Green Tuff Research Articles

Hydrogen and oxygen isotopic ratios and major element chemistry of Japanese thermal water systems

More than 140 thermal waters of Japan were studied isotopically and chemically. Highly saline brines at Arima and Takarazuka, Hyogo-Ken, and Ishibotoke near Osaka indicate wide ranges of δ18O and δD values from meteoric values of δ18O = -8.2 and δD = -50.0 ‰ SMOW to highly shifted values of +6.5 and -27.8 ‰, respectively. The isotopic values of these brines vary proportionally with chloride concentration irrespective of temperature, carbonate concentration or locality. These saline waters are isotopically and chemically best explained as the mixtures of local meteoric waters and a saline brine of Cl-= 43, 700 ppm, δ18O = +8 ‰ and δD = -30 to -25 ‰. The latter is most likely the “residual magmatic, metamorphic or geothermal” fluid associated with upper Cretaceous rhyolitic and granitic rocks and Ryoke metamorphic rocks in which these brines are found. Thermal waters at Ikeda and in adjacent areas, Shimane-Ken and at Senami, Niigata-Ken, are similar to the Arima brines in the isotopic and major element chemistry, but are much more diluted by the respective local meteoric waters. Many of the thermal waters along the ocean coasts are isotopically intermediate between oceanic and local meteoric waters and are considered to be mixtures of the two types of water. As a result of hydrothermal mineral-sea water interaction, the coastal thermal waters differ considerably in the chemistry from fresh sea water and are typical of Na-Ca-Cl type. The coastal thermal waters isotopically and chemically may be similar, if not the same, to submarine hydrothermal ore fluids responsible for the Kuroko type mineralization. The isotopic values and their relationship to salinity, however, widely differ from one system to another depending on the hydrogeological conditions of each system. The coastal thermal waters at Ibusuki of Ata Caldera, Kagoshima-Ken, for instance, are significantly affected by the waters from three crater lakes, Lake Ikeda, Unagi-Ike and Kagami-Ike, in which the δ18O and δD values are meteorologically balanced at such high values as -2.6 and -19.4‰, respectively. Acid to neutral thermal waters of volcanic affiliation indicate varying degrees of isotopic shifts, but they are supposed from their δD values to be essentially derived from recycled meteoric water. Many thermal waters of neutral chloride type in the “green tuff” regions of the inner Honshu also are simple meteoric in origin without showing any significant isotopic shifts, although the waters are relatively high in salinity and SO4/Cl ratios.

Synthesis of analcime from volcanic sediments in sodium silicate solution

Analcime has been synthesized from natural rhyolitic tuff and green tuff (Miocene age) at 200° C and 20 kg/cm2 with solution of Na2SiO3 (12%) in 50- to 260-hr runs. From the diffraction intensities, it was found that the alteration products of green tuff contained more analcime than those of rhyolitic tuff. It has been concluded that the lithological character of starting materials and the chemical behavior of reaction products are important controlling factors in analcimization.

HYDROTHERMAL ALTERATION OF MIOCENE TUFFS IN NAOH•KOH SOLUTIONS, WITH SPECIAL REFERENCE TO CHEMICAL BEHAVIOR (HYDROTHERMAL STUDIES ON THE WALL-ROCK ALTERATION-3-)

Natural green tuff and rhyolitic tuff (Miocene age) were subjected to alter in sodium hydroxide and potassium hydroxide solutions under 200°C and 200kg/cm2. Various chemical behaviors were shown under the influence of running times and chemical conditions. Al2O3 content in the alteration product shows an apparent increase. However, Al2O3 is absent from the present hydrothermal solutions. It is assumed that during hydrothermal alteration, fresh rock has decreased in weight so that Al2O3 has apparently increased. Column A in Table 5 shows the culculated weight in grams of each oxide remaining from the alteration of 100g of fresh rock, on the assumption of constant Al2O3. It may be concluded from the present experiments that the amount of analcime in the alteration product depends upon mineral mineral association of starting material and contents of SiO2 in alteration products.

