Alexander E. Romashkin

Two-billion-year-old evaporites capture Earth’s great oxidation

A strongly oxidizing Paleoproterozoic era Two billion years ago, marine sulfate concentrations were around one-third as high as modern ones, constituting an oxidizing capacity equivalent to more than 20% of that of the modern ocean-atmosphere system. Blättler et al. found this by analyzing a remarkable evaporite succession more than 1 billion years older than the oldest comparable deposit discovered to date. These quantitative results, for a time when only more qualitative information was previously available, provide a constraint on the magnitude and timing of early Earths response to the Great Oxidation Event 2.3 billion years ago. Science, this issue p. 320 The oxidizing capacity of the ocean was one-fifth of modern values in the Paleoproterozoic era. Major changes in atmospheric and ocean chemistry occurred in the Paleoproterozoic era (2.5 to 1.6 billion years ago). Increasing oxidation dramatically changed Earth’s surface, but few quantitative constraints exist on this important transition. This study describes the sedimentology, mineralogy, and geochemistry of a 2-billion-year-old, ~800-meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 meters) followed by units dominated by anhydrite-magnesite (~500 meters) and dolomite-magnesite (~200 meters). The evaporite minerals robustly constrain marine sulfate concentrations to at least 10 millimoles per kilogram of water, representing an oxidant reservoir equivalent to more than 20% of the modern ocean-atmosphere oxidizing capacity. These results show that substantial amounts of surface oxidant accumulated during this critical transition in Earth’s oxygenation.

6.2 The Pechenga Greenstone Belt

Geology and stratigraphy of the Pechenga Greenstone Belt is described in detail in Chap. 4.2. The brief geological outline presented here provides a scientific context and background information for the FAR-DEEP implemented in this area.

7.7 The Earliest Phosphorites: Radical Change in the Phosphorus Cycle During the Palaeoproterozoic

Phosphate is an essential and growth-limiting nutrient required by all forms of life, as it is a key component of many important macro-molecules. These macro-molecules are involved in energy transport, information storage, and structural support functions include membrane lipids, proteins, and nucleic acids. The global phosphorus cycle, which includes only dissolved and solid phases without any gaseous components, is strongly influenced by biological processes (Gulbrandsen 1969; Jahnke 1992; Follmi 1996). Continental weathering and riverine discharges are the most important sources delivering both particulate and dissolved phosphate into the oceans (Froelich et al. 1982; Follmi 1995). Long-term changes in the phosphorus cycle, such as variations in sources, concentration of dissolved seawater phosphate, formation of phosphorite deposits, and sequestration in biomass, are linked with other biogeochemical cycles and track major changes in Earth’s environmental conditions (Sheldon 1980; Baturin 1982; Papineau 2010; Planavsky et al. 2010). Biologic influence upon the phosphorus cycle can be traced back to the early Archaean (Blake et al. 2010). Ancient biologic processing of phosphate is inferred from the oxygen isotope ratios of some phosphates in 3200–3500 Ma sediments that are similar to those of modern marine biogenic phosphates (Blake et al. 2010).

The Tulomozero Formation: FAR-DEEP Holes 10A and 10B

The main geological and stratigraphic features of the Onega Basin are discussed in Chap. 4.3. Given here is a brief geological outline to provide a scientific context and background information for the FAR-DEEP implemented in this area.

The Imandra/Varzuga greenstone belt

The Late Archaean-Early Palaeoproterozoic transition (2500–2000 Ma) represents a hallmark period when the Earth System experienced a series of fundamental upheavals. Among them, the most important was the establishment of an oxygen-rich atmosphere (sometimes referred to as the Great Oxidation Event) and the emergence of an aerobic biosphere. Associated with this, either incidentally or causally, was a cascade of other prominent, global-scale events that considerably modified Earth’s surface environments, either temporarily or permanently; these are reviewed in Parts 1 and 8 in full, and detailed in Part 7. Briefly mentioned here, these include: the severe and global climatic event known as the Huronian glaciation; an unprecedented perturbation of the global carbon cycle, the large-magnitude Lomagundi-Jatuli positive excursion of δ13Ccarb, lasted over 160 Ma; radical changes in the phosphorus and sulphur cycles resulting in accumulation of the first-known massive sulphates and sedimentary phosphates; a radical modification in recycling of organic matter leading to the emergence of a new 13C-depleted carbon reservoir in the form of carbonate concretions; and an unprecedented accumulation of organic-rich sediments and formation of the earliest supergiant petroleum deposits.

Polisarka sedimentary formation: FAR-DEEP hole 3A

The Late Archaean-Early Palaeoproterozoic transition (2500–2000 Ma) represents a hallmark period when the Earth System experienced a series of fundamental upheavals. Among them, the most important was the establishment of an oxygen-rich atmosphere (sometimes referred to as the Great Oxidation Event) and the emergence of an aerobic biosphere. Associated with this, either incidentally or causally, was a cascade of other prominent, global-scale events that considerably modified Earth’s surface environments, either temporarily or permanently; these are reviewed in Parts 1 and 8 in full, and detailed in Part 7. Briefly mentioned here, these include: the severe and global climatic event known as the Huronian glaciation; an unprecedented perturbation of the global carbon cycle, the large-magnitude Lomagundi-Jatuli positive excursion of δ13Ccarb, lasted over 160 Ma; radical changes in the phosphorus and sulphur cycles resulting in accumulation of the first-known massive sulphates and sedimentary phosphates; a radical modification in recycling of organic matter leading to the emergence of a new 13C-depleted carbon reservoir in the form of carbonate concretions; and an unprecedented accumulation of organic-rich sediments and formation of the earliest supergiant petroleum deposits.

Structure and optical properties of PECVD-prepared As-Se-Te chalcogenide films designed for the IR optical applications

For the first time films of the As-Se-Te (15≤As≤40, 30≤Se≤65, 5≤Te≤30) chalcogenide system have been prepared by Plasma-Enhanced Chemical Vapor Deposition (PECVD) at low pressure (0.1 Torr). RF (40 MHz) inductively coupled non-equilibrium plasma discharge has been chosen as the initiator of chemical interaction between precursors. Elemental As, Se, and Te of high-purity were used as the initial substances. High-pure argon was utilized as career gas as plasma feed gas. The obtained chalcogenide planar materials have been studied in terms their physical-chemical properties. The films were modified by continuous and femtosecond laser irradiation.

6.1 The Imandra/Varzuga Greenstone Belt

The Late Archaean-Early Palaeoproterozoic transition (2500–2000 Ma) represents a hallmark period when the Earth System experienced a series of fundamental upheavals. Among them, the most important was the establishment of an oxygen-rich atmosphere (sometimes referred to as the Great Oxidation Event) and the emergence of an aerobic biosphere. Associated with this, either incidentally or causally, was a cascade of other prominent, global-scale events that considerably modified Earth’s surface environments, either temporarily or permanently; these are reviewed in Parts 1 and 8 in full, and detailed in Part 7. Briefly mentioned here, these include: the severe and global climatic event known as the Huronian glaciation; an unprecedented perturbation of the global carbon cycle, the large-magnitude Lomagundi-Jatuli positive excursion of δ13Ccarb, lasted over 160 Ma; radical changes in the phosphorus and sulphur cycles resulting in accumulation of the first-known massive sulphates and sedimentary phosphates; a radical modification in recycling of organic matter leading to the emergence of a new 13C-depleted carbon reservoir in the form of carbonate concretions; and an unprecedented accumulation of organic-rich sediments and formation of the earliest supergiant petroleum deposits.