Early Precambrian Research Articles

Fine tuned exploration of evolutionary relationships within the protein universe.

In the regime of domain classifications, the protein universe unveils a discrete set of folds connected by hierarchical relationships. Instead, at sub-domain-size resolution and because of physical constraints not necessarily requiring evolution to shape polypeptide chains, networks of protein motifs depict a continuous view that lies beyond the extent of hierarchical classification schemes. A number of studies, however, suggest that universal sub-sequences could be the descendants of peptides emerged in an ancient pre-biotic world. Should this be the case, evolutionary signals retained by structurally conserved motifs, along with hierarchical features of ancient domains, could sew relationships among folds that diverged beyond the point where homology is discernable. In view of the aforementioned, this paper provides a rationale where a network with hierarchical and continuous levels of the protein space, together with sequence profiles that probe the extent of sequence similarity and contacting residues that capture the transition from pre-biotic to domain world, has been used to explore relationships between ancient folds. Statistics of detected signals have been reported. As a result, an example of an emergent sub-network that makes sense from an evolutionary perspective, where conserved signals retrieved from the assessed protein space have been co-opted, has been discussed.

An Individual Amino Acid as a Possible Prebiotic Catalyst

AbstractBetter understanding how reactions have been catalyzed in the prebiotic world is important for better realizing how enzymes have evolved. The dominant hypothesis is that the first catalyst was an RNA molecule. It was also assumed that amyloid fibrils, self‐assembled by peptides or proteins, served as the first catalysts. However, debate still exists regarding which process occurred first: the polymerization of RNA or the synthesis of proteins. Here, we show that an individual amino acid, L‐3,4‐dihydroxyphenylalanine (DOPA), can act as a catalyst. This amino acid is the main constituent of mussel adhesion proteins that function in harsh conditions very similar to plausible prebiotic conditions. By tracing the hydrolysis of two compounds, p‐nitrophenylacetate and acetylcholine, we showed that DOPA catalyzes a reaction; we suggest its role as a prebiotic catalyst.

Prebiotic Organic Chemistry of Formamide and the Origin of Life in Planetary Conditions: What We Know and What Is the Future.

The goal of prebiotic chemistry is the depiction of molecular evolution events preceding the emergence of life on Earth or elsewhere in the cosmos. Plausible experimental models require geochemical scenarios and robust chemistry. Today we know that the chemical and physical conditions for life to flourish on Earth were at work much earlier than thought, i.e., earlier than 4.4 billion years ago. In recent years, a geochemical model for the first five hundred million years of the history of our planet has been devised that would work as a cradle for life. Serpentinization processes in the Hadean eon affording self-assembled structures and vesicles provides the link between the catalytic properties of the inorganic environment and the impressive chemical potential of formamide to produce complete panels of organic molecules relevant in pre-genetic and pre-metabolic processes. Based on an interdisciplinary approach, we propose basic transformations connecting geochemistry to the chemistry of formamide, and we hint at the possible extension of this perspective to other worlds.

Typical Characteristics of the Earth’s Magnetic and Gravity Fields Related to Global and Regional Tectonics

Abstract —We present a summary and analysis of current views on the magnetic and gravity fields of the Earth as a reflection of global and regional tectonic processes. The discussion concerns the probable interconnection between the distribution of the geomagnetic field characteristics, gravity anomalies and the manifestations of mantle plume magmatism as the most remarkable geologic indicator of deep geodynamics. We demonstrate that the distribution of the characteristics of the main geomagnetic field has a qualitative similarity to anomalies of the gravity field. Brief variations of the geomagnetic field are due to high-frequency oscillations in the ionosphere, do not affect the general state of the field, and are useless when considering issues of global tectonics. On the contrary, variations with long periodicities, first of all geomagnetic reversals, can be among the main indicators of the evolution of the geodynamo – the heat mechanism controlling the entire series of global tectonic processes. The frequency of reversals is determined by the intensity of mantle plumes that cause the cooling of the core, increase the convection rate in the asthenosphere, and respectively, the periodic changes in the tectonosphere. We assume the existence of three modes of behavior for this system. The first one corresponds to steady convection, in which reversals are extremely rare or do not happen at all. These episodes – superchrons – compose no more than 20% of the duration of the Phanerozoic. The second mode occurs significantly more often in the geologic history and is characterized by active convection with frequent reversals happening at least once every 5 Myr. Finally, the third mode, which is rare for the Phanerozoic but was probably more prevalent in the early Precambrian, corresponds to hyperactive turbulent convection, when the frequency of reversals reached 20 and possibly more during one million years. Although the demonstrated qualitative similarity in the position of extreme values of the main geomagnetic field, the centers of free air gravity anomalies, and manifestations of large igneous provinces does not yet have a credible explanation, we consider it to be fundamental and requiring special study and detailed elaboration.

