Kimberlites of Camsell Lake field and some features of construction, and composition of lithosphere roots of southeastern part of Slave Craton, Canada

Since the discovery of the first kimberlite pipe CL-25 within a new kimberlite field situated east of Camsell Lake in 1994 (Pokhilenko et al., 1995(Pokhilenko et al., , 1997)), Winspear Resources Ltd. has recognized a number of new bodies: the CL-174 Pipe few hundreds of meters apart from the CL-25 Pipe, a system of dikes, and a blind body filled with a breccia of complex composition near Snap Lake about 20 km west of the CL-25 and CL-174 pipes.Petrographic and petrochemical characteristics of the CL-25 and CL-174 kimberlites are very close; the distribution patterns of compositions of garnets, magnesian ilmenites, and Cr-spinellide from both pipes are also quite identical.All the characteristics of kimberlites and their mantle-derived minerals reported for the CL-25 Pipe (Pokhilenko et al., 1995(Pokhilenko et al., , 1997) may be valid for the CL-174 Pipe as well.It is made up of typical kimberlite breccia with a high content of xenogenous material represented chiefly by the host granitoids and metamorphic rocks.Petrochemical and petrographical characteristics of the kimberlites from the CL-174 Pipe also permit them to be classified as group I (Skinner, Clement, 1979).Like the CL-25 Pipe, this pipe is poor in diamonds.The kimberlite rocks found in a system of dikes and in boulder trains near Snap Lake drastically differ from the kimberlites from the CL-25 and CL-174 pipes in petrography, petrochemistry, mineralogy, and in being incomparably richer in diamonds.The kimberlites from the Snap Lake region are established in a series of dikes up to 4 m thick, drilled on the western shore of the lake, in its southern part.Also, they are found in a blind body, resembling a thick (about 100 m) sill, drilled at a depth of 100 m; this body is made up of compositionally complex breccia with an upward variable amount of kimberlite material, reaching the maximum in the lower part of the body.A great deal of kimberlite fragments (hundreds of kilograms) have been established in a boulder train, extended from Snap Lake through a peninsula in the southern part of the lake.The dikes of the western shore are made up of kimberlite rocks with the massive texture of the groundmass and virtually contain no host rock xenoliths; the mantle rock xenoliths are very rare and are represented chiefly by serpentinized granular peridotites.Grains of pyropes, mainly of purple color and up to 3 mm in size, are very scarce.Grains of octahedral chromites up to 1.5 mm in size are also rare.Ilmenites in the rock are not found at all.It was established that the crushed and panned specimen, composed of several ten small fragments of 1.1 kg in total weight, contained 11 grains of pyrope, 16 grains of chromite, and 4 grains of diamond, the largest of which was about 2 mm in size.In composition these rocks belong to the most magnesian varieties of kimberlites and have analogs among the Siberian diamond-rich kimberlites: 31.6 -32.4 wt.% Si02, 0.73 -0.83 wt.% Ti02, 3.18 -3.93 wt.% A1203, 8.61 -9.38 wt.% Fe203, 0.18 -0.23 wt.% MnO, 32.5 -33.7 wt.% MgO, 1.64 -5.39 wt.% CaO, 0.01 -0.15 wt.% Na20, 0.36 -0.58 wt.% K20, 0.50 -0.82 wt.% P205; LOI= 13.2-15.9wt.%.The pyropes from kimberlites have an unusually wide range of variations in Cr203 contents, up to 17 wt.%,and this distinguishes them from the pyropes from the South-African and Siberian pipes,

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.