Thermomagnetic evidence of native iron in sediments

Abstract

The paper summarizes the results of thermomagnetic analysis concerning the distribution of metallic iron in the sediments ranging in age from Miocene to Early Cretaceous sampled from the following sections: Gams (Austria); Verkhorech'e and Sel'bukhra (the Crimea); Kvirinaki and Tetritskaro (Georgia); Aimaki, Dzhengutai, Madzhalis, and Gergebil (Ciscaucasia, Russia); Klyuchi and Teplovka (Volga region, Russia); Koshak (Kazakhstan); and Khalats and Kara Kala (Turkmenia). Small amounts of native iron (from 10 -5 % to 0.05%) are identified in 521 samples of 921 studied; i.e., iron particles are almost pervasive. This fact traces the origin of these particles to cosmic dust. Some established features point to the heterogeneous char acter of the cosmic dust: (a) the samples clearly fall into two groups. One group comprises the rocks that con tain iron particles; the rocks of the other group are iron free. In the first group, four intervals are distinguished where the sediments are globally enriched with iron with constant nickel content (5-6%); (b) in terms of composition, the iron particles are divided into three groups. The first group contains pure iron; the particles pertaining to the second group contain iron with a minor amount of nickel typical for kamacite; and the third group comprises the particles of Fe Ni alloy with more than 20% nickel. The first and the second groups are ubiquitous; the particles of the third group are spread locally. They bear no relation to cosmic dust and are probably associated with the meteoritic impacts.

Extraterrestrial Metallic Iron in the Lacustrine, Epicontinental and Oceanic Sediments: A Review of Thermomagnetic and Microprobe Analyzes Data

“…scatter of the data is controlled by the degree of redeposition of iron particles and their probable terrestrial origin, i.e., the situations when these particles participate in the accumulation of the sediments just as the terrestrial particles. In our case, this is reflected by the coefficients of the linear correlation between the concentrations of iron particles and magnetite of 0.3-0.6 [9]. In contrast to the general trend, at the points that are related to the redeposition (the open circles in Figure 17), the dependence of the size of the zero group and the rate of sedimentation vanishes.…”

“…In contrast to the general trend, at the points that are related to the redeposition (the open circles in Figure 17), the dependence of the size of the zero group and the rate of sedimentation vanishes. In the case of terrestrial native iron, we should expect the distribution to follow the Poisson zero-mode distribution, which is supported by the single-mode distribution of the magnetite content having knowingly terrestrial origin in the same sediments [9,10]. The absence of a correlation between the concentrations of terrestrial magnetic minerals (e.g., magnetite) and the rate of sedimentation is clearly seen in Figure 18.…”

“…Against the scatter of the data, it is clearly seen that the zero group tends to increase with an increase in the sedimentation rate (Figure 17). In particular, the [5,9] (c) a metal part of the meteorites [5,9]. N-the number of definitions.…”

“…In recent years, we have studied the spreading and composition of metallic iron particles in the Pleistocene lacustrine sediments of the Darhad Basin, northern Mongolia, in the Upper Miocene sediments of Lake Baikal, in epicontinental sediments of Miocene, Oligocene, Eocene, Cretaceous, Late Jurassic, and Early Cambrian age in different regions of North Eurasia and in ocean sediments of the NorthWestern Atlantic [4][5][6][7][8][9][10]. This article represents a result of a review and generalization of thermomagnetic and microprobe analyzes data for mentioned above articles and regions.…”