| Summary: | Hydrothermal alteration on the Hank property, northwestern British Columbia, is hosted
by andesitic to basaltic volcaniclastic breccias, flows and sills of the Upper Triassic Stuhini Group;
Lower Jurassic sedimentary rocks; and, a hypabyssal, Middle Jurassic (185±3 Ma) potassiumfeldspar
megacrystic porphyry which intrudes the stratified rocks. Alteration on the property
forms two sub-parallel northeast trending zones (Upper and Lower alteration zones) which are
capped by broad tabular zones at higher elevations (Felsite Hill and Rojo Grande).
The lower alteration zone (LAZ) strikes northeasterly and dips steeply to the southeast
cutting the stratigraphy on the property and is characterized by intense illite-dominant alteration.
The pit area of the Upper alteration zone (UAZ) is semiconformable to stratigraphy, strikes
northeast and dips moderately to the southeast. The pit area of the UAZ is hosted within
volcaniclastic breccias with footwall and hanging wall defined by flows or sills. Alteration is
characterized by illite/smectite which grades into illite/smectite+kaolinite-dominant alteration near
the top of the zone. Above the UAZ, alteration comprises kaolinite-dominant alteration
containing minor natroalunite within the volcanic and overlying sedimentary sequences. This
transition from illite/smectite to kaolinite-dominant alteration is marked by a zone of intense,
multiphase silicification dipping gently to the south.
Alteration mineralogy on the Hank property is characteristic of a near-surface, lowsulphidation
epithermal environment dominated by illite alteration at depth and illite/smectite and
kaolinite alteration at higher elevations. The overall morphology of these alteration zones
suggests that the LAZ is a conduit for hydrothermal fluids which cuts stratigraphy. The UAZ,
and the Flats Zone (FZ) are semiconformable to stratigraphy, indicating lateral movement of
hydrothermal fluids along a permeable horizon outward from the central conduit. The silicified
zone, which lies above the UAZ, may indicate a zone of increased permeability or the presence of
a paleo-water table or aquifer. Above the silicified zone, tabular zones of kaolinite-dominant
alteration reflect the upper parts of an epithermal environment, derived from acidic, vapour
condensate above the paleo-water table. Illite/smectite alteration within the potassium-feldspar
megacrystic porphyry suggests that it intruded during the final stages of hydrothermal activity and
may be the causative intrusion.
Alteration and mineralization on the Hank property represents one extreme of a
continuum of mineralization styles throughout the Iskut River area including porphyry, vein and
exhalative examples, all co-temporal with Middle Jurassic intrusions.
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