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Magmas, ore deposits and geodynamic evolution at a convergent margin: the case of Ecuador

English title Magmas, ore deposits and geodynamic evolution at a convergent margin: the case of Ecuador
Applicant Chiaradia Massimo
Number 117616
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geochemistry
Start/End 01.10.2007 - 30.09.2009
Approved amount 128'280.00
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Keywords (9)

Ecuador; adakite; calc-alkaline; porphyry-Cu; epithermal; gold; copper; geochronology; isotopes

Lay Summary (English)

Lead
Lay summary
Porphyry-Cu±Au and associated epithermal deposits reflect a local and transient concomitance of magmatic, hydrothermal and tectonic processes at convergent margins. Recent studies show that porphyry-Cu/epithermal mineralization could be preferentially associated with so called adakitic magmas (e.g., characterized by high Sr/Y and low Yb). Nevertheless, the temporal relationship between adakitic rocks and mineralization is unclear. Additionally, there is no general consensus about the origin of adakites (slab melting or deep evolution of mantle-derived magmas?), although there is agreement about the fact that the onset of adakitic magmatism is related to a major geodynamic change (slab break-off, lithospheric delamination, crustal thickening, subduction of hot oceanic lithosphere, flat subduction), which might also have a major impact on the formation of porphyry-Cu/epithermal deposits.

In Ecuador the largest concentration of porphyry-Cu-Au and epithermal deposits is associated with dominantly normal calc-alkaline rocks formed between 30 and 9 Ma (current lack of radiometric dating precludes a better definition of the younger temporal limit). Formation of porphyry-Cu and epithermal deposits (except Quimsacocha: 5.3 Ma?) virtually ceases after about 9 Ma roughly in coincidence with the widespread onset of adakitic volcanism.

The apparent extinction of mineralization after ~9 Ma in concomitance with a geochemistry switch from normal calc-alkaline to adakitic volcanism deserves a thorough investigation because that can shed light on the relationship between adakitic rocks and porphyry-type mineralization.

The goals of this project are:

(i)Reconstruct geochemical evolution of Tertiary magmatic centers associated with major mineralization of Ecuador and the transition to the “barren” (?) adakitic volcanism using geochronological, geochemical and isotope tracing tools.
(ii)Correlate such geochemical evolution to the geodynamic evolution of Ecuador.
(iii)Explore the relationships between changing magma chemistry, which ultimately results from a changing geodynamic regime, and the formation of ore deposits.
(iv)Determine the origin of the adakitic signatures of Tertiary and recent magmatic rocks of Ecuador.

This study will contribute to understand the relationships between metallogeny, adakitic magma chemistry and geodynamic evolution at convergent margins. Results of this project may also provide new tools for the exploration of porphyry-Cu and epithermal deposits based on the geochemistry of the associated magmatic rocks and on geodynamic changes.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
126896 Magmas, ore deposits and geodynamic evolution at a convergent margin: the case of Ecuador 01.01.2010 Project funding
109626 Magmas, ore deposits and geodynamic evolution at a convergent margin: the case of Ecuador 01.10.2005 Project funding

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