Ten potential target areas for metallic mineral exploration were selected on the basis of a photo-lineament interpretation of the ERTS image 1172-17141 in central Colorado. An evaluation of bias indicated that prior geologic knowledge of the region had little, if any, effect on target selection. In addition, a contoured plot of the frequency of photo-lineament intersections was made to determine what relationships exist between the photo-lineaments and mineral districts. Comparison of this plot with a plot of the mineral districts indicates that areas with a high frequency of intersections commonly coincide with known mineral districts. The results of this experiment suggest that photo-lineaments are fractures or fracture-controlled features, and their distribution may be a guide to metallic mineral deposits in Colorado, and probably other areas as well

Nicolais, S. M.

English

NASA Technical Reports Server

Paper G 14 
MINERAL EXPLORATION WITH ERTS IMAGERY 
Stephen M. Nicolais, Colorado School of Mines 
Ten p o t e n t i a l  t a r g e t  areas f o r  metallic mineral explora- 
t i o n  w e r e  selected on t h e  b a s i s  of a photo-lineament 
i n t e r p r e t a t i o n  of the ERTS image 1172-17141 i n  c e n t r a l  
Colorado. O f  t h e  t e n  t a r g e t  areas selected, f i v e  in-  
cluded t h e  following mineral districts: the Breckenridge , 
d i s t r i c t ,  the  Leadville-Climax-Alma area, and t h e  Tomichi,, 
# 
Bonanza and Cripple  Creek d i s t r i c t s .  An evaluat ion of 
bias ind ica ted  t h a t  p r i o r  geologic knowledge of the 
region had l i t t l e ,  i f  any, effect on t a r g e t  s e l ec t ion .  
In  addi t ion ,  a contoured p l o t  of the  frequency of 
photo-lineament i n t e r s e c t i o n s  w a s  made to determine 
and mineral d i s t r i c t s .  Comparison of t h i s  p l o t  w i t h  a 
p l o t  of the  mineral d i s t r i c t s  i nd ica t e s  t h a t  areas 
w i t h  a high frequency of i n t e r s e c t i o n s  commonly coincide 
w i t h  known mineral d i s t r i c t s .  The r e s u l t s  of t h i s  
experiment suggest t h a t  photo-lineaments are f r a c t u r e s  
may be a guide t o  metallic mineral depos i t s  i n  Colorado, 
and probably o the r  areas as w e l l .  
c*c 
what r e l a t ionsh ips  e x i s t  between t h e  photo-lineaments ‘I 
1 
I 
I o r  f rac ture-cont ro l led  features ,and t h e i r  d i s t r i b u t i o n  
INTRODUCTION 
Mineral explorat ion i s  an of ten-ci ted p o t e n t i a l  appl ica t ion  of 
o r b i t a l  remote sensing data. However, before a new method, system 
o r  instrument i s  employed by industry,  it must show p o t e n t i a l  use 
and economic f e a s i b i l i t y .  In  t h i s  l i gh t ,  an experiment w a s  
designed t o  test t h e  appl ica t ion  of photo-lineament information 
obtained from ERTS imagery t o  t h e  se l ec t ion  of p o t e n t i a l  t a r g e t  
areas for mineral explorat ion.  The ob jec t ives  of t h e  experiment 
w e r e  : 
1) To select p o t e n t i a l  target areas based on the d i s t r i b u t i o n  of 
photo-lineaments and t h e i r  i n t e r sec t ions ,  as obtained from the  
ERTS image. 
To eva lua te  t h e  t a r g e t  areas. 
t r i b u t i o n  of photo-lineament i n t e r s e c t i o n s  and t h e  loca t ion  of 
mineral d i s t r i c t s .  
2) 
3) T o  determine what r e l a t ionsh ips ,  i f  any, e x i s t  between t h e  dis- 
https://ntrs.nasa.gov/search.jsp?R=19740022646 2020-03-17T15:06:16+00:00Z
The test  area w a s  defined by a s i n g l e  ERTS image of c e n t r a l  
Colorado (Pig. l), which includes a p a r t  of t h e  Colorado Mineral 
B e l t ,  and thus ,  severa l  major mining d i s t r i c t s .  The northeast-  
t rending mineral b e l t  i s  character ized by i n t r u s i v e  porphyries 
of L a t e  Cretaceous and e a r l y  Te r t i a ry  age (1). O r e  deposi t ion,  
i n  most cases, w a s  s t r u c t u r a l l y  cont ro l led  by f a u l t s  and shear 
zones. 
