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在南秦岭地体中广泛分布着武当群变质沉积—火山岩组合的基底岩石,是东秦岭造山带重要的岩石单元,但对其形成时代的认识存在分歧。笔者通过对豫西地区武当地体北部武当群上部杨坪组变质沉积岩和下部双台组变质中酸性火山岩锆石U-Pb年龄的测定,认为杨坪组变质沉积岩沉积物源主要由晚元古代(860～640Ma)和早元古代(2260～1800Ma)、少量晚太古代和中元古代地壳物质构成,与扬子陆块具有亲缘关系。沉积时代应晚于640Ma。变质中酸性火山岩形成时代为730～780Ma之间,峰值(755±6)Ma,与双台组新元古代变质基性火山岩为同期岩浆作用的产物,成因上推测与Rodinia超大陆裂解作用有关。
The basement rocks of the Wudang Group metamorphic sedimentary-volcanic assemblage are widely distributed in the South Qinling terrane and are important rock units in the East Qinling orogenic belt. However, their understanding of the formation age is different. Based on the U-Pb dating of the Yangping metamorphic sedimentary rocks in the upper Wudang Group and the metamorphic intermediate-acid volcanic rocks in the lower part of the Wudang Group in western Henan, the authors believe that the sedimentary source of the metamorphic sedimentary rocks in the Yangping Formation is mainly composed of Late Proterozoic (860 ~ 640Ma) and early Proterozoic (2260 ~ 1800Ma), a small amount of Late Archean and Mesoproterozoic crustal material, and has a genetic relationship with the Yangtze block. Sedimentary era should be later than 640Ma. The metamorphic mid-acidic volcanic rocks formed between 730 and 780 Ma and peaked at (755 ± 6) Ma, and were derived from the Neoproterozoic metamorphic basement volcanic rocks of the Shuangtai Formation during the same period. The origin of the metamorphic mid-acidic volcanic rocks was related to the Rodinia supercontinental pyrolysis.