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ID 48304
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title alternative
Internal and permeability structures of Pre-Cretaceous nappe boundaries in the Inner Zone of Southwest Japan
creator
Hirose, Takehiro
subject
nappe boundary
fault
permeability
cataclasite
abstract
福井県小浜市下加斗片地域に露出している丹波帯と超丹波帯のナップ境界断層帯の内部構造と浸透率構造を調べた.その結果,(1)両地質体は約3 mのカタクレーサイト帯を介して完全に固着して接しており,変形は幅0.2~3 cmの面状カタクレーサイトに集中していること,(2)断層帯では,石英や方解石,リモナイト脈,炭質物の濃集層のほか,多量の層状珪酸塩鉱物が晶出しており,流体を媒介とした活発な物質移動があったこと,(3) 本ナップ境界では,上盤に低い浸透率を示す砂岩層,下盤および断層帯ではそれより1~3桁高い浸透率を示す礫質泥岩層およびカタクレーサイト帯が分布していることがわかった.このような浸透率構造によって,断層帯内部に高間隙水圧が保持され,ナップの大規模な衝上運動が可能になったと考えられる.
abstract
We determined the internal and permeability structures of the nappe boundary between the Tamba and the Ultra-Tamba belt in the Inner Zone of Southwest Japan. Protolith of hanging wall is Permian sandstone and that of footwall is Jurassic pelitic breccia. These are stuck tightly with cataclasite zone of 3 m in width. Permeability data and structural observations of the fault zone suggest the following; (1) cataclasite is distributed in the fault zone, but most deformation is localized in 0.5 to 3 cm width foliated cataclasite zones in the hanging wall, (2) experiments at effective pressures, Pe, of 40 to 100 MPa show that permeability of the hanging wall is low (10-20 m2 at Pe > 80 MPa), while it is higher by 1-3 orders of magnitude in the footwall and the fault zone. The permeability structure implies that high pore fluid pressure could be sustained within the fault zone, which could have promoted the thrust movement.
journal title
The Journal of the Geological Society of Japan
volume
Volume 111
issue
Issue 5
start page
300
end page
307
date of issued
2005-05
publisher
日本地質学会
issn
0016-7630
1349-9963
ncid
publisher doi
language
jpn
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
© The Geological Society of Japan 2005
relation url
department
Graduate School of Science