of Rangin (1982), or Morro Hermoso Member] crossed by diabase dykes, with an interbedded sedimentary unit containing a Tithonian fauna in their upper part (Rangin, 1982); (ii) a 2500 m thick sequence of graywacke
, claystone and conglomerate with poorly rounded volcanic pebbles, interbedded calcareous strata and pyroclastic deposits and, in its lower part, some interbedded basalt flows establishing its continuity with the underlying Morro Hermoso Member.
Descripcion: Constituida por interestratificaciones de lutitas y areniscas (areniscas y graywackes
liticas), con laminacion paralela, cruzada, bidireccional, posibles briozooarios y globigerinoides, con fuerte influencia volcanica (clastos de rocas volcanicas: 3-70%, mayoritariamente alrededor de un 60%).
Pyrargyrite probably does not occur in the Llallagua stock, but it was an ore mineral with galena in a peripheral vein in graywackes
at Uncia, 3 km south of the intrusion.
This fault dips approximately 35 degrees to the northeast, and brings the Mesozoic sediments and Tertiary volcanics into contact with older, underlying shales, graywackes
and mafic volcanic rocks.
1) could be summarized as a basement of Upper Precambrian age which crops out in the center of the Olivenza-Monesterio anticlinorium, formed by successive levels of schists, graywackes
, shales and graphitic quartzites affected by a low-grade regional metamorphism (Benito et al.
The rocks exposed at the Hale Creek mine are typical of the Franciscan-Knoxville group of late Jurassic age and consist of sandstones, shales, cherts, greenstones and graywackes