Koichi Mimura

Nagoya University | Meidai

Pressure is one of the important factors that promote chemical reactions in solid organic matter. Here we present the pressure-induced chemical reactions of aromatic compounds. At room temperature, oligomerization of benzene and naphthalene was observed at pressures greater than around 15 GPa. Gas chromatography-mass spectrometry analysis of the re...

Silicate spherules have been identified from the ca. 3.4 Ga-old Strelley Pool Formation (SPF) in the Pilbara Craton, Western Australia. Their origins and geochemical characteristics, including the Re and platinum-group elements of their host clastic layer and the overlying and underlying microfossil-bearing finely laminated carbonaceous cherts, wer...

Shock experiments on an aqueous l-alanine solution were undertaken to examine the significance of cometary impacts in supplying prebiotic compounds to the early Earth. The shock pressures and temperatures ranged from 6.5 to 34.0 GPa and 516 to 963 K, respectively. Alanine in the shocked samples decreases in abundance and has higher d/l ratios as th...

The evolution of Earth’s climate and oceans during the Early Eocene Climatic Optimum (EECO) has been a focus of extensive research, but the continental response to global climate change in this warmer than modern world is poorly understood. This study quantitatively reconstructs terrestrial paleoenvironment and paleohydrological changes as recorded...

Hydrogenated carbon nitride is synthesized by polymerization of 1,5-naphthyridine, a nitrogen-containing heteroaromatic compound, under high-pressure and high-temperature conditions. The polymerization progressed significantly at temperatures above 573 K at 0.5 GPa and above 623 K at 1.5 GPa. The reaction temperature was relatively lower than that...

The Takisawa limestone body is embedded in the Iinoya Formation of the Chichibu Composite Belt, central Japan. The geological age of the Takisawa limestone body is ambiguous due to a paucity of index fossils. Here, we collected ten samples of the Takisawa limestone and report two fragments of conodont P1 elements. These conodonts can be identified...

Prof. Sugisaki performed a lot of creative studies dealing with various topics of earth science. We introduce his representative works in the following 6 sections: 1. Geochemical Studies of GroundWater, 2. Frontiers in Tectonochemistry, 3. Tectonic Behavior of Subsurface Fluids in Relation to Earthquakes, 4. Studies on Marine Sediments and Sediment...

To reveal the thermal history of the Allende (CV3) meteorite, we pyrolyzed insoluble organic matter (IOM) from the meteorite and examined the chemical and isotopic composition of the pyrolysates against the pyrolysis temperature. Major pyrolysates from the Allende IOM were sulfur (S)-bearing compounds (H2S, SO2, CS2, and OCS), oxygen (O)-bearing co...

The chemical reaction of 2,3-naphthyridine, a nitrogen-containing aromatic compound, was investigated at pressures ranging from 0.5 to 1.5 GPa and temperatures from 473 to 573 K. A distinct decrease in the amount of residual 2,3-naphthyridine was observed in the samples recovered after reaction at ˃523 K at 0.5 and 1.0 GPa, and ˃548 K at 1.5 GPa. T...

2,5-Diketopiperazines (DKPs) are widely recognized as chiral molecules with great potential in medicinal chemistry. Complete separation of DKP stereoisomers is very important for efficiently investigating the chemical characteristics of DKPs. The combination of esterification and acylation caused the enantiomers of cyclo(d-Ala-d-Ala) and cyclo(l-Al...

This study presents results of measurements of over 800 palynomorphic specimens of lenticular microfossils from the two remote localities of the 3.4 Ga Strelley Pool Formation in the Pilbara Craton, Western Australia that represent different depositional environments and thus different habitats. It is demonstrated statistically that the two populat...

Infrared spectra of benzene were measured at pressures up to 25.3 GPa at room temperature using a diamond anvil cell. With decompression from pressures above 18.7 GPa, a new peak of C-H vibration mode appeared at a lower frequency than that of benzene. This indicates that an irreversible chemical change occurred at a pressure that was lower than th...

Phase diagrams of benzene have been reported on the basis of data mainly obtained from static compression at various pressure-temperature, P-T, conditions. However, there are few data in the high pressure and high temperature region of the phase diagram. To understand the physical and chemical behavior of benzene in that region, multiple shock comp...

