Geology, geochronology and geochemistry of large Duobaoshan Cu–Mo–Au orefield in NE China: Magma genesis and regional tectonic implications

• Published in: Di xue qian yuan. 2021-01, Vol.12 (1), p.265-292
• Main Authors: Cai, Wen-yan, Wang, Ke-yong, Li, Jian, Fu, Li-juan, Lai, Chun-kit, Liu, Han-lun
• Format: Article
• Language: English
• Subjects: Central Asian Orogenic Belt (CAOB); Duobaoshan Cu–Mo–Au orefield (NE China); Epithermal Au deposit; Paleo-Asian Ocean; Porphyry Cu deposit
• ISSN: 1674-9871
• DOI: 10.1016/j.gsf.2020.04.013

Duobaoshan is the largest porphyry-related Cu–Mo–Au orefield in northeastern (NE) Asia, and hosts a number of large-medium porphyry Cu (PCDs), epithermal Au and Fe–Cu skarn deposits. Formation ages of these deposits, from the oldest (Ordovician) to youngest (Jurassic), have spanned across over 300 ​Ma. No similar orefields of such size and geological complexity are found in NE Asia, which reflects its metallogenic uniqueness in forming and preserving porphyry-related deposits. In this study, we explore the actual number and timing of magmatic/mineralization phases, their respective magma genesis, fertility, and regional tectonic connection, together with the preservation of PCDs. We present new data on the magmatic/mineralization ages (LA–ICP–MS zircon U–Pb, pyrite and molybdenite Re–Os dating), whole-rock geochemistry, and zircon trace element compositions on four representative deposits in the Duobaoshan orefield, i.e., Duobaoshan PCD, Tongshan PCD, Sankuanggou Fe–Cu skarn, and Zhengguang epithermal Au deposits, and compiled published ones from these and other mineral occurrences in the orefield. In terms of geochronology, we have newly summarized seven magmatic phases in the orefield: (1) Middle–Late Cambrian (506–491 ​Ma), (2) Early and Middle Ordovician (485–471 ​Ma and ~462 ​Ma), (3) Late Ordovician (450–447 ​Ma), (4) Early Carboniferous and Late-Carboniferous to Early Permian (351–345 and 323–291 ​Ma), (5) Middle–Late Triassic (244–223 ​Ma), (6) Early–Middle and Late Jurassic (178–168 ​Ma and ~150 ​Ma), and (7) Early Cretaceous (~112 ​Ma). Three of these seven major magmatic phases were coeval with ore formation, including (1) Early Ordovician (485–473 ​Ma) porphyry-type Cu–Mo-(Au), (2) Early–Middle Triassic (246–229 ​Ma) porphyry-related epithermal Au-(Cu–Mo), and (3) Early Jurassic (177–173 ​Ma) Fe–Cu skarn mineralization. Some deposits in the orefield, notably Tongshan and Zhengguang, were likely formed by more than one mineralization events. In terms of geochemistry, ore-causative granitoids in the orefield exhibit adakite-like or adakite-normal arc transitional signatures, but those forming the porphyry-/epithermal-type Cu–Mo–Au mineralization are largely confined to the former. The varying but high Sr/Y, Sm/Yb and La/Yb ratios suggest that the ore-forming magmas were mainly crustal sourced and formed at different depths (clinopyroxene-/amphibole-/garnet-stability fields). The adakite-like suites may have formed by partial melting of the thicke