Chronology of intrusion, volcanism, and ore deposition at Bingham, Utah— A reply
No abstract available.
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Geology topics
W. J. Moore
Publications and source records attributed to W. J. Moore.
Chronology of intrusion, volcanism, and ore deposition at Bingham, Utah
Potassium-argon dates for major igneous rock types in the Bingham mining district, Utah, range from 39 to 32 m.y. and suggest that:(1) Plutonism, volcanism, and hydrothermal activity were sequential stages in a magmatic history of about 7 m.y. duration.(2) Latitic volcanic rocks, in part, postdate emplacement of the Last Chance and Bingham stocks.(3) Sulfide mineralization and hydrothermal alteration followed emplacement of the monzonitic stocks and extrusion of at least the earliest units in the volcanic sequence; the time interval between intrusion and alteration was probably less than 1 m.y.(4) The rhyolites of Shaggy Peak, which may represent terminal differentiation products in a comagmatic series, are the youngest igneous rocks in the area.
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Precision measurement of lead isotopes ratios: preliminary analyses from the U.S. mine, Bingham Canyon, Utah
A gas-source mass spectrometer has been constructed for the precise measurement of lead isotope ratios. Sixteen analyses on 4 different preparations of the same galena made over a period of 2 months gave 95% confidence limits (per analysis) of 206 Pb/ 204 Pb= 0.080%, 207 Pb/ 206 Pb= 0.042%and 208 Pb/ 206 Pb= 0.046% . Eight samples from the U.S. mine in the Bingham district have a linear relationship over the 1% range of their 206 Pb/ 204 Pb ratios. The simplest model fitting these data suggests that the lead was separated from a primary system (μ=8.98) 1630±150m.y. ago and subsequently mixed with a radiogenic lead of similar age; biotite K-Ar dates for altered intrusive rocks associated with the ores provide an apparent age of mineralization and suggest that isotopic evolution of the lead was terminated about 36 m.y. ago.
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