Convective isolation of Hadean mantle reservoirs through Archean time

Although Earth has a convecting mantle, ancient mantle reservoirs that formed within the first 100 Ma of Earth's history (Hadean Eon) appear to have been preserved through geologic time. Evidence for this is based on small anomalies of isotopes such as 182W, 142Nd, and 129Xe that are decay products of short-lived nuclide systems. Studies of such short-lived isotopes have typically focused on geological units with a limited age range and therefore only provide snapshots of regional mantle heterogeneities. Here we present a dataset for short-lived 182Hf-182W (half-life 9 Ma) in a comprehensive rock suite from the Pilbara Craton, Western Australia. The samples analyzed preserve a unique geological archive covering 800 Ma of Archean history. Pristine 182W signatures that directly reflect the W isotopic composition of parental sources are only preserved in unaltered mafic samples with near canonical W/Th (0.07 to 0.26). Early Paleoarchean, mafic igneous rocks from the East Pilbara Terrane display a uniform pristine µ182W excess of 12.6 ± 1.4 ppm. From ca 3.3Ga onward, the pristine 182W signatures progressively vanish and are only preserved in younger rocks of the craton that tap stabilized ancient lithosphere. Given that the anomalous 182W signature must have formed by ca 4.5 Ga, the mantle domain that was tapped by magmatism in the Pilbara Craton must have been convectively isolated for nearly 1.2 Ga. This finding puts lower bounds on timescale estimates for localized convective homogenization in early Earth's interior and on the widespread emergence of plate tectonics that are both important input parameters in many physical models.

Banded iron formation from Antarctica: The 2.5 Ga old Mt. Ruker BIF and the antiquity of lanthanide tetrad effect and super-chondritic Y/Ho ratio in seawater

Here we report the first detailed geochemical data for Banded Iron-Formation (BIF) from Antarctica. Micro drill cores were taken from adjacent magnetite/haematite and metachert bands from the 2.5 Ga old Mt. Ruker BIF, Prince Charles Mountains, East Antarctica. Low concentrations of Al, Zr, Hf, and Sc reveal the purity of the samples. The chemical composition matches closely that of other early Precambrian BIF, except for an enrichment of Ni, and high Ba/Sr ratios in the metachert. Shale-normalized Rare Earths and Yttrium (REYSN) patterns show all the features of modern seawater such as depletion of light vs heavy REYSN, positive anomalies of LaSN, GdSN, and YSN (i.e. super-chondritic Y/Ho ratios) and the W-type lanthanide tetrad effect (LTE), but positive EuSN and no CeSN anomalies (and no positive Eu anomalies in chondrite-normalized REY patterns). This distribution is fully compatible with that of other pure Early Precambrian BIFs, suggesting high-temperature hydrothermal input of REY into seawater and a redox level of the atmosphere-hydrosphere system too reducing for Ce oxidation. The uniform, super-chondritic Y/Ho ratios in adjacent iron-oxide and metachert BIF bands most strongly suggest that the conspicuous banding does not result from post-depositional separation of an initially homogenous Fe-silicate precipitate, but argues for a primary origin of the banding. The super-chondritic Y/Ho ratios fit well within the range reported for other BIF worldwide, corroborating that positive Y anomalies, although possibly of smaller size than today, have always been a characteristic feature of seawater. The Mt. Ruker BIF further complements the set of Early Precambrian marine chemical sediments in which the W-type LTE has been observed, and demonstrates the antiquity of the LTE in seawater. These subtle features reveal that the distribution of the redox-insensitive REY in seawater did not change significantly over the almost 4 billion years geological record of seawater. The super-chondritic Y/Ho ratios and W-type LTE in this and other oxide-facies BIF are in marked contrast to the REY distribution in Modern and Cenozoic oxidic hydrogenetic ferromanganese crusts, pointing towards fundamentally different removal mechanisms of REY from Modern vs Early Precambrian seawater.