AN INTERSTRATIFIED MINERAL OF CHLORITE AND MONTMORILLONITE FROM THE GREEN TUFF IN THE YAMAKATA DISTRICT IBARAGI PREFECTURE JAPAN

An interstratified chlorite-montmorillonite mineral was found as an alteration mineral of tuff and tuffaceous sediments in the Neogene Tertiary “Green Tuff” near the Yamakata-machi, Kuji-Gun, Ibaragi Prefecture. The <2μ fraction obtained by the sedimentation method contains about 3.2% quartz as an impurity. Chemical composition: SiO2 37.82%; TiO2 0.22%; Al2O3 14.72%; Fe2O3 6.47%; FeO 8.90%; MgO 14.36%; MnO 0.37%; CaO 1.81%; Na2O 1.10%; K2O 1.10%; H2O (+) 7.10%; H2O (-) 6.44%; total 100.41%. After subtracted 3.2% quartz from the chemical analysis, the structural formula was obtained as (Ca0.357Na0.391K0.258) (Al1.563Fe+30.895Fe+21.369Mg3.938) (Si6.371Al1.629) O20 (OH)10. nH2O. X-ray examination of the natural material shows a reflection at about 31A and its higher orders, but they make an irrational series. The montmorillonite-like layers expand with ethylene glycol and contract with heat treatment similar to montmorillonite. X-ray analysis revealed that the interstratification is produced by two component stacking of about 60% chlorite-like layers and about 40% montmorillonite-like layers. DTA and I. R. data are also described in this paper.

Bedded manganese ore deposit of the Sanpo mine, in the Imagane-cho, Setana Province, Hokkaido

Ore deposit of the Sanpo mine buried between green tuff breccia and pebble bearing sandstone belong to the Kunnui-Formation of Neogene Tertiary is manganese ore deposit of bedded form called the Pirika type. Most of the Pirika type deposits occurred in the Yakumo-Formation or between the Yakumo- and Kunnui-Formations are commonly constituted with the ore min srals of manganese oxide such as pyrolusite, cryptomelane, nsutite, manganite and so on. Though ore deposit of the Sanpo mine is one of the Pirika type deposits, it differs from the others on several points such as stratigraphical horizon of mineralization, and properties of country rocks and paragenesis of ore minerals. Especially, piedmontite-braunite associations in dense ore, and montmorillonitepiedmontite assemblage in the hanging wall-rock, are very interesting. Thus we concluded that the bedded manganese ore deposits of the mine might be caused by epigenetic condition.

30. Some chemical characteristics of the Neogene Tertiary volcanic rocks distributed in the green tuff area(Abstracts of Papers submitted for the Meetings of the Society)

30. Some chemical characteristics of the Neogene Tertiary volcanic rocks distributed in the green tuff area(Abstracts of Papers submitted for the Meetings of the Society)

Chemical composition of wairakites in green tuff

Wairakites in Miocene andesitic-basaltic pyroclastic rocks of the Tanzawa Mountain and Yugami districts are very close to CaAl2Si4O122H2O in chemical composition.

Bentonite deposits at Hattari, Hokkaido (II)

The Hattari bentonite deposits which are situated at the southwestern end of the Shakotan Peninsula occur in the Miocene green tuff formation. This formation in the neighborhood of the deposits is divided into the following three zones from the lower side by kinds of zeolites in the tuff: (1) Analcime zone in the northeastern part of this mining area. (2) Non-zeolite zone in the middle part. (3) Clinoptilolite zone in the southwestern part. These zones do not always correspond with the subdivision of the strata. The bentonite deposits are found in the clinoptilolite zone and the ore bodies form irregularly lenticular beds. The original rock of the bentonite is rhyolitic vitric tuff. The main mineral compositions of the ore are montmorillonite, zeolite, α-cristobalite, opal, quartz, plagioclase and biotite. Microscopically, montmorillonite fills up the interspaces of glass fragments, and is also formed in these marginal zones. Most of zeolite, α-cristobalite and opal are probably included in glass fragments. X-ray investigation shows that bentonite in water is mechanically divided into montmorillonite group and zeolite one which is identified as clinoptilolite. The differential thermal analysis curve of the material shows no remarkable thermal peak up to 1, 000°C. X-ray powder reflections after heating at 100°C, ......, 800°C, 850°C, 900°C and 1, 000°C and effects of the treatments with HCl against the material do not completely agree with the already known data of clinoptilolite. The rate of swelling of the bentonite is related to the shape of 15_??_; peak of X-ray reflection pattern, and it decreases by repetition of swelling and drying. The cation-exchange capacity of the bentonite is 96 me/100gr. It is considered that the existence of the hydrothermal sulfides ore deposits in this mining area, the relation with the division of the strata and the zonal arrangement of zeolities, the mode of occurrence of the bentonite, and the silicification and adulariazation of the country rocks show that the Hattari bentonite deposits might be formed by a diagenesis and a hydrothermal alteration of vitric tuff.

