The conglomerate of Churn Creek: Late Cretaceous basin evolution along the Insular–Intermontane superterrane boundary, southern British Columbia

2001 ◽  
Vol 38 (1) ◽  
pp. 59-73
Author(s):  
J W Riesterer ◽  
J Brian Mahoney ◽  
Paul Karl Link
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Clastic Rocks ◽  
South Central ◽  
Lower Member ◽  
Volcanic Source ◽  
Braided Stream ◽  
Bridge Group

Upper Cretaceous coarse clastic rocks exposed in the canyon of Churn Creek, south-central British Columbia, record active basin tectonism and coeval volcanism adjacent to the boundary between the Intermontane and Insular superterranes. Mid to late Albian (~104 Ma U–Pb), calc-alkaline andesite and basaltic andesite flows, with minor conglomerate and reworked epiclastic deposits and tuffs correlative with the Spences Bridge Group of the Intermontane superterrane are exposed in the canyon. In depositional contact above the volcanic rocks is the conglomerate of Churn Creek, which contains a thick (>1 km) sequence of complexly intertonguing conglomerate and sandstone that is divided into two members composed of four lithofacies. The lower member was deposited unconformably on the underlying Albian volcanic unit and contains late Albian–Cenomanian chert-pebble (>50% chert) conglomerate and interbedded chert- and volcanic-lithic sandstone. It is interpreted to have been deposited in a braided stream system flowing from southeast to northwest. The source for the chert was most likely the Bridge River terrane, a Mississippian to Jurassic ocean floor assemblage located to the southwest of Churn Creek, south of the Yalakom fault. Gradationally overlying the lower member throughout much of the basin is a mixed chert, plutonic, and volcaniclastic lithofacies of the upper member. Plutonic debris was provided to the mixed and plutonic lithofacies of the upper member by the Little Basin pluton, which was uplifted along the northeast-directed Little Basin thrust fault on the southwest margin of the basin. The upper member also contains a volcanic-rich lithofacies composed of chaotic volcanic conglomerate and local lithic tuff derived from a coeval proximal volcanic source. The conglomerate of Churn Creek records active northeast-vergent compressional tectonism and development of piggyback basins along the boundary between the Insular and Intermontane superterranes during Albian–Santonian time. The conglomerate of Churn Creek has been correlated to the Silverquick – Powell Creek succession of the Methow terrane, based on age, stratigraphic, lithologic, structural, geochemical, and paleomagnetic similarities, and may, therefore, represent an overlap assemblage linking the superterranes in the Late Cretaceous.

Revised stratigraphic nomenclature and age determinations for mid-Cretaceous volcanic rocks in southwestern British Columbia

1989 ◽  
Vol 26 (10) ◽  
pp. 2016-2031 ◽  
Author(s):  
Derek J. Thorkelson ◽  
Glenn E. Rouse
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Fault System ◽  
Volcanic Stratigraphy ◽  
Clastic Rocks ◽  
Lower Unit ◽  
Basement Rocks ◽  
Lithostratigraphic Units ◽  
Bridge Group ◽  
Stratigraphic Nomenclature

Mid-Cretaceous volcanic and volcaniclastic rocks in southwestern British Columbia, east of the Fraser Fault System, constitute two principal lithostratigraphic units. The lower unit, a composite succession of basaltic to rhyolitic lavas and various clastic rocks, is exposed in a 215 km linear belt from near Pavilion to south of Princeton. The upper unit, mostly amygdaloidal andesite, is restricted to the centre of the belt between Spences Bridge and Kingsvale, where it overlies the lower unit and contiguous basement rocks. Both units were deposited subaerially, concurrent with folding and faulting, and share a contact that varies from gradational, near Kingsvale, to unconformable, near Spences Bridge.The names "Spences Bridge Group" and "Kingsvale Group" were used by several authors for various parts of the volcanic stratigraphy. We suggest revision of nomenclature whereby the lower and upper units are named "Pimainus Formation" and "Spius Formation", respectively; together they constitute the Spences Bridge Group. The term "Kingsvale Group" is abandoned.Assemblages of fossil leaves and palynomorphs, collected from one Spius and seven Pimainus localities, include several species of early angiosperms. A late Albian age is thereby indicated for both formations; this is largely corroborated by isotopic dates from the volcanic strata and cross-cutting granitic plutons.

