Nappe structure of the Asaji metamorphic rocks, with special reference to geological structure of the basement complexes in Kyushu

The Asaji metamorphic rocks in the Notsuharu area, Oita Prefecture are composed mainly of pelitic rock, psammitic rock, chert, basic rock and serpentinite. Thelast forms serpentinite melange zone, including many blocks of metamorphic rocks, and shows an overturned fold of SE vergence with the NE plunging fold axis and NNW dipping axial plane. The metamorphic rocks are divided into two groups, separated from each other by the melange zone. One occupies the horizon below the melange zone and the other above. Carbonaceous materials from 32 pelitic rock samples were examined by TAGIRI'S (1981) X-ray diffraction method in order to compare their metamorphic grade. The results show the distinct discontinuity of metamorphic grade between two groups of both sides of the melange zone. It is concluded that the sequence above the melange zone is a nappe (Hikata nappe), and the SE vergenced overturned fold has been formed during the formation of the nappe structure. The Asaji metamorphic rocks are considered to be long to the Ryoke metamorphic rocks. In Kyushu, apparent continuity of the Sambagawa belt terminate at the Saga-noseki Peninsula just to the east of the Notsuharu area. It appears from the above that the nappe of the Ryoke metamophic rocks such as the Hikata nappe overlies the Sambagawa belt in Kyushu. Incidentally, the Nagasaki metamophic rocks would blong to the Sambagawa metamorphic rocks

P-t Path of Sediment Subduction-Underplating-Exhumation Process Related to the Formation of the Sambagawa Schists

The Valanginian accretionary complex and the Barremian accretionary complex of the Chichibu megaunit I of the Southern Chichibu belt in east Shikoku, which consist of prehnite-pumpellyite facies rocks and overlie the Albian accretionary complex of the Chichibu megaunit I and the Cenomanian-Turonian accretionary complex of the Shimanto megaunit, have been clarified by Hara et al. (1992) to be of the same age with reference to the subduction beginning age (youngest fossil age) as the Saruta nappe (I+II) schists and the Fuyunose nappe schists of the Sambagawa megaunit as high P/T type metamorphic rocks respectively. K-Ar ages of muscovites from the former two accretionary complexes, which are considered to have been roughly comparable with the exhumation beginning age, were determined in this paper to be 114 ± 6Ma and 108 ± 5Ma respectively. The exhumation beginning age appears to have been different by ca. 20Ma between the Chichibu megaunit I of subcretion depth of a few kilobars (less than 4kb) and the Sambagawa megaunit of subcretion depth of ca. 10kb with the same subduction beginning age. It would said that this is a rough estimate of P-t path of sediment subduction-underplating-exhumation process related to the formation of the Sambagawa megaunit

Some problems on Palaeozoic-Mesozoic tectonics inSouthwest Japan: Tectonics of metamorphic belts of high-pressure type

Tectonics of the Sangun belt and Sambagawa belt in Southwest Japan, which belong to the metamorphic belt of high-pressure type, have been discussed in this paper. Regarding the Sangun belt, the tectonics of the phases when the original rocks of the Sangun belt were deposited and the Sangun metamorphic field appeared have been analysed. As for the Sambagawa belt, the tectonics of the phases when the Sambagawa metamorphic field was placed under the condition of the highest temperature and then its collapse began have been analysed

Tectonic Evolution of the Sambagawa Schists and its Implications in Convergent Margin Processes

