Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

< previous | issue |       
 
Received: 22 September, 2015
Accepted: 26 February, 2016
Online: 15 March 2016
H. Editor: K. Schulmann
 
  full text (PDF, 1.91 MB)
 
Export to RIS
Export to BibTeX
Export to Mendeley
 
More articles on Geology of Mongolia
 

Original paper

Viktor Antipin, Ochir Gerel, Alexander Perepelov, Dashdorjgochoo Odgerel, Tsegmed Zolboo

Late Paleozoic and Early Mesozoic rare-metal granites in Central Mongolia and Baikal region: review of geochemistry, possible magma sources and related mineralization

Journal of Geosciences, volume 61 (2016), issue 1, 105 - 125

DOI: http://dx.doi.org/10.3190/jgeosci.211



The Central Asian Orogenic Belt (CAOB) was a scene of intense granitoid magmatism during the Phanerozoic with formation of vast batholiths: Angara-Vitim and Daurian-Khentei. In the Late Paleozoic and Early Mesozoic times, the peripheral zones of batholiths underwent granitic magmatism associated with rare-metal mineralization. Petrological and geochemical studies show that the rare-metal Li-F granites formed, with a gap about 100 My, large igneous provinces of the Mongol-Okhotsk Belt.
Late Paleozoic rare-metal granites build a series of multiphase plutons in the Baikal region (e.g. Kharagul 318 ± 7 Ma, Bitu-Dzhida 311 ± 10 Ma and Urugudei 321 ± 5 Ma). The early medium-grained biotite granites and leucogranites, were followed by topaz-bearing microcline- and amazonite-albite granites and a series of dikes. The Early Mesozoic epoch was marked by the formation of the Daurian-Khentei Batholith (230-190 Ma) in the center of area and rifting zones with alkaline and rare-metal granite plutons on the peripheries. In contrast to the Late Paleozoic, small Early Mesozoic intrusions (e.g., Avdar Pluton ~10 km2, 212-209 Ma) of rare-metal Li-F granites within the Avdar-Khoshutul series of granitoids coexisted with sizable plutons (e.g., Janchivlan Pluton ~70 km2, 227-195.3 Ma). Rare-metal Li-F granites of the Janchivlan Pluton produced small domal intrusions composed of microcline-albite, amazonite-albite and albite-lepidolite granites. The Sn-Ta-Nb mineralization is associated with albite-lepidolite granites.
The rare-metal granites of the Baikal region and central Mongolia of contrasting ages show an identical geochemical signature of Li-F granites. It is expressed by increase in F, Li, Rb, Cs, Sn, Be, Ta and Pb and decrease in Sr, Ba, Zn, Zr, Th and U contents in course of multiphase intrusions formation. The geochemical data confirm the magmatic model for genesis of the studied rare-metal Li-F granites. However this process of magma differentiation was terminated with formation of albitites, microclinites and muscovite greisens. The whole-rock geochemistry and isotopic composition of the granites points to the Precambrian crust of the Baikal region (T2DМ = 1.0-1.3 Ga) as the most likely source. We propose the formation of the initial granitic melts due to anatexis of the higher levels of the continental crust, with fluids released during granulite-facies metamorphism in the lower crust. The rare-metal Li-F granites of the studied provinces are intraplate formations geochemically different from the Early Paleozoic collision granitoids. This could be caused by the influence of deep-seated source on the occurrence of rare-metal magmatism.

Journal of Geosciences, Published by © Czech Geological Society, with support from the Czech Geological Survey.
Webdesign inspired by aTeo. Hosted at the server of the Institute of Petrology and Structural Geology, Charles University, Prague.
ISSN: 1803-1943 (online), 1802-6222 (print)
email: jgeosci(at)jgeosci.org
cover_rotated.gif, 15kB

SNIP (Scopus, 2015): 0.700

IF (ISI, 2015): 1.326

Policy: Open Access

ISSN: 1802-6222

E-ISSN: 1803-1943