Using Whole Rock and Zircon Geochemistry to Assess Porphyry Copper Potential of the Tonggou Copper Deposit, Eastern Tianshan

Xue-Bing Zhang,Shi-Shan Wu,Hong-Yan Quan,Feng-Mei Chai,Ke-Yong Wang,Shun-Da Li,Chuan Chen

doi:10.3390/min10070584

Xue-Bing Zhang, Shi-Shan Wu + Show 5 more

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https://doi.org/10.3390/min10070584

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Journal: Minerals	Publication Date: Jun 28, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Xinjiang University, UNSW Sydney, Jilin University

Abstract

Eastern Tianshan hosts a number of porphyry Cu deposits. However, these mainly formed in the Jueluotage Belt, in the middle part of Eastern Tianshan. The Tonggou porphyry Cu mineralization is an exception to this, since it is located in the Bogda Orogenic Belt, north of Eastern Tianshan. We obtained new zircon U-Pb ages, whole-rock geochemical data, zircon Hf isotope data, and zircon trace element compositions. LA-ICP-MS zircon U-Pb dating indicates a crystallization age of 302.2–303.0 Ma for the Tonggou mineralized granodiorite (TMG), which suggests that the Tonggou porphyry Cu mineralization formed in the Late Carboniferous period. εHf (t) data (1.8–14.1) for TMG suggests it was sourced from juvenile crustal melts, mixed with some mantle materials. TMG displays low ΣREE, compatible elements (Ba, Sr, Zr, and Hf), Zr/Hf and Nb/Ta ratios, as well as clearly negative Eu anomalies in whole rocks analyses. In addition, TMG is enriched in P, Hf and Th/U ratios in zircon, and has lower crystallization temperatures (734 to 735 °C) than the Daheyan barren granodiorite (DBG) (753 to 802 °C). Whole rock and zircon geochemical analyses show that the TMG was formed by fractional crystallization to a greater extent than the DBG in the Bogda Orogenic Belt. Moreover, zircon grains of the TMG show high Ce4+/Ce3+ ratios (159–286), which are consistent with related values from large porphyry deposits of the Central Asian Orogenic Belt (CAOB). High Ce4+/Ce3+ ratios reflect oxidizing magmas as a result of fractional crystallization, which indicates that the Tonggou deposit has potential to host a large porphyry Cu deposit.

Highlights

Porphyry Cu systems provide ~75% of global copper production and a set amount of co- or by-product Mo, Au, Pb and Zn [1,2]
The high water content and the oxidation state of magmas in these settings lead to mobilizing metals such as Cu partitioned into exsolved hydrothermal fluids and reprecipitated upon cooling to form porphyry Cu deposits [9,10]
Tonggou porphyry Cu mineralized age is consistent with vein Cu–Zn mineralized age [55], the similarity in ages of porphyry and vein mineralization in the Tonggou deposit indicate that vein Cu polymetallic mineralization is closely associated with porphyry Cu mineralization in temporal and spatial terms

Summary

Introduction

Porphyry Cu systems provide ~75% of global copper production and a set amount of co- or by-product Mo, Au, Pb and Zn [1,2]. Porphyry Cu is one of the most important metallogenic systems, and has attracted the attention of many economic geologists [3,4,5,6]. These systems always form in association with magmatism at subduction and collision setting [6,7,8]. The high water content and the oxidation state of magmas in these settings lead to mobilizing metals such as Cu partitioned into exsolved hydrothermal fluids and reprecipitated upon cooling to form porphyry Cu deposits [9,10]. Higher oxygen fugacity favors the transport of metals and S from the mantle to shallow crustal levels, the former being an important factor that restricts the formation of porphyry deposits [1,4,6,10].

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