Oligomerization of alanine was observed by pressurizing its solid-free aqueous solution. Co-occurring solidifications of alanine and H2O as immiscible phases at high pressure were found to be crucial for concentrating the solute, alanine. The pressure-induced freeze concentration also enhances the pressure-induced oligomerization.

The stability and pressure-induced chemical reactions of naphthalene were investigated at room temperature at pressures up to 23 GPa. In-situ X-ray diffraction (XRD) measurements indicated that naphthalene retained its crystal structure up to ∼20 GPa, whereas a solid amorphous phase was observed in the recovered samples. Based on microanalysis of t...

Charcoal is widely used for radiocarbon dating in archaeological and paleoenvironmental studies. Reliable 14 C dating requires appropriate chemical treatment to remove postdeposition contamination from the charcoal samples. This study assesses two pretreatments: acid-base-acid (ABA) and acid-base-oxidation with stepped combustion (ABOx-SC). In addi...

Three pieces of coniform conodonts were discovered in the Aso limestone body in Fuketsu Cave, Chichibu Belt, Mie Prefecture. Although the genera and species of the discovered conodonts have not been identified, they have features similar to those of Late Triassic conodonts (e.g., Zieglericonus rhaeticus Kozur and Mock). Our discovery of conodonts a...

The 3.4-Ga Strelley Pool Formation (SPF) at the informally named 'Waterfall Locality' in the Goldsworthy greenstone belt of the Pilbara Craton, Western Australia, provides deeper insights into ancient, shallow subaqueous to possibly subaerial ecosystems. Outcrops at this locality contain a thin (<3 m) unit of carbonaceous and non-carbonaceous chert...

Pressure-induced oligomerization was found from high-pressure experiments at 25 °C on alanine powder soaked with its saturated aqueous solution. The oligomerization to alanylalanine occurred at 5 GPa. The maximum yields of alanylalanine and trialanine were, respectively, 1.1 × 10-3 and 1.3 × 10-4 at 11 GPa.

The Strelley Pool Formation (SPF) is widely distributed in the East Pilbara Terrane (EPT) of the Pilbara Craton, Western Australia, and represents a Paleoarchean shallow-water to subaerial environment. It was deposited ~3.4 billion years ago and displays well-documented carbonate stromatolites. Diverse putative microfossils (SPF microfossils) were...

Oligomerization of benzene at high pressures up to 16 GPa was investigated at room temperature using an opposed-anvil type pressure apparatus. The recovered samples were analyzed using GC-MS to identify and quantify the products after the high-pressure experiments. Some structural isomers of benzene dimer as well as biphenyl, naphthalene, and terph...

We conducted shock experiments simulating comet impacts to assess the feasibility of peptide synthesis by such a process. We used frozen mixture of the amino acid glycine, water ice, and silicate (forsterite) as the starting material and applied impact shocks ranging from 4.8 to 26.3 GPa using a vertical propellant gun under cryogenic conditions (7...

We suggest that comet impacts can readily account for the oligomerization of glycine to form the precursors of life on the early Earth. Since comet impacts are ubiquitous phenomenon, they play an important role in organic chemical evolution.

Abundant cell-like organic structures have been proposed as microfossils in Paleoarchean (3.2–3.5 Ga) cherts. The wide range of δ13Corg values recorded in Paleoarchean organic matter (OM), including some of these possible microfossils, is difficult to reconcile with the smaller range observed in living cells and younger microfossils. Metamorphic an...

A new microfossil locality for the ca. 3400 Ma Strelley Pool Formation (SPF), in the Pilbara Craton, Western Australia, was discovered in the Panorama greenstone belt. Large and morphologically diverse microfossils (>20 μm, up to 100 μm, along the major dimension) are abundant in a carbonaceous laminated black chert of shallow water origin that was...

Mt. Ishimaki is the Jurassic accretionary complex of the Chichibu Belt in Toyohashi City, near Nagoya in central Japan. The Ishimaki limestone is thought to be seamount-type limestone. The P1 elements of the conodonts Norigondolella navicula and Ancyrogondolella quadrata found in the limestone indicate it is of Norian age. The Sr isotopic compositi...

To study the detailed structural and isotopic heterogeneity of the insoluble organic matter (IOM) of the Murchison meteorite, we performed two types of pyrolytic experiments: gradual pyrolysis and stepwise pyrolysis. The pyrolysates from the IOM contained 5 specific organic groups: aliphatic hydrocarbons, aromatic hydrocarbons, sulfur-bearing compo...