Phot o i n t e  r p r e t  a t  ion  
Photo in te rpre ta t ion  w a s  performed on t h e  11 January 1973 image 
U72-17141 (Fig. 2 )  using a Bausch & Lomb zoom stereoscope i n  
both s tereoscopic  and monoscopic modes. The 9.5 x 9.5-inch 
i t i v e  t ransparenc ies  of a l l  four  M S S  bands w e r e  used; however, 
t of t h e  da t a  w a s  obtained from band 7. This  image w a s  chosen 
r o ther  images of t h e  same scene because t h e  topography i s  
anced by t h e  low-angle s o l a r  i l luminat ion (23' i nc l ina t ion )  
snow cover i n  t h e  mid-winter imagery. The f i r s t  s t e p  of  t h e  
eriment consis ted of i n t e r p r e t i n g  t h e  ERTS image and p l o t t i n g  
fh? photo-lineaments on an overlay (Fig. 3 ) .  
w e r e  p lo t ted :  
Two types of elements 
s t r a i g h t  lineaments and cu rv i l i nea r ,o r  c i r cu la r ,  
8 
4 3 a a a g e t  A r e a  Select ion 
d ten t ia l  reconnaissance t a r g e t  areas w e r e  s e l ec t ed  on t h e  b a s i s  
of t h e  lineament d a t a  obtained. Se lec t ions  w e r e  made under t h e  
following assumptions : 
1) W e  are looking f o r  metallic mineral depos i t s  
2 )  Mineralization i s  probably s t r u c t u r a l l y  r e l a t e d  t o  f a u l t s  and 
shear  zones, which may, i n  tu rn ,  be s p a t i a l l y  r e l a t e d  t o  
i n t r u s i v e  s tocks,  plugs and volcanic centers .  
Target s e l ec t ion  cons is ted  of two s t eps .  F i r s t ,  about 40 s m a l l ,  
s p e c i f i c  t a r g e t s  w e r e  chosen based on t h e  numbers and kinds of 
photo-lineament in t e r sec t ions .  Next, t h e  1 0  b e s t  t a r g e t  areas 
(Fig. 4)  w e r e  s e l ec t ed  from t h e  f i r s t  group. Each t a r g e t  area 
corresponds t o  a c i r c u l a r  area on t h e  ground about 1 4  km (9 m i )  
i n  diameter o r  approximately 165 sq km ( 6 4  sq m i ) .  The 1 0  f i n a l  
t a r g e t  areas w e r e  broken down i n t o  t h r e e  orders  of p r i o r i t y  
(1, highest ,  etc.) based on the  complexity, type and s t r eng th  of 
t h e  i n t e r s e c t i o n s  and t h e  presence o r  absence of cu rv i l i nea r  o r  
circular fea tures .  Of these  c r i t e r i a ,  complex areas of i n t e r s e c t i o n s  
and i n t e r s e c t i o n s  of photo-lineaments with cu rv i l i nea r  o r  c i r c u l a r  
f ea tu re s  w e r e  f e l t  t o  be t h e  most important. 
786 
Target Area Evaluation 
A map of Colorado mineral  depos i t s  (2) w a s  used t o  eva lua te  t h e  
target areas. The loca t ion  of t h e  l a r g e r  mineral d i s t r i c t s  and 
t h e  se l ec t ed  t a r g e t  areas are shown i n  t h e  overlay i n  Figure 5. 
Most of t h e  annotated mineral d is t r ic ts  have produced over 
$100,000 i n  m e t a l s ;  however t h e  combined production of Climax, 
Leadvi l le  and Cripple  Creek has been over $ ,000,000,000 i n  
which have had production f igu res  over $1,000,000 include 
Breckenridge, Kokomo, A l m a ,  and Bonanza. Five of t h e  1 0  t a r g e t  
areas coincide with t h e  following mineral d i s t r i c t s :  Breckenridge, 
t h e  Leadville-Climax-Alma area (covered by one target area) , 
Tomichi, Bonanza, and Cripple  Creek. These r e s u l t s  were b e t t e r  
than expected, so t h e  inf luence of p r i o r  geologic knowledge of 
t h e  test area on t a r g e t  s e l ec t ion  w a s  t es ted .  
