The main applications of a handheld K-, eU-, eTH- spectrometer at geological issues are:

Determination of insitu concentrations of natural (K, eU, eTh) elements in the field.

Identification of artificial radiation sources in the field.

Radiation monitoring and mapping by point-, profile-, and continuous measurements in the field. Here, the geological boundaries  between acidic, potassium-rich, granitic rocks and potassium-poor rocks can be mapped.

Furthermore, special element anomalies can be localized, which are concentrated in the U- and Th-bearing minerals (U, Th-prospecting for zircon, monazite, apatite, etc.).

Portable gamma-ray spectrometers are especially designed for surface and borehole measurements.

Best regards,

G. Grundmann

When you are studying sedimentary sequences, you can deduce from total gamma-ray signal the relative proportion of clay within the sedimentary rock.

Using spectral gamma-ray signal, you can trace the concentration of U, Th and K. This is useful for tracing potential zone of organic matter enrichment, where U-enrichment, disconnected from Th and K enrichment, are observed.

Have a look at one of my paper (and references therein):

Bodin et al. (2011) Early Toarcian source rock potential in the Central High Atlas Basin (Central Morocco): Regional distribution and depositional model. Journal of Petroleum Geology, 34(4):345 - 363

Article Early toarcian source-rock potential in the central high atl...

Thanks  really i find you paper very useful, cause i focus in my study to determine  TOC from log 

Regards

The Th-U-K model for clay mineral and TOC identification was developed in the 50s-60s by the wireline industry based on a handful of geological studies of elemental analyses of clay minerals. While the Th-K relationships developed in those early papers remains the subject of some debate (i.e. just how well does Th indicate the presence of Kaolinite...) the U signal does have a strong correlation with the presence of organic matter. There is no universal correlation between U content and TOC, but within a basin a given correlation tends to work reasonably well. If you are looking at an improved TOC indicator from logs, consider adding other tools. There is some very nice work with the elemental spectroscopy tools (C, O, S, etc...) that add more character and detail to TOC evaluation. Check out papers by Susan Herron et al - Schlumberger over the past 20 years.

Thanks dear James

James Howard is correct. One influence factor for differences in OM response to the U content is its nature. Marine organic matter is enriched in U, but lacustrine OM is not. Rations U/Th, U/K and K/Th are usefull for paleoenvironmental inferences. About paleoenvironmental reconstruction, please see the conference paper "APLICAÇÃO DA GAMAESPECTROMETRIA EM TESTEMUNHOS COLETADOS NO ESTREITO DE BRANSFIELD, PENÍNSULA ANTÁRTICA" on my page https://www.researchgate.net/profile/Fernando_Freire10/research. Sorry, it is in Portuguese, but I think you can get some ideias from the figures. Now we are writing a paper in English about this.