INTRUSIVE ROCKS OF THE GAME LAKE AREA AND IMPLICATIONS FOR THE ORIGIN OF THE SNOWCAMP OPHIOLITE

The geology of the Cartwright Lake area consists of a >2 km thick conformable sequence of Early Proterozoic supracrustal rocks intruded by calc-alkaline granitoid plutons. The supracrustal succession comprises a basal series of tholeiitic basalts, an overlying bimodal sequence, and an uppermost series of calc-alkaline andesites. The bimodal sequence incorporates abundant tholeiitic basalts and associated mafic tuffs, lesser felsic hyaloclastites and pyroclastics, and minor interflow greywacke–mudstone turbidites.Petrogenetic models involving trace-element concentrations indicate that most of the extrusive and intrusive rocks were derived from similar parent magmas that formed by extensive partial melting of a garnet lherzolite upper-mantle source. The parent liquids fractionated along an early tholeiitic trend and a later calc-alkaline trend, producing the observed geochemical variations in the mafic and intermediate volcanic assemblages. Ponding of mafic magma at the base of the crust may have promoted crustal fusion, thereby generating felsic liquids, which erupted and formed the dacite–rhyolite suite.The geology and geochemistry of the volcanic assemblages are consistent with a subduction-related origin in a volcanic-arc setting. The majority of geochemical evidence favours the interpretation that the Cartwright Lake segment of the arc developed on relatively thin sialic crust.

Download Full-text

Provenance of igneous clasts in conglomerates of the Archaean Timiskaming Group, Kirkland Lake area, Abitibi greenstone belt, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e94-156 ◽

1994 ◽

Vol 31 (12) ◽

pp. 1749-1762 ◽

Cited By ~ 5

Author(s):

Marc I. Legault ◽

Keiko Hattori

Keyword(s):

Greenstone Belt ◽

Volcanic Rocks ◽

Hydrothermal Activity ◽

Tholeiitic Basalt ◽

Coarse Grained ◽

Alkaline Magmatism ◽

Lake Area ◽

Calc Alkaline ◽

Intrusive Rocks ◽

Strike Slip Movement

Four types of igneous clasts from Timiskaming conglomerates of the Kirkland Lake area are identified: calc-alkaline porphyry, trachyte (K2O + N2O > 7.25 wt.%), trondhjemite, and tholeiitic basalt. Clasts derived from quartz–carbonate veins and carbonatized porphyries and komatiites indicate CO2-rich hydrothermal activity along the Larder Lake – Cadillac Fault before sedimentation. Calc-alkaline porphyry, the predominant clast, is similar in appearance to feldspar porphyry intrusions widely exposed in the area, but the two are not related. The porphyry clasts are cogenetic with diorite–granodiorite intrusions and volcanic rocks of the greenstone belt. Andesite clasts are only observed near the base of the assemblage, and the ratio of basalt to andesite increases up stratigraphic sections. The change suggests progressive erosion of arc-related volcanic rocks during sedimentation. Composition, texture, and mineralogy of the trondhjemite clasts are consistent with their derivation from the marginal phases of the Round Lake batholith. Intrusive rocks of the Timiskaming Group (coarse-grained holocrystalline syenitic–monzonitic rocks, biotite-bearing feldspar porphyries, and mica-rich lamprophyres) were not observed in the clasts, which suggests sedimentation prior to unroofing of these rocks. Sedimentation of the conglomerates postdated unroofing of underlying plagioclase porphyry (~2685 Ma), but predated unroofing of Timiskaming intrusions. The distribution of alkaline clasts only in proximity to the fault implies that alkaline magmatism was confined along the fault. Derivation of clasts from both sides of the fault and proximity of inferred sources support a pull-apart basin for sedimentation with minor strike-slip movement during and after the sedimentation.

