1996 Fiscal Year Final Research Report Summary
Magma mixing process by fractal dimensions
| Project/Area Number |
06640606
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Petrology/Mineralogy/Science of ore deposit
|
|---|
| Research Institution | Hokkaido University of Education |
|---|
Principal Investigator |
WADA Keiji Hokkaido University of Education at Asahikawa Assistant Professor, 教育学部・旭川校, 助教授 (50167748)
|
|---|
| Project Period (FY) |
1994 – 1996
|
| Keywords | magma mixing / fractal / fractal dimensions / mafic inclusions / plagioclase / magma chamber / Me-akan volcano / Taisetsu volcano |
|---|
| Research Abstract |
1.Geological survey of Me-akan and Taisetsu volcanoes was performed with special reference to the volcanic history and sampling for heterogeneous ejecta including mafic inclusions.
2.Chemical analyzes of the rocks and minerals of Me-akan and Taisetsu volcanoes were carried out with XRF and EPMA achines. Chemical zonings at the rim of phenocrysts indicate that andesite and dacite magmas were erupted through the multi-stage magma mixing in magma chamber and conduit.
3.Measured fractal dimensions of morphological patterns of heterogeneous ejecta from Me-akan volcano vary from 0.9 to 1.6, which are intimately correlated with mixing development stage and flow mechanism of magmas. In the case of pyroclastic eruptions, mixed magmas are in a turbulent state on account of higher ascending rate, which yields higher fractal dimensions. As mixing proceeds fractal dimensions decrease, and then perfect homogenization between felsic and mafic magmas causes the disappearance of the fractal structure to form intermediate composition magmas.
Mafic inclusions have a key role in understanding the mixing process in magma chamber and conduit. The mafic inclusions in lavas from Taisetsu volcano are classified into three types based on the plagioclase texture. As a result of constraints for these mafic inclusions, multi-stage mixing scenario was proposed.
|
