Ore-bearing explosive breccias of the final phase of the early Paleocene (Dalnegorsk) magmatic impulse in the Sikhote-Alin: data of thermobaric and geochemical study of inclusions in quartz

Abstract

We have studied explosion-breccias of the Solontsovaya volcano-tectonic structure located in the Dalnegorsk ore district within the Sikhote-Alin. The structure is composed of early Paleocene rocks of the Dalnegorsk volcanic-plutonic association. It is shown that explosion-breccias relate to the final stage of formation of the central-type volcanic edifice and are, probably, synchronous with the Pb-Zn skarn mineralization. The analysis of melt inclusions in breccia quartz indicates that early Paleocene chambers saturated with fluids should be associated with the superplumasitic melt of trachydacitic composition (ASI = 1.1) rich in sulfur, chlore and ore components (Zn, Mn, Fe, Ti). The presence of more siliceous ultrapotassic melts of rhyo- dacitic composition in a chamber is considered as a result of fluid-magmatic differentiation of trachydacitic melt during the intensive albite crystallization. Explosive breccias can serve as a forecasting and prospecting indicator in the assessment of possible ore content in the volcanic structures of the Dalnegorsk ore district in regard to the deep-seated Pb-Zn mineralization.