PETROLOGY AND ORE MINERALIZATION OF METABASITES OF THE TERNOVKA SYNCLINE (MIDDLE FOREDNIEPREAN)

Velikanov Y.F., Velikanova O.Y.

M.P. Semenenko Institute of geochemistry, mineralogy and ore formation of NAS of Ukraine, Kyiv, Ukraine, olgavelikanova1@rambler.ru

 

The Ternovka Syncline is extended northwestward in the western part of the Devladovo regional fault zone. The Syncline is composed by metabasic-ultrabasic formation consisting of metabasite strata containing five bed-like bodies of ultrabasites. Metabasites are mostly granoblastic, but in the southern limb of the syncline they are amigdaloid.

The southern limb of the Syncline comprises medium-crystalline hornblende amphibolites and amphibolite schists, whereas the northern limb is represented by fine- to medium-crystalline amphibolites often altered by late metamorphic processes.  Amphibolites are differently granitized but the granitization rate rises northward.

Amphibolites are dark-grey colored with greenish tint, have massive or schistose textures and consist of (wt %): blue-green hornblende (40-50), plagioclase (20-40), quartz (10-15); secondary minerals: biotite, carbonate, actinolite, tremolite, chlorite, sericite; accessories: apatite, titanite, zircon, epidote; ore minerals: magnetite, pyrite, pyrrhotite, chalcopyrite atc.

Ternary diagram CaO-MgO-Al₂O₃ demonstrates intermediate contents of calcium, alumina and magnesium. ACFM diagram classifies the metabasites as subalkaline-aluminous basic rocks. In petrochemical diagrams, the metabasites covers the fields of basaltic komatiites.

Geochemical characteristics of the rocks and minerals were investigated using chemical, spectral and EPMA analytical data.

The highest concentrations (wt %) in the metabasites were detected for  Li and Co – 0.01; Sc – 0.02; Rb and Sr – 0.03; Ba – 0.08; Y, V and Zn – 0.1; Zr and Cu – 0.2; Cr and Ni – 0.3; Mn and P – 0.5; Ti – up to 1.0.

La/Sm and La/Yb ratios in the Ternovka metabasites equal 2.2 and 2.5, respectively, similarly to basaltic komatiites of Pillar (Australia).

Mo ores (0.1-0.3 % of Mo) were found in the zones of quartzification. In addition,  Cu (up to 0.1-0.2 %), W (up to 0.01 %) and locally Au (up to 0.1 ppm in 0.5-1.5 m intervals) were detected in quartz-sulphide metasomatic zones.