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Comparative study of felsic magmas with explosive or not explosive eruption

爆炸性喷发与非爆炸性喷发的长英质岩浆对比研究

基本信息

批准号：
10440141
负责人：
SAWADA Yoshihiro
金额：
$ 8万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10440141/
关键词：
Quaternary volcanoes lava dome pyroclastic flow felsic magma volatile components organic matter paleomagnetism reverse thermoremanent magnetism 自己反転熱残留磁性鉱物

项目摘要

(1) On the basis of paleomagnetic and petrographical studies, it estimates that the four lava domes of Mt. Sanbe formed at 3.7-3.8 Ka. Hemoilmenite showing self-reversal of thermo-remnant magnetization was found in dacite clasts and lava from Mt. Sanbe and Mt. Daisen.(2) Laboratory experiments aimed at allowing estimation of emplacement temperatures of pyroclastic deposits flows using H/C ratios of entrained carbonized wood were carried by simulating the thermal conditions in pyroclastic flows. H/C ratios show a strong correlation with temperature. H/C thermometry was tested by natural carbonized woods and paleomagnetic blocking temperatures from Holocene pyroclastic flow deposits. Emplacement temperatures of Taiheizan pyroclastic flow deposits about 5.5km from the conduit of the Sanbe volcano were estimated 530-560℃ by these methods.(3) Organic matter was found in igneous rocks related to sediments during the generation and ascent of magmas, such as S-type felsic rocks, high Mg andesite, rocks formed by slab melting and sedimentary origin migmatite.(4) Experiments were carried out to examine transformation of sediment-derived hydrocarbons contained in felsic magma and during its solidification at middle crustal condition. Carbonaceous materials remained in all experimental products, not only as carbonate and graphite but also as solid state hydrocarbon, indicating that polymerization occurred.

(1)根据古地磁和岩石学研究，推测三别山4个熔岩穹丘形成于3.7 ~ 3.8 Ka。在三别山和岱森山英安岩碎屑和熔岩中发现了热残余磁化自反转的血红铁矿。(2)通过模拟火山碎屑流热条件，利用夹带炭化木材的H/C比值估算火山碎屑沉积流的就位温度。H/C比值与温度有较强的相关性。采用天然炭化木材和全新世火山碎屑流沉积的古磁阻温进行H/C测温。利用这些方法估算出离三别火山导管约5.5km的太黑山火山碎屑流沉积的就位温度为530 ~ 560℃。(3)在岩浆生成和上升过程中与沉积物有关的火成岩中发现有机质，如s型长英质岩、高镁安山岩、板块熔融岩和沉积源混辉岩等。(4)对中地壳条件下长英质岩浆及其凝固过程中沉积物衍生烃的转化进行了实验研究。所有实验产物中均存在碳质物质，不仅以碳酸盐和石墨的形式存在，而且以固态烃的形式存在，表明聚合发生了。