广西佛子冲铅锌（银）矿田岩浆岩的时代及地球化学特征

广西佛子冲铅锌（银）矿田内发育两个岩浆岩系列，即海西期弱碱质Ｓ型花岗岩系和燕山期钙碱质Ⅰ型花岗质火山岩系，两者的地球化学特征差异十分显著。钙碱质岩系由早期至晚期，其岩石特征参数、微量元素及稀土元素表现出规律性变化，反映出同源火山岩浆的演化特征。铅锌（银）成矿作用与钙碱质岩系，尤其是晚期浅成侵入体（次火山岩）密切相关。     

砾石钙膜纹层测年数据采集技术的实现方法及可行性分析

根据砾石钙膜纹层的明暗度测年是沉积物年代测定的一种新的思路．本阐述了用扫描仪对砾石钙膜切面直接进行高分辨率扫描，继而通过计算机获取其明暗度值并绘制明暗度一厚度曲线图，将它与其它定年结果对比确定砾石钙膜开始形成的年代的思路和实现方法．同时分别对同一剖面多次扫描，同一样品不同部位和同一阶地面上所取不同样品的结果进行了相关性分析，结果表明此方法是可靠的．     

The I-Xe chronometer

¹²⁹Xe, from the decay of the now-extinct 16.7 Ma¹²⁹I, accumulates in iodine-bearing sites and since most iodine host phases are secondary, the I-Xe system is typically a chronometer for post-formational processes. The validity of the I-Xe chronometer is confirmed by comparison with Pb-Pb ages on phosphate and feldspar separates from twelve meteorites. Phosphate separates are found to be concordant with Pb-Pb for all six samples in which useful I-Xe data were obtained. Feldspar is a better iodine host than apatite in H chondrites, typically providing good I-Xe isochrons. These too are concordant with the Pb-Pb ages of the corresponding phosphates for five out of six feldspar separates. The exception is Allegan whose feldspar yields one of the oldest I-Xe ages observed, similar to those for CI and CM magnetites. We attribute this to a more primary mineralization, predating the secondary phosphate from which the comparison Pb-Pb age was obtained. Absolute I-Xe ages, found using the reported Pb-Pb age of Acapulco phosphate provide an absolute I-Xe age of 4.566 ± 0.002 Ga for both Shallowater and Bjurböle irradiation standards. This allows relative I-Xe ages to be interpreted in the context of absolute ages.