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本文旨在介绍用长寿命放射性衰变系统首次直接测定沉积碳酸盐岩的年龄。津巴布韦南部马斯文戈(旧称维多利亚堡)绿岩带的穆香迪克叠层石灰岩,其Pb/Pb等时线年龄为2839±33Ma。已发表的关于穆香迪克灰岩的年龄(～3.5Ga)的主张,其根据是猜想的穆香迪克花岗岩对它的侵入,据报道,该花岗岩体的Rb/Sr全岩年龄为3445±260Ma。穆香迪克花岗岩体的最新Rb-Sr和Pb/Pb同位素数据表明,该花岗岩体的侵位年龄可能为～2900Ma,新的野外证据表明,该花岗岩体构成了叠层石灰岩沉积的基底。因此,这些新年龄数据并不支持穆香迪克藻叠层石的年龄为～3.5Ga。Pb/Pb等时线方法可以测定前寒武纪含化石灰岩和不含化石灰岩的沉积年龄,因而对古生命问题的解决具有广泛的应用范围。
This article aims to introduce the first direct determination of the age of sedimentary carbonate rocks using long-lived radioactive decay systems. The Muntick laminated limestone in the Masstone (formerly Victoria Fort) greenstone belt in southern Zimbabwe has a Pb / Pb isochron age of 2839 ± 33Ma. Published assertions of age (~3.5Ga) for the Mutildik limestone are based on the conjecture of its invasion by the Muchadike granite, which reportedly had a Rb / Sr whole-rock age of 3445 ± 260 Ma . The latest Rb-Sr and Pb / Pb isotopic data from the Muntick granite show that the emplacement age of the granite may be ~ 2900 Ma, and new field evidence suggests that the granite forms the basement for laminated limestone deposition. As a result, these new age data do not support the age of ~3.5Ga for Mutiadikaponite strata. The Pb / Pb isochron method can determine the age of Precambrian calcified limestone and non-calcified limestone, and thus has a wide range of applications for the resolution of paleontological problems.