precious and base m e t a l s .  Other important k i n e r a l  d i s t r i c t s  
B i a s  i n  Target Select ion 
Copies of j u s t  t h e  lineament i n t e r p r e t a t i o n  w e r e  d i s t r i b u t e d  t o  
a test group of 15 Colorado School of Mines professors  and graduate 
s tudents .  After  being in s t ruc t ed  on t h e  basic assumptions made 
during t h e  se l ec t ion  of t h e  Phase I t a r g e t  areas ( those chosen 
i n  the first p a r t  of t h e  experiment),  each member of t h e  group 
w a s  asked t o  select 1 0  c i r c u l a r ,  14 kilometer-diameter target 
areas. Analysis of t he  test group's s e l e c t i o n s  (Phase I1 t a r g e t  
areas) showed a remarkably s t rong  agreement f o r  8 t a r g e t  areas, 
5 of which coincide with mineral d i s t r i c t s ;  4 of these 5 w e r e  
a l s o  picked during Phase I of the  experiment. The test group's 
successfu l  t a r g e t s  (i.e. coincidence w i t h  a mineral district)  
are tabula ted  and compared w i t h  the  successful  Phase I targets i n  
Figure 6. There is a f a i r l y  s t rong  agreement among members of 
t h e  tes t  group f o r  t h e  t a r g e t  areas t h a t  o u t l i n e  t h e  following 
mineral d i s t r i c t s :  t he  Leadville-Climax-Alma area, Tomichi, 
Monarch, Bonanza and Cripple  Creek districts. 
Statist ical  ana lys i s  w a s  used t o  evaluate  both t h e  test group's 
r e s u l t s  and t h e  method of t a r g e t  s e l ec t ion  used i n  t h e  experiment. 
The p robab i l i t y  of s e l e c t i n g  one successful  t a r g e t  area i n  t en  
tries by random process i s  .32; t h i s  value decreases t o  .01  f o r  
s e l e c t i n g  f i v e  successful  t a r g e t  areas. In  addi t ion ,  t he  p robab i l i t y  
of 5 people choosing t h e  same successful  t a r g e t  area by random 
process i s  a m e r e  1.4 X l m  The ana lys i s  was performed by 
placing a square g r i d  w i t h  t h e  approximate dimensions of a t a r g e t  
area (9-xg-mile squares) on t h e  lineament i n t e r p r e t a t i o n  and t h e  
mineral d i s t r i c t  overlays.  The p r o b a b i l i t i e s  were calculated 
assuming t h a t  t h e r e  are 1 2  chances f o r  a t a r g e t  area t o  coincide 
with a mineral d i s t r i c t  and t h e r e  a re  70 poss ib le  choices ( t a r g e t  
areas-squares) which coincide w i t h  photo-lineaments occurr ing on 
the overlay.  
787 
Analysis of t h e  test group's r e s u l t s  i nd ica t e  t h a t  bias had 
very l i t t l e ,  i f  any, e f f e c t  on t h e  se l ec t ion  of  t h e  Phase I t a r g e t  
areas, and suggests t h a t  some of t h e  mineral districts are defined 
by photo-lineament information. 
Photo-Lineaments and Mineral D i s t r i c t s  
To  determine what r e l a t ionsh ips  e x i s t  between mineral districts 
and photo-linears,  t h e  frequency of photo-lineament i n t e r s e c t i o n s  
w a s  p l o t t e d  using a computer program o r i g i n a l l y  designed t o  p l o t  
s te reonet  data i n  a form s u i t a b l e  f o r  contouring. The contoured 
p l o t  shows t h e  densi ty ,  o r  concentration, of a l l  types of i n t e r -  
s ec t ions  on t h e  photo-lineament overlay (Fig. 7 ) .  
The Cripple Creek d is t r ic t  i s  w e l l  defined by a high dens i ty  of 
lineament i n t e r s e c t i o n s ,  and t h e  Kokomo, Climax-Alma, Goldbrick- 
P i t k i n  and Tomichi d i s t r i c t s  a re  moderately-well defined. The 
Leadvi l le  and Bonanza districts w e r e  no t  discr iminated by t h i s  
method. It should be noted t h a t  t h e  Kokomo and Goldbrick-Pitkin 
d i s t r i c t s  do no t  coincide with t h e  previously-selected Phase I 
t a r g e t  areas, but  they are discr iminated by a high dens i ty  of 
photo-lineament in t e r sec t ions .  It is a l s o  i n t e r e s t i n g  t o  note  
t h a t  the 8 t a r g e t  a reas  t h a t  show good agreement among members of 
the  tes t  group, a l s o  coincide w i t h  areas having a high concentra- 
t i o n  of lineament in t e r sec t ions .  
SUMMARY 
A promising approach t o  t h e  se l ec t ion  of mineral explorat ion 
t a r g e t s  using ERTS imagery has been demonstrated. T h i s  study 
reduced an o r i g i n a l  search area  of 33,500 sq k m  (13,000 sq m i l e s )  
t o  t e n  165 sq km (64  sq m i )  reconnaissance t a r g e t  areas tha t  appear 
to have t h e  s t r u c t u r a l  r e l a t ionsh ips  commonly assoc ia ted  w i t h  
mineral izat ion i n  t h i s  region. Major mineral d i s t r i c t s  e x i s t  
i n  5 of the  10 t a r g e t  areas selected. In  addi t ion ,  t h i s  experiment 
shows a d e f i n i t e  co r re l a t ion  between some of the  major mineral 
districts i n  t h i s  p a r t  of Colorado and areas having a high dens i ty  
of photo-lineament i n t e r s e c t i o n s  as in t e rp re t ed  from ERTS imagery. 
