Carbonate sediments & natural organic matter

本研究项目探讨了碳酸盐岩沉积物的成岩作用，既与生活在沉积物表面附近的生物有关，也与在其降解过程中渗出到间隙环境中的无生命的自然有机质有关。主要重点是监测腐殖质化的自然过程及其如何影响，例如有机胶体和自生碳酸钙的形成。腐殖化作用，仅次于光合作用，是地球上有机碳最重要的转移机制之一。一般来说，它包括将不稳定的生物大分子转化为在地球表面条件下稳定的地质大分子。因此，如果某些条件适用，这种低分子量腐殖质化合物甚至可以在地质上成熟的沉积岩中检测到，这些沉积岩有数亿年的历史。最近对现代和古代沉积物的分析表明，显生宙的细粒碳酸盐丘是相对新鲜的地聚合物的主要汇。腐殖化作用与矿物自生作用相结合，不仅为这些石灰石的增生机制提供了解释，还解释了其他地质特征，如它们的荧光或洞穴系统的早期开放。从短期来看，该项目打算通过探索大巴哈马海岸海绵生物礁下的早期成岩作用来证实我们的方法。预期的现象（海绵组织的钙化、缩聚、蛋白石针状物的溶解、文石的再结晶）应该作为古代富含海绵的碳酸盐丘的范例。这样的土丘在过去的地质时期更为常见，它们逐渐形成了大型结构。古代土丘的突出例子发生在摩洛哥阿特拉斯山脉的侏罗纪。然而，这里的研究兴趣有更大的范围，因为它还考虑了从大灭绝中恢复，它对沉积几何形状的影响以及深埋环境中天然有机质的动员。这些问题对油气藏的地下预测和勘探策略具有重要意义。

This research project explores the diagenesis of carbonate sediments in relation to both organisms that live near to the sediment surface and the non-living, natural organic matter that exudates into the interstitial environment during their degradation. The primary focus is to monitor the natural process of humification and how it influences, e.g., the formation of organic colloids and authigenic Ca-carbonates. Humification, next to photosynthesis, represents one of the most important transfer mechanisms of organic carbon on Earth. In general, it comprises the transformation of labile, biological macromolecules into geological macromolecules that are stable under the conditions of the Earth's surface. By consequence, and if certain conditions apply, such low-molecular weight humic compounds should be detectable even in geologically mature sedimentary rocks, hundreds of million of years in age. Recent insights from the analysis of modern and ancient sediments indicate that Phanerozoic, fine-grained carbonate mounds acted as a major sink of relatively fresh geopolymers. Humification, in concert with mineral authigenesis, not only offers an explanation for the accretion mechanism of these limestones, it also explains other geological features such as their fluorescence or the early opening of a cavity system. In the short term perspective, this project intends to substantiate our approach by exploring early diagenesis below the sponge bioherms of the Great Bahama Bank. The expected phenomena (calcification of sponge tissue, polycondensation, dissolution of opaline spicules, recrystallisation of aragonite) should serve as a paradigm for the ancient sponge-rich carbonate mounds. Such mounds were much more common in the geological past where they built up to form large structures. Prominent examples of ancient mounds, which I explore for comparison, occur in the Jurassic of the Atlas mountains in Morocco. However, the research interest there has a larger scope in that it also considers recovery from mass extinction, its impact on depositional geometries and the mobilisation of natural organic matter in the deep-burial environment. These issues are important for subsurface prognosis and exploration strategies for hydrocarbon reservoirs.