Geochronology and Geochemistry of Gneiss, Migmatite, and Granite from the Zhenghe Area, SE China: Implications for Late Paleozoic–Mesozoic Crustal Evolution of the Cathaysia Block

Abstract

Rocks in the Cathaysia Block record multiple tectonic events and provide a window to understand the evolution of the South China Block. This study reports geochronological, geochemical and Sr-Nd-Hf isotopic data for gneiss, granite, and migmatite in Zhenghe. The gneiss yielded an upper intercept age of 1,942 Ma, reflecting reworking of protolith. The migmatites formed at 399 Ma, slightly earlier than the granite (∼392 Ma). Melanosomes displayed nearly flat chondritenormalized rare earth element patterns, along with (⁸⁷Sr/⁸⁶Sr)_i and ε_Nd(t) values of 0.7062–0.7155 and –11.0 to 0.3, exhibiting a lower crustal affinity. Geochemical characteristics of the leucosome and granite differed from those of the melanosome, and the degree of element enrichment or depletion was higher. The Sr-Nd isotopic compositions of granite and leucosome were different, but both suggest a crustal origin. In addition, the gneiss revealed a Mesozoic tectono–metamorphic overprint, likely related to crust thickening. Our research suggests that late Paleozoic anatexis resulted from collision between the Gondwana continent and the West Cathaysia Block. Underthrusting of the East Cathaysia Block beneath the West Cathaysia Block contributed to Mesozoic orogeny. Our new data document Paleoproterozoic reworking, Paleozoic anatexis, and Triassic metamorphism, providing novel insights into evolution of the Cathaysia Block.

Keywords

anatexis / late Paleozoic–Mesozoic / zircon U-Pb ages / Sr-Nd-Hf isotope / Zhenghe area / Cathaysia Block

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2025 Geological Society of China