IODP Phase 1 post cruise support for C Smith-Duque Expedition 344

IODP 第 1 阶段为 C Smith-Duque Expedition 344 提供巡航后支持

• 批准号: NE/L014351/1
• 负责人: Damon Teagle
• 金额: $ 4.42万
• 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: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FL014351%2F1
• 关键词: IODP; Phase; post; cruise; support

The subduction of tectonic plates is one of the fundamental processes of plate tectonics, and the most potent source of earthquakes near the Earth's surface. The process occurs at convergent boundaries where one tectonic plate moves under another tectonic plate by sinking into the Earth's mantle. Despite the wealth of research that has been dedicated to understanding the role of subduction in earthquake generation (seismogenesis) direct sampling of the seismogenic region of subduction zones has been beyond the reach of direct sampling and observation.I sailed as part of an international team of scientists on Integrated Ocean Drilling Program (IODP) Expedition 344 to recover seafloor sediments and underlying volcanic rocks that make up the subducting oceanic plate (Cocos-Nazca) and the upper plate (Caribbean) of the Costa Rica Arc. Expedition 344 made important progress in determining the geological nature of subducting sediments and basement, the rate of subduction of the Cocos plate into the Costa Rican margin, the nature of fluid-rock interactions within the Costa Rican margin, and how the forces acting on the subduction system change as the subduction system enters the seismogenic zone. At one site, volcanic rock beneath sediment was sampled. The volcanic rocks recovered during Expedition 344 originally formed during the eruption of sub-sea volcanoes along mid-ocean ridges, but have since cooled, moved by ocean spreading, and are now entering the Costa Rican subduction zone.Throughout the lifetime of oceanic crust, thermally driven seawater/rock interaction known as hydrothermal alteration, results in exchange of elements and compounds to form new minerals within voids and veins, or locally replacing the original minerals in the rocks. Fluids that form these minerals are sourced from seawater that has interacted with oceanic crust at a low temperature. As oceanic crust subducts, temperatures and pressures increase such that water previously bound in secondary minerals migrates upwards and that it may contribute the hydrothermal activity at or near subduction zones. Our research, based on secondary mineral calcium carbonate will be used to determine if subduction-related fluids have influenced the hydrothermal system of imminently subducting basement.The element Strontium (Sr), present in calcium carbonate, is extremely useful since its isotopic composition in seawater through time is well known. We will use the Sr-isotopic composition in calcium carbonate to estimate how much seawater has mixed with mid-ocean ridge basalt, which in turn has a very different but well defined isotopic ratio. In addition we will use Sr isotopes to partially constrain the timing of calcium carbonate formation.Temperature is known to control the preference of Oxygen (O) isotopes uptake during calcium carbonate formation. We will therefore use O-isotopes in carbonates to determine the temperature of formation to estimate the thermal environment of formation. Knowing the temperature will provide insight into whether some or all of the fluids have come from subduction settings. We will see if later episodes of veining (as the crust moves towards the subduction zone) increase in temperature. This will indicate that subduction processes are influencing incoming ocean crust.Trace elements from fluids are incorporated in to calcium carbonate during its formation, therefore we can measure the concentrations of these elements to estimate the composition of the fluid. Trace element compositions will then be compared against seawater compositions and pore-fluid compositions from other subduction zone settings to estimate where fluids may have come from. Our research will offer new insight into the nature of alteration within imminently subducting ocean crust, and therefore will contribute to our understanding of the composition and physical properties of material that enters subduction zones.

构造板的俯冲是板块构造的基本过程之一，也是地球表面附近最有效的地震来源。该过程发生在收敛边界，其中一个构造板通过沉入地球的地幔下方移动在另一个构造板下。尽管有大量的研究致力于了解俯冲发电中的俯冲作用（地震生成）对俯冲带的地震生成区的直接取样已经超出了直接取样和观察的范围，但我作为一支在综合海洋训练计划（IODP）降落的境内的国际科学家团队的一部分，以使海洋降落344的繁殖量为seply seplistic seplan voldan voldan volds volling volds volling volling voldan voldan volds volds voll volds volds volds volds wolds volds wolds volds wolds wolds。哥斯达黎加弧的板（可可纳粹）和上板（加勒比海）。 Expedition 344在确定俯冲沉积物和地下室的地质性质，Cocos板的俯冲速率，进入哥斯达黎加边缘的俯冲速率，哥斯达黎加边缘内的流体摇滚相互作用的性质以及对俯冲系统对俯冲系统的作用在俯冲系统中如何变化，探险344取得了重要进展。在一个地点，采样了沉积物下面的火山岩。在探险344期间恢复的火山岩最初是在海洋中部山脊沿着海洋火山喷发中形成的空隙和静脉，或者在当地取代岩石中的原始矿物质。形成这些矿物质的流体来自在低温下与海洋壳相互作用的海水。随着海洋外壳俯冲，温度和压力的增加，以前在二级矿物质中结合的水会向上迁移，并且可能在俯冲带或接近俯冲带或接近俯冲带的水热活动中迁移。我们的研究基于碳酸盐钙将用于确定俯冲相关的液体是否影响了迫在眉睫的俯冲基质的水热系统。碳酸钙中存在的元素延纹（SR）非常有用，因为它的同位素组成在海洋中的同位素组成是非常有用的。我们将在碳酸钙中使用SR-同位素组合物来估计多少海水与中海脊玄武岩混合在一起，这又具有非常不同但定义明确的同位素比。此外，我们将使用SR同位素部分约束碳酸钙形成的时机。已知植物可以控制氧气（O）同位素摄取在碳酸钙形成过程中的偏好。因此，我们将在碳酸盐中使用O-同位素来确定形成温度以估计形成的热环境。知道温度将提供有关某些或全部流体是否来自俯冲设置的洞察力。我们将看到后来的静脉发作（随着外壳向俯冲带移动）是否会增加温度。这将表明俯冲过程正在影响传入的海壳。在形成过程中，将流体的跟踪元素纳入到碳酸钙中，因此我们可以测量这些元素的浓度以估计流体的组成。然后将将痕量元素组成与其他俯冲区设置的海水组成和孔流体组成进行比较，以估算流体可能来自何处。我们的研究将提供有关即将俯冲的海壳中改变性质的新见解，因此将有助于我们理解进入俯冲区的材料的组成和物理特性。