Two associated homodrome rhythms, starting from gabbros or diorites and comprising quartz diorites, granodiorites, adamellites, granites and leucocratic granites, are distinguished in the Magadan series. Both rhythms differ in petrochemical and geochemical features. In addition, granodiorites of rhythm I, composing the major part of the Magadan series rocks, exhibit the presence of ovoid inclusions of diorite and contrasting granite-leucocratic compositions. The inclusions are compositionally similar to diorite and leucogranite dikes localized in granodiorites, and diorite inclusions are extended to form dikes. This permits the inclusions to be treated as the intrusion products of the melts of contrasting composition into an imperfectly crystallized granodiorite intrusive body. The occurrence of diorite inclusions indicates the prolongating existence of the basic magma chamber corresponding at least to the formation of the basic rocks of rhythm I. A mantle source of gabbro-diorite melts, and essentially a crustal one for granitoids, is proposed. Based on the differences of basic rocks of both rhythms of the Magadan series, a conclusion is made about a two-fold rise of the melts of basalt composition into the crust. The genesis of high-potassium granites composing the margins of inclusions of the last phases of the series and the hypothesis of their deep-seated origin are discussed.
