According to Pliny, the name magma was used for the residue or dregs of salve [Pliny: 77]. Later, the name was used for the mother liquor of a solution, and at the end of the 18th century, the Neptunists used it for the mother liquor of rocks such as granite [Dolomieu: 1794]. The word magma was introduced by Scrope in 1825 [Scrope: 1825]. It was Fournet and Durocher who gave it its present meaning, but even after that time, stony molten material was treated as lava [Fournet: 1844, Durocher: 1845]. Vogelsang and others used the name magma for the amorphous base of porphyritic rocks, and used the term magma-basalt [Vogelsang: 1872]. Magma is now considered to be a molten fluid or paste that originates in the Earth's crust, from which igneous rocks are formed by crystallization or other solidification processes. Magma is a concept and cannot be observed. All that can be observed on the ground are materials derived from magma, and since the process of their formation is unknown, inferences are made from the results of many observations. Magma contains materials that represent all or part of igneous rocks, as well as volatile components and residual liquids that escaped during or after solidification. It is therefore a mistake to assume that the composition of a rock represents the magma that formed it. When the periphery of a magma cools rapidly, the composition of the magma is likely to be largely preserved, except for gases and vapors, but rocks show a wide range of regional differentiation, and differentiated rocks are chemically very different from parts of the magma [Niggli: 1942, Barth: 1952, Read: 1957, Read & Watson: 1962, Suzuki: 1994]. Even today, there is confusion in the way magma is described, and there are many unclear descriptions, such as whether it refers to something that is completely molten, or whether it is acceptable for the molten material to contain crystals. When using the word magma, it is important to clearly define it. The Greek word mag means kneaded mass, ointment, and in Latin, residue, or dregs. In Japanese, it is called rock sludge, and sludge refers to vinegar made from millet, called "konzu." This word also means rinsing water or soup. Source: Asakura Publishing Dictionary of Petrology Information |
プリニイによれば,マグマ(magma)という名称は膏薬の残りまたはかすに用いられていた[Pliny : 77].後になってこの名称は溶液の母液に用いられるようになり,18世紀末になってネプチュニストが花崗岩のような岩石の母液に対して使用した[Dolomieu : 1794].マグマという語はスクロープによって1825年に導入されたものである[Scrope : 1825].現在のような意味となったのはフールネとドロシャーによるが,この頃以後でも石質の熔融物質は熔岩(lava)とし扱われていた[Fournet : 1844, Durocher : 1845].フォーゲルザングたちはマグマの名称を斑状の岩石の非結晶質の基盤に用い,magma-basaltなどと使用した[Vogelsang : 1872].現在ではマグマは地殻に発生した熔融流体または糊状の塊で,この物質から結晶作用またはその他の固化の過程によって火成岩が形成されると考えられているものである.マグマとはあくまで概念的なもので実際に観測することができない.地上で観測可能なものはマグマから由来した物質であり,その形成過程が分からないので,多くの観測結果から推論がなされている.マグマは火成岩のすべてまたは一部を代表する物質を含むのみならず,固化の間または後に逸散してしまった揮発性成分や残留液体を含んでいる.それゆえ岩石の組成がその岩石を形成したマグマを代表すると仮定することは誤りである.マグマの周縁部が急冷した場合には,ガスや蒸気以外はマグマの組成が大体は保存されると考えられるが,岩石は地域的に広い範囲の分化作用を示し,分化した岩石は化学的にマグマ全体の一部で非常に異なったものとなる[Niggli : 1942, Barth : 1952, Read : 1957, Read & Watson : 1962, 鈴木 : 1994].現在でもマグマの表現には混乱があり,完全に熔融したものをいうのか,熔融体が結晶を含んでいても構わないのか,不明確な記述が多い.マグマの語を使用する際は定義をはっきりさせて使うべきである.ギリシャ語のmagはこねた塊,軟膏,ラテン語で残り,かすの意味.日本語では岩漿といい,漿とは粟で作った酢のことで“こんず”という.この語にはとぎ汁や汁の意味がある. 出典 朝倉書店岩石学辞典について 情報 |
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