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No.26 (1979/12) >

 
Title :ジャーガルとその母材に関する研究 : 第 5 報沖縄本島, 那覇市具志および具志頭村安里土壌(層)断面の粘土鉱物(農芸化学科)
Title alternative :Studies on theJaagarusolis and their parent materials : V. Clay minerals of soil profiles at Gushi, Naha city and Asato, Gushikami-son, Okinawa Island (Department of Agricultural Chemistry)
Authors :渡嘉敷, 義浩
大屋, 一弘
Authors alternative :Tokashiki, Yoshihiro
Oya, Kazuhiro
Issue Date :11-Dec-1979
Abstract :沖縄本島南部において, 堆積様相がいずれも異なる泥灰岩層の上部にそれぞれ砂岩層(ニービ層)が堆積する那覇市具志(O-11)断面および赤褐色土層(マージ層)が堆積する具志頭村安里(O-14)断面について, 2,3の理化学性, 粘土部分の非結晶質および結晶質成分, およびシルト部分の1次鉱物組成などの特徴を調べた。ニービ層のpHは概して弱アルカリ性を示し, 砂部分は80∿90%を占めた。非結晶質成分は25∿39%で, ジチオナイト, シユウ酸ナトリウムおよび水酸化ナトリウムなどによる可溶成分はそれぞれ組成が異なり, 層間でも若干異なった。そして, 可溶成分中のFe_2O_3含量はジチオナイトで11∿18%, シユウ酸ナトリウムで4∿6%を示し, いずれも他の堆積物より多かった。残りの結晶質成分はイライトやモンモリロナイトが主体で, 他にバーミキユライトークロライト中間種, バーミキユライト, クロライト, カオリン鉱物および少量のパイロフイライトが随伴した。一方, 1次鉱物は石英が主要鉱物で, 他に長石, ダイアスポア, ドロマイト, パイロフイライトおよびクリストバライトが存在した。クチヤ層はいずれも弱アルカリ性の反応を示し, 粘土含量が9∿12%の壌土を示した。粘土部分の非結晶質成分は各可溶成分間および各層間で異なり, 特に水酸化ナトリウム可溶成分の特徴は泥灰岩層の堆積様相の差異を反映するように思われ, 断面間で著しく異なった。Fe_2O_3含量はジチオナイト可溶成分で2∿5%, シユウ酸ナトリウム可溶成分で2∿3%をそれぞれ示した。結晶質成分は81∿91%で他の堆積物よりも多く, 鉱物組成はほぼニービ層に類似するが, 粘土部分にパイロフイライトは存在せず, そしてシルト部分にカルサイトが存在してパイロフイライトおよびダイアスポアは存在しなかった。マージ層のpHは概して酸性を示し, 粘土含量は21∿40%で埴壌土∿軽埴土を示した。非結晶質成分は各可溶成分間および各層間で異なった。特にシユウ酸ナトリウム可溶成分と水酸化ナトリウム可溶成分とでは, 他の堆積物には見られない著しい特徴の差異が認められた。ジチオナイト可溶成分中のFe_2O_3含量は8∿13%で, 他方の成分中のそれは1∿2%であった。結晶質成分は68∿80%存在し, イライトやバーミキュライトークロライト中間種が主体で, 他にバーミキュライトやカオリン鉱物が随伴した。そして, これらに附随してモンモリロナイトが存在した。また, 1次鉱物としては石英が主要鉱物で, 他に長石やクリストバライトが随伴した。
Two soil profiles were selected in the southern part of Okinawa Island to characterize physical, chemical and mineralogical properties of the soil in relation to underlying parent materials. One soil profile was located at Gushi, Naha-city (Profile no. 0-11), and the soil was brown and rather sandy, which is called "niibi" by an Okinawan dialect. The other soil profile was at Asato, Gushikami-son (Profile no. 0-14), and the soil was brown and rather clayey, which is locally called "maaji". Both of the soils were underlain by marl like deposit called "kucha" in Okinawa. The dissolution method with dithionite, sodium-oxalate and sodium hydroxide was employed in addition to ordinary procedures of studying physical and chemical properties of the soil. Mineral compositions of the clay and silt fractions were also studied by the X-ray diffraction method. At the 0-11 profile the "niibi" layers were slightly alkaline. The sand fractions ranged from 80 to 90% in the fine earth. The clay fractions contained 25 to 39% of amorphous constituents. The contents of amorphous materials dissolved by dithionite, sodium-oxalate and sodium hydroxide treatments were little different among the treatments and among the layers in the "niibi" profile. Iron oxides were about 11 to 18% in the dithionite soluble material and 4 to 6% in the sodium hydroxide soluble material. Illite and montmorillonite were the major crystalline materials in the residues; vermiculite-chlorite intergrade, vermiculite, chlorite and kaolin minerals were the minor ones, and pyrophyllite was in the least quantity. In the sand fractions the primary mineral quartz was the major constituent, and also identified were feldspar, diaspore, dolomite, pyrophyllite and cristobalite in a minor quantity. At the 0-14 profile the "maaji" layers were generally acid in reaction and ranged from clay loam to light clay in texture containing 21 to 40% of clay. Amorphous constituents dissolved from the clay fractions were different in the content by the respective dissolution treatments and by the layers of "maaji", and also the difference was distinctive from those in the "niibi" layers of the 0-11 profile and in the underlain "kucha" layers of both the 0-11 and the 0-14 profile.
The difference in the composition of the amorphous material was remarkable specifically in the sodium-oxalate soluble and the sodium hydroxide soluble materials. Iron oxides in the clay fraction of the "maaji" layers were about 8 to 13% in the dithionite soluble material and about 1 to 2% in the sodium-oxalate soluble material. The main crystalline minerals in the clay fractions were illite and vermiculite-chlorite intergrade accompanied by small quantitis of vermiculite, kaolin minerals and montmorillonite. In the silt fractions identified were quartz in a large quantity, and feldspar and cristobalite in a small quantity. The marl like "kucha" layers at the both profiles of 0-11 and 0-14 were all slightly alkaline in reaction and loam in texture having 9 to 12% of clay. Different amounts of amorphous materials were obtained from the clay fractions by the respective dissolution treatments and by the "kucha" layers. A remarkable difference was occurred specifically in the composition (SiO_2/Al_2O_3 ratio) of the sodium hydroxide soluble material among the "kucha" layers within a profile and between the "kucha" layers of the 0-11 and the 0-14 profiles. Iron oxides in the clay fractions of the "kucha" layers were 2 to 5% in the dithionite soluble material and 2 to 3% in the sodium-oxalate soluble material, respectively. Crystalline materials were 81 to 91% in the clay fractions, the figures of which were much higher than those in the "niibi" and "maaji" layers. The mineral compositions in the "kucha" layers were similar to those of the "niibi" layers except for the absence of pyrophyllite in the clay fractions and the absence of pyrophyllite and diaspore but the presence of calcite in the silt fractions.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/4147
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.26 p.69 -82
Appears in Collections:No.26 (1979/12)

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