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Date Permissions Signed
Date of Award
Master of Science (MS)
Brown, Edwin H.
Babcock, R. Scott (Randall Scott)
The Lone Jack group of claims is in the Mt. Baker Mining District, northern Whatcom County, Washington. Three prominent gold-quartz veins are present, two of which were mined and produced 945 kg of gold between 1901 and 1924. Since then mining operations have not been renewed.
The quartz veins are within 3 km of surface exposures of the Miocene Chilliwack Batholith, above and within a zone of deformation related to the mid-Late Cretaceous Shuksan fault. This major Northern Cascades structure has juxtaposed the Upper Mesozoic Carrington Phyl lite over the Paleozoic volcanic and sedimentary rocks of the Chilliwack Group. The quartz veins are genetically related to local Tertiary block faulting which postdated the metamorphism and deformation related to the Shuksan fault. The style of deformation and timing of these Tertiary faults suggests that they are related to the emplacement of the nearby batholith. The quartz veins were emplaced during, perhaps in the waning stages of, this intrusive activity.
Two generations of mineralization are present; each has a similar paragenesis. Vein minerals other than quartz include pyrrhotite, pyrite, chalcopyrite, tellurbismuth, and free gold. Gold was deposited in equilibrium with pyrrhotite, sericite, and graphite.
Fluid inclusion analyses were used to determine that the ore-forming solutions were boiling, dilute, and contained an average of 0.25 mol% CO2. Crystallization occurred at about 285oC and 625 bars of lithostatic pressure. Thermodynamic calculations indicate that the gold may have been transported as the Au(HS)ˉ2 complex, and that precipitation of the gold resulted from the physiochemical changes caused by boiling.
Prospecting for similar deposits in the area should be directed toward locating post-metamorphic quartz veins near the Shuksan fault and the Chilliwack Batholith, which show evidence of boiling.
Gold mineralization, Miocene Chilliwack Batholith
Western Washington University
Subjects – Names (LCNAF)
Lone Jack Gold Mine (Whatcom County, Wash.)
Whatcom County (Wash.)
Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Christenson, Lief G., "Genesis of Gold Mineralization in the Lone Jack Mine Area, Mt. Baker Mining District, Washington" (1986). WWU Graduate School Collection. 774.