【作者】 周杰；

【导师】 曾志刚；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质， 2012， 硕士

【摘要】 生活于海底热液区和冷泉区中的生物壳体能够记录所处海水的环境信息。本研究以西南印度洋脊（SWIR）热液调查区取得的藤壶壳体和美国加利福尼亚近海岸SantaMonica海盆冷泉区取得的双壳类壳体为研究对象，通过电子显微镜、X射线衍射（XRD）、C、O同位素测定等实验测试手段，对样品进行了矿物组成以及元素组成研究，以探讨深海极端环境下生物壳体记录的环境信息，为研究深海环境提供依据。本次研究得出以下两方面的成果：热液区样品：实验样品种类鉴定结果显示藤壶可能属于厚板藤壶科Pachylasmatidae，似厚板藤壶Pachylasmasp.的种。XRD测试结果显示，藤壶壳体矿物组成主要为方解石，仅有两个样品含有不到1%的石英杂质。壳体δ13C值分布在0.54–1.80‰之间，平均值为1.15‰（n=30），符合正常海相生物碳酸盐壳体δ13C值取值范围。壳体δ18O值分布在4.02–5.67‰之间，平均值为5.21‰（n=30），根据δ18O值范围推测，藤壶壳体形成时海水的盐度存在异常。通过对δ13C值和δ18O值的分析，可以推测藤壶靠近热液喷口生活，周围海水中的含碳气体浓度与正常海水环境差别不大。冷泉区样品：实验样品种类鉴定结果显示主要有以下两种双壳类：长形伴溢蛤CalyptogeniaelongataDall，扁满月蛤Lucinomasp.。XRD测试结果显示，两种冷泉双壳类壳体矿物组成主要为文石（99%以上）。壳体δ13C值分布在-23.05–2.11‰之间，平均值为-6.62‰（n=30），多数壳体δ13C为负值（低于-1.27‰），低于正常海相生物碳酸盐壳体δ13C值。个别壳体表现出13C较大亏损（δ13C值低至-23.05‰），且随年龄增长壳体δ13C值发生较大变化（变化幅度达到15.61‰）。这是至今报导的最亏损13C的新鲜海洋双壳类壳体。壳体δ18O值分布在2.19–3.66‰之间，平均值为2.91‰（n=30），部分壳体的δ18O值比与海水达到同位素平衡时形成的碳酸盐壳体重。通过对δ13C值和δ18O值的分析，可以推测双壳类周围的甲烷浓度发生了变化。更多还原

【Abstract】 Biogenic shells are good candidates for investigating the deep sea environment. The barnacle shell samples discussed in this paper were recovered from the southwest India ridge (SWIR). The bivalve shell samples studied here were obtained from the cold seep area of Santa Monica Basin, off shore of California. In order to investigate the circumstantial information recorded by biogenic shells a polarizing microscope, X ray powder diffraction and stable isotopes gas mass spectrometer were used for the mineralogy and stable isotopic analyses,which provide as a basis for studying deep-sea environments.The experiment results of barnacle shell from the hydrothermal area samples show that the barnacle belongs to slab barnacle Pachylasmatidea, Pachylasma sp. The X-ray Diffraction (XRD) results indicate that barnacle shell is predominantly of calcite (only two samples contain a little quartz which less than1%). The513C values of30samples are scattered between0.54%and1.80%with a mean of1.15%, within the range of normal biogenic shell δ13C values. The δ18O values of the30samples are scattered between4.02%o and5.67%o with a mean of5.21%. which derives that the salinity of seawater changed when shells were formed. The analysis of δ13C and δ18O values indicate that the barnacle lived near a hydrothermal vent, and the carbon gas concentration in ambient seawater is close to the normal marine environment level.The results of bivalve shells from the cold seep area samples illustrate that the bivalves belong to Calyptogenia elongata Dall and Lucinoma sp. However, the X-ray Diffraction (XRD) results indicate that bivalve shells are predominantly aragonite (more than99%). The δ13C values of30samples are from-23.05%to2.11%with a mean of-6.62%, lower than δ13C values of normal biogenic shell, and the carbon isotopic compositions of a shell were largely changed during its growth. Meanwhile, several shells δ13C value is depleted with minimum value of-23.05%. which is the most13C-depleted shells of fresh marine bivalves so far has been discovered. The δ18O values of the30samples are within the range of2.19%o to3.66%o with a mean of 2.91%o, and some samples are heavier than biogenic carbonate shell which precipitated in equilibrium with seawater. The analysis of δ3C and δ18O values has verified that the methane concentration in ambient seawater was increased.更多还原