Determination of isotopic ratios, abundances and chemical species (chemical state) on platinum group elements and its application to the study of geochemical cycle and environmental change on the surface of the Earth

测定铂族元素的同位素比、丰度和化学形态（化学态），以研究地球表面的地球化学循环和环境变化。1．大陆地壳上的铼-锇系统学：报告了塔克拉玛干沙漠沙和昆仑山冰川冰碛的第一个铼-锇同位素数据。来自不同地区的塔克拉玛干沙漠沙子显示出令人惊讶的均质锇同位素数据。研究表明，塔克拉玛干沙漠的沙子来源于沙漠周围的冰碛和河流沉积物或西藏土壤，并因沙漠中的风沙活动而均质化。将塔克拉玛干沙漠砂的Re-Os数据与黄土高原黄土的Re-Os数据进行了比较，得出黄土的Re-Os数据可以用来代替上陆壳。2．基于 X 射线吸收精细结构光谱的铁陨石和铂矿石样品中锇的形态：……更多我们报道了第一个基于同步辐射的 X 射线吸收精细结构 (XAFS) 光谱，用于地球和宇宙化学材料中的锇，并表明铁陨石和铂矿石中的锇主要以金属形态存在。预计XAFS技术在天然样品中Os形态分析中的进一步应用将有助于阐明Re-Os同位素系统中Re/Os分馏过程。 3．海洋中锇同位素比的演变（P-T边界锇同位素比）：日本西南部外围燧石推导的锇同位素组成显示，早二叠世至三叠世地幔物质对海水的贡献较高，表明P-T边界大灭绝事件更可能是由大型火成岩省活动引起的。 4． Re和Os从海水到沉积物的去除机制：在海水-沉积物系统中，研究表明Re仅在还原环境下从海水中去除，而Os在各种氧化还原条件下很容易从海水中去除到沉积物中。较少的

Isotopic ratios, abundances and chemical species (chemical state) on platinum group elements were determined to study geochemical cycle and environmental change on the surface of the Earth.1. Rhenium-osmium systematics on continental crust : The first Re-Os isotopic data were reported for the Taklimakan Desert sands and glacial moraines from the Kunlun Mountains. The Taklimakan Desert sands from various regions show surprisingly homogeneous Os isotopic data. It is supported that the Taklimakan Desert sands are derived from moraines and river sediments around the desert or from Tibetan soils and are homogenized by aeolian activity in the deserts. Our Re-Os data for the Taklimakan Desert sands were compared with those of loess from the Loess Plateuau, and it was concluded that the Re-Os data for the loess can be used and as proxy for the upper continental crust.2. Speciation of osmium in an iron meteorite and a platinum ore specimen based on X-ray absorption fine-structure spectroscopy : … More We reported the first synchrotron radiation-based X-ray absorption fine structure (XAFS) spectra for Os in geo- and cosmo-chemical materials and showed that Os in the iron meteorite and the platinum ore chiefly exist as a metallic species. It is expected that further application of the XAFS technique to the Os speciation in natural samples will be help to elucidate Re/Os fractionation processes in the Re-Os isotopic system.3. Evolution of Os isotope ratios in the ocean (Osmium isotope ratio at P-T boundary) : Osmium isotopic compositions deduced from cherts from the outer zone in the southwest Japan show the higher contribution of mantle material to seawater from early Permian to Triassic, suggesting the mass extinction event at P-T boundary is more likely caused by large igneous province activity.4. Removal mechanism of Re and Os from seawater to sediments : In seawater-sediment system, it was shown that Re was removed from seawater only under reducing environment and Os was readily removed from seawater to sediments under various redox conditions. Less