Bentonite deposits at Hattari, Hokkaido (I)

The Hattari bentonite deposits which are situated at the southwestern end of the Shakotan Peninsula occur in the Miocene green tuff formation. This formation in the neighborhood of the deposits is divided into the following three zones from the lower side by kinds of zeolites in the tuff: (1) Analcime zone in the northeastern part of this mining area. (2) Non-zeolite zone in the middle part. (3) Clinoptilolite zone in the southwestern part. These zones do not always correspond with the subdivision of the strata. The bentonite deposits are found in the clinoptilolite zone and the ore bodies form irregularly lenticular beds. The original rock of the bentonite is rhyolitic vitric tuff. The main mineral compositions of the ore are montmorillonite, zeolite, α-cristobalite, opal, quartz, plagioclase and biotite. Microscopically, montmorillonite fills up the interspaces of glass fragments, and is also formed in these marginal zones. Most of zeolite, α-cristobalite and opal are probably included in glass fragments. X-ray investigation shows that bentonite in water is mechanically divided into montmorillonite group and zeolite one which is identified as clinoptilolite. The differential thermal analysis curve of the material shows no remarkable thermal peak up to 1, 000°C. X-ray powder reflections after heating at 100°C, ......, 800°C, 850°C, 900°C and 1, 000°C and effects of the treatments with HCl against the material do not completely agree with the already known data of clinoptilolite. The rate of swelling of the bentonite is related to the shape of 15_??_; peak of X-ray reflection pattern, and it decreases by repetition of swelling and drying. The cation-exchange capacity of the bentonite is 96 me/100gr. It is considered that the existence of the hydrothermal sulfides ore deposits in this mining area, the relation with the division of the strata and the zonal arrangement of zeolities, the mode of occurrence of the bentonite, and the silicification and adulariazation of the country rocks show that the Hattari bentonite deposits might be formed by a diagenesis and a hydrothermal alteration of vitric tuff.

Geology and ore deposits of the Shakotan Peninsula, southeastern Hokkaido (II)

A dome structure formed of successive pyroclastic accumlation of so-called “green tuff effusion” is the main geologic constituent of the Shakotan Peninsula, southwestern Hokkaido. Igneous effusion and intrusion held in the district are carried wholly concordant to this dome structure; intrusive bodies are prefered to the central part of the dome and younger effusives are arranged to the peripheral part. Further, prominent mineralized zones closely allied to this geologic structure are known in this volcanic field. They are arranged to the cross direction of the axis of the peninsula. With them, interesting zonal distribution of ore deposits such arrangement as (1) Mn (Pb, Zn) deposits disposed to the central part of the dome succeeded by (2)|Cu, Pb, Zn (Au, Ag) deposits, (3) FeS2 deposits, and (4) BaSO4 deposits to the outer parts, are well ascertained. Of these deposits, some peculiar features of ore mineral are mentioned. They are unusual occurrences of pyrrhotite and molybdenite in the (1) Mn (Pb, Zn) deposits, realgar and orpiment in the (2) Cu, Pb, Zn) (Au, Ag) deposits and stibnite in the (4) BaSO4 deposits. The trace elements associated with these deposits have also peculiar behaviours. High concentration of W in the rhodochrosite from the (1) Mn (Pb, Zn) deposits, and Bi, Mo, Sn in the sulphide minerals from the (2) Cu, Pb, Zn (Au, Ag) deposits are their prominent features. Several varieties of wall rock alteration are mentioned with these ore deposits. Although sezicite-quartz and montmorillonite-kaolinite-quartz associations are the common feature of wall rock alteration of them, carbon-itization around the (1) Mn (Pb, Zn) deposits, occurrence of alunite, diaspore or jarosite with the (3) FeS2 deposits and the (4) BaSO4 deposits are the peculiar feature of this ore field. Their peculiarity is well serve for the prospecting researches.

Geology and ore deposits of the Shakotan Peninsula, southwestern Hokkaido (I)

