Changes

==Spectral gamma-ray logs==

==Spectral gamma-ray logs==

Spectral gamma-ray logs measure the relative contribution of potassium, thorium, and uranium to the overall gamma-ray response. A high potassium content generally indicates the presence of minerals such as potassium feldspar and mica. Thorium is associated with the mineral monazite, a common heavy mineral in sandstones sourced from acid igneous rocks.<ref name=Hurstandmilodowski_1996>Hurst, A., and A. Milodowski, 1996, Thorium distribution in some North Sea sandstones: Implications for petrophysical evaluation: Petroleum Geoscience, v. 2, no. 1, p. 69–68.</ref> Uranium is commonly found absorbed onto organic material and clay in marine shales.<ref name=Serra_1984 />

Spectral gamma-ray logs measure the relative contribution of potassium, thorium, and uranium to the overall gamma-ray response. A high potassium content generally indicates the presence of minerals such as potassium feldspar and mica. Thorium is associated with the mineral monazite, a common heavy mineral in sandstones sourced from acid [[igneous rock]]s.<ref name=Hurstandmilodowski_1996>Hurst, A., and A. Milodowski, 1996, Thorium distribution in some North Sea sandstones: Implications for petrophysical evaluation: Petroleum Geoscience, v. 2, no. 1, p. 69–68.</ref> Uranium is commonly found absorbed onto organic material and clay in marine shales.<ref name=Serra_1984 />

Spectral gamma-ray logs are used less frequently than the other types of log, although in certain situations they can pick out features that the other logs will not.<ref name=Hancock_1992>Hancock, N. J., 1992, [[Quick-look lithology from logs]], in D. Morton-Thompson and A. M. Woods, eds., [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me10.htm Development geology reference manual]: AAPG Methods in Exploration Series 10, p. 174–179.</ref> For example, the spectral gamma-ray log response can be used to identify a zone of potassium feldspar dissolution in leached sandstone below an unconformity.

Spectral gamma-ray logs are used less frequently than the other types of log, although in certain situations they can pick out features that the other logs will not.<ref name=Hancock_1992>Hancock, N. J., 1992, [[Quick-look lithology from logs]], in D. Morton-Thompson and A. M. Woods, eds., [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me10.htm Development geology reference manual]: AAPG Methods in Exploration Series 10, p. 174–179.</ref> For example, the spectral gamma-ray log response can be used to identify a zone of potassium feldspar dissolution in leached sandstone below an unconformity.