Origination petrographic thin sections

Syngenicity Are the features syngenetic with a primary mineral phase of the rock Or, on the contrary, are they of later origin, e.g. introduced into pores or fracmres and lithified by secondary or later-generation minerals, a test that can usually be met by appropriately careful study of petrographic thin sections. 

Petrographic Studies. Polished thin sections were examined by optical methods to determine original mineralogy and alteration phases. The sections were taken and oriented in such a manner to allow comparison of the microscopic mineralogy with the results of the autoradiography experiments The shale was too fine-grained to be characterized in detail. 

Petrographically, Spannagel flowstone and stalagmites are composed of coarsely crystalline, columnar calcite indicating slow precipitation rates (e.g., Frisia et al., 2000). Lamination is rare in these samples, although faint laminae of possible annual origin were identified in thin section by epifluorescence microscopy. Postdepositional alteration is confined to macroscopic dissolution features, while there is little evidence of in-situ recrystallization in our samples. 

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