A microfossil assemblage recently discovered from the Farrel Quartzite (ca. 3.0 Ga) in the Goldsworthy greenstone belt in the Pilbara Craton comprises five main morphological types (thread like, film-like, spheroidal [>15 and <15 μm], and lenticular to spindle-like) and some elaborate morphologies that might represent reproducing or resting stages...

In order to evaluate the dissolution processes of elements from subducting sediments into fluids during early stages of metamorphism (up to oligoclase-biotite zone at about 30 km depth), the chemical composition of Sanbagawa pelitic schists, Sanbagawa Metamorphic Belt, Japan was studied. Samples from different metamorphic grades show similarities i...

Morphologically diverse structures that may constitute organic microfossils are reported from three remote and widely separated localities assigned to the ca. 3400 Ma Strelley Pool Formation in the Pilbara Craton, Western Australia. These localities include the Panorama, Warralong, and Goldsworthy greenstone belts. From the Panorama greenstone belt...

A systematic REE+Y study of Archean (ca. 3.0Ga) cherts from the Mount Goldsworthy greenstone belt in the northeastern Pilbara Craton, Western Australia was performed in order to understand their origin and depositional environment. Analyzed samples include microfossil-bearing black cherts from the Farrel Quartzite and a black vein chert from the un...

Abstract— We performed shock-recovery experiments on insoluble organic matter (IOM) purified from the Murchison meteorite, and determined the abundances and isotope ratios of hydrogen and carbon in the shocked IOM sample. We also performed shock experiments on type III kerogen and compared the results of these experiments with the experimental resu...

A systematic REE + Y study of Archean (ca. 3.0 Ga) cherts from the Mount Goldsworthy greenstone belt in the northeastern Pilbara Craton, Western Australia was performed in order to understand their origin and depositional environment. Analyzed samples include microfossil-bearing black cherts from the Farrel Quartzite and a black vein chert from the...

Microstructures recently reported from an Archaean sedimentary succession (ca. 3.0 Ga) in the Mount Goldsworthy–Mount Grant area in the northeastern Pilbara Craton meet the criteria for compelling evidence of biogenicity [Sugitani, K., Grey, K., Allwood, A., Nagaoka, T., Mimura, K., Minami, M., Marshall, C.P., Van Kranendonk, M.J., Walter, M.R., 20...

We recently reported a diverse assemblage of carbonaceous structures (thread-like, film-like, spheroidal, and spindle-like) from chert in the ca. 3.0 Ga Farrel Quartzite of the Gorge Creek Group in the Pilbara Craton, Western Australia. Results from a rigorous examination of occurrence, composition, morphological complexity, size distributions, and...

Diverse microstructures have recently been reported from the Archean sedimentary succession now assigned to the Farrel Quartzite (3.02 Ga) at the Mount Grant and Mount Goldsworthy area, Pilbara Craton, Western Australia [1]. A highly probable to possible biogenic origin of the four major morphological types (thread-like, film-like, spheroidal and l...

A diverse assemblage of indigenous carbonaceous microstructures, classified here as highly probable microfossils to pseudomicrofossils, is present in the >ca. 2.97Ga Farrel Quartzite (Gorge Creek Group) at Mount Grant and Mount Goldsworthy, Pilbara Craton, Western Australia. The microstructures are an integral part of the primary sedimentary fabric...

The Middle Permian Gufeng Formation in the northeastern Yangtze platform, China, contains radiolarian chert that is characterized by black color, high content of Fe, Mo, Ni, Cu, and Zn. Based on the inorganic geochemical features, previous work concluded that the cherts were deposited under sulfate-reducing conditions. In this study, organic carbon...

We tried to estimate paleotemperatures from two chosen fossils by measuring d/l aspartic acid ratios and radiocarbon ages of the XAD-2-treated hydrolysate fractions in the fossils. The d/l aspartic acid ratio was measured with a gas chromatograph and radiocarbon dating was performed using a Tandetron AMS system at Nagoya University. The radiocarbon...

We performed shock-recovery experiments on insoluble organic matter (IOM) purified from the Murchison meteorite, and determined the abundances and isotope ratios of hydrogen and carbon in the shocked IOM sample. We also performed shock experiments on type III kerogen and compared the results of these experiments with the experimental results regard...

