| Autor: |
Quang, Chan X., Clark, Alan H., Lee, James K. W., Hawkes, Nicholas |
| Předmět: |
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| Zdroj: |
Economic Geology & the Bulletin of the Society of Economic Geologists; Jan/Feb2005, Vol. 100 Issue 1, p87-114, 28p, 1 Color Photograph, 4 Diagrams, 5 Charts, 5 Graphs, 5 Maps |
| Abstrakt: |
The Jurassic to middle Eocene porphyry copper deposits and prospects exposed on the Pacific slopes of the central Andean Cordillera Occidental of southern Perú between latitudes 16°30′ and 18° S record a protracted, ca. 30-m.y. history of supergene processes that were fundamentally controlled by the evolving local geomorphologic environment, itself a response to successive regional tectonic events, including the late Eocene Incaic, the late Oligocene to earliest Miocene Aymargt, and the middle to late Miocene Quechuan events. Weathering of the porphyry centers also overlapped temporally with the local resumption of arc volcanism in southern Pert1 at 25.5 Ma following a 27-m.y. amagmatic interval, and supergene processes were variously interrupted or terminated by ignimbrite blanketing, although in several locations supergene profiles were preserved by such cover. The landform chronology for the area surrounding the Cuajone, Quellaveco, and Toquepala deposits (ca. 17° S) is revised and extended northwestward through field mapping to the Cerro Verde-Santa Rosa district (ca. 16° 30′ S). The 40Ar-39Ar incremental-heating dates of supergene alunite group minerals from the Angostura (38.1 and 38.8 Ma) and Posco (38.8 Ma) prospects and the Cerro Verde deposit (36.1-38.8 Ma) demonstrate that supergene processes were underway in the late Eocene beneath a subplanar topography resulting from uplift and erosion during the Incaic orogeny, now represented by a regional unconformity in the Cenozoic volcanic-sedimentary rock succession. Broadly contemporaneous supergene processes were probably active in the Cuajone-Quellaveco-Toquepala district. Slow erosion and the accumulation of clastic sediments through the tectonically quiescent early to mid-Oligocene are envisaged to have caused a rise in the water table and the widespread preservation of the Incaic supergene profiles. Aymará uplift subsequently led to the... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
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