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EARLY
AND LATE COLLISIONAL GRANITOID BATHOLITHS OF THE URALS: CONDITIONS
OF LOCATION, GEOCHEMICAL AND METALLOGENE SPECIALIZATION AND
PRACTICAL
SIGNIFICANCE
Ogorodnikov V.N.*,
Sazonov V.N.**, Polenov Yu.A.*
*Urals State Mining
University, Ekaterenburg, Russia
**Institute of Geology and
Geochemistry UrB RAS, Ekaterinburg, Russia, Sazonov@igg.uran.ru
Collision
granitoids of the Urals are divided into two groups: of early
(380-290) and late (290-240 Ma) collision (Gold…, 2001;
Fershtater et al., 2007; Kholodnov, 2007). The first group is
represented by quartz diorites,
granodiorites, adamellites, granites and the second one – by
biotite (normal) and leucogranites (Fershtater et al., 2007;
Kholodnov, 2007). Both groups localize within: a) suture zones, b)
areas of suture zones cross section and conjugation of suture zones
with the faults of NW orientation, c) the Main granite axis of the
Urals (there are some massifs located to the W from the Main suture
zones). In the Urals granitoid batholiths are located in such
domains, where depth to the basalt strata is 21,5 km and thickness
of the latter is 30,6 km.
There
are many dykes (from acidic to basic composition) in the Uralian
granitoid batholiths. Composition
of dykes is predetermined by poly-step anatexis on the basite
(gabbro) base and crystallization differentiation (Gold…,
2001; Fershtater et al., 2007; Kholodnov, 2007). More late
granitoids accompanied more acidic dyke complexes. This was a reason
for the following relations which everyone can see in the Shartash
granite batholith (Central Urals): pegmatites cross lamprophyres,
from the one hand and lamprophires cross pegmatites from the other
hand. Multiphase granite massifs and associated mineralization can
reach 60 to 100 Ma (Gold…, 2001; Fershtater et al., 2007).
Early
collisional granitoids are specialized on Au and W (see
Korobeynikov, Mironov, 1992; Gold…, 2001; Fershtater et al.,
2007). As a rule, there is more gold in more basic granitoides. The
dyke complexes are more auric then host granitoids. Dyke complexes
are considered as a fluid leader (Korobeynikov, Mironov, 1992;
Gold…, 2001). In apogranitoid fluid, the ratio F: Cl: S
(perhaps, CO2)
is such that it is quite sufficient for Au extract, but that of
chalkhophile elements and Fe is impossible in these conditions
(Kholodnov, 2007).
Late collisional granites
specialized on F (instead of Cl), their clark value being small
(less then 2 mg/t).
Most
gold deposits of quartz-veined type are conjugated with
beresite-listvenite formation. Its metasomatites
are formed at high activity of CO2,
low
concentration of Cl and relatively high F in the fluid. During the
process of beresitization-listvenitization, F is concentrated in
muscovite, so content of F in the fluid increases, Cl takes part in
Au transport that is proved by presence of this element and its
combinations in gold nuggets.
Hydroxide
minerals of late collisional granites are poor in Cl (0,0-0,05
wt.%). But they are rich in F: in apatites 4,0, biotites - 1,5 wt.%
and more (Sazonov et al., 2005). Contents of F and K, Be, Ta, Nb,
Li, Rb, Cs in late collisional granites are correlated. Activity of
F in an apogranite fluid essentially predetermines compositions
of rare metal (Be, Ta, Nb, Li, Rb, Cs) and W and W-Mo
mineralizations.
Thus fluid specialization of
collisional granitoids is important criterion of their magmatic
specialization and potential ore-bearing. It is predetermined by:
source of melt generation (mantle, crust), nature of substrate and
geodynamic regime. A fluid specialization (F and Cl for example) is
characteristic for all parts of ore-magmatic system - magmatites,
ore bodies and associated metasomatites. Thus, fluid specialization
is a base for formational analyses of magmatites, associated
metasomatites and metallogeny (Korobeynikov, Mironov 1992; Koroteev,
Sazonov, 2005; Gold…, 2001; Kholodnov, 2007).
References
Fershtater G.B.,
Kholodnov V.V., Borodina N.S. Magmatic complexes of the Urals
controlling the goldmineralization
// Rudogenes. Miass, 2007. P.320-322.
Gold deposits of the Urals/Sazonov V.N., Ogorodnikov V.N., Koroteev V.A. et al., Ekaterinburg, 2001. 622p.
Korobeynikov A.F., Mironov A.G. Geochemistry of gold in
endogenic processes, and conditions of gold deposits formation.
Novosibirsk: Nauka, 1992. 217p.
Kholodnov V.V. Halogens
(F, Cl) – indicators of supra subduction granitoid
specialization of tanolite-granodiorite formation for
gold-sulfide-quartz mineralization // Geodynamics, magmatism,
metamorphism and ore formation. Ekaterinburg,
2007. P.856-889.
Koroteev V.A., Sazonov V.N. Geodynamics, ore genesis and prognosis. Ekaterinburg, 2005.
285p.
Sazonov V.N.,
Ogorodnikov V.N., Polenov Yu.A. Correlation between volatiles (F,
Cl, CO2,
S) and some ore forming elements in ore formations of the Urals and
their productive rock complexes // Urals mineralogy school –
2005. Ekaterinburg, 2005.
P.54-64
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