Geochemical relation of an accessory and ore mineralization in ore-magmatic systems with lithium-fluoric granites of the Far East
National university of mineral resources «Mining», Saint-Petersburg, Russia
The ore-magmatic systems (OMS) of the Far East largest tungsten-tin deposits (Pyrkakayskoye, Odinokoye, Kesterskoye, Olonoyskoye, Pravourmiyskoye, Tigrinoye et al.) include Late Cretaceous plutonic series with late lithium-fluoric granites. TheOMS are components sedimentary and volcanogenic series of passive continental margin and accretion zones generated and processed in a course of the Yanshanian, Verkhoyanian and Laramide orogeny. Granitoid magmatism develops in the crust chamber structures and ends in a formation of the multistage granite domes topped with complexes of rare metal granites and greisens (Rub et al., 1982; Romanovskiy, 1999; Gonevchuk, 2002; Geodinamika..., 2006; Mitrofanov, 2007). The major metallogenic feature of the OMS with lithium-fluoric granites of the Pacific ore belt (POB) - weak denudation and exposure on the modern surface of the top stage including various nonindustrial accessory mineralization of additional and veined phases of plumasite granites, ongonites and the richest industrial mineralization of zwitters and tourmalinites (Tomson, Tananayeva, 1989; Gonevchuk, 2002; Alekseev, 1989; 2011; 2013).
Studying of the granitoid accessory minerals by means of EMPA and SIMS has shown an extreme variety of their species composition and isomorphic components. Tungsten, yttric, tantalum-niobic, ceric, titanic and uranium-thorium accessory minerals complexes are classified. The main evolution tendency of rare metal mineralization of the ore-bearing intrusive series is established: progressive accumulation of rare elements among biotite leucogranites – monzogranites – rare metal granites – zwitters. Along with this a directed change from the titan-niobium-tungsten and ytterbium-yttric mineralization to the niobium-tantalic and lantan-ceric. Precision research of lithium-fluoric granites has shown that cassiterite often mentioned in papers of the XX century as typical accessory mineral of the Pacific tin-bearing granites is not characteristic of such rocks. The only exception is cassiterite of the greisenized granites. Among the primary accessory minerals of other ore elements typical of an external zone of the Pacific ore belt - Mo, As, Cu, Pb, Zn, Ag, In are not established. Only tungsten, the main ore element of the Asian POB segment, forms common in lithium-fluoric granites minerals – ferberite, âîëüôðàìîèêñèîëèò and tungsten-containing accessories (rutile, ilmenite, fergusonite-(Y), ishikawaite, calciosamarskite, samarskite-(Yb), aeschynite-(Y), struverite, liandratite, russellite). The wide spread of tungsten and tungsten-containing accessory minerals is a newly established regional feature of rare-metal granites in the Far East.
A comparative analysis of accessory and ore mineralization has shown, that postmagmatic minerals inherit rare-metal composition of accessories, but the leading role shifts from the main components (W, Nb, Y, REE) to the minor, which were a part of magmatic minerals in form of isomorphic and crystal impurities (Sn, As, Cu, Bi, Pb, U). As a result of the OMS postmagmatic evolution an association of mixed chalcophylic (cassiterite, stannite, arsenopyrite, chalcopyrite et al.) and lithophylic (ferberite, wolframoixiolite, monazite, allanite et al.) ore minerals is formed (table). The conclusion from this follows: the composition of hydrothermal ore mineralization is defined by geochemical potential of lithium-fluoric granites.
Thus, basic metallogenic feature of the Pacific ore belt is established: tungsten-tin and accompanying ore mineralization is a product of geochemical evolution of the ore-magmatic systems with lithium-fluoric granites. It demands a specification of metallogenic prospects in the tungsten-tin-ore provinces and outlined ore knots of the Russian East and allows to use established accessory complexes as indicators of the Pacific rare metal magmatism.
Researches are executed at financial support of the Russian Federal Property Fund (the grant 11-05-00868-à).
Table. Ore elements mineralogy of the OMS with lithium-fluoric granites from the Far East
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