ABSTRACT: Tectonics and the Metal-Bearing Characteristics of the Sedimentary Cover of the Pacific Ocean and the Marginal Seas
L. E. Levin, E. N. Isaev, I. M. Mirchink, I. S. Gramberg, L. I. Krasny
The metal-bearing sedimentary cover of the Pacific Ocean floor is characterized by 17 horizons at different levels from the basalt top of layer 2A up to Pleistocene. The metal-bearing sections (Tithonian-Albian, Upper Cretaceous-Eocene, Oligocene-Pleistocene) indicate clearly the dependence on endogenic activity in the evolution of oceanic crust and its volcano-sedimentary cover: hydrothermal after ending of each spreading stage, supply of metals from volcanic processes of oceanic crust reworking from Early Cretaceous to Pleistocene. Principal differences exist in metallogenesis between the East Pacific Rise and the West Pacific Tectonic region. This difference is caused by two different tectonic regimes of the Pacific ocean floor--the direction of oceanic crust spreading and the superimposed processes of intraplate volcanism. Each type of metal accumulation is characterized by distinct tectonic conditions that determine their formation and distribution. Sulfide accumulations appear to be confined to metal-bearing horizons in the basins of the early oceanic sedimentation stage, i.e., Late Jurassic-Early Cretaceous. The sediments with manganese oxides and accompanying heavy metals occur predominantly in Late Cretaceous-Pleistocene basins. The metal-bearing horizons of increased thickness (150 m) and geochemical concentrations (content of manganese oxides is 26-34% and the sum of copper, nickel, and cobalt is up to 3.47%) is characterized by interdependence between the superposition in space of different-age metal-bearing horizons, the highest spreading rat (5.2-9.8 cm/m.y.) and synchronous intraplate volcanism. Ten such areas are distinguished in the Pacific Ocean and Philippine Sea with possibly large reserves of metals.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990