43-101 2007 Technical Report On The San Antonio Project, Baja ...

Derry, Michener, Booth & Wahl Consultants Ltd. Page 217.2 Local and Property GeologyMel Herdrick, V.P. Exploration and a director of Pitalla, has provided the following description:“Geology in and around the gold deposits is determined from the drilling because of sand andgravel pediment cover. The deposits are contained in a large mega shear structure, possibly aMesozoic age thrust fault dipping about 45 degrees westerly. This mega-shear appears to beregional in extent, with strands and splays that may have been more favourable formineralization, which coalesce in one zone at Planes. (Figure 7.2)However the drilling at Planes and Colinas shows the thickness of the shear zone to be more than200 metres hosted in mid-level intrusive rocks of similar age to the shearing episode. This, andthe presence of the structure for 40 km to the south, suggest more likely that the shear zone is athrust fault related structure. Drilling at Planes has shown a very thick shear zone often with achange from coarse grained biotite-hornblende quartz diorite in the hangingwall to a fine tomedium grained biotite granodiorite in the footwall. In the Colinas deposit, diorite to gabbro isfound irregularly in both hangingwall and footwall parts of the mega-shear zone. The strikelength of the shear zone through both Planes and Colinas is about 3 km, with mapping by EchoBay indicating extension at least several km more to the south.Drilling has also revealed that a small northwest trending graben basin, probably Pleistocene age,with true listric faulting drops the northeastern part of the Planes deposit in domino like faultsegments to sequentially more than 200 metres deeper to the northeast. Geophysical workconsisting of both limited gravity and IP lines has been completed to determine the local extentof deeper parts of this basin. Sediment filling associated with the pediment development of thearea consists of mainly sandy gravel produced by weathering breakdown of the localgranodiorite and quartz diorite igneous rocks. Possibly this basin is still structurally activedropping in recent time. The top surface of the pediment has numerous scattered cobbles andoccasional boulders, which appear to have been moved by erosion from further west, whereschist and gneiss are more common. In several geological reports of the region the formal namefor this young basin filling is Salada Formation. (Aranda-Gomez and Perez-Venzor, 1989)Surface oxidation of the sulphide bearing deposits has progressed to about 100 metres in thePlanes deposit and about 25-30 metres in the Colinas deposit. It is reported that the Paredonesdeposit further south has only about 5-10 metres of oxidation. The reason for the depth ofoxidation being greater at Planes is probably due to several causes. One is the covering of thedeposit by pediment that removed it from active erosion. Much of the oxidized material is verysoft due to the leaching of sulphides and probably would have eroded easily if exposed. Secondfactor in the depth of oxidation is the breakage of the deposit by the young listric faultingepisode associated with the graben basin formation. The faulting opened the rock to moreoxygen carried by sub-surface waters with a deeper water table flow route developed.”