Continental Crust Rejuvenation Across the Paleo‐Mesoarchean Transition Resulted From Elevated Mantle Geotherms.

The increase in initial Hf isotopes identified in early Mesoarchean detrital zircon is commonly interpreted as a reflection of the geodynamic transition from stagnant‐lid to mobile‐lid tectonics. However, given the lack of petrogenetic context, interpreting detrital zircon may lead to spurious conclusions. In this contribution, we use zircon U‐Pb‐Hf‐O isotopic and bulk rock compositions of newly identified 3.05–2.9 Ga granitoids from the SW Yangtze Block to posit petrogenesis within an isotopically juvenile magmatic system. A statistical analysis of these data with a global igneous zircon Lu‐Hf isotopic compilation reveals an increase in average initial radiogenic Hf isotopes during the Paleoarchean to Mesoarchean transition. We posit that the Earth's continental crust underwent a global rejuvenation across the Paleo‐Mesoarchean transition. This rejuvenation can be explained by an independently observed increase in mantle temperatures resulting from mantle thermal evolution and does not require a change in tectonic style. Plain Language Summary: In this study, we explore the Earth's continental crust evolution before 3.0 billion years ago, a period characterized by limited preserved ancient rocks. We focus on zircon from igneous rocks, which provides a more reliable petrogenetic record than detrital zircon. Our study challenges the widely observed increase in detrital zircon initial Hf isotopes during the Paleo‐to Mesoarchean transition, often interpreted as a shift in tectonic regimes. We present new data from 3.05 to 2.9 billion‐year‐old granitoids in the Yangtze Block, suggesting isotopically juvenile magmatic activity. Statistical analysis of a global database of igneous zircon Hf isotopes reveals a state‐shift increase in εHf(t) across the Paleo‐to Mesoarchean transition, indicating global crustal rejuvenation at that time. Contrary to prevailing theories, we propose that this rejuvenation can be attributed to elevated mantle temperatures, challenging the notion of a significant geodynamic change during this period. Our findings emphasize the need to consider mantle thermal evolution in understanding continental crust growth on early Earth. Key Points: 3.05 and 2.9 Ga granitoids derived from juvenile crust are identified in the SW Yangtze BlockGlobal crust rejuvenation occurred across the Paleo‐to Mesoarchean transitionThis period of rejuvenation resulted from the effects of peak mantle temperatures [ABSTRACT FROM AUTHOR]