Ariel – a window to the origin of life on early earth?

Is there life beyond Earth? An ideal research program would first ascertain how life on Earth began and then use this as a blueprint for its existence elsewhere. But the origin of life on Earth is still not understood, what then could be the way forward? Upcoming observations of terrestrial exoplanets provide a unique opportunity for answering this fundamental question through the study of other planetary systems. If we are able to see how physical and chemical environments similar to the early Earth evolve we open a window into our own Hadean eon, despite all information from this time being long lost from our planet’s geological record. A careful investigation of the chemistry expected on young exoplanets is therefore necessary, and the preparation of reference materials for spectroscopic observations is of paramount importance. In particular, the deduction of chemical markers identifying specific processes and features in exoplanetary environments, ideally “uniquely”. For instance, prebiotic feedstock molecules, in the form of aerosols and vapours, could be observed in transmission spectra in the near future whilst their surface deposits could be observed from reflectance spectra. The same detection methods also promise to identify particular intermediates of chemical and physical processes known to be prebiotically plausible. Is Ariel truly able to open a window to the past and answer questions concerning the origin of life on our planet and the universe? In this paper, we discuss aspects of prebiotic chemistry that will help in formulating future observational and data interpretation strategies for the Ariel mission. This paper is intended to open a discussion and motivate future detailed laboratory studies of prebiotic processes on young exoplanets and their chemical signatures.

On the specification of the chronostratigraphic scheme of the Buzko-Rosynskyi block of the Ukrainian Shield

In the current correlation chronostratigraphic scheme of early Precambrian of the Ukrainian Shield, among Neoarchean supra crystalline formations of the Buzko-Rosynskyi block, it is identified the Rosynsko-Tikytska series, which consist of the Myzynivska and Lysianska strata and the independent Volodarsko-Bilotserkivska strata, which are located on the same stratigraphic level in the scheme.
 According to the results of the mapping of metamorphic formations within this block during the geological survey of scale 1:200 000 (articles “Bila Tserkva”, “Uman”, “Lyubashivka”, “Kotovsk”, “Haisyn”, “Skvyra”) it is established these stratas are located in the section in a following order: the lower one is the Myzynivska, the middle one is the Volodarsko-Bilotserkivska and the upper one is the Lysianska and they form a single Rosynsko-Tikytska series. Also, these works did not confirm the presence in the region of the Bilotserkivska group of magnetic anomalies of two-pyroxene schale among the rocks of the Volodarsko-Bilotserkivska strata. This is a sign of their higher metamorphism degree. The hypersthene is present in the area of the Volodarka then only in high-iron rocks. Its presence is associated with a local temperature increase during metamorphism due to the high oxidative ability of iron. This indicates the possibility of its crystallization under conditions of amphibolite facies. A powerful argument in favor of this is the occurrence of a relatively thin carbonate-ferruginous-siliceous strata among thick amphibolite-gneiss and crystalline-schist-amphibolite strata which metamorphosed under amphibolite facies conditions. It indicates the low probability that the metamorphism of the iron ore could occur locally in other conditions.
 The obtained new data on the composition of the Rosynsko-Tikytska series and the actual stratigraphic sequence of stratas in it, indicates the necessity of making appropriate changes in the current correlation chronostratigraphic scheme of early Precambrian formations of the Ukrainian Shield.

Finding Signs of Life on Transiting Earthlike Planets: High-resolution Transmission Spectra of Earth through Time around FGKM Host Stars

