Original paper

A porphyry-type Mo-Cu discovery at Granite Mountain, Nevada: Predictions based on mineralogical and geochemical study of zoning

Bowes, William A.; Kutina, Jan; Aaker, S.K; Fredriksson, Kurt; Golightly, D.W.

Global Tectonics and Metallogeny Volume 1 Number 4 (1982), p. 402 - 439

3 references

published: Dec 1, 1982

BibTeX file

ArtNo. ESP136000104002, Price: 19.00 €

Download preview PDF Buy as PDF


The mineral potential of an intersection of deep-seated fracture zones in NW-Nevada, occurring above a major eastwest trending structural boundary in the upper mantle, was examined. A discovery of porphyry-type Mo-Cu mineralization was made in the central part of the intersection, in the Kennedy District of Granite Mountain in Pershing County. The spatial position of the discovery area is corroborated by major geophysical anomalies, as surveyed by Phoenix Geophysics Ltd. (P.G. Hallof, this issue). The mineralized area occurs in and around a stock of a monzogranite to granodiorite composition and is about 2'12 miles (about 4 km) long, the copper and molybdenum concentrations followed outward by zoning with zinc, lead, silver and, locally, gold. The main concentration of molybdenum and copper, so far detected, is associated with an apophysis of monzogranodiorite which intruded into a complex of dioritic and gabbroic rocks (pyroxene-biotite monzogabbro and hornblende-biotite quartz monzodiorite). Very extensive K-metasomatism was superimposed on the diorite-gabbro rock complex, causing further "monzonitization " of these rocks. Chloritization and argillitization of monzogranodiorite increases with increasing depth and is associated with a higher concentration of molybdenite. The deepest parts of the 870 ft. deep drillhole K-101 show a porphyry development of the monzogranodiorite and an increase in the total SiO, content. The SiO, and K,O contents of these rocks correlate with the composition of the porphyry rocks from some molybdenum stockwork deposits. The area under study appears favorable for the occurrence of larger concentrations of metals, in particular molybdenum. Deeper drilling is recommended.


Nous avons examine Ie potentiel minier d'une intersection de zones de fractures profondes au N-W Nevada, situee au dessus d'une discontinuite majeure Est-Ouest dans Ie manteau superieur. Une mineralisation de type «Mo-Cu porphyry » a ete decouverte dans la partie centrale de la zone d'intersection qui appartient au Kennedy District de Granite Mountain, dans Ie Pershing County. Par son emplacement, ceUe decouverte correspond a une zone d'anomalies geophysiques majeures detectee par Phoenix Geophysics Ltd. (P.G. Hal lof, meme volume). La zone mineralisee, mesurant environ 2.5 miles (environ 4 km) se situe autour et dans un «stock» de composition monzogranite a granodiorite, et contient les principales concentrations en cu ivre et molybdene, auquelles succede vers I 'exterieur, une zone a plomb, zinc, argent et anomalies locales en or. Les concentrations principales en molybdene et cuivre detectees jusqu' a present, sont associees a une apophyse de monzogranodiorite formant une intrusion dans Ie complexe des roches dioritiques et gabbroiques (monzogabbro a pyroxene-biotite et quartz monzodiorite a hornblende-biotite). Le roches du complexe diorite-gabbro ont subi un tres important metasomatisme du potassium, causant une «monzonitization » accrue de ces roches. La chloritisation et I 'argilisation de la monzogranodiorite croit en profondeur et est associee a une concentration accrue en molybdenite. Les portions les plus profondes du sondage K-1 01 de 870 pieds (265 m) de profondeur, montrent un developpement porphyrique de la monzogranodiorite et un accroissement en Si02. Les concentrations en Si02 et K20 de ces roches correspondent aux compositions des roches porphyriques de certains depOts «stockwork» de molybdene. La zone couverte par I'etude apparait favorable a I'origine de concentrations plus importantes de certains metaux, en particulier molybdene. Un sondage plus profond est recommande.


porphyry coppergranite mountainnevadausageochemical zoning