ABSTRACT A sample of fine-grained grey Stockholm granite from the Frescati area just north of central Stockholm, east-central Sweden, earlier dated to 1803 +23/−19 Ma by the U-Pb zircon method using TIMS on multigrain fractions, has been reanalyzed using the Nordsim ion microprobe. The new age obtained, 1792±4 Ma, is more precise, and replaces the earlier highly discordant date. It agrees well with other ages for the formation of the Stockholm-type granites and related pegmatites, indicating an age of around 1.79 Ga for this late-orogenic Svecofennian granite magmatism. The Stockholm granite thus formed toward the end of the 1.83–1.79 Ga late Svecofennian metamorphic phase, and crosscuts earlier formed migmatitic gneiss structures in a brittle manner at the present-day level of exposure.

中文翻译：

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瑞典中东部 Frescati 斯德哥尔摩花岗岩的精细 U-Pb 年龄

摘要 来自瑞典中东部斯德哥尔摩市中心以北 Frescati 地区的细粒灰色斯德哥尔摩花岗岩样品，早在 1803 +23/−19 Ma，通过 U-Pb 锆石方法使用 TIMS 对多颗粒部分进行了鉴定。使用 Nordsim 离子微探针重新分析。获得的新年龄，1792±4 Ma，更精确，并取代了早期高度不一致的日期。它与斯德哥尔摩型花岗岩和相关伟晶岩形成的其他时代非常吻合，表明这种晚造山的斯韦科芬期花岗岩岩浆作用的年龄约为 1.79 Ga。因此，斯德哥尔摩花岗岩在 1.83-1.79 Ga 晚期 Svecofennian 变质期结束时形成，早期的横切面在当今暴露水平下以脆性方式形成混合片麻岩结构。