Abstract:

 The structure of metallogenic system and oreforming processes are studied preliminarily in this essay for Corich MnFe crusts on the seamounts in the Pacific. Orecontrolling factors of ferromanganese metallogenic system on seamounts mainly include geological and oceanographic factors. The major geological factors are composed of the formation, migration and drowning of seamounts, as well as opening and closure of seaways. The major oceanographic factors are composed of thermohaline circulation, oxygen minimum zone (OMZ), aragonite lysocline, carbonate compensation depth, and hydrodynamic conditions around seamounts. This essay focuses on the orecontrolling factors on Corich FeMn crusts, which could be the migration and drowning of seamounts, opening and closure of seaways, evolution of OMZ, variation of ocean circulation and climate change. Seamounts provide an oreholding space for the precipitation of Corich FeMn crusts. Longterm stability of an oreholding space is the precondition for the precipitation of crusts; the age of seamounts, migration of seamounts, and the opening and closure of seaways constrained the evolution of oreforming background of seamount metallogenic system for Corich FeMn crusts. OMZ is the predominant geochemical barrier zone for the mineralization of crusts, and a major source for manganese; internal tide and eddies mixed the OMZ seawater and oxygen and Ferich deep and bottom water, which resulted in the oxidation of metal ions, aggregation and then the precipitation of colloid, and the formation of Corich FeMn crusts. Taking the Magellan Seamount Cluster and Marcuswake Seamount Cluster as an example, the oreforming process of Corich FeMn crusts since the late Cretaceous is divided into five stages: (1) the Cretaceousthe Eocene; (2) the Late Eocenethe Late Oligocene; (3) the Late Oligocenethe early Middle Miocene; (4) the early Middle Miocenethe early Late Miocene; (5) the early Late Miocenethe present. Stage 2 and 3 are favorable for the formation of Corich FeMn crusts.

Key words: Key words: seamount metallogenic system; Corich FeMn crusts; orecontrolling factors; oreforming processes and stages; the Pacific