GEOCHEMISTRY AND FORMATION CONDITIONS OF Ni-BEARING GABBRO-CORTLANDITE COMPLEX ON THE KAMCHATKA PENINSULA

The internal structure and proportions of the main rocks of the Kuvalorog gabbro-cort-landite massif, the largest intrusion on the Kamchatka Peninsula, are considered. The intrusive rocks are shown to abound in pargasitic amphibolite and biotite. Ultrabasic orthopyroxene contains melt inclusions with porphyritic pargasite phenocrysts, which point to a high water content in the parental melt of this intrusion. In trace-element patterns of rocks and minerals the massif is similar to Ni-bearing traps of the Siberian Platform. The behavior of lanthanides in the cortlandites evidences that their parental magma was melted out of a garnet-bearing mantle source and then crystallized under high-pressure conditions. Like the productive intrusions in the Noril’sk district, the rocks and all rock-forming minerals of the Kuvalorog massif are depleted in Ni relative to chondrite C1, which indicates a high Ni-sulfide ore potential of the massif. Trace-element pattern, rocks, minerals, depletion, nickel, gabbro-cortlandite complex, rifting In recent years, the interest in the exploitation of commercial Ni-sulfide ores of gabbro-cortlandite intrusions in the south of the Sredinny Ridge (Kamchatka Peninsula) has been renewed. It is obvious that this problem cannot be realized without a geological study of ore-bearing intrusive complex in this region. Numerous geological investigations into gabbro-cortlandite intrusions in the Far East were performed in the 1970–80s [Zimin, 1973