1020 Subsurface Geologic Methods 



location and magnitude. Surface installations (mills, smelters, tailings, 

 dumps, roads, etc.) indicate localization and size of past operations, and 

 the recovery processes utilized. 



All fragmentary information must be integrated to determine miner- 

 alogy, magnitude of deposits, and past mine economics. This type of inte- 

 gration facilitates better interpretative geology and consequent future 

 planning. 



Physiography usually reflects geology, and, when locally calibrated 

 to geology, is a valuable and useful aid to geologic correlation and inter- 

 pretation. 



The legend and symbols shown in figures 539 and 540 follow for the 

 most part U.S.G.S. standardization. 



The first cultural symbol shown is for scaled representation and is 

 used for detailed mapping; the generalized symbols to the right are for 

 reconnaissance mapping. 



Culture is represented in black. Even elevation contours are black 

 when occurring on man-made features (dumps, cuts, etc.) ; the original 

 natural topography is represented by dashed-brown superimposed con- 

 tours. 



Cultural excavation features (cuts, fill, dumps, tailings, and culti- 

 vated ground) are represented by both cultural and lithological legend. 

 The compositional representation conforms with geologic symbols and 

 colors. Thus, a dump may be indicated by cultural legend with superim- 

 posed green, red, and purple stipple indicating granite, vein quartz, and 

 sulfides composition. 



Side-note descriptions or numbers are neatly lettered in lower case. 

 The lettering should be as small as legibility will permit. If representa- 

 tion is orderly and systematic, it will not be necessary to erase or repost 

 previous side-note observation to make room for new data. An area or 

 point (described by side note) is indicated by a line parallel with ordinate 

 lines. When it has become habit to post side-note lines in an east-west or 

 north-south direction, the geologist will find that he has more room on 

 the sheet for recording of detailed observation. 



All culture, ordinate lines and values, and engineering data are 

 posted on the glazed or reverse side of the tracing-cloth maps. 



Geology — Mining-geologic representation facilitates prediction of ore 

 localization. The following geologic legend graphically and decisively 

 represents structure, texture, composition (primary and superimposed 

 metamorphic or hydrothermal effects), and stratigraphy. A better un- 

 derstanding of the geologic-representation system will result if the repre- 

 sentation objectives are considered. 



1. Ore Localization Factors: 



a. Genetic or Source Control: The location of a cupola deter- 

 mines source point and consequent primary pattern of hydro- 

 thermal effects. Zonation or annular pattern of magmatic and 



