Home – Home – Jornals – Russian Geology and Geophysics 2005 number 5

Granites of the Late Mesozoic Kukul'bei ore-bearing complex in the Aga structure-formational zone of eastern Transbaikalia are studied. It is shown that the concentrations of incompatible trace elements in them are correlated with the domal morphology of the roof of granite intrusive systems of the Kukul'bei complex. Massifs of biotite granites of the major intrusive phase (MIP) are localized in the centers of domes formed in enclosing sand-shaly rocks, and younger ore-bearing leucogranite (usually muscovite) differentiates occur on the flanks of the axial, most uplifted, zones of the domes. The studied granites are highly aluminous and potassic. The MIP granites are enriched in granitophile trace elements, including Sn, W, Be, Ta, and volatiles, which are of plutonic genesis. The enrichment is shown to be of local character: The most enriched granite bodies occur in the axial zones of domes, whereas granites with lower concentrations of trace elements (as low as their clarkes), in the peripheral, least uplifted, zones of the domes. Rare-metal mineralization is localized in leucogranites drastically depleted in Sr and Ba; its productivity is directly correlated with the concentrations of trace elements in the leucogranites.
The granites of intrusive systems of the Kukul'bei complex, localized in deep-fault zones, might be enriched in trace elements (including volatiles F and B) as a result of their supply with mantle fluids. This process led to the formation of crustal granite magma chambers of ore-bearing rare-metal intrusions. Their subsequent evolution during the fluid supply resulted in leucogranite differentiates enriched in trace, ore-forming, and volatile elements, which were the major source of ore-bearing fluids and hydrotherms at the postmagmatic stage.