scholarly journals A U - Pb Zircon Age For Host Rocks of a Syngenetic Strontium [-Zinc] Occurrence in the Kitsault Lake area, West - Central British Columbia

1992 ◽  
Author(s):  
J K Mortensen ◽  
R V Kirkham
Keyword(s):  
British Columbia ◽  
Lake Area ◽  
Zircon Age ◽  
West Central ◽  
Host Rocks

Tip Top Hill volcanics: Late Cretaceous Kasalka Group rocks hosting Eocene epithermal base- and precious-metal veins at Owen Lake, west-central British Columbia

1992 ◽  
Vol 29 (5) ◽  
pp. 854-864 ◽  
Author(s):  
Craig H. B. Leitch ◽  
C. T. Hood ◽  
Xiao-Lin Cheng ◽  
A. J. Sinclair
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Lake Area ◽  
Vein Deposit ◽  
Type Area ◽  
Lake Formation ◽  
Host Rocks ◽  
Polymictic Conglomerate

Rocks hosting the Silver Queen epithermal Au–Ag–Zn–Pb–Cu vein deposit near Owen Lake, British Columbia, belong to the Tip Top Hill volcanics. They are lithologically similar to the informally named Upper Cretaceous Kasalka Group rocks exposed in the type area at Tahtsa Lake, 75 km southwest of the deposit, and at Mount Cronin, 100 km northwest of the deposit. The Kasalka Group rocks in the Tahtsa Lake area give questionable dates of 105 ± 5 Ma by K–Ar on whole rock but are cut by intrusions dated at 83.8 ± 2.8 Ma by K–Ar on biotite. The sequence at the Silver Queen deposit includes a polymictic conglomerate, followed upward by felsic fragmental rocks and a thick porphyritic andesite flow and sill unit, cut by microdiorite and quartz–feldspar porphyry intrusions. The porphyritic andesite and the microdiorite have been dated as Late Cretaceous (78.3 ± 2.7 and 78.7 ± 2.7 Ma, respectively, by K–Ar on whole rock), close to previous dates for these rocks (77.1 ± 2.7 and 75.3 ± 2.0 Ma, respectively). The quartz–feldspar porphyry intrudes the porphyritic andesites but has an older U–Pb zircon date of 84.6 ± 0.2 Ma, probably due to underestimation of the true age of the host rocks by the K–Ar whole-rock method. Later dykes correlate with younger volcanic rocks belonging to the Ootsa Lake and Endako groups. Eocene pre- and postmineral plagioclase-rich dykes (51.9 ± 1.8 to 51.3 ± 1.8 Ma) and late diabase dykes (50.4 ± 1.8 Ma; all by K–Ar on whole rock) may be correlative with trachyandesite volcanics of the Goosly Lake Formation, part of the Eocene Endako Group. These volcanics have been dated elsewhere at 55.6 ± 2.5 to 48.8 ± 1.8 Ma by K–Ar on whole rock and biotite, respectively. Mineralization at Silver Queen is therefore similar in age to, but slightly younger than, the producing Equity mine located 30 km to the northeast, which is estimated at 58.5 ± 2.0 Ma by K–Ar on whole rock.

Carbonate-hosted lead–zinc occurrences in northeastern British Columbia with emphasis on the Robb Lake deposit

1978 ◽  
Vol 15 (11) ◽  
pp. 1737-1762 ◽  
Author(s):  
R. W. Macqueen ◽  
R. I. Thompson
Keyword(s):  
British Columbia ◽  
Hydrogen Sulphide ◽  
Middle Devonian ◽  
Mineral Deposits ◽  
Burial Depth ◽  
Sulphide Mineral ◽  
Lake Area ◽  
Sulphur Isotope ◽  
Platform Margin ◽  
Host Rocks

