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Geochemical characteristics of the Shujiadian Cu deposit related intrusion in Tongling: Petrogenesis and implications for the formation of porphyry Cu systems in the Middle-Lower Yangtze River Valley metallogenic belt, eastern China
journal contribution
posted on 2023-05-19, 02:54 authored by Wang, S, Zhou, T, Yuan, F, Fan, Y, David CookeDavid Cooke, Lejun ZhangLejun Zhang, Fu, B, Noel WhiteNoel WhitePorphyry Cu deposits can form in intracontinental or post-collision settings; however, both the genesis of fertile magmas and the mechanism of metal enrichment remain controversial. The Shujiadian porphyry Cu deposit is located in the Tongling area of the Middle–Lower Yangtze River Valley metallogenic belt. It is hosted by the Shujiadian complex, which mainly consists of quartz diorite porphyry (143.7 ± 1.7 Ma) and pyroxene diorite (139.8 ± 1.6 Ma). They both belong to the calc-alkaline series, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in high field-strength elements (HFSE) and heavy rare earth elements (HREE), and slightly negative Eu anomalies. Both quartz diorite porphyry and pyroxene diorite have geochemical affinities with adakite, and their low MgO (1.5–3.7 wt%), and Ni (3.7–6.9 ppm), Cr (2.0–44 ppm), and Th/Ce contents (0.06–0.11) indicate that the intrusive rocks have some characteristics of adakite-like rocks derived from thickened lower crust and melts from metabasaltic rocks and eclogites. Plagioclases from the quartz diorite porphyry are andesine (An value = 31.8–40.5) and from the pyroxene diorite are felsic albite and oligoclase with large-scale zones and variable An value (An value = 8.9–18.3), Fe and Sr contents, which indicate that mixing of mafic and felsic magma may have occurred in the shallow magma chamber. Compared to the barren quartz diorite porphyry, relatively lower SiO2 contents (49.5–55.2 wt.%), higher εNd(t) values (− 7.4 to − 6.9), εHf(t) values (− 11.0 to − 9.1) compositions, Ti-in-zircon temperatures (714–785 °C), and variations of HREE contents of the mineralization-related pyroxene diorite suggest mixing with high-temperature mafic magma. Calculated Ce4 +/Ce3 + values of pyroxene diorite plot between the Ni–NiO buffer (NNO) and magnetite–hematite buffer (MH), and barren quartz diorite porphyry samples plot below the Ni–NiO buffer (NNO). Geochemical features of relatively enriched LILEs, depleted HFSEs, and markedly negative Nb–Ta anomalies, imply that the mafic magma was generated by partial melting of enriched lithospheric mantle, which had been metasomatized by slab-derived fluids from Neoproterozoic-subducted oceanic lithosphere; as a result, the parental magma was rich in H2O, S, and metals (e.g. Cu), with high fO2.
Funding
Australian Research Council
AMIRA International Ltd
ARC C of E Industry Partner $ to be allocated
Anglo American Exploration Philippines Inc
AngloGold Ashanti Australia Limited
Australian National University
BHP Billiton Ltd
Barrick (Australia Pacific) PTY Limited
CSIRO Earth Science & Resource Engineering
Mineral Resources Tasmania
Minerals Council of Australia
Newcrest Mining Limited
Newmont Australia Ltd
Oz Minerals Australia Limited
Rio Tinto Exploration
St Barbara Limited
Teck Cominco Limited
University of Melbourne
University of Queensland
Zinifex Australia Ltd
History
Publication title
LithosVolume
252-253Pagination
185-199ISSN
0024-4937Department/School
School of Natural SciencesPublisher
Elsevier BVPlace of publication
NetherlandsRights statement
Copyright 2016 Elsevier B.V.Repository Status
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