ThermoSill - Effects of local heating due to sill intrusion on subsurface sedimentary microbial activity

最近的IODP Exp.385(瓜伊马斯盆地构造与生物圈，9月至11月2019年)在瓜伊马斯盆地钻探了八个地点，瓜伊马斯盆地是加利福尼亚州海湾的一个年轻的边缘裂谷盆地，其特点是海底扩张活跃，沉积物沉积迅速，包括来自生物生产力高的上覆水域的富含有机的沉积物和来自附近大陆边缘的陆源沉积物。考察队以富含有机物质的沉积序列为岩心，并侵入了岩床。微生物学是此次考察的重点研究课题之一。为量化硫酸盐还原速率收集了一个大样本集，这是海洋沉积物中定量上最重要的电子受体过程，目前在GFZ。拟议的ThermoSill项目最初将侧重于这些岩心中微生物硫酸盐还原的一般特征以及压力和温度的影响。钻探岩心经历了非常不同的地温梯度，从大约200到800摄氏度公里-1不等，船上的地球化学数据已经表明正在发生各种生物地球化学过程。在深海沉积物中，特别是那些埋藏在很深的地方，因此温度很高的沉积物中，像短链有机酸这样的有机底物通常是一个限制因素。由于瓜伊马斯盆地沉积物受水热作用的影响，大分子沉积有机质的热裂解提供了丰富的微生物底物。ThermoSill将研究这种丰富的底物是否会导致特定底物的优先降解，从而揭示在生命上限温度下的过程。将特别注意甲烷的厌氧氧化。在项目的最后部分，将通过加热实验来模拟窗台的就位和伴随的温升。这些实验将伴随着热解实验和动力学模型，以测试这种短期加热是否会对地质时间尺度上的微生物群落产生影响。拟议的项目与探险队的目标直接相关。它也是对正在进行的一个项目的补充，该项目研究了压力和温度对南开海槽非水热影响沉积物中微生物硫酸盐还原的影响。实验370)。

The recent IODP Exp. 385 (Guaymas Basin Tectonics and Biosphere, Sept.-Nov. 2019) drilled eight sites in Guaymas Basin, a young marginal rift basin in the Gulf of California, characterized by active seafloor spreading and rapid sediment deposition, including organic-rich sediments derived from biologically highly productive overlying waters and terrigenous sediments from nearby continental margins. The expedition cored sequences of organic-rich sediments with sill intrusions. Microbiology was one of the key research topics of this expedition. A large sample set for quantification of sulfate reduction rates, the quantitatively most important electron acceptor process in marine sediments, was collected and is now at GFZ. The proposed ThermoSill project will initially focus on the general characteristics of microbial sulfate reduction in these cores as well as the effects of pressure and temperature. The drill cores have experienced vastly different geothermal gradients, ranging from ca. 200 to over 800 °C km-1, and the on-board geochemical data already indicate a great diversity of biogeochemical processes taking place. In deep sea sediments, especially those buried to great depth and therefore temperature, organic substrates like short-chain organic acids are a generally a limiting factor. Because the sediments in Guaymas Basin are hydrothermally influenced, thermogenic cracking of macromolecular sedimentary organic matter provides abundant microbial substrates. ThermoSill will investigate whether this abundance of substrate has an effect leads to a preferential degradation of specific substrates and therefore shed light onto processes at the upper temperature limit of life. Particular attention will be paid to anaerobic oxidation of methane. In the final part of the project, the emplacement of sills and concomitant temperature increase will be simulated by heating experiments. These experiments will be accompanied by pyrolysis experiments and kinetic modelling to test whether such short-time heating can have an effect on the microbial community over geologic timescales. The proposed project is directly relevant to the objectives of the expedition. It is also complementary to an ongoing project that studies the effects of pressure and temperature on microbial sulfate reduction in non-hydrothermally influenced sediments from Nankai Trough (IODP. Exp. 370).