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.

scholarly journals Stratigraphic affinity of Upper Cretaceous volcanic rocks in the Churn Creek-Gang Ranch area, south-central British Columbia

1999 ◽  
Author(s):  
M L Haskin ◽  
J B Mahoney ◽  
R J Enkin ◽  
P S Mustard ◽  
C J Hickson
Keyword(s):  
British Columbia ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
South Central

scholarly journals Geochemistry, geochronology, and fluid inclusion study of the Late Cretaceous Newton epithermal gold deposit, British Columbia

2016 ◽  
Vol 53 (1) ◽  
pp. 10-33 ◽  
Author(s):  
Lijuan Liu ◽  
Jeremy P. Richards ◽  
S. Andrew DuFrane ◽  
Mark Rebagliati
Keyword(s):  
British Columbia ◽  
Gold Deposit ◽  
Late Cretaceous ◽  
Gold Mineralization ◽  
Volcanic Rocks ◽  
Fluid Inclusion Study ◽  
Epithermal Gold ◽  
Epithermal Gold Deposit ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Newton is an intermediate-sulfidation epithermal gold deposit related to Late Cretaceous continental-arc magmatism in south-central British Columbia. Disseminated gold mineralization occurs in quartz–sericite-altered Late Cretaceous felsic volcanic rocks, and feldspar–quartz–hornblende porphyry and quartz–feldspar porphyry intrusions. The mineralization can be divided into three stages: (1) disseminated pyrite with microscopic gold inclusions, and sparse quartz–pyrite ± molybdenite veins; (2) disseminated marcasite with microscopic gold inclusions and minor base-metal sulfides; and (3) polymetallic veins of pyrite–chalcopyrite–sphalerite–arsenopyrite. Re–Os dating of molybdenite from a stage 1 vein yielded an age of 72.1 ± 0.3 Ma (published by McClenaghan in 2013). The age of the host rocks has been constrained by U–Pb dating of zircon: Late Cretaceous felsic volcanic rocks, 72.1 ± 0.6 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013); feldspar–quartz–hornblende porphyry, 72.1 ± 0.5 Ma; quartz–feldspar porphyry, 70.9 ± 0.5 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013). The mineralized rocks are intruded by a barren diorite, with an age of 69.3 ± 0.4 Ma. Fluid inclusions in quartz–pyrite ± molybdenite ± gold veins yielded an average homogenization temperature of 313 ± 51 °C (number of samples, n = 82) and salinity of 4.8 ± 0.9 wt.% NaCl equiv. (n = 46), suggesting that a relatively hot and saline fluid likely of magmatic origin was responsible for the first stage of mineralization. Some evidence for boiling was also observed in the veins. However, the bulk of the gold mineralization occurs as disseminations in the wall rocks, suggesting that wall-rock reactions were the main control on ore deposition.

Petrology and geochemistry of the Kamloops Group volcanics, British Columbia

1981 ◽  
Vol 18 (9) ◽  
pp. 1478-1491 ◽  
Author(s):  
Thomas E. Ewing
Keyword(s):  
British Columbia ◽  
Fractional Crystallization ◽  
Middle Eocene ◽  
Volcanic Rocks ◽  
Primary Source ◽  
Low Pressure ◽  
Rock Types ◽  
South Central ◽  
High K ◽  
Petrology And Geochemistry