CONCLUSIONS 
The  r e s u l t s  of  t h i s  experiment suggest t h a t  photo-lineaments on 
ERTS imagery are f r a c t u r e s  o r  f racture-control led f ea tu res  and 
tha t  their  d i s t r i b u t i o n  may be a guide t o  metallic mineral depos i t s  
i n  Colorado, and probably o the r  areas as w e l l .  Analysis of 
photo-lineament information contained on ERTS imagery can be a 
very valuable and inexpensive f i r s t  s t e p  i n  any mineral explorat ion 
program, e spec ia l ly  i f  it is used i n  conjunction w i t h  o ther  
sources of geologic information. Imagery acquired from space w i l l  
788 
probably prove most useful i n  areas of the  world i n  which less i s  
known about the geology. Moreover, t h e  favorable r e su l t s  of 
t h i s  study suggest that. those t a rge t  areas t h a t  do not correspond 
with known areas of mineralization may, i n  f ac t ,  be new t a rge t s  
for  m E 1  exploration i n  Colorado. 
ACKNOWLEDGMENTS 
Support for  t h i s  study w a s  provided by the Colorado School of 
Mines/ERTS project ,  funded by NASA Contract NAS5-21778. Apprecia- 
t ion  is  extended t o  D a n i e l  H. Knepper, Gary Rahes and D r s .  
Donald Sawatzky and Milton W i l t s e  for t h e i r  help and suggestions 
during t h i s  investigation, 
REFERENCES 
1. Ogden Tweto and P.K. S i m s .  Precambrian ancestry of t h e  
Colorado Mineral B e l t .  Geol. SOC. America B u l l . ,  v. 74,  
991-1014. 1963. 
2. J.W. Vanderwilt. Mineral Resources of Colorado, Plate 4. 
S ta te  of Colorado Mineral Resources Board, Denver, 547 p. 
1947. 
789 
*GRAND 
JUNCTION 
CANON * 
t 
Figure 1. Colorado index map. Geographic location of the ERTS 
imagery used i n  t h i s  investigation. 
790 
Figure 2 .  11 January 1 9 7 3  ERTS image 1172-17141-7. 
791 
Figure 3 .  Photo-lineament overlay. Sol id  l i n e s  are well-defined 
l i n e a r s ;  dashed l i n e s  are poss ib le  o r  moderately 
expressed l i n e a r s ;  dot ted l i n e s  are cu rv i l i nea r  o r  
c i r c u l a r  fea tures .  
792 
I I 
Location of t a rge t  areas selected on t h e  basis  of 
photo-linears. The p r i o r i t i e s  (1, highest, etc.) are 
indicated by the number next t o  each t a rge t  area. 
I 
Figure 4 .  
793 
Figure 5. Location of major mineral districts and selected t a r g e t  
areas. The small circles are i s o l a t e d  areas of mineral 
production, general ly  of low value. The l a r g e r  mineral 
d i s t r i c t s  ind ica ted  by a black dot  have i r r e g u l a r  
o u t l i n e s  and are annotated by an abbreviation: MZ- 
Montezuma, Br-Breckenridge, Ko-Kokomo, Cx-Climax, Al- 
A l m a ,  Lv-Leadville, S1-Sugarloaf, Tc-Tincup, G-P- 
Goldbrick-Pitkin, Tm-Tomichi, Mn-Monarch, BZ-Bonanza, 
CC-Cripple Creek, SC-Silver C l i f f ,  Ro-Rosita. 
794 
TEST GROUP RESULTS 
Figure 6. T e s t  group's s u c c e s s f u l  t a r g e t  areas. Each letter across 
the  top  corresponds t o  a member of tlie tes t  group. 
Coincidence of  a mineral d i s t r i c t  with a t a r g e t  area is 
ind ica ted  by t h e  let ter X. T h e  letter 0 i n  column P 
represents  t h e  successful  t a r g e t  area se l ec t ions  of Phase X. 
The last  column ind ica t e s  t h e  percent agreement f o r  
successful  t a r g e t  a reas  se lec ted  during Phase I and Phase I1 
of the  experiment. 
795 
Figure 7. Density of photo-lineament intersections and the loca- 
tion of major mineral districts. The numbers in the 
legend represent the number of photo-lineament inter- 
sections per unit area. 
796 


Mineral exploration with ERTS imagery

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server