Beitrag
Source Rocks and the Genesis of Metallic Mineral Deposits
Doe, Bruce R.
Global Tectonics and Metallogeny Volume 4 Number 1-2 (1991), p. 13 - 20
32 Literaturangaben
veröffentlicht: Jan 1, 1991
ArtNo. ESP136000401001, Preis: 19.00 €
Abstract
Although the processes by which certain natural resources such as oil and gas, phosphorite, and sandstone uranium are formed are reasonably well understood, there is little understanding about the importance of source rocks in metallic sulfide ore deposits. The time has come to begin clearing up this mystery. Anion sources must be considered in addition to metal sources. Why are there Cretaceous copper porphyry deposits in Arizona, but Tertiary molybdenum porphyry deposits in Colorado and northern New Mexico, for example? Perhaps the deepsource material for the porphyries generating the porphyry copper deposits was depleted in extractible copper in the Cretaceous and was not available during Tertiary igneous activity. It is less clear why Laramide igneous activity in Colorado did not lead to the formation of molybdenum porphyry. The source material for porphyries and other igneous rocks is rarely available for study. It is noted that the oldest basement rocks in Wyoming were already uranium rich in Archean rocks, but the oldest rocks in Colorado, Proterozoic rocks, were not. Large uranium sandstone ores are found in Wyoming but not in Colorado. It is proposed that geochemical blocks might exist where geochemical anomalies in older rocks may be a clue to the presence of ore in younger rocks - the geochemical block hypothesis. The hypothesis is testible and worthy of further consideration.
Schlagworte
Metallic Mineral Deposit • Source Rocks • Cretaceous • copper