The timing and nature of inorganic calcium carbonate precipitation within exposed basalt from the South Pacific Gyre, IODP Expedition 329.

南太平洋环流暴露的玄武岩中无机碳酸钙沉淀的时间和性质，IODP 第 329 次探险。

• 批准号: NE/L000024/1
• 负责人: Damon Teagle
• 金额: $ 4.51万
• 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: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FL000024%2F1
• 关键词: timing; nature; inorganic; calcium; carbonate

IODP Expedition 329 sailed a transect of over 11,000 km of ocean over a period of 66 days from Papeete, Tahiti to Auckland, New Zealand to recover sediment and basalt drillcores from within the South Pacific Gyre (SPG), the world's largest ocean current system. and one of the most poorly explored regions of Earth. Indeed the last scientific expedition which recovered samples from the seafloor within the SPG was over 130 years ago during the HMS Challenger Expedition (1872-1876). During IODP Expedition 329 we made great strides in addressing what, if any, microbial life occurs beneath the sea floor within the gyre and in what conditions (habitats) life occurs. We also explored the role the oceans, seafloor sediment, and underlying ocean crust plays in controlling habitats beneath the seafloor across a transect of the SPG.At three sites we took samples of the volcanic basement rocks beneath the sediment. The volcanic rocks, initially formed from eruptions of sub-sea volcanoes along mid ocean ridges (mid ocean ridge basalt) have since cooled and spread from the mid ocean ridge over millions of years to their present location.Chemical interaction with seawater that enters the ocean crust through fractures and joints (caused by post eruption cooling and tectonic movement) results in the formation of secondary minerals that fill fracture space and sometimes replaces the original volcanic rock. This 'seafloor weathering' process results in chemical transfer between seawater and volcanic rocks, altering the composition of ingressing seawater and the volcanic crust. Our research, based on the low temperature (<100 deg C) secondary mineral calcium carbonate will address some of the uncertainties associated with this process and in turn will answer some important questions regarding basement habitability and global geochemical cycles.The element Strontium (Sr), which is present in calcium carbonate, is extremely useful since its isotopic composition in seawater varies through time and this record 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 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. Since isotopes of Uranium (U) decay radioactively into stable isotopic 'daughters' of Lead (Pb) at a known rate, it is possible, given the right geological conditions and appropriate methods, to date the formation of mineral phases. U and Pb incorporated into calcium carbonate will provide insights into the timing of seafloor weathering processes in oceanic crust. We will utilize measurements of U and Pb isotopes to date calcium carbonate formation within the South Pacific Gyre.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 determine the thermal environment of formation. Knowledge of temperature will allows us to place limits on the extent of the sub seafloor biosphere. Impurities of Magnesium (Mg) and Sr that variably replace (substitute) for calcium (Ca) in the crystal structure of calcite can be measured to infer past Mg/Ca and Sr/Ca ratios of ancient seawater for upto 120 Myrs of geological time. These ratios act as proxies for ancient seawater chemistry, which in turn provide insights into geochemical processes that take place between the Earth's crust, the oceans, and the atmosphere. Our research will offer tantalizing clues into the potential habitat for microbial life within oceanic crust, offer insights into the timing of seafloor weathering processes within the SPG.

IODP Expedition 329在66天内从大溪地的Papeete到新西兰的奥克兰，从南太平洋Gyre（SPG）内恢复了Sediment和Basalt Driltercores，在66天内航行了超过11,000公里的海洋。这是探索地球地区最糟糕的地区之一。确实，在SPG内的海底回收样本的最后一次科学探险是130年前的HMS Challenger探险（1872-1876）。在IODP Expedition 329期间，我们在解决Gyre内的海底以及在什么情况下（栖息地）生命的情况下，微生物生命发生了什么。我们还探索了海洋，海底沉积物和底层海皮的作用，在控制海底下方的栖息地穿过SPG的横断面。最初是由海脊中海山山脉（海脊中部）爆发形成的火山岩自那以后冷却并从中海山脊上散布了数百万年的海洋山脊到当前的位置。与海水与海水的化学互动，通过裂缝和关节的裂缝和污染后的裂缝和污染物造成的序列造成了次要的造成的序列，这是次要散发的动作，以至于造成了次要的流动，这是在次数上造成的。原始的火山岩。这种“海底风化”过程导致海水和火山岩之间的化学转移，改变了进入海水和火山壳的组成。我们的研究基于低温（<100 dEG）碳酸盐钙将解决与此过程相关的一些不确定性，进而将回答有关地下室可居住性和全球地球化学周期的一些重要问题。元素腹（SR）（碳酸盐）中存在于碳酸钙中，这是非常有用的，因为它的同位素组合非常有用，因为其在海水中均已在海水中广为人知。我们将在碳酸钙中使用SR-同位素组合物来估计海水与中海脊玄武岩混合了多少，该玄武岩的同位素比非常不同，但定义明确。此外，我们将使用SR同位素部分约束碳酸钙形成的时间。由于铀（U）的同位素以已知速率放射性地衰减成稳定的同位素“女儿”，因此，鉴于正确的地质条件和适当的方法，迄今为止，有可能迄今为止矿物相的形成。碳酸钙中掺入的U和PB将为海底风化过程的时机提供洞察力。我们将利用U和Pb同位素的测量值迄今在南太平洋陀螺仪内部的碳酸钙形成。植物植物可以控制氧气（O）同位素在碳酸钙形成过程中摄取的偏好。因此，我们将在碳酸盐中使用O-同位素来确定地层温度以确定形成的热环境。温度的知识将使我们能够对海底生物圈的范围进行限制。可以测量有方解石晶体结构的镁（Mg）和SR的杂质（Mg）和SR的杂质，可以测量有方解石结构的钙（CA），以推断过去的Mg/Ca和SR/CA比古代海水的比率为120 MYRS的地质时间。这些比率是古代海水化学反应的代理，这反过来又提供了对地球，海洋，海洋和大气之间发生的地球化学过程的见解。我们的研究将为海洋壳中微生物生命的潜在栖息地提供诱人的线索，为SPG内海底风化过程的时机提供见解。

项目成果

Presence of oxygen and aerobic communities from sea floor to basement in deep-sea sediments

• DOI: 10.1038/ngeo2387
• 发表时间: 2015-04-01
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: D'Hondt, Steven;Inagaki, Fumio;Ziebis, Wiebke
• 通讯作者: Ziebis, Wiebke

Seafloor basalt alteration and chemical change in the ultra thinly sedimented South Pacific

南太平洋超薄沉积海底玄武岩蚀变和化学变化

• DOI: 10.1002/2013gc005141
• 发表时间: 2014-07
• 期刊: Geochemistry Geophysics Geosystems
• 影响因子: 3.5
• 作者: Guo-Liang Zhang;Christopher, Smith_Duque
• 通讯作者: Christopher, Smith_Duque