In the lavas of Kayodake, Komagatake and Iwate volcanic groups of the Nasu volcanic zone in the north-eastern Japan, there are many basalts and basic andesites which contain much large plagioclase phenocrysts (up to 2cm.) of anorthitic composition (An 95). Particularly the lowest lava of the Kayodake volcanic group contains plagioclase phenocrysts more than 43 per cent in volume; therefore its A1₂0₃ and CaO contents attain to 23.74 and 12.34 per cent, respectively. Its chemical composition resembles to that of anorthositic gabbro or kenningite.
Regarding to the A1₂0₃, this is probably highest value ever reported in the world in the effusive form. It is considered that the origin of such lavas of abnormal composition should be attributed to the floating up of anorthite crystals and to the sinking down of olivine and pyroxene crystals formed in the early stage.

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九州地方の主な安山岩類,すなわち第三紀琉球火出帯に属する肥薩火山区の輝石安山岩類,第四紀疏球火山帯の代表的輝石安山岩類および第四紀の火山である,いわゆる大山火山帯に属する雲仙,由布岳および両子出などの角閃石安山岩類その他に副成分として含有されるジルコンを分離し,主にその色(群色)・結晶形・晶相・晶癖などを観察測定した結果を簡単に要約すると次のとおりである。
1) 肉眼観察によるジルレコンの色(群色)はここに取扱つた試料では(1) 淡紅色ないしピンク色, (2) ピンク色ないし淡いピンク色, (3) 無色ないし淡灰色, (4) 黄褐色ないし淡黄褐色に分類されるが,これらのうち第三紀の岩石中のものは殆んど(2)に属し,第四紀の岩石中のものは(2)および(3)に属する。またまれに(4)の色を示す場合がある。
琉球火山帯での第三紀安山岩中のジルコンと第四紀安山岩中のジルコンでは一般に前者が淡いピンク色を帯びるのに対して後者はピンク色を示さず,無色,灰色,淡黄褐色などを呈する。しかし一般に第四紀安山岩中に含有されるジルコンは,第三紀の岩石に比較してその量が著しく少いかまたは桜島・阿蘇などにおける如く殆んど含まれない¹⁾。
2) 安山岩類中のジルコン結晶の大きさは一般にきわめて小さいが輝石安山崇中のジルコンは角閃安山岩中のジルコンよりもさらに小さい。すなわち前者では0.04×0.02mmないし0.25×0.10mm,後者では0.08×0.05mmないし0.25×0.15mmの粒状結晶が普通であるが長柱状結晶も少量認められる。
次に伸長比は全般的にみて1～2.0の範囲のものが80%を占める。そのうち1～1.5又は1.6～2.0のものがピークを示す。
3) 次に晶相および晶癖を夫々5型および3型に分類し各々の頻度および関係図を作製した。その結果,明らかに安山岩中のジルコンの晶相および晶癖と深成岩中のジルコンのそれとは異る傾向がみられる。また輝石安山岩中のジルコンと角閃石安山岩中のジルコンとを比較すれば,両種の間には可成り相違がみられる。
また一つの火山区域内ではジルコン結晶の晶相および晶癖には類似性があるか否かはこれから研究を進めてゆく段階であつて現在のところまだ不明であるが,肥薩火山区の輝石安山岩中のジルコンを例:ことると,それらの間には可成りの差異が認められる。しかし例えば琉球火山帯と大山火山帯の岩石中のジルコンとの間には明かに相違が認められる。
4) 多くの岩石中にはジルコンの自形結晶のほか融蝕されて,または磨耗されて丸味を帯びるものや,或は破砕された結晶片を多量に含むことがある。破砕結晶の一部は勿論岩石粉砕時におけるものもあるが殆んど同じ方法で同じ程度に粉砕し分離したジルコン中に,殆んど破砕片を含まず自形結晶のみの場合が少くないのに対し,一方ある試料では著しく多量の破砕片を含む事実などから考えると,破砕結晶はジルコン自身の破砕性に差異がない限りでは,岩石の粉砕以前からすでに破砕されていたのではないかと思われる。
そうであるとすれば,融蝕形又は破砕片を普遍的に含む岩石では,マグマの混成作用又は同化作用が行われたと推定される有力な証拠としてこれらが考えられはしないか。例えば肥薩火山区の岩石で鬼岳系および上場系の岩石のジルコンに融蝕形を示すものが多く,矢筈長熔岩には少いことは,前者ではマグマの混成作用・同化作用が有力に働き,後者ではそれが少いと筆者が,岩石学的ならびに岩石化学的研究から結論したことを裏がきするものではなかろうか。
5) 霧島火山新期熔岩におけるように,殆んど大部分のジルコン結晶がmetamictiza-tionを受けており,透明な正常ジルコンが殆んど含まれないことがある。新しい熔岩中のジルコンがこのような変質作用を受けているのは,古い時代の岩石から由来した捕獲結晶であろうか。或いはジルコンの結晶講造又は放射能源の問題に帰せられるぺきであろうか。何れも可能性のある因子であるが,本問題はジルコン研究に課せられた多くの未解決の問題とともに将来の詳細な研究によつて解決されるべき重要な課題の一であろう。

