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The recently discovered Jinkeng deposit, located in eastern Guangdong Province, SE China, is a granite-related cassiterite–sulfide-type Sn–Cu–Pb–Zn deposit in the Cathaysia Block. Zircon U–Pb dating of the biotite granite and fine-grained granite associated with the deposit yielded concordant ages of 144.7 ± 0.8 Ma and 141.1 ± 1.3 Ma, respectively. These ages are consistent, within error, with the molybdenite Re–Os isochron age of 139.3 ± 2.5 Ma for the deposit, indicating a temporal link between the emplacement of granitic plutons and polymetallic Sn mineralization. Combined with the regional mineralization ages, we propose that the 145–135 Ma interval represents another significant period of Sn–W mineralization in southern China, in addition to those already recognized. The biotite granite and fine-grained granite have similar geochemical characteristics; both are weakly peraluminous, high-K and calc-alkaline, containing abundant Si, Na, and K, and low concentrations of Fe, Mg, Ca, and P. Compared to primitive mantle and unfractionated granitoids, they are enriched in Rb, Th, U, K, and Pb, have relatively high Rb/Sr and low K/Rb values, are depleted in Ba, Sr, and Ti, and have prominent negative Eu anomalies (δEu = 0.05–0.19), characteristic of highly fractionated I-type granites. Zircons from these granites have ε Hf (t) values ranging from − 9.2 to − 3.3, and Hf model ages (T DM2 ) of 1776–1406 Ma, suggesting that the granites formed by the partial melting of Proterozoic basement material, and contain a minor mantle-derived component. Highly fractionated and reduced ( f O 2 below NNO) magma facilitated the enrichment of Sn. Existing knowledge on the tectonic evolution of this region and new data from this study, indicate that the granites and associated Sn mineralization in the Jinkeng deposit formed in an extensional environment at ~ 140 Ma, likely related to the rollback of the paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

The newly discovered Dadaoshan Sn deposit is located in the eastern Guangdong Sn–W province, coastal SE China. The Sn mineralization, hosted in Jurassic porphyritic granite and the Lower Jurassic Jinji Formation sedimentary wall rocks, is considered to be granite-related. In this study, the porphyritic granite was LA–ICP–MS zircon U–Pb dated to be 153.2 ± 1.2 Ma, consistent with the syn -mineralization molybdenite Re–Os age of 152.6 ± 1.8 Ma. The porphyritic granite samples are weakly peraluminous (A/CNK = 1.0–1.1) and high-K calc-alkaline. The rocks contain high SiO 2 (72.9–75.6 wt%), moderate Rb/Sr (5–9) and low ΣREE (136–223 ppm). They are enriched in F, Li, Rb and Sn, depleted in Ba, Sr, P, Zr, Th, Nb and Y, and have distinct negative Eu anomalies (δEu = 0.09–0.18), suggesting that the porphyritic granite is highly fractionated I-type granite. The calculated initial 87 Sr/ 86 Sr (0.711582–0.715173), relatively low ɛ Nd (t) (−9.48 to −8.54; T DM2 = 1638–1814 Ma), and the zircon ε Hf (t) (−14.2 to −5.1; two-stage model ages = 1528–2103 Ma) all suggest that the granite was mainly crustal-derived with little mantle input. Sulfur isotopic compositions for the sulfides (arsenopyrite and chalcopyrite: δ 34 S = −1.1 to 1.4‰, average = −0.1) imply a dominantly magmatic sulfur source. The calculated zircon Ce 4+ /Ce 3+ and Eu N /Eu N ∗ ratios of the Dadaoshan granite range from 1.0 to 112 (mean = 31.7) and from 0.04 to 0.37 (mean = 0.14), respectively, indicating a low oxygen fugacity for the magma. The reducing and highly fractionated nature of the Dadaoshan granitic magma may have played a key role in the Sn mineralization. It was previously argued that the Jurassic Sn–W mineralization and its causative magmatism were largely confined in the South China interior, e.g., the Nanling Range. Our new data suggest that the Late Jurassic Sn–W mineralization and its causative magmatism actually extended to the SE China coastal area. The Dadaoshan granite may have been generated from partial crustal melting led by underplating of mantle-derived magmas in an extensional environment. Regional extension may have been related to the west-directed, flat-slab subduction and delamination of the Paleo-Pacific (Izanagi) plate beneath the South China block. Another suite of Early Cretaceous Sn–W-bearing granitic rocks in eastern Guangdong may have mainly been crustal-derived with minor mantle input, and likely occurred under back-arc extensional setting led by the Paleo-Pacific subduction rollback. [ABSTRACT FROM AUTHOR]