Hat Project Regional Geology Setting;
The Hat Property is situated immediately east of the Coast Range in Stikine Terrane of the Intermontane Physiographic Province. Mineralization occurs in volcaniclastic rocks of Upper Triassic age and in younger dioritic and gabbroic intrusions. Volcanic flows of Tertiary age cover parts of the property. Sheared and altered portions of the host rocks contain the principal minerals: chalcopyrite, pyrite and magnetite. Mineralization is accompanied by chlorite, epidote and a distinctive red feldspathic alteration. Gold is an important component but is not visible.
Hat Property Geology and Metallogeny:
Doubleview’s geological team, as part of an ongoing study of the Hat gold-copper alkalic porphyry deposit, is continually updating its geologic model. Exploration of the newly discovered “Lisle Zone” mineralized area in Northwest British Columbia is in the early stages of drilling to determine its geologic characteristics and to locate its boundaries. Along with a focus on that Zone, work has continued in order to better define and prioritize numerous anomalous areas that have similar but untested characteristics. Methods incorporates the application of data from the Company’s large database of various technical surveys and extrapolation of information from drill holes. The current study includes entry of data from more than 2200 samples into a large GIS Database (Geographic Information System) (Figure 1) that was then tested by a variety of modeling methods, including application of simple “Fuzzy Logic”-type routines to extract specific information, such as sulphide occurrences, or alteration types. Working with this database has given new perspectives of the geological potential of the Hat Property.
The Hat project lies in Stikinia terrane at the western edge of the Intermontane physiographic province, proximal to the Coast Crystalline Belt. Dominant rock types are related to the Stuhini formation, a volcaniclastic unit of Upper Triassic age that is similar to the Nicola and Takla Group rocks elsewhere in British Columbia and Lewes River Group in Yukon. Various granitic plutons are outliers of Coast Intrusions and regional structural styles conform to northwesterly Cordilleran trends. Tertiary and younger volcanoes that occur along a northerly alignment have resulted in large areas of flat-lying basaltic lavas that, along with extensive glacial till and outwash deposits, obscure underlying formations and frustrate mineral exploration.
Although most of British Columbia’s copper porphyry deposits are located in central “Quesnellia” terrane, a north-trending belt of intermediate volcaniclastic rocks that extends northerly through the length of the province, “Stikinia” terrane, with similar characteristics but is less explored, is host to several active mines and numerous properties that are either awaiting development or re-activation. In both terranes most deposits are closely related to dioritic and granodioritic plutons of Early- to Mid-Jurassic age.
Although northwestern British Columbia is endowed with a significant number of base metal deposits, the recently inaugurated Red Chris copper-gold mine is the only mine presently in production. Several historic mines are now closed or inactive and several properties have entered the permitting phase. Many deposits with realistic potential to achieve production are located within 200 km of the Hat deposit. Of particular note are the huge KSM-Pretium copper-gold-silver-molybdenum resources, the rich Galore Creek copper bodies, the very large Copper Fox, aka Schaft Creek, copper-molybdenum deposit, the above-noted, recently started Red Chris mine and the now-depleted very high-grade Eskay gold and silver mine. A large number of junior mining companies are active throughout the Northwest and it continues to be the most active exploration area of the Province. It appears certain that northwest BC is destined to become a very important mining area that will ensure the future of mining in B.C.
The overall shape and dimensions of the Lisle Zone, discovered by Doubleview in 2014, have not yet been defined but, on the basis of available drill hole data extends horizontally in excess of 900 metres and vertically to depths of at least 350 metres from surface. Gold content is closely related to copper values and commonly ranges from 0.1 to 2 grams/tonne, with copper from 0.2 to 1.5%. Drill hole H-11 returned 451 metres with 0.17 g/tonne gold and 0.22% copper and hole H-23 that intersected the Zone at greater depth returned 110 metres with 0.36 g/t gold and 0.47% copper. The outside dimensions, thickness and overall metal content of the Lisle Zone have not been determined and an apparent increase in metal values with depth has not been confirmed.
Hat Project Geological Framework:
Geologically speaking, the Hat complex is represented by andesitic volcanic and volcanoclastic rocks of late-Triassic Stuhini formation intruded by multi-phase dioritic and gabbroic intrusions, thought to be of early Jurassic age. The intrusions evolved to form significant sub-alkaline suite porphyry copper-gold systems and the porphyry intrusions and related hydrothermal fluids resulted in strong alteration footprints. The known Lisle zone porphyry copper-gold system as well as Hat property Anomalies A, E, C, D and the “Hoey” zones remain open in all directions and continued to be investigated during the exploration and drilling programs.
Magnetic Survey, Deposit and Porphyry Outline:
Porphyry copper deposits often, but not always, appear as magnetic highs, with alteration halos usually manifested as annular (donut-shaped) or open-ring peripheral magnetic lows (Heithersay and Walshe, 1995; Ford and others, 2007). Typically, there is significant variability in magnetic susceptibility throughout the altered rock owing to the nonhomogeneity of phyllic alteration-related magnetite destruction and late-stage magnetite formation (Gettings, 2005). [Preliminary Model of Porphyry Copper Deposits, USGS – Open-File Report 2008–1321 ]
Figure 1 illustrates detailed ground magnetic intensity of the Hat Porphyry system with observed sulphide mineral occurrences. The magnetic survey has been analyzed as a part of company’s update of its expanded Hat Project database.
Figure 2 shows an interpretation of the magnetic signatures.