UK-IODP Moratorium Co-Chief Support for Expedition 393: Quantifying the geochemical impacts of ocean crustal ageing.

UK-IODP 暂停第 393 次探险联合首席支持：量化海洋地壳老化的地球化学影响。

• 批准号: NE/X009440/1
• 负责人: Damon Teagle
• 金额: $ 11.49万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX009440%2F1
• 关键词: UK; IODP; Moratorium; Co; Chief

The mid-ocean ridges are a range of submarine ridge that spiral around Earth like the seams on a baseball. This is where new ocean crust is constructed from magma formed from the partial melting of the upper mantle that then upwells to be intruded into and erupted onto the ocean floor. More that 3 square kilometres of ocean crust are formed each year. On average the ocean crust is approximately 6.5 +/- 1 km thick, and consequently more than 20 cubic kilometres of magma moves from the mantle to make new crust every year, making this process the dominant mechanism for heat and mass transfer from the interior of the Earth to the surface of our planet. Geophysical surveys demonstrate that the ocean crust is completely solidified within a kilometre or so of the spreading ridge. The cooling and crystallisation of these magmas is facilitated by the circulation of seawater-derived "black-smoker" hydrothermal fluids (upto 400 degrees C) that vent on the seafloor at spectacular black smoker chimneys, form volcanic-hosted massive sulphide base metal deposits (Cu, Zn), and provide energy and environments for diverse communities of exotic chemosynthetic organisms and microbes. As the ocean crust spreads away from the ridge axis further reactions with seawater-derived fluids occur on the vast ridge flanks that cover more than 60 percent of the surface of our planet. This circulation is driven by the cooling of the new plate-the lithosphere-as it matures away from the ridge. Seafloor measurements indicate that compared to models on average there is a discernible conductive heat flow deficit out to crust of ~65 million years, indicating the advection of heat by the circulation of hydrothermal fluids. However, in contrast to the high temperature systems at the ridge axis, hydrothermal circulation on the ridge flanks occurs at low temperatures generally much less than 100 degrees and generally at only a few tens of degrees or lower. This leads to the alteration of volcanic rocks and the precipitation of secondary minerals such as clays, iron oxides, carbonates, sulphides and zeolites. Because of their vast scale, these ridge flank reactions involve huge volumes of seawater-derived hydrothermal fluids and are important components in the global geochemical budgets of important elements and compounds such as U, K, CO2, H2O, S, Mg, Ca and Fe3+/Fetotal (oxidation). Most of these reactions occur in the volcanic lava flows of the uppermost crust. Integrated Ocean Discovery Program (IODP) Expedition 390/393 are the first experiment to systematically quantify the evolving styles and extents of seawater-basalt hydrothermal exchange across the flank of a mid-ocean ridge. Importantly it will drill sites with normal thickness sediment cover in contrast to earlier ocean drilling that has tended to sample sites with anomalously thick sediment cover. It will drill through the sedimentary overburden and sample 200 to 300 metres of the lava sequences in ocean crust of 6.6, 15.2, 30.6, 49.2 and 61.2 million years old on the western flank of the slow to medium spreading rate Mid-Atlantic Ridge across an east-west transect at approximately 30 deg South. At the oldest 61.2 million-year-old crust IODP Expedition 390/393 will drill two sites - one with only a thin sediment cover (<300 m) to contrast and compare with ocean crust of the same age that has been buried by a much thicker sediment cover (~600 m).Careful quantitative core description, mineral identification and geochemical analyses of fresh, little altered ocean basalt and representative samples of more strongly altered rocks and minerals from lava flows, breccias and veins will enable us to understand the evolving styles of hydrothermal fluid-rock reactions and quantify the progressive extents of chemical exchange between seawater and the ocean crust. These analyses will also reveal information about changes in the composition of ocean bottom waters over the past 60 million years.

海洋中部山脊是一系列海底脊，像棒球上的接缝一样在地球上旋转。这是由岩浆由上地幔的部分熔化形成的岩浆建造的，然后将上下入狱并爆发到海底。每年形成3平方公里的海壳。平均而言，海角约为6.5 +/- 1 km厚，因此，岩浆从地幔从地幔移动了20立方公里，每年都会制造新的地壳，使该过程成为从地球内部到我们星球表面的热和质量转移的主要机制。地球物理调查表明，在扩散山脊的一公里左右的情况下，海角完全固化。这些岩浆的冷却和结晶促进了海水衍生的“黑人烟”水热液（最高400度c），在海底上以壮观的黑色吸烟烟囱在海底上排放，形成火山供应的巨大的硫化物基金会（CU，Zn），并提供各种环境，并提供动态的环境，并提供动态的环境，并提供动态的环境和环境。和微生物。随着海角从山脊轴蔓延开来，与海水衍生的液体发生了进一步的反应，发生在广阔的山脊侧面，覆盖了我们星球表面的60％以上。这种循环是由新板的冷却驱动的 - 岩石圈 - 它使其从山脊上移开。海底测量结果表明，与平均模型相比，有可分离的导电热量缺乏至6500万年的外壳，这表明通过热液流体的循环循环进行热量。但是，与山脊轴的高温系统相反，脊侧面的热液循环通常在低温下发生通常小于100度，通常仅在几十几个或更低的地方。这导致火山岩的改变以及粘土，氧化铁，碳酸盐，硫化物和沸石等次要矿物的降水。由于它们的规模巨大，这些山脊侧面反应涉及大量海水衍生的水热流体，并且是重要元素的全球地球化学预算中的重要组成部分，例如U，U，K，CO2，H2O，H2O，S，MG，Ca，Ca，Ca和Fe3+/repotal（氧化）。这些反应大部分发生在上皮的火山熔岩流中。综合海洋发现计划（IODP）探险390/393是系统地量化海水 - 巴萨尔特水热交换的不断发展的样式和范围的第一个实验，跨过远洋山脊的侧面。重要的是，与早期的海洋钻井相比，它将钻孔厚度正常的厚度沉积物盖，而较早的海洋钻孔倾向于采样异常厚的沉积物盖。它将钻探沉积覆盖层，并在海壳中采样200至300米的熔岩序列，为6.6、15.2、30.6、49.2、49.2和6120万年，在大约30度的East-Westect横文中，较慢的中大西洋山脊的慢速扩散速率的西部侧面延伸。在最古老的6120万年历史的IODP探险390/393上，将钻一个两个地点 - 一个站点 - 一个薄薄的沉积物盖（<300 m），与相同年龄的海壳形成对比，并与更厚的沉积物所埋葬的相同年龄（约600 m）埋葬（〜600 m）的层次。从熔岩流，角砾岩和静脉中改变的岩石和矿物质将使我们能够理解水热液反应的不断发展的风格，并量化海水和海水中的化学交换的渐进性。这些分析还将揭示有关过去6000万年来海洋底部水域组成变化的信息。

项目成果

South Atlantic Transect

南大西洋横断面

• 发表时间: 2024
• 期刊: Proceedings of the International Ocean Discovery Program Expedition reports
• 作者: Coggon, R.M.;Teagle, D.A.H.;Sylvan, J.B.;Reece, J.;Estes, E.R.;Williams, T.J.;Christeson, G.L.
• 通讯作者: Christeson, G.L.

Expedition 390 Preliminary Report: South Atlantic Transect 1

• DOI: 10.14379/iodp.pr.390.2022
• 发表时间: 2022-10
• 期刊: International Ocean Discovery Program Preliminary Report
• 作者: R. Coggon;J. Sylvan;D. Teagle;J. Reece;G. Christeson;E. Estes;T. Williams