现代高温热泉硅质叠层石成因及纹层变化机理研究

As typical organosedimentary deposits produced by the mediation of growth and activity of microorganisms, stromatolites in modern high temperature hot springs contain important environmental and biological information, and provide unique opportunities for understanding the genesis of these modern and ancient stromatolites. Using multidisciplinary methods, together with in-situ growth experiment of siliceous stromatolite, the aim of this study is to (1)obtain the growth speed of siliceous stromatolite and the cycle of laminations, (2)identify the major factors which potentially control cyclic laminations,(3) discuss the microbial roles in constructing siliceous stromatolites and (4) understand the silicification of hyperthermophilic bacteria, in a high temperature (T>90℃) hot spring in Rehai Geothermal Field, Tengchong, Yunan. Critically,this study will elucidate the genesis of the siliceous stromatolites and recognize the biotic and abiotic processes which could influence the formation of siliceous stromatolites from various aspects including growth, structure, biological affect and environmental driving force. The results from this study are expected to provide a novel insight into the formation of modern and ancient stromatolites, the biogeochemical process of silica in high temperature hot springs, as well as the co-evolution of microbes and extreme environment.

作为典型的生物沉积地质体，现代高温热泉叠层石中蕴含着重要的地质环境和生物信息，为研究叠层石的形成机理提供了极好的对象。本项研究以云南腾冲热海高温（T>90℃）热泉环境中正在生长的硅质叠层石为研究对象，采用矿物学、地球化学和微生物学等多学科交叉研究方法，结合硅质叠层石的热泉原位生长实验，确定硅质叠层石的生长速率和纹层变化周期，识别控制硅质叠层石纹层周期性变化的主要因素，探讨超嗜热微生物在硅质叠层石生长中的作用和硅化机制，从叠层石的生长、结构、生物影响和环境驱动力等几方面研究高温硅质叠层石的形成机制，认识影响高温硅质叠层石形成的关键生物和非生物过程。此项研究对于深入理解现代和古代硅质叠层石的形成机理、高温环境中硅的生物地球化学过程、以及微生物与极端环境的协同演化关系具有十分重要的意义。

本项目研究了云南腾冲热海高温（T>90℃）热泉环境中正在生长的硅质（无定形硅）叠层石，结合硅质叠层石的热泉原位生长实验，确定硅质叠层石的生长速率和纹层变化周期（池中蛋白石的沉淀速率为0.5-0.75mm/月，PVC管中蛋白石的沉淀速率在2.5-3.5mm/月之间），提出气候周期性变化（如降水量等）是造成低孔隙度层和高孔隙度纹层形成的主要原因，认识高温热泉体系中微生物的快速硅化过程及生物信号的消失过程，发现以除硫球菌目古菌、热变形菌目古菌和产水菌门细菌为主的微生物是这一硅质叠层石的主要建造者。该研究成果对于深入理解高温环境中微生物硅化过程、高温叠层石的成因机制及环境指示意义具有重要的意义。