Search

The formation of rodingites has been a continually controversial topic, largely due to the absence of minerals that can be unambiguously dated. Here, we present a case study that utilized LA‐ICPMS garnet U–Pb dating, in conjunction with field investigations, petrology and Raman spectroscopy, to reveal the age and petrogenesis of rodingite in the northern North China Craton. The rodingites are spatially associated with mafic and alkaline rocks. Our findings indicate that rodingitization occurred at ca. 388 Ma, making it about 5–10 Myr younger than its mafic protoliths, but contemporaneous with the adjoining alkaline plutons. These observations suggest that the rodingitization may be attributed to hydrothermal fluids from the alkaline magmas. Our study emphasizes the importance of utilizing garnet U–Pb dating to determine the timing of rodingitization and introduces a novel perspective on the relationship between rodingitization and alkaline magmas in extensional continental settings. [ABSTRACT FROM AUTHOR]

An integrated study of zircon U-Pb ages and Hf-O isotopes, whole rock and apatite geochemistry, and whole rock Sr-Nd-Hf isotopes were conducted for the Jurassic adakitic volcanic rocks from the Tiaojishan Formation in the Yanshan Fold and Thrust Belt (YFTB) of the North China Craton, to investigate their genesis, with attention to the role of crust thickness in achieving the adakitic traits. Zircon U-Pb dating gives eruption ages of 162–158 Ma for these rocks. These rocks have variable SiO 2 (55.7–68.1 wt%) and MgO (0.35–4.0 wt%), and adakitic trace element signatures including high Sr/Y (27.9–100) and (La/Yb) N ratios (9.6–27.6). Chemical variations in whole rock and apatite suggest a feldspar-dominated fractional crystallization, superimposed by variable mineral accumulation on whole rock compositions. Together with isotopic compositions that include evolved whole rock (87Sr/86Sr) i = 0.70447–0.70591, ε Nd (t) = −17.5 to −12.1, and ε Hf (t) = −22.2 to −11.2, and zircon ε Hf (t) = −26.8 to −11.2 and δ18O = 5.7–7.0 ‰, we attribute these rocks are sourced from mafic lower continental crust. By comparing the trace element signatures between the examined samples and modern continental arc magmatic rocks formed at variable crustal thickness, it is suggested that these rocks are most likely originated from a thickened crust. A further estimate based on whole rock Sr/Y and La/Yb gives a crust thickness of 56 ± 7 km. The crust thickening and associated uplift of the YFTB could be attributed to the westward subduction of the Paleo-Pacific plate. This led to a high altitude (∼3.8 ± 0.9 km) and cool climate habitat (a mean annual paleotemperature of 7 ± 7 °C) for the Yanliao Biota lived therein during this period, which may have played an important role in the earliest appearance of the feathered characteristic of dinosaurs. • A thickened lower continental crust source is responsible for the volcanic rocks. • Crust thickening and uplift are related to the subduction of the Paleo-Pacific plate. • Uplift-induced cooling may be important for the appearance of feathered dinosaurs. [ABSTRACT FROM AUTHOR]