Abstract
Fourteen core samples of Precambrian granitic gneisses from a well drilled in the Green Township, Scioto County, Ohio were studied to determine the origin of alkali feldspar in these rocks. The well intersected the basement at a depth of 1,700 m and penetrated 11.3m of Precambrian crystalline rocks. Petrographically the samples in the upper 6.4 m of the basement core show evidence of severe alteration by the presence of hematite, limonite and chlorite and by the absence of plagioclase. Alkali feldspars from this part of the core are turbid, have a low 2 V of about 10°, are highly enriched in K, have low Na and Rb concentrations, lack cathode luminescence, and form a straight line on a Rb-Sr isochron diagram yielding a date of 599±69 Ma. Core samples from below 6.4 m appear relatively fresh and unaltered. Alkali feldspar from this portion of the core is orthoclase, shows uniform blue luminescence and gives a Rb-Sr date of 1,162±11 Ma. These results indicate that feldspars in the lowest part of the core are primary minerals that crystallized during the Grenville Orogeny, whereas the K-feldspar in the top of the core is of low-temperature secondary origin. The formation of this feldspar is explained as a consequence of chemical weathering of primary feldspar during late Precambrian time to clay minerals that were later reconstituted under low-temperature hydrothermal conditions as K-feldspar (adularia) by reactions with brines derived from the overlying Mt. Simon Formation of Cambrian age.
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References
Ali AD, Turner P (1982) Authigenic K-feldspar in the Bromsgrove sandstone formation (Triassic) of central England. J Sediment Petrol 52:187–197
Barbis FC (1978) Rb-Sr geochronology of the Precambrian basement of Ohio. Unpub. M.Sc. thesis, Dept. Geol. and Mineral., The Ohio State University, Columbus, Ohio, p 83
Bass MN (1960) Grenville boundary in Ohio. J Geology 68:673–677
Botoman G (1975) Precambrian and Paleozoic stratigraphy and potential mineral deposits along the Cincinnati Arch of Ohio, Unpub. M.Sc. thesis, Dept. of Geol. and Mineral., The Ohio State University, Columbus, Ohio, p 137
Faure G, Barbis FC (in press) Detection of neoformed adularia by Rb-Sr age determinations of granitic rocks in Ohio. In: Augustithis SS (ed) Leaching and Diffusion
Faure G (1977) Principles of isotope geology. Wiley and Sons, New York, p 464
Gonterman RJ (1973) Petrographic study of the Precambrian basement rocks of Ohio. Unpub. M.Sc. thesis, Dept. of Geol. and Mineral., The Ohio State University, Columbus, Ohio
Janssens A (1973) Stratigraphy of the Cambrian and Lower Ordovician rocks in Ohio. Ohio Geological Survey Bulletin 64:197
Kastner M, Siever R (1979) Low temperature feldspars in sedimentary rocks. Am J Sci 279:435–479
Kastner M (1971) Authigenic feldspars in carbonate rocks. Am Mineral 56:1403–1442
Mensing TM (1982) Geochemical and Sr isotope investigation of low-temperature feldspar (adularia) in a Precambrian basement core from Scioto County, Ohio. Unpub. M.Sc. thesis, Dept. Geol. and Mineral., The Ohio State University, Columbus, Ohio, p 116
Shieh YN (1982) Oxygen isotope study of Precambrian granites from the Illinois deep hole project. J Geophys Res (in press)
York DJ (1969) Least-squares fitting of a straight line with correlated errors. Earth and Planet. Sci Letters: 5:320–324
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Laboratory for Isotope Geology and Geochemistry (Isotopia), Contribution No. 68
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Mensing, T.M., Faure, G. Identification and age of neoformed Paleozoic feldspar (adularia) in a Precambrian basement core from Scioto County, Ohio, USA. Contrib Mineral Petrol 82, 327–333 (1983). https://doi.org/10.1007/BF00399710
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DOI: https://doi.org/10.1007/BF00399710