Zhensheng Chen, Lee R. Riciputi, Claudia I. Mora, Neil S. Fishman; Regional fluid migration in the Illinois basin: Evidence from in situ oxygen isotope analysis of authigenic K-feldspar and quartz from the Mount Simon Sandstone. Geology ; 29 (12): 1067–1070. doi: https://doi.org/10.1130/0091-7613(2001)029<1067:RFMITI>2.0.CO;2
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Oxygen isotope compositions of widespread, authigenic K-feldspar and quartz overgrowths and cements in the Upper Cambrian Mount Simon Sandstone were measured by ion microprobe in 11 samples distributed across the Illinois basin and its periphery. Average K-feldspar δ18O values increase systematically from +14‰ ± 1‰ in the southernmost and deepest samples in Illinois to +24‰ ± 2‰ in the northernmost outcrop sample in Wisconsin. A similar trend was observed for quartz overgrowths (22‰ ± 2‰ to 28‰ ± 2‰). Constant homogenization temperatures (100–130 °C) of fluid inclusions associated with quartz overgrowths throughout the basin suggest that the geographic trend in oxygen isotope compositions is a result of diagenetic modification of a south to north migrating basinal fluid.