Subsurface and Office Representation in Mining Geology 1035 



b. Approximate location and shape. 



Data located on the sectional plane are represented by short 



dashes closely spaced. 

 Projected data to sectional plane are represented by short 

 dashes; spacing distance indicates projection distance. 

 2. Doubtful or universal data: 



Data located on the sectional plane are represented by closely 



spaced dots. Projected data are indicated by dots; spacing 



distance indicates projection distance. 



The projection direction and inclination of geology is in a direction 



parallel to linear structure elements (flutings, mullion, striae, fold-axis 



lines, flow lines, etc.) ; the lines of least curvature on geologic structure 



usually coincide with net displacement or maximum elongation direction. 



Longitudinal projections are on either horizontal or vertical planes. 

 Vertical-section projection is convenient unless veins are at very low dip 

 angles. Vertical plane projection implies vertical shortening distortion, 

 and that ore volumes are products of length, horizontal width, and ver- 

 tical distance rather than length, true width, and inclined distance. The 

 projection plane is parallel to ordinate lines, even though the vein strike 

 is diagonal to ordinate lines; veins are unpredictable warped "planes" 

 varying laterally and vertically in attitude (frequently 30°). Since dip 

 distortion is accepted, additional strike distortion will not seriously affect 

 utilization of longitudinal projections systematically prepared on east- west 

 or north-south planes. Ordinate-direction orientation of the projection 

 plane simplifies longitudinal section preparation and facilitates better sec- 

 tional integration, correlation, and filing. East-west or north-south, rather 

 than true lengths of ore, are used in volume calculations; ton or volume 

 factors indicated by numerical contours on the longitudinal section facil- 

 itates calculation. 



(zeology (composition, texture, and intersecting structures) of both 

 vein walls may be represented on two separate longitudinal projections as 

 on plan maps. 



Vein configuration is represented by superimposed contours. The 

 Connolly vein-contouring technique is utilized to show vein or orebody 

 configuration. An auxiliary "datum" plane designated as zero "elevation" 

 is erected nearly parallel to the vein. Vein-offset distances or "elevations" 

 are measured; measure-point positions are projected to an east- west or 

 north-south vertical longitudinal section; and the "elevation" values are 

 contoured. Contours are superimposed on the texture-composition repre- 

 sentation. 



Miner alo graphic and Hand-Specimen Representntion — (Indicated in 

 figure 545.) Mine^alogic legend and paragenetic sequence representation 

 are combined. The same shading, hatching, or colors are utilized on both 

 the legend-paragenetic sequence diagram and the micro-sketch or photo. A 

 graphic scale is placed beneath the micro-sketch. 



