Origin of gem-quality megacrysts in the Cenozoic alkali basalts from the Muling area, northeastern China

Hu, Lianxi; Pan, Shaokui; Lu, Ren; Zheng, Jianping; Dai, Hancheng; Guo, Anhong; Li, Yu; Sun, Haiqi

doi:10.1016/j.lithos.2022.106720

Cited by 1 publication

(1 citation statement)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Megacrystic zircons (which are typically centimeter-sized) are found within intraplate alkali basalt deposits around the world; their derivatives are formed as a result of secondary processes, especially those seen in the countries along the western Pacific continental margins [6][7][8][9]. These basalts commonly contain abundant mantle xenoliths, along with a variety of high-pressure megacrysts such as corundum, pyroxene, garnet and spinel [10][11][12][13], offering scientists an opportunity to elucidate the composition and evolutionary history of the deep lithosphere. Some species of megacrysts (e.g., corundum and zircon) have also been commercially exploited for several centuries to supply the global market with gemstones [14].…”

Section: Introductionmentioning

confidence: 99%

Age and Geochemistry of Zircon Megacrysts from Alluvial Deposits in the Huadian Area, Northeastern China

et al. 2023

Self Cite

View full text Add to dashboard Cite

Megacrystic zircons have recently been found in alluvial deposits in the Huadian area of northeastern China. However, studies have rarely been conducted on these zircons. In this article, we present systematic in situ trace element, U-Pb age and Hf isotope data regarding these Huadian zircons, with the aim of investigating their source characteristics and provenance. The studied zircons, with a diameter of 0.7–1.2 cm, are dominantly irregular in shape and have a rounded termination, with a color ranging from near-colorless to reddish brown to maroon. The zircons show oscillatory zoning in CL images, with a Th/U value of 0.18–1.27, which is consistent with the typical features of magmatic zircons. The positive εHf(t) value of Huadian zircons (4.8–9.2) further indicates the presence of precipitation from the mantle-derived melt, with limited contamination of the crustal components. The obtained weighted mean 206Pb/238U age for these zircons is 17.9 ± 0.12 Ma, which is slightly older than the eruptional ages of the associated alkali basalts (from 17.6 ± 1.09 Ma to 17.8 ± 0.69 Ma), implying a short residence time in the mantle before entrainment. Huadian zircons incorporate a wide range of trace elements, including ΣREE (117–2790 ppm), Hf (4902–11856 ppm) and Y (145–3645 ppm) contents, generating mixed-source protolith assignments. As is suggested by the moderate variations seen in the Hf isotopes, we propose that the source melts of Huadian zircons are complex in nature, which is likely the result of the chemical heterogeneity of the upper mantle.

show abstract