Controls on supergene enrichment of porphyry copper deposits in the Central Andes: A review and discussion |
| |
| Authors: | Adrian J Hartley Clive M Rice |
| |
| Institution: | (1) Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, AB24 3UE, UK |
| |
| Abstract: | The Central Andes host some of the world’s largest porphyry copper deposits. The economic viability of these deposits is dependent
on the size and quality of their supergene enrichment blanket. Published models that have strongly influenced exploration
policy suggest that supergene enrichment ceased at 14 Ma due to an increase in aridity. Here we discuss these models using
published geochronological, geomorphological and geological data. Geochronological data indicate that supergene oxidation
and enrichment has been active between 17 and 27°S across the forearc of northern Chile and southern Peru from 44 to 6 Ma,
and on the Bolivian Altiplano and Eastern Cordillera of Argentina from 11 Ma to present. There is evidence for cessation at
20, 14 and 6 Ma. However, a major problem is that as more geochronological data become available the age ranges and periods
of enrichment increase. This suggests that the full spectrum of enrichment ages may not have been sampled. The relationship
between supergene enrichment and the age of regional pediplain surface development is not well constrained. Only in two areas
have surfaces related to enrichment been directly dated (southern Peru and south of 26°S in Chile) and suggest formation post
14 Ma. Sedimentological data indicate that a fluctuating arid/semi-arid climate prevailed across the Atacama Desert until
between 4 and 3 Ma, climatic conditions that are thought to be favourable for supergene enrichment. The balance between uplift,
erosion, burial and sufficient water supply to promote enrichment is complex. This suggests that a simple model for controlling
supergene enrichment is unlikely to be widely applicable in northern Chile. General models that involve climatic desiccation
at 14 Ma related to rainshadow development and/or the presence of an ancestral cold-upwelling Humboldt Current are not supported
by the available geological evidence. The integration of disparate sedimentological, geomorphological and supergene age data
will be required to fully understand the controls on and distribution of supergene oxidation and enrichment in the Central
Andes. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
