日本海形成に伴う西南日本の火山岩類の岩石化学-化学組成と同位体組成からの検討

• Project/Area Number: 06640582
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: Geology
• Research Institution: Shimane University
• Principal Investigator: MORRIS Paul A. 島根大学, 理学部, 助教授 (70252898)
• Co-Investigator(Kenkyū-buntansha): 加々美 寛雄 岡山大学, 地球内部研究センター, 助教授 (20108179) ; 沢田 順弘 島根大学, 理学部, 助教授 (80196328) ; 飯泉 滋 島根大学, 理学部, 教授 (80032639)
• Project Period (FY): 1994
• Project Status: Completed (Fiscal Year 1994)
• Budget Amount: ¥1,800,000 (Direct Cost: ¥1,800,000); Fiscal Year 1994: ¥1,800,000 (Direct Cost: ¥1,800,000)
• Keywords: MATSUE FORMATION / ISOTOPE / WHOLE-ROCK CHEMISTRY / OKI DOZEN ISLAND / QUATERNARY ARC / SLAB MELTING

Research Abstract

Three projects have been undertaken.The first involved sampling and analysis of ll Ma old basalts of the Matsue Formation,which outcrops within a 5 km radius of Matsue city.Representative samples were analysed for major and trace element oxides,rare earth elements,and ^<87>Sr/^<86>Sr and ^<143>Nd/^<144>Nd.three samples were dated by K/Ar whole rock.Preliminary results show that two basalt types are present,one representing melting of an isotopically depleted mantle source,and the other,melting of an isotopically and trace element enriched source.Most Matsue Formation basalts are mixtures of these two end members.The range in isotope chemistry spans that known for all of southwest Japan.The limited age and extent of the Matsue Formation basalts is interpreted as representing interaction of a small mantle plume with overlying relatively depleted mantle.The second project has involved whole-rock and isotope analysis,with K/Ar age dating of Miocene volcanic rocks from Oki Dozen Island.This approach has revised the volcanic history,showing that the central cone trachyte,and syenite on Oki Dozen evolved together as an early igneous phase,before the eruption of basaltic through to rhyolitic rocks that make up the main volcanic shield.Earlier studies had argued that the central cone trachyte occurred part the way through the shield building phase,and the position of the syenite was unknown.The third project has been to examine the whole-rock and isotope chemistry of Quaternary volca

Research Products

• [Publications] MORRIS PAUL A.: "SLAB MELTING AS AN EXPLANATION OF QUATERNARY VOLCANISM AND ASEEISMICITY IN SOUTHWEST JAPAN." CEOLOCY. (IN PRESS). (1995)
• [Publications] IIZUMI S,MAEHARA K,MORRIS PA,SAWADA Y.: "SR ISOTOPE DATA OF SOME CST ROCK REFERENCE SAMPLES." MEMOIRS OF THE FACULTY OF SCIENCE,SHIMANE UNIVERSITY. 28. 83-86 (1994)
• [Publications] MORRIS PAUL A.: "SLAB MELTING AS THE CANSE OF VOLCANISM AND ASEISMICITY IN SOUTHWEST JAPAN." ABSTRACTS WITH PROCRANS.JOINT ANNUAL CENERAL MEETING MIN.SOC.JAPAN,SOC.OF RES.CEOL.,J.ASSOC.MIN.PET.EC.CEOL.76- (1994)