Research on the relationships between cobalt-rich crusts and substrate rocks in the Mid-Pacific Mountains

The features of texture and structures,mineral and chemical compositions of substrate rocks and cobaltcrusts in the Mid-Pacific Mountains are identified and analysed.The results indicate that the major types of substrate rocks are alkaline basalt,phosphorite,phosphatized carbonate rocks and cherts in this area.In the above-mentioned rocks,the alkaline basalt is the most widespread one,and has been weathered to some extent.The observation has shown that the carrier of cobaltcrust can be all kinds of rocks.The thickness of crusts on basalts,weathered volcanic rocks,etc.is greater than that of cherts.The thicker crusts have more economic value and are major objects for dressing and smelting.The cobal-trich crusts in the research area can be divided into three types according to the shape:plate,gravel-like and nodule-like crust.The relationships between crusts and substrate rocks have been probed from the following four aspects:(1) the characteristics of major metallic elements content in seaw ater,substrate rocks and crusts;(2) the different close relations between different bedrocks and crusts by cluster analysis; (3) the distribution characteristics of crusts;(4) the influence of rock types on the growth of crusts.The conclusion is that volcanic rock,phosphorite,etc.contribute to the formation of the crust.