Petrogenesis and metallogenic implications for the Machang, Huangdaoshan, and Tuncang plutons in eastern Anhui: an integrated age, petrologic, and geochemical study

ABSTRACT

The Tuncang–Chuzhou–Machang area (eastern Anhui province) is geologically located in the intersection between the Yangtze block and the Qinling–Dabie orogenic belt. Many Mesozoic plutons outcrop in this district that are Cu–Au prospective but inadequately studied. We report new LA-ICP-MS zircon U–Pb ages, petrologic, and whole rock geochemical data for three representative plutons at Machang, Huangdaoshan, and Tuncang. New dating results suggest that all the Machang (129.3 ± 1.6 Ma), Huangdaoshan (129 ± 1.7 Ma), and Tuncang (130.8 ± 1.9 Ma) plutons were emplaced in the Early Cretaceous, slightly older than other plutons in neighbourhood of the Zhangbaling uplift. The three plutons contain typical low-Mg adakitic affinities, in which the rocks contain SiO₂ >56%, Al₂O₃ ≥15%, Mg# <53, elevated Sr, Ba, Cr, Ni, Sr/Y, and La/Yb, low Y and Yb and no discernible Eu anomaly. Their petrogenesis may have been related to the delamination and partial melting of the lower crust, which is different from the Chuzhou pluton, which was interpreted to have formed by partial melting of the subducted slabs. We suggest that this petrogenetic difference may explain why the pluton at Chuzhou is Cu–Au fertile, whereas those at Machang, Huangdaoshan, and Tuncang are largely barren. It is proposed that adakitic plutons formed by partial melting of the subducted slabs have high metallogenetic potentiality in the area.

KEYWORDS:

• Mesozoic adakitic plutons
• Anhui
• Yangtze block
• lower crusts delamination
• Cu–Au mineralization
• LA-ICP-MS dating

Acknowledgements

We thank Huang XianJue from the 312 Geological Brigade of Anhui Geology & Mineral Resources Exploration Bureau for their valuable support during the fieldwork. We are grateful for the official review by two anonymous reviewers. This work was financially supported by National Key Research and Development Plan: [Grant Number 2016YFC0600206], National Natural Science Foundation of China: [Grant Numbers 41672081, 41320104003, and 41172084], and Public Welfare Project of Anhui Province: [Grant Number 2015-K-2, K-3].

Disclosure statement

No potential conflict of interest was reported by the authors.

Highlight

1. Zircon U–Pb dating confirms Machang, Huangdaoshan, and Tuncang plutons age.

2. The petrogenesis of these three plutons may have been related to the lower crustal delamination and partial melting based on their geochemical features.

3. Partial melting products of the subducted oceanic slabs which can be explained the Cu–Au fertile in Chouzhou pluton for regional Cu–Au mineralization.

Supplemental data

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [Grant Numbers 41172084, 41320104003, and 41672081];  National Key R&D Program of China: [Grant Number 2016YFC0600206]; and Public Welfare Project of Anhui Province: [Grant Number 2015-K-2, K-3].