Layered Gabbroids of the Pekulney Ridge, Chukotka, Northeastern Russia: Geology, Petrography, Age, and Geodynamics

The author has actualized the data obtained by her own research and from publications to conclude that gabbroids in the northern part of the Pekulney Ridge build a large intrusion, named Svetlorechensky. It belongs to the type special for the region: it possesses features of layered plutons and multiphase intrusions. It is classified as a petrotype of a gabbro complex of the same name, whose bodies are present in the southern part of the ridge, as well. The establishing of the Svetlorechensky complex took place in the Early Cretaceous (most probably in the Hauterivian). The original composition of the parent magma was characterized as typical island arc tholeitic basalt. Amphibole-two-pyroxene rocks of the Pekulneyveem River basin, supposedly dated back to the Archean by previous researchers, build the marginal series in the first intrusive phase of the Svetlorechensky pluton. Among the host complexes, the author has established stratified high-temperature metamorphic formations, supposedly Paleozoic, and “pre-Svetlorechensky” gabbroids. The deep structure reconstruction for the pluton permitted to interpret it as a heavily asymmetric harpo - lith, localized in the hanging side of a long-developed ancient island arc uplift.