Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario

Details Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario

Aug 1967

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1967natur.215..725c&link_type=abstract

Nature, Volume 215, Issue 5102, pp. 725-726 (1967).

Computer Science

3

Scientific paper

THE Brent crater (46° 04' N., 78° 29' W.) is cut into the Pre-Cambrian gneisses of central Ontario. On the surface the crater is marked by a poorly defined depression 18,000 ft. in diameter, with a sharply denned central crater 11,000 ft. in diameter and about 200 ft. deep. Drilling1 has shown that the central crater is partly filled with flat lying Ordovician strata underlain by a thick lens of brecciated Pre-Cambrian material. A hole drilled approximately in the centre of the structure1,2 passed through about 800 ft. of Ordovician strata, 1,900 ft. of breccia of various kinds, and beginning at a depth of 2,716 ft. penetrated breccia with a matrix of igneous textured trachyte for more than 100 ft. Below this ``melt zone'' brecciation died out very rapidly. Because of petrographic features found in the breccias, Brent has been widely accepted as a holotype of a ``fossil'' meteorite crater1-4. The Brent crater occurs on or near the Ottawa-Bonnechere graben, however, a major structure with a length of some hundreds of miles5, along which circular alkaline and carbonatitic complexes were intruded in Cambro-Ordovician time6,7. These facts suggest a possible endogenetic origin for the crater. In an attempt to resolve this problem we examined the petrographic and chemical composition of twenty-three samples of drill core from the central hole and nine samples collected on the surface. It was found petrographically that the samples fell into four groups. Underlying the Ordovician were about 100 ft. of breccias with substantial amounts of glass (often of several types), below which were 1,700 ft. of breccias with little or no glass. At a depth of 2,700 ft., 16 ft. of breccia rich in glass was again encountered grading into inclusion rich trachyte of igneous aspect. About 50 ft. of breccia rich in glass occurred below the trachyte, passing abruptly into relatively undeformed country rocks. A specimen from one of the dykelets cutting the breccia poor in glass was composed of extremely fine grained carbonates, minute needles of a pleochroic blue mineral and abundant opaque dust.

Affiliated with

Also associated with

No associations

Rating

Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1416143