Geochemistry, isotope triad (Nd-Sr-O), and 40Ar-39Ar age of Paleozoic alkaline mafic intrusions of the Kuznetsk Alatau (by the example of the Belaya Gora pluton)

We report the first data on 40Ar/39Ar dating, trace-element geochemistry, and isotope (Nd, Sr, O) composition of the Belaya Gora gabbro-foidolite-foyaite intrusive massif, one of typical representatives of the alkaline province of the northeastern Kuznetsk Alatau. The established age of rock-forming amphibole, ~ 401-403 Ma, is taken as the time of the pluton formation in the Early Devonian. The distribution and ratios of LILE and HFSE in the rocks suggest that the intrusion took place in the setting of “superposition” of Devonian mantle plume on the Early Paleozoic accretion-collision complexes. Therefore, the source of magmatic products had a heterogeneous composition as a result of mixing of plume material with the substances of suprasubduction and crustal substrates. The mantle component might have been a PREMA + EM combination, which is confirmed by the parameters of the Nd isotope composition (£NdT - 3.2-4.6; TNd(DM) - 0.8 Ga) of alkaline rocks. 87 86 18 The effects of crustal contamination are reflected in the high ratios of strontium and oxygen isotopes ( Sr/ Sr)T - 0.7046-0.7054; 5 O - 8.5-9.2%c, SMOW).