Geological characteristics, metallogenesis, and tectonic setting of porphyry–skarn Cu deposits in East Kunlun Orogen

Abstract

The East Kunlun Orogen (EKO), as the west segment of the Central China Orogen, is the most important Triassic polymetallic metallogenic belt in China. In this paper, we summarize the geological characteristics (stratigraphy, structure, ore‐related plutons, wall rock alteration, and orebodies), ore‐forming fluids and materials, geochronology, and petro‐geochemistry of the representative porphyry–skarn Cu–polymetallic deposits, including the Saishitang, Hutouya, and Kaerqueka deposits in the EKO. The porphyry–skarn Cu deposits in the EKO are mainly distributed in tectonic units of the Qimantagh Belt and the Elashan Belt. Among them, the skarn Cu deposits provide the majority of Cu resources, which mainly occur in the contact zone between the Triassic granitoids and the volcanic–sedimentary rocks (e.g., the Ordovician–Silurian Tanjianshan Group and the Early to Middle Triassic Hongshuichuan Group), and the skarn and orebodies are mainly controlled by interlayer–gliding structures. Ore‐forming fluids of the porphyry Cu deposits are magmatic mixed with meteoric water, whereas the fluids of skarn Cu deposits are mainly of magmatic origin. The higher δ18O (>10‰) of garnet and pyroxene in prograde skarn and wide range of sulphur isotopic compositions (δ34S values from −8.9‰ to 11.0‰) suggest that ore‐forming materials of skarn Cu deposits were partially derived from the country rocks. Based on detailed field investigations, we identified four Cu mineralization types, including veinlet–disseminated Cu (Mo, Au) mineralization occurring within the intrusions, proximal skarn Cu (Fe, Pb, Zn, Au) mineralization, distal skarn Cu mineralization, and distal skarn Pb–Zn (Cu) mineralization. The porphyry–skarn Cu deposits are associated with magmatism that occurred mainly during 235–218 Ma. The ore‐related granitoids are mostly calc‐alkaline I‐type granites, derived from partial melting of the Precambrian basement rocks with various degrees of involvement of mantle components. Combined with the regional tectonic evolution, we conclude that the Cu mineralization in the EKO began with the closure of A'nyemaqen Ocean (~238 Ma) and subsequently culminated in a postcollisional setting (~225 Ma).

Origin of the Late Permian gabbros and Middle Triassic granodiorites and their mafic microgranular enclaves from the Eastern Kunlun Orogen Belt: Implications for the subduction of the Palaeo‐Tethys Ocean and continent–continent collision

“…Recent studies show that the Late Triassic granitoids can be divided into calc‐alkaline and alkaline rocks, which have been suggested to be related to post‐collisional setting (Feng et al, ; Wang, Feng, Li, & Li, ; Xiong et al, ; Yao, ; Yu et al, ; Yu et al, ). The Late Triassic Elashan Formation terrestrial volcanic rocks, and the contemporaneous A‐type granites (Gao et al, ; Hu et al, ; Liu, Mo, Yu, Zhang, & Xu, ; Xi et al, ) and mafic–ultramafic rocks (Hu et al, ; Luo, Ke, Cao, Deng, & Chen, ; Ma et al, ; Figure ) suggest a post‐collisional tectonic regime during Late Triassic in the EKOB.…”

Geochronology and Geochemistry of Late Paleozoic Volcanic Rocks and Their Relationship With Iron and Molybdenum Deposits in Xilekuduk Area, Northern Margin of Junggar

“…With the crystallization differentiation of magma and the precipitation of copper element, the high background value of copper in volcanic rocks of the Beitashan Formation is formed. The Cu content of basalt is 95 × 10 −6 -25 × 10 -6 , which is about 4 times of the Clark value of crust and that of andesite is 20 × 10 -6 , which is roughly equivalent to the Clark value of crust, which provides material source for the formation of later copper deposits (Yang et al, 2010). In the Qiaoxiahara iron-copper-gold deposit on the northern side of the study area, iron ore body mainly occurs in the basalt-andesite volcanic rock of the Beitashan Formation of the Middle Devonian, which is derived from the early intermediate-basic volcanism (Ying, 2007).…”

Fluid Inclusions and S–Pb Isotopes of the Reshui Porphyry Mo Deposit in East Kunlun, Qinghai Province, China

“…The mineralization in the EKOB is spatially and temporally related to Triassic granitoids. The EKOB experienced strong crust-mantle interactions during the Triassic [5,6,18,31], among which magma underplating and mixing were predominant, with abundant porphyry and skarn mineralization [9,10]. In this study, we collected data published in the literature regarding porphyry mineralization ages ( Table 3).…”

“…The East Kunlun Orogenic Belt (EKOB) is located along the northern margin of the Tibetan Plateau [1][2][3] and is one of the most important magmatic arcs and polymetallic metallogenic belts in China [4][5][6][7][8]. Many porphyry-skarn deposits have been discovered and explored in this area (e.g., the Kaerqueka Cu-Mo porphyry deposit, Hutouya Cu-Pb-Zn skarn deposit, and Galinge Fe skarn deposit [9][10][11][12][13]). Many publications have focused primarily on the geochemistry of the granite [14][15][16][17][18] and on the description of the geological characteristics of typical deposits and their host rocks [19][20][21].…”