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On the magnetite and the hematite from the cupriferous iron sulphide deposits, such as the Shingü, Shirataki, Sazare, and Kõtsu mines, occurring in the Sambagawa crystalline schist zone, the writer has chiefly investigated occurrence, various textures under the ore-microscope distribution of minor elements and magnetic property.
It is the purpose of this paper to give some interpretation on the genesis of Kieslager.

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The paragenesis of ludwigite has been frequently described by Geijer, Watanabe, Tilley and others, however, that of paigeite has not been described in detail. The present paper purports to describe the paragenesis of paigeite from the Kamaishi mine, Iwate Pref., Japan, and to clarify the difference in the paragenesis of paigeite and ludwigite, moreover, to discuss their genesis.
Assuming a similarity of temperature and pressure during the formation of paragenesis of paigeite and ludwigite, and that chemical potentials of H₂O, CO₂, Na₂O, K₂O, B₂O₃ in the pore fluids participating in the formation of these parageneses were alike, and further that changes in the chemical potential of Fe had no effect on the composition of diopside, forsterite, phlogopite, spinel and tourmaline, but that, they it may be had a striking effect on the composition of the mineral of ludwigite series, concluded that the paragenesis of paigeite was formed in a condition where the chemical potential of O₂ in the pore fluids was low and that of Fe in the system was high, whereas, the paragenesis of ludwigite was formed in a condition where the chemical potential of O₂ was high and that of Fe was low.

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Petrologic and sedimentalogic studies on the source-rocks of petroleum in the Teradomari folding zone in Niigata Prefecture have been carried out. The extractive organic constituents of the fine grained clastics, so-called grey shale, black shale and hard shale, were determined. The relation ships between the stratigraphic distribution of the organic constituents and the lithologic features and other characteristics of the source rocks themselves were discussed in the present paper.
It may be suggested that the results afford important criteria for the interpretation of complex phenomena related with the Neogene sediments developed in the oil-fields of Japan.

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This paper deals with the proposal of a new hypothesis for inflammable natural gas pools of special type found theoretically by the writer in 1948 and has been studied in succession. The hypothesis for the special gas pools is characterized essentially by inflamable natural gas dissolved in the underground water with saturate solubility without oil. The saturate degree is generally determined by the physical and chemical conditions of the solvent water under the ground. The reservoir pressure and temperature are the main factors which control the solubility of inflammable natural gas for the undergound water.
Many productive gas wells for the gas pools of this type have already successfully drilled and now under drilling in many areas in Japan from Hokkaidõ to Kyüshü, especially vividful in Niigata plain and Southern Kantõ basin. The gas pools of this type are important for our country because more than 80% of total inflammable natural gas production of Japan is occupied by the gas of this type. Many theoritical results have been obtained by us by the observation of these gas fields during last eleven years from 1948 to 1959. These theories derived out of hypothesis proposed here seem not only true, but has no contradiction among many theoritical explanations of the gas field phenomena each other on the point of geological and geophysical views.
As the examples of derived theories from the new hypothesis, this paper also takes up some themes and their outlines.
These themes are shown as follows; (1) vertical disolved gas distribution in the pore water of all strata in the gas field, (2) the gas contents in the inflammable natural gas pools dissolved-in-water type, (3) geochemical prospecting of gas fields, (4) syncline theory for inflammable natural gas pools dissolved-in-water type, (5) arc type exploitation method, (6) calculation of self flowing power for the flowing gas wells, (7) enrichment of inflammable natural gas pools dissolved-in-water type, (8) calculation of gas reserves, (9) stability of natural gas production, (10) generation of gas pools with abnormally high gas-water ratio.
As a result, many theories derived from the same one hypothesis have given us nearly enough explanations for many phenomena on these gas pools and have no contradiction among these explanations each other.
Therefore this basemental hypothesis “the natural gas in the gas pools with under ground water exists in the underground water with dissolved feature” can be considered as the one of the new believable theory.

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