Abstract
Data from analysis of fluid inclusions in carbonates of the northern Appalachian basin indicate higher paleotemperatures and greater depths of burial than have been inferred for the rocks of this region. Preliminary research has revealed fluid homogenization temperatures averaging 96°C (205°F) for the formation of saddle dolomite, 114°C-170°C (237°F-338°F) for calcite vein fillings, and 290°C (554°F) for calcite cements in samples from the Mohawk and Champlain valleys of New York state. The calcite-filled veins sampled in the Champlain valley of eastern New York display higher average homogenization temperatures than similar veins from the Mohawk valley of central New York. This difference may reflect a higher post-Early Ordovician paleogeothermal gradient operative in eastern New York. Drusy calcite cements in samples from central New York are interpreted as precipitates from saline brines having temperatures between 267°C (512°F) and 302°C (576°F). These temperatures support conodont alteration data obtained by others for the rocks of this area. Using a geothermal gradient of 25°C/km (72°F/mi), a former depth of burial in excess of 9 km (5.6 mi) is implied. Seismic and gravity data do not show evidence of the presence of post-Early Ordovician shallow plutons. Therefore, it appears unlikely that precipitation at the high temperatures measured resulted from magma-derived hot meteoric fluids. End_of_Article - Last_Page 1930------------
Published Version
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