|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1996 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1995 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Conclusions : Most significant knowledge obtained through the research is as follows ;
(1) Multiply chilled-margin dykes
(2) Conditions of multiple dyke formation
(3) Multiple dykes are common in arc volcanoes and slow spreading ridges, while they may be rare in fast spreading ridges.
Multiply chilled-margin dykes : Field research done on Fudeshima Volcano, Izu Oshima, Older volcanics of northern Yatsugatake Volcano and Troodos Ophiolite, Cyprus, revealed the existence of a sort of multiple dykes, which have multiply chilled margins 1-20 cm thick only in several tens of centimeters from the dyke selvages. Such dykes indicate that pulse of magma intrusions repeated in a short time interval.
Conditions of multiple dyke formation : In Troodos Ophiolite, Presence of multiple dykes are confined to near the layred gabbros. On the contrary, sheeted dykes occurring in stratigraphically higher horizons are of simple dykes. This suggests the conditions which favor the formation of multiple dykes to be 1) repetition of magma intrusion, and 2) large ratios of frequency of magma intrusion/solidification time of dykes (F/S ratio).
Troodos vs. Semail : All sheeted dykes examined in the Semail Ophiolite are simple. This suggests that in Semail, 1) magma did not intrude as pulse, or 2) F/S ratio was very high. In addition to this, generation of magma pulse may be controlled by the ratio of volume of recharged magma/that of magma chamber.
トル-ドスvs. オマーン:オマーンではシート状岩脈群は全て単純岩脈で,1m以下が最も多い.重複岩脈が島弧火山下,低速拡大軸のトル-ドスにあって,高速拡大軸のオマーンにないことから,オマーンでは1)マグマパルスは発生しなかった,2) F/S比が非常に高かった,の可能性が考えられる.また,パルスの発生は供給マグマの体積/マグマ溜りの体積に支配されている可能性がある.