The vast majority of carbonate minerals in modern marine sediments are biogenic, derived from the skeletal remains of organisms living in the ocean. However, carbonate minerals can also precipitate abiotically within marine sediments, and this carbonate mineral precipitation within sediments has been suggested as a third major, and isotopically distinct, sink in the global carbon cycle, particularly important earlier in Earth history. Here we present a global compilation of pore fluid data and compare the sulfate, calcium, phosphate and magnesium concentrations with pore fluid alkalinity to explore the emerging relationships and explore what drives carbonate mineral precipitation in sediments. Our data compilation shows that the gradient of pore fluid sulfate concentrations correlates strongly with the gradient of alkalinity as well as with the gradient of calcium, and that these correlations improve dramatically in sediments where methane is present. We also note that sedimentary pore fluids that are high in phosphate concentration are also high in alkalinity, which may indicate suppression of carbonate mineral precipitation in the presence of sedimentary phosphate. Our data can be used to highlight sediments where both dolomite formation and dolomitization of previously deposited calcium carbonate minerals is occurring. We explore how carbonate mineral saturation state changes as a function of calcium concentrations, alkalinity, and pH, and suggest a reason why calcium concentrations are never fully depleted in sedimentary pore fluids. We conclude that carbonate minerals precipitate in sediments with methane, where the anaerobic oxidation of this methane helps promote particularly high saturation states for carbonate minerals.

现代海洋沉积物中的绝大多数碳酸盐矿物是生物成因的，它们来自生活在海洋中的生物的骨骼遗骸。但是，碳酸盐矿物也可以在海洋沉积物中非生物地沉淀，并且已提出这种沉积物中的碳酸盐矿物沉淀是全球碳循环中的第三种主要且同位素不同的下沉，在地球历史的早期尤为重要。在这里，我们提供了孔隙流体数据的全球汇总，并将硫酸盐，钙，磷酸盐和镁的浓度与孔隙流体的碱度进行了比较，以探讨新出现的关系并探讨驱动沉积物中碳酸盐矿物沉淀的因素。我们的数据汇编显示，孔隙流体硫酸盐浓度的梯度与碱度梯度以及钙的梯度密切相关，并且这些相关性在存在甲烷的沉积物中显着改善。我们还注意到，磷酸盐浓度高的沉积孔隙流体的碱度也高，这可能表明在沉积磷酸盐的存在下碳酸盐矿物沉淀的抑制作用。我们的数据可用于突出显示先前沉积的碳酸钙矿物同时发生白云石形成和白云石化的沉积物。我们探讨了碳酸盐矿物的饱和状态如何随钙浓度，碱度和pH的变化而变化，并提出了沉积孔隙液中钙浓度从未完全耗尽的原因。我们得出的结论是，碳酸盐矿物与甲烷一起沉积在沉积物中，其中甲烷的厌氧氧化有助于促进碳酸盐矿物的特别高的饱和状态。