Abstract The search for life in the universe mainly uses modern Earth as a template. However, we know that Earth’s atmospheric composition changed significantly through its geological evolution. Recent discoveries show that transiting, potentially Earthlike, exoplanets orbit a wide range of host stars, which strongly influence their atmospheric composition and remotely detectable spectra. Thus, a database for transiting terrestrial exoplanets around different host stars at different geological times is a crucial missing ingredient to support observational searches for signs of life in exoplanet atmospheres. Here, we present the first high-resolution transmission spectra database for Earthlike planets, orbiting a wide range of host stars, throughout four representative stages of Earth’s history. These correspond to a prebiotic high-CO2 world—about 3.9 billion years ago in Earth’s history—and three epochs through the increase in oxygen from 0.2% to modern atmospheric levels of 21%. We demonstrate that the spectral biosignature pairs O2+CH4 and O3+CH4 in the atmosphere of a transiting Earthlike planet would show a remote observer that a biosphere exists for oxygen concentrations of about 1% of modern Earth’s—corresponding to about 1–2 billion years ago in Earth’s history—for all host stars. The full model and high-resolution transmission spectra database, covering 0.4–20 μm, for transiting exoplanets—from young prebiotic worlds to modern Earth analogs orbiting a wide range of host stars—is available online. It is a tool to plan and optimize our observation strategy, train retrieval methods, and interpret upcoming observations with ground- and space-based telescopes.

Persistence of partial melting in the southern North China Craton: Evidence from Paleoproterozoic migmatites of the Taihua Complex

The Taihua Complex is exposed in the southern North China Craton (NCC), it has experienced a long and complicated history of multiple crustal growth, magmatism, metamorphism and deformation during the early Precambrian. Abundant leucosomes are widely distributed within the migmatites of the Taihua Complex, which occurred as irregular lenses, blocks, layers or dikes with several thickness of millimeters to tens of centimeters wide. Meanwhile, former presence of melt and typical microstructures related to partial melting also can be recognized in the thin sections under the microscope, those provide compelling evidences that the Taihua Complex has extensively suffered partial melting, and can be regarded as the best target to decipher multistage anatexis during metamorphism as well as assembly of the whole NCC. However, the timing and nature of the partial melting in the Taihua Complex have not been well studied up to now. In this contribution, we present an integrated in situ zircon U-Pb ages and Hf isotope compositions for the Paleoproterozoic migmatites from the Taihua Complex in the southern NCC. Both the metasedimentary and metamorphized plutonic rocks of the Taihua Complex have extensively suffered partial melting. The ca. 2.50 Ga magmatic zircons or inherited magmatic cores from the migmatites and leucosomes present similar Hf isotope composition to those of the contemporaneous depleted mantle at ca. 2.50 Ga, suggesting that ca. 2.50 Ga is a major period of crustal growth in the southern NCC as well as the whole NCC. The ages of metamorphic zircons obtained from leucosomes, melanosomes and migmatites show a large time interval of 1909–1798 Ma, indicating that the Taihua Complex has experienced a persistence of partial melting event during Late Paleoproterozoic that lasted more than 100 Ma. The crustal anatexis in the southern NCC probably occurred during the post-peak upper amphibolite- to granulite facies stage with melting temperature of at least 652–753 °C. The decompression melting and widespread migmatization of the Taihua Compelx are probably due to extension related to exhumation of the previously thickened crust during Paleoproterozoic collision between the Eastern and Western block, or between the Southern Archean Block and other micro-continents. The main collision-related assembly and crustal thickening events in the southern NCC likely occurred at ca. 1.95 Ga, rather than ca. 1.85 Ga as previously believed.

On the Capability of Oxidovanadium(IV) Derivatives to Act as All-Around Catalytic Promoters Since the Prebiotic World.

For a long time the biological role of vanadium was not known, while now the possibility of using its derivatives as potential therapeutic agents has given rise to investigations on their probable side effects. Vanadium compounds may inhibit different biochemical processes and lead to a variety of toxic effects and serious diseases. But, on the other hand, vanadium is an essential element for life. In recent years, increasing evidence has been acquired on the possible roles of vanadium in the higher forms of life. Despite several biochemical and physiological functions that have been suggested for vanadium and notwithstanding the amount of the knowledge so far accumulated, it still does not have a clearly defined role in the higher forms of life. What functions could vanadium or its very stable oxidovanadium(IV) derivatives have had in the prebiotic world and in the origins of life? In this review, we have briefly tried to highlight the most useful aspects that can be taken into consideration to give an answer to this still unresolved question and to show the high versatility of the oxidovanadium(IV) group to act as promoter of several oxidation reactions when coordinated with a variety of ligands, including diketones like acylpyrazolones.

