Литосфера (Feb 2016)
U-Pb age and Hf-Nd-Sr-Cu-S isotope systematics of the Binyuda and Dyumtaley ore-bearing intrusions (Taimyr, Russia)
Abstract
We present for the first time U-Pb age data and Hf-Nd-Sr-Cu-S isotope signatures for lithologies and associated sulphide ores from the Binyuda and Dyumtaley ultramafic-mafic intrusions located in the limits of the Taimyr Peninsula (Russian Arctic). Zircons are characterized by similar U-Pb ages (245.7 ± 12 Ma at Binyuda and 256.2 ± 0.89 Ma at Dyumtaley), indicating for their close temporal relationship with tholeiite-basalt magmatism of the Siberian Platform. Silicate materials show distinct Hf-Nd-Sr isotope signatures (εHf = -3.8 ± 1.3, ɛNd = -3.8±0.4 and87Sr/86Sri = 0.70588 ± 0.00013 at Binyuda and εHf = 9.5 ± 2.5, ɛNd = 4.2 ± 0.7 and87Sr/86Sri = 0.70474 ± 0.00020 at Dyumtaley). The determined Hf-Nd-Sr variability is interpreted to represent a primary source signature of the lithological units. An important role of the juvenile component is clearly pronounced for the Dyumtaley intrusion, whereas a major contribution from a subcontinental mantle or essentially crustal source is inferred for the Binyuda intrusion. These signatures clearly manifest deviation from those typical of the ore-bearing intrusions from the Noril’sk Province, characterized by protracted magmatic evolution with significant time span of zircon and baddeleyite U-Pb ages (from ca. 350 to 230 Ma), relatively constant εNd values (ca. +1 ± 0.5), highly heterogeneous εHf (from -2.3 to 16.3) and87Sr/86Sri (from 0.70552 to 0.70798). In terms of Cu-isotopes, the majority of the analyzed sulphide samples fall within a tight cluster of δ65Cu values (-0.66 ± 0.24‰ at Binyuda and 0.4 ± 0.1‰ at Dyumtaley), characteristic of the ores from the economic Ni-Cu-PGE deposits at Talnakh. In contrast, notable difference in δ34 S values typifies sulphide ores at Binyuda and Dyumtaley (1.5 ± 0.4 and 11.4 ± 0.6‰ respectively). We suggest that the Cu-S isotope characteristics of the sulphide ores reflect their primary signature rather than a result of mixed sources or magmatic fractionation of stable isotopes. However, the latter possibility cannot be ruled out for heavy S isotope composition of sulphide ore at Dyumtaley. Samples of the disseminated sulphide ore from the Dyumtaley intrusion approach δ34S-δ65Cu parameters of the economic ores at Talnakh (Noril’sk Province) and might be considered as the most prospective for targeting the massive Ni-Cu-PGE sulphide ores.
