The role of magmatic processes in the development of hypogene mineralisation at Quebrada Blanca, Northern Chile
Author(s)
Rowland, Matthew Gareth
Abstract
This thesis presents data relating to the intrusive lithologies, hydrothermal veins, and styles of alteration which record the evolution of the magmatic-hydrothermal system associated with the porphyry copper deposit of Quebrada Blanca, the most northern of such deposits of Late Eocene-Early Oligocene age in Chile. Data presented include field and petrographic observations. elemental and isotopic geochemistry of whole rocks and mineral separates, and microthermometric analyses of fluid inclusions. A comparison of these data with those reported for other porphyry copper deposits indicates that the components of the magmatichydrothermal system at Quebrada Blanca and their temporal relationships are typical of porphyry copper deposits in general. Analysis of data from Quebrada Blanca suggests that the evolution of the magmatichydrothermal system was driven by a series of processes in a sub-volcanic environment. There are two fundamental processes in this series: (I) Equilibration between a layer of magma at the base of a physically stratified felsic chamber and a melt volatile phase derived from a mafic magma; (2) Dyking of this layer of felsic magma upwards through the dominantly crystalline regions of the chamber. Hypogene mineralisation is bracketed by these two processes and is thought to be a product of equilibration between dominantly crystalline magma in the upper parts of the felsic chamber and volatiles sourced from the layer of felsic magma at the base of the chamber. Combined. the proposed processes form a genetic model for magmatic-hydrothermal systems associated with porphyry copper deposits and for the development of hypogene mineralisation. This model accounts more completely for the nature and interrelationships of the characteristic components of such magmatic-hydrothermal systems than previous genetic models. The model can be used to explain some of the variations displayed by magmatichydrothermal systems and so is of value both for the better understanding of existing deposits and in the exploration for new prospects.
Version
Open Access
Date Awarded
1999
Copyright Statement
Attribution-Non Commercial-No Derivatives 4.0 International Licence (CC BY-NC-ND)
Publisher Department
Department of Earth Science & Engineering
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)