Genesis of zircon and its constraints on interpretation of U-Pb age

Zircon U-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon U-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of U-Pb age. Three methods have been proposed to link zircon U-Pb age to metamorphic conditions: ( i ) internal structure; ( ii ) trace element feature; (iii) mineral inclusion composition. Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances, with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks. Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore, interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.     

长江与黄河现代表层沉积物元素组成及其示踪作用

长江与黄河现代表层沉积物中常量及微量元素组成特征明显不同。长江相对富Ｋ、Ｆｅ,Ａｌ等常量元素及绝大多数微量元素,且元素含量变化大;而黄河相对富Ｃａ,Ｎａ,Ｓｒ,Ｚｒ,Ｈｆ等少数元素,元素含量变化较小;Ｃｕ,Ｚｎ,Ｓｃ,Ｔｉ,Ｆｅ,Ｖ,Ｎｉ,Ｃｒ,Ｍｎ,Ｌｉ,Ｚｒ,Ｈｆ,Ａｌ等元素及Ｌａ／Ｓｃ,Ｔｈ／Ｃｏ,Ｌａ／Ｃｏ,Ｔｉ／Ｚｒ,Ｚｒ／Ｙ等元素比值可较好地用来区分长江与黄河沉积物,以探索长江与黄河的     

用同位素稀释质谱法测定微量稀土元素

用同位素稀释质谱法测定高纯物中或植物样品中8种微量稀土元素Ce,Nd,Sm,Eu,Gd,Dy,Er和Yb,讨论干扰和分馏偏差校正.该法精密度好于1％,检出限小于2.3×10~(-9)g,准确度优于±5%.     

走进医院的诺贝尔化学奖

说到诺贝尔化学奖,人们首先想到的往往是聚合、氟化、染色体等高深科学领域,让人觉得高不可攀.而今年的这一奖项让我们看到了身边的事物,"绿色荧光蛋白的发现"这个获奖题目听起来虽然还是很专业,可是如果说它用于搜索癌症等病变细胞的位置,亦即"示踪元素",我们就不再生疏了.三位获奖者中的下村修就是发现这种荧光蛋白的第一人.