Abstract The Eastern Cathaysia Block located to the western side of the Pacific Plate was mainly covered by late Mesozoic intrusive and volcanic rocks, and the age and composition of its basement remain enigmatic. Here we firstly report U–Pb and Hf isotopes in zircon xenocrysts from late Mesozoic mafic sub-volcanic rocks in Pingtan Island, the east coastal area of the Eastern Cathaysia Block, with surprising Paleoproterozoic to Archean U–Pb isotopic ages. Neither ca. 1.8 Ga nor 1.0–0.7 Ga age peaks that are very typical in the outcropping rocks (including the Neoproterozoic sedimentary rocks in Pingtan Island) in the South China Block is identified. The two main Precambrian age peaks of 3.4–3.0 Ga and 2.6–2.2 Ga of these zircon xenocrysts are explained by contamination from the sediments in the unexposed basement. The youngest two Paleoproterozoic zircon xenocrysts may indicate the deposition of the basement close to ca. 1.8 Ga. The identification provides clues to the existence of the Paleoproterozoic basement in the Eastern Cathaysia Block. It may further suggest that the late Mesozoic (continental arc?) magmatism in the Eastern Cathaysia Block was most likely developed on and contaminated by the Paleoproterozoic basement.

中文翻译：

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晚中生代火山岩锆石异晶揭示东华夏地块下的古元古代基底

摘要 位于太平洋板块西侧的东华夏地块主要被晚中生代侵入岩和火山岩覆盖，其基底的年龄和成分仍是一个谜。在这里，我们首先报告了东华夏地块东部沿海地区平潭岛晚中生代基性亚火山岩中锆石异种晶中的 U-Pb 和 Hf 同位素，具有令人惊讶的古元古代至太古代 U-Pb 同位素年龄。都没有。确定了华南地块出露岩石（包括平潭岛新元古代沉积岩）中非常典型的1.8 Ga和1.0-0.7 Ga年龄峰。这些锆石异晶的两个主要的前寒武纪年龄峰值 3.4-3.0 Ga 和 2.6-2.2 Ga 可以通过未暴露基底中沉积物的污染来解释。最年轻的两个古元古代锆石异晶可能表明基底的沉积接近约 1.8 Ga. 该鉴定为东华夏地块存在古元古代基底提供了线索。这可能进一步表明东华夏地块的晚中生代（大陆弧？）岩浆活动很可能是在古元古代基底上发育和污染的。