Carbonate Deposits of Eastern Sarmatia (Early Precambrian Ignateevo Formation, Kursk Block): Sedimentation Conditions and Paleocontinental Correlations

The Neoarchean–Early Paleoproterozoic section of the Eastern Sarmatia Kursk Block contains different formations: terrigenous-carbonate (Ignateevo Formation), terrigenous (Stoilo Formation), and banded iron (Korobki Formation). The Kursk Block sequences have obvious similarities to the coeval terrigenous-carbonaceous-ferriferous formations of the Kaapvaal and Pilbara cratons. The Ignateevo Formation dolomites are correlated with the Campbellrand–Malmani and Wittenoom–Carawine carbonate platforms. Carbonate rocks of all three cratons are silicified and show no evidence of clastic contamination. They are characterized by low Sr concentrations and are enriched in Fe and Mn. The REE distribution in carbonate rocks is characteristic of Neoarchean marine sediments: flat profiles on spider diagrams, positive La anomalies, absence of Ce anomaly, and increased Y/Ho ratios relative to the chondrite value. The values of δ13C (0.3–0.9‰ PDB) and δ18O (–10.1 to –13.0‰ PDB) in the Ignateevo Formation dolomites fall within the range of the Late Archean and Early Paleoproterozoic marine carbonate sediments. The 87Sr/86Sr ratio in the Ignateevo Formation dolomites (0.7101–0.7195) is higher than that in the Neoarchean marine carbonates, which implies either isolation of the paleobasin or disturbance of the Rb–Sr isotope systems during metamorphism. The Ignateevo Formation dolomites and calc-silicate rocks (intensively silicified dolomites) are closest in their isotope-geochemical characteristics to shallow-water dolomites of the Campbellrand–Malmani Platform (South Africa). Probably, the Ignateevo Formation dolomites and partly the formations composing the Campbellrand–Malmani Platform formed in the most isolated part of the paleobasin, which facilitated to their complete dolomitization and partial silicification.

Theoretical minimal RNA rings mimick molecular evolution before tRNA-mediated translation: codon-amino acid affinities increase from early to late RNA rings

Nucleotide affinities for noncovalent interactions with amino acids produce associations between mRNAs and cognate peptides, potentially regulating ribosomal translation. Correlations between nucleotide affinities and residue hydrophobicity are explored for 25 theoretical minimal RNA rings, 22 nucleotide-long RNAs designed in silico to code for each amino acid once after three translation rounds, and forming stem-loop hairpins. This design presumably mimicks life's first RNAs. RNA rings resemble consensual tRNAs, suggesting proto-tRNA function, predicted anticodon and cognate amino acid. The 25 RNA rings and their presumed evolutionary order, deduced from the genetic code integration order of the amino acid cognate to their predicted anticodon, produces noteworthy associations with several ancient properties of the cell's translational machinery. Here we use this system to explore the evolution of codon affinity-residue hydrophobicity correlations, assuming these reflect pre-tRNA and pre-ribosomal translations. This hypothesis expects that correlations decrease with genetic code inclusion orders of RNA ring cognates. RNA ring associations between nucleotide affinities and residue hydrophobicities resemble those from modern natural genes/proteins. Association strengths decrease with genetic code inclusion ranks of proto-tRNA cognate amino acids. In silico design of minimal RNA rings didn't account for affinities between RNA and peptides coded by these RNAs. Yet, interactions between RNA rings and translated cognate peptides resemble modern natural genes. This property is strongest for ancient RNA rings, weakest for recent RNA rings, spanning a period during which modern tRNA- and ribosome-based translation presumably evolved. Results indicate that translation lacking tRNA-like adaptors based on codon-amino acid affinities and the genetic code pre-existed tRNA-mediated translation. Theoretical minimal RNA rings appear valid prebiotic peptide-RNA world models for the transition between pre-tRNA- and tRNA-mediated translations.

Revisiting stratigraphic complexes and regional stratigraphic scheme of the lower precambrian of the Ukrainian shield. Article 2. Correlation of complexes of ukrainian and other shields of North Eurasia

