43-101 2009 Technical Report On The San Antonio Project, Baja ...
43-101 2009 Technical Report On The San Antonio Project, Baja ...
43-101 2009 Technical Report On The San Antonio Project, Baja ...
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PEDIMENT GOLD CORP.Rock types of the area consist of various units of metamorphic crystalline rocks andnumerous intrusives.Diorite and GabbroDiorite and closely related gabbro are part of the older intrusive sequence with abundanthornblende or augite. <strong>The</strong>se rock units generally have a dark color due to high percentageof mafic minerals. <strong>The</strong> diorite and gabbro are usually coarse grained although some finegrained varieties have been observed in the La Colpa area. <strong>The</strong>se more mafic rock units arelocated only in the south part of the Colinas area and near the La Colpa mine area. Dioriteis common in the areas around Paredones Amarillos, Uvares, and Mirador.Biotite Hornblende Quartz DioriteBiotite Hornblende Quartz Diorite is part of a large batholithic mass ranging from gabbrothrough quartz diorite and granodiorite composition. This igneous mass covers a large areaeast of La Paz extending south beyond Todos <strong>San</strong>tos and possibly toward Cabo <strong>San</strong> Lucas.<strong>The</strong> intrusives of this mass are characterized by abundant hornblende and minor quantitiesof magnetite and commonly have illmenite as the dominant opaque mineral. Diorite of thiscomplex is the hangingwall rock type at Paredones Amarillos while the quartz diorite iscommon in both the hanging-wall and footwall of the Planes deposit. Las Colinas has a mixof diorite and quartz diorite in both the parts of the shear zone hosted deposit.<strong>The</strong> hornblende rich intrusive complex ranges compositionally from gabbro, to diorite, andhornblende quartz diorite which as stated above are intrusive into the metasedimentaryunits. Locally foliation is developed within the intrusive units which are cut by numerouspegmatitic to aplitic small irregular dikes. Coarse grained biotite hornblende quartz dioriteis the most common rock type present in the Planes deposit. A similar appearing coarsegrained weakly foliated biotite granodiorite is present in the Triunfo district, but it appearsto be a different intrusive complex with biotite the major mafic mineral.Hornblende from the hornblende gabbro near Paredones is radiometric age dated at 129 ma(plus or minus 5ma) (Brown, et. al 1998) Age dating by Carrillo-Chavez et al. (1999) alsoreport the coarse grained gabbro, diorite-quartz diorite rocks range in age from 130 to 140ma as determined by testing of the abundant igneous hornblende. Both the Valle Perdidobatholith and the Triunfo batholith intrude those older hornblende bearing igneous rocksthat are about 30 to 50 million years older. <strong>The</strong> aplite and pegmatitic dikes found only inthe hangingwall blocks appear to be derived from the Valle Perdido granite batholithlocated somewhat deeper. <strong>The</strong> dikes, however, are not present in the Valle Perdidobatholith.Biotite Granodiorite-Granite (Valle Perdido Batholith and Smaller Bodies)Biotite Granodiorite-Granite is present as a medium grained quartz rich intrusive beneaththe Planes deposit and is seen mainly in the drill holes which penetrate deeper into thehanging-wall of the large thrust fault shear zone. <strong>The</strong> intrusive has a weakly porphyriticcharacter with fine grained biotite of a brownish coffee color in drill holes. Rocks of similar