New geochronometer for the direct isotopic dating of native platinum minerals (190Pt-4He method)
New geochronometer for the direct isotopic dating of native platinum minerals (190Pt-4He method)
复制标题
用于天然铂矿物直接同位素测年的新型地质计时器（190Pt-4He 法）
作者：
Y. Shukolyukov;O. Yakubovich;A. Mochalov;A. Kotov;E. Sal’nikova;S. Yakovleva;S. Korneev;B. M. Gorokhovskii
提出了一种基于天然同位素 190Pt α 衰变的同位素地质年代学新方法，用于测定天然铂矿物的年代。通过对包括铂在内的天然金属晶格中氦的热脱附分析，我们能够预测天然铂矿物中放射性 4He 在达到其熔化温度时具有非常高的热稳定性（保留率）。为了验证所提出的 190Pt-4He 方法，对 Galmoenan 纯铜矿-单斜辉石岩和 Kondyor 碱性超镁铁岩地块中的异铂进行了直接同位素测年。通过这种方法对来自 Galmoenan 地块 (70 ± 5 Ma) 的原生铂矿进行的测年结果与地质观测和平均 Sm-Nd 和 Rb-Sr 同位素年龄估计一致。从 Kondyor 地块获得的砂矿异铁铂 190Pt-4He 年龄 (112 ± 7 Ma) 也与地质观测结果一致，并且接近 koswites（金云母辉石岩、辉长岩、霞石正长岩和纯岩之后的交代岩）的 K-Ar 和 Rb-Sr 年龄。我们的实验数据表明，190Pt-4He 方法是一种很有前景的天然铂矿物测年工具。
A new method of isotope geochronology was proposed for dating native platinum minerals on the basis of the α-decay of the natural isotope 190Pt. The analysis of the thermal desorption of helium in the crystal lattice of native metals, including platinum, allowed us to predict a very high thermal stability (retentivity) of radiogenic 4He in native platinum minerals up to their melting temperatures. In order to validate the proposed 190Pt-4He method, direct isotopic dating was performed for isoferroplatinum from the Galmoenan dunite-clinopyroxenite and Kondyor alkaline ultramafic massifs. The results of dating obtained by this method for primary ore platinum from the Galmoenan Massif (70 ± 5 Ma) are consistent with geological observations and mean Sm-Nd and Rb-Sr isotopic age estimates. The 190Pt-4He age obtained for placer isoferroplatinum from the Kondyor Massif (112 ± 7 Ma) also agrees with geological observations and is close to the K-Ar and Rb-Sr ages of koswites (phlogopite-magnetite pyroxenites, gabbros, nepheline syenites, and metasomatic rocks after dunites). Our experimental data demonstrated that the 190Pt-4He method is a promising tool for dating native platinum minerals.