Nb、Ta在锆石和花岗质熔体中分配系数的实验研究

Nb and Ta, as high filed elements, have identical ion radium (～0.64?) and same value(+5). Which make them to have same geological behavior in geological process.In the evolution of crust-mantle, some special geological condition can cause their partitioning. As a common accessary mineral,whether zircon can cause fractionation between Nb and Ta or not in geological process,it is not fully understood by now.The changes of partitioning coefficents of Nb and Ta between zircons and felsic melts with temperature and pressure will be eximed by experiments.which will provide clues for fractionation between Nb and Ta in geological process.The experiments will also give the relationship between Ti contents in zorcon and felsic melt which can be used as correcton of Ti-in-zircon thermometer without rutile in systems. The accurately determined Nb and Ta contents in zircons from different origins may provide discrimination factors for the zircons from different rocks combining with other trace element characters.

Nb、Ta同为高场强元素，由于它们具有相近的离子半径(～0.64?)和相同的化学价态(+5)，使得它们在地质过程中具有相似的地球化学行为。在壳-幔演化过程中，一些特殊的地质条件会导致这两个元素的分馏。锆石作为自然界中最常见的副矿物之一，在地质过程中是否会对Nb、Ta产生分馏作用，目前还缺乏研究。本研究将通过实验的方法获得Nb、Ta在锆石和花岗质岩浆中的分配系数随温度和压力的变化，为研究地质过程中锆石是否会对Nb、Ta元素进行分馏提供证据。并利用实验数据，确定花岗质岩浆中TiO2不饱和时，锆石中Ti含量和熔体中Ti含量的关系，提供锆石Ti温度计的校正系数。通过不同成因锆石中Nb、Ta含量的准确测定，结合其它微量元素特征，为锆石的成因判别提供有效的依据。