Av. Koloskov et al., Potassic volcanics of Central Kamchatka and the Late Cretaceous-Paleogene Kuril-Kamchatka alkaline province, PETROLOGY, 7(5), 1999, pp. 527-543
New and published geochemical data on the Late Cretaceous-Paleogene potassi
c subalkalic and alkalic volcanic rocks of the Kuril-Kamchatka alkaline pro
vince (Little Kurils, Central Kamchatka, Eastern Kamchatka, Belaya River, a
nd Southern Koryak Range) were analyzed. In contrast to a widely accepted o
pinion on the affiliation of these volcanics with the shoshonite series of
the island-are type, the potassic alkalic and subalkalic volcanics of the p
rovince are considered as part of the series of lamproite-like rocks. They
show high Mg, Cr, and Ni contents, variable concentrations of a number of i
ncompatible elements at restricted variations in potassium contents (define
d by equilibrium with phlogopite under magmatic or metasomatic conditions),
and depletion in Th, U, Zr, and Hf. These characteristics are typical of t
he low-titanium varieties of lamproite-series rocks. The lamproite-like roc
ks were distinguished into a particular series, which appears in the geodyn
amic environment of incipient rifting in an island-are system.