Collaborative Research: Rates of Carbonate Formation in the Samail Ophiolite, Oman: Implications of Ultramafic Weathering for the Carbon Cycle

合作研究：阿曼萨迈伊蛇绿岩中碳酸盐的形成速率：超镁铁质风化对碳循环的影响

• 批准号: 1049950
• 负责人: Kenneth Sims
• 金额: $ 2.96万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1049950&HistoricalAwards=false
• 关键词: Collaborative; Research; Rates; Carbonate; Formation

In the last few years, considerable attention has been focused on carbon capture and storage to mitigate anthropogenic input of atmospheric CO2. One proposed option for mitigation is to increase conversion of CO2 gas to stable, solid carbonate minerals during chemical weathering of tectonically exposed mantle rock (or peridotite). While natural carbonation of peridotite is commonly observed, its rate, and therefore the rate of CO2 uptake via this weathering mechanism, is poorly known. Determining the natural rate of peridotite carbonation is critical for understanding the influence of this potentially important ?sink? in the global carbon cycle. The natural peridotite carbonation rate is also an essential, but poorly constrained, parameter in calculations evaluating the viability of using artificially-enhanced, in situ alteration of peridotite to mitigate the buildup of anthropogenic input to atmospheric CO2.The primary objective of this research is to determine natural carbonation rates of exposed mantle peridotites. The Samail Ophiolite, Oman, is one of the largest and best-exposed ophiolites in the world, and hence is an ideal natural laboratory for investigating natural carbon storage in mantle peridotites. The research team has selected and carefully mapped eight sites that include roadcuts exposing carbonate veins, travertine deposits, and one site located on the natural peridotite weathering surface and containing abundant carbonate veins. The work plan consists of determining the ages of carbonates using two independent radiogenic dating techniques: 14C (for carbonates as old as ~50,000 years) and 238U-230Th (for carbonates as old as ~350,000 years). In addition, they will determine exposure ages for the host mantle peridotite to test the hypothesis that carbonate weathering primarily occurs in a thin weathering horizon that keeps pace with erosion rates. This project constitutes the Ph.D. thesis research for MIT/WHOI Joint Program student Evelyn Mervine. An improved understanding of natural carbonate formation in ultramafic rocks will aid efforts to develop CO2 capture and storage in ultramafic rocks to offset anthropogenic CO2 emissions and mitigate global climate change.

在过去几年中，人们对碳捕获和封存给予了相当多的关注，以减少大气二氧化碳的人为输入。提出的一种缓解方案是在构造暴露的地幔岩（或橄榄岩）的化学风化过程中增加二氧化碳气体向稳定的固体碳酸盐矿物的转化。虽然橄榄岩的自然碳化作用很常见，但其速率以及通过这种风化机制吸收二氧化碳的速率却鲜为人知。确定橄榄岩碳化的自然速率对于理解这一潜在重要“下沉”的影响至关重要。在全球碳循环中。在评估使用人工增强的橄榄岩原位蚀变来减轻人为输入到大气二氧化碳的累积的可行性的计算中，天然橄榄岩碳化率也是一个重要但约束较少的参数。这项研究的主要目的是确定暴露地幔橄榄岩的自然碳化速率。阿曼的萨梅尔蛇绿岩是世界上最大、暴露程度最好的蛇绿岩之一，因此是研究地幔橄榄岩天然碳储存的理想天然实验室。研究小组选择并仔细绘制了八个地点，其中包括暴露碳酸盐岩脉、钙华矿床的路堑，以及一个位于天然橄榄岩风化表面并含有丰富碳酸盐岩矿脉的地点。该工作计划包括使用两种独立的放射成因测年技术确定碳酸盐的年龄：14C（对于碳酸盐的年龄可达约 50,000 年）和 238U-230Th（对于碳酸盐的年龄可达约 350,000 年）。此外，他们还将确定主地幔橄榄岩的暴露年龄，以检验碳酸盐风化主要发生在与侵蚀速率保持同步的薄风化层中的假设。该项目构成了博士学位。麻省理工学院/WHOI 联合项目学生 Evelyn Mervine 的论文研究。加深对超镁铁质岩石中天然碳酸盐形成的了解将有助于开发超镁铁质岩石中二氧化碳的捕获和储存，以抵消人为二氧化碳排放并缓解全球气候变化。