Since 1994 a geochemical mapping project has been undertaken in Aichi prefecture, central Japan, with the aim of establishing a database to contribute to environmental assessment in the region. To date more than 1200 stream sediments have been collected and analyzed. The samples were analyzed for 10 major elements by X-ray fluorescence spectrometry...

Geochemical and petrological analyses of Archean clastic metasedimentary rocks at Mt. Goldsworthy in the Pilbara Craton, Western Australia reveal the early evolution of continental crust and the Earth's surface environment. The succession correlative to the ca. 3.4 Ga Strelley Pool Chert is composed dominantly of silicified medium-grained to very c...

Geochemical maps expressing areal distributions of chemical elements in the earth’s land surface have been published in several countries in relation to various global environment issues. The authors have applied a radiogenic isotope ratio, 87Sr/86Sr, to geochemical mapping in order to understand the geological origin, transportation and dispersion...

Single- and multiple-shock recovery experiments on Murchison meteorite samples were performed, to examine the shock-induced isotope behavior of their hydrogen and carbon contents. δD values of the shocked Murchison showed an initial increase from +10.6‰ to +59.1‰ before declining to −87.6‰, as the dehydrogenation progressed. Isotope behavior of δD...

Polycyclic aromatic hydrocarbons (PAHs) were shocked across a peak shock pressure range of 5.8 to 36.6 GPa with or without serpentine and were then evaluated with an elemental analyzer, an X-ray diffractometer, a gas chromatograph, and a gas chromatograph–mass spectrometer. On the basis of the results, we examined the shock-induced dehydrogenation...

Polycyclic aromatic hydrocarbons (PAHs) with a hydrous or an unhydrous mineral matrix were impacted and analyzed, to study the behavior of PAHs against shock. Results of the shock experiments suggested that volatiles discharged from the hydrous mineral did not influence the behavior of PAHs against shock. The shocked samples contained unreacted sta...

To examine the behavior of polycyclic aromatic hydrocarbons (PAHs) during shock-induced pyrolysis, we performed shock recovery experiments of various PAHs (naphthalene, anthracene, pyrene, and fluoranthene) at pressures ranging from 12.0 to 33.7GPa. The shock-induced pyrolysis predominantly produced amorphous carbon. The pyrolysis consists of PAH r...

The chemical behavior of phenanthrene during a reaction triggered by shock waves, and its influence on the physical property of phenanthrene were studied over the pressure range of 7.9–32.0 GPa. Chemical analyses showed that shocked phenanthrene included insoluble carbonaceous material containing amorphous carbon, polycyclic aromatic hydrocarbons (...

A total of 27 well gas samples collected from SW Japan were subjected to precise analysis of He, Ne and Ar isotopic compositions. The sampling area covers localities where mantle-derived helium emanates in the fore-arc of the Kii Peninsula, and is known as the ‘Kinki spot’ [e.g., Sano and Wakita, J. Geophys. Res. 90 (1985) 8728–8741]. The Kinki spo...

We analyzed normal saturated paraffins (n-paraffins) in 70 surface sediments in the northwest Pacific to examine the spatial distribution of organic materials. All sediments show bimodal n-paraffin abundance patterns against carbon number with maxima at C16 and C31, indicating that n-paraffins in marine sediments are a mixture of long-chain n-paraf...

A approximately 3.3 Ga sedimentary succession at Mt. Goldsworthy in the northeastern Pilbara Block, Australia contains beds composed of silicified pseudomorphs of nahcolite (NaHCO3) or barite (BaSO4). This sedimentary succession correlates with the Corboy Formation and consists of lower, middle and upper sedimentary units, which conformably overlie...

Shock waves and carbon-bearing materials occur ubiquitously in the universe and the interaction between them is a common phenomenon. In the interaction, which we call shock reaction, the shock wave compresses and heats the carbon-bearing materials, producing organic materials with compositions differing from those of the initial materials. We belie...

Normal saturated fatty acid (n-fatty acid) in marine sediments from coastal and pelagic environments were analyzed. The coastal sediments contain both short-chained n-fatty acids with carbon numbers from 12 to 18 and long-chained acids from 22 to 32, whereas the pelagic sediments contain predominantly short-chained acids. The relative abundance of...

