Heterogeneous altered breccia

From Pontifex Report No. 9884. March 31st, 2011 Heterogeneous and weakly schistose, sericite-hematite-quartz altered fine fragmental facies with scattered small quartz grains, minor diffuse leucoxene and trace zircon grains. Could be interpreted as acid volcanic breccia or tuff, but poor textural preservation makes this difficult to distinguish from sheared, altered metasediment, albeit perhaps volcaniclastic. Sample is a heterogeneous and weakly schistose, sericite-hematite-quartz altered fine fragmental facies with scattered small quartz grains, minor diffuse leucoxene and trace zircon grains. Could be interpreted as acid volcanic breccia or tuff, but poor textural preservation makes this difficult to distinguish from sheared, altered metasediment, albeit perhaps volcaniclastic. Visually estimated mineralogy. Mineral Abundance Origin/Location Sericite ± extremely fine quartz Dominant. Pervasive alteration, poorly defining a fine foliation matrix, also more concentrated in small scattered fragments. Earthy hematite Subordinate Staining throughout, locally concentrated in lenses or fragments. Quartz sand size grains Minor Disseminated through matrix and as angular to rounded grains in small fragments. Leucoxene Trace Ex oxide and diffuse Zircon Trace Inherited accessories 0.1mm Carbonate and sericite Sparse In microfractures These rock chips are dominated by variable concentrations of sericite and earthy hematite, partly forming a fine foliated matrix, also more concentrated to poorly define elliptical or irregular probable fragments to 8mm long. Some fragments lack inclusions and may represent altered volcanic glass. Other fragments contain angular quartz small grains, subangular to rounded, some vaguely rectangular patches of sericite that could represent completely altered feldspar microphenocrysts. Sparse lamellar sericite could represent small flakes of mica, possibly biotite. Rare small quartz grains have embayed margins. Minor leucoxene is dispersed and occurs in some fragments and there are rare zircon grains about 0.1mm in size.