Abstract

Publications of the last 25 years that discuss the emplacement of granite plutons are reviewed, with special reference to North America. The plutons are classified according to emplacement in the epizone, mesozone, or catazone of the earth's crust. It is found that those emplaced in the epizone are almost wholly discordant; those in the mesozone complex, in part discordant and in part concordant; and those of the catazone predominantly concordant. Granite formed by granitization is considered to be minor or local in plutons of the epizone, common but subordinate in those of the mesozone, and a major factor in plutons of the catazone. The authors of the papers reviewed in general, however, infer that magma was either directly or indirectly the major factor in all the zones. Contrary to some current theories, this review emphasizes the great number and great total volume of granitic plutons emplaced as fluid magma in the epizone and their community of origin with lavas of similar composition directly associated in time and space. Magma is thus inferred to play the major role in Tertiary stocks and batholiths. There appears to be no discontinuity between plutons of the epizone and those of the mesozone, and a major role for magma is indicated for the latter also. The evidence is not clear as to whether plutons of the mesozone are continuous with those of the catazone, have roots in the catazone, or are pinched off from it. Batholiths emplaced in the mesozone are dominant in most basement complexes of Precambrian to Early Cretaceous ages.

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