Bell Copper Discovers Advanced Argillic Alteration in New Breccia Pipes at Sombrero Butte
--------------------------------------------------------------------------------
Vancouver, B.C.: Bell Copper Corporation ("Bell Copper" or the "Company") (TSX-V Symbol: BCU) is pleased to report that on the basis of recently completed fieldwork, the Company has expanded its landholdings at the Sombrero Butte project near Tucson, Arizona. The new claims add 9 newly identified breccia pipes to the project. These new breccia pipes include a cluster of five which contain Dickite in advanced argillic alteration. Breccia pipes with Dickite in advanced argillic alteration are significant as indicators of potentially large economic porphyry copper systems in the subsurface. The following excerpt is from a technical paper on the geology of the Resolution deposit also located in this region of Arizona (citations are provided):
"The upper kilometer of the deposit, pervasively sericitized and with abundant pyrite and later bornite-chalcocite, is overprinted by advanced argillic alteration with kaolinite, dickite, and less alunite, topaz, pyrophyllite, and zunyite. The vein-controlled, high sulfidation assemblage pyrite + chalcocite correlates most strongly with advanced argillic alteration and copper grades greater than 10%. Deposits sharing features seen in the upper portions of the Magma porphyry include some of the world's largest copper deposits (e.g. Butte and Chuquicamata). The discovery of this style of porphyry ore in the southwestern US should serve as an incentive for renewed exploration efforts there."
Sandra Troutman, Advanced argillic alteration in the deeply buried Magma Porphyry Cu-Mo prospect, Superior, Arizona, Abstract from SME Meeting, 2002
The newly discovered group of breccia pipes is of particular interest because of the distribution of advanced argillic alteration occurring within the breccia matrix. Advanced argillic alteration of five of the breccias is indicated by the presence of translucent blue-green Dickite (Al2Si2O5(OH)4) forming the breccia matrix. Dickite is an alumino-silicate clay that forms at temperatures of 150°-270°C under very acidic conditions. Positive identification of the Dickite was made using a PIMA infrared spectrometer as well as a Thermo Nikolet Almega microRaman spectrometer at the University of Arizona RRUFF laboratory.
Dickite and other minerals characteristic of advanced argillic alteration have been found in several other high grade, major porphyry copper systems, including Resolution, Bisbee, and San Manuel, all well known copper deposits located in the Laramide porphyry copper belt in Arizona (San Manuel is 19 kilometers west of Sombrero Butte). In addition to these localities, Dickite has also been recognized throughout the world in major deposits such as Oyu Tolgoi in Mongolia, Butte, Montana, Cananea, Mexico, and El Salvador, Chile. In these deposits, Dickite is associated with high grade copper minerals such as digenite, chalcocite, and bornite.
X-ray fluorescence analyses of iron oxide minerals in the dickite-bearing breccias show anomalous copper, molybdenum, and arsenic. This area also contains younger porphyry intrusions, abundant tourmaline, and sericitic alteration of the porphyry intrusions.
No evidence has been found of previous drilling in any of the dickite altered breccia pipes. Fieldwork will continue in order to develop a better understanding of these new breccia pipes and to formulate the phase III drilling program at Sombrero Butte, which will focus on this area of advanced argillic alteration.
Fieldwork for 2008 involves continued geologic mapping, surface geochemistry, stream sediment sampling and surface geophysics followed by diamond drilling in the 3rd Quarter of 2008.
