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The Maimon Formation consists largely of metavolcanic rocks with a small proportion of metasediments. Specific premetamorphic lithologic units that have been identified by a combination of field mapping, petrographic study, and chemical analyses include metabasalt (pyroxene-plagioclase and related mafic plagioclase porphyry), metadacite/metarhyolite (quartz porphyries), undivided metavolcanic rocks (largely plagioclase porphyry; probably metaandesite), and metasediments (including limestone [now marble], iron formation, and carbonaceous shale [now slate]). Although flows are common in the Maimon Formation, agglomerates and tuffs are also present.

Rock types and textures suggest that most of the Maimon Formation volcanic rocks were emplaced in a submarine environment and that water depths increased to the southeast. Many rocks have undergone both seafloor and regional metamorphism, and much of the formation consists of the assemblage epidote-chlorite-albite. Less deformed zones throughout the Maimon Formation preserve remnant phenocrysts, and remnant pillows and amygdules are present in the northern part. Foliation, which apparently resulted from regional metamorphism, is widespread but is best developed in the northwestern part of the Maimon Formation, where actinolite is part of the metamorphic assemblage.

The Maimon Formation is part of a belt of low-grade metamorphic rocks, including the Amina Schist, that crops out along the northern margin of the Cordillera Central. Whereas chemical compositions of the Maimon Formation support the interpretation that it consists largely of metavolcanic rocks that were altered by seafloor metamorphism, published chemical analyses for the Amina Schist are richer in CaO and could represent volcaniclastic metasediments. Neither the Maimon nor the Amina chemical analyses are as strongly bimodal as the Los Ranchos Formation, with which correlation has been suggested, and the types of mineral deposits in these formations also differ significantly. If these three units are coeval, they must have formed in different environments, with the Los Ranchos Formation forming on a seamount or other elevated seafloor, the Maimon Formation forming in a more typical oceanic island-arc setting, and the Amina Schists forming from detritus derived from these or other rocks.

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