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Abstract

The northern Pacific Rim, defined as stretching from southern China to southern Mexico, displays profound differences in both metallogenic character and regulatory environment. The largest Mesozoic and Cenozoic ore deposits of the northwestern Pacific quadrant contain principally tin, tungsten, molybdenum, or gold, whereas those in the northeastern quadrant are dominated by copper, silver, molybdenum, or gold. The regulatory environments of the northwestern Pacific Rim countries are generally considered less attractive for equity-financed exploration than those of the northeastern Pacific, as witnessed by the far fewer active companies and projects in the former compared to the latter. Furthermore, there is little western company exploration anywhere for tin, tungsten, and molybdenum, arguably some of the prime targets in the northwestern Pacific quadrant. Therefore, notwithstanding greater state funding of exploration in the northwestern Pacific quadrant, particularly in eastern China and the Russian Far East, the northeastern Pacific region has been the subject of far more effective exploration during the past two decades.

More than two-thirds of the 67 principal metal deposits around the northern Pacific Rim are confined to and help define 20 spatially restricted metallogenic provinces, many the products of several discrete metallogenic epochs. The positions of these provinces may reflect the character of the underlying lithosphere. Nearly 40% of these major deposits had been discovered by the early decades of the 20th century, either accidentally or, chiefly in the western Americas, as a result of traditional prospecting. Since the 1940s, geologic, geochemical, and, to a lesser degree, geophysical techniques became progressively more widely employed. Geologic observation, mapping, and conventional geochemical exploration techniques led to most major discoveries before the mid-1990s. Application of broadly similar methods also resulted in the 15 more recent discoveries, 11 of which are located in the northeastern Pacific quadrant; all except four in the previously known metallogenic provinces. Most of the major discoveries from the mid-1990s onward were near known mineralization, seven of those in the northeastern quadrant involving junior exploration companies and four in the northwestern quadrant by semiautonomous provincial agencies. Eleven of the deposits discovered since the early 1990s were wholly or partly exposed, with the remainder completely concealed beneath pre- and/or postmineralization cover.

It is predicted that the northeastern Pacific quadrant will continue to attract the majority of effective exploration attention and, as a consequence, will continue to dominate the northern Pacific Rim discovery record into the foreseeable future. Most major new deposits are likely to be located in the defined metallogenic provinces and to result from conventional exploration programs increasingly underpinned by conceptual geology and robust drilling budgets.

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