Control of Shear-Zone-Induced Pressure Fluctuations
on Gold Endowment: The Giant El Callao District,
Guiana Shield, Venezuela
Author
dc.contributor.author
Velásquez, German
Author
dc.contributor.author
Salvi, Stefano
Author
dc.contributor.author
Siebenaller, Luc
Author
dc.contributor.author
Béziat, Didier
Author
dc.contributor.author
Carrizo, Daniel
Admission date
dc.date.accessioned
2019-05-31T15:21:00Z
Available date
dc.date.available
2019-05-31T15:21:00Z
Publication date
dc.date.issued
2018
Cita de ítem
dc.identifier.citation
Minerals, Volumen 8, Issue 10, 2018, Pages 1-21
Identifier
dc.identifier.issn
2075163X
Identifier
dc.identifier.other
10.3390/min8100430
Identifier
dc.identifier.uri
https://repositorio.uchile.cl/handle/2250/169473
Abstract
dc.description.abstract
The El Callao district, with a total endowment of more than 2000 t Au, is considered to be the
most prolific gold resource in Venezuela. Mineralization is hosted by a vein system that is genetically
associated with the El Callao transpressional shear zone. This vein system consists of a network of
interconnected quartz–albite–ankerite veins enveloping a large number of metabasaltic fragments
that host gold-bearing pyrites. Based on detailed mineralogical, microstructural, and fluid inclusion
studies, a pressure-temperature pathway was established for the evolution of the mineralizing
fluid during shear-zone development and exhumation. This path is characterized by repeated
episodes of fluid pressure fluctuation from lithostatic (higher than 1.6 kbar) to near-hydrostatic values
(<0.4 kbar), recorded throughout the transition from the quasi-plastic to frictional deformation
cortical domains. Each successive pressure drop induced boiling of the hydrothermal fluid,
with the resulting fluid phase separation controlling: (i) pyrite and invisible gold crystallization,
which occurred during ductile and ductile-brittle transition strain conditions, and (ii) primary gold
remobilization with consequent native-refined gold precipitation, occurring mainly under brittle
conditions. The metallogenic framework that was proposed for the El Callao shear zone can be
used as a vector to explore and characterize other mineralized shear zones in the Guiana Shield and
analogous orogenic systems worldwide.