The minor intrusions of the Edel’veis alkaline–carbonatite complex are bounded by the spurs of the North Chuya Ridge in southeastern Gorny Altai. According to Ar–Ar isotope data, the complex formed in the Middle Cambrian (∼507 Ma). All of its components (alkali clinopyroxenite–melanogabbro–alkali syenite + Ca-carbonatite) occur in only one pluton. Silicate igneous rocks are equivalent in silica content and alkalinity to potassic alkaline and subalkalic mafic rocks. Apatite-phlogopitic Ca-carbonatites are enriched in P2O5 (up to 3.6 wt.%), Sr (∼2500–5500 ppm), and REE (up to ∼2000 ppm) and are, presumably, of liquation genesis. A PREMA-type plume component was a predominant magma source for the complex (ɛNd(T) = +6.56 to +6.85). According to isotope data (87Sr/86Sr(T) ∼ 0.7032–0.7039; δ18O ∼ 7.5–14.9‰; δ13C ∼ –2.7 to –8.4‰), the fractionation of the melts was accompanied by their crustal contamination. The trace-element composition of the rocks suggests that the complex developed on a continental margin and its development was accompanied by late-collisional rifting and the mixing of moderately depleted (PREMA) and enriched suprasubductional lithospheric mantle (EM I or EM II) with continental crust. It is presumed that the alkaline and carbonatite complexes in the western Central Asian Fold Belt are of primary plume origin and form a LIP within this belt together with other associations produced by Early Paleozoic (510–470 Ma) magmatism.
A U–Pb isotope analysis has revealed zircons, dated at ~ 510–490 and ~ 430–400 Ma, in granitoid intrusions on the eastern slope of the Kuznetsk Alatau Range (Batenev Ridge). This suggests two stages of the regional granitoid magmatism: Middle–Late Cambrian and Silurian–Early Devonian. The ages of two zircon grains from the rocks of the Tigertysh pluton are ~ 1.9 and ~ 2.6 Ga; they suggest the involvement of fragments of the Paleoproterozoic continental crust in magma generation. The granitoids, independently of their age, are mostly products of rocks of the calc-alkalic (K2O/Na2O ≈ 0.5–1.7) series. In the proportions of alumina, calcium, and alkalies most of them correspond to I-type granites (A/CNK≤1.1) with reduced Fe/(Fe + Mg) values and contents of HFSE, including REE (ΣREE ≈ 100–300 ppm). The trace-element patterns of the rocks point to the possible participation of both IAB and OIB in magma genesis. Presumably, the influence of the within-plate component increased as a result of the superposition of plume on accretion–collisional structures, and their melting might have favored the preservation of geochemical features of subduction magmatism in the granitoids. The isotopic inhomogeneity (εNd(T) = 2.3–4.8, (87Sr/86Sr)T ≈ 0.7036–0.7051) of the granitoid complexes suggests the heterogeneous composition of the material sources, which consisted of the matter of moderately depleted (PREMA) and enriched (EM) lithospheric mantle and crustal substrate, mixed in different proportions. Some products of the regional alkali-basic magmatism are coeval with the Cambrian granitoids of the Kuznetsk Alatau and are similar to them in isotope composition. This magmatism confirms the interaction of plume with the active continental margin at the Caledonian stage of evolution of the Central Asian Fold Belt.
Small intrusions of lamprophyres and lamproites (Chuya complex) and K-monzonitoids (Tarkhata and Terandzhik complexes) are widespread in southeastern Gorny Altai. Geochronological (U–Pb and Ar–Ar) isotope studies show their formation in the Early–Middle Triassic (~ 234–250 Ma). Lamproites have been revealed within two magmatic areas and correspond in geochemical parameters to the classical Mediterranean and Tibet orogenic lamproites. According to isotope data ((87Sr/86Sr)T = 0.70850–0.70891, (143Nd/144Nd)T = 0.512157–0.512196, 206Pb/204Pb = 17.95–18.05) and Th/La and Sm/La values, the Chuya lamproites and lamprophyres melted out from the enriched lithospheric mantle with the participation of DM, EM1, EM2, and SALATHO. The monzonitoid series of the Tarkhata and Terandzhik complexes are similar in petrographic and geochemical compositions but differ significantly in Sr–Nd isotope composition: The Tarkhata monzonitoids are close to the Chuya lamproites, whereas the Terandzhik ones show a higher portion of DM ((87Sr/86Sr)T = 0.70434–0.70497, (143Nd/144Nd)T = 0.512463–0.512487) in their source, which suggests its shallower depth of occurrence and the higher degree of its partial melting as compared with the derivates of the Chuya and Tarkhata complexes. The studied rock associations tentatively formed in the postcollisional setting under the impact of the Siberian superplume.
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