A dome structure formed of successive pyroclastic accumlation of so-called “green tuff effusion” is the main geologic constituent of the Shakotan Peninsula, southwestern Hokkaido. Igneous effusion and intrusion held in the district are carried wholly concordant to this dome structure; intrusive bodies are prefered to the central part of the dome and younger effusives are arranged to the peripheral part. Further, prominent mineralized zones closely allied to this geologic structure are known in this volcanic field. They are arranged to the cross direction of the axis of the peninsula. With them, interesting zonal distribution of ore deposits such arrangement as (1) Mn (Pb, Zn) deposits disposed to the central part of the dome succeeded by (2)|Cu, Pb, Zn (Au, Ag) deposits, (3) FeS2 deposits, and (4) BaSO4 deposits to the outer parts, are well ascertained. Of these deposits, some peculiar features of ore mineral are mentioned. They are unusual occurrences of pyrrhotite and molybdenite in the (1) Mn (Pb, Zn) deposits, realgar and orpiment in the (2) Cu, Pb, Zn) (Au, Ag) deposits and stibnite in the (4) BaSO4 deposits. The trace elements associated with these deposits have also peculiar behaviours. High concentration of W in the rhodochrosite from the (1) Mn (Pb, Zn) deposits, and Bi, Mo, Sn in the sulphide minerals from the (2) Cu, Pb, Zn (Au, Ag) deposits are their prominent features. Several varieties of wall rock alteration are mentioned with these ore deposits. Although sezicite-quartz and montmorillonite-kaolinite-quartz associations are the common feature of wall rock alteration of them, carbon-itization around the (1) Mn (Pb, Zn) deposits, occurrence of alunite, diaspore or jarosite with the (3) FeS2 deposits and the (4) BaSO4 deposits are the peculiar feature of this ore field. Their peculiarity is well serve for the prospecting researches.

Occurrence of ferberite from Obanazawa Mine, Yamagata Prefecture, and its significances in the mineralization in the green tuff region

The Obanazawa mine is situated about 9.5km north-east of Obanazawa City, Yamagata Prefecture, northeastern Japan. The ore deposit is made up of copper-zinc quartz veins developed in dacite and dacitictuff of Miocene age. Ore minerals are chalcopyrite, sphalerite, pyrite, tetrahedrite and ferberite. The pyrite has either pentagonal dodecahedral form or colloform textures. This is the first occurrence of ferberite in the green tuff region of the inner zone of northeastern Japan. Hexagonal; platy crystals of pyrite are observed in the vein found in the Komatazawa valley. It seems that they were crystallized as pyrrhotite single crystals and altered to pyrite aggregates after the formation of the vein. Gangue mineral is quartz accompanied by a small amount of barite. Argillization (mainly sericitization) and silicification are distinguished. Ferberite was identified by means of X-ray and chemical analysis; the composition is (Fe0.90 Mn0.10)WO4. Occurrence of ferberite and pyrite after pyrrhotite means that the veins may have formed at high temperature but the properties of other vein minerals suggest that they crystallized at low temperature. They have been explained as a telescoping phenomena of xenothermal type deposits in the greentuff region. The Obanazawa mine is situated at the intersection of N-S and NWSE main structural lines of northeastern Japan ; the basement of this area seems to be uplifted. The mineral assemblages of this ore deposit may be explained by assuming that a subvolcanic magma chamber exists in this area.

Alteration Minerals of Green tuffs in the Uchimura District, Nagano Prefecture (Part 1)

Alteration Minerals of Green tuffs in the Uchimura District, Nagano Prefecture (Part 1)

COASTAL TERRACES OF THE SADO ISLAND, JAPAN

The Sado Island with 857 km2 in area is situated in the Japan Sea, about 35 km off Honshu. This islandd consists of two regions, Osado and Kosado. The former region which lies in the northern half is larger than the latter and also higher in altitude, and considered to be a tilted block with steeper foreslopes on the east side. This area is composed mainly of volcanic rocks such as andesite, liperite, basalt, and Miocen green tuff. Surrounding this island are coastal terraces developed widely. The author surveyed these coastal terraces and their deposits in the Osado region, in order to clarify their distribution, altitude, and nature and to consider the geomorphic history. The main results are summarized as follows: 1) The coastal terraces are divided into six plains owing to their altitude and continuity. They are as follows: the first terrace (160-220 m in altitude), second (80-140 m), third (60-120 m), fourth (35-70 m), fifth (25-40 m), and the sixth (5-8 m). 2) These terraces are well developed in the western coastal region in general. On the east side, however, they are no more than a fragmentary distribution. Among the terraces of the Osado region, the third and fourth terraces show a broad and cotinuous distribution. The sixth terrace is also developed all around the island in spite of the limited width. 3) Considering from the thickness and facies of the terrace deposits, the nature of the terrace plains can be classified into four groups. A a In the western coastal region, every terrace plain is of a marine origing formed by striking abrasion of the open sea. B: On the coast along the Mano Bay, the terraces are thought to be of a marine origin formed by the cut and built action of waves in the inland bay. C: In the Kuninaka Plain, the second and third terraces are elevated fans built by the rivers from the northern mountains. On the contrary, the fourth terrace is a dissected coastal plain which consists of thicker neritic sediments deposited in the inland bay. D: In the eastern coastal region, marine terraces are hardly recognized, and most of the flat plains are very small elevated fans consisting of poorly sorted boulders transported by the torrential streams down from the steep slopes. 4) The sixth terrace continues to the alluvial plain of the Kuninaka area, composed of marine alluvial deposits containing the fauna which indicates warmer water temperautre than the present sea in the vicinity and having about 70 m in thickness. Therefore, the formation of the sixth terrace plain is to be correlated with the transgression of early alluvial age which is recognized at many places in Japan. As for the fourth terrace which has a wide distribution and thicker neritic sediments, it may be considered that it was built by the transgression preceeding the regression of the last glacial age just before the alluvial trans-gression. 5) The differences in the character of terrace plains which were mentioned in 3) seem to haue been influenced chiefly by the asymmetry of topography and the condition whether open-sea-facing or not. Rock control is recognized where stacks are found on the terrace plains in the volcanic rock areas of Osado. Concerning the formation of the terrace as a whole, however, it is of the secondary importance, since topographic differences such as those of slopes seem to be the primary differentiating causes. 6) On every marine terrace plain, the elevations of the ancient strand lines increase in an accelerated manner towards the middle part of both sides of the Osado coasts, and this tendency is more evident on the older terraces. This means the upwarping movement with the axis at the middle part of the island has continued since the formation of the first terrace plain.