Download Full-text

Characterization of Mafic - Ultramafic Intrusive Rocks in the Flin Flon - Snow Lake area, Manitoba

10.4095/127282 ◽

1989 ◽

Cited By ~ 1

Author(s):

L D Ayers ◽

J Young

Keyword(s):

Lake Area ◽

Intrusive Rocks ◽

Flin Flon

Download Full-text

POTASSIUM–ARGON DATES OF BASIC INTRUSIVE ROCKS OF THE DISTRICT OF MACKENZIE, N.W.T.

Canadian Journal of Earth Sciences ◽

10.1139/e66-029 ◽

1966 ◽

Vol 3 (3) ◽

pp. 389-412 ◽

Cited By ~ 17

Author(s):

Alice Payne Leech

Keyword(s):

World Wide ◽

Precise Determination ◽

Radiometric Dating ◽

Lake Area ◽

Tholeiitic Magma ◽

Slave Province ◽

Best Value ◽

The World ◽

Intrusive Rocks

Samples were taken from diabase dykes and related contact rocks and from a differentiated intrusive body of the District of Mackenzie in the Yellowknife–Prosperous Lake area, the Lac de Gras area, the Point Lake area, and the Tree River – Coronation Gulf area. In addition, several samples were taken from basic intrusions of Ontario, and some of the results obtained from these are included.Radiometric dating by the potassium–argon method indicated at least four periods of diabase dyke intrusion in the Slave Province of the Precambrian shield about 2 200–2 400 m.y. ago, 1 900–2 100 m.y. ago, 1 100–1 200 m.y. ago, and 600–700 m.y. ago. Scatter in the radiometric dates prevents recognition of other possible events by use of the whole-rock method, where the age of intrusion is older than Middle Proterozoic.Chemical and petrologic studies were carried out in conjunction with the radiometric dating. Precise determination of potassium proved difficult; in most cases, a best value for each sample was selected from the results of three independent determinations. There is some suggestion of an increase in the potassium content of diabase dykes in the Canadian shield throughout Precambrian time. Alkali–silica ratios show that all of the diabase dykes studied belong to the world-wide tholeiitic magma type.

Download Full-text

GEOCHRONOLOGY OF THE CANADIAN SHIELD IN NORTHEASTERN ALBERTA: I. ANDREW LAKE AREA

Canadian Journal of Earth Sciences ◽

10.1139/e67-029 ◽

1967 ◽

Vol 4 (3) ◽

pp. 541-563 ◽

Cited By ~ 11

Author(s):

H. Baadsgaard ◽

John D. Godfrey

Keyword(s):

Field Work ◽

Lake Area ◽

Geologic History ◽

Apparent Absence ◽

Petrographic Examination ◽

Intrusive Rocks ◽

History Of ◽

Basement Gneiss ◽

Northeastern Alberta ◽

Representative Samples

Field work and petrographic investigation in the Precambrian of northeastern Alberta near Andrew Lake indicate a complex geologic history involving at least three major diastrophic periods. U–Pb, Rb–Sr, K–Ar, and several model lead dates determined on amenable phases of representative samples of the major rock units may be placed in three groups, roughly corresponding to the major diastrophic periods. All mica K–Ar dates are close to ~1 800 m.y., while the zircon, uraninite, and allanite U–Pb dates fall into two groups at ~1 900 m.y. and ~2 250 m.y, A whole-rock Rb–Sr isochron plot of selected basement gneiss samples also yields two groups of dates at ~1 900 m.y. and ~2 250 m.y. When the geologic history of seven selected representative rock samples is judged by petrographic examination of the dated minerals, the petrographically estimated response of the minerals to sequential geologic events is reflected with good correlation by the various dates determined on the minerals. Some discrepancies in this latter correlation are noted and include such things as a relatively 'old' zircon in a young intrusive plug, the apparent absence of primary intrusive rocks at the time of the oldest (zircon dates) and the youngest (K–Ar mica dates) diastrophic periods.

Download Full-text