摘要
综合地质、生物、化学、物理等多学科的实验方法模拟化石蓝藻的形成过程,即将现代丝状蓝藻Oscillatoria tenuis浸入SiO_2溶胶中;加入电解质和调节pH值后,SiO_2溶胶转化为凝胶;再进一步在高温高压条件下将样品转变成埋藏于蛋白石硅质矿物中的蓝藻化石。对人工硅化化石切片的形态学观察发现,人工硅化蓝藻化石与前寒武纪燧石层中的蓝藻化石具有可对比性。不同的温度压力条件对化石形态、颜色,细胞结构有不同程度的影响。对人工硅化蓝藻化石的有机质分析表明,样品的烷烃部分C_(17)正烷烃占绝对优势;随着温度压力的提高,长链正烷烃的含量逐渐增加。另外还检测到具398nm吸收峰的一种新色素,它可能是一种叶绿素a的降解产物。
Artificially silicified microfossils were obtained by means of the technique involving permeation of the blue-green alga Oscillatoria tenuis, through solution of colloidal silica, conversion of the silica sol to silica gel, and transformation of the amorphous silica gel containing embedded algae into opal under conditions of rising temperature and pressure. The algal filaments in the opal thin section appeared unchanged in cell size, had clear cell wall, were yellow-brown in colour, and had fussy intracellular structure when artificially silicified at a temperature of 250℃ and under a pressure of 1.013×0~7 Pa for 100 hours. But when silicified at a temperature of 350℃ and under a pressure of 3.040×10~7 Pa for 100 hours, they were reduced in size, had fussy cell wall, and were of reddish-brown colour; and there was no trace of intraeellular structure. The organic matter in the opal thin section was clearly observed near the silieified cell wall under both conditions. Analysis of the composition of the extractable organic matter from the opal-embedded artificially fossilized alga showed that the quantity of alkane was almost three times more at 250℃ and 1.013×10~7 Pa than that at 350℃ and 3.040×10~7 Pa. Data of gas chromatography showed a dominance of C_(17) normal alkane in all samples, but the long chain normal alkanes (about C_(29)-C_(31)) increased with increasing temperature and pressure. A new pigment compound was detected in the artificial fossils with a peak of visible absorption spectrum at 398nm, which was considered as degradation from chlorophyll a. A discussion is also made on implications of the results from the micropaleontological and organic geochemical experiments as mentioned above.
出处
《微体古生物学报》
CSCD
北大核心
1991年第2期197-206,251,共10页
Acta Micropalaeontologica Sinica
基金
国家自然科学基金
国家教委优教基金
