The Paleozoic-Aged University Foidolite-Gabbro Pluton of the Northeastern Part of the Kuznetsk Alatau Ridge, Siberia: Geochemical Characterization, Geochronology, Petrography and Geophysical Indication of Potential High-Grade Nepheline Ore

Abstract

Geological, geochemical and ground magnetic techniques are used to characterize the University alkaline-gabbroid pluton and crosscutting N-S trending alkaline dikes, located northeast of the Kuznetsk Alatau ridge, Siberia. Trace element concentrations and isotopic compositions of the igneous units were determined by XRF, ICP-MS and isotope analysis. The Sm-Nd age of subalkaline (melanogabbro, leucogabbro 494–491 Ma) intrusive phases and crosscutting alkaline dikes (plagioclase ijolite, analcime syenite 392–389 Ma) suggests two stages of activity, likely representing separate events. The subalkaline and alkaline rocks are characterized by low silicic acidity (SiO2 = 41–49 wt %), wide variations in alkalinity (Na2O + K2O = 3–19 wt %; Na2O/K2O = 1.2–7.2 wt %), high alumina content (Al2O3 = 15–28 wt %) and low titanium content (TiO2 = 0.07–1.59 wt %). The new trace element data for subalkaline rocks (∑REE 69–280 ppm; La/Yb 3.7–10.2) of the University pluton and also the crosscutting younger (390 Ma) alkaline dikes (∑REE 10–1567 ppm; La/Yb 0.7–17.8 ppm) both reflect an intermediate position between oceanic island basalts (OIBs) and island arc basalts (IABs). The presence of a negative Nb–Ta anomaly and the relative enrichment in Rb, Ba, Sr, and U indicate a probable interaction of mantle plume material with the lithospheric mantle beneath previously formed accretion complexes of subduction zones. The isotopic signatures of strontium (εSr(T) +3.13–+28.31) and neodymium (εNd(T) +3.2–+8.7) demonstrate the evolution of parental magmas from a plume source from moderately depleted PREMA mantle, whose derivatives underwent selective crustal contamination.

Editorial for Special Issue “Ore Genesis and Metamorphism: Geochemistry, Mineralogy, and Isotopes”

“…The successful synthesis of geological-petrographic, isotope-geochemical and geophysical methods is described in the article by Mustafaev et al [6]. This paper provides a consistent view at the formation of the University Foidolite-Gabbro Pluton (Kuznetsk Alatau Ridge, Siberia) and a potential source of its nepheline ores.…”

Early Triassic Episode of the Kresty Volcano–Plutonic Complex Formation in the Maymecha-Kotuy Alkaline Province, Polar Siberia: Geochemistry, Petrology and Uranium–Lead Geochronology

“…One of the variants of such genesis may be the interaction with the carbonate substrates of the Siberian craton, which these objects are localized in [26]. Quite often such examples are observed for folded areas of alkaline magmatism [6,27,28].…”

Evolution of Syenite Magmas: Insights from the Geology, Geochemistry and O-Nd Isotopic Characteristics of the Ordovician Saibar Intrusion, Altai-Sayan Area, Russia

“…Within the Saibar intrusion, there are no mafic rocks with a SiO2 content of 52 wt.% that preceded or accompanied the formation of syenites. This limits the po of reconstructing the composition of magmas that was parental for the syenitic r the same time, the other syenite-bearing intrusions of the Altai-Sayan fold belt mafic rocks formed synchronously with examined syenites, which indicates the spondence to the composition of parent magmas [32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Accordingly, the geolo finity of the Saibar intrusion to other similar intrusions suggests a genetic conne tween its rocks and the mafic magmas, which occurred at levels of the magmati inaccessible to observation.…”

“…This part of the CAOB covers the sizable Altay-Sayan fold belt, where alkaline magmatism produced the syenites typical of Kuznetsk Alatau and southeast of Tuva in the Eastern Sayan Mountains and Sangilen Highland, as well as in the Minusinsk Trough subdividing these territories. Alkaline magmatism proceeded several times throughout the Paleozoic epoch in the Early Paleozoic (510-450 Ma), Devonian (410-390 Ma), and Late Carboniferous and Early Permian (305-280 Ma) [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. [47,48].…”