Carbonate sediments & natural organic matter

碳酸盐沉积物

• 批准号: 312463-2008
• 负责人: Neuweiler, Fritz
• 金额: $ 2.26万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2010
• 资助国家: 加拿大
• 起止时间: 2010-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=457436
• 关键词: Carbonate; sediments; natural; organic; matter

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.

该研究项目探讨了碳酸盐沉积物的成岩作用，与生活在沉积物表面附近的生物体和在降解过程中渗出到间隙环境中的无生命的天然有机物有关。主要重点是监测腐殖化的自然过程及其影响，例如有机胶体和自生碳酸钙的形成。腐殖化是仅次于光合作用的代表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，即使在地质成熟、年龄为数亿年的沉积岩中，也应该可以检测到这种低分子量腐殖质化合物。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土丘是相对新鲜的地质聚合物的主要汇。腐殖化作用与矿物自生作用相结合，不仅解释了这些石灰岩的增生机制，还解释了其他地质特征，例如它们的荧光或空腔系统的早期打开。从短期来看，该项目旨在通过探索大巴哈马浅滩海绵生物礁下方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、乳白针状体的溶解、文石的重结晶）应该作为古代富含海绵的碳酸盐丘的范例。这种土丘在地质历史中更为常见，它们堆积起来形成大型结构。我为了比较而探索的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，那里的研究兴趣范围更大，因为它还考虑了大规模灭绝的恢复、其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。这些问题对于油气藏的地下预测和勘探策略具有重要意义。