The Sambagawa schists as high P /T metamorphic rocks are a member of Mesozoic accretionary complexes developed in the southern front of the Kurosegawa-Koryoke continent of Southwest Japan. The Mesozoic accretionary complexes are divided into four megaunits developed as nappes, Chichibu megaunit II, Sambagawa megaunit, Chichibu megaunit I and Shimanto megaunit in descending order of structural level. The Chichibu megaunit II consists of three accretionary units developed as nappes, late early Jurassic unit, late middle Jurassic unit and latest Jurassic unit (Mikabu unit) in descending order of structural level. The Chichibu megaunit I consists of five accretionary units developed as nappes, late middle Jurassic unit (Niyodo unit), late Jurassic unit, Valanginian unit, Barremian unit and Albian unit in descending order of structural level. The Shimanto megaunit, which just underlies the Chichibu megaunit I, is Cenomanian-Turonian accretionary unit and Coniacian-Campanian accretionary unit. The schists, which underlie the Chichibu megaunit II, all have been so far called the Sambagawa schists. These are divided into six units, Saruta unit, Fuyunose unit, Sogauchi unit, Sakamoto unit, Oboke unit and Tatsuyama unit in descending order of structural level, which show different tectono-metamorphic history and different radiometric ages from each other. The Sakamoto unit, Oboke unit and Tatsuyama unit have been assumed with reference to their radiometric ages and structural relations to belong to the late middle Jurassic accretionary unit of the Chichibu megaunit I (high pressure equivalent of the Niyodo unit), the Cenomanian-Turonian accretionary unit of the Shimanto megaunit and the Coniacian-Campanian accretionary unit of the Shimanto megaunit respectively in this paper. The upper member of the Sambagawa schists, Saruta unit, Fuyunose unit and Sogauchi unit, is therefore called the Sambagawa megaunit in this paper. The northern half and the southern half of the Sambagawa megaunit are intercalated as nappes between the Chichibu megaunit II and the Oboke unit and between the Chichibu megaunit II and the Sakamoto unit respectively. The constituent units of the Chichibu megaunit II, Sambagawa megaunit and Shimanto megaunit clearly show a downward younging age polarity, as compared with each other with reference to the oldest one of radiometric ages ( = metamorphic ages) of each unit. The Chichibu megaunit II and the Chichibu megaunit I show the same radiometric ages as compared between them with the same fossil age. The Saruta unit, Fuyunose unit and Sogauchi unit have therefore been assumed to be high pressure equivalent of Valanginian unit, that of Barremian unit and that of Albian unit of the Chichibu megaunit I respectively. These high pressure units were exhumed, separating the Chichibu supermegaunit into the Chichibu megaunit II and the Chichibu megaunit I and thrusting up onto the Chichibu megaunit I. On the basis of the growth history of amphibole in hematite-bearing basic schists of the Sambagawa megaunit, it has been assumed that the highest temperature metamorphism of the Fuyunose unit occurred, when it had been coupled with the Saruta unit which was exhuming, and that of the Sogauchi unit did through its coupling with the Fuyunose and Saruta units which were exhuming. In the subduction zone which was responsible for the formation of the Sambagawa megaunit, namely, the peak metamorphism of a newly subducted unit appears to have occurred when it had been coupled with previously subcreted units which were exhuming. It has been also clarified that the subduction of a new unit occurred mixing the lower pressure part of the pre-existing subcretion unit as tectonic blocks. There is a distinct difference in the oldest one of radiometric ages between constituent units of the Sambagawa schists, showing a downward younging age polarity. The oldest one of radiometric ages of each unit appears to approximate to the age of the ending of peak metamorphism and to the age (Eh age) of the beginning of its exhumation. Such the tectonics of the Sambagawa megaunit would be explained in term of two-way street model. Because the age (Sub age) of the beginning of the subduction of each unit can be assumed from its fossil age, the average velocity of the subduction and that of the exhumation of the Sambagawa megaunit in Shikoku have roughly been estimated to be ca. 0.9 mm/year and ca. 2.0 mm/year respectively. Deformation of quartz, whose style depends strongly upon strain rate, resulted in type I crossed girdle without conentration in Y even in the depth part of more than 10kb of the subduction zone, which was placed under temperature condition of much higher than 500°C, unlike the cases of magma-arcs where quartz c-axis fabrics with maximum concentration in Y are found in gneisses produced under temperature condition of lower than 500°C. Quartz deformation in the depth part of 15-17kb of the subduction zone appears to have occurred as dominant prism slip. The hanging wall of the Kurosegawa-Koryoke continent, which was placed at the depth of ca. 15-17 kb, thrust onto the Saruta unit at the depth of ca. 10-11 kb, accompanying intermingling of constituent rocks of the former and the latter and also mixing of various depth parts of the latter. The highest temperature metamorphism of the Saruta unit, which appears to have occurred under metamorphic condition of lower P /T than under that related to the formation of the general type of high P /T type metamorphic rocks, is ascribed to a contact metamorphism related to the overthrusting of the Kurosegawa-Koryoke continent. The thrusting of the Kurosegawa-Koryoke continent is ascribed to its collision with the Hida continent. The coupling of the previously subcreted Saruta unit with the newly subcreted Fuyunose unit occurred accompanying nearly isobaric cooling of the former. The great exhumation of the Saruta nappe (I + II) and Fuyunose nappe schists with great volume began together with the subcretion of the Sogauchi unit. The beginning age of the exhumation of the Sambagawa schists with great volume appears to coincide with that of the subduction of the Kula-Pacific ridge in Kyushu-Shikoku, which has been assumed by Kiminami et al. (1990). Namely, their great exhumation occurred with the progress of the subduction of the Kula-Pacific ridge with an eastward younging age polarity. The exhumation units, which were developed after the Mikabu unit, clearly show an eastward younging age polarity. Namely, these comparable with the Saruta unit, Fuyunose unit and Sogauchi unit are not found in central Japan and the Kanto Mountains. Rock deformation in the deformation related to the exhumation of the Sambagawa schists and their underlying schists appears to have commonly been of flattened type in mean strain. During the Ozu phase when the Kula-Pacific ridge subducted to the greater depth, the collapse of the Kurosegawa-Koryoke continent took again place, accompanying that of the pile nappe structures of the Sambagawa megaunit, Chichibu megaunit I and Oboke unit, and the thermal gradient along the plate boundary greatly changed, giving rise to medium P/T type metamorphism in the subduction zone (formation of the Tatsuyama nappe schists). The geological structures of the Sambagawa megaunit consist thus of two types of pile nappe structures, pre-Ozu phase pile nappe structures and Ozu phase pile nappe structures. The former is structures related to the coupling of the exhuming units ( = previously subcreted units) with the newly subcreted unit. The latter is structures showing the collapse of the former. The Ozu phase pile nappe structures are further divided into the pile nappe structures formed during the earlier stage (Tsuji stage) of the Ozu phase and these formed during the later stage (Futami stage). The former is disharmonic with reference to movement picture with the latter: The deformation related to the formation of the former, accompanying exhumation of the Oboke nappes, appears to contain a component of northward displacement, while that for the latter does a component of southward displacement. After the Ozu phase deformation the Sambagawa megaunit suffered the Hijikawa-Oboke phase folding, forming a series of sinistral en echelon upright folds. The relationship between the above-mentioned tectonic events of the Sambagawa megaunit and its surroundings and their radiometric ages is summarized as follows: [Original table is skipped. For more details, please refer to the full text.

