Citation
Ruíz García, Casilda and Arribas Moreno, Antonio
(2002).
Mineralogy and geochemistry of the Masa Valverde blind massive sulphide deposit, Iberian Pyrite Belt (Spain).
"Ore Geology Reviews", v. 19
(n. 1-2);
pp. 1-22.
ISSN 0169-1368.
https://doi.org/10.1016/S0169-1368(01)00037-3.
Abstract
Masa Valverde is a blind, volcanic-hosted massive sulphide deposit recently discovered in the Spanish sector of the
Iberian Pyrite Belt (IPB). The deposit is more than 1 km long and is located at depths between 400 and 850 m, in direct
spatial association with a residual gravimetric anomaly. The ore body is concealed beneath Culm sedimentary rocks which
cover the westem extension of a Hercynian age anticline, a few kilometers west of an area where older massive sulphide
workings existed. The Masa Valverde deposit consists of two main ore bodies composed dominantly of massive and banded
pyrite which are hosted by a volcano-sedimentary sequence made up of felsic tuffs interlayered with shale, siliceous exhalite
and radiolarian chert. The abundance of sedimentary host rocks to the deposit is a feature shared by other large massive
sulphide deposits in the eastem sector of the IPB and is interpreted as significant with respect to the origin of the deposit (a
break in volcanic activity). The thickness of the upper massive sulphide orebody varies between a few meters and 70 m, and
it consists of lenses and blankets of massive sulphides with interbedded tuff and shale and occasionally stockwork zones.
The lower orebody is smaller and thinner than the upper one, but this may be due to incomplete drilling. Two types of
stockwork occur beneath the massive sulphide bodies, the more common type consists of irregular and anastomosing
sulphide veinlets and irregular blebs formed by replacement. Stockwork with cross-cutting, generally straight-sided, sulphide
veins is, by contrast, suggestive of formation by hydraulic fracturing. The mineralogy and alteration processes of the ore and
host rocks at Masa Valverde are analogous to those of other IPB massive sulphides.