Late Mesozoic high-K calc-alkaline magmatism in Southeast China: the Tongling example

ABSTRACT

We report new zircon U–Pb ages, Hf isotopic and geochemical results for the Tongling granitic plutons of Southeast China. SHRIMP U–Pb ages for the Miaojia quartz monzodiorite porphyrite，the Tianebaodan and Tongguanshan quartz monzodiorites, the Xinqiaotou granodiorite porphyry, and the Shatanjiao and Nanhongchong granodiorite are 143 ± 2, 141 ± 1 and 142 ± 1, 147 ± 1, and 145 ± 1 and 139 ± 1 Ma, respectively. Combined with previous geochronological data, our results indicate that the porphyritic rocks are older than rocks of the same type lacking porphyritic texture. Geochemically, these high-K calc-alkaline intrusive rocks are characterized by arc-like trace element distribution patterns, with significant enrichment in LILE and LREE but depletion in HFSE. Lu–Hf isotopic compositions of zircons from the high-K calc-alkaline (HKCA) rocks have ε_Hf(t) values of magmatic 139–147 Ma zircons from −8.1 to −25.6, with two-stage model ages (t_DM2) of 1.71–2.67 Ga, whereas ε_Hf(t) values of inherited 582–844 Ma zircons range from 5.4 to −9.5, with t_DM2 of 1.39–2.22 Ma, younger than t_DM2 values of igneous zircon, indicating that newly formed mantle material was added to the continental crust of the Yangtze Block. Moreover, ε_Hf(t) values of inherited zircon cores older than 1000 Ma are from −7.8 to −26, similar to magmatic zircons, and the t_DM2 values are all greater than 3.0 Ga (3.16–3.75 Ga), reflecting partial melting of ancient sialic material. We conclude that the plutonic melts were derived from both the enriched mantle and the ancient crust. The HKCA Tongling intrusions coincide temporally with the J₃–K₁ magmatic event that was widespread in Southeast China. This igneous activity may have accompanied sinistral slip along the Tan-Lu fault due to oblique subduction of the Palaeo-Pacific plate.

KEYWORDS:

• Zircon U–Pb chronology
• Hf isotopes
• high-K calc-alkaline intrusive rocks
• Tongling

Acknowledgements

This paper is cosponsored by Natural Science Fund Project Nos. 41472063 and 40921001, Science and Technology Project of Land and Resources from Anhui province (2012-K-03) (Study on the metallogenic regularity and prospecting predition of the porphyry copper deposits in Tongling County, Anhui Province), and National Specific Project No. SinoProbe-05-05. We are grateful to Dr Robert J. Stern, Editor-in-Chief of International Geology Review and three anonymous reviewers for insightful and constructive reviews of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Natural Science Fund [project numbers 41472063 and 40921001], Science and Technology Project of Land and Resources from Anhui province [2012-K-03] (study on the metallogenic regularity and prospecting prediction of the porphyry copper deposits in Tongling County, Anhui Province), and National Specific [project number SinoProbe-05-05].