Tracing Orogenic Evolution From Multi-Detrital Mineral Records: U-Pb Geochronology and Trace-Element Constraints From Glacial Diamictites

Abstract

Integrating multiple detrital mineral systems provides a powerful framework for reconstructing source-region tectonothermal evolution because different minerals record complementary aspects of magmatic and metamorphic processes. Glacial diamictites are particularly valuable for this approach because extensive glacial erosion can sample broad source regions and diverse crustal levels while minimizing chemical weathering and preserving unstable mineral phases. Here, we present integrated U-Pb geochronological and trace-element analyses of detrital apatite and rutile from Marinoan-aged glacial diamictites of the Yangtze Block in South China and combine these data with existing zircon data sets. Detrital apatite records dominant mafic and I-type magmatism between ∼970 and 650 Ma, with more evolved peraluminous signatures appearing at 850–820 Ma, broadly consistent with declining zircon εHf(t) values. Detrital rutile reveals dominant Neoproterozoic (∼970–790 Ma) and subordinate Paleoproterozoic (2.2–1.8 Ga) metamorphic signatures. Zr-in-rutile thermometry indicates temperatures of 480°C–980°C, including a distinct ∼950–820 Ma high-pressure, low-temperature population consistent with blueschist- to eclogite-facies conditions. These data record major tectonic transitions within the Panxi-Hannan orogen of the northwestern Yangtze Block, from an intra-oceanic arc (970–880 Ma) to a continental arc (870–790 Ma), followed by regional extension after 790 Ma. The cessation of rutile and metamorphic apatite ages coincides with the onset of regional extension in the source orogen. The ∼950–820 Ma cold-subduction signature expands the global record of Tonian low-geothermal-gradient metamorphism. Our results demonstrate that integrating multiple detrital mineral systems yields a more complete tectonic history than any single provenance proxy.