Normal saturated fatty acid (n-fatty acid) in marine sediments from coastal and pelagic environments were analyzed. The coastal sediments contain both short-chained n-fatty acids with carbon numbers from 12 to 18 and long-chained acids from 22 to 32, whereas the pelagic sediments contain predominantly short-chained acids. The relative abundance of...

Middle Triassic radiolarian bedded cherts in the Mino Belt, central Japan, include a sequence showing an abrupt facies change from the lower to the upper, where grey–black bedded cherts enriched in carbonaceous matter and framboidal pyrite are overlain by brick-red hematitic bedded cherts. Brownish-yellow chert enriched in goethite and purple-red c...

Shock waves generated by projectile impacts were transmitted into hexane and the shocked hexane was analyzed by TCD-GC, FID-GC, GCMS, and FABMS for produced aliphatic hydrocarbons. The projectile length and its velocity were varied from 10 to 40 mm and from 220 to 1040 m/s, respectively. The initial temperature of the hexane was 77, 193 and 273 K....

Normal paraffin compositions were determined for marine sediments from coastal and pelagic environments and for shales in the Jurassic-Cretaceous bedded chert sequence from the Franciscan terrane, western North America. The pelagic sediments and shales from a lower horizon of the bedded chert sequence are characterized by short-chained n-paraffins....

Stream sediments in and around Seto City, Aichi Prefecture, were examined for geoenvironmental assessment of the area. New 157 samples were analysed for seventeen elements including Al, Ca, Ce, Co, Cr, Cu, Fe, K, Mn, Mg, Na, Ni, P, Sr, Ti, V and Zn. ICP atomic emission spectrometry and atomic absorption spectrometry were employed for the analyses....

This article discusses the comments of J.F.Kenney regarding the paper presented by Sugisaki and Mimura on the possible abiogenic origin of hydrocarbons in mantle rocks. They discuss the problems pointed out by Kenney and emphasize the consistency between their results and the studies of several Russian scientists.

Shock waves trigger reactions in solid benzene at 77 K to produce hydrogen, light alkanes from C1 to C3, light alkenes from C2 to C3, acetylene, aromatic hydrocarbons with high-molecular weights ranging from 102 (phenylacetylene) to 306 (quaterphenyl), and unknown carbonaceous materials. These products are similar to those yielded by rapidly quench...

The synthesis of polycyclic aromatic hydrocarbons (PAHs) from benzene by shock waves was studied in order to search for a novel possibility of PAH formation under cosmochemical conditions. Shock waves generated by projectile impacts were transmitted into pure benzene, and then the shocked samples were analyzed by FID gas chromatography and gas chro...

It was experimentally shown that shock waves generated by projectile impact cause a reaction between benzene molecules to produce heavier aromatic hydrocarbons such as naphthalene, biphenyl, phenanthrene, and chrysene. Most of these shock induced-molecules are detected in meteorites and cosmic dusts; some in interstellar environments. Such processe...

Analyses of 227 rocks from fifty localities throughout the world showed that mantle derived rocks such as tectonized peridotites in ophiolite sequences (tectonites) arid peridotite xenoliths in alkali basalts contain heavier hydrocarbons (n-alkanes), whereas igneous rocks produced by magmas such as gabbro arid granite lack them. The occurrence of h...

Impact experiments for CO and H2 mixtures showed that hydrocarbon gases up to C4H10 are synthesized by shock. The conversion of CO to hydrocarbons increases with increasing shock energy but the composition of synthesized hydrocarbons depends on that of the reactant (H2/CO). From the results, geneses of some light hydrocarbons in planetary materials...

国立情報学研究所で電子化したコンテンツを使用している。 The Geochemistry and Cosmochemistry Laboratory, Nagoya University, began a geochemical mapping project in 1994 to make environmental assessment of the Chubu area in Japan and to provide students with the training of collection and chemical analysis of geological samples. During ten years from 1994 to 2004, 1563 stream se...

Lake Nakaumi, San-in area, is one of the largest blackish lake in Japan. Recently, sedimentation of organic flock named “Hedoro” becomes a serious problem, because the enrichment of organic flock may damage the ecological system. In order to reveal geochemical behavior of elements in the organic-rich sediment of the brackish lake during early diage...