Abstract

Rare earth element (REE), Th, and Sc analyses of mudstones from the contact metamorphic aureole of the Middle Jurassic Emigrant Gap composite pluton support the idea that the lower Paleozoic Lang, Black Oak Spring, and Zion Hill sequences are composed of detritus derived from a continental landmass. On REE distribution diagrams, our samples exhibited (1) no systematic change as a result of varying metamorphic grade, (2) light-REE enrichment trends, and (3) Eu anomalies that vary from 0.46 to 0.93 and average 0.66. On a La-Th-Sc ternary diagram, our data cluster within the fields of passive-margin sediment and post-Archean Australian shale (PAAS). These new data—in conjunction with the quartz-rich character of sandstones, the absence of volcanic material, and Precambrian detrital zircon ages—suggest that clastic material in the Lang, Black Oak spring, and Zion Hill sequences was derived from a continental landmass that may have been North America or, alternatively, some continental fragment oceanward of early Paleozoic North America.

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