In the Rocky Mountains of northeastern British Columbia, a Lower and Middle Devonian platform carbonate succession of six formations and [Formula: see text] total thickness gives way laterally north and west to shales, siltstones, and carbonaceous limestones of the Besa River Formation, of deeper water origin. Promising mineralization, dominantly sphalerite with some galena, is located in carbonates near the platform margin, within the Muncho–McConnell–Stone, Pine Point – Sulphur Point, and Slave Point Formations. Mineralization is not obviously related to structure, unconformities, or evaporite solution. Sphalerite and galena are closely associated with white sparry dolomite and commonly accompanied by quartz and thermally altered reservoir bitumen. Sulphur isotope ratios of galena and sphalerite range from + 5.0 to + 17.5 δ34S‰, consistent with a reduced sulphate or petroleum-derived hydrogen sulphide source for sulphur.At Robb Lake, mineralization occurs within broadly conformable breccias in the Stone, Muncho–McConnell interval; sparry dolomite forms the breccia matrix; and bitumen is common although rare elsewhere in the interval. Maximum paleotemperatures of host carbonates at Robb Lake appear to have been about 200–230 °C, as determined by bitumen characteristics, fluid inclusion filling temperatures in quartz, and illite crystallinity from illite in Besa River Formation shales. The Paleozoic and Mesozoic sedimentary section in the region suggests that the Middle Devonian of the Robb Lake area reached a maximum burial depth of about 5 km during mid-Cretaceous time. Physical proximity of bitumen and sulphide mineral deposits suggests that similar processes were involved in petroleum maturation–migration, and metallic mineral precipitation. Besa River shales are seen as probable sources for both petroleum and metals; sulphide sources appear to have been hydrogen sulphide generated within carbonate host rocks. A genetic association of petroleum and metals implies that mineralization took place relatively late (?early Mesozoic), and under deep subsurface conditions.Ground preparation in the form of brecciation and fracturing is problematical; at Robb Lake it may be a consequence of hydraulic fracturing due to high pore pressures generated by dewatering of the fine clastic facies that envelope the host dolomites. A better knowledge of time of origin of these deposits will contribute greatly to an understanding of their genesis. Meanwhile, consideration of the burial and thermal history of the host rocks offers a useful framework within which the mineral deposits and their genesis may be assessed.

Identification and significance of late Holocene tephra from Otter Creek, southern British Columbia, and localities in west-central Alberta

1977 ◽  
Vol 14 (11) ◽  
pp. 2593-2600 ◽  
Author(s):  
J. A. Westgate
Keyword(s):  
British Columbia ◽  
Late Holocene ◽  
Far North ◽  
West Central ◽  
Tephra Beds ◽  
Middle Unit ◽  
Mount St Helens

Three thin, light-coloured, ash-grade tephra beds occur within the uppermost metre of peat at Otter Creek bog in southern British Columbia. The youngest tephra is related to the ~2600 year old Bridge River tephra but is probably the product of a younger and weaker eruption that directed tephra to the southeast of the vent, believed to be located in the Meager Mountain district of southwestern British Columbia. The middle unit is ~2100 years old and is tentatively correlated with one of the upper beds of set P tephra of Mount St. Helens in Washington. The lowermost tephra is equivalent to the Yn bed of set Y, derived from an eruption of Mount St. Helens about 3400 years ago.The Yn tephra has been located as far north as Entwistle in west-central Alberta but mineralogically and chemically similar tephra elsewhere in this region is ~4300 years old and thus represents an older part of the Y set. Significant compositional differences between these two extensive members of the Y set have not yet been recognized.

Rare earth element concentrations in Quaternary volcanic rocks of southwestern British Columbia

1984 ◽  
Vol 21 (6) ◽  
pp. 731-736 ◽  
Author(s):  
Nathan L. Green ◽  
Paul Henderson
Keyword(s):  
British Columbia ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Lake Area ◽  
Calc Alkaline ◽  
Lower Light ◽  
The Individual ◽  
High Level ◽  
Ree Patterns

A suite of hy-normative hawaiites, ne-normative mugearite, and calc-alkaline andesitic rocks from the Garibaldi Lake area exhibits fractionated, slightly concave-upward REE patterns (CeN/YbN = 4.5–15), heavy REE contents about 5–10 times the chondritic abundances, and no Eu anomalies. It is unlikely that the REE patterns provide information concerning partial melting conditions beneath southwestern British Columbia because they have probably been modified substantially by upper crustal processes including crustal contamination and (or) crystal fractionation. The REE contents of the Garibaldi Lake lavas are not incompatible with previous interpretations that (1) the hawaiites have undergone considerable fractionation of olivine, plagioclase, and clinopyroxene; and (2) the individual andesitic suites were derived from separate batches of chemically distinct magma that evolved along different high-level crystallization trends. In general, however, the andesites are characterized by lower light REE contents than the basaltic andesites. These differences in LREE abundances may reflect different amounts of LREE-rich accessory phases, such as apatite, sphene, or allanite, assimilated from the underlying quartz diorites.

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