Search USGS⌕ Search

Geology topics

N. P. Peterson

Publications and source records attributed to N. P. Peterson.

9 recordsLinked to original sources
USGS1962

Geology and ore deposits of the Globe-Miami district, Arizona

The rocks of the Globe-Miami district range from lower Precambrian to Recent. The oldest formation, the Pinal schist, comprises several varieties of schist formed by dynamic and thermal metamorphism of shale and feldspathic sandstone during the early Precambrian Mazatzal revolution. During the later stages of this revolution, the schist was intruded by a complex of dioritic rocks and by plutons of granite and quartz monzonite. There were extensive intrusions of a biotite-quartz diorite, known as the Madera diorite, mainly south of the district. In the northern part of the mapped area, the schist was invaded by an extensive mass, the Ruin granite, which is a coarse-grained rock most commonly of quartz monzonitic composition. There are also smaller sill-like masses of slightly gneissic muscovite granite.

Arizona↗
USGS1954

Copper cities copper deposit, Globe-Miami district, Arizona

The Copper Cities copper deposit in the Globe - Miami district , Arizona , is now in process of development. It is of the "porphyry" type and occurs in a body of quartz monzonite that has been intruded by smaller masses of granite porphyry. The hypogene sulfides are pyrite, chalcopyrite, and a very little molybdenite. Pyritic mineralization extends over a large area of which only a small portion contains an appreciable amount of chalcopyrite. The outcrop of the copper -bearing rock, roughly 1,800 feet square, is bounded on the west, north, and east sides by fault zones. The south boundary is gradational. The pyrite to chalcopyrite ratio of the protore increases rapidly with depth, whereas the copper content decreases but slightly. The ore body is a shallow chalcocite zone formed by supergene enrichment. Bodies of granite porphyry within the copper -bearing area were not as strongly mineralized by hypogene solutions as the quartz monzonite, and in them the chalcocite zone is thin, undoubtedly because the granite porphyry is less pervious to ground water than the quartz monzonite.

Arizona↗