K-Ar and 40 Ar/39Ar geochronology of weathering process
K-Ar and 40 Ar/39Ar geochronology of weathering process
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DOI：
10.1146/annurev.earth.27.1.183
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
P. Vasconcelos
中科院分区：
文献类型：
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作者：
P. Vasconcelos
■摘要大陆风化过程K-Ar和40 Ar/39 Ar测年应用的最新进展表明该方法适用于风化剖面中存在的矿物测年。明矾石族硫酸盐和锰氧化物通常通过风化反应沉淀，30年前首次采用K-Ar法进行分析。最近，这些矿物被证明是适合的40 Ar/39 Ar年代学，尽管他们的细粒的习惯。K-Ar法的整体性和风化剖面中矿物组合的复杂性限制了风化作用的K-Ar定年。40 Ar/39 Ar方法可能的单晶方法允许风化剖面的研究，其中明矾石和黑锰矿族矿物作为次要相出现。可能与40 Ar/39 Ar方法的步进加热分析提供有关的Ar和K的保留历史，深成污染物的存在下，和可能的39 Ar反冲样品辐照过程中的信息。全自动.
▪ Abstract Recent developments in the application of K-Ar and 40Ar/39Ar dating of continental weathering process demonstrate the method's suitability for dating minerals present in weathering profiles. Alunite-group sulfates and hollandite-group manganese oxides, which often precipitate through weathering reactions, were first analyzed by the K-Ar method 30 years ago. Recently these minerals were shown to be suitable to 40Ar/39Ar geochronology, despite their fine-grained habits. The bulk nature of the K-Ar technique and the complex mineral assemblages in weathering profiles restrict K-Ar dating of weathering processes. The single-crystal approach possible with the 40Ar/39Ar method allows the study of weathering profiles where alunite- and hollandite-group minerals occur as minor phases. Step-heating analysis possible with the 40Ar/39Ar method provides information about the Ar and K retention histories, the presence of hypogene contaminants, and possible 39Ar recoil during sample irradiation. Fully automat...