Genetic Characterization of Hantaviruses Transmitted by the Korean Field Mouse (Apodemus peninsulae), Far East Russia

In an epizootiologic survey of 122 rodents captured in Vladivostok, Russia, antibodies positive for hantavirus were found in Apodemus peninsulae (4/70), A. agrarius (1/39), and Clethrionomys rufocanus (1/8). The hantavirus sequences identified in two seropositive A. peninsulae and two patients with hemorrhagic fever with renal syndrome (HFRS) from the Primorye region of Far East Russia were designated as Solovey and Primorye, respectively. The nucleotide sequences of the Solovey, Primorye, and Amur (obtained through GenBank) sequences were closely related (>92% identity). Solovey and Primorye sequences shared 84% nucleotide identity with the prototype Hantaan 76-118. Phylogenetic analysis also indicated a close relationship between Solovey, Primorye, Amur, and other viruses identified in Russia, China, and Korea. Our findings suggest that the Korean field mouse (A. peninsulae) is the reservoir for a hantavirus that causes HFRS over a vast area of east Asia, including Far East Russia

Polymorphism of the Tryptophan Hydroxylase 2 (TPH2) Gene Is Associated with Chimpanzee Neuroticism

In the brain, serotonin production is controlled by tryptophan hydroxylase 2 (TPH2), a genotype. Previous studies found that mutations on the TPH2 locus in humans were associated with depression and studies of mice and studies of rhesus macaques have shown that the TPH2 locus was involved with aggressive behavior. We previously reported a functional single nucleotide polymorphism (SNP) in the form of an amino acid substitution, Q468R, in the chimpanzee TPH2 gene coding region. In the present study we tested whether this SNP was associated with neuroticism in captive and wild-born chimpanzees living in Japan and Guinea, respectively. Even after correcting for multiple tests (Bonferroni p = 0.05/6 = 0.008), Q468R was significantly related to higher neuroticism (β = 0.372, p = 0.005). This study is the first to identify a genotype linked to a personality trait in chimpanzees. In light of the prior studies on humans, mice, and rhesus macaques, these findings suggest that the relationship between neuroticism and TPH2 has deep phylogenetic roots

Genetic and biological comparision of tick-borne encephalitis viruses from Hokkaido and Far-Eastern Russia

We compared the biological properties of Oshima 5-10 (tick-borne encephalitis [TBE] virus isolated in Hokkaido, Japan) and Sofjin-HO (Far-Eastern subtype TBE virus) including plaque formation, virus replication and virus protein synthesis in BHK-21 cell cultures to reveal strain differences. We also determined the complete nucleotide sequences of both strains and compared the deduced amino acid sequences. Plaques of Oshima 5-10 were smaller than those of Sofjin-HO. Virus titers in culture fluid of Oshima 5-10 were 1/100 of those of Sofjin-HO at 9 and 12 hr after infection. Less viral protein and RNA syntheses of strain Oshima 5-10 was observed than with Sofjin-HO. Genetic analysis revealed 1.4% of amino acids to differ with Sofjin-HO. No difference between the two strains was detected in the motif sequence of the viral enzyme, cleavage sites of viral protein or glycosylation sites of NS1