The Kamloops Group is an alkali-rich calc-alkaline volcanic suite of Early to Middle Eocene age, widespread in south-central British Columbia. Rock types in the suite range from high-K basalt through andesite to rhyolite. The suite is characterized by relatively high K2O, Sr, and Ba, but low Zr, Ti, and Ni concentrations, only moderate Ce enrichment, and little or no Fe enrichment. Initial ratios 87Sr/86Sr are about 0.7040 in the western half, and about 0.7060 in the eastern half of the study area. No difference in chemistry or mineralogy marks this sharp transition. Chemically similar suites include the Absaroka–Gallatin suite in Wyoming and the lower San Juan (Summer Coon) suite in Colorado. The content of K2O at 60% SiO2 increases regularly eastward across southern British Columbia. The chemical data support the subduction-related continental arc origin of the Kamloops Group volcanics.The volcanic rocks consist in the main of augite–pigeonite andesites ranging from 52 to 62% silica, with subordinate quantities of olivine–augite–pigeonite basalt and biotite rhyodacite and rhyolite. The andesites and basalts were derived by a combination of low-pressure fractional crystallization, higher pressure fractional crystallization, and variable parental magmas, whereas low-pressure fractional crystallization of plagioclase, biotite, and apatite from parental basalt and andesite produced the rhyolites. The parental magmas were basalts and basaltic andesites with high K, Sr, and Ba. The primary source of these magmas is inferred to have been an alkali-enriched hydrous peridotite with neither plagioclase nor garnet present in the residuum.

Mineralogy and origin of the upper Eastend and Whitemud Formations of south-central and southwestern Saskatchewan and southeastern Alberta

1969 ◽  
Vol 6 (2) ◽  
pp. 317-334 ◽  
Author(s):  
P. N. Byers
Keyword(s):  
Chemical Weathering ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Source Area ◽  
Heavy Minerals ◽  
Major Constituent ◽  
Abrupt Decrease ◽  
South Central ◽  
Mechanical Weathering ◽  
Kaolinitic Clay

The Upper Cretaceous non-marine Whitemud Formation of south-central and southwestern Saskatchewan and southeastern Alberta consists of kaolinitic, metamorphic lithic sands and silts, and kaolinitic clays. The sands and silts are not highly feldspathic as was originally thought. The major constituent is metamorphic lithic grains with minor kaolinitic clay and vermicular kaolin, clear angular quartz, chert, muscovite, and minor volcanic lithic grains and feldspar. The upper part of the Upper Cretaceous Eastend Formation, which conformably underlies the Whitemud Formation, consists of non-marine sands, silts, and clays. Kaolin is very rare. The bulk of the sands are composed of volcanic lithic grains with minor metamorphic lithic grains, clear angular quartz, chert, feldspar, muscovite, and biotite.The contact is characterized by the following changes from the Eastend Formation upward into the Whitemud Formation: an abrupt decrease in volcanic lithic grains and increase in metamorphic lithic grains; the appearance of kaolin and the disappearance of biotite and apatite; a slight increase in clear angular quartz and muscovite and a decrease in feldspar; a general increase in metamorphic heavy minerals; and an increase in the percentage of ilmenite (both as solitary grains and intergrown with magnetite), which is altered to leucoxene.On the basis of mineralogy, the Whitemud Formation is definitely a correlative of the Colgate Member of the Fox Hills Formation in Montana and North Dakota.The upper Eastend and Whitemud Formations were derived from Upper Cretaceous volcanic rocks, Precambrian and Paleozoic metamorphic rocks, and Paleozoic carbonates all situated in Montana. Upper Eastend sediments represent fast mechanical weathering of mountains of freshly extruded volcanic rocks, whereas the Whitemud sediments represent slow chemical weathering and leaching, which predominated once the mountainous volcanic rocks were worn down. This deep chemical weathering altered the volcanic tuffs and flows into kaolinitic clay at the source area; the kaolin of the Whitemud Formation is not derived from the weathering of feldspars at the site of deposition.It is suggested that the Frenchman and Ravenscrag Formations were also derived from Upper Cretaceous and Lower Tertiary volcanic rocks in Montana.

Sign in / Sign up

Export Citation Format

Share Document