The second article discusses the 5 main types of stratogenic metamorphic complexes found in the East-European and Siberian platforms: 1) granulite-gneissic; 2) amphibolite-gneissic; 3) greenstone; 4) ferruginous-siliceous-schistose (metavolcano-chemo-terrigenic) 5) gneiss-schistose (metacarbonaceous-terrigenic). The types of complexes, in addition to the fact that they differ in the degree and type of metamorphism, also have different geologic-formational composition. These complexes are seen as the largest regional stratigraphic subdivisions in all regions of the Early Precambrian. They are represented with varying degrees of completeness on the Aldan-Stanovian, Anabarian and Baltic shields and on the Voronezh crystalline massif. The most complete stratigenic metamorphic complexes are developed on the Ukrainian and Aldan-Stanovian Shields. The complexes of the various regeions are mutually correllated between themselves and the Ukrainian Shield based on them corresponding to the types of stratogenic metamorphic complexes. The similarities between the complexes across different regions are to most researchers evidence not only of similar conditions of the formation of same-type complexes, but also, most likely, their conformance to identical quasi-synchronous stages in the development of the Earth’s core. Based on the results of both articles of the cycle, it is concluded that the largest divisions of the current Chronostratigraphic Scheme of the Early Precambrian of the Ukrainian Shield, which are shown in it as “series”, deserve either the transfer to the rank of “stratigraphic complexes” or the inclusion in the complexes by uniting series. Combining of the series concern to granulite-gneiss complexes that need to be renamed in the updated stratigraphic scheme. For other complexes, for the sake of inheritance with the previous schemes, it is advisable to preserve the geographical names of the series.

Modification of the hydro-thermal mineral-forming fluid composition in the Early Precambrian of the Earth

Modification of the hydro-thermal mineral-forming fluid composition in the Early Precambrian of the Earth

Small circRNAs with self-cleaving ribozymes are highly expressed in diverse metazoan transcriptomes.

Ribozymes are catalytic RNAs present in modern genomes but regarded as remnants of a prebiotic RNA world. The paradigmatic hammerhead ribozyme (HHR) is a small self-cleaving motif widespread from bacterial to human genomes. Here, we report that most of the classical type I HHRs frequently found in the genomes of animals are contained within a novel family of non-autonomous non-LTR retrotransposons of the retrozyme class. These retroelements are expressed as abundant linear and circular RNAs of ∼170-400 nt in different animal tissues. Bioinformatic and in vitro analyses indicate an efficient self-cleavage of the HHRs harboured in most invertebrate retrozymes, whereas HHRs in retrozymes of vertebrates, such as the axolotl and other amphibians, require to act as dimeric motifs to reach higher self-cleavage rates. Ligation assays of retrozyme RNAs with a protein ligase versus HHR self-ligation indicate that, most likely, tRNA ligases and not the ribozymes are involved in the step of RNA circularization. Altogether, these results confirm the existence of a new and conserved pathway in animals and, likely, eukaryotes in general, for the efficient biosynthesis of RNA circles through small ribozymes, which opens the door for the development of new tools in the emerging field of study of circRNAs.

High-resolution Transmission Spectra of Earth Through Geological Time

Abstract The next generation of ground- and space-based telescopes will be able to observe rocky Earth-like planets in the near future, transiting their host star. We explore how the transmission spectrum of Earth changed through its geological history. These transmission spectra provide a template for how to characterize an Earth-like exoplanet—from a young prebiotic world to a modern Earth. They also allow us to explore at what point in its evolution a distant observer could identify life on our Pale Blue Dots and other worlds like it. We chose atmosphere models representative of five geological epochs of Earth’s history, corresponding to a prebiotic high CO2-world 3.9 billion years ago (Ga), an anoxic world around 3.5 Ga, and 3 epochs through the rise of oxygen from 0.2% to present atmospheric levels of 21%. Our transmission spectra show atmospheric spectral features, which would show a remote observer that Earth had a biosphere since about 2 billion years ago. The high-resolution transmission spectral database of Earth through geological time from the VIS to the IR is available online and can be used as a tool to optimize our observation strategy, train retrieval methods, and interpret upcoming observations with the James Webb Space Telescope, the Extremely Large Telescopes, and future mission concepts like Origins, HabEx, and LUOVIR.

