Material flux through the hydrothermal circulation at the mid-ocean ridge estimated by Ophiolite

由蛇绿岩估算的大洋中脊热液循环的物质通量

• 批准号: 10640468
• 负责人: CHIBA Hitoshi
• 金额: $ 1.79万
• 依托单位: Okayama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 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/grant/KAKENHI-PROJECT-10640468/
• 关键词: Ophiolite; mid-ocean ridge; seafloor hydrothermal system; hydrothermal circulation; stable isotope ratio; material flux; オマーン; 酸素同位対比; イオウ同位対比

In order to estimate the depth of and material transfer through the hydrothermal circulation at the mid-oceanic ridge, sulfur contents and oxygen and sulfur isotopic ratios of a series of rock samples collected from the Samail Ophiolite in Oman were measured. Oxygen isotope ratios of the pillow lava unit indicates that this unit finally reacted with hydrothermal fluid whose temperature was less than 200℃ and at high water/rock ratio. In the sheeted dike complex, hydrothermal fluid whose temperature was higher than 350℃ was circulated into the boundary of the gabbro unit, if we assume that the water/rock ratio is unity in this unit. The altered gabbro might be reacted with hydrothermal fluid of 500℃ at very low water/rock ratio, 0.n. There are very good correlations between whole rock oxygen isotope ratios and whole rock strontium isotope ratios, and between whole rock oxygen isotope ratios and water content of rocks. It indicates that the oxygen isotope ratio is a very good indicator o … More f the degree of alteration. Sulfur content of the whole rock sample does not correlate with oxygen isotope ratio or strontium isotope ratio. In the pillow lave unit, sulfur content is very low because sulfur was extensively lost by hydrothermal circulation. In the sheeted dike complex unit, there are two parts : one has very low sulfur content because sulfur was lost by hydrothermal circulation and the other is enriched in sulfur compared to the original igneous sulfur content. Sulfur isotope ratio suggests that sulfur enrichment was caused by the precipitation of sulfide minerals from the hydrothermal fluid. In the gabbro unit, unaltered sample has sulfur content and sulfur isotope ratio similar to those of original igneous rock. It indicates that the sulfur loss did not occur at the bottom of the gabbro unit. If we estimate the total sulfur loss from the sheeted dike complex using the difference between average sulfur content of measured samples and original sulfur content of igneous rock, it exceed the amount of sulfur to produce the volcanogenic massive sulfide deposit which is now under mining on land. Less

为了估算大洋中脊热液循环的深度和物质转移，测量了从阿曼Samail蛇绿岩中采集的一系列岩石样品的硫含量和氧硫同位素比值。枕状熔岩单元的氧同位素特征表明，该单元最终与温度低于200℃的高水岩比热液发生了反应。在席状岩墙杂岩中，温度高于350℃的热液循环进入辉长岩单元的边界，假设该单元的水岩比为1。蚀变辉长岩可能与500℃的热液在很低的水岩比（0.1N）下发生反应。全岩氧同位素比值与全岩锶同位素比值、全岩氧同位素比值与岩石含水量之间有很好的相关性。这表明氧同位素比值是一个很好的指示 ...更多信息 改变的程度。全岩样品的硫含量与氧同位素比值或锶同位素比值没有相关性。在枕状层单元中，由于热液循环使硫大量流失，硫含量很低。在席状岩墙复合体单元中，存在两个部分：一部分由于热液循环而损失硫，因此硫含量很低，另一部分相对于原始火成岩硫含量富集硫。硫同位素比值表明硫的富集是由热液中硫化物矿物的沉淀引起的。在辉长岩单元中，未蚀变样品的硫含量和硫同位素比值与原始火成岩相似。这说明辉长岩单元底部没有发生硫的流失。如果用实测样品的平均硫含量与火成岩原始硫含量之差来估算席状岩墙复合体的硫损失总量，则超过了目前正在陆地开采的火山成因块状硫化物存款的硫损失量。少

项目成果

Kataoka, S.: "Topography and fluid geochemistry of the Iheya North Knoll seafloor hydrothermal system in the Ikinawa Trough."JAMSTEC J.Deep Sea Res.. 16(II). 1-7 (2000)

Kataoka, S.：“Ikinawa 海槽 Iheya North Knoll 海底热液系统的地形和流体地球化学。”JAMSTEC J.Deep Sea Res.. 16(II)。

D.A.Teagle.et al.: "Dissectiog an active hydrothenmal deposit : the strontium and Oxygen Isotope anatomy of the TAG hydrothermal mound." Chemical Geology. 149. 1-24 (1998)

D.A.Teagle.等人：“解剖活跃的热液沉积物：TAG 热液丘的锶和氧同位素解剖结构。”

Kawahata,H.: "Sr Isotope Geochemistry and Hydrothermal Alteration of the Oman Ophiolite"Journal of Geophysical Research. (印刷中). (2001)

Kawahata, H.：“阿曼蛇绿岩的高级同位素地球化学和热液蚀变”地球物理研究杂志（2001 年）。

Chiba., H.: "Hydrothermal circulation in Samail Ophiolite in Oman estimated by oxygen isotope ratio."Monthly Chikyu. 21. 372-376 (1999)

Chiba., H.：“通过氧同位素比估算阿曼萨梅尔蛇绿岩的热液循环。”每月 Chikyu。

Chiba, H.: "Stable isotope study of anhydrite and sulfide minerals at the TAG mound, Mid Atlantic Ridge 26°N, ODP Leg 158."Proceedings of the Ocean Drilling Program. 158. 129-141 (1998)

Chiba, H.：“TAG 土丘的硬石膏和硫化物矿物的稳定同位素研究，大西洋中脊 26°N，ODP Leg 158。”海洋钻探计划论文集 158. 129-141 (1998)。