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Abstract

Porphyry Cu deposits in China contain a total resource of ~47 million tonnes (Mt) Cu at average grades rangingmostly from 0.2 to 0.7% Cu (most Approximately 50% of the giant and ~35% of the intermediate porphyry Cu deposits in China formed in arcsettings. The Xiongcun, Pulang, Duobuza, Bolong, and Naruo deposits in Tibet formed in continental arc settings, and the Central Asian porphyry Cu belt deposits (e.g., Tuwu-Yandong, Duobaoshan, Wushan, Baogutu,and Bainaimiao) formed in island-arc settings. Ore-forming porphyry magmas in arc settings in China probablyformed by partial melting of metasomatized mantle wedge. Ascent and emplacement of porphyry magmasin arc settings was controlled by transpressional (e.g., strike-slip fault systems) or compressional deformation(e.g., arc-parallel thrust fault systems). Approximately 40% of the giant and ~65% of the intermediate porphyryCu deposits in China occur in postcollisional settings. These deposits are mainly concentrated in the TibetanPlateau, including four giant (e.g., Qulong, Jiama, Zhunuo, and Yulong) and more than 15 intermediate-sizedeposits. The mineralized intrusions in postcollisional settings were generated by partial melting of subduction-modified mafic lower crust. Ore-forming metals and sulfur were derived from remelting of sulfide phasesthat were introduced during precollisional arc magmatism, and the water in the Cu-forming porphyry magmaswas concentrated during dehydration reactions in the upper parts of the subducting continental plate and/ordegassing of mantle-derived H2O-rich ultrapotassic and/or alkaline mafic magmas. Porphyry magma ascent andemplacement were controlled by regional shear zones (e.g., strike-slip fault systems) or extensional fracturearrays (e.g., normal fault systems) in postcollisional settings.Porphyry Cu deposits in China mostly show typical alteration zoning from inner potassic to outer propyliticzones, with variable phyllic and argillic overprints. Potassic alteration can be generally subdivided into innerK-feldspar and outer biotite zones, with K-feldspar–rich alteration mostly earlier than biotite-rich alteration.Phyllic alteration generally comprises early-stage chlorite-sericite and late-stage quartz-sericite alteration, andthe chlorite-sericite zone typically occurs beneath the quartz-sericite zone. Lithocaps are absent in most of theporphyry Cu deposits in China, even for those in the youngest (~30–14 Ma) ores in the Gangdese belt. Alterationarchitecture of the porphyry Cu deposits in China is mainly dependent on the structural setting and degree oftelescoping. Telescoping of alteration assemblages in the postcollisional porphyry Cu deposits is more stronglydeveloped than that in island and continental arc porphyry Cu de posits. This is probably because postcollisionalporphyry Cu deposits and districts in China either experienced higher rates of synmineralization uplift or suffered more complex structural superposition, compared with those formed in magmatic arcs. Hypogene Cumineralization in some giant porphyry deposits in China (e.g., Xiongcun, Qulong) is associated with potassicalteration and particularly with late-stage biotite alteration. But hypogene mineralization for more than 50%of giant porphyry Cu deposits, including the Dexing, Yulong, Tuwu-Yandong, Duobaoshan, and Tongkuangyudeposits, is characterized by a Cu sulfide assemblage with phyllic alteration, particularly with chlorite-sericitealteration. The presence of several world-class postcollisional porphyry Cu provinces in China demonstratesthat the generation of porphyry Cu deposits does not always require a direct link to oceanic plate subduction.

Item Type:	Book Section
Authors/Creators:	Yang, ZM and Cooke, DR
Keywords:	porphyry, copper, gold, China
Publisher:	Society of Economic Geologists, Special Publication
DOI / ID Number:	https://doi.org/10.5382/SP.22.05
Copyright Information:	Copyright 2019 Society of Economic Geologists, Inc.
Related URLs:	UTAS Profile: Cooke, DR
Item Statistics:	View statistics for this item

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