Earth’s Oldest Rocks (2nd Edition). Martin van Kranendonk, Vickie Bennett, and Elis Hoffmann, Editors

Book Review| March 01, 2020 Earth’s Oldest Rocks (2nd Edition). Martin van Kranendonk, Vickie Bennett, and Elis Hoffmann, Editors Peter A. Cawood Peter A. Cawood School of Earth Atmosphere and Environment Monash University Clayton, Victoria 3800, Australia January 23, 2020 Search for other works by this author on: GSW Google Scholar Economic Geology (2020) 115 (2): 473. https://doi.org/10.5382/econgeo.115.2.br02 Article history first online: 09 Mar 2020 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Peter A. Cawood; Earth’s Oldest Rocks (2nd Edition). Martin van Kranendonk, Vickie Bennett, and Elis Hoffmann, Editors. Economic Geology 2020;; 115 (2): 473. doi: https://doi.org/10.5382/econgeo.115.2.br02 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyEconomic Geology Search Advanced Search Earth’s Oldest Rocks (2nd Edition). Martin van Kranendonk, Vickie Bennett, and Elis Hoffmann, Editors. 2018. Elsevier. 1112 Pp. Paperback ISBN 978-0-444639011; eBook ISBN 978-0-444639028. Price: $US225. Earth’s Oldest Rocks focuses on the first 1.5 billion years of our planet’s history, covering the period from its accretion from the solar nebula to a time when plate tectonics is thought to be the modus operandi controlling Earth evolution. This record is spatially and temporally incomplete with the first 500 million years, the Hadean Eon, largely limited to a few zircon grains and some small rock outcrops. The rock record becomes more... You do not currently have access to this article.

Prebiotic Peptides: Molecular Hubs in the Origin of Life.

The fundamental roles that peptides and proteins play in today's biology makes it almost indisputable that peptides were key players in the origin of life. Insofar as it is appropriate to extrapolate back from extant biology to the prebiotic world, one must acknowledge the critical importance that interconnected molecular networks, likely with peptides as key components, would have played in life's origin. In this review, we summarize chemical processes involving peptides that could have contributed to early chemical evolution, with an emphasis on molecular interactions between peptides and other classes of organic molecules. We first summarize mechanisms by which amino acids and similar building blocks could have been produced and elaborated into proto-peptides. Next, non-covalent interactions of peptides with other peptides as well as with nucleic acids, lipids, carbohydrates, metal ions, and aromatic molecules are discussed in relation to the possible roles of such interactions in chemical evolution of structure and function. Finally, we describe research involving structural alternatives to peptides and covalent adducts between amino acids/peptides and other classes of molecules. We propose that ample future breakthroughs in origin-of-life chemistry will stem from investigations of interconnected chemical systems in which synergistic interactions between different classes of molecules emerge.

Plate-plume tectonics as an integrated mechanism of geodynamic development of the tectonosphere of Ukraine and adjacent regions

A progress of geodynamic processes in Early Precambrian of the Ukrainian Shield (USh) has been considered. Based on the known data on plate- and plume-tectonic processes of Phanerozoic the following problems have been investigated: 1) what trajectories of material flows in Precambrian mantle might occur; 2) what was an interaction of plumes and regular mantle convection; 3) the time of existence of plumes and are they permanent or pulsating; 4) the time of beginning of Precambrian geodynamic processes comparable with Phanerozoic ones. It has been shown taking as examples the Ukrainian and the Canadian shields that present-day thermochemical and dynamic processes do not completely delete geological-geophysical features of ancient zones of subduction and plumes in solid lithosphere and adjacent areas of mesosphere preserved since Early Precambrian. The Earth crust of these shields was intensely reprocessed by granitization and basification comparable with activity of hot points that were more developed than now. Within the area of USh these processes were the most active in the interval 2,0±0,2 Ga. Two of stages of geodynamic evolution of the USh within the limits of the Bug-Middle Dnieper-Periazov and Volyn-Podolian parts, superimposed in time, have been studied. Comparison of materials of geologic-geophysical mapping of this territory with the data of deep seismic sounding (DSS) and seismography allows refining geodynamic model of the Volyn-Podolian part of the USh along the trans-sect Eurobridge-97 composed earlier. Tectonophysical justification of necessity to include pulsating plumes with which formation of the Korsun-Novomyrgorod and Korosten plutons of gabbro -anorthosites and rapakivi was particularly associated to geodynamic process has been given. Comparison of models of subduction-collision processes within the limits of the USh and the Superior Province (Canada) has shown that independent approaches to solving geodynamic problems give relative results. The materials obtained on the USh do not exhaust all the possible episodes of its Neoarhean –Proterozoic geodynamic development. Trailing of super-modern DSS geo-travers along the axial part of the USh is required for their study.