Geology in the Northern District of Ueda City, Nagano Prefecture, with Special Reference to Green Tuffs

Geology in the Northern District of Ueda City, Nagano Prefecture, with Special Reference to Green Tuffs

Miocene Volcanic rocks in green tuff region, northeast Japan

Miocene Volcanic rocks in green tuff region, northeast Japan

Une impregnation plombo-zincifere dans les tufs rhyolitiques de la Finosa, pres Ghisoni (Corse)

Abstract The Finosa locality, 4 km east of Ghisoni (central Corsica), is situated in the northern part of a series of pyroclastic and detrital formations of probable Permian or upper Carboniferous age. The section studied includes ignimbrites with long sinuous xenoliths of recrystallized rhyolitic glass, alternating green and red tuffs, agglomerates, arkoses, breccia, and limestone. The mineralization is stratiform, emplaced by substitution in the rhyolitic tuff at the expense of the vitreous matrix. Mineralization in the green tuffs was arrested by the lateral passage to the red facies. The main locality is situated where the tuffs are crushed by a protuberance from the roof of the underlying granite basement complex. The Finosa mineralization exhibits marked vertical zonation. The minerals encountered are listed according to their relative abundance showing a predominance of sphalerite and galena. These mineralized deposits are classified as mesothermal beds impregnated and substituted in the collapse zones of the siliceous rocks. The mineralization is related to the terminal phases of the Hercynian orogeny.

Geology and Hydrocarbon Deposits of the Shonai Basin in Yamagata Prefecture, Japan

Recent deep drilling by Teikoku Oil Co. is adding much new subsurface geologic information, making possible an interpretation of the central portion of Shonai Plain. The present study is a report on the subsurface stratigraphy and the structure of that region, related to hydrocarbon deposit. Three matters in particular are reported. 1) There is a newly discovered Jurizuka Uplift which is gently descending to Sakata city and increasing the thickness of the tertiary formation to the north. 2) The gentle anticlinal structure is disclosed near Sagoshi and its core is composed of the pyroclastic sediment of green tuff formation. On the crestal part of this anticrine, a small amount of hydrocarbon is found, but not so productive as the lacking of the potential reservoir. 3) The writer discusses the petroleum accumulation in Narahashi-Ishinazaka oil field, related to the sedimentation and the growth history of each anticline in Shonai Basin.

Petrology of the granitic rocks which constitute the basements of the green tuffs in the borderland of the Japan Sea of the Tohoku district, Japan

Petrology of the granitic rocks which constitute the basements of the green tuffs in the borderland of the Japan Sea of the Tohoku district, Japan

ON THE AGE OF METAMORPHISM IN THE JAPANESE ISLANDS

The distribution, lithology, and previously held theories on age of metamorphic activity in Japan are outlined. Precise age determination of each metamorphic complex is still uncertain. The latest was probably Miocene, the earliest either Precambrian or as late as Devonian. Miocene metamorphism affected the so-called green tuff region of the Inner zone of Japan. The Hida gneiss is the result of the oldest age of metamorphism. Absolute age determination of 230 x 106 years has been made of minerals in the Ryoke gneiss although recurring metamorphism has been shown for its area. Considerable granite emplacement occurred during the Cretaceous and early Tertiary. The age of metamorphism resulting in the Sambagawa-Mikabu complexes is much in dispute but is probably older than late Triassic. M. Russell