Geochemical Studies on volcanoes in the Canarian islands.

加那利群岛火山的地球化学研究。

基本信息

批准号：
07041095
负责人：
WAKITA Hiroshi
金额：
$ 1.41万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至无数据
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07041095/
关键词：
Canarian Islands Helium Isotope Ratio Hot Spot Volcanism Lower Mantle Oceanic Island

项目摘要

Helium isotopic ratios in natural systems are a potential tool for detecting mantelic degassing from different tectonics settings such as mid-ocean ridge basalts, oceanic volcanic islands, are volcanism, and intraplate continental volcanism environments. Helium isotopic signature from mantle plume regions such as Hawaii, Iceland, and Yellowstone range from 9 to 30 Ra which indicates helium degassing from the lower mantle.Several hypothesis have been considered for the origin of the volcanic activity in the Canary Islands. Helium isotope systematics applied to the actual degassing will provide an additional insight to the discussion on whether the Canarian archipelago is indeed a hot spot.More than 40 gas samples have been collected from actual degassing sites at La Palma, Tenerife and Lanzarote islands.The observed ^3He/^4He ratios vary significantly from 1.02 to 9.63 Ra, being Ra (atmospheric ratio) =1.40*10^<-6>. Most of the samples show isotopic ratios higher than atmospheric value indicating a contribution of mantle-derived helium. The highest observed helium isotopic ratio, 9.63 Ra, was detected inside Taburiente caldera (La Palma Is.). This ^3He/^4He ratio is higher than the typical MORB-type helium 8(]SY.+-.])1 Ra and agrees well with a plume-type helium. Such evidence supports that the volcanic-hydrothermal discharge in La Palma island is related to magma derived from a rising hot zone.The geographical distribution of the ^3He/^4He ratios obtained in this Field Research shows the highest level of helium-3 emission on the westernmost zone of the Canarian archipelago. This ^3He/^4He ratio would imply the existence of a helium source degassing from the lower mantle. The result of this International Scientific Research Program add an additional insight to the controversy on the origin of the volcanic activity of the Canary islands which seems to be related to a hot spot model.

天然系统中的氦同位素比是检测不同构造设置的壁炉脱牙的潜在工具，例如中海脊玄武岩，海洋火山岛，是火山群和岩内大陆火山主义环境。来自夏威夷，冰岛和黄石等地幔羽状区域的氦同位素特征范围为9至30 ra，表明从下地幔的氦气脱气。为加那利群岛的火山活动起源，已经考虑了几个假设。适用于实际脱气的氦同位素系统学将为讨论是否确实是一个热点，从而为讨论提供了一个额外的见解。从La Palma，Tenerife和Lanzarote岛上收集了40多个气体样本，观察到的 ^3he/ ^4He比率从1.02至9.63 raver raviio carriio fare ^3he/ ^4he比例（均为9.63 ra）（均为9.63 RA）。 = 1.40*10^<-6>。大多数样品显示的同位素比高于大气值，表明地幔衍生氦的贡献。在Taburiente Caldera（La Palma IS。）内检测到最高观察到的氦同位素比为9.63 Ra。这个 ^3he/ ^4he比率高于典型的MORB型氦8（]sy。+ - 。]）1 RA，并且与羽状型氦气很好地吻合。这样的证据支持，拉帕尔马岛的火山热放电与源自升高的热区的岩浆有关。在该田间研究中获得的 ^3he/ ^4He比率的地理分布表明，加拿大群岛最西端的氦3发射水平最高。这个 ^3he/ ^4he比率将暗示存在氦源从下地幔脱气。这项国际科学研究计划的结果增加了关于加那利群岛火山活动起源的争议，这似乎与热点模型有关。