Abylkas Saginov Karaganda Technical University, Karaganda, Republic of Kazakhstan:

M. B. Mynbaev, Doctoral Student
T. V. Kryazheva, Associate Professor, Candidate of Geological and Mineralogical Sciences, kryazheva_t@mail.ru
V. S. Portnov, Professor, Doctor of Engineering Sciences

Zhezkazgan Baikonurov University, Zhezkazgan, Republic of Kazakhstan:

G. Zh. Dosetova, Doctoral Student

The authors investigated mineralogy and petrography of the Devonian volcanic formations in the Zhaksytau caldera in the Western Mugodzhar Mountains with a view to assessing probable ore content of the area. Amongst the volcanic rocks of the caldera, the Mugodzhary series is best developed and composes the uplands of the Mugodzhar Mountains. The relevance of the research is governed by the need to have new data on the formation conditions of pyrite gold and polymetallic mineralization in the late ensimatic island arcs. The basis of the research is the analysis of the material constitution of the volcanic formations. The test area is a part of the south extension of the Tagil–Magnitogorsk depression in the Southern Ural. The petrographic compositions and structures of the Mugodzhary formation rocks are described. Pillow lavas of various morphology types occupy substantial volumes in the Silurian and Devonian cross-section of the Western Mugodzhary, and mostly adjoin certain sites in the cross-section. The composition of magma, which generated the pillow lavas, gradually changed with time from plateau-basalt in the Silurian Period and from andesite–basalt to andesite in the Devonian Period. Different zones of the same lava pillow have different chemistries. The degree of albitization of the pillow lavas is directly proportional to the degree of decrystallization of rocks and, probably, is independent of the formation conditions of the pillow lavas. The pillow lavas contain much more metals than the overburden of the same composition. The pillow lavas should be considered as the favorable host environment for the Cyprus-type pyrite–copper mineralization.

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