264 REPORTS ON THE STATE OF SCIENCE, ETC. 



Rock Temperatures and some Ventilation Conditions in the 

 Mines of Northern Ontario. 



By Ralph H. Cleland. 



The Canadian Mining and Metallurgical Bulletin, Montreal, no. 256, 1933, 



PP- 379-407- 



This paper is a resume of a brief survey of rock temperatures made by 

 the Ontario Department of Mines during 1932. Present temperatures 

 were recorded, and the geothermal gradients that now exist were determined. 



The geothermometer used is described, and details of instruments for 

 measuring rock temperatures are shown in a diagram. 



Geological summaries and temperature conditions in the following 

 districts are given : (1) Porcupine district ; (2) Kirkland Lake district ; 

 and (3) Sudbury district — Frood mine. 



Excerpts from various articles showing rock-temperature conditions in 

 other places are given. The two last chapters deal with the geothermal 

 gradient variations and the underground air conditions. 



The Significance of Underground Temperatures. 



By M. W. Strong. 

 The Petroleum Times, London, vol. 30, no. 758, 1933, p. 132. 



The author discusses in turn the factors governing underground tempera- 

 tures and draws a number of conclusions from his studies. 



He next discusses chemical action, such as oxidation, hydration, pyritisa- 

 tion, etc. The conductivity difference of rocks is shown to be a major 

 cause of varying gradients, while the effect of diffusivity difference of rocks 

 is important where rapid changes are taking place. 



Rapid denudation tends to increase gradients, especially at the surface, 

 while rapid deposition in geosynclines tends toward lower gradients. 

 Squeezing out of incompetent strata also tends to give high gradients. 

 Thrusts and the tectonic piling-up of strata both tend to lower the gradient 

 by burying large masses of rocks at low temperature. As to the upward 

 movement of rock, intrusive salt plugs and igneous masses will increase 

 the gradient. This effect should be sought for only in the late Tertiary 

 strata, unless very large masses have been involved. The effect of late 

 emergence of strata after a long period beneath the sea is that the gradient 

 may be lowered if emergence is in a warm region. The effect of direction 

 of flow of underground waters is determined by topographic, stratigraphic, 

 and tectonic factors, while Quaternary climatic changes may have an 

 important effect on underground temperatures by altering the mean surface 

 temperature. 



Special factors are : (a) The loss of heat due to gas escape and oil seepages 

 from oil-fields, and (b) replacement of oil by incoming water. As to (a), 

 this refers to loss by old seepages extending over geological time, and 

 appreciable amounts of heat may be lost in this way whose effect will vary 

 with the porosity and size of the reservoir. As to (b), if the influx is large 

 and from below, increasing temperatures might accompany it ; if slow 

 and coming in laterally, this effect might be masked. 



