Magnesium Isotope Geochemistry of Carbonate Sediments

提供资金，通过测量整个新生代的远洋碳酸盐的#948; 26 Mg来重建海水的#948; 26 Mg。PI的初步结果显示，在太平洋和大西洋的站点中，#948; 26 Mg的模式相似。然而，一些观察到的#948; 26 Mg的变化太快，太大，与目前对地球化学镁循环的理解不一致。为了更好地了解远洋碳酸盐中镁同位素的变化，PI还将对个别物种的浮游有孔虫和散装碳酸盐沉积物以及孔隙流体的其他尺寸部分进行镁同位素测量。这些测量结果将为成岩作用的潜在影响提供重要的新约束。PI还将寻求替代方法，利用蒸发岩矿物中的流体包裹体重建海水中的#948; 26 Mg。这项工作将有助于阐明控制海水主要元素化学的过程，从而在地质时间尺度上控制全球碳循环和气候。这项研究有可能对我们对海洋化学的理解产生广泛的影响，特别是在镁，钙和碳的地球化学循环方面。此外，拟议的活动可能有助于阐明更好地了解新生代气候变化的原因，更好地了解在这一时间尺度上影响碳循环的制约因素。这项研究将支持研究生的培训，他们将接触到一系列方法，包括质谱和数值建模。

Funds are provided to reconstruct the δ26Mg of seawater by measuring it the δ26Mg of pelagic carbonates across the Cenozoic. PI's preliminary results show similar patterns in δ26Mg at sites in both the Pacific and Atlantic Ocean sites. However, some of the observed changes in δ26Mg are too fast and too large to be compatible with the current understanding of the geochemical magnesium cycle. To refine understanding of magnesium isotope variability in pelagic carbonates the PI will also make magnesium isotope measurements on individual species of planktonic foraminifera and other size fractions of the bulk carbonate sediment as well as in pore fluids. These measurements will provide important new constraints on the potential effects of diagenesis. The PI will also pursue alternative approaches to reconstructing the δ26Mg of seawater using fluid inclusions in evaporite minerals. The work will help elucidate the processes that control the major element chemistry of seawater, and therefore the global carbon cycle and climate, on geologic timescales. The research has the potential to make a broad impact on our understanding of the chemistry of the ocean, particularly with respect to the geochemical cycles of magnesium, calcium, and carbon. In addition, the proposed activities may help elucidate a better understanding of the causes of climate change over the Cenozoic by better constraining factors that affect the carbon cycle over this timescale. The research will support the training of a graduate student who will be exposed to a range of approaches including mass spectrometry and numerical modeling.