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Geochronological, geochemical, and Nd–Hf isotopic constraints on the origin of magmatism in the Dabaoshan ore district of South China
Author(s) -
Lei Wang,
Xinbiao Jin,
Deming Xu,
Jinhui Cai,
Yaowu Wang
Publication year - 2018
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3248
Subject(s) - geology , zircon , geochemistry , orogeny , magmatism , intraplate earthquake , partial melting , basalt , subduction , continental arc , geochronology , mantle (geology) , petrology , volcanic rock , tectonics , paleontology , volcano
SHRIMP and LA–ICP–MS zircon U–Pb dating, Nd and Hf isotope analyses, 40 Ar/ 39 Ar geochronology, and whole‐rock geochemistry indicate three episodes of magmatism in the Dabaoshan ore district, South China: (1) Caledonian dacites (ca. 438 Ma); (2) Indosinian dolerites (ca. 210 Ma); and (3) Yanshanian granodiorites/porphyries (ca. 165 Ma) and basalts (ca. 147 Ma). Episode 1 dacites and episode 3 granodiorites/porphyries are enriched in Rb, Th, U, and LREEs and depleted in Nb, Ta, Sr, P, and Ti. The dacites may have been derived from partial melting of Mesoproterozoic–Paleoproterozoic crustal material, whereas the granodiorites/porphyries were derived mainly from partial melting of a late Mesoproterozoic crustal source with minor inputs of mantle material, according to whole‐rock ε Nd (t) and zircon ε Hf (t) values. The geochemical characteristics of episode 2 dolerites and episode 3 basalts, as well as their positive ε Nd (t) values (3.3–5.9 and 3.5–4.0, respectively), suggest a depleted mantle source. Taking into account the tectonic evolution of the South China Block, we suggest episode 1 dacites and episode 2 dolerites formed in an extensional setting that resulted from lithospheric delamination during the Caledonian intraplate orogeny and orogenic collapse during the Indosinian intraplate orogeny. Episode 3 granodiorites/porphyries and basalts formed in a back‐arc extensional setting in response to the westwards subduction of the Palaeo‐Pacific Plate beneath the South China Block. The timing of the three episodes of magmatism coincides roughly with the published ages of mineralization in the Dabaoshan ore district, suggesting a genetic relationship.