Distribution of thorium, uranium, and potassium in igneous rocks of the Boulder batholith region, Montana, and its bearing on radiogenic heat production and heat flow

Abstract

________________________________________ El Introduction. ____ ______ ___ _ 1 Acknowledgments __ 2 Geologic setting... _____ ___ ___ 2 Distribution of thorium, uranium, and potassium in igneous rocks of the Boulder batholith region _ _ 6 Prebatholith volcanic rocks______ _ 6 Batholith rocks________ _______ ________ 6 Postbatholith volcanic rocks________ _______ 6 Para Distribution of thorium Continued Summary and comparison of thorium, uranium, and potassium abundance data____________________ E10 Nature of variation in thorium and uranium content.___ II Comparison of thorium and uranium distribution between contrasting magma series.__________________ 12 Radiogenic heat production and heat flow-________ 17 References.. ______________________________ 19 11. Postbatholith igneous rocks of probable early Tertiary age in the Boulder batholith region. ______ 12. Post-Lowland Creek volcanic rocks (Miocene or Pliocene) _ _____________ _ ________________ 13. Distribution of thorium and uranium in the Butte Quartz Monzonite from underground workings in the Butte district, Montana __

Using granite to image the thermal state of the source terrane

“…This conclusion is consistent with the measured values for the Pioneer Batholith, averaging about 2 /iW/m 5 (Zen, in prep. ) and for the Boulder Batholith, averaging about 3 /iW/m 3 (Tilling & Gottfried 1969), when compared to the typical Archaean cratonal value for N America, about 1 (uW/m 3 (Lachenbruch & Sass 1977). In the models I have used the last value for the source rocks because it may be more representative than the "upper limits" given by the batholiths.…”

Trace element variation in the leucogranites within the main Galway Granite, Connemara, Ireland

“…The latter display a wide variation in U and Th contents typical of highly fractionated granites (Rogers and Ragland, 1961;Tilling and Gottfried, 1969). M.G.1 and M.G.6 (garnetiferous), the most fractionated Murvey granites, contain the highest levels of U.…”

Evaluation of a hydrothermal anomaly near Ennis, Montana

“…As stated by R.H. Mariner (U.S. Geological Survey, written commun., 1980), "The relatively large helium content, almost certainly, must originate from radioac tive decay in the basement rock, although leakage from the mantle cannot be ruled out without isotopic data." Radioactive decay might be a major source of the geothermal heat (Tilling and Gottfried, 1969;Blackwell and Robertson, 1973;Gabelman, 1976), but further study of this aspect was beyond the scope of this in vestigation. The source of the helium in test hole TX-11 is probably the fractured gneiss, as evidenced by the abnormally large response of the natural gamma logs, but the water is not anomalously radioactive.…”