic can be compared to the present euxynic stage of the Black Sea. Model calculations show that a normal productivity is sufficient for the explanation of the relatively high organic C content (up to 35%). During relatively short periods of stagnation (1–10 Ma) considerable amounts of organic carbon (7 · 1013t), sulfur (2 · 1013t) and heavy metals (9.1 · 1011−5 · 109t) had been fixed in the black shales.