茂名盆地含丛粒藻烷之沉凝灰岩与油页岩的地球化学研究

Volcanic breccia, tuff, tuffaceous laminae and tuffaceous siltstone are recently discovered with several layers embedding in the oil shale formation in the Tertiary Maoming Basin. Especially, botryococcanes with extremely heavy δ13C values were found mainly occurring in the top of the oil shale formation, as well as in the red tuffaceous laminae also within the upper part of the oil shale formation. These implied that huge changes on the water body environment and algal ecosystem were brought by the volcanic activities. Typically, the great enhancement of the dissolved iron concentration in the water body brought by the descendent volcanic ashes would facilitate the bloom of some algae, which, on one hand, consumed a great quantity of dissolved CO2 in the water body leading to the death of the common algae; on the other hand, the B race of the botryococcus braunii with capability of utilizing the bicarbonate ions during its photosynthesis could be survived and bloomed. However, the unsustainable supply of the HCO3- ion would cause the demise of the oil shale deposits and thus the subduction of the lake basin. Therefore, the studies on organic and inorganic geochemistry for the key horizon of the tuffaceous layers could illustrate the elimination history of the lake basin; point out the start and the key controlling factor of the growth and prosperous bloom of the B. braunii, as well as its origin and mechanism with heavy stable carbon isotopic composition. Of course, according to the geochemical condition and biogeochemical mechanism illustrated by the vivid case study results, the answers for the above questions will help provide the scientific references and consults for the modern cultures, which could potentially improve and enhance the yields of the hydrocarbon generating algae. The study area and scope can be enlarged to the other terrestrial basins with oil shale occurrence, in order to comprehensively explore the influence of the volcanic activities on the lake basin.

茂名油页岩层中发育有火山角砾岩、凝灰岩层、沉凝灰岩夹层和凝灰质砂岩层；上部油页岩发育至少6层以上的凝灰岩层，具有重碳同位素组成的丛粒藻烷主要出现在油页岩顶部及其红色沉凝灰岩夹层中，指示火山活动使水体环境和藻类生态发生了变化：火山活动带来水体可溶性Fe的大量增高，促进了藻类勃发，消耗了水体中溶解的CO2使得一些藻类消亡，而利用碳酸氢根进行光合作用的丛粒藻B属勃发，后者不可持续最终使得油页岩消失。因此，关键层位凝灰岩夹层的有机、无机地球化学研究，可揭示藻类和油页岩演化消亡的历史；丛粒藻发育和繁盛的启动和主控因素；丛粒藻烷的重碳同位素成因。通过实例获得的地史时期丛粒藻繁盛的地球化学条件和生物地化机理，可为现代油藻培养的产量提高提供水体营养条件依据。研究范围可适当扩展至其它陆相油页岩盆地，通过对比和检验，为火山活动对油页岩盆地的影响提供实例、实证和科学依据

茂名油页岩中的丛粒藻烷单体碳同位素重达-6‰，富集层主要以红色沉凝灰岩夹层出现在油页岩顶部，指示火山活动使水体环境和藻类生态发生了变化。关键层位凝灰岩夹层的有机无机地球化学研究，可揭示藻类和油页岩演化消亡的历史，丛粒藻发育和繁盛的启动和主控因素，以及丛粒藻烷的重碳同位素成因。.虽然宏观尺度上的火山活动，无法从周边区域获得地质上的证据支持，但是中等尺度上的铁质层和微观尺度上的大量菱铁矿和赤铁矿褐铁矿等铁质矿物，以及扫描电镜纳米尺度下观察到的铁氧化菌，一系列不同尺度的证据皆表明铁可作为丛粒藻发育繁盛的主要营养元素，铁氧化菌与丛粒藻具有生态协同发育、共生/营养机制，成为丛粒藻繁盛勃发及油页岩发育的主控因素。.精细的有机地球化学研究，获得如下坚实的进展：①分离并在常规荧光显微镜下鉴定出丛粒藻化石，实现了杯口等微细结构观察；②首次报道了C39-lycopane的发现和鉴定，确认丛粒藻L种的生源贡献；③对30多年前文献中的两个C30-HBI化合物的碳数和结构都予以了修正；④发现并鉴定具有新颖的季碳β位甲基结构的C33-新丛粒藻烷酮，从而对30年前人鉴定的C33-丛粒藻烷的分子结构也进行了修正；⑤丛粒藻烯通常都是用三元环中间体理论来解释其生成的，我们提出了一条简单直接的四元环中间体生物合成途径，合理解释了其生成机理和以C33为主峰的原因；⑥根据鉴定出的5个新丛粒藻烷类化合物和3个含氧中间体之结构和碳数变化，我们提出了一条成岩演化途径，合理解释了茂名盆地新丛粒藻烷的结构碳数演变及其特殊分布之谜。.通过上述研究，证实了丛粒藻B种和L种在茂名油页岩中的共生和存在，对新丛粒藻烷的重碳同位素成因进行了解释。分子结构鉴定方面属最大的创新，克服了有机化合物分离、提纯和高纯制备的难题，学习和掌握了NMR技术；在丛粒藻培养方面开展了尝试和实践，后续还需要培养出B种藻株，扩培后开展各种营养盐（含铁质纳米矿物）的生长刺激培养实验，才能对第三代的生物质能源研究提供科学证据和应用价值。