432 



UNITED STATES MINERAL RESOURCES 



turing of an intense nature and of long dura- 

 tion (Rehrig and Heidrick, 1972). 



8. The deposits are associated with intrusives of a 



complex nature showing evidence of multiple 

 intrusion events (Wallace and others, 1968). 



9. Intense hydrothermal alteration of host intru- 



sive as well as of country rocks with an ac- 

 companying variety of accessory minerals is 

 a trademark of porphyry deposits (Vander- 

 wilt and King, 1955). 

 Using a combination of some of the geologic fea- 

 tures just described, we have estimated speculative 

 resources of molybdenum in and near the State of 



Colorado as an example. 



The known molybdenum occurrences in and near 

 Colorado occur in clusters that are shown in figure 

 52. These clusters of molybdenum deposits are 

 closely associated with areas of principal middle 

 Tertiary silicic intrusive activity. The molybdenum 

 occurrences and associated intrusives are spatially 

 related to major gravity lows, also shown in 

 figure 52. 



Three of the clusters of molybdenum occurrences 

 contain the major porphyry molybdenum deposits 

 at Henderson, at Climax, and at Questa. Some evi- 

 dence suggests that the other clusters shown may 



1.09° 



104° 



EXPLANATION 



c < 



-250 mil'ligals -300 milligals 



Bouguei gravity contours 



(from Woollaid and Joesting, 1964) 



s 



Limits of principal tertiary intrusive 

 activity 



o 



Cluster of known molybdenum occurrences 



Major molybdenum deposit 



I 



J I I I 



COL ORADO 

 new" MEXICO 



I 



J 



OKLAHOMA 



TEXAS 



Figure 52. — Map showing location of molybdenum resources in Colorado and northern New Mexico in relation to various 



geologic parameters. 



